Influence of human immunodeficiency virus type 1 subtype on mother-to-child transmission

The present study was designed to assess whether the subtype of human immunodeficiency virus type 1 (HIV-1) could affect the rate of HIV-1 mother-to-child transmission in a cohort of 31 HIV-1-seropositive pregnant Tanzanian women. In order to assign a subtype to the samples analysed, nucleotide sequencing of the HIV-1 long terminal repeat U3 and C2V3C3 envelope regions was performed from the sera of these 31 pregnant women. Except in three cases, amplification of both regions was achieved in all samples. Subtypes A (n=13, 46 %), C (n=6, 21 %) and D (n=2, 7 %), as well as a number (25 %) of A/C, C/A, D/A and C/D recombinant forms (n=3, 2, 1 and 1, respectively), were identified. Of the 31 HIV-1 seropositive pregnant women analysed, eight (26 %) transmitted HIV-1 to their infants. Among the eight transmitter mothers, four (4 of 13, 31 %) were infected with HIV-1 subtype A, one (1 of 6, 17 %) with HIV-1 subtype C, none (0 of 2, 0 %) with HIV-1 subtype D and three (3 of 7, 43 %) with HIV-1 subtype recombinant A/C. These findings show no significant differences in the mother-to-child transmissibility of HIV-1 subtypes A, C and D and detected recombinants forms.