HHV-6 was isolated in 1986 from patients suffering form lymphoproliferative disorders and AIDS. The antibodies directed against HHV-6 indicate a previous viral infection in 80~90% of the general population. HHV-6 isolates have been divided into
two
distinct subgroups(subgroup A and B) based on restriction enzyme profiles, prevalence in the population, and their in vitro ability to grow in cultured cells. Subgroup A strain(strains GS and U1102) is correlated with lymphoproliferative
disorders.
HHV-6 has been proposed to be a co-factor in the progression of AIDS because HHV-6 and HIV 1 have been demonstrated to co-infect CD4+ human T cells and accelerate HIV-1 expression and cell death.
HHV-6 has also been associated with human several malignancies. The association between HHV-6 and human cancer might be strengthened if other fragments representing different regions of the genome with demonstrated transforming potential were
also
used
for these analyses. These associations have led to the analysis of genomic HHV-6 DNA and cloned restrictions fragments(Sal 1-L-SB, -SH, -BN, -BS, -HS, -HS) for their ability to transform cells in vitro. A 4. 1-kb Sall-L fragment which exhibited
transforming activity was identified. This fragment was retained in focal and tumor-derived cell lines. In addition, the Sal l-L fragment was shown to transactivate the HIV-1 LTR.
Initial experiments have co-localized both the transforming and transactivating activities to a 1. 9kb Sall-L-SH fragment and implicate a 283-aa ORF as the functional element. Moreover, the identification of a transforming and transactivating
region in
HHV-6 has strengthened the association of HHV-6 as a co-factor in AIDS and AIDS-related malignancies.
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