Lev Zilber

Picture of Lev Zilber

Date of Birth: 03/27/1894

Age: 72

Citizenship: Russia


Lev Alexandrovich Zilber life (1894-1966) spanned by far the most tragic period in the history of Russia, including the events of the Russian-Japanese War, the 1905 Revolution, the two revolutions of 1917, two world wars and civil wars, Stalin`s terror 30 50 years, the Gulag, the session of Agricultural Sciences (1948), Pavlovian session (1950), "doctors` Plot" (1952), rampant anti-Semitism, the fight against cosmopolitanism. Only two short periods of his life can be considered relatively normal: before 1917 and after 1953, and between these dates was seven and a half years in prisons and camps.

Our sketch of the tragic (and happy!) Fate of the scientist, we begin with a brief description of his personality, because it will allow a much better understanding of his artistic career. Decade daily communication with L.A.Zilberom give us that right.

Lev was a kind of passionate, given to any business, any idea that it captures a whole, without a trace, with incredible energy, pressure, impatience and fury. In his life there was nothing that he would do out of duty, for service, half, somehow. He had a favorite expression is not very correct from the point of view of normative grammar, but it is very typical for him: "What should be." This could relate to and experience that should be delivered "as it should be", and running water in the country, which he did, "as it should be," and the whole surrounding.

It would seem that passion of nature and irrepressible vitality would have to rise to haste, haste, unwillingness to deal with one and the same for a long time. In fact, Silber had a rare patience and persistence in achieving goals, though it took years. For the last 20 years of his life had gone to search for evidence of a flawless theory developed by him virusogeneticheskoy of tumors.

Lev set himself goals that have never been private, narrow, minor, he was never interested in the "final sewing buttons on his uniform crosslinked" (Zilber expression). It attracted the goals that were either just not visible to others, or seemed unattainable. This maximalism, unwillingness to work in the existing fields of science, a sharp departure from one area to another and invasion, which looked at first irrational, followed indeed the internal logic, which were leading the romance of the unknown, the resistance of the material, the difficulty of achieving a result.

When in microbiology and bacteriology he left, he then believed sverhtrudnyh tasks, he left in virology, which while current science simply did not have, and that is what attracted him. When infectious medical virology as a science has gained shape, it has become uninteresting for Zilber, and he began to build a non-infectious onkovirusologiyu. Changing direction is not in a science, and science itself, he carried throughout his life a constant attachment to immunology. From the first steps in science under the guidance V.A.Barykina * and until recent years, when he was working on a vaccine against cancer, his fascination with the problems did not weaken immunity and immunological methods he used all his life. We think that this is not accidental. Immunology - one of the most complex areas of biology and medicine, which is the whole XX century. It remained the focus of attention of researchers. Of course, immunology - one of the most, if I may say so, biological sciences, among many of the life sciences, the border with medicine, and if we use modern terminology, that biomedicine has been the core of the entire scientific life Zilber, who had two complete higher education - natural sciences ( Petersburg State University) and health (Moscow University). It is interesting that he was born in a family of musicians, where he had not been a single man of science, and his father strongly objected to his admission to the university, because he wanted to make sure to son skripacha.Virusologicheskie interests Zilber literally grew out of his work in microbiology, as and the bacteria and viruses coexisting in higher organisms, were, according to Lev Alexandrovich, interact, and this interaction could be a symbiotic and antagonistic. Experiments began with the study of the adsorption of virus smallpox vaccine in vitro on yeast cells (with E.Vostruhovoy and later with A. Belyaev). It was proved that live yeast cells are capable of adsorbing significant quantities of vaccinia virus. Zilber staff observed a similar phenomenon in the experiments with other viruses, and found that, in addition to yeast, certain bacteria and protozoa (single-celled eukaryotes) can also adsorb viruses.

All these data have led to the concept of Lev Alexandrovich, postulated symbiosis of viruses and germs. It is named viroforii, and in a broader sense - allobioforii (Zilber term). Lev stressed that this phenomenon has not only general biological but also of great practical importance, because it can seriously impact on the epidemiology of some viral infections [1]. He believed that in some cases the virus enters the cells of microorganisms and multiplies them, because experience suggests such a possibility. These views Zilber so ahead of their time, that were long out of sight of contemporary researchers.

The development of domestic virology, especially medical, it has been strongly stimulated by the All-Union meeting on ultravirusov (1935). The meeting Zilber made a keynote, where the role of viruses seen in the broader theoretical and practical terms - in biology, medicine and agriculture. Strikingly, but in this report it is quite clearly formulated the term virologic approach to the problem of the origin of tumors. Moreover, it mentioned the possibility of the existence of foreign antigens in tumors as the presence of oncogenic viruses markers. The report certainly suggests that when entering the virology Zilber already worried about the problem of virology and immunology of cancer.

At the same time it creates a viral lab Central People`s Commissariat of the RSFSR. The laboratory is the first independent virological institution of our country, whose forced a brief (1934-1937) and brilliant existence forever remain in the history of Russian science. The Institute of Microbiology, Academy of Sciences of the USSR Lev organizes the Virology Department. Characteristically, Silber always aspired to harmonious development and virology as part of biology, and as a part of medicine. In the laboratory, the emphasis was on the medical aspects of virology, and in the department - on the general biological. This approach laid Zilber, still preserved in the national virology, in the works of famous works virusologov.V Central Laboratory of Viral clearly manifested integral approach scientist to virological problems: we study not just viruses (especially influenza), but immunity to it . in immunology Extensive knowledge Zilber find here a new application to the extremely poorly known objects. The most important task of the first virological institutions in the country has been training. Lev has always preferred to work with young people, full of enthusiasm and able to easily accept new ideas and methods. Laboratory consisted of very young people, and their leaders were executed only 40 years old. The turning point in the history of the domestic medical virology and in the fate of most of the staff of the Central Laboratory of the virus, the triumph and tragedy of its head Lev Alexandrovich Zilber became legendary expedition to the Far East in 1937 GS beginning of the 30s in some areas of the Far East, the doctors found severe acute disease often results in the death of patients, as affects the central nervous system. The disease has not been studied and classified by local doctors as "toxic flu". In 1935 A.G.Panov doctor, who worked in the Far East for the first time found that the disease - encephalitis; he believed it had already known at the time of Japanese encephalitis. In 1936, the Far Eastern doctors Pasteur station, was administered to mice in the brain marrow emulsion died of encephalitis people tried to identify the pathogen, but the attempt was not successful. It became clear that local doctors can not cope with the disease and need help from the center.

Many years later Zilber recalled: "When the People`s Commissariat of the time formed the expedition, he wanted to make a complex group, which was to be 10 professors I resolutely refused to participate in such an expedition and said something to one - or I take. all responsibility and form an expedition, or arrange as you see fit. After a big conversation turned me down. but the military-sanitary management was vitally interested in the struggle against encephalitis. Remember that time - it was a period not only of a wide economic development of the Far East, but also the time when we were forced to keep it large military units that were directly in the forest. Therefore, the Military Medical Administration has asked the People`s Commissar of defense, and his direct orders I edinonachalno led an expedition. I could choose in this expedition anyone and work as we considered it necessary I took only the young, and did so quite consciously of course, I gathered them and warned of the dangers and difficulties and everything else..; young people were in my eyes, a huge advantage - they were not bound by the old misconceptions about this disease. Before our local neurologists argued that this disease is a Japanese summer encephalitis, and even in our official documents, when we went to the Far East, and has been written - that we are going to study summer encephalitis. I was not convinced of this, and we have made three scientific plan. The first plan for the case, if it is really summer encephalitis, the second plan - if it is any other encephalitis. And finally, the third plan - in case this is not encephalitis. These plans have been worked out in detail. From the beginning I planted parallelism in this work. It was delivered in a way that my employees were divided into two groups, which did the same thing to be sure of a result, and in order to reduce the time of research. This system is in the course of specific conditions, when it was necessary to solve the problem very quickly, fully justified itself "[2, p. 48].

Further it is written immediately after the expedition. "At the first road May 19, 1937 with a group of employees in the taiga in the northern area of diseases, I was faced with the facts that led me to question the existing concept of the epidemiology of the disease. In a small bolnichke located in the forest timber industry I have found in recent history three years. Their view showed that encephalitis suffer mostly in the spring and only the people who work in the forest, and often do not have any contact with each other. this data is not aligned with the theory of contact or droplet infection. The same taiga bolnichke May 19, I found the patient encephalitis, which is ill may 4 and is already recovering by the time of my visit. She was the first patient of this season, and the establishment of the source of her infection could be crucial for future studies. The patient was a housewife, did not go anywhere for two years from the taiga settlement, where she lived, and which did not have any contact with patients or with their families. For a long time failed to establish a s at least some probability of the origin of this disease. It refuted the theory and contact, and the summer season, and the assumption of the possibility of transfer of disease by mosquitoes, as there are no mosquitoes at this time was not in the area. After a long questioning the patient remembered that for 10-14 days before the disease she collected in the forest last year`s pine nuts and, after returning home, found at glaring mites. This single fact which could link her illness, of course, caught my attention, "[3, pp. 125, 126]." I flew to Vladivostok to learn a little bit about chto-to ticks (I knew nothing about them then) ... It helped me, but only in literature, and I found in the work of one veterinarian curve bite cattle ticks, which perfectly matches the curve of increase of the disease in people, but with a delay of two weeks; it is clear that it was the incubation period "[4, p. 162]." The probability of transfer of the disease in this way for me was so obvious, that at the end of May, I sent a number of doctors, including employees of the expedition in the taiga to the parties of persons working exclusively in the forest, to instruct them about the dangers of tick bites. Later it turned out that these people fell ill in 1937, only one person, but in previous years it was the most stricken group. Together with the collection of epidemiological data has been organized and experimental verification of the theory tick. Relevant experiences entrusted me Mikhail Chumakov, crowned with complete success, and it has been experimentally proved the possibility of transmission of disease ticks. These and all subsequent work, especially following extensive research of Academician E.N.Pavlovskogo and his staff, fully confirmed the theory put forward by me on the transfer of disease ticks "[5, p. 9].

Tick-borne theory advanced by Zilber, justified his colleagues and himself, strikes us even 65 years after these events, many associated with her circumstances. The idea appeared May 19, 1937 - two days (!) After the start of direct work in the outbreak of the disease, and only after 20 (!) Days, "I took the responsibility - says Silber - offer at a specially convened meeting of June 10 local health authorities to radically change all the measures to combat these diseases, focusing on prevention protivokleschevoy "[2, p. 126]. Only someone with a combination of many qualities - scientific intuition, determination, action, a sense of responsibility, speed of thought, inner conviction, humanity - could in such a fantastic time frame to go from a scientific hypothesis that has arisen out of nowhere, to vigorous practical measures to rescue people taiga. Of course, here fully manifested style and character Zilber, always prone to "rapid" generalizations. However, it would be wrong and naive to think that one patient, one revelation, one guess is ensured the success of the expedition. Sam Lev thought that a huge role in the scientific search plays preparation research. When I think about the role played by the preparation of studies, I always remember our expedition in 1937 "[2, p. 51]. All of the most perfect machine to the last stud, was provided with the equipment of the expedition, lacking only tropical monkeys . And from Japan to meet the expedition were sent urgently purchased monkeys. They were needed for crucial experiments.

Tick-borne theory answered the question of the carriers of the disease and how it spreads, so that she had, in addition to the theoretical, of great practical importance. Of course, she did not answer the question about the nature of the causative agent: mites, in principle, could carry and bacteria and rickettsiae, and viruses. Only carefully designed experiments (it is worth mentioning that it is a wild taiga, impassable roads, wooden huts, rather than on the sterile "boxes" and "kelp"!) Could give an answer to this question. Adhering to historical accuracy, give the floor to the original source: "... the first fatal cases of the disease were given material, by which almost simultaneously and me Shubladze Lewkowicz in the south and the north and Chumakov was isolated the causative agent, who turned ultravirusom having some similarity to Japanese viruses American and encephalitis. a little later these same strains were isolated Solovyov. In June and July 1937 me and put Shubladze infection experiments the monkeys died from brain emulsion encephalitis people and received by the time of passage virus. These tests also confirmed the etiological significance of strains isolated by us but the neutralization of these strains by sera of convalescents, that is, people who have had encephalitis, a long time we did not go that precluded the recognition of isolated virus causative agent of the disease. Only after both experiments were collected serum later periods of convalescence, we received a distinct positive results and it became clear that in our hands is the causative agent of the disease "[2, p. 127].

And now we present an assessment of the expedition "from outside". "Actually, all of the work on the study of the taiga encephalitis was a feat of our scientists. The feat has become, as it were their daily way of life. But I want to say too much about some of extraordinary episodes reminiscent of the heroism of the soldiers on the battlefield. Somehow in the midst of the work we began heavy rains. The raging river broke the dam. Water penetrated into the vivarium - the room where the animals were. It was necessary to save them in that whatever the cost, to save everyone. Scientists announced Abraham. Working on the waist in the water, they are pushed to the cell with the land frightened mice and monkeys. The animals were saved. Soon ill Dr Chumakov. Despite the severe muscle pain and weakness, he continued to work. But temperatupa crept up. There were the first signs of brain disease. Chumakov came down. Fellows swept anxiety, but he reassured them. "Nonsense, cost - he said -. It woke up my old rheumatism." However, it was not so: he was infected with encephalitis. Chumakov bravely looked in danger of the eyes and asked his comrades only one thing - to bring their common cause to end "[6, p. 12,13]. The great strength of mind and will allow Mikhail Chumakov resist the terrible disease. Another member of the expedition V.D.Solovev also suffered encephalitis, fortunately, a milder form.

It is useful to cite the opinion of one of the leaders of the second expedition to the Far East (1938) A.A.Smorodintseva, subsequently leading virologist, academician of AMS USSR (as it relates to 1984): "I must say that a suitable candidate, of course, the L. A.Zilber to solve such a complex problem, at that time it was impossible to choose "; "Lev Zilber literally went to the unknown and brilliantly proved the viral nature of the causative agent of tick-borne encephalitis" [7, p. 18]. These evidences are of particular value as Smorodintsev not only well aware of all the related with the expedition in 1937 the circumstances, but did not agree with Zilber on many issues of general virology, which they openly debated in the postwar years.

Zilber with his usual laconic summarized the expedition: "To work on the site of the expedition on August 15 [1937] was completed within three months, we have established the existence of a new, previously unknown forms of encephalitis, isolated 29 strains of pathogen it is installed epidemiology of the disease. and its transporter mainly studied clinical, pathological anatomy and histology of the disease. This success was overshadowed by the laboratory infestations employees ... it is difficult to establish the circumstances under which they were infected. All the usual preventive measures when working with infectious material carefully carried out by all employees. the most dangerous experiments with a nasal infection of monkeys have been carried out by me with the help of Shubladze. You can not be assumed that the virus has a special extraordinary kakoy-to infectivity. in the end we were the pioneers in this field, we were the first people in the world who were holding this unknown before the virus. it is possible that a certain value were relatively primitive conditions in which the work was done, and a great fatigue of daily work 12 hours or more for three months only for this time holiday. But I could not keep my staff on this hard work: they all worked with exceptional passion and genuine enthusiasm. In subsequent years, fatal infections have been working with our virus in Moscow in special virology laboratories that took specially designed measures to prevent infections. These facts compel us to think about our unusually high infectivity of the virus, and it is not surprising that the first encounter with him was not without casualties. They could be much more significant, "[3, p.128].

It would seem that people for three months literally risked his life every hour, can count at least on gratitude for what they had done. However, it was in 1937, and a monstrous, absurd and blasphemous denunciation arrested expedition leader and two of his closest collaborators and A.D.Sheboldaevu T.M.Safonovu. In the absence of the arrested and without their names being published the first scientific report about the etiology of encephalitis. Several participants zilberovskoy expedition, as well as leaders and members of the second and third expeditions of 1938 and 1939. (E.N.Pavlovsky, A.A.Smorodintsev, P.A.Petrischeva) were awarded the Stalin Prize of 1st degree. Among the winners there L.A.Zilbera, A.D.Sheboldae howl T.M.Safonovoy.

About the period from 1937 to 1939 Lev almost never spoke, but sometimes referred to Lefortovo, Lubyanka, Butyrka, Sukhanovo - for hundreds of thousands of our citizens these names meant prison monstrous physical and mental suffering, almost inevitable death. Zilber went through it all, not signing the recognition of non-existent crimes. Many years later, he was at the annual medical examination, and a young female doctor looking at a picture of his chest, exclaimed: "You have broken ribs as A is not written about it in the card!". "Yes, - said Silber - before the war, I was in a terrible car accident." He was very pleased with how cleverly held a trusting young woman.

In 1939, Silber was released. We can not say now, that was decisive in this release: the absurdity of whether the charges vigorously if and fearless action devoted friends or "shift change" in the NKVD, where instead of the bloody executioner Yezhov came a new executioner - Beria, who began his work with the release of a very small part prisoners. Upon his release, Silber publishes classical, fundamental work on tick-borne encephalitis [5], written on the heels of another expedition in 1937, wrote a monograph on encephalitis, leases it to the publisher in December 1939 Book recruited, due out in next year, but in 1940, followed by a second arrest. Luckily, the one instance of this knigi.Bylo would be extremely surprising, one might even say, "normal", if such a bright personality, as Leon Zilber, would stay while at liberty. Strikingly different - he survived, survived, preserved intellect and will to the life and scientific work. We think that Zilber saved by the fact that he did not sign a confession of his "guilt", despite the torture, and his friends, in spite of the terror of the NKVD, were not afraid to declare in writing his complete innocence. Of course, they have committed a civil feat, if we remember that it was a time of war, and Zilber accused neither more nor less, as in "high treason". Therefore, salvation Zilber, his return to freedom - not the result of "restoration of the truth", "recognition errors" those who tormented him and kept behind bars, and the final result of his courage, will-power, on the one hand, and the friendly, professional solidarity - with other. It was not a gift of fate, but the outcome of the fight a few people with the Stalinist machine of death. In this, perhaps, the chief moral lesson Zilber life has intrinsic, absolute value.

The question may arise: why, talking about the opening of a carrier of the virus and tick-borne encephalitis, we used extensive quotes from the works Zilber? The reason is simple: the story of this discovery long distorted beyond recognition, and therefore we feel obliged to interesahnauchnoy truth refer to "indications" of the main participant in the events.

In school textbooks 1950-1970-ies in biology discovery carrier encephalitis associated only with the name E.N.Pavlovskogo, Zilber surname was not mentioned at all, although the names of some members of the first expedition (Chumakov, E.N.Levkovich, The .D.Solovev, A.K.Shubladze) in some places appeared. Not in any way detracting from the value of the expedition 1938 and 1939., It should be emphasized that the honor of the discovery of the virus as a new, independent units posology and honor carrier detect virus - mite, completely owned by members of the expedition in 1937 Subsequent expeditions have fully confirmed the results, supplemented them, detailed, deepened, but in no way denied. This is the historical truth.

Why do we think the expedition in 1937 led by Zilber milestone in the history of Russian virology?

Firstly, after the discovery of tobacco mosaic virus D.I.Ivanovskim, laid the foundation of virology as a science, and to the shame of Russia at that time, and the Nobel committee not marked the Nobel Prize, the detection of the virus and vector borne encephalitis was most striking achievement of the national virology. Neither before nor after did not, unfortunately, as the undisputed and significant for their scientific and practical implications of discoveries in the history of the Russian Virology.

Secondly, the expedition had a decisive influence on the formation of the national school of Medical Virology, its rapid formation and development. Recall that the members of the first expedition - Chumakov, A.K.Shubladze, E.N.Levkovich, V.D.Solovev - became leading virologists country that created later their research areas, have prepared their students. Medical Virology in the USSR after the 1937 expedition, she received a powerful impetus to the development, there was a network of virological institutions are now playing an important role in the national virology.

Third, follow-up study of both the Lev Alexandrovich and his students, and other researchers have shown that the tick-borne encephalitis is not endemic to the Far East, and is far more widespread - not only in Siberia, but also in Europe - wherever found in nature ticks. Therefore, achieving members of the expedition in 1937 are far beyond the primary tumor diseases, where early results have been received, and have a much wider geographical significance. So now, of course, should drop the name "Far East spring-summer encephalitis," continue to use the name "encephalitis", emphasizing its important features - the nature of the carrier.

Fourth, the story of the first expedition, perhaps unique in how negligible was the interval between research and direct access in practice. Long before the end of the expedition (although three months for such complex work - a very short time) practical recommendations for combating mites led to a sharp drop in the incidence of not only the population but also military, in 1937-1939. saved thousands of lives.

Expedition 1937 - a textbook example of the effectiveness of basic science as a means to solve practical problems of the country.

While in detention (1937-1939, 1940-1944), Silber of the term served in the Pechora camps. Here, under the tundra, he created a drug against pellagra and saved the lives of hundreds of prisoners who were dying from full beriberi (they even received an inventor`s certificate - and this in inhuman conditions to enter into the camp!). During his second imprisonment, he worked in the so-called sharashka - NKVD closed institution in which the arrested scientists worked under the constant and vigilant control. Nevertheless, the work "sharashka" was an outlet that allowed at least partially return to science, without which the Lev could not exist. As he later wrote, "the circumstances are such that I have had plenty of time to think." Indeed, the work "sharashka" has provided this opportunity, there is not called in for questioning, not tortured.

The culmination of the epic taiga can be considered the publication in 1946 of the monograph Zilber, written six years earlier. It not only sums up the experience of studying tick-borne encephalitis, but also considers the problem of epidemic encephalitis in general. This monograph was awarded in 1946 the Stalin Prize of 2nd degree. In the same year, achieving the national virology to study tick-borne encephalitis are known to English-speaking readers: great review published Zilber, written jointly with V.D.Solovevym.

Back in his laboratory at the Central Institute of Epidemiology and Microbiology (now the Institute of Epidemiology and Microbiology. Gamalei RAMS), Lev poopolzhil vipusologicheskie research, in particular, on the western encephalitis, influenza, antiviral immunity, but the focus of his research interests is clearly shifts to onkovirusologii.

Zilber Why, when life became a classic infectious (epidemic) Virology, created the first and best school in the country of Medical Virology, after his release from prison in March 1944, does not return to the area where he was waiting for an easy life Reapers deserved laurels and "clipping coupons "with an outstanding opening? It seems to us that there were several reasons. Vo-pervyh, more than seven years in prisons and camps, following the success of the expedition of 1937, and then a blatant falsification of the history of discovery of tick-borne encephalitis, which up to 1953 no one in no hurry to fix it, could not but cause serious injury, even a moral to this courageous man, how Zilber.

Second, paradoxically, tick-borne encephalitis was not in the plans of the Central Laboratory of the virus, a problem has arisen in response to the urgent need for practical medicine and the military. It does not fit into the strategic plans Zilber, he laid them on virology meeting in 1935 Taiga saga in this sense, was a manifestation of excitement researcher thirst struggle with uncertainty and danger, and looked like the suppression of the plague outbreak in Nagorno-Karabakh in 1930, which Silber brilliantly realized and then spoke about this with his usual skill. In addition, the tick-borne encephalitis was basically defeated (to avoid ticks!), And to engage in detailed Lev did not want it, he was just not interested.

Third, the prison experience, which we describe below, have further strengthened his confidence in the fact that viruses and cancer - concepts compatible and amenable to experimental attack. As we already mentioned, in 1935 Silber in the report at the meeting of virologists talking about viral theory of cancer origin.

Considering all these factors, taken together, care onkovirusologiyu tumor immunology, and it seems logical to Zilber: Region did not developed, the difficulties seem insurmountable, the scientific community skeptical - is not repelled and attracted by the Lion Aleksandrovicha.Nelzya say that Zilber was the first who expressed the idea of ??viruses as an etiological factor in the occurrence of neoplasia. By that time, were isolated viruses that can cause tumors in animals and birds - chickens sarcoma virus (P.Raus, 1911), rabbit papilloma virus (R.Shoup, 1932), the virus tumors of the mammary glands of mice (Dzh.Bitner, 1936) [ eleven]. Naturally, in those years, experiments were conducted only in experimental animals, tissue culture method and the cells appeared 15 years later. But where to get the animals in the prison? Lev quickly finds a way out. He agrees with the prisoners, and they begin to catch him in mice and rats, which in "sharashka" enough, and paying the price for this work in tobacco, to issue conclusions.

In the early 1940s, it was known that tumors in experimental animals can cause processing carcinogens, several viruses and implanting them live tumor cells. What is taking Silber? It causes tumor carcinogenic in rodents, and then using the cell-free extracts of these tumors that is disrupted cells, passed through a Seitz filter, tries to cause tumors in adult mice. These experiments (except for two) were negative, whereas the cell homogenates are not passed through a Seitz filter, retain the ability to form tumors.

However, the two cases have drawn attention Zilber. In one - in the dead by accident (and not as a result of the tumor process) rats, which were inoculated with cell-free extracts, found a small tumor nodule ( "young" tumor). The extract of the tumor, in turn, induce tumor in another recipient animal. In the second case, a possible viral agent was also present in the "youngest" of the tumor. All this led Zilber suggests that the virus may be present only in tumors at early stages ( "young"). Thus, the virus launches a neoplastic process, and subsequently a tumor cell in the virus does not need. Lev pro