Human herpes virus 6 (HHV-6) was first isolated in 1986 from people with AIDS. It has since been found to be relatively common in the population as a whole, although people with HIV are more frequently infected. One study found HHV-6 in all the body tissues that were studied from nine randomly selected people with HIV at autopsy.

HHV-6 infects T-lymphocytes. The only disease that has been conclusively linked to HHV-6 is Exanthem subitum, a feverish illness of children. In immunosuppressed people it is a possible cause of pneumonitis.

Some researchers have suggested that HHV-6 could contribute to the loss of CD4 T-cells in people with HIV, since HHV-6 can activate HIV in latently infected cells and stimulates the release of cytokines that in turn also activate HIV. It also stimulates CD8 T-cells and natural killer cells to express the CD4 receptor, rendering them vulnerable to infection by HIV. One study found high levels of actively reproducing HHV-6 in the lymph nodes of all ten HIV-positive studied, including those with very high CD4 cell counts.

Some researchers have suggested that infection with both HIV and HHV-6 make retinal cells in the eye particularly susceptible to opportunistic infections such as CMV.

Other researchers have reported that active HHV-6 can be found in the brains of people with AIDS, where it may destroy myelin (the sheath surrounding nerves) and cause dementia.

Research

Knox (1994) detected HHV-6 in all lung, lymph node, spleen, liver and kidney tissues obtained at necropsy from an unselected series of nine people with AIDS. This infection rate was significantly higher than that for CMV. In one person lung infection was extensive enough to account for fatal pneumonitis.

References

Knox KK et al. Disseminated active HHV-6 infections in patients with AIDS. Lancet 343: 577-578, 1994.

Knox KK et al. Active HHV-6 infection in the lymph nodes of HIV infected pateints: in vitro evidence that HHV-6 can break HIV latency. J Acquir Immune Defic Syndr Hum Retrovirol 11: 370-378, 1996.

Lusso P et al. Commentary: Human herpesvirus 6 in AIDS. Lancet 343: 555-556, 1994.

Oavi H et al. Implication of HIV-1 and HHV-6 in the development of AIDS retinitis. Tenth International AIDS Conference, Yokohama, abstract 333B, 1994.