The object of study of virology is. Research work "virology in the future". The flu is not as bad as complications after it, one woman says to another

"Starfall" Astafiev

In the middle of the 20th century, the desire for a truthful recreation of life was gaining strength in Soviet literature, writers were paying more and more attention to the problems of humanism and morality. But this does not mean at all that the authors only scrupulously reflected life in all its manifestations, on the contrary, it is for this period that the flourishing of lyrical prose is characteristic. We can recall a number of wonderful works by front-line writers, imbued with a special lyrical intonation: “Battalions ask for fire” (1957), “Last volleys” (1959) by Y. Bondarev, “Nine days (South of the main attack)” ( 1958), "Span of the Earth" (1959) by G. Baklanov, "The Third Rocket" (1962), "Front Page" (1963) by V. Bykov and others.

What do all these works have in common? In my opinion, novels and short stories of writers - representatives of youth prose - are related by the fact that the main characters were the embodiment of the author's experience, often the image of the author was clearly visible through the image of the character. The war in the description of representatives of youth prose is described without the slightest embellishment, with many cruel details. But, perhaps, due to the youth of the authors, military pictures are still fanned by some kind of romance.

In my work, I would like to dwell on the analysis of Viktor Petrovich Astafiev's story "Starfall", written by him in 1960. This small work seems to be very capacious, it shows the reader an entire era in the life of a nineteen-year-old boy. Those few months that he spent in the Krasnodar hospital were imprinted in his soul and memory for life.

There is not a single description of military operations in the story. Written fifteen years after the war, the work, in my opinion, is a summary of the author's reflections on those events. Astafiev here refrains from stories about battles, heroic deeds, great disasters of the people. The story seems to be completely everyday. We read about the life of the inhabitants of the hospital, far from comfort, but still not without pleasant moments, about how they try to “snatch”, “grab” all the possible advantages of being in the hospital. However, the author does not allow us to doubt for a second the readiness of these soldiers to take up arms as soon as it becomes possible for them.

There is a lot of autobiography in this story. The main character of Starfall, Mikhail, is also a Siberian, he was brought up in an orphanage, studied to be a train compiler, like Viktor Petrovich Astafyev himself. Reading this work, you are involuntarily imbued with "the conviction that this romantic story also happened to the author of the story himself.

Starfall is a work imbued with deep lyricism. The theme of love begins to sound to hold from the very first lines. As soon as the young man opens his eyes, having come to his senses after a serious operation, a young nurse appears in his eyes, with whom the soldier falls in love at first sight. The author is far from romanticism. Somewhere between the lines we can understand that this love is not at all something unique, unearthly. Nineteen-year-old orphanage resident Mikhail had never met a girl until then. Having been on the verge of life and death, Misha subconsciously comes to the need to meet his love. And the first girl he saw - a pretty charming nurse Lidochka immediately wins his heart.

Of course, there are many tragic moments in the story: people die, and those who shared the hospital ward with them yesterday do not immediately come to terms with the loss. Astafiev also describes the devastated city, with destroyed houses and ruined streets, a people living in constant need. But still, in general, "Starfall", in my opinion, is one of the most optimistic works of Astafiev. There are so many heroes in the story that never lose heart, such solidarity between them is felt that one involuntarily imbues with confidence that such a people, such people could not but emerge victorious from a terrible bloody war. This is largely due to the fact that we see the city of the war years, a hospital full of wounded, through the eyes of a very young man. Youthful love of life, the desire to know life can overcome the pain and horror of war. And we see this not only in the young soldier, but also in the girl who loved him so deeply and selflessly. The final pages of the story are full of nagging pain. And the reader sympathizes with the girl left in the rear almost more than with the soldier leaving for the front. The scene of Mikhail's farewell to Lida is deeply touching. Lines from a poem by Vladimir Vysotsky come to mind:

So it happened - the men left,

Abandoned crops ahead of time, -

Introduction

General virology studies the nature of viruses, their structure, reproduction, biochemistry, and genetics. Medical, veterinary and agricultural virology investigates pathogenic viruses, their infectious properties, develops measures for the prevention, diagnosis and treatment of diseases caused by them.

Virology solves fundamental and applied problems and is closely related to other sciences. The discovery and study of viruses, in particular bacteriophages, has made a huge contribution to the formation and development of molecular biology. The branch of virology that studies the hereditary properties of viruses is closely related to molecular genetics. Viruses are not only a subject of study, but also a tool for molecular genetic research, which links virology with genetic engineering. Viruses are the causative agents of a large number of infectious diseases in humans, animals, plants, and insects. From this point of view, virology is closely related to medicine, veterinary medicine, phytopathology and other sciences.

Having emerged at the end of the 19th century as a branch of human and animal pathology, on the one hand, and phytopathology, on the other, virology has become an independent science, rightfully occupying one of the main places among the biological sciences.

Chapter 1. History of Virology

1.1. Discovery of viruses

Virology is a young science with a history of just over 100 years. Having begun its journey as a science of viruses that cause diseases in humans, animals and plants, virology is currently developing in the direction of studying the basic laws of modern biology at the molecular level, based on the fact that viruses are part of the biosphere and an important factor in the evolution of the organic world.

The history of virology is unusual in that one of its subjects, viral diseases, began to be studied long before the actual viruses were discovered. The beginning of the history of virology is the fight against infectious diseases, and only subsequently - the gradual disclosure of the sources of these diseases. This is confirmed by the work of Edward Jenner (1749-1823) on the prevention of smallpox and the work of Louis Pasteur (1822-1895) with the causative agent of rabies.

Since time immemorial, smallpox has been the scourge of mankind, claiming thousands of lives. Descriptions of smallpox infection are found in the manuscripts of the most ancient Chinese and Indian texts. The first mention of smallpox epidemics on the European continent dates back to the 6th century AD (an epidemic among the soldiers of the Ethiopian army besieging Mecca), after which there was an inexplicable period of time when there was no mention of smallpox epidemics. Smallpox began to roam the continents again in the 17th century. For example, in North America (1617-1619), 9/10 of the population died in Massachusetts, in Iceland (1707) after a smallpox epidemic, only 17 thousand people remained from 57 thousand people, in the city of Eastham (1763 ) out of 1331 inhabitants, 4 people remained. In this regard, the problem of combating smallpox was very acute.

The method of preventing smallpox through vaccination, called variolation, has been known since ancient times. References to the use of variolation in Europe date back to the middle of the 17th century with references to earlier experience in China, the Far East, and Turkey. The essence of variolation was that the contents of pustules from patients who had a mild form of smallpox were introduced into a small wound on the human skin, which caused a mild illness and prevented an acute form. However, at the same time, a great danger of a severe form of smallpox remained, and mortality among the vaccinated reached 10%. Jenner revolutionized smallpox prevention. He was the first to draw attention to the fact that people who had had cowpox, which proceeded easily, subsequently never had smallpox. On May 14, 1796, Jenner introduced into the wound of James Phips, who had never had smallpox, liquid from the pustules of Sarah Selmes, a milkmaid who had cowpox. At the site of artificial infection, the boy developed typical pustules, which disappeared after 14 days. Then Jenner introduced a highly infectious material from the pustules of a smallpox patient into the boy's wound. The boy didn't get sick. This is how the idea of ​​vaccination was born and confirmed (from the Latin word vacca - a cow). In Jenner's time, vaccination was understood as the introduction of vaccinia infectious material into the human body with the aim of preventing smallpox from contracting smallpox. The term vaccine was applied to a substance that prevented smallpox. Since 1840, smallpox vaccine began to be obtained by infecting calves. The human smallpox virus was discovered only in 1904. Thus, smallpox is the first infection against which a vaccine was used, that is, the first controlled infection. Advances in vaccination against smallpox have led to its eradication on a global scale.

Nowadays, vaccination and vaccine are used as general terms for inoculation and inoculation material.

Pasteur, who essentially did not know anything concrete about the causes of rabies, except for the indisputable fact of its infectious nature, used the principle of weakening (attenuation) of the pathogen. In order to weaken the pathogenic properties of the rabies pathogen, a rabbit was used, into the brain of which the brain tissue of a dog that had died of rabies was injected. After the death of a rabbit, its brain tissue was introduced to the next rabbit, and so on. About 100 passages were carried out before the pathogen adapted to the brain tissue of the rabbit. Being introduced subcutaneously into the body of a dog, it showed only moderate properties of pathogenicity. Such a "re-educated" pathogen Pasteur called "fixed", in contrast to the "wild", which is characterized by high pathogenicity. Later, Pasteur developed a method for creating immunity, consisting of a series of injections with a gradually increasing content of a fixed pathogen. The dog that completed the full course of injections was found to be fully resistant to infection. Pasteur came to the conclusion that the process of development of an infectious disease, in essence, is the struggle of microbes with the body's defenses. “Each disease must have its pathogen, and we must contribute to the development of immunity to this disease in the patient's body,” said Pasteur. Still not understanding how the body develops immunity, Pasteur managed to use his principles and direct the mechanisms of this process to the benefit of man. In July 1885, Pasteur had the opportunity to test the properties of a "fixed" rabies agent on a child bitten by a rabid dog. The boy was given a series of injections of an increasingly poisonous substance, with the last injection already containing a completely pathogenic form of the pathogen. The boy remained healthy. The rabies virus was discovered by Remlenge in 1903.

It should be noted that neither the smallpox virus nor the rabies virus was the first discovered virus to infect animals and humans. The first place rightfully belongs to the foot-and-mouth disease virus, discovered by Leffler and Frosch in 1898. These researchers, using multiple dilutions of a filtering agent, showed its toxicity and made a conclusion about its corpuscular nature.

By the end of the 19th century, it became clear that a number of human diseases, such as rabies, smallpox, influenza, yellow fever, are infectious, but their pathogens were not detected by bacteriological methods. Thanks to the work of Robert Koch (1843-1910), who pioneered the technique of pure bacterial cultures, it became possible to distinguish between bacterial and non-bacterial diseases. In 1890, at the X Congress of Hygienists, Koch was forced to declare that "... in the listed diseases, we are not dealing with bacteria, but with organized pathogens that belong to a completely different group of microorganisms." This statement by Koch shows that the discovery of viruses was not a random event. Not only the experience of working with pathogens that are incomprehensible in nature, but also an understanding of the essence of what is happening contributed to the fact that the idea was formulated about the existence of an original group of pathogens of infectious diseases of a non-bacterial nature. It remained to experimentally prove its existence.

The first experimental proof of the existence of a new group of pathogens of infectious diseases was obtained by our compatriot, plant physiologist Dmitry Iosifovich Ivanovsky (1864-1920), while studying tobacco mosaic diseases. This is not surprising, since infectious diseases of an epidemic nature have often been observed in plants. Back in 1883-84. Dutch botanist and geneticist de Vries observed an epidemic of greening flowers and suggested the infectious nature of the disease. In 1886, the German scientist Mayer, who worked in Holland, showed that the sap of plants suffering from mosaic disease, when inoculated, causes the same disease in plants. Meyer was sure that the culprit of the disease was a microorganism, and unsuccessfully searched for it. In the 19th century, tobacco diseases caused great harm to agriculture in our country as well. In this regard, a group of researchers was sent to Ukraine to study tobacco diseases, which, being a student of St. Petersburg University, included D.I. Ivanovsky. As a result of studying the disease, described in 1886 by Mayer as a mosaic disease of tobacco, D.I. Ivanovsky and V.V. Polovtsev came to the conclusion that it represents two different diseases. One of them - "ribbon" - is caused by a fungus, and the other is of unknown origin. The study of tobacco mosaic disease was continued by Ivanovsky in the Nikitsky Botanical Garden under the guidance of Academician A.S. Famycin. Using the juice of a diseased tobacco leaf, filtered through a Chamberlain candle, which retains the smallest bacteria, Ivanovsky caused a disease in tobacco leaves. Cultivation of infected juice on artificial nutrient media did not give results, and Ivanovsky comes to the conclusion that the causative agent of the disease has an unusual nature - it is filtered through bacterial filters and is not able to grow on artificial nutrient media. Heating the juice at 60-70 °C deprived it of infectivity, which testified to the living nature of the pathogen. Ivanovsky first called the new type of pathogen "filterable bacteria". The results of the work of D.I. Ivanovsky were the basis of his dissertation, presented in 1888, and published in the book "On Two Diseases of Tobacco" in 1892. This year is considered the year of the discovery of viruses.

For a certain period of time in foreign publications, the discovery of viruses was associated with the name of the Dutch scientist Beyerink (1851-1931), who also studied tobacco mosaic disease and published his experiments in 1898. Beyerink placed the filtered juice of an infected plant on the surface of an agar, incubated and obtained bacterial colonies on its surface. After that, the upper layer of agar with colonies of bacteria was removed, and the inner layer was used to infect a healthy plant. The plant is sick. From this, Beijerinck concluded that the cause of the disease was not bacteria, but some kind of liquid substance that could penetrate the agar, and called the pathogen "liquid live contagion." Due to the fact that Ivanovsky only described his experiments in detail, but did not pay due attention to the non-bacterial nature of the pathogen, there was a misunderstanding of the situation. Ivanovsky's work gained fame only after Beijerinck repeated and expanded his experiments and emphasized that Ivanovsky proved for the first time precisely the non-bacterial nature of the causative agent of the most typical viral disease of tobacco. Beijerinck himself recognized the primacy of Ivanovsky and, at present, the priority of the discovery of viruses by D.I. Ivanovsky is recognized all over the world.

The word VIRUS means poison. This term was used by Pasteur to refer to the contagious beginning. It should be noted that in the early 19th century, all pathogenic agents were called the word virus. Only after the nature of bacteria, poisons and toxins became clear, the terms "ultravirus", and then simply "virus" began to mean "a new type of filterable pathogen." The term “virus” took root widely in the 30s of our century.

It is now clear that viruses are characterized by ubiquitousness, that is, the ubiquity of distribution. Viruses infect representatives of all living kingdoms: humans, vertebrates and invertebrates, plants, fungi, bacteria.

The first report relating to bacterial viruses was made by Hankin in 1896. In the Chronicle of the Pasteur Institute, he stated that "... the water of some rivers of India has a bactericidal effect ...", which is undoubtedly associated with bacterial viruses. In 1915, Twoorth in London, studying the causes of lysis of bacterial colonies, described the principle of transmission of "lysis" to new cultures in a series of generations. His work, as often happens, actually went unnoticed, and two years later, in 1917, the Canadian de Hérelle rediscovered the phenomenon of bacterial lysis associated with a filtering agent. He named this agent bacteriophage. De Hérelle assumed that there was only one bacteriophage. However, studies by Barnet, who worked in Melbourne in 1924-34, showed a wide variety of bacterial viruses in physical and biological properties. The discovery of the diversity of bacteriophages aroused great scientific interest. In the late 1930s, three researchers - physicist Delbrück, bacteriologists Luria and Hershey, who worked in the USA, created the so-called "Phage Group", whose research in the field of bacteriophage genetics ultimately led to the birth of a new science - molecular biology.

The study of insect viruses has lagged far behind the virology of vertebrates and humans. It is now clear that insect-infecting viruses can be conditionally divided into 3 groups: insect viruses proper, animal and human viruses, for which insects are intermediate hosts, and plant viruses, which also infect insects.

The first insect virus that has been identified is the silkworm jaundice virus (silkworm polyhedrosis virus, named Bollea stilpotiae). As early as 1907, Provacek showed that the filtered homogenate of diseased larvae is infectious for healthy silkworm larvae, but it was not until 1947 that the German scientist Bergold discovered rod-shaped virus particles.

One of the most fruitful studies in the field of virology is Reid's study of the nature of yellow fever on US Army volunteers in 1900-1901. It has been convincingly demonstrated that yellow fever is caused by a filterable virus transmitted by mosquitoes and mosquitoes. Mosquitoes have also been found to remain non-infectious after ingesting infectious blood for two weeks. Thus, the external incubation period of the disease (the time required for the reproduction of the virus in the insect) was determined and the basic principles of the epidemiology of arbovirus infections (viral infections transmitted by blood-sucking arthropods) were established.

The ability of plant viruses to reproduce in their carrier - an insect was shown in 1952 to Maramorosh. The researcher, using an insect injection technique, convincingly demonstrated the ability of the aster jaundice virus to multiply in its vector, the six-spotted cicada.

1.2. Stages of development of virology

The history of achievements in virology is directly related to the success of the development of the methodological base of research.

^ Late 19th - early 20th century. The main method for identifying viruses during this period was the method of filtration through bacteriological filters (Chamberland candles), which were used as a means of separating pathogens into bacteria and non-bacteria. Using filterability through bacteriological filters, the following viruses have been discovered:

1892 - tobacco mosaic virus;

1898 - FMD virus;

1899 - rinderpest virus;

1900 - yellow fever virus;

1902 - fowl and sheep pox virus;

1903 - rabies virus and swine fever virus;

1904 - Human smallpox virus;

1905 - Canine distemper virus and vaccine virus;

1907 - dengue virus;

1908 - smallpox and trachoma virus;

1909 - polio virus;

1911 Rous sarcoma virus;

1915 - bacteriophages;

1916 - measles virus;

1917 - herpes virus;

1926 - vesicular stomatitis virus.

30s - the main virological method used for the isolation of viruses and their further identification are laboratory animals (white mice - for influenza viruses, newborn mice - for Coxsackie viruses, chimpanzees - for hepatitis B virus, chickens, pigeons - for oncogenic viruses , gnotobiont piglets - for intestinal viruses, etc.). The first to systematically use laboratory animals in the study of viruses was Pasteur, who as early as 1881 carried out studies on the inoculation of material from patients with rabies into the brain of a rabbit. Another milestone is the work on the study of yellow fever, which resulted in the use of newborn mice in virological practice. The culmination of this cycle of work was the isolation by Cycles in 1948 of a group of epidemic myalgia viruses on suckling mice.

1931 - chicken embryos, which are highly sensitive to influenza, smallpox, leukemia, chicken sarcoma and some other viruses, began to be used as an experimental model for virus isolation. And now chicken embryos are widely used for the isolation of influenza viruses.

1932 - English chemist Elford creates artificial finely porous colloidal membranes - the basis for the ultrafiltration method, with which it became possible to determine the size of viral particles and differentiate viruses on this basis.

1935 - The use of the centrifugation method made it possible to crystallize the tobacco mosaic virus. Currently, centrifugation and ultracentrifugation methods (acceleration at the bottom of the tube exceeds 200,000 g) are widely used for virus isolation and purification.

In 1939, an electron microscope with a resolution of 0.2-0.3 nm was used for the first time to study viruses. The use of ultrathin tissue sections and the method of negative staining of aqueous suspensions made it possible to study the interaction of viruses with a cell and to study the structure (architecture) of virions. The information obtained using an electron microscope was significantly expanded using X-ray diffraction analysis of crystals and pseudocrystals of viruses. The improvement of electron microscopes culminated in the creation of scanning microscopes, which make it possible to obtain three-dimensional images. Using the method of electron microscopy, the architecture of virions and the features of their penetration into the host cell were studied.

During this period, the bulk of the viruses were discovered. The following can be given as an example:

1931 swine influenza virus and western equine encephalomyelitis virus;

1933 - human influenza virus and eastern equine encephalomyelitis virus;

1934 - mumps virus;

1936 - mouse breast cancer virus;

1937 - tick-borne encephalitis virus.

40s. In 1940, Hoagland and colleagues found that the vaccinia virus contains DNA, but not RNA. It became apparent that viruses differ from bacteria not only in size and inability to grow without cells, but also in that they contain only one type of nucleic acid - DNA or RNA.

1941 - American scientist Hurst on the model of the influenza virus discovered the phenomenon of hemagglutination (gluing of red blood cells). This discovery formed the basis for the development of methods for the detection and identification of viruses and contributed to the study of the interaction of the virus with the cell. The principle of hemagglutination is the basis of a number of methods:

^ RHA - hemagglutination reaction - used to detect and titrate viruses;

RTGA - hemagglutination inhibition reaction - is used for the identification and titration of viruses.

1942 - Hurst establishes the presence of an enzyme in the influenza virus, which was later identified as neuraminidase.

1949 - discovery of the possibility of culturing animal tissue cells under artificial conditions. In 1952, Enders, Weller, and Robbins received the Nobel Prize for their development of the cell culture method.

The introduction of the cell culture method into virology was an important event that made it possible to obtain culture vaccines. Of the currently widely used cultured live and killed vaccines based on attenuated strains of viruses, vaccines against poliomyelitis, mumps, measles and rubella should be noted.

The creators of polio vaccines are American virologists Sabin (a trivalent live vaccine based on attenuated strains of polioviruses of three serotypes) and Salk (a killed trivalent vaccine). In our country, Soviet virologists M.P. Chumakov and A.A. Smorodintsev developed a technology for the production of live and killed polio vaccines. In 1988, the World Health Assembly challenged WHO to eradicate poliomyelitis from the world by completely stopping the circulation of wild poliovirus. To date, great progress has been made in this direction. The use of global vaccination against poliomyelitis with the use of "round" vaccination schemes has not only dramatically reduced the incidence, but also created areas free from the circulation of wild poliovirus.

Viruses discovered:

1945 - Crimean hemorrhagic fever virus;

1948 - Coxsackie viruses.

50s. In 1952, Dulbecco developed a method for titrating plaques in a monolayer of chick embryo cells, which made it possible to introduce a quantitative aspect into virology. 1956-62 Watson, Kaspar (USA) and Klug (Great Britain) develop a general theory of the symmetry of virus particles. The structure of the virus particle has become one of the criteria in the virus classification system.

This period was characterized by significant advances in the field of bacteriophages:

The induction of the prophage of lysogenizing phages was established (Lvov et al., 1950);

It has been proven that infectivity is inherent in phage DNA, and not in the protein shell (Hershey, Chase, 1952);

The phenomenon of general transduction was discovered (Zinder, Lederberg, 1952).

The infectious tobacco mosaic virus was reconstructed (Frenkel-Konrad, Williams, Singer, 1955-57), in 1955 the poliomyelitis virus was obtained in crystalline form (Schaffer, Schwerd, 1955).

Viruses discovered:

1951 - murine leukemia viruses and ECHO;

1953 - adenoviruses;

1954 - rubella virus;

1956 - parainfluenza viruses, cytomegalovirus, respiratory syncytial virus;

1957 - polyoma virus;

1959 - Argentine hemorrhagic fever virus.

The 1960s and subsequent years are characterized by the flourishing of molecular biological research methods. Achievements in the field of chemistry, physics, molecular biology and genetics formed the basis of the methodological base of scientific research, which began to be applied not only at the level of methods, but also entire technologies, where viruses act not only as an object of research, but also as a tool. No discovery in molecular biology is complete without a viral model.

1967 - Cathes and McAuslan demonstrate the presence of a DNA-dependent RNA polymerase in the vaccinia virion. The following year, RNA-dependent RNA polymerase is found in reoviruses, and then in paramyxo and rhabdoviruses. In 1968, Jacobson and Baltimore establish the presence in polioviruses of a genomic protein connected to RNA, Baltimore and Boston establish that the poliovirus genomic RNA is translated into a polyprotein.

Viruses discovered:

1960 - rhinoviruses;

1963 - Australian antigen (HBsAg).

70s. Baltimore, together with Temin and Mizutani, report the discovery of the enzyme reverse transcriptase (revertase) in the composition of RNA-containing oncogenic viruses. The study of the genome of RNA-containing viruses is becoming real.

The study of gene expression in eukaryotic viruses provided fundamental information about the molecular biology of eukaryotes themselves - the existence of the mRNA cap structure and its role in RNA translation, the presence of a polyadenyl sequence at the 3' end of mRNA, splicing, and the role of enhancers in transcription were first identified in the study of animal viruses.

1972 - Berg publishes a report on the creation of a recombinant DNA molecule. There is a new branch of molecular biology - genetic engineering. The use of recombinant DNA technology makes it possible to obtain proteins that are important in medicine (insulin, interferon, vaccines). 1975 - Koehler and Milstein produce the first lines of hybrids producing monoclonal antibodies (MABs). Based on MCA, the most specific test systems for the diagnosis of viral infections are being developed. 1976 - Blumberg for the discovery of HBsAg receives the Nobel Prize. It has been established that hepatitis A and hepatitis B are caused by different viruses.

Viruses discovered:

1970 - hepatitis B virus;

1973 - rotaviruses, hepatitis A virus;

1977 - hepatitis delta virus.

80s. The development laid down by the domestic scientist L.A. Zilber's ideas that the occurrence of tumors may be associated with viruses. The components of viruses responsible for the development of tumors are called oncogenes. Viral oncogenes turned out to be among the best model systems that help to study the mechanisms of oncogenetic transformation of mammalian cells.

1985 - Mullis receives the Nobel Prize for the discovery of the polymerase chain reaction (PCR). This is a molecular genetic diagnostic method, which, in addition, has made it possible to improve the technology for obtaining recombinant DNA and discover new viruses.

Viruses discovered:

1983 - human immunodeficiency virus;

1989 - hepatitis C virus;

1995 - Hepatitis G virus discovered using PCR.

1.3. Development of the concept of the nature of viruses

Answers to the questions "What are viruses?" and "What is their nature?" have been the subject of discussion for many years since their discovery. In the 20-30s. no one doubted that viruses are living matter. In 30-40 years. it was believed that viruses are microorganisms, since they are able to reproduce, have heredity, variability and adaptability to changing environmental conditions, and, finally, are subject to biological evolution, which is provided by natural and artificial selection. In the 1960s, early advances in molecular biology marked the decline of the concept of viruses as organisms. In the ontogenetic cycle of the virus, two forms are distinguished - extracellular and intracellular. The term VIRION has been introduced to designate the extracellular form of the virus. Differences between its organization and the structure of cells have been established. The facts pointing to a type of reproduction completely different from cells, called disjunctive reproduction, are summarized. Disjunctive reproduction is the temporal and territorial disunity of the synthesis of viral components - genetic material and proteins - from the subsequent assembly and formation of virions. It has been shown that the genetic material of viruses is represented by one of two types of nucleic acid (RNA or DNA). It is formulated that the main and absolute criterion for distinguishing viruses from all other forms of life is the absence of their own protein-synthesizing systems.

The accumulated data allowed us to conclude that viruses are not organisms, even the smallest ones, since any, even minimal organisms such as mycoplasmas, rickettsia and chlamydia have their own protein-synthesizing systems. According to the definition formulated by academician V.M. Zhdanov, viruses are autonomous genetic structures capable of functioning only in cells with varying degrees of dependence on cellular systems for the synthesis of nucleic acids and complete dependence on cellular protein-synthesizing and energy systems, and undergoing independent evolution.

Thus, viruses are a diverse and numerous group of non-cellular life forms that are not microorganisms, and united in the kingdom Vira. Viruses are studied within the framework of virology, which is an independent scientific discipline that has its own object and methods of research.

Virology is divided into general and particular, and virological research is divided into fundamental and applied. The subject of fundamental research in virology is the architecture of virions, their composition, the features of the interaction of viruses with the cell, the methods of transferring hereditary information, the molecular mechanisms of the synthesis of elements and the process of their integration into a whole, the molecular mechanisms of the variability of viruses and their evolution. Applied research in virology is related to the solution of problems in medicine, veterinary medicine and phytopathology.

CHAPTER 2

^ STRUCTURAL AND MOLECULAR ORGANIZATION OF VIRUSES

In the ontogenetic cycle of the virus, two stages are distinguished - extracellular and intracellular, and, accordingly, two forms of its existence - the virion and the vegetative form. A virion is a whole viral particle, mainly composed of protein and nucleic acid, often resistant to environmental factors and adapted to transfer genetic information from cell to cell. The vegetative form of the virus exists in a single virus-cell complex and only in their close interaction.

2.1. Virion architecture

The extracellular form of the virus - the virion, designed to preserve and transfer the nucleic acid of the virus, is characterized by its own architecture, biochemical and molecular genetic features. The architecture of virions is understood as the ultrafine structural organization of these supramolecular formations, which differ in size, shape, and structural complexity. To describe the architecture of viral structures, a nomenclature of terms has been developed:

A protein subunit is a single polypeptide chain folded in a certain way.

Structural unit (structural element) - a protein ensemble of a higher order, formed by several chemically linked identical or non-identical subunits.

Morphological unit - a group of protrusions (cluster) on the surface of the capsid, visible in an electron microscope. Clusters consisting of five (pentamers) and six (hexamers) protrusions are often observed. This phenomenon is called pentameric-hexameric clustering. If the morphological unit corresponds to a chemically significant formation (retains its organization under conditions of mild disintegration), then the term capsomer is used.

Capsid - an outer protein sheath or sheath that forms a closed sphere around the genomic nucleic acid.

Core (core) - the inner protein shell, directly adjacent to the nucleic acid.

Nucleocapsid is a complex of protein with nucleic acid, which is a packaged form of the genome.

Supercapsid or peplos is a virion shell formed by a lipid membrane of cellular origin and viral proteins.

Matrix is ​​a protein component located between the supercapsid and the capsid.

Ash gauges and spines are superficial protrusions of the supercapsid.

As already noted, viruses can pass through the most microscopic pores that trap bacteria, for which they were called filtering agents. The filterability property of viruses is due to the size calculated in nanometers (nm), which is several orders of magnitude smaller than the size of the smallest microorganisms. The sizes of viral particles, in turn, fluctuate within a relatively wide range. The smallest simple viruses have a diameter of just over 20 nm (parvoviruses, picornaviruses, Qβ phage), medium-sized viruses - 100-150 nm (adenoviruses, coronaviruses). The largest recognized vaccinia virus particles, the size of which reach 170x450 nm. The length of filamentous plant viruses can be 2000 nm.

Representatives of the kingdom Vira are characterized by a variety of forms. In terms of their structure, viral particles can be simple formations, or they can be quite complex ensembles that include several structural elements. A conditional model of a hypothetical virion, including all possible structural formations, is shown in Figure 1.

There are two types of viral particles (VP), fundamentally different from each other:

1) HF, devoid of an envelope (non-enveloped or uncoated virions);

2) HF having an envelope (enveloped or coated virions).

Rice. 1. The structure of a hypothetical virion

2.1.1. The structure of virions without an envelope

Three morphological types of virions without an envelope have been identified: rod-shaped (filamentous), isometric, and club-shaped (Fig. 2). The existence of the first two types of uncoated virions is determined by the manner in which the nucleic acid folds and interacts with proteins.

1. Protein subunits bind to the nucleic acid, extending along it in a periodic manner so that it coils into a helix and forms a structure called the nucleocapsid. This way of regular, periodic interaction of protein and nucleic acid determines the formation of rod-shaped and filamentous viral particles.

2. The nucleic acid is not bound to the protein sheath (possible non-covalent bonds are very mobile). This principle of interaction determines the formation of isometric (spherical) viral particles. The protein coats of viruses that are not bound to a nucleic acid are called a capsid.

3. Club-shaped virions have a differentiated structural organization and consist of a number of discrete structures. The main structural elements of the virion are the isometric head and the tail process. Depending on the virus, a sleeve, neck, collar, tail rod, tail sheath, basal plate, and fibrils may also be present in the virion structure. Bacteriophages of the T-even series have the most complex differentiated structural organization, the virion of which consists of all the listed structural elements.

Virions or their components can have two main types of symmetry (the property of bodies to repeat their parts) - helical and icosahedral. In the event that the components of the virion have different symmetry, then they speak of a combined type of HF symmetry. (scheme 1).

The helical stacking of macromolecules is described by the following parameters: the number of subunits per turn of the helix (u, the number is not necessarily an integer); distance between subunits along the axis of the helix (p); helix pitch (P); P=pu. A classic example of a virus with helical symmetry is the tobacco mosaic virus (TMV). The nucleocapsid of this 18x300 nm rod-shaped virus consists of 2130 identical subunits, with 16 1/3 subunits per helix turn, and the helix pitch is 2.3 nm.

Icosahedral symmetry is the most efficient for constructing a closed

Virology (from lat. vīrus - "poison" and Greek logos - word, doctrine) - the science of viruses, a section of biology.

Virology emerged as an independent discipline in the middle of the 20th century. It arose as a branch of pathology - human and animal pathology on the one hand, and phytopathology - on the other. Initially, the virology of humans, animals and bacteria developed within the framework of microbiology. The subsequent successes of virology are largely based on the achievements of related natural sciences - biochemistry and genetics. The object of study of virology are subcellular structures - viruses. By their structure and organization, they belong to macromolecules, therefore, since the time when a new discipline took shape, molecular biology, which combined various approaches to the study of the structure, functions and organization of macromolecules that determine biological specificity, virology has also become an integral part of molecular biology. Molecular biology widely uses viruses as a research tool, and virology uses molecular biology methods to solve its problems.

History of virology

Viral diseases such as smallpox, poliomyelitis, yellow fever, tulip variegation have been known since ancient times, but no one knew anything about the causes that caused them for a long time. At the end of the 19th century, when it was possible to establish the microbial nature of a number of infectious diseases, pathologists came to the conclusion that many of the common diseases of humans, animals and plants cannot be explained by infection with bacteria.

The discovery of viruses is associated with the names of D.I. Ivanovsky and M. Beyerink. In 1892, D.I. Ivanovsky showed that the disease of tobacco - tobacco mosaic - can be transferred from diseased plants to healthy ones if they are infected with the juice of diseased plants, previously passed through a special filter that traps bacteria. In 1898, M. Beijerink confirmed the data of D.I. Ivanovsky and formulated the idea that the disease is not caused by a bacterium, but by a fundamentally new, different from bacteria, infectious agent. He called it contagium vivum fluidum - a living liquid infectious principle. At that time, the term “virus” was used to denote the infectious beginning of any disease - from the Latin word “poison”, “poisonous beginning”. Сontagium vivum fluidum came to be called a filterable virus, and later simply a "virus". In the same year, 1898, F. Lefleur and P. Froshsh showed that the causative agent of foot-and-mouth disease in cattle passes through bacterial filters. Shortly thereafter, it was found that other diseases of animals, plants, bacteria and fungi are caused by similar agents. In 1911, P. Rous discovered a virus that causes tumors in chickens. In 1915, F. Twort, and in 1917 F. D'Herelle independently discovered bacteriophages - viruses that destroy bacteria.

The nature of these pathogens remained unclear for more than 30 years - until the early 30s. This was explained by the fact that traditional microbiological research methods could not be applied to viruses: viruses, as a rule, are not visible in a light microscope and do not grow on artificial nutrient media.

Categories:Detailing concepts:

Municipal state educational institution

"Secondary school No. 3"

Stavropol Territory, Stepnovsky District,
v. Bogdanovka

MKOU secondary school No. 3, student of grade 10
Scientific adviser:

Toboeva Natalya Konstantinovna
teacher of geography, biology, MKOU secondary school №3

I .Introduction

II .Main part:

1. Discovery of viruses

2. Origin of viruses

3. Structure

4. Penetration into the cell

5. Flu

6.Chickenpox 7.Tick-borne encephalitis 8.The future of virology

III.Conclusion

IV. Bibliography

V. Application

Object of study:

Non-cellular life forms are viruses.

Subject of study:

Present and future of virology.

Objective:

To find out the importance of virology at the present time, to determine its future. The set goal could be achieved as a result of solving the following tasks:

1) the study of literature covering the structure of viruses as non-cellular life forms;

2) study of the causes of viral diseases, as well as their prevention.

This determined the topic of my research.

I. Introduction.

The action-packed and fascinating history of virology is distinguished by triumphant victories, but, unfortunately, also by defeats. The development of virology is associated with the brilliant successes of molecular genetics.

The study of viruses has led to an understanding of the fine structure of genes, the deciphering of the genetic code, and the identification of mutation mechanisms.

Viruses are widely used in genetic engineering and research.

But their cunning and ability to adapt knows no bounds, their behavior in each case is unpredictable. Victims of viruses are millions of people who died from smallpox, yellow fever, AIDS and other diseases. Much remains to be discovered and known. Nevertheless, the main successes in virology have been achieved in the fight against specific diseases. That is why scientists say that virology will take the leading place in the third millennium.

What has virology given to humanity in the fight against its formidable enemy, the virus? What is its structure, where and how does it live, how does it reproduce, what other “surprises” does it prepare? These are the questions I have considered in my work.

II .Main part:

1. Discovery of viruses.

The discoverer of the world of viruses was the Russian botanist D.I. Ivanovsky. In 1891-1892. he persistently searched for the causative agent of tobacco mosaic disease. The scientist studied the liquid obtained by rubbing diseased tobacco leaves. I filtered it through filters that should not have missed a single bacterium. Patiently, he pumped liters of juice taken from the leaves of mosaic tobacco into hollow bacterial filters made of finely porous porcelain, resembling long candles. The walls of the filter were sweating with transparent droplets that flowed into a pre-sterilized vessel. With light rubbing, the scientist applied a drop of such filtered juice to the surface of the tobacco leaf. After 7-10 days, undoubted signs of mosaic disease appeared in previously healthy plants. A droplet of filtered sap from an infected plant would attack any other tobacco plant with mosaic disease. The infection could pass from plant to plant without end, like a flame of fire from one thatched roof to another.

In the future, it was possible to establish that many other viral pathogens of infectious diseases of humans, animals and plants capable of passing through could be seen through the most advanced light microscopes. Particles of various viruses could be seen only through the window of an all-seeing device - an electron microscope, which gives an increase of hundreds of thousands of times.

D.I. Ivanovsky did not attach much importance to this fact, although he described his experience in detail.

His work gained fame after, in 1899, the Dutch botanist and microbiologist Martin Beijerinck confirmed the results of D.I. Ivanovsky's research. M. Beijerink proved that the mosaic of tobacco can be transferred from one plant to another using filtrates. These studies marked the beginning of the study of viruses and the emergence of virology as a science.

2. Origin of viruses.

3. Structure.

Being completely primitive creatures, viruses have all the basic properties of living organisms. They reproduce offspring similar to the original parental forms, although their mode of reproduction is peculiar and differs in many respects from what is known about the reproduction of other creatures. Their metabolism is closely related to the metabolism of host cells. They have a heredity characteristic of all living organisms. Finally, they, like all other living beings, are characterized by variability and adaptability to changing environmental conditions.

The largest viruses (for example, smallpox viruses) reach a size of 400-700 nm and approach the size of small bacteria, the smallest (causative agents of poliomyelitis, encephalitis, foot and mouth disease) measure only tens of nanometers, i.e. close to large protein molecules, in particular blood hemoglobin molecules.

Viruses have a variety of shapes - from spherical to filamentous. Electron microscopy allows not only to see viruses, to determine their shapes and sizes, but also to study the spatial structure - molecular architectonics.

For viruses, a relatively simple composition is typical: nucleic acid (RNA or DNA), protein, more complex in structure contain carbohydrates and lipids, sometimes they also have a number of their own enzymes.

As a rule, the nucleic acid is located in the center of the viral particle and is protected from adverse effects by a protein shell - capsomeres. Observations in an electron microscope showed that a particle of viruses

(or virions) in form are of several basic types.

Some viruses (usually the simplest ones) resemble regular geometric bodies. Their protein shell almost always approaches the shape of an icosahedron (regular twenty-sided) with faces of equilateral triangles. These virions are called cubic (for example, the polio virus). The nucleic acid of such a virus is often twisted into a ball. Particles of other viruses are in the form of oblong rods. In this case, their nucleic acid is surrounded by a cylindrical capsid. Such virions are called helical (for example, tobacco mosaic virus).

Viruses of a more complex structure, in addition to the icosahedral or helical capsid, also have an outer shell, which consists of a variety of proteins (many of them are enzymes), as well as lipids and carbons.

The physical structure of the outer shell is very variable and not as compact as that of the capsid. For example, the herpes virus is a helical enveloped virion. There are viruses with an even more complex structure. Thus, the smallpox virus does not have a visible capsid (protein shell), but its nucleic acid is surrounded by several shells.

4. Penetration into the cell.

As a rule, the penetration of the virus into the cytoplasm of the cell is preceded by its binding to a specific receptor protein located on the cell surface. Binding to the receptor is carried out due to the presence of special proteins on the surface of the viral cell. The area of ​​the cell surface, to which the virus has joined, sinks into the cytoplasm and turns into a vacuole. The vacuole wall, which consists of a cytoplasmic membrane, can merge with other vacuoles or the nucleus. So the virus is delivered to any part of the cell.

The receptor mechanism for the penetration of the virus into the cell ensures the specificity of the infectious process. The infectious process begins when the viruses that have entered the cell begin to multiply, i.e. viral genome replication and self-assembly of the capsid occur. For reduplication to occur, the nucleic acid must be freed from the capsid. After the synthesis of a new nucleic acid molecule, it is dressed with viral proteins synthesized in the cytoplasm of the host cell - a capsid is formed.

Accumulation of viral particles leads to withdrawal from the cell. For some viruses, this happens by "explosion", while the integrity of the cell is violated and it dies. Other viruses are shed in a manner resembling budding. In this case, the cells can maintain their viability.

Bacteriophage viruses have a different way of penetration into the cell. The bacteriophage inserts a full rod into the cell and pushes the DNA (or RNA) that is in its head through it. The bacteriophage genome is located in

cytoplasm, and the capsid remains outside. In the bacterial cytoplasm, the reduplication of the bacteriophage genome, the synthesis of its proteins, and the formation of the capsid begin. After a certain period of time, the bacterial cell dies, and mature particles enter the environment.

5. Flu.

Influenza is an acute infectious disease caused by a filtering virus that causes general intoxication and damage to the mucous membrane of the upper respiratory tract.

It has now been established that the influenza virus has several serological types that differ in their antigenic structure.

There are such varieties of the influenza virus: A, B, C, D. Virus A has 2 subspecies, designated:A 1 and A2.

The influenza virus outside the human body is unstable and quickly dies. Vacuum-dried virus can be stored for a long time.

Disinfectants quickly destroy the virus, and ultraviolet radiation and heating also have a detrimental effect on the virus.

Allow the possibility of infection from a virus carrier. The virus is transmitted from a sick person to a healthy person by airborne droplets. Coughing and sneezing can spread the infection.

Epidemics of viral influenza most often occur during the cold season.

An influenza patient is contagious for 5-7 days. All people who have not had the flu are susceptible to the disease. After suffering the flu, immunity remains for 2-3 years.

The incubation period is short - from several hours to 3 days. Most often 1-2 days.

There are usually no prodromes, and sudden onset is characteristic. Chills, headache, general weakness appear, the temperature rises to 39-40 degrees. Patients complain of soreness during rotation of the eyes, aching joints, muscles, sleep is disturbed, sweating is different. All this indicates a general intoxication with the involvement of the nervous system in the process.

The central nervous system is especially sensitive to the toxic effects of the influenza virus, which is clinically expressed in severe adynamia, irritability, and the sense of smell and taste are reduced.

On the part of the digestive tract, the phenomena of influenza intoxication are also different: loss of appetite, stool retention, sometimes, more often in young children, diarrhea.

The tongue is coated with a coating, slightly swollen, which leads to the appearance of impressions of the teeth along the edges. The temperature remains elevated for 3-5 days and, in the absence of complications, gradually decreases to normal or drops critically.

After 1-2 days, a runny nose, laryngitis, bronchitis may appear. Often there is bleeding from the nose. Cough at first dry, turns into cough with phlegm. Vascular disorders are expressed in the form of a decrease in blood pressure, pulse instability and disturbance of its rhythm.

Uncomplicated influenza usually resolves within 3-5 days, however, full recovery takes 1-2 weeks.

Like any infection, influenza can occur in mild, severe, hypertoxic and fulminant forms.

Along with this, the viral flu can be extremely mild and endure on the legs, ending within 1-2 days. These forms of influenza are called erased.

Influenza infection can cause complications from various organ systems. Most often in children, influenza is complicated by pneumonia, otitis media, which is accompanied by fever, anxiety, sleep disturbance.

Complications from the peripheral nervous system are expressed in the form of neuralgia, neuritis, radiculitis.

Treatment:

The patient must be provided with bed rest and rest. Bed rest must be maintained for some time, and after a drop in temperature. Systematic airing of the room, daily warm or hot baths, good nutrition - all this increases the body's resistance in the fight against influenza.

Specific treatment of viral influenza is carried out using anti-influenza polyvalent serum proposed by A.A. Smorodintsev.

Of the symptomatic agents that reveal headache, pain in muscles and joints, as well as neurological pain, pyryramidone, phenacetin, aspirin with caffeine are prescribed.

In severe toxicosis, intravenous administration of glucose is prescribed. With uncomplicated influenza, antibiotics are not used, because. They don't work on the virus anymore. With a dry cough, hot milk with soda or borjom is useful.

Prevention:

Patients should be isolated at home or in hospitals. If the patient is left at home, it is necessary to place him in a separate room or separate his bed with a screen or sheet. Caregivers should wear a gauze mask that covers the nose and mouth.

6.Chickenpox.

Chicken pox is an acute infectious disease caused by a virus and characterized by a rash on the skin and mucous membranes of a spotty-vesicular rash.

The causative agent of chickenpox is a filter virus and is found in chickenpox vesicles, as well as in the blood. The virus is characterized by instability and various environmental influences and quickly dies.

The source of infection is a patient who is contagious during the rash and at the end of incubation. The infection is spread by airborne droplets. The disease is not transmitted through objects.

Immunity after chicken pox remains for life. The incubation period lasts from 11 to 21 days, with an average of 14 days.

In most cases, the disease begins immediately, and only sometimes there are harbingers in the form of a moderate increase in temperature with symptoms of general malaise. The prodromes may be accompanied by an eruption resembling scarlet fever or measles.

With a moderate rise in temperature, a spotty rash of various sizes appears on different parts of the body - from a pinhead to lentils. Over the next hours, a bubble with transparent contents surrounded by a red rim forms in place of the spots. Chickenpox vesicles (vesicles) are located on intact skin, tender and soft to the touch. The content of the vesicle soon becomes cloudy, and the vesicle itself bursts (2-3 days) and turns into a crust, which disappears after 2-3 weeks, usually leaving no scar. Rashes and subsequent blistering can be profuse, covering the entire scalp, trunk, limbs, while on the face of the distal parts of the limbs they are less abundant.

The course of chicken pox is usually accompanied by a slight violation of the general condition of the patient. Each new rash causes an increase in temperature to 38 ° and above. This reduces appetite.

In addition to the skin, chicken rash can affect the mucous membranes of the mouth, conjunctiva, genitals, larynx, etc.

Treatment:

Bed linen should always be clean. Take warm baths (35 ° -37 °) from weak solutions of potassium permanganate. The patient's hands should be clean with short-cut nails.

Separate vials are lubricated with iodine or potassium solution, 1% alcohol solution of brilliant green.

With purulent complications caused by a secondary infection, treatment is carried out with antibiotics (penicillin, streptomycin, biomycin)

Prevention:

A person infected with chickenpox must be isolated at home. Disinfection is not carried out, the room is ventilated and subjected to wet cleaning.

7. Tick-borne encephalitis.

An acute viral disease characterized by damage to the gray matter of the brain and spinal cord. The reservoir to the sources of infection are wild animals (mainly rodents) and ixodid ticks. Infection is possible not only by sucking a tick, but also by drinking the milk of infected goats. The causative agent belongs to arboviruses. The gate of infection is the skin (with suction of ticks) or the mucous membrane of the digestive tract (with alimentary infection). The virus penetrates hematogenously into the central nervous system, causing the most pronounced changes in the nerve cells of the anterior horns of the cervical spinal cord and in the nuclei of the medulla oblongata.

The incubation period is from 8 to 23 days (usually 7-14 days). The disease begins acutely: chills, severe headache, weakness appear. After suffering encephalitis, persistent consequences may remain in the form of flaccid paralysis of the muscles of the neck and shoulder girdle.

Treatment:

Strict bed rest:

with mild forms - 7-10 days,

with moderate - 2-3 weeks,

with severe - even longer.

Prevention:

When a tick is sucked in an area unfavorable for encephalitis, it is necessary to administer anti-encephalitis gamma globulin. According to the indications, preventive vaccination is carried out.

8. The future of virology.

What are the prospects for the development of virology in the 21st century? In the second half of the 20th century, progress in virology was associated with classical discoveries in biochemistry, genetics, and molecular biology. Modern virology intertwines the successes of fundamental applied sciences, so its further development will follow the path of in-depth study of the molecular basis of the pathogenicity of viruses of new previously unknown pathogens (prions and virions), the nature and mechanisms of virus persistence, their ecology, the development of new and improvement of existing methods of diagnostics and specific prevention of viral diseases.

So far, there is no more important aspect in virology than the prevention of infections. Over the 100 years of the existence of the science of viruses and viral diseases, vaccines have undergone great changes, having gone from the attenzated and killed vaccines of the time of Pasteur to modern genetically engineered and synthetic vaccine preparations. This direction will continue to develop, based on physicochemical genetic engineering and synthetic experiments in order to create polyvalent vaccines that require minimal vaccinations as early as possible after birth. Chemotherapy will be developed, a relatively new approach for virology. These drugs are useful only in some cases.

III. Conclusion.

Mankind faces many complex unresolved virological problems: latent viral infections, viruses and tumors, etc. The level of development of today's virology, however, is such that means of fighting infections will definitely be found. It is very important to understand that viruses are not an element alien to wildlife, they are a necessary component of the biosphere, without which adaptation, evolution, immune defense and other interactions of living objects with the environment would probably not be possible. Understanding viral diseases as pathologies of adaptation, the fight against them should be aimed at raising the status of the immune system, and not at the destruction of viruses.

An analysis of various literary sources and statistical data led to the following conclusions:

viruses are autonomous genetic compounds of the structure that are unable to develop outside the cell;

3) are a variety of shapes and simple composition.

Bibliography:

1. Great Soviet Encyclopedia: V.8 / Ed. B.A. Vvedensky.

2. Denisov I.N., Ulumbaev E.G. Handbook - guide of a practicing doctor. - M .: Medicine, 1999.

3. Zverev I.D. Reading book on human anatomy, physiology and hygiene.- M.: Enlightenment, 1983.

4. Luria S. et al. General virology.- M.: Mir, 1981.

6. Pokrovsky V.I. Popular medical encyclopedia.- M.: Oniks, 1998.

7.Tokarik E.N. Virology: present and future // Biology at school.-2000.- No. 2-3.

The human body is prone to all kinds of diseases and infections; animals and plants also get sick quite often. Scientists of the last century tried to identify the cause of many diseases, but even having determined the symptoms and course of the disease, they could not confidently say about its cause. And only at the end of the nineteenth century did such a term as "viruses" appear. Biology, or rather one of its sections - microbiology, began to study new microorganisms, which, as it turned out, have long been adjacent to humans and contribute to the deterioration of his health. In order to more effectively fight viruses, a new science emerged - virology. It is she who can tell a lot of interesting things about ancient microorganisms.

Viruses (biology): what is it?

Only in the nineteenth century, scientists found that the causative agents of measles, influenza, foot-and-mouth disease and other infectious diseases, not only in humans, but also in animals and plants, are microorganisms invisible to the human eye.

After the viruses were discovered, biology was not immediately able to answer the questions posed about their structure, origin and classification. Humanity has a need for a new science - virology. At the moment, virologists are working on the study of already familiar viruses, watching their mutations and inventing vaccines to protect living organisms from infection. Quite often, for the purpose of the experiment, a new strain of the virus is created, which is stored in a "sleeping" state. On its basis, drugs are being developed and observations are being made on their effects on organisms.

In modern society, virology is one of the most important sciences, and the most sought-after researcher is a virologist. The profession of a virologist, according to sociologists, is becoming more and more popular every year, which well reflects the trends of our time. After all, according to many scientists, soon wars will be waged with the help of microorganisms and ruling regimes will be established. Under such conditions, a state with highly qualified virologists may be the most resilient, and its population the most viable.

The emergence of viruses on Earth

Scientists attribute the emergence of viruses to the most ancient times on the planet. Although it is impossible to say exactly how they appeared and what form they had at that time. After all, viruses have the ability to penetrate absolutely any living organisms, they have access to the simplest forms of life, plants, fungi, animals and, of course, humans. But viruses do not leave behind any visible remains in the form of fossils, for example. All these features of the life of microorganisms significantly complicate their study.

• they were part of the DNA and separated over time;
• they were built into the genome from the very beginning and under certain circumstances "woke up", began to multiply.

Scientists suggest that in the genome of modern people there is a huge number of viruses that our ancestors were infected with, and now they have naturally integrated into DNA.

Viruses: when were they discovered

The study of viruses is a fairly new section in science, because it is believed that it appeared only at the end of the nineteenth century. In fact, it can be said that an English doctor unconsciously discovered the viruses themselves and their vaccines at the end of the nineteenth century. He worked on the creation of a cure for smallpox, which at that time mowed down hundreds of thousands of people during an epidemic. He managed to create an experimental vaccine directly from the sore of one of the girls who had smallpox. This vaccine proved to be very effective and saved more than one life.

But D.I. Ivanovsky is considered the official "father" of viruses. This Russian scientist studied diseases of tobacco plants for a long time and made an assumption about small microorganisms that pass through all known filters and cannot exist on their own.

A few years later, the Frenchman Louis Pasteur, in the process of fighting rabies, identified its pathogens and introduced the term "viruses". An interesting fact is that the microscopes of the late nineteenth century could not show viruses to scientists, so all assumptions were made regarding invisible microorganisms.

Development of virology

The middle of the last century gave a powerful impetus to the development of virology. For example, the invented electron microscope finally made it possible to see viruses and classify them.

In the fifties of the twentieth century, a polio vaccine was invented, which became a salvation from this terrible disease for millions of children around the world. In addition, scientists have learned to grow human cells in a special environment, which has led to the possibility of studying human viruses in the laboratory. At the moment, about one and a half thousand viruses have already been described, although fifty years ago only two hundred such microorganisms were known.

Properties of viruses

Viruses have a number of properties that distinguish them from other microorganisms:

• Very small sizes, measured in nanometers. Large human viruses, such as smallpox, are three hundred nanometers in size (that's only 0.3 millimeters).
• Every living organism on the planet contains two types of nucleic acids, while viruses have only one.
• Microorganisms cannot grow.
• Viruses reproduce only in the living cell of the host.
• Existence occurs only inside the cell; outside of it, the microorganism cannot show signs of vital activity.

Virus Shapes

To date, scientists can confidently declare two forms of this microorganism:

• extracellular - virion;
• intracellular - virus.

Outside the cell, the virion is in a "sleeping" state, it will not show any signs of life. Once in the human body, it finds a suitable cell and, only having penetrated into it, it begins to actively multiply, turning into a virus.

The structure of the virus

Almost all viruses, despite the fact that they are quite diverse, have the same type of structure:

• nucleic acids that make up the genome;
• protein shell (capsid);
• some microorganisms also have a membrane coating on top of the shell.

Scientists believe that this simplicity of structure allows viruses to survive and adapt in changing conditions.

Currently, virologists distinguish seven classes of microorganisms:

• 1 - consist of double-stranded DNA;
• 2 - contain single-stranded DNA;
• 3 - viruses copying their RNA;
• 4 and 5 - contain single-stranded RNA;
• 6 - transform RNA into DNA;
• 7 - transform double-stranded DNA through RNA.

Despite the fact that the classification of viruses and their study have stepped far forward, scientists admit the possibility of the emergence of new types of microorganisms that differ from all those already listed above.

Types of viral infection

The interaction of viruses with a living cell and the way out of it determines the type of infection:

• lytic

In the process of infection, all viruses simultaneously leave the cell, and as a result, it dies. In the future, viruses "settle" in new cells and continue to destroy them.

• persistent

Viruses leave the host cell gradually, they begin to infect new cells. But the former continues its vital activity and "gives birth" to more and more new viruses.

• Latent

The virus is embedded in the cell itself, in the process of its division, it is transmitted to other cells and spreads throughout the body. Viruses can remain in this state for quite a long time. Under the necessary set of circumstances, they begin to actively multiply and the infection proceeds according to the types already listed above.

Russia: where are viruses studied?

In our country, viruses have been studied for quite a long time, and it is Russian specialists who are leading in this area. The D.I. Ivanovsky Research Institute of Virology is located in Moscow, whose specialists make a significant contribution to the development of science. Research laboratories operate on the basis of the research institute, a consulting center and a department of virology are maintained.

In parallel, Russian virologists are working with WHO and expanding their collection of virus strains. Research Institute specialists work in all areas of virology:

• general:
• private;
• molecular.

It should be noted that in recent years there has been a tendency to unite the efforts of virologists around the world. Such joint work is more effective and allows serious progress in the study of the issue.

Viruses (biology as a science has confirmed this) are microorganisms that accompany all life on the planet throughout their existence. Therefore, their study is so important for the survival of many species on the planet, including humans, who have become victims of various epidemics caused by viruses more than once in history.