What's new in human herpesvirus-6? Clinical immunopathology of the HHV-6 infection.

Human herpesvirus-6 (HHV-6), formerly known as human B-lymphotropic virus (HBLV), was first isolated in 1986 from patients with lymphoproliferative disorders and AIDS. Antibody prevalence against HHV-6 varies between about 60-80% indicating a widespread latent infection. Although HHV-6 infects in vivo primarily T-lymphocytes, it is associated with similar diseases as in infection with Epstein-Barr virus (EBV), a clearly B-lymphotropic virus. Reactivation of latent HHV-6 infection in patients with subnormal host defense may cause persistent active infection with so-called postinfectious chronic fatigue syndrome (PICFS) or may contribute to other pathologies such as immune deficiency itself, autoimmune disorders or progressive lymphoproliferation. Coinfection of CD4 cells by HHV-6 and human immunodeficiency virus (HIV 1) in AIDS patients can aggravate HIV-induced acquired immune deficiency. These characteristics of the only recently detected new virus justify further intense investigation.