6 topics with concise breakdowns: definitions, key facts, and class questions.
This section focuses on viruses capable of causing malignant cell transformation. Here we analyze the general mechanisms of viral carcinogenesis, the integration of the viral genome into the host DNA, and the blockade of cellular tumor suppressor genes.
The materials provide a detailed description of both RNA-containing (human T-lymphotropic viruses, hepatitis G virus) and DNA-containing oncogenic viruses. Special emphasis is placed on pathogens with proven clinical significance—human papillomavirus (HPV) and polyomaviruses.
In practical classes and exams, instructors most frequently ask about the classification of oncoviruses, the mechanisms of action of viral oncoproteins (e.g., E6 and E7 in HPV), and the role of high-oncogenic strains in the development of cervical cancer. Knowledge of these topics is an absolute must-have not only for passing exams successfully, but also for understanding the infectious nature of tumors in future practice.
To which family and genus is the hepatitis G virus provisionally assigned?
It is classified within the Flaviviridae family and the Hepacivirus genus.
What is the essence of Zilber's viral-genetic theory?
The essence of the theory is that to trigger malignant transformation, the viral genome must necessarily integrate into the host cell DNA and closely interact with it.
What are the similarities between HTLV and HIV?
Both viruses affect cells of the human immune system, share common routes of transmission (bloodborne, sexual, and mother-to-child), and are characterized by a prolonged period of latent carriage.
Why does malignant transformation occur specifically in non-permissive cells?
In non-permissive cells, the virus is physically incapable of completing the replication cycle and assembling new virions. Therefore, classic cell lysis (destruction) does not occur, and early viral genes manage to trigger the transformation process of the surviving cell.
Why cannot the virus replicate fully in the basal layer?
Productive infection is only possible in differentiated stratified squamous epithelial cells. Cells of the basal layer divide actively, but do not provide the conditions for the complete viral reproductive cycle.
Is the SV-40 virus capable of causing oncological diseases in humans?
No. Although SV-40 causes tumors in certain rodents and monkeys, it has no oncogenic effect in humans. This was convincingly proven after millions of people were accidentally administered SV-40-contaminated polio vaccines—no increase in cancer incidence followed.
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