Evaluation of postpartum HIV superinfection and mother-to-child transmission

OBJECTIVE: This study examined HIV superinfection in HIV-infected women postpartum and its association with mother-to-child transmission (MTCT). DESIGN: Plasma samples were obtained from HIV-infected women who transmitted HIV to their infants after 6 weeks of age (transmitters n = 91) and HIV-infected women who did not transmit HIV to their infants (nontransmitters n = 91). These women were originally enrolled in a randomized trial for prevention of MTCT of HIV in Malawi (Post-Exposure Prophylaxis of Infants trial in Malawi). METHODS: Two HIV genomic regions (p24 and gp41) were analyzed by next-generation sequencing for HIV superinfection. HIV superinfection was established if the follow-up sample contained a new phylogenetically distinct viral population. HIV superinfection and transmission risk were examined by multiple logistic regression adjusted for Post-Exposure Prophylaxis of Infants study arm baseline viral load baseline CD4 cell count time to resumption of sex and breastfeeding duration. RESULTS: Transmitters had lower baseline CD4 cell counts (P = 0.001) and higher viral loads (P < 0.0001) compared with nontransmitters. There were five cases of superinfection among transmitters (rate of superinfection = 4.7/100 person-years) compared with five cases among the nontransmitters (rate of superinfection = 4.4/100 person-years; P = 0.78). HIV superinfection was not associated with increased risk of postnatal MTCT of HIV after controlling for maternal age baseline viral load and CD4 cell count (adjusted odds ratio = 2.32 P = 0.30). Longer breastfeeding duration was independently associated with a lower risk of HIV superinfection after controlling for study arm and baseline viral load (P = 0.05). CONCLUSION: There was a significant level of HIV superinfection in women postpartum but this was not associated with an increased risk of MTCT via breastfeeding.