Perinatal transmission of major, minor, and multiple maternal human immunodeficiency virus type 1 variants in utero and intrapartum

Previous studies have provided conflicting data on the presence of selectiv e pressures in the transmission of a homogeneous maternal viral subpopulati on to the infant. Therefore, the purpose of this study was to definitively characterize the human immunodeficiency virus type 1 (HIV-1) quasispecies t ransmitted in utero and intrapartum, HIV-1 envelope gene diversity from per ipheral blood mononuclear cells and plasma was measured during gestation an d at delivery in mothers who did and did not transmit HIV perinatally by us ing a DNA heteroduplex mobility assay. Children were defined as infected in utero or intrapartum based on the timing of the first detection of HIV. Un treated transmitting mothers (n = 19) had significantly lower HIV-1 quasisp ecies diversity at delivery than untreated nontransmittting mothers (n = 18 ) (median Shannon entropy, 0.711 [0.642 to 0.816] versus 0.853 [0.762 to 0. 925], P = 0.005), Eight mothers transmitted a single major env variant to t heir infants in utero, and one mother transmitted a single major env varian t intrapartum, Four mothers transmitted multiple HIV-1 env variants to thei r infants in utero, and two mothers transmitted multiple env variants intra partum, The remaining six intrapartum- and two in utero-infected infants ha d a homogeneous HIV-1 env quasispecies which did not comigrate with their m others' bands st their first positive time point. In conclusion, in utero t ransmitters were more likely to transmit single or multiple major maternal viral variants. In contrast, intrapartum transmitters were more likely to t ransmit minor HIV-1 variants. These data indicate that different selective pressures, depending on the timing of transmission, may be involved in dete rmining the pattern of maternal HIV-1 variant transmission.