DNA Viruses (Parvoviruses, Papillomaviruses, Adenoviruses, Hepatitis B Virus, Herpesviruses, Poxviruses, Anelloviruses)
13 topics with concise reviews: definitions, key facts, and class questions.
Welcome to the DNA-containing viruses section. Unlike most RNA viruses, these pathogens (with rare exceptions) replicate in the host cell nucleus and feature high genome stability. Here we analyze the agents you are guaranteed to encounter in clinical practice.
The section covers key families: from tiny parvoviruses and oncogenic human papillomaviruses to massive poxviruses, including the currently relevant mpox virus. A special place is occupied by hepatitis B virus with its unique replication cycle, as well as the extensive herpesvirus family (herpes simplex virus, VZV, CMV, EBV, types 6–8), prone to lifelong latency. In addition, we will touch upon recently discovered and still poorly understood anelloviruses.
During tests and exams, professors traditionally drill students on hepatitis B serological markers, HPV and EBV oncogenesis mechanisms, and require a clear distinction between alpha-, beta-, and gamma-herpesviruses. Pay special attention to transmission routes, infection types (acute, chronic, persistent), and specific prophylaxis—this is the foundation for your future medical practice.
Unlike most DNA-containing viruses, their genome is represented by linear single-stranded DNA, which must be converted into a double-stranded form by host cellular enzymes.
Why is it impossible to culture HPV in laboratory conditions for diagnostics?
The virus does not replicate in standard cell cultures, as its replicative cycle strictly depends on the stages of natural maturation and differentiation of skin or mucosal epithelium.
Why is hepatitis B virus called reverse-transcribing?
During replication in the cytoplasm, viral DNA polymerase (reverse transcriptase) synthesizes a new DNA strand using the intermediate pregenomic RNA template.
Where is the herpesvirus supercapsid formed?
The supercapsid (outer envelope) is formed from the inner layer of the host cell nuclear membrane during nucleocapsid budding from the nucleus.
What main biological feature unites all alpha-herpesviruses?
They are characterized by a short replication cycle, which ensures their rapid growth and reproduction in infected tissues.
Why is herpes impossible to cure completely?
The virus transitions into a latent form in sensitive nerve ganglia. Its DNA persists in neuronal nuclei as free circular episomes (about 20 copies per cell), which are inaccessible to antibodies and unaffected by chemotherapeutic drugs.
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