In an investigation of the evolution of the third hypervariable loop of gpl20 (V3), the principal neutralization determinant of human immunodeficiency virus type 1, we have analyzed 89 V3 sequences of plasma viral RNA purified from peripheral blood samples donated over 7 years by an infected hemophiliac. Considerable sequence diversity in the V3 region was found at all time points after seroconversion. Phylogenetic analysis revealed that an important diversification had occurred by 3 years posinfection and that, subsequently, most sequences could be allocated to either one of two major lineages that persisted throughout the remainder of the infection. Rapid changes in frequency of the most common sequences and the observation that the same hexapeptide motif (GPGSAV) at the crown of the V3 loop has evolved convergently provide strong evidence that selective processes determine the evolutionary fate of sequence variants in this region.

Sequence change in different hypervariable regions of the external membrane glycoprotein (gpl20) of human immunodeficiency virus type 1 (HIV-1) was studied. Viral RNA associated with cell-free virus particles circulating in plasma and proviral DNA present in HIV-infected peripheral blood mononuclear cells (PBMCs) were extracted from blood samples of two currently asymptomatic hemophiliac patients over a 5-year period. HIV sequences were amplified by polymerase chain reaction to allow analysis in the V3, V4, and V5 hypervariable regions of gpl20. Rapid sequence change, consisting of regular replacements by a succession of distinct viral populations, was found in both plasma virus and PBMC provirus populations. Significant differences between the frequencies of sequence variants in DNA and RNA populations within the same sample were observed, indicating that at any one time point, the predominant plasma virus variants were antigenically distinct from viruses encoded by HIV DNA sequences in PBMCs. How these findings contribute to current models of HIV pathogenesis is discussed.

To investigate the prevalence of hepatitis C virus infection in two risk groups, stored serum samples from treated haemophiliacs and intravenous drug users were tested for anti-HCV by both anti-C-100 based and second generation ELISAs (Abbott and Ortho) followed by testing in two confirmatory immunoblot assays that incorporate core as well as other non-structural antigens (Innogenetics LIA and Chiron RIBA-HCV test). Clear evidence of HCV infection was found in all but one of 78 haemophiliacs treated with non-virus inactivated clotting factor concentrates, but in none exposed only to super dry heat-treated concentrates. Only four samples gave rise to conflicting serological results between the four tests, two of these occurred in patients with advanced HIV related disease and almost certainly reflected loss of humoral immunity associated with disease progression, and the others occurred in the only two patients tested who were chronic carriers of hepatitis B infection and may reflect an interaction between the two viruses. Comparison of anti-C-100 versus second generation tests in immunocompetent drug users revealed a false negative rate of 20% using C-100 alone, indicating the advantage of using second generation assays for detection of past or current HCV infection. Of all of the antigens used in the confirmatory assay, positive sera showed strongest and most frequent reactivity with the C22 and C33c proteins (Ortho RIBA).

Recall of patients who had been treated by a human immunodeficiency virus (HIV)-infected surgeon uncovered 1 previously unknown HIV-seropositive person. Nucleotide sequencing of the gag gene and maximum likelihood phylogenetic analysis were used to investigate the relationships among sequences from the surgeon, the patient, and an anonymous blood donor from whom the patient had received blood products. The likelihoods of all possible pathways of transmission linking these persons were estimated. On these data, transmission from the surgeon to the patient was significantly less likely than from the blood donor to the patient. It is concluded that none of the recalled patients were infected by the surgeon.

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