Background: The HIVNET 012 trial in Uganda demonstrated that single dose nevirapine (NVP) prophylaxis is effective for preventing HIV-1 mother-to-child transmission. Women in the NVP arm of HIVNET 012 received a single dose of NVP in labor. Previous studies demonstrated that NVP resistance (NVPR) mutations were detectable in 21 (19%) of 111 women at 6–8 wks post-partum. An exploratory study further suggested that the rate of NVPR was higher in women infected with subtype D than subtype A HIV-1.

Methods: We extended the studies described above by analyzing samples from 271 of the 313 women enrolled in the NVP arm of HIVNET 012 (all available samples). This included 143 subtype A, 94 subtype D, 6 subtype C, and 28 inter-subtype recombinant samples. HIV-1 genotyping was performed with the Applied Biosystems ViroSeq HIV-1 Genotyping System and subtyping was performed by phylogenetic analysis of pol region sequences.

Results: NVPR mutations were detected in 66 (24%) of the 271 women at 6–8 wks post-partum. In a univariate analysis, women with subtype D were more likely to have NVPR mutations than women with subtype A: 35/94 (37%) in subtype D vs 24/143 (17%) in subtype A, odds ratio (OR) = 2.9 (95% CI: 1.6-5.4). In a logistic regression model controlling for baseline RNA and CD4 count, all variables in the model were independent predictors of resistance. Controlling for baseline RNA and CD4 count, the OR for subtype in this model was 3.0 (95% CI: 1.6-5.9).

Conclusions: This extended analysis of NVPR in the HIVNET 012 trial further defines the rate of NVPR in women 6–8 wks after single dose NVP. The extended analysis provides further evidence that the rate of NVPR is higher among women with subtype D vs A. This suggests that the rate of NVPR following single dose NVP prophylaxis may vary from region to region, depending on which subtypes are prevalent.