Antiretroviral Resistance Patterns and HIV-1 Subtype in Mother-Infant Pairs after the Administration of Combination Short-Course Zidovudine plus Single-Dose Nevirapine for the Prevention of Mother-to-Child Transmission of HIV

Background. World Health Organization guidelines for prevention of mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) recommend administration of zidovudine and single-dose nevirapine (NVP) for HIV-1-infected women who are not receiving treatment for their own health or if complex regimens are not available. This study assessed antiretroviral resistance patterns among HIV-infected women and infants receiving single-dose NVP in Thailand, where the predominant circulating HIV-1 strains are CRF01_AE recombinants and where the minority are subtype B. Methods. Venous blood samples were obtained from (1) HIV-infected women who received zidovudine from 34 weeks' gestation and single-dose NVP plus oral zidovudine during labor and (2) HIV-infected infants who received single-dose NVP after birth plus zidovudine for 4 weeks after delivery. HIV-1 drug resistance testing was performed using the TruGene assay (Bayer HealthCare). Results. Most mothers and infants were infected with CRF01_A E. NVP resistance was detected in 34 (18%) of 190 women and 2 (20%) of 10 infants. There was a significantly higher proportion of NVP mutations in women with delivery viral loads of 150,000 copies/mL (adjusted odds ratio, 8.5; 95% confidence interval, 2.2-32.8, Pp.002 for linear trend) and in those with subtype B rather than CRF01_AE infections (38% vs. 16%; adjusted odds ratio, 3.6; 95% confidence interval, 1.1-11.8; Pp. 038). Conclusions. The lower frequency of NVP mutations among mothers infected with subtype CRF01_AE, compared with mothers infected with subtype B, suggests that individuals infected with subtype CRF01_AE may be less susceptible to the induction of NVP resistance than are individuals infected with subtype B.