We studied the heterogeneity and intactness of the vif gene in six HIV- 1-infected individuals at various clinical stages. The proviral vif sequences in peripheral blood mononuclear cells were amplified by PCR, followed by cloning and sequencing of 45 vif clones. The intraindividual diversity of the vif genes ranged from 0.45 to 3.3% and was not correlated with disease stage. Although the vif gene has been shown to be essential for infection of HIV-1 in vitro, a high frequency (31%) of defective vif genes was observed. In one patient, six vif clones carried double nonsense mutations at the same positions, five of which were clustered in the phylogenetic tree, suggesting that these vif-defective viruses may have replicated in vivo. Phylogenetic analysis revealed that the vif sequences from each individual were clustered into a separate group and that all of them belong to subtype B.
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