Background

Antiretroviral therapy (ART) has become more available throughout the developing world during the past five years. The World Health Organization recommends nonnucleoside reverse transcriptase inhibitor-based regimens as initial ART. However, their efficacy may be compromised by resistance mutations selected by single-dose nevirapine (sdNVP) used to prevent mother-to-child-transmission of HIV-1 (PMTCT). There is no simple and efficient method to detect such mutations at initiation of ART.

Methods

181 women participating in a PMTCT clinical trial who started NVP-ART after they had received sdNVP or placebo were tested for nevirapine-resistance point-mutations (K103N, Y181C, and G190A) using 100 copies of HIV-1 DNA with a sensitive oligonucleotide ligation assay (OLA) able to detect mutants at low concentrations (≥5% of the viral population). Virologic failure was defined as plasma HIV-1 RNA confirmed >50 copies/mL between 6–18 months of NVP-ART.

Results

At initiation of NVP-ART, resistance mutations were identified in 26% of 148 participants given sdNVP (K103N-13%, Y181C-5%, G190A-19%; ≥2 mutations-10%) at a median 9.3 months after sdNVP. The risk of virologic failure was .62 (95% confidence interval (CI), 0.46–0.77) in women with ≥1 resistance mutation, compared to 0.25 (95% CI, 0.17–0.35) in those without detectable resistance mutations (P<.0001). Failure was independently associated with resistance, an interval of <6 months between sdNVP and NVP-ART initiation, and a viral load above the median at NVP-ART initiation.

Conclusions

Access to simple and inexpensive assays to detect low-concentrations of NVP-resistant HIV-1 DNA prior to the initiation of ART could help improve the outcome of first-line antiretroviral therapy.

A single dose of nevirapine (sdNVP) to prevent mother-to-child transmission of HIV-1 increases the risk of failure of subsequent NVP-containing antiretroviral therapy (ART), especially when initiated within 6 months of sdNVP administration, emphasizing the importance of understanding the decay of nevirapine-resistant mutants. Nevirapine-resistant HIV-1 genotypes (with the mutations K103N, Y181C, and/or G190A) from 21 women were evaluated 10 days and 6 weeks after sdNVP administration and at the initiation of ART. Resistance was assayed by consensus sequencing and by a more sensitive assay (oligonucleotide ligation assay [OLA]) using plasma-derived HIV-1 RNA and cell-associated HIV-1 DNA. OLA detected nevirapine resistance in more specimens than consensus sequencing did (63% versus 33%, P < 0.01). When resistance was detected only by OLA (n = 45), the median mutant concentration was 18%, compared to 61% when detected by both sequencing and OLA (n = 51) (P < 0.0001). The proportion of women whose nevirapine resistance was detected by OLA 10 days after sdNVP administration was higher when we tested their HIV-1 RNA (95%) than when we tested their HIV-1 DNA (88%), whereas at 6 weeks after sdNVP therapy, the proportion was greater with DNA (85%) than with RNA (67%) and remained higher with DNA (33%) than with RNA (11%) at the initiation of antiretroviral treatment (median, 45 weeks after sdNVP therapy). Fourteen women started NVP-ART more than 6 months after sdNVP therapy; resistance was detected by OLA in 14% of the women but only in their DNA. HIV-1 resistance to NVP following sdNVP therapy persists longer in cellular DNA than in plasma RNA, as determined by a sensitive assay using sufficient copies of virus, suggesting that DNA may be superior to RNA for detecting resistance at the initiation of ART.