Molecular characterization of HIV type 1 vpu genes from mothers and infants after perinatal transmission

We compared 162 vpu sequences of human immunodeficiency virus type 1 (HIV-1) in peripheral blood mononuclear cell DNA of 6 infected mother-infant pairs after perinatal transmission, and found a 90.12% frequency of intact vpu open reading frames. The heterogeneity of vpu genes between epidemiologically linked mother-infant pairs was lower compared with epidemiologically unlinked individuals. However, the variability of vpu genes was higher than that seen for other HIV-1 genes, including vif, vpr, tat, and gag p17 from the same mother-infant pairs. Moreover, the infants' sequences displayed patterns similar to those seen in their mothers. The functional domains essential for Vpu activity, including efficient release of virus particles from infected cells and CD4 degradation, were conserved in most of the sequences. In a phylogenetic analysis, the 162 sequences from 6 mother-infant pairs formed distinct clusters for each mother-infant pair sequences and grouped with subtype B sequences. These data support the importance of vpu in HIV-1 replication of mother-infant isolates that are involved in perinatal transmission.