Identification of nevirapine-resistant HIV-1 in the latent reservoir after single-dose nevirapine to prevent mother-to-child transmission of HIV-1

HIV DNA Sequencing to Detect Archived Antiretroviral Drug Resistance

INTRODUCTION

Proviral HIV DNA integrated within CD4 T-cells maintains an archive of viral variants that replicate during the course of the infection, including variants with reduced drug susceptibility. We considered studies that investigated archived drug resistance, with a focus on virologically suppressed patients and highlighted interpretative caveats and gaps in knowledge.

RESULTS

Either Sanger or deep sequencing can be used to investigate resistance-associated mutations (RAMs) in HIV DNA recovered from peripheral blood. Neither technique is free of limitations. Furthermore, evidence regarding the establishment, maintenance, expression and clinical significance of archived drug-resistant variants is conflicting. This in part reflects the complexity of the HIV proviral landscape and its dynamics during therapy. Clinically, detection of RAMs in cellular HIV DNA has a variable impact on treatment outcomes, modulated by the drugs affected, treatment duration and additional determinants of virological failure, including those leading to suboptimal drug exposure.

CONCLUSIONS

Sequencing cellular HIV DNA can provide helpful complementary information in treatment-experienced patients with suppressed plasma HIV RNA who require a change of regimen. However, care should be taken when interpreting the results. Presence of RAMs is not necessarily a barrier to treatment success. Conversely, even the most sensitive sequencing techniques will fail to provide a comprehensive view of the HIV DNA archive. To inform treatment decisions appropriately, the overall clinical and treatment history of a patient must always be considered alongside the results of resistance testing. Prospective controlled studies are needed to validate the utility of drug resistance testing using cellular HIV DNA.

Protection of Newborn Macaques by Plant-Derived HIV Broadly Neutralizing Antibodies: a Model for Passive Immunotherapy during Breastfeeding

Preventing human immunodeficiency virus (HIV) infection in newborns by vertical transmission remains an important unmet medical need in resource-poor areas where antiretroviral therapy (ART) is not available and mothers and infants cannot be treated prepartum or during the breastfeeding period. In the present study, the protective efficacy of the potent HIV-neutralizing antibodies PGT121 and VRC07-523, both produced in plants, were assessed in a multiple-SHIV (simian-human immunodeficiency virus)-challenge breastfeeding macaque model. Newborn macaques received either six weekly subcutaneous injections with PGT121 alone or as a cocktail of PGT121-LS plus VRC07-523-LS injected three times every 2 weeks. Viral challenge with SHIVSF162P3 was twice weekly over 5.5 weeks using 11 exposures. Despite the transient presence of plasma viral RNA either immediately after the first challenge or as single-point blips, the antibodies prevented a productive infection in all babies with no sustained plasma viremia, compared to viral loads ranging from 103 to 5 × 108 virions/ml in four untreated controls. No virus was detected in peripheral blood mononuclear cells (PBMCs), and only 3 of 159 tissue samples were weakly positive in the treated babies. Newborn macaques proved to be immunocompetent, producing transient anti-Env antibodies and anti-drug antibody (ADA), which were maintained in the circulation after passive broadly neutralizing antibody clearance. ADA responses were directed to the IgG1 Fc CH2-CH3 domains, which has not been observed to date in adult monkeys passively treated with PGT121 or VRC01. In addition, high levels of VRC07-523 anti-idiotypic antibodies in the circulation of one newborn was concomitant with the rapid elimination of VRC07. Plant-expressed antibodies show promise as passive immunoprophylaxis in a breastfeeding model in newborns. IMPORTANCE Plant-produced human neutralizing antibody prophylaxis is highly effective in preventing infection in newborn monkeys during repeated oral exposure, modeling virus in breastmilk, and offers advantages in cost of production and safety. These findings raise the possibility that anti-Env antibodies may contribute to the control of viral replication in this newborn model and that the observed immune responsiveness may be driven by the long-lived presence of immune complexes.

Human Immunodeficiency Virus Antiretroviral Resistance and Transmission in Mother-Infant Pairs Enrolled in a Large Perinatal Study

Background

The presence of antiretroviral drug-associated resistance mutations (DRMs) may be particularly problematic in human immunodeficiency virus (HIV)-infected pregnant women as it can lead to mother-to-child transmission (MTCT) of resistant HIV strains. This study evaluated the prevalence and the effect of antiretroviral DRMs in previously untreated mother-infant pairs.

Methods

A case-control design of 1:4 (1 transmitter to 4 nontransmitters) was utilized to evaluate DRMs as a predictor of HIV MTCT in specimens obtained from mother-infant pairs. ViroSeq HIV-1 genotyping was performed on mother-infant specimens to assess for clinically relevant DRMs.

Results

One hundred forty infants acquired HIV infection; of these, 123 mother-infant pairs (88%) had specimens successfully amplified using ViroSeq and assessed for drug resistance genotyping. Additionally, 483 of 560 (86%) women who did not transmit HIV to infants also had samples evaluated for DRMs. Sixty-three of 606 (10%) women had clinically relevant DRMs; 12 (2%) had DRMs against >1 drug class. Among 123 HIV-infected infants, 13 (11%) had clinically relevant DRMs, with 3 (2%) harboring DRMs against >1 drug class. In univariate and multivariate analyses, DRMs in mothers were not associated with increased HIV MTCT (adjusted odds ratio, 0.8 [95% confidence interval, .4-1.5]). Presence of DRMs in transmitting mothers was strongly associated with DRM presence in their infants (P < .001).

Conclusions

Preexisting DRMs were common in untreated HIV-infected pregnant women, but did not increase the risk of HIV MTCT. However, if women with DRMs are not virologically suppressed, they may transmit resistant mutations, thus complicating infant management.

Mathematical Models of HIV Latency

Viral latency is a major barrier to curing HIV infection with antiretroviral therapy, and consequently, for eliminating the disease globally. The establishment, maintenance, and potential clearance of latent infection are complex dynamic processes and can be best understood and described with the help of mathematical models. Here we review the use of viral dynamics models for HIV, with a focus on applications to the latent reservoir. Such models have been used to explain the multiphasic decay of viral load during antiretroviral therapy, the early seeding of the latent reservoir during acute infection and the limited inflow during treatment, the dynamics of viral blips, and the phenomenon of posttreatment control. In addition, mathematical models have been used to predict the efficacy of potential HIV cure strategies, such as latency-reversing agents, early treatment initiation, or gene therapies, and to provide guidance for designing trials of these novel interventions.

Pharmacogenetics of nevirapine excretion into breast milk and infants' exposure through breast milk versus postexposure prophylaxis

AIM

The influence of genetic factors on nevirapine (NVP) breast milk pharmacokinetics and breastfed infants' exposure were investigated.

PATIENTS & METHODS

Associations between nine SNPs in NVP disposition genes in mothers and its plasma and breast milk concentrations were explored in nursing mother-infant pairs.

RESULTS

NVP pharmacokinetics in maternal plasma, breast milk and infant exposure indices were influenced by CYP2B6 516G>T and 983T>C. The median (range) milk-to-plasma area under the curve (AUC0-12) ratio was 0.95 (0.56-1.5). Calculated as percentages of pediatric treatment, infant postexposure prophylaxis and maternal weight-adjusted doses, the maximum exposure indices were 3.64% (1.99-9.88), 26.0% (9.93-79.1) and 13.8% (5.77-27.7), respectively. Infant plasma concentration as a result of exposure through breast milk (n = 93), pre-exposure prophylaxis (n = 10) and both (n = 27) were 660 (104-3090), 1020 (401-3325) and 2720 ng/ml (1360-7290), respectively.

CONCLUSION

The clinical significance of the observed differences between routes of infants' exposure warrants further investigation.

Genetic Analyses of HIV-1 Strains Transmitted from Mother to Child in Northern Vietnam

We previously reported mother-to-child transmission of HIV-1 in nine (6.7%) of 135 children on nevirapine prophylaxis in Vietnam. In the current study, we investigated the appearance and profile of antiretroviral drug (ARV) resistance mutations, the predicted coreceptor usage, and the genetic diversity of HIV-1 strains isolated from the eight pairs of HIV-1-infected mothers and their children, who were followed up to 12 months after birth. Portions of the pol and env C2V3 regions of the HIV-1 strains were analyzed genetically. HIV-1 CRF01_AE RNA was detected in four (50%) children at delivery. Y181C, a nevirapine resistance mutation, appeared in two (25%) children 1 and 3 months after birth, respectively. No ARV resistance mutation was detected in the mothers, though three mothers were on ARV prophylaxis. Five mothers and their children harbored CCR5-tropic (R5) viruses. Two mothers harbored both R5 and CXCR4-tropic (X4) viruses, but their children harbored only R5 viruses even though the X4 viruses were dominant in the mothers. In the remaining one mother, HIV-1 RNA was not amplified and her child harbored both R5 and X4 viruses at birth, but only X4 virus 12 months after delivery. The infants' viruses were more homogeneous than their mothers' viruses (mean distance: 0.5% vs. 1.1%, respectively). This is the first molecular epidemiological study of vertical HIV-1 infections in Vietnam. These findings may provide useful knowledge for the prevention of mother-to-child transmission of HIV-1 and the antiretroviral treatment of children in Vietnam.

Challenges and Clinical Decision-Making in HIV-to-HIV Transplantation: Insights From the HIV Literature

Life expectancy among HIV-infected (HIV+) individuals has improved dramatically with effective antiretroviral therapy. Consequently, chronic diseases such as end-stage liver and kidney disease are growing causes of morbidity and mortality. HIV+ individuals can have excellent outcomes after solid organ transplantation, and the need for transplantation in this population is increasing. However, there is a significant organ shortage, and HIV+ individuals experience higher mortality rates on transplant waitlists. In South Africa, the use of organs from HIV+ deceased donors (HIVDD) has been successful, but until recently federal law prohibited this practice in the United States. With the recognition that organs from HIVDD could fill a critical need, the HIV Organ Policy Equity (HOPE) Act was passed in November 2013, reversing the federal ban on the use of HIV+ donors for HIV+ recipients. In translating this policy into practice, the biologic risks of using HIV+ donors need to be carefully considered. In this mini-review, we explore relevant aspects of HIV virology, antiretroviral treatment, drug resistance, opportunistic infections and HIV-related organ dysfunction that are critical to a transplant team considering HIV-to-HIV transplantation.

Antiretroviral drugs for prevention of mother-to-child transmission: pharmacologic considerations for a public health approach

OBJECTIVE

Efavirenz-based antiretroviral therapy is recommended for prevention of mother-to-child transmission of HIV with two programmatic options: lifelong therapy for all women or treatment until cessation of breastfeeding. However, the risk of HIV resistance emerging after discontinuing efavirenz-based antiretroviral therapy is unclear. We review present knowledge surrounding the emergence of resistance after stopping efavirenz-based antiretroviral regimens.

DESIGN

An expert review.

METHODS

A literature review was conducted to identify studies assessing risk for emergence of efavirenz-related resistance following discontinuation of efavirenz-based antiretroviral regimens containing either lamivudine and zidovudine or tenofovir disoproxil fumarate and lamivudine. Discontinuation strategies including the use of 'pharmacologic tails' are discussed in the light of what is known about the pharmacology of the drugs.

RESULTS

We found no head-to-head comparisons between zidovudine, lamivudine and efavirenz and tenofovir disoproxil fumarate, lamivudine and efavirenz. The risk for HIV resistance exists, even with a 5-7 day tail of zidovudine and lamivudine. For tenofovir disoproxil fumarate, lamivudine and efavirenz, we found no clinical data to inform a recommendation for a tail.

CONCLUSION

In order to prevent emergence of resistance, a tail of at least 2 weeks in duration may be required when discontinuing efavirenz in a regimen containing zidovudine and lamivudine. Studies are needed to characterize the risk of resistance among women who discontinue tenofovir disoproxil fumarate, lamivudine and efavirenz.

Measuring turnover of SIV DNA in resting CD4+ T cells using pyrosequencing: implications for the timing of HIV eradication therapies

Resting CD4+ T cells are a reservoir of latent HIV-1. Understanding the turnover of HIV DNA in these cells has implications for the development of eradication strategies. Most studies of viral latency focus on viral persistence under antiretroviral therapy (ART). We studied the turnover of SIV DNA resting CD4+ T cells during active infection in a cohort of 20 SIV-infected pigtail macaques. We compared SIV sequences at two Mane-A1*084:01-restricted CTL epitopes using serial plasma RNA and resting CD4+ T cell DNA samples by pyrosequencing, and used a mathematical modeling approach to estimate SIV DNA turnover. We found SIV DNA turnover in resting CD4+ T cells was slow in animals with low chronic viral loads, consistent with the long persistence of latency seen under ART. However, in animals with high levels of chronic viral replication, turnover was high. SIV DNA half-life within resting CD4 cells correleated with viral load (p = 0.0052) at the Gag KP9 CTL epitope. At a second CTL epitope in Tat (KVA10) there was a trend towards an association of SIV DNA half-life in resting CD4 cells and viral load (p = 0.0971). Further, we found that the turnover of resting CD4+ T cell SIV DNA was higher for escape during early infection than for escape later in infection (p = 0.0084). Our results suggest viral DNA within resting CD4 T cells is more labile and may be more susceptible to reactivation/eradication treatments when there are higher levels of virus replication and during early/acute infection.

Impact of antiretroviral drugs in pregnant women and their children in Africa: HIV resistance and treatment outcomes

The global community has committed itself to eliminating new pediatric HIV infections by 2015 and improving maternal, newborn, and child health and survival in the context of HIV. Such objectives require regimens to prevent mother-to-child transmission (pMTCT) which, while being highly efficacious, protect the efficacy of future first-line antiretroviral therapy (ART). Major obstacles to eliminating vertical transmissions globally include low rates of adherence to ART and non-completion of the 'pMTCT cascade' due to programmatic and structural challenges faced by healthcare systems in low-income countries. Providing all pregnant women with lifelong ART regardless of CD4 count/disease stage (Option B+) could be the most effective option to prevent both HIV transmission and resistance, assuming adherence is successfully maintained. This strategy is more likely to achieve sustained undetectable HIV viremia, does not involve ART interruptions, is simpler to implement, and is cost-effective. Where Option B+ is not available, options A (short course zidovudine with single-dose nevirapine and an ARV "tail") and B (combination ART during pregnancy and breastfeeding, with ART cessation after weaning in women not qualifying for ART for their own health) are also efficacious, highly cost-effective and associated with infrequent resistance selection if taken properly.

Successful isolation of infectious and high titer human monocyte-derived HIV-1 from two subjects with discontinued therapy

Background

HIV-1 DNA in blood monocytes is considered a viral source of various HIV-1 infected tissue macrophages, which is also known as “Trojan horse” hypothesis. However, whether these DNA can produce virions has been an open question for years, due to the inability of isolating high titer and infectious HIV-1 directly from monocytes.

Results

In this study, we demonstrated successful isolation of two strains of M-HIV-1 (1690 M and 1175 M) from two out of four study subjects, together with their in vivo controls, HIV-1 isolated from CD4+ T-cells (T-HIV-1), 1690 T and 1175 T. All M- and T- HIV-1 isolates were detected CCR5-tropic. Both M- HIV-1 exhibited higher levels of replication in monocyte-derived macrophages (MDM) than the two T- HIV-1. Consistent with our previous reports on the subject 1175 with late infection, compartmentalized env C2-V3-C3 sequences were identified between 1175 M and 1175 T. In contrast, 1690 M and 1690 T, which were isolated from subject 1690 with relatively earlier infection, showed homogenous env C2-V3-C3 sequences. However, multiple reverse transcriptase (RT) inhibitor resistance-associated variations were detected in the Gag-Pol region of 1690 M, but not of 1690 T. By further measuring HIV DNA intracellular copy numbers post-MDM infection, 1690 M was found to have significantly higher DNA synthesis efficiency than 1690 T in macrophages, indicating a higher RT activity, which was confirmed by AZT inhibitory assays.

Conclusions

These results suggested that the M- and T- HIV-1 are compartmentalized in the two study subjects, respectively. Therefore, we demonstrated that under in vitro conditions, HIV-1 infected human monocytes can productively release live viruses while differentiating into macrophages.

Frequency and factors associated with adherence to and completion of combination antiretroviral therapy for prevention of mother to child transmission in western Kenya

Introduction

The objective of this analysis was to identify points of disruption within the prevention of mother-to-child transmission (PMTCT) continuum from combination antiretroviral therapy (CART) initiation until delivery.

Methods

To address this objective, the electronic medical records of all antiretroviral-naïve adult pregnant women who were initiating CART for PMTCT between January 2006 and February 2009 within the Academic Model Providing Access To Healthcare (AMPATH), western Kenya, were reviewed. Outcomes of interest were clinician-initiated change or stop in regimen, disengagement from programme (any, early, late) and self-reported medication adherence. Disengagement was categorized as early disengagement (any interval of greater than 30 days between visits but returning to care prior to delivery) or late disengagement (no visit within 30 days prior to the date of delivery). The association between covariates and the outcomes of interest were assessed using bivariate (Kruskal-Wallis test for continuous variables and the Chi-square test for categorical variables) and multivariate logistic regression analysis.

Results

A total of 4284 antiretroviral-naïve pregnant women initiated CART between January 2006 and February 2009. The majority of women (89%) reported taking all of their medication at every visit. There were 18 (0.4%) deaths reported. Clinicians discontinued CART in 10 patients (0.7%) while 1367 (31.9%) women disengaged from care. Of those disengaging, 404 (29.6%) disengaged early and 963 (70.4%) late. In the multivariate model, the odds of disengagement decreased with increasing age (odds ratio [OR] 0.982; confidence interval [CI] 0.966–0.998) and increasing gestational age at CART initiation (OR 0.925; CI 0.909–0.941). Women receiving care at a district hospital (OR 0.794; CI 0.644–0.980) or tuberculosis medication (OR 0.457; CI 0.202–0.935) were less likely to disengage. The odds of disengagement were higher in married women (OR 1.277; CI 1.034–1.584). The odds of early disengagement decreased with increasing age at CART initiation (OR 0.902; CI 0.881–0.924). The odds of late disengagement decreased with increasing age at CART initiation (OR 0.936; CI 0.917–0.956). While they increased with higher CD4 counts at CART-initiation (OR 1.001; CI 1.000–1001) and in married women (OR 1.297; CI 1.000–1.695)

Conclusions

In a PMTCT programme embedded in an antiretroviral treatment programme with an active outreach department, the majority (67.4%) of women remained engaged and received uninterrupted prenatal CART.

An "escape clock" for estimating the turnover of SIV DNA in resting CD4⁺ T cells

Persistence of HIV DNA presents a major barrier to the complete control of HIV infection under current therapies. Most studies suggest that cells with latently integrated HIV decay very slowly under therapy. However, it is much more difficult to study the turnover and persistence of HIV DNA during active infection. We have developed an “escape clock” approach for measuring the turnover of HIV DNA in resting CD4+ T cells. This approach studies the replacement of wild-type (WT) SIV DNA present in early infection by CTL escape mutant (EM) strains during later infection. Using a strain-specific real time PCR assay, we quantified the relative amounts of WT and EM strains in plasma SIV RNA and cellular SIV DNA. Thus we can track the formation and turnover of SIV DNA in sorted resting CD4+ T cells. We studied serial plasma and PBMC samples from 20 SIV-infected Mane-A*10 positive pigtail macaques that have a signature Gag CTL escape mutation. In animals with low viral load, WT virus laid down early in infection is extremely stable, and the decay of this WT species is very slow, consistent with findings in subjects on anti-retroviral medications. However, during active, high level infection, most SIV DNA in resting cells was turning over rapidly, suggesting a large pool of short-lived DNA produced by recent infection events. Our results suggest that, in order to reduce the formation of a stable population of SIV DNA, it will be important either to intervene very early or intervene during active replication.

New treatments for HIV have proved very successful at controlling viral replication and preventing the onset of AIDS. However, these treatments must be continued for life, because if they are stopped the virus rapidly ‘rebounds’ to its original levels. The reason for this rebound is the existence of a population of viruses that lie dormant inside cells during treatment, and reactivate as soon as treatment is stopped. This ‘latent virus’ is extremely long-lived under drug therapy conditions, and therefore presents a major barrier to viral eradication. However, very little is known about the survival and reactivation of latently infected cells during ongoing infection, because virus is being formed and destroyed all the time. We have developed a novel ‘escape clock’ approach to measure how long viral DNA lasts in monkeys. We find that, in the setting of low viral load, the lifespan of infected cells is very long, whereas during active infection there is a surprisingly high turnover of viral DNA within resting CD4 T cells. We believe this is due to high level of immune activation when there is a high level of replicating virus. This result may have important implications for the optimal timing of drug treatment.

Comparison of resistance mutation patterns in historical plasma HIV RNA genotypes with those in current proviral HIV DNA genotypes among extensively treated patients with suppressed replication

OBJECTIVES

Heavily treatment-experienced patients with good virological control could be at risk of virological failure on switching to a new regimen if pre-existing drug resistance is not taken into account. We examined whether genotyping based on cellular HIV-1 DNA during controlled viraemia identifies resistance mutations detected in plasma HIV-1 RNA during treatment with previous antiretroviral regimens.

PATIENTS AND METHODS

All 169 patients enrolled in the Agence Nationale de Recherche sur le SIDA (ANRS) 138-intEgrase inhibitor MK_0518 to Avoid Subcutaneous Injections of EnfuviRtide (EASIER) trial had already received three antiretroviral drug classes [nucleoside reverse transcriptase inhibitor (NRTI), nonnucleoside reverse transcriptase inhibitor (NNRTI) and protease inhibitor (PI)] and had plasma HIV-1 RNA<400 copies/ml at baseline. The results of previous resistance genotyping of plasma HIV-1 RNA in individual patients were compared with those of resistance genotyping of whole-blood HIV-1 DNA at randomization.

RESULTS

A median of 4 plasma RNA genotypes were available for the 169 patients. The median numbers of resistance mutations in HIV-1 RNA and DNA were, respectively, 5 and 4 for NRTIs, 2 and 1 for NNRTIs, and 10 and 8 for PIs. The difference was significant for all three drug classes (P=0.001). Resistance to at least one antiretroviral drug was detected exclusively in HIV-1 RNA or in DNA in 63% and 13% of patients for NRTI, 47% and 1% of patients for NNRTI, and 50% and 7% of patients for PI, respectively.

CONCLUSION

This study shows that, among highly treatment-experienced patients on effective highly active antiretroviral therapy, resistance genotyping of HIV-1 DNA detects fewer resistance mutations than previous analyses of HIV-1 RNA. These results have implications for patient management and for the design of switch studies.

The effect of sample handling on cross sectional HIV incidence testing results

Objective(s)

To determine if mishandling prior to testing would make a sample from a chronically infected subject appear recently infected when tested by cross-sectional HIV incidence assays.

Methods

Serum samples from 31 subjects with chronic HIV infection were tested. Samples were subjected to different handling conditions, including incubation at 4°C, 25°C and 37°C, for 1, 3, 7 or 15 days prior to testing. Samples were also subjected to 1,3, 7 and 15 freeze-thaw cycles prior to testing. Samples were tested using the BED capture enzyme immuno assay (BED-CEIA), Vironostika-less sensitive (V-LS), and an avidity assay using the Genetic Systems HIV-1/HIV-2 plus O EIA (avidity assay).

Results

Compared to the sample that was not subjected to any mishandling conditions, for the BED-CEIA, V-LS and avidity assay, there was no significant change in test results for samples incubated at 4°C or 25°C prior to testing. No impact on test results occurred after 15 freeze-thaw cycles. A decrease in assay results was observed when samples were held for 3 days or longer at 37°C prior to testing.

Conclusions

Samples can be subjected up to 15 freeze-thaw cycles without affecting the results the BED-CEIA, Vironostika-LS, or avidity assays. Storing samples at 4°C or 25°C for up to fifteen days prior to testing had no impact on test results. However, storing samples at 37°C for three or more days did affect results obtained with these assays.

Slower clearance of nevirapine resistant virus in infants failing extended nevirapine prophylaxis for prevention of mother-to-child HIV transmission

Nevirapine resistance mutations arise commonly following single or extended-dose nevirapine (ED-NVP) prophylaxis to prevent mother-to-child transmission (PMTCT) of human immunodeficiency virus (HIV), but decay within 6-12 months of single-dose exposure. Use of ED-NVP prophylaxis in infants is expected to rise, but data on decay of nevirapine resistance mutations in infants in whom ED-NVP failed remain limited. We assessed, in Ethiopian infants participating in the Six-Week Extended Nevirapine (SWEN) Trial, the prevalence and persistence of nevirapine resistance mutations at 6 and 12 months following single-dose or up to 6 weeks of ED-NVP, and correlated their presence with the timing of infection and the type of resistance mutations. Standard population genotyping followed by high-throughput cloning were done on dried blood spot samples collected during the trial. More infants who received ED-NVP had nevirapine resistance detected by standard population genotyping (high frequencies) at age 6 months compared with those who received single-dose nevirapine (SD-NVP) (58% of 24 vs. 26% of 19, respectively; p = 0.06). Moreover, 56% of ED-NVP-exposed infants with nevirapine resistance at age 6 months still had nevirapine resistance mutations present at high frequencies at age 1 year. Infants infected before 6 weeks of age who received either SD- or ED-NVP were more likely to have Y181C or K103N; these mutations were also more likely to persist at high frequencies through 1 year of age. HIV-infected infants in whom ED-NVP prophylaxis fails are likely to experience delayed clearance of nevirapine-resistant virus in the first year of life, which in turn places them at risk for early selection of multidrug-resistant HIV after initial therapy with nonnucleoside reverse transcriptase inhibitor-based regimens.

Efavirenz-based combination antiretroviral therapy after peripartum single-dose nevirapine

Single-dose nevirapine (sdNVP) reduces mother-to-child HIV transmission, but induces NVP resistance and subsequent NVP-based combination antiretroviral therapy (cART) may fail. Some resistance mutations affect NVP more than efavirenz (EFV). We evaluated virological suppression of EFV-based cART in women after sdNVP. A retrospective analysis matched 107 women who had received sdNVP within the 24 months before cART (cases) with women who had never received sdNVP (controls). By total cohort (intention-to-continue treatment) at week 96, 65% of cases and 73% of controls had a viral load (VL) <400 copies/mL and 63% of cases and 64% of controls had VL <25 copies/mL. At weeks 48 and 96, women starting cART less than six months after sdNVP (n = 20) had VL <400 copies/mL of 90% and 75%, respectively compared with 90% and 70%, respectively, for controls. Overall 172 (80%) women reached week 96. EFV-based cART, in field conditions, was effective for women after sdNVP, even within six months of sdNVP.

Emergence and persistence of minor drug-resistant HIV-1 variants in Ugandan women after nevirapine single-dose prophylaxis

Background

Nevirapine (NVP) single-dose is still a widely used antiretroviral prophylaxis for the prevention of vertical HIV-1 transmission in resource-limited settings. However, the main disadvantage of the Non-nucleoside Reverse Transcriptase Inhibitor (NNRTI) NVP is the rapid selection of NVP-resistant virus with negative implications for subsequent NNRTI-based long-term antiretroviral therapy (ART). Here, we analysed the emergence of drug-resistant HIV-1 including minor variants in the early phase after NVP single-dose prophylaxis and the persistence of drug-resistant virus over time.

Methods and Findings

NVP-resistant HIV-1 harbouring the K103N and/or Y181C resistance mutations in the HIV-1 reverse transcriptase gene was measured from 1 week up to 18 months after NVP single-dose prophylaxis in 29 Ugandan women using allele-specific PCR assays capable of detecting drug-resistant variants representing less than 1% of the whole viral population. In total, drug-resistant HIV-1 was identified in 18/29 (62%) women; rates increased from 18% to 38% and 44% at week 1, 2, 6, respectively, and decreased to 18%, 25%, 13% and 4% at month 3, 6, 12 and 18, respectively. The proportion of NVP-resistant virus of the total viral population was significantly higher in women infected with subtype D (median 40.5%) as compared to subtype A (median 1.3%; p = 0.032, Mann-Whitney U test). 33% of resistant virus was not detectable at week 2 but was for the first time measurable 6–12 weeks after NVP single-dose prophylaxis. Three (10%) women harboured resistant virus in proportions >10% still at month 6.

Conclusions

Current WHO guidelines recommend an additional postnatal intake of AZT and 3TC for one week to avoid NVP resistance formation. Our findings indicate that a 1-week medication might be too short to impede the emergence of NVP resistance in a substantial proportion of women. Furthermore, subsequent NNRTI-based ART should not be started earlier than 12 months after NVP single-dose prophylaxis.

Advances in prevention of mother-to-child HIV transmission: the international perspectives

We have sufficient knowledge and unprecedented access to global resources to dramatically reduce the transmission of HIV-1 from mother to children worldwide. Most transmission occurs during delivery and after birth through breastfeeding. For this reason, efforts to interrupt transmission have focused on peripartum period and safe infant feeding. This includes the use of antiretroviral therapy, elective cesarean section, avoidance of breastfeeding, and exclusive breastfeeding. This review summarizes recent studies and new international development on the prevention of mother-to-child HIV transmission. Prevention of mother-to-child transmission of HIV should now be integrated as part of basic maternal and child health services.

Induction therapy with protease-inhibitors modifies the effect of nevirapine resistance on virologic response to nevirapine-based HAART in children

BACKGROUND

Nevirapine resistance after failed prophylaxis to prevent mother-to-child human immunodeficiency virus (HIV) transmission can compromise subsequent nevirapine-based highly active antiretroviral therapy (HAART).

METHODS

Nevirapine-exposed children who achieved virologic suppression with lopinavir/ritonavir-based induction HAART before switch to nevirapine-based HAART or who continued the lopinavir/ritonavir regimen were studied. Nevirapine-resistant HIV was quantified (≥ 1% frequency) in plasma before therapy and archived in peripheral blood mononuclear cells after induction HAART with ultradeep pyrosequencing. The primary endpoint was virologic failure (confirmed viremia ≥ 1000 copies/mL by 52 weeks) on nevirapine-based HAART, and Receiver operating characteristic analysis identified threshold levels of resistance associated with failure.

RESULTS

Nevirapine resistance mutations were detected in plasma at a median frequency of 25.6% in 41 (33%) of 124 children starting HAART at median 9 months of age. After a median nine months of induction HAART, nevirapine-resistant HIV remained archived in cells in 59 (61%) of 96 children (median 13.6% of cells). The threshold frequency of nevirapine resistance in plasma most predictive of virologic failure on nevirapine-based HAART was 25%. Children maintaining resistance before therapy at or above this threshold frequency had a 3.5 fold higher risk of failure (95% confidence interval, 1.1-10.8) than children without detectable plasma resistance. In contrast, virologic failure was not independently associated with age, resistance in plasma below 25% frequencies, or archived in cells.

CONCLUSIONS

Virologic suppression with lopinavir/ritonavir-based HAART in nevirapine-exposed children raises the threshold level of resistance at which reuse of nevirapine-based therapy is compromised. Standard genotyping may allow identification of children likely to benefit from an induction-switch approach.

Suboptimal nevirapine steady-state pharmacokinetics during intrapartum compared with postpartum in HIV-1-seropositive Ugandan women

BACKGROUND

Conflicting data exist regarding the effect of pregnancy on steady-state nevirapine pharmacokinetics (PK), although steady-state nevirapine concentrations during pregnancy have never been characterized in sub-Saharan Africa.

METHODS

This was a longitudinal intensive PK study in Ugandan pregnant women receiving nevirapine-based antiretroviral therapy. Participants underwent intensive 12-hour PK sampling during the second trimester (T2; n = 4), third trimester (T3; n = 15) and 6 weeks postpartum (PP; n = 15). HIV-1 RNA was performed within 2 weeks of each visit. Nevirapine C12 above 3000 ng/mL was classified as optimal based on the suggested value for therapeutic drug monitoring.

RESULTS

The pharmacokinetics of nevirapine were influenced by pregnancy, demonstrated by a 20% reduction in the maximum concentration, minimum concentration (C12), and area under the curve between T3 and PP visits (P = 0.001, P = 0.011 and P = 0.005, respectively). Ten subjects (66.7%) had C12 values <3000 ng/mL during T3. Of these participants, 7 partcipant's C12 concentrations increased to >3000 ng/mL during the PP visit. HIV-1 RNA were <1000 copies per milliliter at T3 and <400 copies per milliliter at PP in all patients.

CONCLUSIONS

Nevirapine exposure was reduced in Ugandan women during their third trimester compared with the same women PP, however, HIV RNA remained <1000 copies per milliliter. The long-term impact of intermittent suboptimal nevirapine concentrations during pregnancy is unknown.

Higher levels of Zidovudine resistant HIV in the colon compared to blood and other gastrointestinal compartments in HIV infection

Background

The gut-associated lymphoid tissue (GALT) is the largest lymphoid organ infected by human immunodeficiency virus type 1 (HIV-1). It serves as a viral reservoir and host-pathogen interface in infection. This study examined whether different parts of the gut and peripheral blood lymphocytes (PBL) contain different drug-resistant HIV-1 variants.

Methods

Gut biopsies (esophagus, stomach, duodenum and colon) and PBL were obtained from 8 HIV-1 infected preHAART (highly active antiretroviral therapy) patients at three visits over 18 months. Patients received AZT, ddI or combinations of AZT/ddI. HIV-1 Reverse transcriptase (RT)-coding sequences were amplified from viral DNA obtained from gut tissues and PBL, using nested PCR. The PCR fragments were cloned and sequenced. The resulting sequences were subjected to phylogenetic analyses, and antiretroviral drug mutations were identified.

Results

Phylogenetic and drug mutation analyses revealed differential distribution of drug resistant mutations in the gut within patients. The level of drug-resistance conferred by the RT sequences was significantly different between different gut tissues and PBL, and varied with antiretroviral therapy. The sequences conferring the highest level of drug-resistance to AZT were found in the colon.

Conclusion

This study confirms that different drug-resistant HIV-1 variants are present in different gut tissues, and it is the first report to document that particular gut tissues may select for drug resistant HIV-1 variants.

Addition of 7 days of zidovudine plus lamivudine to peripartum single-dose nevirapine effectively reduces nevirapine resistance postpartum in HIV-infected mothers in Malawi

BACKGROUND

We assessed whether 7 days of zidovudine + lamivudine postpartum with single-dose nevirapine at labor decreases nevirapine resistance in HIV-infected women in Malawi.

METHODS

HIV-infected pregnant women receiving intrapartum single-dose nevirapine and 7 days of zidovudine + lamivudine (n = 132) and women receiving intrapartum single-dose nevirapine alone (n = 66) were followed from an antenatal visit through 6 weeks postpartum. Plasma specimens at 2 and 6 weeks postpartum were tested for genotypic resistance to nevirapine by population sequencing and sensitive real-time polymerase chain reaction. Poisson regression was used to determine predictors of postpartum nevirapine resistance.

RESULTS

Median HIV RNA was similar at entry (4.27 log vs. 4.35 log, P = 0.87), differed at 2 weeks postpartum (2.67 log vs. 3.58 log, P < 0.0001) but not at 6 weeks postpartum (4.49 log vs. 4.40 log, P = 0.79), between single-dose nevirapine/zidovudine + lamivudine and single-dose nevirapine groups, respectively. Nevirapine resistance, measured by population sequencing and sensitive real-time polymerase chain reaction, was significantly less common in those receiving single-dose nevirapine/zidovudine + lamivudine compared with single-dose nevirapine, respectively, at 2 weeks [10% (4 of 40) vs. 74% (31 of 42), P < 0.0001] and 6 weeks postpartum [10% (11 of 115) vs. 64% (41 of 64), P < 0.0001; adjusted relative risk = 0.18, 95% confidence interval (0.10 to 0.34)].

CONCLUSIONS

The significant decrease in nevirapine resistance conferred by 1 week of zidovudine + lamivudine should help policymakers optimize peripartum HIV prophylaxis recommendations.

Estimating frequencies of minority nevirapine-resistant strains in chronically HIV-1-infected individuals naive to nevirapine by using stochastic simulations and a mathematical model

Nevirapine forms the mainstay of our efforts to curtail the pediatric AIDS epidemic through prevention of mother-to-child transmission of HIV-1. A key limitation, however, is the rapid selection of HIV-1 strains resistant to nevirapine following the administration of a single dose. This rapid selection of resistance suggests that nevirapine-resistant strains preexist in HIV-1 patients and may adversely affect outcomes of treatment. The frequencies of nevirapine-resistant strains in vivo, however, remain poorly estimated, possibly because they exist as a minority below current assay detection limits. Here, we employ stochastic simulations and a mathematical model to estimate the frequencies of strains carrying different combinations of the common nevirapine resistance mutations K103N, V106A, Y181C, Y188C, and G190A in chronically infected HIV-1 patients naïve to nevirapine. We estimate the relative fitness of mutant strains from an independent analysis of previous competitive growth assays. We predict that single mutants are likely to preexist in patients at frequencies ( approximately 0.01% to 0.001%) near or below current assay detection limits (>0.01%), emphasizing the need for more-sensitive assays. The existence of double mutants is subject to large stochastic variations. Triple and higher mutants are predicted not to exist. Our estimates are robust to variations in the recombination rate, cellular superinfection frequency, and the effective population size. Thus, with 10(7) to 10(8) infected cells in HIV-1 patients, even when undetected, nevirapine-resistant genomes may exist in substantial numbers and compromise efforts to prevent mother-to-child transmission of HIV-1, accelerate the failure of subsequent antiretroviral treatments, and facilitate the transmission of drug resistance.

Nevirapine resistance by timing of HIV type 1 infection in infants treated with single-dose nevirapine

BACKGROUND

In women, single-dose nevirapine for prophylaxis against mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) selects for nevirapine-resistant HIV-1, which subsequently decays rapidly. We hypothesized that the selection, acquisition, and decay of nevirapine-resistant HIV-1 differs in infants, varying by the timing of HIV-1 infection.

METHODS

We conducted a prospective, observational study of 740 Mozambican infants receiving single-dose nevirapine prophylaxis and determined the timing of infection and concentrations of nevirapine-resistant HIV-1 over time.

RESULTS

Infants with established in utero infection had a high rate (87.0%) of selection of nevirapine-resistant HIV-1 mutants, which rapidly decayed to undetectable levels. The few without nevirapine resistance received zidovudine with single-dose nevirapine and/or their mothers took alternative antiretroviral drugs. Infants with acute in utero infection had a lower rate of nevirapine-resistant HIV-1 (33.3%; P = .006, compared with established in utero infection), but mutants persisted over time. Infants with peripartum infection also had a lower rate of nevirapine-resistant HIV-1 (38.1%; P = .001, compared with established in utero infection) but often acquired 100% mutant virus that persisted over time (P = .017, compared with established in utero infection).

CONCLUSIONS

The detection and persistence of nevirapine-resistant HIV-1 in infants after single-dose nevirapine therapy vary by the timing of infection and the antiretroviral regimen. In infants with persistent high-level nevirapine-resistant HIV-1, nevirapine-based antiretroviral therapy is unlikely to ever be efficacious because of concentrations in long-lived viral reservoirs. However, the absence or decay of nevirapine-resistant HIV-1 in many infants suggests that nevirapine antiretroviral therapy may be effective if testing can identify these individuals.

Effects of highly active antiretroviral therapy duration and regimen on risk for mother-to-child transmission of HIV in Johannesburg, South Africa

BACKGROUND

Limited information exists about effects of different highly active antiretroviral therapy (HAART) regimens and duration of regimens on mother-to-child transmission (MTCT) of HIV among women in Africa who start treatment for advanced immunosuppression.

METHODS

Between January 2004 to August 2008, 1142 women were followed at antenatal antiretroviral clinics in Johannesburg. Predictors of MTCT (positive infant HIV DNA polymerase chain reaction at 4-6 weeks) were assessed with multivariate logistic regression.

RESULTS

Mean age was 30.2 years (SD = 5.0) and median baseline CD4 count was 161 cells per cubic millimeter (SD = 84.3). HAART duration at time of delivery was a mean 10.7 weeks (SD = 7.4) for the 85% of women who initiated treatment during pregnancy and 93.4 weeks (SD = 37.7) for those who became pregnant on HAART. Overall MTCT rate was 4.9% (43 of 874), with no differences detected between HAART regimens. MTCT rates were lower in women who became pregnant on HAART than those initiating HAART during pregnancy (0.7% versus 5.7%; P = 0.01). In the latter group, each additional week of treatment reduced odds of transmission by 8% (95% confidence interval: 0.87 to 0.99, P = 0.02).

CONCLUSIONS

Late initiation of HAART is associated with increased risk of MTCT. Strategies are needed to facilitate earlier identification of HIV-infected women.

Resistance considerations in sequencing of antiretroviral therapy in low-middle income countries with currently available options

PURPOSE OF REVIEW

Access to antiretroviral therapy (ART) has been scaled-up in low-middle income countries (LMICs), where the majority of the world's HIV-1-infected population is living. Concerns towards the emergence and spread of HIV-1 drug resistance exist, given the lack of virological monitoring which may give rise to accumulation of resistance as well as the use of suboptimal ART in pregnant women with the aim to reduce perinatal transmission. Knowledge of the prevalence of transmitted and emerging drug resistance as well as its specific patterns is of help in guiding the selection of appropriate ART types and sequencing strategies.

RECENT FINDINGS

Whereas transmitted drug resistance in LMIC is still limited, resistance in pregnant women as a consequence of suboptimal ART for the prevention of vertical transmission is frequent and dependent on viral subtype and load. Accumulation of drug resistance during first-line ART depends on the frequency of monitoring, whereas mutational patterns are influenced by type of ART and, partly, viral subtype.

SUMMARY

Optimized ART for prevention of mother-to-child transmission and closer monitoring of ART programs with the inclusion of viral load may help reducing unnecessary development of HIV drug resistance in LMIC and preserve the limited available treatment options.

Use of antiretrovirals during pregnancy and breastfeeding in low-income and middle-income countries

PURPOSE OF REVIEW

The purpose of the study was to review recent evidence on the use of antiretrovirals during pregnancy and breastfeeding in low-income and middle-income settings.

RECENT FINDINGS

Access to antiretroviral prophylaxis strategies for HIV-infected pregnant women has increased globally, but two-thirds of women in need still do not receive even the simplest regimen for the prevention of mother-to-child transmission of HIV, and most pregnant women in need of antiretroviral treatment do not receive it. The use of combination antiretroviral treatment in pregnancy in low-resource settings is safe and effective, and increasing evidence supports starting ongoing antiretroviral treatment at a CD4 cell count below 350/microl in pregnant women. The use of appropriate short-course antiretroviral prophylactic regimens is effective for prevention of mother-to-child transmission of HIV in women with higher CD4 cell counts. New data on the use of antiretroviral prophylaxis to prevent transmission through breastfeeding demonstrate that both maternal antiretroviral treatment and extended infant prophylaxis are effective.

SUMMARY

Antiretroviral use in pregnancy can benefit mothers in need of treatment and reduce the risk of mother-to-child transmission. Emerging evidence of the effectiveness of antiretroviral prophylaxis in preventing transmission through breastfeeding is encouraging and likely to influence practice in the future.