Frequent nevirapine resistance in infants infected by HIV-1 via breastfeeding while on nevirapine prophylaxis.

Objective: The objective of this study is to assess nevirapine (NVP) resistance in infants who became infected in the three arms of the Breastfeeding, Antiretrovirals and Nutrition (BAN) study: daily infant NVP prophylaxis, triple maternal antiretrovirals or no extra intervention for 28 weeks of breastfeeding.

Design: A prospective cohort study.

Methods: The latest available plasma or dried blood spot specimen was tested from infants who became HIV-positive between 3 and 48 weeks of age. Population sequencing was used to detect mutations associated with reverse transcriptase inhibitor resistance. Sequences were obtained from 22 out of 25 transmissions in the infant-NVP arm, 23 out of 30 transmissions in the maternal-antiretroviral arm and 33 out of 38 transmissions in the control arm.

Results: HIV-infected infants in the infant-NVP arm were significantly more likely to have NVP resistance than infected infants in the other two arms of the trial, especially during breastfeeding through 28 weeks of age (56% in infant-NVP arm vs. 6% in maternal-antiretroviral arm and 11% in control arm, P¼0.004). There was a nonsignificant trend, suggesting that infants with NVP resistance tended to be infected earlier and exposed to NVP while infected for a greater duration than infants without resistance.

Conclusion: Infants on NVP prophylaxis during breastfeeding are at a reduced risk of acquiring HIV, but are at an increased risk of NVP resistance if they do become infected. These findings point to the need for frequent HIV testing of infants while on NVP prophylaxis, and for the availability of antiretroviral regimens excluding NVP for treating infants who become infected while on such a prophylactic regimen.