Persistence of nevirapine-resistant HIV-1 in women after single-dose nevirapine therapy for prevention of maternal-to-fetal HIV-1 transmission

Abstract

Single-dose nevirapine (sdNVP) for prevention of mother-to-child transmission of HIV-1 can select nevirapine (NVP)-resistant variants, but the frequency, duration, and clinical significance of this resistance is not well defined. We used a sensitive allele-specific PCR assay to assess the emergence and persistence of NVPresistant variants in plasma samples from 22 women with HIV-1 subtype C infection who participated in a study of sdNVP for prevention of mother-to-child transmission of HIV-1. The women were categorized into three groups on the basis of detection of NVP resistance by standard genotype analysis. Group 1 (n ‫؍‬ 6) had NVP resistance detected at 2 and 6 mo after sdNVP, but not at 12 mo. Group 2 (n ‫؍‬ 9) had NVP resistance detected at 2 mo, but not 6 mo. Group 3 (n ‫؍‬ 7) had no NVP resistance detected at any time point. Allele-specific PCR analysis for the two most common NVP resistance mutations (K103N and Y181C) detected NVP-resistant variants in most (16 of 21) samples that were negative for NVP resistance by standard genotype, at levels ranging from 0.1% to 20% 1 yr after treatment. The frequency of NVP-resistant mutations decreased over time, but persisted above predose levels for more than 1 yr in >23% of the women. These findings highlight the urgent need for studies assessing the impact of sdNVP on the efficacy of subsequent antiretroviral therapy containing NVP or other nonnucleoside reverse transcriptase inhibitors.allele-specific PCR ͉ resistance ͉ low-frequency mutants T he treatment of pregnant women with antiretroviral therapy, in combination with zidovudine chemoprophylaxis administered to newborns, has dramatically reduced vertical transmission of HIV in developed countries (1-5). However, perinatal transmission of HIV-1 remains a major problem in developing countries because of limited access to antiretroviral therapy (6-8). In this latter setting, the simple regimen of maternal single-dose intrapartum nevirapine (NVP) and single-dose NVP (sdNVP) for the newborn reduces the risk of mother-to-child HIV-1 transmission (MTCT) by 41% through age 18 mo (9). Moreover, sdNVP has been demonstrated to be more effective than zidovudine chemoprophylaxis alone, and to be equivalent to NVP plus zidovudine in preventing MTCT (9-12). The efficacy of sdNVP in preventing MTCT is attributed to its potent antiviral activity, rapid absorption, placental transfer, and long half-life (13, 14). As a result, its use has been recommended by the World Health Organization as one of several options to reduce MTCT in resource-limited countries [Joint UNAIDS͞WHO press release (2000) (WHO, Geneva)].NVP is a potent nonnucleoside reverse transcriptase inhibitor (NNRTI) of HIV-1 (15-17). If administered as monotherapy, NVP selects for resistant variants within 1 wk, commonly those variants with the K103N and͞or Y181C mutations in reverse transcriptase, which confer cross-resistance to other approved drugs in the NNRTI class (18)(19)(20). The K103N mutation appears to have little effect on the replicative capacity o...

Role of low-frequency HIV-1 variants in failure of nevirapine-containing antiviral therapy in women previously exposed to single-dose nevirapine

“…These mutants most commonly encode K103N, Y181C, or G190A mutations in HIV-1 RT, conferring resistance to NVP and efavirenz. With the use of sensitive drug resistance assays, such as allele-specific PCR (ASP), resistant mutants can be detected in the majority of women after NVP exposure and can persist for years (6,7).…”

Improvement in allele-specific PCR assay with the use of polymorphism-specific primers for the analysis of minor variant drug resistance in HIV-1 subtype C

“…The studies from developing countries that use single-dose nevirapine are quite heterogeneous with respect to the techniques used and the frequency of nevirapine resistance mutations detected in different HIV-1 subtypes (Flys et al, 2005;Johnson et al, 2005;Lalonde et al, 2007;Loubser et al, 2006;Palmer et al, 2006a). All of the studies demonstrate that the commercial techniques are suboptimal in their ability to detect minor variants, but no consensus emerges from the data regarding the degree of resistance and the duration of persistence of minor variant resistance after nevirapine exposure.…”

“…Our technique differs from the protocol developed by others using universal primers specific to samples of HIV-1 subtype C (Palmer et al, 2006a). In this previous approach, a common reverse primer was used that did not overlie the site of interest and this allows for the quantitation of a total number of copies of amplicon in each sample.…”

“…Different sets of reverse primers were created. The universal primer set is exactly the same set of primers used in the protocol devised for subtype C (Palmer et al, 2006a), with the addition of a specific primer for the ntAAG. Allele-specific reverse primers were also constructed to match the varying template sequence in the primer binding site.…”

“…The exact nature of the clinical importance of minor variants remains unclear, but data suggests these populations of drug resistant viruses contribute to virologic failure (Jourdain et al, 2004;Lecossier et al, 2005), and may allow for the prediction of virologic failure at an earlier stage. As a result, several new assays have been developed to detect and quantify minor variant resistance (Bergroth et al, 2005;Flys et al, 2005;Nissley et al, 2005;Palmer et al, 2005;Shi et al, 2004), and the application of such techniques to HIV-1 subtype C samples has already provided insight into the persistence of drug resistance following single-dose nevirapine (Loubser et al, 2006;Palmer et al, 2006a).…”