Molecular and biological characterization of a replication competent human immunodeficiency type 2 (HIV-2) proviral clone

We obtained complete genomic clones of human immunodeficiency virus type 2 (HIV-2) from the DNA of the neoplastic human cell line HUT 78 freshly infected with a HIV-2 isolate, strain SBL6669. The recombinant phage DNA was transfected into the lymphocytes of CD4-positive HUT 78 cell line to test the replication competence of the proviral DNA. One genomic clone, designated HIV-2(SBL/ISY), yielded retroviral particles after a few weeks of culture of the transfected cells. The HIV-2(SBL/ISY) clone contained a complete provirus and cellular flanking sequence. We obtained the DNA sequence of the provirus and compared it with the published sequence of two other HIV-2 isolates. The degree of variability among HIV-2 isolates is comparable to that observed among African HIV-1 isolates sequenced to date. Immunologically, HIV-2(SBL/ISY) is similar to the parental virus (HIV-2(SBL6669)) but differs in the envelope transmembrane protein that is truncated (gp32-34) in the parental virus and not in HIV-2(SBL/ISY) (gp41). Both the parental and the cloned viruses are infectious and cytopathic for some human T-cell lines, induce syncytia, and infect a human macrophage cell line (U397) in vitro. The availability of a biologically active HIV-2 clone provides the means to study the role and interaction of HIV-2 genes in vitro as well as to assess the functional similarities among HIV-1 and HIV-2 genes. Since HIV-2(SBL/ISY) cloned virus infects fresh peripheral blood T cells from Rhesus macaques in vitro and infects the same animal in vivo, its use in animals may represent a model for functional study of viral genes in vivo as well as for development of experimental approaches to prevent and cure retroviral infection in humans.