Gag-p6 Tsg101 binding site duplications in maternal-infant HIV infection

Prevalence and patterns of HIV p6 duplications in HIV-1 mother-to-baby transmission are examined. Resistance genotyping was performed in a multisite U.S. study of antiretroviral resistance in vertical transmission. Sequence data were used in secondary analyses of HIV genetic variation. Two hundred sixty HIV viral RNA samples from HIV-infected pregnant women and their infants were analyzed with a commercial resistance genotyping kit. Chromatograms were examined for variability in the 3' region of gag. From 103 mother-baby sets, 190 samples gave readable p6 sequence. Of 103 mother-baby sets, 20 (19%) showed duplication of between 3 and 12 codons ending at the PTAPP motif of p6. When maternal p6 duplication was present and the p6 sequence was available from both maternal and infant isolates, all (seven of seven) infants had p6 duplications, but two cases showed discordancies between maternal and infant sequences. The prevalence of p6 duplication varied among geographical sites, ranging from 4 of 43 families (9%, Puerto Rico and New York sites) to 16 of 60 families (27%, Massachusetts, Texas, and Illinois). The presence of p6 duplication was not associated with differences in transmission, viral load, or disease progression in the infants, but showed a trend toward association with lower maternal CD4 count. Substantial p6 variation data are generated by resistance genotyping. PTAP duplication is prevalent in this group of HIV-infected women and infants. The duplication is efficiently transmitted from mother to infant, is present at variable prevalence at different geographic sites, and shows no clear association with vertical transmission risks.