DNA viruses and viral persistence

What core replication and expression features characterize most DNA viruses?

Most DNA viruses replicate their DNA genome inside the host cell nucleus and tightly regulate their own temporal gene expression. They frequently establish long-term persistent or latent infections.

What functional roles distinguish Immediate-Early/Early ($\alpha$/$\beta$/E) genes from Late ($\gamma$/L) genes in DNA viruses?

Immediate-Early and Early genes (e.g., HPV E1, E2, E6, E7) encode non-structural proteins required for gene regulation, host cell cycle modulation, DNA replication, and immune evasion. Late genes (e.g., HPV L1, L2) encode structural capsid proteins assembled after genome replication.

How is HPV gene expression coordinated with epithelial cell differentiation?

HPV infects basal epithelial cells where early genes (E1, E2, E6, E7) drive viral DNA replication and cellular proliferation. Structural late proteins (L1 and L2) are expressed strictly in upper, terminally differentiated epithelial layers prior to viral release.

What mechanisms allow persistent HPV to evade host immune surveillance in high-grade lesions?

1. E6 and E7 downregulate host cytokine and interferon production.

2. E5 reduces MHC Class I expression on the cell surface.

3. Production of highly immunogenic structural proteins (L1 and L2) is delayed until outer, shedding epithelial layers.