Rapid development of antiretroviral drug resistance mutations in HIV-infected children less than two years of age initiating protease inhibitor-based therapy in South Africa.

Data on the development of antiretroviral drug resistance in HIV-1-infected children receiving protease inhibitor (PI)-based antiretroviral therapy (ART) are limited. We examined antiretroviral resistance among a cohort of 323 South African HIV-infected children <2 years old exposed to nevirapine for prevention of mother-to-child transmission. Ritonavir (RTV) was used initially for 138 children who were <6 months old or receiving antimycobacterial therapy; otherwise children received lopinavir/ritonavir (LPV/r)-based ART. HIV-1 population sequencing of the pol gene was conducted on all pretreatment samples and on posttreatment samples for children who did not achieve HIV-1 plasma RNA <400 copies/ml by 52 weeks. Among children in the cohort, 38 died, 22 had <24 weeks follow-up, 209 achieved virologic suppression, and 54 did not. Of 41 children without virologic suppression with posttreatment HIV genotype data available, major resistance mutations were found in 32 (78%): 14 (36%) had PI mutations including V82A, M46I, and L90M; 29 (71%) had M184V/I; and three had NNRTI mutations (K103N, Y181C, and G190A). Among the children who did not achieve virologic suppression, none of the seven children treated exclusively with LPV/r developed PI-related mutations, compared with 14 of 32 (44%) who received RTV-based regimens (p=0.036); PI genotypes were unavailable for two children. Seventy-eight percent of children without virologic suppression developed resistance mutations that impact second-line ART options. Only children who received RTV-based ART developed major PI-related resistance mutations, and use of this regimen should be avoided.