Optimization of the oligonucleotide ligation assay, a rapid and inexpensive test for detection of HIV-1 drug resistance mutations, for non-North American variants

Ligation-based assay for variant typing without sequencing: Application to SARS-CoV-2 variants of concern

BACKGROUND

COVID-19 prevalence has remained high throughout the pandemic with intermittent surges, due largely to the emergence of genetic variants, demonstrating the need for more accessible sequencing technologies for strain typing.

METHODS

A ligation-based typing assay was developed to detect known variants of severe acute respiratory syndrome virus 2 (SARS-CoV-2) by identifying the presence of characteristic single-nucleotide polymorphisms (SNPs). General principles for extending the strategy to new variants and alternate diseases with SNPs of interest are described. Of note, this strategy leverages commercially available reagents for assay preparation, as well as standard real-time polymerase chain reaction (PCR) instrumentation for assay performance.

RESULTS

The assay demonstrated a combined sensitivity and specificity of 96.6% and 99.5%, respectively, for the classification of 88 clinical samples of the Alpha, Delta, and Omicron variants relative to the gold standard of viral genome sequencing. It achieved an average limit of detection of 7.4 × 10⁴ genome copies/mL in contrived nasopharyngeal samples. The ligation-based strategy performed robustly in the presence of additional polymorphisms in the targeted regions of interest as shown by the sequence alignment of clinical samples.

CONCLUSIONS

The assay demonstrates the potential for robust variant typing with performance comparable with next-generation sequencing without the need for the time delays and resources required for sequencing. The reduced resource dependency and generalizability could expand access to variant classification information for pandemic surveillance.

Point-of-Care Tests for HIV Drug Resistance Monitoring: Advances and Potentials

HIV/AIDS is a global public health crisis that is yet to be contained. Effective management of HIV drug resistance (HIVDR) supported by close resistance monitoring is essential in achieving the WHO 95-95-95 targets, aiming to end the AIDS epidemic by 2030. Point-of-care tests (POCT) enable decentralized HIVDR testing with a short turnaround time and minimal instrumental requirement, allowing timely initiation of effective antiretroviral therapy (ART) and regimen adjustment as needed. HIVDR POCT is of particular significance in an era when ART access is scaling up at a global level and enhanced HIVDR monitoring is urgently needed, especially for low-to-middle-income countries. This article provides an overview of the currently available technologies that have been applied or potentially used in HIVDR POCT. It may also benefit the continued research and development efforts toward more innovative HIVDR diagnostics.

Magnetic Bead Processing Enables Sensitive Ligation-Based Detection of HIV Drug Resistance Mutations

HIV develops single nucleotide polymorphisms (SNPs), some of which lead to drug resistance mutations (DRMs) that prevent therapeutic viral suppression. Genomic sequencing enables healthcare professionals to select effective combination antiretroviral therapy (ART) to achieve and maintain viral suppression. However, sequencing technologies, which are resource-intensive, are limited in their availability. This report describes the first step toward a highly specific ligation-based SNP discrimination method with endpoint PCR detection, which is more suitable for resource-limited clinics. The approach is based on magnetic bead processing to maximize reaction product transfer and minimize the carryover of incompatible buffer for three consecutive enzymatic reactions─reverse transcription (RT), oligonucleotide ligation assay (OLA), and PCR. The method improved PCR detection following RT → OLA by 8.06 cycles (∼250-fold) compared to direct pipette processing and detected between 103 and 104 RNA copies per reaction. In studies with synthesized nucleic acids based on the well-studied HIV mutation, K103N, the assay successfully differentiated between wild-type and mutant for RNA targets with high specificity. With further development, this design provides a pathway for SNP detection with more accessible PCR instrumentation and is a step toward a self-contained processing approach that incorporates the SNP specificity of the ligation reaction for more effective clinical management of DRMs in resource-constrained settings.

Rapid Near Point-of-Care Assay for HLA-B*57:01 Genotype Associated with Severe Hypersensitivity Reaction to Abacavir

The nucleoside reverse transcriptase inhibitor abacavir (ABC) is used commonly to treat young children with HIV infection and is a component of the fixed-dose-combination Triumeq^®. ABC can trigger a severe hypersensitivity reaction in people who are homozygous or heterozygous for HLA-B*57:01. Testing for HLA-B*57:01 before ABC initiation is standard-of-care in high-resource settings, but current tests are costly or difficult to access in resource-limited settings. To address these gaps, we developed an inexpensive simple-to-use rapid assay to detect HLA-B*57:01. We designed and optimized a multiplexed polymerase chain reaction (PCR) to amplify HLA-B*57 subtypes and the human beta-globin gene; employed probes and ligation to specifically tag the HLA-B*57:01 allele with biotin. Tagged-ligated products were detected by immunocapture in an enzyme-linked immunosorbent assay plate or lateral flow strip. Cell lines with known HLA genotypes were used to optimize the assay. The optimized assay was then compared with genotypes of clinical specimens (n = 60) determined by sequencing, with specimens enriched for individuals with HLA-B*57:01. The optimized assay utilizes 40-min 35-cycle multiplex PCR for B*57 and beta-globin; 20-min ligation reaction; and 15-min detection. Evaluation of the HLA-B*57:01 oligonucleotide ligation assay using clinical specimens had a sensitivity of 100% (n = 27/27 typed as B*57:01) and specificity of 100% (n = 33/33 typed as non-B*57:01) by visual interpretation of lateral flow strips. The cost is US$5.96/specimen. This rapid and economical assay accurately detects HLA-B*57:01 in clinical specimens. Use of this assay could expand access to HLA-B*57:01 genotyping and facilitate safe same-day initiation of ABC-based treatment.

Near point-of-care, point-mutation test to detect drug resistance in HIV-1: a validation study in a Mexican cohort

OBJECTIVE

Pretreatment HIV-drug resistance (PDR, HIVDR) to non-nucleoside reverse transcriptase inhibitors (NNRTIs) is increasing globally. NNRTIs continue to be used as first-line antiretroviral therapy (ART) in some communities due to the cost of dolutegravir-based ART or dolutegravir-associated adverse events. A simplified version of the oligonucleotide ligation assay (OLA) - 'OLA-Simple' - is a low-cost, near point-of-care assay that provides ready-to-use lyophilized reagents and reports HIVDR mutations as colored lines on lateral flow strips. Our objective was to design and validate OLA-Simple for a Mexican cohort.

DESIGN

OLA-Simple probes to detect K65R, K103N/S, Y181C, M184V, and G190A were optimized for HIV Mexican sequences. Sixty clinical plasma specimens were analyzed by OLA-Simple by technicians blinded to Illumina-MiSeq sequences, and HIVDR results were compared.

METHODS

Plasma RNA was tested using OLA-Simple kits. OLA-Simple lateral flow strips were read by in-house software, and were classified as mutant or wild-type at each codon. The comparison of results by OLA-Simple and Miseq was used to generate receiver-operating characteristic curves.

RESULTS

OLA-Simple PCR amplified 59 of 60 specimens and successfully genotyped 287 of 295 codons, with eight of 295 (2.7%) indeterminate results. Compared to MiSeq, OLA-Simple gave five of 295 (1.7%) false-positive and four of 295 (1.4%) false-negative results. Excluding indeterminate results, OLA-Simple classified mutant with an accuracy of 97.4 and 98.8% when using thresholds at 10 and 25% mutant within an individual's HIV quasispecies, respectively.

CONCLUSIONS

Compared to MiSeq, OLA-Simple detected HIVDR with high sensitivity and accuracy. OLA-Simple could expand access to affordable and rapid HIVDR testing to guide appropriate ART choices in populations using NNRTI-based ART.

Cost-effectiveness analysis of pre-ART HIV drug resistance testing in Kenyan women

BACKGROUND

The prevalence of pre-treatment drug resistance (PDR) to non-nucleoside reverse-transcriptase inhibitor (NNRTI) agents is increasing in sub-Saharan Africa, which may decrease the effectiveness of efavirenz-based antiretroviral therapy (ART) programs. However, due to recent safety concerns, there has been hesitancy to replace efavirenz-based ART with dolutegravir in women of reproductive potential. Our objective was to evaluate whether PDR testing for women not initiating dolutegravir-based ART would be a cost-effective strategy to address the challenges posed by PDR.

METHODS

We developed an HIV drug resistance model that simulates the emergence and transmission of resistance mutations, calibrated to the Kenyan epidemic. We modeled three care strategies for PDR testing among women not initiating dolutegravir-based ART: no PDR testing, PDR testing with a low-cost point mutation assay, known as oligonucleotide ligation assay (OLA), and PDR testing with consensus sequencing. Using a health sector perspective, this model was used to evaluate the health outcomes, lifetime costs, and cost-effectiveness under each strategy over a 15-year time horizon starting in 2019.

FINDINGS

OLA and CS PDR testing were projected to have incremental cost-effectiveness ratios (ICER) of $10,741/QALY gained and $134,396/QALY gained, respectively, which are not cost-effective by national income standards. Viral suppression rates among women at 12 months after ART initiation were 87·8%, 89·0%, and 89·3% with no testing, OLA testing, and CS testing, respectively. PDR testing with OLA and CS were associated with a 0.5% and 0.6% reduction in incidence rate compared to no PDR testing. Initial PDR prevalence among women was 13.1% in 2019. By 2034, this prevalence was 17·6%, 17·4%, and 17·3% with no testing, OLA testing, and CS testing, respectively.

INTERPRETATION

PDR testing for women is unlikely to be cost-effective in Kenya whether one uses a low-cost assay, such as OLA, or consensus sequencing.

FUNDING

National Institutes of Health, Gilead Sciences.

Evaluation of the management of pretreatment HIV drug resistance by oligonucleotide ligation assay: a randomised controlled trial

BACKGROUND

Although experts have recommended testing for pretreatment drug resistance (PDR) before antiretroviral therapy (ART) initiation, there is little evidence to support its implementation. We aimed to establish whether an inexpensive point mutation assay can improve virological suppression by identifying PDR to guide drug selection for ART in a lower-middle income country.

METHODS

Investigators did an open-label, randomised controlled trial at three HIV treatment sites in Kenya: two in Nairobi and one in rural Maseno. Individuals (aged ≥2 years) were eligible to participate if they were confirmed HIV-seropositive, qualified for first-line ART, planned to reside in the area for more than 1 year, and provided informed consent. We randomly assigned participants (1:1) to either PDR testing by oligonucleotide ligation assay (OLA) to guide selection of ART or to standard of care, which did not include OLA testing. The OLA-guided therapy group had pre-ART peripheral blood mononuclear cells evaluated for drug resistance to non-nucleoside reverse transcriptase inhibitor (NNRTI) at codons Lys103Asn, Tyr181Cys, Gly190Ala, and to lamivudine at Met184Val, and when at least one drug-resistant codon was detected in a participant's pre-ART specimen, clinicians were directed to prescribe protease inhibitor-based second-line ART. Those without detected resistance and those who were randomised to standard of care received NNRTI-based first-line ART. The primary outcome was plasma HIV-1 RNA of at least 400 copies per mL at 4, 8, or 12 months after ART initiation, which defined virological failure, assessed in all participants who received treatment (data were censored for those lost-to-follow-up or who died). The study has been completed and is registered with ClinicalTrials.gov, NCT01898754.

FINDINGS

We screened 1198 participants between May 28, 2013, and Nov 4, 2014, of whom 991 (83%) were enrolled (492 received OLA and 495 received standard of care; four did not begin treatment). 93 participants (prevalence 9·4%) had PDR (95% CI 7·7-11·4). 34 (8·5%) of 400 participants in the OLA group had virological failure at month 12 of ART (95% CI 6·0-11·7) compared with 39 (9·7%) of 402 (7·0-13·0) in the standard-of-care group (log-rank p=0·26). Among participants with PDR, virological failure was lower in the OLA-guided therapy group than in the standard-of-care group: five (14%) of 35 compared with 13 (50%) of 26; p=0·0020). Among those prescribed NNRTI-based ART, participants given efavirenz were less likely to have virological failure than were those receiving nevirapine (odds ratio 0·37, 95% CI 0·22-0·62; p<0·0001). The OLA-guided therapy group had 39 serious non-lethal adverse events and 34 deaths. The standard-of-care group had 34 severe adverse events and 43 deaths, differences that were not significant. Adverse events judged to potentially be due to ART were few and similar between groups, with 17 (16%) in the OLA-guided therapy group and 16 (16%) in the standard-of-care group (p=0·90).

INTERPRETATION

Our finding that OLA testing for PDR reduced virological failure in only those with specific PDR mutations suggests that PDR poses less of a risk for virological failure than that predicted by past prevalence estimates, and that the value of PDR testing to reduce virological failure should be assessed for antiretroviral treatment regimens.

FUNDING

US National Institutes of Health.

OLA-Simple: A software-guided HIV-1 drug resistance test for low-resource laboratories

Background

HIV drug resistance (HIVDR) testing can assist clinicians in selecting treatments. However, high complexity and cost of genotyping assays limit routine testing in settings where HIVDR prevalence has reached high levels.

Methods

The oligonucleotide ligation assay (OLA)-Simple kit was developed for detection of HIVDR against first-line non-nucleoside/nucleoside reverse transcriptase inhibitors and validated on 672 codons (168 specimens) from subtypes A, B, C, D, and AE. The kit uses dry reagents to facilitate assay setup, lateral flow devices for visual HIVDR detections, and in-house software with an interface for guiding users and analyzing results.

Findings

HIVDR analysis of specimens by OLA-Simple compared to Sanger sequencing revealed 99.6 ± 0.3% specificity and 98.2 ± 0.9% sensitivity, and compared to high-sensitivity assays, 99.6 ± 0.6% specificity and 86.2 ± 2.5% sensitivity, with 2.6 ± 0.9% indeterminate results. OLA-Simple was performed more rapidly compared to Sanger sequencing (<4 h vs. 35–72 h). Forty-one untrained volunteers blindly tested two specimens each with 96.8 ± 0.8% accuracy.

Interpretation

OLA-Simple compares favorably with HIVDR genotyping by Sanger and sensitive comparators. Instructional software enabled inexperienced, first-time users to perform the assay with high accuracy. The reduced complexity, cost, and training requirements of OLA-Simple could improve access to HIVDR testing in low-resource settings and potentially allow same-day selection of appropriate antiretroviral therapy.

Fund

USA National Institutes of Health R01; the Clinical and Retrovirology Research Core and the Molecular Profiling and Computational Biology Core of the UW CFAR; Seattle Children's Research Institute; UW Holloman Innovation Challenge Award; Pilcher Faculty Fellowship.

Pretreatment HIV Drug Resistance and Virologic Outcomes to First-Line Antiretroviral Therapy in Peru

Access to nucleoside reverse transcriptase inhibitor (NRTI) and non-nucleoside reverse transcriptase inhibitor (NNRTI) first-line antiretroviral therapy (ART) for HIV has been increasing in Peru since a national ART program was initiated in 2004. Between 2007 and 2009, we found a 1% prevalence of pre-ART HIV drug resistance (PDR) among antiretroviral (ARV)-naive Peruvians. Given that PDR has been associated with virologic failure (VF) of ART, in 2014-2015 we enrolled a follow-up cohort at the same institution to determine whether the rate of transmitted resistance had increased and compared virologic outcomes of those with and without PDR. Blood specimens from ARV-naive individuals were assessed for PDR to NNRTI-based ART by an oligonucleotide ligation assay (OLA) sensitive to 2% mutant within an individual's HIV quasispecies at reverse transcriptase codons M41L, K65R, K103N, Y181C, M184V, and G190A, and by Sanger consensus sequencing (CS). Rates of VF (plasma HIV RNA >200 copies/mL) were compared between those with and without PDR. Among 122 ARV-naive adults, PDR was detected by OLA in 17 (13.9%) adults. Compared with the 2007-2009 cohort, the proportion with PDR at OLA codons was significantly increased (p < .001). A total of 11 of 19 OLA mutations conferring high-level drug resistance were also detected by CS, and 8 additional participants had mutations encoding low-level resistance detected by CS for a total of 25 participants (20.5%). VF at month 6 of NNRTI-ART appeared greater in participants with versus without PDR [4/18 (22.2%) vs. 3/71 (4.2%); p = .03]. An increasing prevalence of PDR was detected among ARV-naive Peruvians. Studies are needed to determine risks of specific PDR mutations.

Implementation of a point mutation assay for HIV drug resistance testing in Kenya

OBJECTIVES

An increasing prevalence of HIV pretreatment drug resistance (PDR) has been observed in Africa, which could decrease the effectiveness of antiretroviral therapy (ART) programs. We describe our experiences, the costs and challenges of implementing an oligonucleotide ligation assay (OLA) for management of PDR in Nairobi, Kenya.

DESIGN

An observational report of the implementation of OLA in a Kenyan laboratory for a randomized clinical trial evaluating whether onsite use of OLA in individuals initiating ART would decrease rates of virologic failure.

METHODS

Compared detection of mutations and proportion of mutants in participants' viral quasispecies by OLA in Kenya vs. Seattle. Reviewed records of laboratory workflow and performance of OLA. Calculated the costs of laboratory set-up and of performing the OLA based on equipment purchase receipts and supplies and labor utilization, respectively.

RESULTS

OLA was performed on 492 trial participants. Weekly batch-testing of median of seven (range: 2-13) specimens provided test results to Kenyan clinicians within 10-14 days of sample collection at a cost of US$ 42 per person tested. Cost of laboratory setup was US$ 32 594. Challenges included an unreliable local supply chain for reagents and the need for an experienced molecular biologist to supervise OLA performance.

CONCLUSION

OLA was successfully implemented in a Kenyan research laboratory. Cost was twice that projected because of fewer than predicted specimens per batch because of slow enrollment. OLA is a potential simple, low-cost method for PDR testing in resource-limited settings (RLS). Ongoing work to develop a simplified kit could improve future implementation of OLA in RLS.

Current Status of Point-of-Care Testing for Human Immunodeficiency Virus Drug Resistance

Healthcare delivery has advanced due to the implementation of point-of-care testing, which is often performed within minutes to hours in minimally equipped laboratories or at home. Technologic advances are leading to point-of-care kits that incorporate nucleic acid-based assays, including polymerase chain reaction, isothermal amplification, ligation, and hybridization reactions. As a limited number of single-nucleotide polymorphisms are associated with clinically significant human immunodeficiency virus (HIV) drug resistance, assays to detect these mutations have been developed. Early versions of these assays have been used in research. This review summarizes the principles underlying each assay and discusses strategic needs for their incorporation into the management of HIV infection.

Genetic Variability of HIV-1 for Drug Resistance Assay Development

A hybridization-based point-of-care (POC) assay for HIV-1 drug resistance would be useful in low- and middle-income countries (LMICs) where resistance testing is not routinely available. The major obstacle in developing such an assay is the extreme genetic variability of HIV-1. We analyzed 27,203 reverse transcriptase (RT) sequences from the Stanford HIV Drug Resistance Database originating from six LMIC regions. We characterized the variability in a 27-nucleotide window surrounding six clinically important drug resistance mutations (DRMs) at positions 65, 103, 106, 181, 184, and 190. The number of distinct codons at each DRM position ranged from four at position 184 to 11 at position 190. Depending on the mutation, between 11 and 15 of the 24 flanking nucleotide positions were variable. Nonetheless, most flanking sequences differed from a core set of 10 flanking sequences by just one or two nucleotides. Flanking sequence variability was also lower in each LMIC region compared with overall variability in all regions. We also describe an online program that we developed to perform similar analyses for mutations at any position in RT, protease, or integrase.

Simplified Paper Format for Detecting HIV Drug Resistance in Clinical Specimens by Oligonucleotide Ligation

Human immunodeficiency virus (HIV) is a chronic infection that can be managed by antiretroviral treatment (ART). However, periods of suboptimal viral suppression during lifelong ART can select for HIV drug resistant (DR) variants. Transmission of drug resistant virus can lessen or abrogate ART efficacy. Therefore, testing of individuals for drug resistance prior to initiation of treatment is recommended to ensure effective ART. Sensitive and inexpensive HIV genotyping methods are needed in low-resource settings where most HIV infections occur. The oligonucleotide ligation assay (OLA) is a sensitive point mutation assay for detection of drug resistance mutations in HIV pol. The current OLA involves four main steps from sample to analysis: (1) lysis and/or nucleic acid extraction, (2) amplification of HIV RNA or DNA, (3) ligation of oligonucleotide probes designed to detect single nucleotide mutations that confer HIV drug resistance, and (4) analysis via oligonucleotide surface capture, denaturation, and detection (CDD). The relative complexity of these steps has limited its adoption in resource-limited laboratories. Here we describe a simplification of the 2.5-hour plate-format CDD to a 45-minute paper-format CDD that eliminates the need for a plate reader. Analysis of mutations at four HIV-1 DR codons (K103N, Y181C, M184V, and G190A) in 26 blood specimens showed a strong correlation of the ratios of mutant signal to total signal between the paper CDD and the plate CDD. The assay described makes the OLA easier to perform in low resource laboratories.

Oligonucleotide ligation assay detects HIV drug resistance associated with virologic failure among antiretroviral-naive adults in Kenya

BACKGROUND

Transmitted drug resistance (TDR) is increasing in some areas of Africa. Detection of TDR may predict virologic failure of first-line nonnucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral therapy (ART). We evaluated the utility of a relatively inexpensive oligonucleotide ligation assay (OLA) to detect clinically relevant TDR at the time of ART initiation.

METHODS

Pre-ART plasmas from ART-naive Kenyans initiating an NNRTI-based fixed-dose combination ART in a randomized adherence trial conducted in 2006 were retrospectively analyzed by OLA for mutations conferring resistance to NNRTI (K103N, Y181C, and G190A) and lamivudine (M184V). Post-ART plasmas were analyzed for virologic failure (≥1000 copies/mL) at 6-month intervals over 18-month follow-up. Pre-ART plasmas of those with virologic failure were evaluated for drug resistance by consensus and 454-pyrosequencing.

RESULTS

Among 386 participants, TDR was detected by OLA in 3.89% (95% confidence interval: 2.19 to 6.33) and was associated with a 10-fold higher rate of virologic failure (hazard ratio: 10.39; 95% confidence interval: 3.23 to 32.41; P < 0.001) compared with those without TDR. OLA detected 24 TDR mutations (K103N: n = 13; Y181C: n = 5; G190A: n = 3; M184V: n = 3) in 15 subjects (NNRTI: n = 15; 3TC: n = 3). Among 51 participants who developed virologic failure, consensus sequencing did not detect additional TDR mutations conferring high-level resistance, and pyrosequencing only detected additional mutations at frequencies <2%. Mutant frequencies <2% at ART initiation were significantly less likely to be found at the time of virologic failure compared with frequencies ≥2% (22% vs. 63%; P < 0.001).

CONCLUSIONS

Detection of TDR by a point mutation assay may prevent the use of suboptimal ART.

Single-agent tenofovir versus combination emtricitabine plus tenofovir for pre-exposure prophylaxis for HIV-1 acquisition: an update of data from a randomised, double-blind, phase 3 trial

BACKGROUND

Antiretroviral pre-exposure prophylaxis (PrEP), with daily oral tenofovir disoproxil fumarate or tenofovir disoproxil fumarate in combination with emtricitabine, has been shown to be efficacious for HIV-1 prevention. Although the use of more than one antiretroviral agent is essential for effective HIV-1 treatment, more than one agent might not be required for effective prophylaxis. We assessed the efficacy of single-agent tenofovir disoproxil fumarate relative to combination emtricitabine plus tenofovir disoproxil fumarate as PrEP.

METHODS

We did a randomised, double-blind, placebo-controlled three-group phase 3 trial of daily oral tenofovir disoproxil fumarate and emtricitabine plus tenofovir disoproxil fumarate PrEP in HIV-1 uninfected individuals in heterosexual HIV-1 serodiscordant couples from Kenya and Uganda. After an interim review, the trial's placebo group was discontinued and thereafter the active groups were continued, and participants initially randomly assigned to placebo were offered rerandomisation in a 1:1 ratio to tenofovir disoproxil fumarate or emtricitabine plus tenofovir disoproxil fumarate as PrEP. The primary endpoints were HIV-1 seroconversion and safety. This trial is registered with ClinicalTrials.gov, number NCT00557245.

FINDINGS

4410 (99·6%) of 4427 couples received tenofovir disoproxil fumarate or emtricitabine plus tenofovir disoproxil fumarate and were followed up for HIV-1 acquisition. Of 52 incident HIV-1 infections, 31 occurred in individuals assigned tenofovir disoproxil fumarate (incidence 0·71 cases per 100 person-years) and 21 were in those assigned emtricitabine plus tenofovir disoproxil fumarate (0·48 cases per 100 person-years); HIV-1 incidence in the placebo group until discontinuation was two cases per 100 person-years. HIV-1 prevention efficacy with emtricitabine plus tenofovir disoproxil fumarate was not significantly different from that of tenofovir disoproxil fumarate alone (hazard ratio [HR] 0·67, 95% CI 0·39-1·17; p=0·16). Detection of tenofovir in plasma samples, compared with no detection and as measured in seroconverters and a subset of non-seroconverters, was associated with an 85% relative risk reduction in HIV-1 acquisition for the tenofovir disoproxil fumarate group (HR 0·15, 95% CI 0·06-0·37; p<0·0001) and 93% for the emtricitabine plus tenofovir disoproxil fumarate group (0·07, 0·02-0·23; p<0·0001). No significant differences were noted in the frequency of deaths, serious adverse events, or serum creatinine and phosphorus abnormalities between the two groups.

INTERPRETATION

These results do not rule out the potential for a slight difference in HIV-1 protection with tenofovir disoproxil fumarate compared with emtricitabine plus tenofovir disoproxil fumarate, but show that once-daily oral tenofovir disoproxil fumarate or emtricitabine plus tenofovir disoproxil fumarate regimens both provide high protection against HIV-1 acquisition in heterosexual men and women.

FUNDING

Bill & Melinda Gates Foundation and US National Institutes of Health.

Optimization of the oligonucleotide ligation assay for the detection of nevirapine resistance mutations in Zimbabwean Human Immunodeficiency Virus type-1 subtype C

An oligonucleotide ligation assay (OLA) designed to detect Human Immunodeficiency Virus type-1 (HIV)-drug-resistance to the nevirapine (NVP) selected mutations K103N, Y181C, V106M and G190A was used to evaluate 200 archived dried blood spots (DBS) from infected infants participating in the Zimbabwean Early Infant Diagnosis (EID) Program. Consensus sequencing of specimens with indeterminate OLA results was performed to identify genetic sequence polymorphisms that appeared to compromise performance of the OLA. When consistent patterns of polymorphisms were observed the probes were redesigned, and DBS specimens with indeterminate OLA results were retested with the new Zimbabwe-specific (ZW) probes. OLA results obtained in Zimbabwe were compared to repeat testing in a US reference laboratory. 188/200 (94%) DBS yielded polymerase chain reaction (PCR) amplification of HIV pol. ZW probes reduced indeterminate OLA results from 5.2% to 2.8% of codons evaluated (p=0.02), with 98.2% concordance between results obtained in the Zimbabwean and US laboratories. Optimization of OLA probes to accommodate polymorphisms in regional HIV variants improved OLA performance, and comparison to the USA results showed successful implementation of the OLA in Zimbabwe for detection of NVP resistance mutations in DBS specimens.

Lack of resistance to integrase inhibitors among antiretroviral-naive subjects with primary HIV-1 infection, 2007-2013

BACKGROUND

US guidelines recommend genotyping for persons newly diagnosed with HIV infection to identify transmitted drug resistance mutations associated with decreased susceptibility to nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors and protease inhibitors. To date, testing for integrase strand transfer inhibitor (INSTI) mutations has not been routinely recommended. We aimed to evaluate the prevalence of transmitted INSTI mutations among persons with primary HIV-1 infection in Seattle, WA, USA.

METHODS

Persons with primary HIV-1 infection have enrolled in an observational cohort at the University of Washington Primary Infection Clinic since 1992. We performed a retrospective analysis of plasma specimens collected prospectively from the 82 antiretroviral-naive subjects who were enrolled from 2007-2013, after FDA-approval of the first INSTI. Resistance testing was performed by consensus sequencing.

RESULTS

Specimens for analysis had been obtained a median of 24 (IQR 18-41, range 8-108) days after the estimated date of HIV-1 infection. All subjects were infected with HIV-1 subtype B except for one subject infected with subtype C. Consensus sequencing identified no subjects with major INSTI mutations (T66I, E92Q, G140S, Y143C/H/R, S147G, Q148H/K/R, N155H). Using exact binomial CIs, the upper bound of the 95% CI was 4.4%.

CONCLUSIONS

Although our sample size was small, this study does not support the need at this time to evaluate integrase mutations as part of routine consensus sequencing among persons newly diagnosed with HIV-1 infection. However, it is likely that the prevalence of transmitted INSTI mutations may increase with the recent commercial introduction of additional INSTIs and presumably greater INSTI use among persons living with HIV-1.

Validation of an oligonucleotide ligation assay for quantification of human immunodeficiency virus type 1 drug-resistant mutants by use of massively parallel sequencing

Global HIV treatment programs need sensitive and affordable tests to monitor HIV drug resistance. We compared mutant detection by the oligonucleotide ligation assay (OLA), an economical and simple test, to massively parallel sequencing. Nonnucleoside reverse transcriptase inhibitor (K103N, V106M, Y181C, and G190A) and lamivudine (M184V) resistance mutations were quantified in blood-derived plasma RNA and cell DNA specimens by OLA and 454 pyrosequencing. A median of 1,000 HIV DNA or RNA templates (range, 163 to 1,874 templates) from blood specimens collected in Mozambique (n = 60) and Kenya (n = 51) were analyzed at 4 codons in each sample (n = 441 codons assessed). Mutations were detected at 75 (17%) codons by OLA sensitive to 2.0%, at 71 codons (16%; P = 0.78) by pyrosequencing using a cutoff value of ≥ 2.0%, and at 125 codons (28%; P < 0.0001) by pyrosequencing sensitive to 0.1%. Discrepancies between the assays included 15 codons with mutant concentrations of ∼2%, one at 8.8% by pyrosequencing and not detected by OLA, and one at 69% by OLA and not detected by pyrosequencing. The latter two cases were associated with genetic polymorphisms in the regions critical for ligation of the OLA probes and pyrosequencing primers, respectively. Overall, mutant concentrations quantified by the two methods correlated well across the codons tested (R(2) > 0.8). Repeat pyrosequencing of 13 specimens showed reproducible detection of 5/24 mutations at <2% and 6/6 at ≥ 2%. In conclusion, the OLA and pyrosequencing performed similarly in the quantification of nonnucleoside reverse transcriptase inhibitor and lamivudine mutations present at >2% of the viral population in clinical specimens. While pyrosequencing was more sensitive, detection of mutants below 2% was not reproducible.

Simultaneous and sensitive detection of human immunodeficiency virus type 1 (HIV) drug resistant genotypes by multiplex oligonucleotide ligation assay

Oligonucleotide ligation assay (OLA) is a highly specific and relatively simple method to detect point mutations encoding HIV-1 drug-resistance, which can detect mutants comprising ≥2-5% of the viral population. Nevirapine (NVP), tenofovir (TDF) and lamivudine (3TC) are antiretroviral (ARV) drugs used worldwide for treatment of HIV infection and prevention of mother-to-child-transmission. Adapting the OLA to detect multiple mutations associated with HIV resistance to these ARV simultaneously would provide an efficient tool to monitor drug resistance in resource-limited settings. Known proportions of mutant and wild-type plasmids were used to optimize a multiplex OLA for detection of K103N, Y181C, K65R, and M184V in HIV subtypes B and C, and V106M and G190A in subtype C. Simultaneous detection of two mutations was impaired if probes annealed to overlapping regions of the viral template, but was sensitive to ≥2-5% when testing codons using non-overlapping probes. PCR products from HIV-subtype B- and C-infected individuals were tested by multiplex-OLA and compared to results of single-codon OLA. Multiplex-OLA detected mutations at codon pairs 103/181, 106/190 and 65/184 reliably when compared to singleplex-OLA in clinical specimens. The multiplex-OLA is sensitive and specific and reduces the cost of screening for NVP, TDF and/or 3TC resistance.

Improvement of the oligonucleotide ligation assay for detection of the M184V drug-resistant mutation in patients infected with human immunodeficiency virus type 1 subtype CRF01_AE

Methods based on genetic sequencing to monitor drug-resistance mutations in human immunodeficiency virus type 1 (HIV-1) require expensive instruments and are only capable of detecting mutant strains comprising >20% of virus populations. The National Institutes of Health's AIDS Research and Reference Reagent Program (NIH ARRRP) makes available a probe-based method, an oligonucleotide ligation assay (OLA-ARRRP), which is less expensive and more sensitive than sequencing to detect such mutations for HIV-1 subtype B. In this study, an OLA was designed to detect the Methionine to Valine mutation at codon 184 (M184V) of the reverse transcriptase (RT) gene in the circulating recombinant form AE strain of HIV-1 (HIV-1 CRF01_AE) common in Thailand, and was evaluated in Thai patients experiencing treatment failure. The subtype-specific OLA-CRF01_AE proved superior to OLA-ARRRP in detecting M184V, although this mutation existed in the genome of the multiple-drug-resistant virus at lower minimal detection levels of 3% prevalence of mutated virus, compared to 50% for OLA-ARRRP. On evaluation using clinical specimens, OLA-CRF01_AE showed excellent agreement with nucleotide sequencing (95.1% overall concordance, kappa>0.79), and the sensitivity was 100% for wild-type and 93.9% for mutant detection at codon 184. The OLA-CRF01_AE also detected M184V mutations in 2.4% (1/42) of specimens that were not detected by sequencing. The indeterminate detection by OLA-CRF01_AE was decreased, from 16.7% to 4.8%, in the samples containing mutant genotype when the strategy using unmodified- as a substitute of the modified-mutant detector probe was applied. Because of their low cost, sensitivity, and ease of use, the OLA-CRF01_AE is an attractive alternative to standard sequencing in resource-limited countries affected by this subtype of HIV-1.

Monitoring of HIV type 1 DNA load and drug resistance in peripheral blood mononuclear cells during suppressive antiretroviral therapy does not predict virologic failure

Our objective was to determine whether monitoring HIV-1 DNA concentration or new resistance mutations in peripheral blood mononuclear cells (PBMCs) during effective antiretroviral therapy (ART) predicts virologic failure. A retrospective analysis used blood specimens and clinical data from three nevirapine containing arms of a four-arm, open-label, randomized trial comparing ART regimens in HIV-1-infected children who had failed mono- or dual-nucleoside therapy. Sensitive assays compared cell-associated HIV-1 DNA concentrations and nevirapine (NVP) and lamivudine (3TC) resistance mutations in children with plasma HIV-1 RNA <400 copies(c)/ml who did or did not experience subsequent virologic failure. Forty-six children were analyzed through the last available follow-up specimen, collected at 48 (n=16) or 96 (n=30) weeks of ART. Thirty-five (76%) had sustained viral suppression and 11 (24%) had plasma viral rebound to ≥ 400 c/ml (virologic failure detected at a median of 36 weeks). HIV-1 DNA levels at baseline, 24, 48, and 96 weeks of ART were similar in children who did vs. did not experience virologic failure (p=0.82). HIV-1 DNA levels did not increase prior to viral rebound. NVP resistance mutations were detected in 91% of subjects in the failure group vs. 3% in the suppressed group (p <0.0001). Among nine evaluable children, NVP mutations were first detected prior to virologic failure in two (22%), at viral rebound in five (56%), and after failure in two (22%) children. HIV-1 DNA concentrations did not predict virologic failure in this cohort. New drug resistance mutations were detected in the PBMCs of a minority of virologically suppressed children who subsequently failed ART.

Transmitted HIV resistance to first-line antiretroviral therapy in Lima, Peru

Transmission of drug-resistant HIV (TDR) has been associated with virologic failure of "first-line," nonnucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral therapy (ART). A national ART program began in Peru in 2004. We evaluated the prevalence of TDR in individuals initiating ART and their virologic outcome during 2 years of ART. HIV-infected, ARV-naive subjects who met criteria to start ART in Lima, Peru were enrolled in a longitudinal observational study between July 2007 and February 2009. Blood plasma and cells obtained prior to ART initiation were assessed for antiretroviral (ARV) resistance by an oligonucleotide ligation assay (OLA) sensitive to 2% mutant at reverse transcriptase (RT) codons K103N, Y181C, G190A, and M184V and a subset by consensus sequencing. A total of 112 participants were enrolled; the mean CD4 was 134 ± 89 cells/μl and the median plasma HIV RNA was 93,556 copies/ml (IQR 62,776-291,364). Drug resistance mutations conferring high-level resistance to ARV were rare, detected in one of 96 (1%) evaluable participants. This subject had the Y181C mutation detected in both plasma and peripheral blood mononuclear cells (PBMCs) at a concentration of 100% by OLA and consensus sequencing; nevertheless nevirapine-ART suppressed her viral replication. Consensus sequencing of 37 (19%) participants revealed multiple polymorphisms that occasionally have been associated with low-level reductions in ARV susceptibility. A low prevalence of TDR was detected among Peruvians initiating ART. Given the increasing availability of ART, continuing surveillance is needed to determine if TDR increases and the mutant codons associated with virologic failure.

Prevalence and impact of minority variant drug resistance mutations in primary HIV-1 infection

Objective

To evaluate minority variant drug resistance mutations detected by the oligonucleotide ligation assay (OLA) but not consensus sequencing among subjects with primary HIV-1 infection.

Design/Methods

Observational, longitudinal cohort study. Consensus sequencing and OLA were performed on the first available specimens from 99 subjects enrolled after 1996. Survival analyses, adjusted for HIV-1 RNA levels at the start of antiretroviral (ARV) therapy, evaluated the time to virologic suppression (HIV-1 RNA<50 copies/mL) among subjects with minority variants conferring intermediate or high-level resistance.

Results

Consensus sequencing and OLA detected resistance mutations in 5% and 27% of subjects, respectively, in specimens obtained a median of 30 days after infection. Median time to virologic suppression was 110 (IQR 62–147) days for 63 treated subjects without detectable mutations, 84 (IQR 56–109) days for ten subjects with minority variant mutations treated with ≥3 active ARVs, and 104 (IQR 60–162) days for nine subjects with minority variant mutations treated with <3 active ARVs (p = .9). Compared to subjects without mutations, time to virologic suppression was similar for subjects with minority variant mutations treated with ≥3 active ARVs (aHR 1.2, 95% CI 0.6–2.4, p = .6) and subjects with minority variant mutations treated with <3 active ARVs (aHR 1.0, 95% CI 0.4–2.4, p = .9). Two subjects with drug resistance and two subjects without detectable resistance experienced virologic failure.

Conclusions

Consensus sequencing significantly underestimated the prevalence of drug resistance mutations in ARV-naïve subjects with primary HIV-1 infection. Minority variants were not associated with impaired ARV response, possibly due to the small sample size. It is also possible that, with highly-potent ARVs, minority variant mutations may be relevant only at certain critical codons.

A comparison of 3 regimens to prevent nevirapine resistance mutations in HIV-infected pregnant women receiving a single intrapartum dose of nevirapine

BACKGROUND

Intrapartum single-dose (SD) nevirapine (NVP) reduces perinatal transmission of human immunodeficiency virus (HIV) infection but selects for NVP-resistant virus, which compromises subsequent NVP-based therapy. A 1-week "tail" of lamivudine and zidovudine after SD-NVP decreases the risk of resistance. We hypothesized that increasing the duration or potency of the tail would further reduce this risk to <10%, using a sensitive assay to measure resistance.

METHODS

HIV-infected pregnant Thai women with a CD4 cell count >250 cells/μL, most receiving zidovudine, were randomized at 28-38 weeks gestation to receive 1 of 3 intrapartum and postpartum regimens: (A) zidovudine plus enteric-coated didanosine plus lopinavir and ritonavir for 7 days, (B) zidovudine plus enteric-coated didanosine for 30 days, or (C) regimen 1 for 30 days. The incidence of NVP resistance mutations at day 10 or week 6 post partum in each arm was compared with that of a historical comparison group who received prenatal zidovudine and SD-NVP. NVP resistance was identified by consensus sequencing and a sensitive oligonucleotide ligation assay (OLA).

RESULTS

At entry, the 169 participants had a median CD4 cell count of 456 cells/μL and an HIV load of 3.49 log(10) copies/mL. The incidence of mutations in each of the 3 P1032 arms was 0% by sequencing and 1.8%, 7.1%, and 5.3% by OLA in arms A, B, and C, respectively, compared with 13.4% by sequencing and 29.4% by OLA in the comparison group (P < .001 for each study arm vs comparison group). Grade 4 anemia developed in 1 woman.

CONCLUSIONS

A 7-day tail of highly active combination therapy or 1 month of dual therapy after SD-NVP prevents most NVP resistance to minimal toxicity.

CLINICAL TRIALS REGISTRATION

The IMPAACT P1032 Clinical Trial is NCT00109590, and the PHPT-2 Clinical Trial is NCT00398684.

Accurate sampling and deep sequencing of the HIV-1 protease gene using a Primer ID

Viruses can create complex genetic populations within a host, and deep sequencing technologies allow extensive sampling of these populations. Limitations of these technologies, however, potentially bias this sampling, particularly when a PCR step precedes the sequencing protocol. Typically, an unknown number of templates are used in initiating the PCR amplification, and this can lead to unrecognized sequence resampling creating apparent homogeneity; also, PCR-mediated recombination can disrupt linkage, and differential amplification can skew allele frequency. Finally, misincorporation of nucleotides during PCR and errors during the sequencing protocol can inflate diversity. We have solved these problems by including a random sequence tag in the initial primer such that each template receives a unique Primer ID. After sequencing, repeated identification of a Primer ID reveals sequence resampling. These resampled sequences are then used to create an accurate consensus sequence for each template, correcting for recombination, allelic skewing, and misincorporation/sequencing errors. The resulting population of consensus sequences directly represents the initial sampled templates. We applied this approach to the HIV-1 protease (pro) gene to view the distribution of sequence variation of a complex viral population within a host. We identified major and minor polymorphisms at coding and noncoding positions. In addition, we observed dynamic genetic changes within the population during intermittent drug exposure, including the emergence of multiple resistant alleles. These results provide an unprecedented view of a complex viral population in the absence of PCR resampling.

Antiretroviral therapy optimisation without genotype resistance testing: a perspective on treatment history based models

Background

Although genotypic resistance testing (GRT) is recommended to guide combination antiretroviral therapy (cART), funding and/or facilities to perform GRT may not be available in low to middle income countries. Since treatment history (TH) impacts response to subsequent therapy, we investigated a set of statistical learning models to optimise cART in the absence of GRT information.

Methods and Findings

The EuResist database was used to extract 8-week and 24-week treatment change episodes (TCE) with GRT and additional clinical, demographic and TH information. Random Forest (RF) classification was used to predict 8- and 24-week success, defined as undetectable HIV-1 RNA, comparing nested models including (i) GRT+TH and (ii) TH without GRT, using multiple cross-validation and area under the receiver operating characteristic curve (AUC). Virological success was achieved in 68.2% and 68.0% of TCE at 8- and 24-weeks (n = 2,831 and 2,579), respectively. RF (i) and (ii) showed comparable performances, with an average (st.dev.) AUC 0.77 (0.031) vs. 0.757 (0.035) at 8-weeks, 0.834 (0.027) vs. 0.821 (0.025) at 24-weeks. Sensitivity analyses, carried out on a data subset that included antiretroviral regimens commonly used in low to middle income countries, confirmed our findings. Training on subtype B and validation on non-B isolates resulted in a decline of performance for models (i) and (ii).

Conclusions

Treatment history-based RF prediction models are comparable to GRT-based for classification of virological outcome. These results may be relevant for therapy optimisation in areas where availability of GRT is limited. Further investigations are required in order to account for different demographics, subtypes and different therapy switching strategies.

Minority variants of drug-resistant HIV

Minor drug-resistant variants exist in every patient infected with human immunodeficiency virus (HIV). Because these minority variants are usually present at very low levels, they cannot be detected and quantified using conventional genotypic and phenotypic tests. Recently, several assays have been developed to characterize these low-abundance drug-resistant variants in the large, genetically complex population that is present in every HIV-infected individual. The most important issue is what results generated by these assays can predict clinical or treatment outcomes and might guide the management of patients in clinical practice. Cutoff values for the detection of these low-abundance viral variants that predict an increased risk of treatment failure should be determined. These thresholds may be specific for each mutation and treatment regimen. In this review, we summarize the attributes and limitations of the currently available detection assays and review the existing information about both acquired and transmitted drug-resistant minority variants.

Association between detection of HIV-1 DNA resistance mutations by a sensitive assay at initiation of antiretroviral therapy and virologic failure

BACKGROUND

Antiretroviral therapy (ART) has become more available throughout the developing world during the past 5 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 human immunodeficiency virus (HIV)-1. There is no simple and efficient method to detect such mutations at the initiation of ART.

METHODS

One hundred eighty-one women who were participating in a clinical trial to prevent mother-to-child transmission and who started NVP-ART after they had received sdNVP or a placebo were included in the study. One hundred copies of each patient's HIV-1 DNA were tested for NVP-resistance point-mutations (K103N, Y181C, and G190A) with a sensitive oligonucleotide ligation assay that was able to detect mutants even at low concentrations (> or = 5% of the viral population). Virologic failure was defined as confirmed plasma HIV-1 RNA >50 copies/mL after 6 to 18 months of NVP-ART.

RESULTS

At initiation of NVP-ART, resistance mutations were identified in 38 (26%) of 148 participants given sdNVP (K103N in 19 [13%], Y181C in 8 [5%], G190A in 28 [19%], and > or = 2 mutations in 15 [10%]), at a median 9.3 months after receipt of sdNVP. The risk of virologic failure was 0.62 (95% confidence interval [CI], 0.46-0.77) in women with > or = 1% resistance mutation, compared with a risk of 0.25 (95% CI, 0.17-0.35) in those without detectable resistance mutations (P < .001). Failure was independently associated with resistance, an interval of <6 months between sdNVP and NVP-ART initiation, and a viral load higher than the median at NVP-ART initiation.

CONCLUSIONS

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

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.

Efficacy and safety of 1-month postpartum zidovudine-didanosine to prevent HIV-resistance mutations after intrapartum single-dose nevirapine

BACKGROUND

Intrapartum single-dose nevirapine plus third trimester maternal and infant zidovudine are essential components of programs to prevent mother-to-child transmission of human immunodeficiency virus (HIV) in resource-limited settings. The persistence of nevirapine in the plasma for 3 weeks postpartum risks selection of resistance mutations to nonnucleoside reverse-transcriptase inhibitors (NNRTIs). We hypothesized that a 1-month zidovudine-didanosine course initiated at the same time as single-dose nevirapine (sdNVP) would prevent the selection of nevirapine-resistance mutations.

METHODS

HIV-infected pregnant women in the PHPT-4 cohort with CD4 cell counts >250 cells/mm3 received antepartum zidovudine from the third trimester until delivery, sdNVP during labor, and a 1-month zidovudine-didanosine course after delivery. These women were matched on the basis of baseline HIV load, CD4 cell count, and duration of antepartum zidovudine to women who received sdNVP in the PHPT-2 trial (control subjects). Consensus sequencing and the more sensitive oligonucleotide ligation assay were performed on samples obtained on postpartum days 7-10, 37-45, and 120 (if the HIV load was >500 copies/mL) to detect K103N/Y181C/G190A mutations.

RESULTS

The 222 PHPT-4 subjects did not differ from matched control subjects in baseline characteristics except for age. The combined group median CD4 cell count was 421 cells/mm3 (interquartile range [IQR], 322-549 cells/mm3), the median HIV load was 3.45 log10 copies/mL (IQR, 2.79-4.00 log10 copies/mL), and the median duration of zidovudine prophylaxis was 10.4 weeks (IQR, 9.1-11.4 weeks). Using consensus sequencing, major NNRTI resistance mutations were detected after delivery in 0% of PHPT-4 subjects and 10.4% of PHPT-2 controls. The oligonucleotide ligation assay detected resistance in 1.8% of PHPT-4 subjects and 18.9% of controls. Major NNRTI resistance mutations were detected by either method in 1.8% of PHPT-4 subjects and 20.7% of controls (P < .001).

CONCLUSIONS

A 1-month postpartum course of zidovudine plus didanosine prevented the selection of the vast majority of NNRTI resistance mutations.

Detection of HIV-1 drug resistance in women following administration of a single dose of nevirapine: comparison of plasma RNA to cellular DNA by consensus sequencing and by oligonucleotide ligation assay

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.

Increased detection of HIV-1 drug resistance at time of diagnosis by testing viral DNA with a sensitive assay

OBJECTIVE

HIV-1 drug resistance has been detected in 8%-24% of recently infected North Americans when assessed by consensus sequencing of plasma. We hypothesized that rates were likely higher but not detected because drug-resistant mutants are transmitted or regressed to levels below the limit of detection by consensus sequencing of HIV-1 RNA.

METHODS

Specimens from antiretroviral-naive individuals recently diagnosed with HIV-1 infection were compared at 15 codons to determine if testing of DNA using a sensitive oligonucleotide ligation assay (OLA) would detect drug resistance mutants not evident by consensus sequencing of serum.

RESULTS

HIV-1 drug resistance at 15 major resistance codons was greater by OLA compared with consensus sequencing: 18 of 104 vs. 12 of 104 individuals (P < or = 0.008) and 33 vs. 18 total mutations (P < or = 0.001); increasing the rate of detection at these 15 codons by 83%. Additional mutations were detected by consensus sequencing at L33, M46, D67, V108, and K219 that were not assessed by OLA.

CONCLUSIONS

The increased detection of drug-resistant HIV-1 by testing peripheral blood cells with a sensitive assay implies that both low and high levels of drug-resistant mutants are transmitted or persist in antiretroviral-naive individuals, suggesting that the clinical relevance of mutants persisting at both levels should be evaluated.