Reverse transcriptase genotypes in pediatric patients failing initial antiretroviral therapy in Gaborone, Botswana.

Background: Limited data are available on patterns of resistance mutations in pediatric patients in southern Africa, where HIV-1 subtype C (HIV-1C) predominates.

Methods: Retrospective chart review of pediatric patients. Nucleoside reverse transcriptase inhibitor (NRTI)- and nonnucleoside reverse transcriptase inhibitor (NNRTI)-associated resistance mutations quantified from population-based sequencing genotypic resistance assay results taken at time of first-line antiretroviral therapy (ART) failure (first-line ART = stavudine [d4T] or zidovudine [ZDV] + lamivudine [3TC] + nevirapine [NVP] or efavirenz [EFV]).

Results: Total number of patients with resistance assays analyzed is 45. Nucleoside reverse transcriptase inhibitor-associated mutation frequencies noted were M184V (n = 41; 91.1%); thymidine analogue mutations (TAMs; n = 20; 44.4%); >1 TAM (n = 9; 20%); TAM-2 pathway (n = 10; 22.2%); TAM-1 pathway (n = 7; 15.6%); TAM-1 and TAM-2 pathways (n = 3; 6.7%); K65R (n = 2; 4.4%); Q151M (n = 1; 2.2%); and L74V (n = 0; 0%). Nonnucleoside reverse transcriptase inhibitor-associated mutation frequencies noted were associated with notable resistance to either/both NVP and EFV (n = 40; 88.9%); K103N (n = 15; 33.3%); ≥1 mutations associated with etravirine (ETR) failure (K101E, Y181C, and G190A; n =20; 44.4%); and ≥2 notable NNRTI mutations (n = 12; 26.7%).

Conclusions: In this cohort, low-genetic barrier mutations were common, as were TAMs, including more than 1 TAM. Mutations compromising nonthymidine analogue backbones were rare, suggesting that it is likely that children who fail first-line NRTI backbones containing d4T or ZDV/3TC would still respond to abacavir (ABC), didanosine (ddI), and, for adolescents, tenofovir (TDF). Our data support the empiric continuation of 3TC in second-line regimens.