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Human herpesvirus 8 (HHV-8) is a recently discovered virus that is highly associated with Kaposi's sarcoma (KS) and AIDS-associated body cavity lymphomas, although it is also found in some normal individuals. HHV-8 is related by nucleotide sequence homology to herpesvirus saimiri (HVS), which causes T cell lymphomas in some New World monkeys, and to Epstein–Barr virus (EBV), a human herpesvirus linked etiologically with Burkitt's lymphoma and nasopharyngeal carcinoma. We report that, like HVS but unlike EBV, HHV-8 contains a gene (ORF74) with significant sequence homology to the high-affinity IL-8 receptor, a member of the α (CXC) chemokine receptor family of transmembrane G protein-coupled receptors. We also show by reverse transcription PCR that the chemokine receptor-related HHV-8 gene is detectable in some RNA samples from KS tissue, and that its expression varies independently from that of ORF26, a minor capsid protein. The presence of a potential chemokine receptor in HHV-8 and its expression in KS tissue suggests that it may be important in the regulation of viral gene expression and may play a role in the etiology of KS and AIDS-related body cavity lymphomas.

The envelope proteins of retroviruses are derived from a polypeptide precursor protein by cleavage adjacent to a cluster of basic amino acids. Site-specific mutagenesis was used to construct a mutant of the human immunodeficiency virus type 1 (HIV-1) in which the arginine residue at the carboxy-terminus of the gp120 was changed to a threonine residue. This single substitution was sufficient to abolish all detectable cleavage of the gp160 envelope precursor polypeptide as well as virus infectivity. The gpl60 was produced in normal quantities from a biologically active clone of the mutant virus after transfection into cos-1 cells. The mutant gp160 contained Winked oligosaccharide chains with mannose-rich cores similar to those of the gp160 produced by the wild-type clone. Immunofluorescence assays showed that gp160 was transported to the surface of transfected CD4+ HeLa cells. No envelope proteins of known size could be detected in the media of cells transfected with the mutant virus, suggesting that functional virions were not formed. Binding of the mutant gp160 to the CD4 receptor molecule was unimpaired. Despite this and the presence of gp160 on the cell surface, neither growth of mutant-transfected CD4+ HeLa cells nor cocultivation of transfected cos-1 cells with H9 cells resulted in significant syncytium formation. The data indicate that the carboxy-terminal arginine residue of HIV-1 gp120 is necessary for envelope protein cleavage and suggest cleavage is important in the virus life cycle in both functional virus release and membrane fusion.

One of the striking molecular aspects of the human T-cell lymphotropic virus type III (HTLV-III) (now called HIV-1) is an unusually large variability in the env genes of different isolates. These differences are clustered primarily within the coding sequences for the large envelope protein and are interspersed among regions within the env gene of relative constancy. Differences among the envelopes of isolated from Africa are so far greater than those among U.S. isolates, but few U.S. isolates have been characterized to date. We report the sequence of the env gene of two U.S. isolates [HTLV-III(MN) and (SC)] and compare them with previously characterized isolates. These two isolates differ substantially from all previously described isolates, especially in the region coding for the large envelope proteins. The env genes of the two new HIV-1 isolates contain conserved and hypervariable regions similar to what has been reported for other isolates, helping to further define those regions. A comparison of the envelope sequences of all the U.S. isolates shows that the similarity between any two ranges from 81 to 85% [except for LAV(BRU) and HTLV-III(BH10) which are 97% similar]. Similar analyses of the African (Zairean) isolates give significantly lower values [71 to 78%, except for 88% between LAV(ELI) and Z6]. This suggests that the African isolates diverged earlier than the U.S. isolates or that transmission of the virus has been more rapid in Africa. Two previous presumptive Haitian isolates are similar to each other and to the U.S. isolates to the same degree as are other U.S. isolates, but differ more markedly from the African isolates, suggesting a common lineage of Haitian and U.S. HIV-1 isolates.