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

In November 1993 an apparently healthy 23-year-old man with no known neurological disorder donated blood for an extended family member who required a blood transfusion at University College Hospital in Ibadan Nigeria. His plasma tested positive for HIV-1 antibodies. It also had 125 pg/ml of HIV-1 p24 protein without the dissociation of immune complexes. Laboratory researchers recovered a new variant of HIV-1 from the peripheral blood mononuclear cells (PBMCs). In vitro the new HIV-1 variant was very cytopathic and replicated well in normal PBMCs in established T-cell lines and in the monocytic cell line U937. Freshly isolated primary macrophage/monocyte cells achieved the highest replicative titre of the new virus and had the least cytopathology. The researchers used cDNA clones containing the env gene to further characterize the new virus. DNA sequence analysis of 14 clones with the coding region for its gp 120 protein classified the Nigerian HIV isolate as HIV-1 subtype A. Only one other subtype A virus from Rwanda has been characterized. It did not exhibit extreme cytopathicity in various cell types as did the Nigerian strain. Distinguishing characteristics of the Nigerian strain include: it grows well in lymphocytes monocytes and macrophages and exhibits cytopathicity without causing syncytia. The Nigerian man from whom the new strain came developed AIDS 6 months after the blood donation and died 4 months later. Most macrophage-tropic viruses are linked to neurotropism. The Nigerian cytopathic HIV-1 strain a macrophage-tropic virus replicates quickly. These findings suggest that this new HIV-1 strain may have enhanced pathogenesis and the rapid onset of clinical disease within a short period.