High prevalence of primary lamivudine and nelfinavir resistance in HIV-1-infected pregnant women in the United States, 1998-2004

HIV drug resistance and mother-to-child transmission of HIV

This article covers HIV drug resistance among pregnant women and the implications of transmission of resistant HIV to the infant. Resistance to antiretroviral drugs may be acquired or can emerge while HIV-infected pregnant women are on antiretroviral therapy, either before or during pregnancy. Resistance to antiretroviral drugs among HIV-infected infants may be acquired from the mother in utero or during the intrapartum period. Resistance may also emerge from exposure to antiretroviral drugs given to the infant for prophylaxis against HIV transmission. In settings where breastfeeding is practiced, ongoing transmission of HIV from breastfeeding may lead to transmission of resistant HIV from the mother. If the mother is taking antiretroviral drugs while breastfeeding, resistance to antiretroviral drugs may emerge in an HIV-infected infant from ingestion of antiretroviral drugs via breast milk. The magnitude and implications of antiretroviral resistance among HIV-infected pregnant women and HIV-infected infants are summarized.

Increased detection of the HIV-1 reverse transcriptase M184V mutation using mutation-specific minority assays in a UK surveillance study suggests evidence of unrecognized transmitted drug resistance

OBJECTIVES

The aim of the study was to estimate the levels of transmitted drug resistance (TDR) in HIV-1 using very sensitive assays to detect minority drug-resistant populations.

METHODS

We tested unlinked anonymous serum specimens from sexual health clinic attendees, who had not received an HIV diagnosis at the time of sampling, by both standard genotyping and using minority detection assays.

RESULTS

By standard genotyping, 21 of 165 specimens (12.7%) showed evidence of drug resistance, while, using a combination of standard genotyping and minority mutation assays targeting three commonly observed drug resistance mutations which cause high-level resistance to commonly prescribed first-line antiretroviral therapy (ART), this rose to 32 of 165 (19.4%). This increase of 45% in drug resistance levels [95% confidence interval (CI) 15.2-83.7%; P=0.002] was statistically significant. Almost all of this increase was accounted for by additional detections of the M184V mutation.

CONCLUSIONS

Future surveillance studies of TDR in the United Kingdom should consider combining standard genotyping and minority-specific assays to provide more accurate estimates, particularly when using specimens collected from chronic HIV infections in which TDR variants may have declined to low levels.

Pre-existing minority drug-resistant HIV-1 variants, adherence, and risk of antiretroviral treatment failure

BACKGROUND

The clinical relevance of detecting minority drug-resistant human immunodeficiency virus type 1 (HIV-1) variants is uncertain.

METHODS

To determine the effect of pre-existing minority nonnucleoside reverse-transcriptase inhibitor (NNRTI)-resistant variants on the risk of virologic failure, we reanalyzed a case-cohort substudy of efavirenz recipients in AIDS Clinical Trials Group protocol A5095. Minority K103N or Y181C populations were determined by allele-specific polymerase chain reaction in subjects without NNRTI resistance by population sequencing. Weighted Cox proportional hazards models adjusted for recent treatment adherence estimated the relative risk of virologic failure in the presence of NNRTI-resistant minority variants.

RESULTS

The evaluable case-cohort sample included 195 subjects from the randomly selected subcohort (51 with virologic failure, 144 without virologic failure), plus 127 of the remaining subjects who experienced virologic failure. Presence of minority K103N or Y181C mutations, or both, was detected in 8 (4.4%), 54 (29.5%), and 11 (6%), respectively, of 183 evaluable subjects in the random subcohort. Detection of minority Y181C mutants was associated with an increased risk of virologic failure in the setting of recent treatment adherence (hazard ratio, 3.45 [95% confidence interval, 1.90-6.26]) but not in nonadherent subjects (hazard ratio, 1.39 [95% confidence interval, 0.58-3.29]). Of note, 70% of subjects with minority Y181C variants achieved long-term viral suppression.

CONCLUSIONS

In adherent patients, pre-existing minority Y181C mutants more than tripled the risk of virologic failure of first-line efavirenz-based antiretroviral therapy.

CLINICAL TRIALS REGISTRATION

NCT00013520.

A review of nucleoside reverse transcriptase inhibitor use to prevent perinatal transmission of HIV

Worldwide, women comprise > 50% of all people living with HIV and the vast majority of these women are of childbearing age. In fact, a significant proportion of these women are identified as HIV-infected during pregnancy. Preventing perinatal transmission has been one of the greatest prevention successes of the HIV epidemic with < 2% of live births resulting in an HIV-infected infant. The strategic use of combination antiretroviral therapy has been a critical component of this reduction. With more antiretroviral agents available for HIV, the appropriate selection of therapy is often based on provider familiarity with the various agents. Although benefits of antiretroviral use in pregnancy tremendously outweigh the risks, concerns regarding short- and long-term toxicity in mothers and their children, in addition to the risk of the development of HIV resistance, remain subjects of discussion. The choice of antiretroviral 'backbone' is supported by extensive data showing efficacy in the prevention of HIV vertical transmission. Co-formulated zidovudine/lamivudine is the most commonly used combination in pregnancy. Long-term consequences of in utero exposure to antiretroviral agents are not fully understood. In this article, we review the data regarding nucleoside reverse transcriptase inhibitors with a focus on tenofovir.

Postpartum antiretroviral drug resistance in HIV-1-infected women receiving pregnancy-limited antiretroviral therapy

BACKGROUND

Pregnancy-limited antiretroviral therapy (PLAT) drastically reduces HIV-1 transmission to the newborn, but may select for antiretroviral drug resistance mutations in mothers.

METHODS

We evaluated antiretroviral-naive, HIV-1-infected pregnant women who received PLAT between 1998 and 2005, and had 2-month or 6-month postpartum plasma samples available with HIV-1 RNA levels more than 500 copies/ml. Postpartum drug resistance mutation rates were assessed blindly using population sequencing and allele-specific PCR (ASPCR) of the M184V, K103N and D30N mutations. Factors associated with selection of drug resistance mutations were investigated.

RESULTS

One hundred and forty-six women were included. All women received zidovudine and lamivudine during pregnancy; 76% also received nelfinavir and 8.2% nevirapine. Resistance data were available from 114 women (78%). Postpartum rates of single-class, dual-class, and triple-class resistance were, respectively, 43, 6.1 and 0% (63.2, 10.5 and 1.7% by ASPCR). In women receiving dual or triple PLAT, respectively, postpartum M184V/I rates were 65% (95% by ASPCR) and 28.7% (51.6% by ASPCR), respectively (P < 0.01). Postpartum nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance rates among women receiving nevirapine were 25% for K103N (37.5% by ASPCR) and 12.5% for Y188C. Protease inhibitor resistance rates in women receiving nelfinavir were 1.1% for D30N (1.1% by ASPCR) and 1.1% for L90M. Dual versus triple PLAT and prolonged zidovudine exposure were associated with selection of M184V. Nevirapine use and length of zidovudine and lamivudine exposure were associated with selection of K103N.

CONCLUSION

PLAT is associated with frequent selection of resistance to drugs with low-genetic barrier. Triple-drug PLAT decreases the odds for M184V selection. Routine postpartum genotypic resistance testing may be useful to guide future treatment decisions in mothers.

Clinical management of HIV-1 resistance

Antiretroviral drug resistance is a fundamental survival strategy for the virus that stems from its vast capacity to generate diversity. With the recent availability of new ARV drugs and classes, it is now possible to prescribe fully active ART to most HIV-infected subjects and achieve viral suppression even in those with multidrug-resistant HIV. It is uncertain, however, if this scenario will endure. Given that ART must be given for life, and new compounds other than second-generation integrase inhibitors may not reach the clinic soon, all efforts must be done to avoid the development of resistance to the new agents. Here, we discuss relevant aspects for the clinical management of antiretroviral drug resistance, leaving detailed explanations of mechanisms and mutation patterns to other articles in this issue. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, vol. 85, issue 1, 2010.