ABSTRACT
Human herpes viruses HHV-6 and HHV-7 belong to the Roseolaviridae genus of the beta herpesvirus subfamily and were discovered in 1986 [1] and 1990 [2], respectively. Prior to the isolation of HHV-6, the last human herpesvirus reported was EBV in 1966. However, after the documentation of HHV-6, within four years HHV-7 [2] and HHV-8 [3] were discovered. Initially, HHV-6 was designated ‘‘HBLV,’’ because it was isolated from peripheral blood mononuclear cells (PBMCS) from patients with AIDS and other lymphoproliferative disorders. Later on, the designation was changed to HHV-6 [4] to conform to the rules of the International Committee on Taxonomy of Viruses. After the initial isolation of HHV-6 at the National Institutes of Health (NIH), two independent isolates were reported-one known as U1102 from Uganda [5], and the other, called Z-29 by the CDC, from Zambia [6]. HHV-7 was initially isolated from CD4þ T cells of a healthy donor at NIH [2], the second independent isolate of HHV-7 was identified at NIH in the PBMC
of a chronic fatigue syndrome patient [7]. HHV-8, also known as Kaposi’s sarcoma-associated herpesvirus (KSHV), was discovered by Chang et al. [3] using representational difference analysis. By using this unique molecular approach, herpes viral DNA sequences were detected in lesions from AIDS patients with Kaposi’s sarcoma. KSHV (or HHV-8) is a member of the genus Rhadinoviridae within the human gamma herpesvirus subfamily. HHV-8 is also called a gamma-2 human herpesvirus [8].
