Seven new human immunodeficiency virus type 2 (HIV-2) isolates (CBL-20 to CBL-26) from The Gambia were characterized. Their cytopathogenicity and growth in vitro correlated with the severity of clinical disease. CBL-22 was highly sensitive to neutralization by HIV-2 sera and was cross-neutralized by some HIV-1 sera. These findings, the differing sizes of envelope glycoproteins of individual isolates, and the sequence analysis of amplified regions of the viral DNAs show that these HIV-2 isolates from one geographical region in West Africa exhibit biological and genome variability comparable to that observed for HIV-1.
PIP: Although the immunodeficiency diseases associated with human immunodeficiency virus (HIV) 1 and 2 are indistinguishable from each other, there is some evidence that HIV-2 isolates may have a longer incubation period. Thus, an investigation was conducted of the biological properties and molecular variability of the spectrum of HIV-2 isolates existing in The Gambia. Serum samples were obtained from 20 HIV-2-positive individuals attending a sexually transmitted diseases clinic in Fajara. Seven new HIV-2 isolates (CBL-20 to CBL-26) were identified. Each differed in terms of its growth rate, cytopathogenicity in vitro, and sensitivity to neutralizing antibodies in patient sera. In addition, there was a close association between the isolates' in vitro cytopathogenicity and the clinical cytopathogenic strains, were obtained from the two patients with acquired immunodeficiency syndrome (AIDS). In contrast, patients from whom CBL-25 and 26 were isolated have been asymptomatic for at least 3 years. CBL-22 was highly sensitive to neutralization by HIV-2 sera and was cross-neutralized by some HIV-1 sera. It is speculated that the observed differences in sensitivity to neutralization reflect differences in antigenic epitope expression or the number and presentation of envelope glycoprotein molecules on an infectious virion. Analysis of the molecular weight of the envelope precursor and the outer envelope protein of various HIV-2 isolates revealed that all the CBL isolated and SBL-6669 have smaller envelope proteins than the prototype strain, LAV-2 ROD. Also observed were differences in the amino acid sequences of these HIV-2 isolates.