Human herpes virus 8

KS is caused by a herpes virus. The virus was first named Kaposi's sarcoma-associated herpes virus (KSHV) but is now usually known as human herpes virus 8 (HHV-8).

HHV-8's genetic material was discovered in KS lesions in late 1994. In March 1996, researchers in San Francisco successfully grew the virus in culture. The virus is a close relative of Epstein-Barr virus, which has been proposed as the cause of non-Hodgkin's lymphoma. Recent studies have confirmed that HHV-8 can almost always be found in KS lesions, including non-HIV-related KS, but is very rare in other body tissues. Nine studies in which samples from 224 KS lesions were examined found that HHV-8's genetic material could be identified in 97% of them. Other types of human tissue rarely contain HHV-8, although it has been isolated from some AIDS-related B-cell lymphomas.

The reason why some people infected with both HIV and HHV-8 develop KS, while others do not, appears to be linked to HHV-8 rather than CD4 cell count. A study found that the presence of HHV-8 genetic material in both blood cells and saliva was associated with KS, while people with HHV-8 only in saliva were much less likely to have KS lesions.1

Scientists have uncovered a number of different ways in which HHV-8's genes, alone or combined with HIV, and possibly other undiscovered factors, may trigger abnormal blood vessel growth. Kaposi's sarcoma is caused by a complex process of HHV-8 infection, the production of inflammatory cytokines and the dysregulation of new blood vessel formation (angiogenesis). Drugs which suppress vessel formation, such as interferon alfa (IntronA / Roferon-A / Viraferon) and interferon beta (Avonex / Rebif / Betaferon), are being tested as treatments for KS.

A number of antibody tests for HHV-8 have been developed for research purposes, although these continue to lack sensitivity. A new generation of HHV-8 assays has been developed which may improve understanding of HHV-8 and lead to clinical use of HHV-8 testing.

References

  1. Cannon MJ et al. Risk factors for Kaposis sarcoma in men seropositive for both human herpes virus 8 and human immunodeficiency virus. AIDS 17: 215-222, 2003