Nucleoside analogue mutations and Q151M in HIV-1 subtype A/E infection treated with nucleoside reverse transcriptase inhibitors

High Rate Multiple Drug Resistances in HIV-Infected Patients Failing Nonnucleoside Reverse Transcriptase Inhibitor Regimens in Thailand, Where Subtype A/E is Predominant

The prevalence of drug resistance was determined among 64 HIV-infected Thai patients who were failed while receiving nonnucleoside reverse transcriptase inhibitor (NNRTI)–based regimens. Eighty-nine percent of patients had 1 or more NNRTI mutation resistances. Almost all patients had resistance to at least 1 nucleoside reverse transcriptase inhibitor (NRTI), and 42% had multiple-NRTI resistance.

Increased risk of Q151M and K65R mutations in patients failing stavudine-containing first-line antiretroviral therapy in Cambodia

Background

Multi-nucleos(t)ide resistance (MNR) mutations including Q151M, K65R mutations, and insertion at codon 69 of HIV-1 reverse transcriptase coding region may confer resistance to all molecules of nucleos(t)ide reverse transcriptase inhibitors (NRTI). The presence of these mutations is an emerging problem compromising non-nucleoside reverse transcriptase inhibitors and protease inhibitors-based therapies. Furthermore, factors associated with selection of these mutations are still not well defined. The current study aimed to evaluate the frequency and to characterize factors associated with the occurrence of multi-nucleos(t)ide resistance mutations among HIV-1 infected patients failing recommended first-line antiretroviral regimens in Cambodia.

Methodology/Principal Finding

This is a retrospective analysis of HIV-1 drug resistance genotyping of 520 HIV-1 infected patients in virological failure (viral load > 250 copies/mL) while on first-line antiretroviral therapy in Cambodia with at least one reverse transcriptase inhibitor resistance associated mutation. Among these 520 patients, a total of 66 subjects (66/520, 12.7%) presented ≥1 MNR mutation, including Q151M, K65R, and Insert69 for 59 (11.3%), 29 (5.6%), and 2 (0.4%) patients, respectively. In multivariate analysis, both Q151M (p = 0.039) and K65R (p = 0.029) mutations were independently associated with current stavudine- compared to zidovudine-use.

Conclusion

Such selection of mutations by stavudine drastically limits the choice of antiretroviral molecules available for second-line therapy in resource-limited settings. This finding supports the World Health Organization’s recommendation for stavudine phase-out.

Multilabel classification for exploiting cross-resistance information in HIV-1 drug resistance prediction

MOTIVATION

Antiretroviral treatment regimens can sufficiently suppress viral replication in human immunodeficiency virus (HIV)-infected patients and prevent the progression of the disease. However, one of the factors contributing to the progression of the disease despite ongoing antiretroviral treatment is the emergence of drug resistance. The high mutation rate of HIV can lead to a fast adaptation of the virus under drug pressure, thus to failure of antiretroviral treatment due to the evolution of drug-resistant variants. Moreover, cross-resistance phenomena have been frequently found in HIV-1, leading to resistance not only against a drug from the current treatment, but also to other not yet applied drugs. Automatic classification and prediction of drug resistance is increasingly important in HIV research as well as in clinical settings, and to this end, machine learning techniques have been widely applied. Nevertheless, cross-resistance information was not taken explicitly into account, yet.

RESULTS

In our study, we demonstrated the use of cross-resistance information to predict drug resistance in HIV-1. We tested a set of more than 600 reverse transcriptase sequences and corresponding resistance information for six nucleoside analogues. Based on multilabel classification models and cross-resistance information, we were able to significantly improve overall prediction accuracy for all drugs, compared with single binary classifiers without any additional information. Moreover, we identified drug-specific patterns within the reverse transcriptase sequences that can be used to determine an optimal order of the classifiers within the classifier chains. These patterns are in good agreement with known resistance mutations and support the use of cross-resistance information in such prediction models.

CONTACT

dominik.heider@uni-due.de

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Long-term lopinavir/ritonavir monotherapy in HIV-infected children

BACKGROUND

Long-term data are limited on lopinavir/ritonavir monotherapy (mLPV/r) as a treatment simplification strategy in virologically suppressed children.

METHODS

Children with confirmed plasma HIV viral load (VL) <50 copies/mL while receiving double protease inhibitors (dPI) were switched to mLPV/r therapy. Virologic failure (VF) was defined as 2 consecutive VL ≥ 500 or 3 consecutive VL ≥ 50 copies/mL. dPI was resumed within 4 weeks in children with VF. Primary endpoint was the proportion of children with VL < 50 copies/mL while still receiving mLPV/r at week 144.

RESULTS

Forty children were enrolled; 90% were receiving LPV/r + saquinavir and 10% LPV/r + indinavir before simplifying to mLPV/r. Median age was 11.7 years; 50% were female. Median CD4% was 27%. Four (10%) had VL > 50 copies/mL at entry. At week 144, the proportion of children still receiving mLPV/r who had VL < 50 copies/mL was 22 of 40 (55%). The proportion of all children with VL < 50 copies/mL at week 144 was 33 of 40 (82.5%). Among 16 children who had VF and resumed dPI, 11 (69%) achieved VL < 50 copies/mL at week 144. No children with VF had major LPV/r mutations. Having detectable VL at entry and adherence by pill count <95% for >3 times at any visits during the study period significantly predicted VF on mLPV/r (both P = 0.025). The proportion of children with elevated total cholesterol (>200 mg/dL) decreased from 65% at baseline to 40% at week 144 (P = 0.007).

CONCLUSIONS

About half of children maintained virologic suppression on mLPV/r for almost 3 years. VF was common but the majority achieved suppression after resuming dPI and none had major LPV/r mutations. mLPV/r should only be considered for simplified maintenance therapy if frequent VL monitoring to detect VF is available.

HIV-1 drug resistance at virological failure versus immunological failure among patients failing first-line antiretroviral therapy in a resource-limited setting

Antiretroviral treatment failure has been defined by immunological failure (IF) in some resource-limited settings whereas defining by virological failure (VF) has been widely used in developed countries. There is limited comparison of the levels of HIV-1 drug resistance between using VF and IF for the diagnosis of treatment failure. A retrospective cohort study was conducted among HIV-1-infected patients failing first-line antiretroviral therapy (ART). Of 95 patients, median CD4 and HIV-1 RNA were 158 cells/mm(3) and 10,200 copies/mL, respectively. Patients in the IF group had higher HIV-1 RNA than those in VF group (23,820 versus 9510 copies/mL, P = 0.008). Nucleoside reverse transcriptase inhibitor (NRTI)-, non-NRTI- and protease inhibitor-resistance-associated mutations (RAMs) were observed in 57.9%, 94.7% and 5.3%, respectively. Q151M, a multidrug RAM, was more commonly observed in the IF group (14.8% versus 2.9%, P = 0.032). Using IF to diagnose treatment failure is associated with higher HIV-1 RNA levels and a higher rate of Q151M, which can limit the options for second-line ART.

A randomized comparison of second-line lopinavir/ritonavir monotherapy versus tenofovir/lamivudine/lopinavir/ritonavir in patients failing NNRTI regimens: the HIV STAR study

BACKGROUND

Data informing the use of boosted protease inhibitor (PI) monotherapy as second-line treatment are limited. There are also no randomized trials addressing treatment options after failing first-line non-nucleoside reverse transcriptase inhibitor (NNRTI)-regimens.

METHODS

HIV-infected subjects ≥18 years, with HIV RNA≥1,000 copies/ml while using NNRTI plus 2 NRTIs, and naive to PIs were randomized to lopinavir/ritonavir (LPV/r) 400/100 mg twice daily monotherapy (mono-LPV/r) or tenofovir disoproxil fumarate (TDF) once daily plus lamivudine (3TC) twice daily plus LPV/r 400/100 mg twice daily (TDF/3TC/LPV/r) at nine sites in Thailand. The primary outcome was time-weighted area under curve (TWAUC) change in HIV RNA over 48 weeks. The a priori hypothesis was that the mono-LPV/r arm would be considered non-inferior if the upper 95% confidence limit in TWAUC mean difference was ≤0.5 log(10) copies/ml.

RESULTS

The intention-to-treat (ITT) population comprised 195 patients (mono-LPV/r n=98 and TDF/3TC/LPV/r n=97): male 58%, baseline mean (sd) age of 38 (7) years, CD4(+) T-cell count of 204 (135) cells/mm(3) and HIV RNA of 4.1 (0.6) log(10) copies/ml. The majority had HIV-1 recombinant CRF01_AE infection, and thymidine analogue mutation (TAM)-2 was 3× more common than TAM-1. At 48 weeks, the difference in TWAUC HIV RNA between arms was 0.15 (95% CI -0.04, 0.33) log(10) copies/ml, consistent with our definition of non-inferiority. However, the proportion with HIV RNA<50 copies/ml was significantly lower in the mono-LPV/r arm: 61% versus 83% (ITT, P<0.01). Baseline HIV RNA≥5 log(10) copies/ml (P<0.001) and mono-LPV/r use (P=0.003) were predictors of virological failure. Baseline genotypic sensitivity scores ≥2 and TAM-2 were associated with better virological control in subjects treated with the TDF-containing regimen.

CONCLUSIONS

In PI-naive patients failing NNRTI-based first-line HAART, mono-LPV/r had a significantly lower proportion of patients with HIV RNA<50 copies/ml compared to the TDF/3TC/LPV/r treatment. Thus, mono-LPV/r should not be recommended as a second-line option.

High virologic response rate after second-line boosted protease inhibitor-based antiretroviral therapy regimens in children from a resource limited setting

Background

Limited data exist for the efficacy of second-line antiretroviral therapy among children in resource limited settings. We assessed the virologic response to protease inhibitor-based ART after failing first-line non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimens.

Methods

A retrospective chart review was conducted at 8 Thai sites of children who switched to PI –based regimens due to failure of NNRTI –based regimens. Primary endpoints were HIV RNA < 400 copies/ml and CD4 change over 48 weeks.

Results

Data from 241 children with median baseline values before starting PI-based regimens of 9.1 years for age, 10% for CD4%, and 4.8 log₁₀ copies/ml for HIV RNA were included; 104 (41%) received a single ritonavir-boosted PI (sbPI) with 2 NRTIs and 137 (59%) received double-boosted PI (dbPI) with/without NRTIs based on physician discretion. SbPI children had higher baseline CD4 (17% vs. 6%, p < 0.001), lower HIV RNA (4.5 vs. 4.9 log₁₀ copies/ml, p < 0.001), and less frequent high grade multi-NRTI resistance (12.4% vs 60.5%, p < 0.001) than the dbPI children. At week 48, 81% had HIV RNA < 400 copies/ml (sbPI 83.1% vs. dbPI 79.8%, p = 0.61) with a median CD4 rise of 9% (+7%vs. + 10%, p < 0.005). However, only 63% had HIV RNA < 50 copies/ml, with better viral suppression seen in sbPI (76.6% vs. 51.4%, p 0.002).

Conclusion

Second-line PI therapy was effective for children failing first line NNRTI in a resource-limited setting. DbPI were used in patients with extensive drug resistance due to limited treatment options. Better access to antiretroviral drugs is needed.

HIV-1 drug resistance mutations among antiretroviral-naive HIV-1-infected patients in Asia: results from the TREAT Asia Studies to Evaluate Resistance-Monitoring Study

Of 682 antiretroviral-naïve patients initiating antiretroviral therapy in a prospective, multicenter human immunodeficiency virus type 1 (HIV-1) drug resistance monitoring study involving 8 sites in Hong Kong, Malaysia, and Thailand, the prevalence of patients with ≥1 drug resistance mutation was 13.8%. Primary HIV drug resistance is emerging after rapid scaling-up of antiretroviral therapy use in Asia.

The evolution of HIV-1 reverse transcriptase in route to acquisition of Q151M multi-drug resistance is complex and involves mutations in multiple domains

Background

The Q151M multi-drug resistance (MDR) pathway in HIV-1 reverse transcriptase (RT) confers reduced susceptibility to all nucleoside reverse transcriptase inhibitors (NRTIs) excluding tenofovir (TDF). This pathway emerges after long term failure of therapy, and is increasingly observed in the resource poor world, where antiretroviral therapy is rarely accompanied by intensive virological monitoring. In this study we examined the genotypic, phenotypic and fitness correlates associated with the development of Q151M MDR in the absence of viral load monitoring.

Results

Single-genome sequencing (SGS) of full-length RT was carried out on sequential samples from an HIV-infected individual enrolled in ART rollout. The emergence of Q151M MDR occurred in the order A62V, V75I, and finally Q151M on the same genome at 4, 17 and 37 months after initiation of therapy, respectively. This was accompanied by a parallel cumulative acquisition of mutations at 20 other codon positions; seven of which were located in the connection subdomain. We established that fourteen of these mutations are also observed in Q151M-containing sequences submitted to the Stanford University HIV database. Phenotypic drug susceptibility testing demonstrated that the Q151M-containing RT had reduced susceptibility to all NRTIs except for TDF. RT domain-swapping of patient and wild-type RTs showed that patient-derived connection subdomains were not associated with reduced NRTI susceptibility. However, the virus expressing patient-derived Q151M RT at 37 months demonstrated ~44% replicative capacity of that at 4 months. This was further reduced to ~22% when the Q151M-containing DNA pol domain was expressed with wild-type C-terminal domain, but was then fully compensated by coexpression of the coevolved connection subdomain.

Conclusions

We demonstrate a complex interplay between drug susceptibility and replicative fitness in the acquisition Q151M MDR with serious implications for second-line regimen options. The acquisition of the Q151M pathway occurred sequentially over a long period of failing NRTI therapy, and was associated with mutations in multiple RT domains.

Monoboosted lopinavir/ritonavir as simplified second-line maintenance therapy in virologically suppressed children

BACKGROUND

Monoboosted protease inhibitor is being evaluated as a strategy to simplify therapy in virologically suppressed patients who are on complex regimens.

METHODS

Children with two consecutive HIV-RNA below 50 copies/ml at least 3 months apart while on double boosted protease inhibitor (dPI) were switched to monoboosted lopinavir/r (mLPV/r). The previous dPI regimen was resumed within 4 weeks in children who experienced virological failure defined as two HIV-RNA at least 500 or three HIV-RNA at least 50 copies/ml. Primary endpoint was the proportion of children still on mLPV/r and having HIV-RNA less than 50 copies/ml at week 48.

RESULTS

Forty children on LPV/r + saquinavir (90%) or LPV/r + indinavir (10%) were enrolled, 50% were female, median [interquartile range (IQR)] age was 11.7 (10.2-13.5) years, and body weight was 29.4 (24.1-40.2 kg). The median (IQR) CD4% was 27 (23.5-29.5%). At 48 weeks, none had died or had HIV disease progression. Thirty-one children were on mLPV/r and 29 (72.5%) had HIV-RNA less than 50 copies/ml. Nine resumed dPI due to mLPV/r failure with four achieving undetectable HIV-RNA. Overall, 31 children (82.5%) had HIV-RNA suppression. Predicting factor for failing mLPV/r was baseline HIV-RNA at least 50 copies/ml. No major protease mutations were found.

CONCLUSION

By simplifying second-line treatment from dPI to mLPV/r, the majority of children had sustained viral suppression at 48 weeks. Randomized study of simplified mono protease inhibitor therapy in children is warranted.

HIV Genetic Diversity and Drug Resistance

Most of the current knowledge on antiretroviral (ARV) drug development and resistance is based on the study of subtype B of HIV-1, which only accounts for 10% of the worldwide HIV infections. Cumulative evidence has emerged that different HIV types, groups and subtypes harbor distinct biological properties, including the response and susceptibility to ARV. Recent laboratory and clinical data highlighting such disparities are summarized in this review. Variations in drug susceptibility, in the emergence and selection of specific drug resistance mutations, in viral replicative capacity and in the dynamics of resistance acquisition under ARV selective pressure are discussed. Clinical responses to ARV therapy and associated confounding factors are also analyzed in the context of infections by distinct HIV genetic variants.

Effectiveness of boosted protease inhibitor-based regimens in HIV type 1-infected patients who experienced virological failure with NNRTI-based antiretroviral therapy in a resource-limited setting

A number of patients have experienced treatment failure while receiving non-nucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral therapy (ART), particularly in resource-limited countries. The need remains for clinical data on protease inhibitor (PI)-based regimens in these patients. A retrospective cohort study was conducted among HIV-1-infected patients who had failed NNRTI-based regimens, were naive to protease inhibitors (PIs), and subsequently initiated a salvage PI-based regimen between January 2004 and December 2006. The study period ended on 30 December 2007. One hundred and forty patients received a single-boosted PI +/- optimized background regimen (OBR) and 64 received double-boosted PIs. The median (IQR) duration of follow-up was 19 (13-29) months. The overall virological failure rate at 24 months was 15.2%. No statistically significant difference was detected between the two regimen groups (single-boosted PI +/- OBR 16.4% vs. double-boosted PIs 12.5%, log rank p = 0.818). At the end of the study, the median (IQR) change in CD4 cell counts for patients in the double-boosted PI group was higher than for patients in the single-boosted PI +/- OBR group [149 (53-322) vs. 105 (23-199), respectively, p = 0.012]. Patients receiving double-boosted PI regimens displayed a higher frequency of hypertriglyceridemia than those patients who received a single boosted PI +/- OBR (31% vs. 11%, respectively, p = 0.001). Boosted PI-based regimens showed acceptable virological outcomes among patients who had failed NNRTI-based ART. In the subgroup analysis, patients who received double-boosted PIs demonstrated a superior immunological response but not better virological outcomes compared to the single-boosted PI +/- OBR group.

Clinical management of HIV-1 resistance

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

Predictors of virologic failure and genotypic resistance mutation patterns in thai children receiving non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy

BACKGROUND

Nonnucleoside reverse transcription inhibitor (NNRTI)-based antiretroviral therapy (ART) has been widely used as a first-line regimen for the treatment of HIV. This study aimed to determine the rate and predictors of virologic failure and describe patterns of resistance mutation.

METHODS

The inclusion criteria were children who were <18 years and receiving NNRTI-based ART. Plasma HIV-1 RNA and CD4 were monitored every 6 months. Virologic failure was defined as plasma HIVRNA >1000 copies/mL.

RESULTS

Forty (20%) of 202 children had virologic failure, of whom 33 (16%) failed in the first year of therapy. By multivariate analysis, the children who received nevirapine were 3.7 times more likely to develop virologic failure than those receiving efavirenz (P = 0.006). The prevalence's of patients with >or=1 major mutations conferring drug resistance to nucleoside reverse transcription inhibitors (NRTIs) and NNRTIs were 89% and 97%, respectively. The common NNRTI mutations were Y181C/I (58%) and K103N (34%). The NRTI mutations were M184V/I (84%), K65R (11%), Q151M (5%), and >or=3 TAMs (3%).

CONCLUSIONS

The virologic failure rate in children was high and mostly occurred in the first year of treatment. The most common resistance mutations were those conferring resistance to NNRTIs and lamivudine. There were few instances of multiNRTI resistance. Early detection of virologic failure might allow more options for second-line regimens.

Differences in resistance mutations among HIV-1 non-subtype B infections: a systematic review of evidence (1996-2008)

Ninety percent of HIV-1-infected people worldwide harbour non-subtype B variants of HIV-1. Yet knowledge of resistance mutations in non-B HIV-1 and their clinical relevance is limited. Although a few reviews, editorials and perspectives have been published alluding to this lack of data among non-B subtypes, no systematic review has been performed to date.With this in mind, we conducted a systematic review (1996-2008) of all published studies performed on the basis of non-subtype B HIV-1 infections treated with antiretroviral drugs that reported genotype resistance tests. Using an established search string, 50 studies were deemed relevant for this review.These studies reported genotyping data from non-B HIV-1 infections that had been treated with either reverse transcriptase inhibitors or protease inhibitors. While most major resistance mutations in subtype B were also found in non-B subtypes, a few novel mutations in non-B subtypes were recognized. The main differences are reflected in the discoveries that: (i) the non-nucleoside reverse transcriptase inhibitor resistance mutation, V106M, has been seen in subtype C and CRF01_AE, but not in subtype B, (ii) the protease inhibitor mutations L89I/V have been reported in C, F and G subtypes, but not in B, (iii) a nelfinavir selected non-D30N containing pathway predominated in CRF01_AE and CRF02_AG, while the emergence of D30N is favoured in subtypes B and D, (iv) studies on thymidine analog-treated subtype C infections from South Africa, Botswana and Malawi have reported a higher frequency of the K65R resistance mutation than that typically seen with subtype B.Additionally, some substitutions that seem to impact non-B viruses differentially are: reverse transcriptase mutations G196E, A98G/S, and V75M; and protease mutations M89I/V and I93L.Polymorphisms that were common in non-B subtypes and that may contribute to resistance tended to persist or become more frequent after drug exposure. Some, but not all, are recognized as minor resistance mutations in B subtypes. These observed differences in resistance pathways may impact cross-resistance and the selection of second-line regimens with protease inhibitors. Attention to newer drug combinations, as well as baseline genotyping of non-B isolates, in well-designed longitudinal studies with long duration of follow up are needed.

The reverse transcriptase 67N 70R 215Y genotype is the predominant TAM pathway associated with virologic failure among HIV type 1C-infected adults treated with ZDV/ddI-containing HAART in southern Africa

HIV-1C has become the dominant HIV-1 subtype in the global AIDS epidemic. Historically, the evolution of drug-resistant mutations was characterized primarily among antiretroviral (ARV)-treated HIV-1B infections. Whereas the non-B viruses are susceptible to the currently used ARVs, some differences between HIV-1 subtypes in response to ARV regimens have been reported. We analyzed the profile of ARV-associated mutations in HIV-1C infection treated with ZDV/ddI-containing regimens in an open-label, randomized 3 x 2 x 2 factorial study comparing ZDV/3TC vs. ZDV/ddI vs. d4T/3TC and EFV vs. NVP regimens in drug-naive adults in Botswana. The overall rate of virologic failure in the ZDV/ddI-containing arms was 14%. We addressed the development of NRTI-associated mutations in 23 virologically failed patients in the ZDV/ddI-containing arms. The 67N 70R 215Y genotype with wild-type amino acids at codon positions 41 and 210 was a dominant pattern of NRTI-associated mutations at the time of virologic failure. The mutation T215Y was the first step in the evolution of the 67N 70R 215Y genotype and was followed by mutations K70R and D67N. Representing a mixture of TAM-1 (41L/210W/215Y) and TAM-2 (67N/70R/215F /219Q) pathways, the 67N 70R 215Y genotype with wild-type amino acids at codon positions 41, 210, and 219 is a unique TAM pathway that is rarely seen in HIV-1B infection. Although limited by relatively small numbers, our data suggest that the 67N 70R 215Y genotype may be the HIV-1C-specific response to the first-line ZDV/ddI-containing regimen at the time of virologic failure. The presence of the 67N 70R 215Y genotype with wild-type amino acids at codon positions 41, 210, and 219 in HIV-1C infection suggests that the evolution of ARV-associated mutations and TAM pathways might be unique in non-B HIV-1 subtypes treated with particular ARV regimens.

Absence of Resistance Mutations in Antiretroviral-Naive Patients Treated with Ritonavir-Boosted Saquinavir

Background

There are few data on the selection of resistance by ritonavir-boosted saquinavir (SQV/r), particularly in antiretroviral (ARV)-naive patients.

Objective

To assess the incidence of virological failure and evolution of resistance in ARV-naive individuals receiving SQV/r in the induction phase of the Staccato trial.

Methods

ARV-naive subjects ( n=272) received SQV/r 1,600/100 mg once daily with two nucleoside reverse transcriptase inhibitors (NRTIs) for at least 24 weeks. Patients were defined as having virological failure (VF) when there were two consecutive HIV-1 RNA measurements >500 copies/ml after week 12. Viral genotypes (reverse transcriptase [RT] and protease [PRO]) were determined at baseline in all patients and as close as possible to the time of initial failure in patients experiencing VF.

Results

VF was observed in 9/272 patients receiving SQV/r 1,600/100 mg once daily with two NRTIs (3.3%) and occurred 19–48 weeks after treatment initiation. Eight of these patients were evaluable at failure. No major PRO mutations were detected, but 2/8 displayed single new minor PRO substitutions (M36I, L10I) at VF that were known or suspected not to have been present at baseline; both these substitutions exist as natural polymorphisms. A third patient displayed a single new RT mutation (M184I).

Conclusions

SQV/r plus two NRTIs (1,600/100 mg once daily) is an effective initial treatment option for ARV-naive patients, resulting in a low rate of viral rebound (3.3%). Furthermore, no major protease mutations were detected following VF, suggesting that future treatment options are preserved.

Resistance issues with new nucleoside/nucleotide backbone options

The nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs/NtRTIs) remain an enduring feature of combination therapy. As NRTI/NtRTI options continue to expand, questions arise about how best to combine these agents to create effective dual NRTI/NtRTI backbones in antiretroviral regimens while avoiding treatment-emergent drug resistance. Clinicians must consider how NRTIs/NtRTIs such as tenofovir DF (TDF), abacavir (ABC), and emtricitabine (FTC), as well as new once-daily and coformulated NRTIs/NtRTIs, interact with older agents when combined in novel regimens and how sequencing the new NRTIs can preserve future treatment options. Resistance data from clinical trials have revealed important information on the patterns, prevalence, and effects of resistance seen among patients experiencing virologic failure. In recent years, the prevalence of some mutations such as M184V and Q151M has remained relatively constant, while the L74V mutation, the 69 insertions, and thymidine analogue mutations have decreased in prevalence. Other mutations such as K65R and Y115F, while still relatively uncommon, are increasing in prevalence. This increase may be due to the use of new treatment combinations that select for these mutations at a higher rate. Clinical trials suggest that new regimens containing TDF or ABC select for K65R and that this mutation is observed more frequently with TDF; in contrast, L74V is observed more frequently in ABC-containing regimens but is not commonly selected by TDF-containing regimens. Several lines of evidence are converging to suggest that the presence of zidovudine may decrease the risk of L74V and K65R in ABC- or TDF-containing regimens. This review summarizes the clinical implications of resistance profiles associated with new NRTI/NtRTI regimens in current use and in advanced clinical studies.

Characterization of mutations in HIV type 1 isolates from 144 Cambodian recently infected patients and pregnant women naive to antiretroviral drugs

A baseline study has been conducted to determine the polymorphism of reverse transcriptase, protease, and envelope genes of HIV-1 isolates from 146 antiretroviral drug-naive Cambodian patients including 22 seroconverters and 124 pregnant women having been diagnosed HIV positive for less than 1 year. Amplification of at least one gene was successful for 144 isolates. All three genes were obtained for 136 isolates. Subtyping showed that CRF01_AE was predominant (130 cases). According to the ANRS September 2004 list, polymorphism substitutions (>50% versus the subtype B consensus) of CRF01_AE at drug resistance positions were observed only in protease: I13V (81%), E35D (87%), M36I (100%), R41K (96%), and H69K (100%). Two strains bore one major resistance mutation to PIs: M46I and N88D. Five other strains carried drug resistance mutations to RTIs: K70R (one strain), V75M (three strains), and K101E (one strain). Of the isolates 4.9% had drug resistance mutations to antiretroviral drugs.

Efficacy of Highly Active Antiretroviral Therapy in HIV-Infected Children Participating in Thailand's National Access to Antiretroviral Program

BACKGROUND

Programs for access to antiretroviral treatment were only recently implemented in developing countries. This study aimed to describe the effect of highly active antiretroviral therapy (HAART) in treating human immunodeficiency virus (HIV)-infected children in Thailand's National Access to Antiretroviral Program for People Living with HIV/AIDS.

METHODS

From August 2002 to July 2003, a total of 107 children were enrolled in the study. They received HAART consisting of either nevirapine or efavirenz, together with lamivudine and stavudine. Generic drugs and/or adult formulations were used. CD4 lymphocyte count, plasma HIV RNA level, and weight-for-age and height-for-age z scores were measured before, 2 months after, and every 6 months after initiation of HAART. A genotypic resistance assay was performed for patients with poor virological response.

RESULTS

The mean age of the patients was 7.7 years (range, 2.1-13.8 years). At baseline, the median CD4 cell percentage was 3%, and the plasma HIV RNA level was 5.4 log10 copies/mL. Four patients died from HIV-related illness. After 72 weeks of HAART, the median CD4 cell percentage was 21%, and 76% of patients had HIV RNA levels of < 50 copies/mL. The mean weight-for-age and height-for-age z scores increased from -1.9 to -1.3 (P < .0001) and from -2.3 to -2.0 (P < .0001), respectively. The percentage of patients who took > or = 95% of prescribed medications during the interval between every follow-up visit was 86% For patients with suboptimal virological response, the most common resistance mutations among HIV isolates were associated with lamivudine and with nonnucleoside reverse-transcriptase inhibitors.

CONCLUSION

In this resource-limited setting, HAART is safe and effective for HIV-infected children despite initiation of treatment during the advanced stage of disease. The use of generic and nonpediatric drug formulations is feasible.

Development of HIV with Drug Resistance after CD4 Cell Count--Guided Structured Treatment Interruptions in Patients Treated with Highly Active Antiretroviral Therapy after Dual--Nucleoside Analogue Treatment

BACKGROUND

For patients with human immunodeficiency virus (HIV) infection, structured treatment interruption (STI) is an attractive alternative strategy to continuous treatment, particularly in resource-restrained settings, because it reduces both side effects and costs. One major concern, however, is the development of resistance to antiretroviral drugs that can occur during multiple cycles of starting and stopping therapy.

METHODS

HIV genotypic drug resistance was investigated in 20 HIV-infected Thai patients treated with highly active antiretroviral therapy (HAART) and CD4 cell count-guided STI after dual nucleoside reverse-transcriptase inhibitor (NRTI) treatment. Resistance was tested at the time of the switch from dual-NRTI treatment to HAART and when HAART was stopped during the last interruption.

RESULTS

After STI, one major drug-resistance mutation occurred (T215Y), and, in the 4 samples with preexisting major mutations (D67N [n=2], K70R [n=2], T215Y [n=2], and T215I [n=1]), the mutations disappeared. All mutations in the HIV protease gene were minor mutations already present, in most cases, before STI was started, and their frequency was not increased through STI, whereas the frequency of reverse-transcriptase gene mutations significantly decreased after the interruptions. After the 48-week study period, no patients had virological failure. Long-term follow-up (108 weeks) showed 1 case of virological failure in the STI arm and 1 in the continuous arm. No virological failure was seen in patients with major mutations.

CONCLUSIONS

Major HIV drug-resistance mutations were not induced through CD4 cell count-guided treatment interruptions in HIV-infected patients successfully treated with HAART after dual-NRTI therapy.

Resistance to dual nucleoside reverse-transcriptase inhibitors in children infected with HIV clade A/E

The prevalence of nucleoside reverse-transcriptase inhibitor (NRTI) mutations was determined among 95 human immunodeficiency virus-infected Thai children who were treated with dual nucleoside reverse-transcriptase inhibitors. Almost all children had resistance to at least 1 NRTI, and approximately half of the children had resistance to multiple NRTIs. Cross-resistance to stavudine and azidothymidine was universal.

HIV/AIDS in Asia

HIV (ie, HIV-1) epidemics in Asia show great diversity, both in severity and timing. But epidemics in Asia are far from over and several countries including China, Indonesia, and Vietnam have growing epidemics. Several factors affect the rate and magnitude of growth of HIV prevalence, but two of the most important are the size of the sex worker population and the frequency with which commercial sex occurs. In view of the present state of knowledge, even countries with low prevalence of infection might still have epidemics affecting a small percentage of the population. Once HIV infection has become established, growing needs for care and treatment are unavoidable and even the so-called prevention-successful countries of Thailand and Cambodia are seeing burgeoning care needs. The manifestations of HIV disease in the region are discussed with the aim of identifying key issues in medical management and care of HIV/AIDS. In particular, issues relevant to developing appropriate highly active antiretroviral treatment programmes in the region are discussed. Although access to antiretroviral therapy is increasing globally, making it work effectively while simultaneously expanding prevention programmes to stem the flow of new infections remains a real challenge in Asia. Genuine political interest and commitment are essential foundations for success, demanding advocacy at all levels to drive policy, mobilise sufficient resources, and take effective action.

Antiretroviral treatment in resource-poor settings: what can we learn from the existing programmes in Thailand?

Here we review a number of issues of relevance to the scale-up of antiretroviral therapy in Thailand. Thailand has an estimated number of people living with HIV/AIDS of approximately 600,000. Currently less than 10% of those are receiving highly active antiretroviral therapy. Government commitment to increase the numbers of individuals being treated has increased because of advocacy from various sectors of society, most importantly from organizations of individuals living with HIV/AIDS, decreasing antiretroviral drug prices, the availability of external funds, and the example of successful treatment initiatives by non-governmental organizations, academia and the private sector. It has also been prompted by the hosting of the 2004 International AIDS Conference in Bangkok.