Compare and contrast the oncogenic viruses human herpesvirus 4 (Epstein-Barr virus) and hepatitis B virus (HBV).

Question

What will be an ideal response?

Answer 1

HHV-4 infects B-lymphocytes and is primarily associated with lymphomas, although it is also associated with nasopharyngeal cancer. HBV infects hepatocytes and has been shown to be associated with hepatic cancer based on a large amount of evidence.

Both oncogenic viruses are DNA viruses with an envelope, and both can establish chronic infections. However, the chronic infection with HHV-4 is a latent infection, whereas chronic hepatitis B virus infections are productive. The DNA of both viruses can be detected in the nuclei of infected cells and may integrate into the host genome. Both infections appear to require cofactors for the development of cancer.

HHV-4 is a member of the herpesvirus family, a group of viruses known to be capable of integrating into the host genome. However, the high prevalence of the virus in the human population, coupled with the relative rarity of the associated cancers, suggests that additional factors are involved in triggering the development of cancer. The cofactors for HHV-4 oncogenicity have not been identified with certainty, but they may be environmental factors, such as exposure to malaria antigens.

The HBV genome has been shown to be capable of integration into the host genome. Viral integration often disrupts normal function or expression of the genes in the vicinity of the site of integration. Integration alone may be sufficient to trigger progression to cancer. However, the observation that not all chronic HBV infections result in hepatic cancer suggests that other factors may be involved or contribute to the development of cancer.