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, n91) and HIV-infected women who did not transmit HIV to their infants (nontransmitters, n91). 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 (P0.001) and higher viral loads (P<0.0001) compared with nontransmitters. There were five cases of superinfection among transmitters (rate of superinfection4.7/100 person-years) compared with five cases among the nontransmitters (rate of superinfection4.4/100 personyears; P0.78). 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 ratio2.32, P0.30). Longer breastfeeding duration was independently associated with a lower risk of HIV superinfection after controlling for study arm and baseline viral load (P0.05). 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.