Isolation and characterization of a new subtype A variant of human immunodeficiency virus type I from Nigeria

We have isolated a new variant of HIV-1 from Nigeria, Africa. The virus was recovered from the peripheral blood mononuclear cells (PBMCs) of an apparently healthy 23-year-old male from Ibadan, Nigeria. The in vitro studies indicated that the virus was highly cytopathic and replicated well in normal PBMCs, established T-cell lines and the monocytic cell line U937. The highest replicative titre of the virus was obtained in freshly isolated primary macrophage/monocyte cells which also showed the least cytopathology. Most other cultures showed single-cell cytolysis and giant cells, and syncytia were not induced in the HTLV-1 infected MT-2 cells. Since no HIV strain has been isolated from Nigeria, we obtained cDNA clones containing the env gene, to further characterize the Nigerian virus. Based on the DNA sequence analysis of 14 clones containing the coding region for its gp 120 protein, the Nigerian HIV isolate has been classified as HIV-1 subtype A. Only one subtype A virus from Rwanda has been characterized and this virus has not been shown to exhibit extreme cytopathicity in various cell types as was observed with the Nigerian strain. Further, the ability of this virus to grow well in lymphocytes, monocytes and macrophages and to exhibit cytopathicity without causing syncytia are uncommon properties distinguishing the Nigerian virus from other HIV-1 strains. Since most macrophage-tropic viruses have been associated with 'neurotropism', the isolation of an HIV-1 strain from the blood of an individual with no known neurological disorder indicates that this rapidly replicating cytopathic virus, with a broad host range, may play an important role in the pathogenesis of HIV disease. This represents the first report of an HIV-1 isolate from Nigeria.