Emerging mutations at virological failure of HAART combinations containing tenofovir and lamivudine or emtricitabine

Spirulina platensis Ameliorates Oxidative Stress Associated with Antiretroviral Drugs in HepG2 Cells

Lately, Spirulina platensis (SP), as an antioxidant, has exhibited high potency in the treatment of oxidative stress, diabetes, immune disorder, inflammatory stress, and bacterial and viral-related diseases. This study investigated the possible protective role of Spirulina platensis against ARV-induced oxidative stress in HepG2 cells. Human liver (HepG2) cells were treated with ARVs ((Lamivudine (3TC): 1.51 µg/mL, tenofovir disoproxil fumarate (TDF): 0.3 µg/mL and Emtricitabine (FTC): 1.8 µg/mL)) for 96 h and thereafter treated with 1.5 µg/mL Spirulina platensis for 24 h. After the treatments, the gene and protein expressions of the antioxidant response pathway were determined using a quantitative polymerase chain reaction (qPCR) and Western blots. The results show that Spirulina platensis decreased the gene expressions of Akt (p < 0.0001) and eNOS (↓p < 0.0001) while, on the contrary, it increased the transcript levels of NRF-2 (↑p = 0.0021), Keap1 (↑p = 0.0002), CAT (↑p < 0.0001), and NQO-1 (↑p = 0.1432) in the HepG2 cells. Furthermore, the results show that Spirulina platensis also decreased the protein expressions of NRF-2 (↓p = 0.1226) and pNRF-2 (↓p = 0.0203). Interestingly, HAART-SP induced an NRF-2 pathway response through upregulating NRF-2 (except for FTC-SP) (↑p < 0.0001), CAT (↑p < 0.0001), and NQO-1 (except for FTC-SP) (↑p < 0.0001) mRNA expression. In addition, NRF-2 (↑p = 0.0085) and pNRF-2 (↑p < 0.0001) protein expression was upregulated in the HepG2 cells post-exposure to HAART-SP. The results, therefore, allude to the fact that Spirulina platensis has the potential to mitigate HAART-adverse drug reactions (HAART toxicity) through the activation of antioxidant response in HepG2 cells. We hereby recommend further studies on Spirulina platensis and HAART synergy.

The Potential of Spirulina platensis to Ameliorate the Adverse Effects of Highly Active Antiretroviral Therapy (HAART)

The human immunodeficiency virus (HIV) is one of the most prevalent diseases globally. It is estimated that 37.7 million people are infected with HIV globally, and 8.2 million persons are infected with the virus in South Africa. The highly active antiretroviral therapy (HAART) involves combining various types of antiretroviral drugs that are dependent on the infected person’s viral load. HAART helps regulate the viral load and prevents its associated symptoms from progressing into acquired immune deficiency syndrome (AIDS). Despite its success in prolonging HIV-infected patients’ lifespans, the use of HAART promotes metabolic syndrome (MetS) through an inflammatory pathway, excess production of reactive oxygen species (ROS), and mitochondrial dysfunction. Interestingly, Spirulina platensis (SP), a blue-green microalgae commonly used as a traditional food by Mexican and African people, has been demonstrated to mitigate MetS by regulating oxidative and inflammatory pathways. SP is also a potent antioxidant that has been shown to exhibit immunological, anticancer, anti-inflammatory, anti-aging, antidiabetic, antibacterial, and antiviral properties. This review is aimed at highlighting the biochemical mechanism of SP with a focus on studies linking SP to the inhibition of HIV, inflammation, and oxidative stress. Further, we propose SP as a potential supplement for HIV-infected persons on lifelong HAART.

Substituting Generic Lamivudine for Emtricitabine in Virologically Suppressed HIV-Infected Patients

This study evaluated the effectiveness of formulary substitution from products or regimens containing name brand emtricitabine to alternative regimens containing generic lamivudine among virologically suppressed HIV-infected patients in a correctional managed health care system. Results of this retrospective cohort study showed that 94.9% of patients switched from emtricitabine to lamivudine ( n = 447) and 93.0% of emtricitabine control patients ( n = 449) had an undetectable viral load at last available test over a 2-year period. The two groups also showed similar values for CD4 counts, compliance, discontinuation, and M184V mutation; however, a slightly greater proportion of lamivudine patients experienced respiratory symptoms. Nonetheless, this study demonstrates that switching virologically suppressed HIV-infected patients from name brand emtricitabine-containing regimens to generic lamivudine-based regimens may reduce costs without compromising safety or effectiveness in correctional managed health care systems with directly observed therapy.

How Much Do We Know about Drug Resistance Due to PrEP Use? Analysis of Experts' Opinion and Its Influence on the Projected Public Health Impact

BACKGROUND

Randomized controlled trials reported that pre-exposure prophylaxis (PrEP) with tenofovir and emtricitabine rarely selects for drug resistance. However, drug resistance due to PrEP is not completely understood. In daily practice, PrEP will not be used under the well-controlled conditions available in the trials, suggesting that widespread use of PrEP can result in increased drug resistance.

METHODS

We surveyed expert virologists with questions about biological assumptions regarding drug resistance due to PrEP use. The influence of these assumptions on the prevalence of drug resistance and the fraction of HIV transmitted resistance was studied with a mathematical model. For comparability, 50% PrEP-coverage of and 90% per-act efficacy of PrEP in preventing HIV acquisition are assumed in all simulations.

RESULTS

Virologists disagreed on the following: the time until resistance emergence (range: 20-180 days) in infected PrEP users with breakthrough HIV infections; the efficacy of PrEP against drug-resistant HIV (25%-90%); and the likelihood of resistance acquisition upon transmission (10%-75%). These differences translate into projections of 0.6%- 1% and 3.5%-6% infected individuals with detectable resistance 10 years after introducing PrEP, assuming 100% and 50% adherence, respectively. The rate of resistance emergence following breakthrough HIV infection and the rate of resistance reversion after PrEP use is discontinued, were the factors identified as most influential on the expected resistance associated with PrEP. Importantly, 17-23% infected individuals could virologically fail treatment as a result of past PrEP use or transmitted resistance to PrEP with moderate adherence.

CONCLUSIONS

There is no broad consensus on quantification of key biological processes that underpin the emergence of PrEP-associated drug resistance. Despite this, the contribution of PrEP use to the prevalence of the detectable drug resistance is expected to be small. However, individuals who become infected despite the use of PrEP should be closely monitored due to higher risk of virological failure when initiating antiretroviral treatment in the future.

Efficacy of tenofovir and efavirenz in combination with lamivudine or emtricitabine in antiretroviral-naive patients in Europe

BACKGROUND

The combination of tenofovir and efavirenz with either lamivudine or emtricitabine (TELE) has proved to be highly effective in clinical trials for first-line treatment of HIV-1 infection. However, limited data are available on its efficacy in routine clinical practice.

METHODS

A multicentre cohort study was performed in therapy-naive patients initiating ART with TELE before July 2009. Efficacy was studied using ITT (missing or switch = failure) and on-treatment (OT) analyses. Genotypic susceptibility scores (GSSs) were determined using the Stanford HIVdb algorithm.

RESULTS

Efficacy analysis of 1608 patients showed virological suppression to <50 copies/mL at 48 weeks in 91.5% (OT) and 70.6% (ITT). Almost a quarter of all patients (22.9%) had discontinued TELE at week 48, mainly due to CNS toxicity. Virological failure within 48 weeks was rarely observed (3.3%, n = 53). In multilevel, multivariate analysis, infection with subtype B (P = 0.011), baseline CD4 count <200 cells/mm³ (P < 0.001), GSS <3 (P = 0.002) and use of lamivudine (P < 0.001) were associated with a higher risk of virological failure. After exclusion of patients using co-formulated compounds, virological failure was still more often observed with lamivudine. Following virological failure, three-quarters of patients switched to a PI-based regimen with GSS <3. After 1 year of second-line therapy, viral load was suppressed to <50 copies/mL in 73.5% (OT).

CONCLUSIONS

In clinical practice, treatment failure on TELE regimens is relatively frequent due to toxicity. Virological failure is rare and more often observed with lamivudine than with emtricitabine. Following virological failure on TELE, PI-based second-line therapy was often successful despite GSS <3.

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

OBJECTIVE

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

DESIGN

An expert review.

METHODS

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

RESULTS

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

CONCLUSION

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

Increased virological failure in naive HIV-1-infected patients taking lamivudine compared with emtricitabine in combination with tenofovir and efavirenz or nevirapine in the Dutch nationwide ATHENA cohort

BACKGROUND

Guidelines for treatment of human immunodeficiency virus type 1 (HIV-1) infection consider lamivudine and emtricitabine to be interchangeable components in first-line combination antiretroviral therapy (cART). The evidence for their clinical equivalence in cART is inconsistent. The primary aim of this study was to evaluate the virological responses to lamivudine and emtricitabine in recommended cART.

METHODS

This was an observational study using data from the AIDS Therapy Evaluation in the Netherlands (ATHENA) nationwide HIV cohort. The virological responses to lamivudine and emtricitabine were compared by multivariable adjusted logistic regression and Cox proportional hazard models. Sensitivity analyses included propensity score-adjusted models.

RESULTS

Therapy-naive HIV-1-infected patients without baseline resistance (N = 4740) initiated lamivudine or emtricitabine with efavirenz/tenofovir or nevirapine/tenofovir. The use of lamivudine was associated with more virological failure at week 48 compared to emtricitabine with efavirenz/tenofovir (10.8% vs 3.6%; adjusted odds ratio [AOR], 1.78; 95% confidence interval [CI], 1.11-2.84) and nevirapine/tenofovir (27% vs 11%; AOR, 2.09; 95% CI, 1.25-3.52) in on-treatment analysis. Propensity score-adjusted models and intent-to-treat sensitivity analyses gave comparable results. The adjusted hazard ratio of virological failure at week 240 using lamivudine instead of emtricitabine was 2.35 (95% CI, 1.61-3.42) with efavirenz and 2.01 (95% CI, 1.36-2.98) with nevirapine. The inclusion of lamivudine or emtricitabine in cART did not influence the time to virological suppression within 48 weeks or the probability of virological rebound after successful virological suppression.

CONCLUSIONS

The use of emtricitabine instead of lamivudine as part of cART was associated with better virological responses. These findings are relevant for settings with extensive use of lamivudine and for settings where generic lamivudine will be available.

Targeting host nucleotide biosynthesis with resveratrol inhibits emtricitabine-resistant HIV-1

OBJECTIVE

The M184V mutation in the HIV-1 reverse transcriptase gene is frequent (>50%) in patients, both in resource-rich and resource-limited countries, conferring high-level resistance (>100-fold) to the cytosine analog reverse transcriptase inhibitors lamivudine and emtricitabine. The reverse transcriptase enzyme of M184V HIV-1 mutants has reduced processivity, resulting in reduced viral replication, particularly at low deoxynucleotide (dNTP) levels. We hypothesized that lowering intracellular dNTPs with resveratrol, a dietary supplement, could interfere with replication of M184V HIV-1 mutants.

DESIGN AND METHODS

Evaluation of the activity of resveratrol on infection of primary peripheral blood lymphocytes by wild-type and M184V mutant HIV-1. We assayed both molecular clones and primary isolates of HIV-1, containing M184V alone and in combination with other reverse transcriptase mutations. Viral infection was quantified by p24 ELISA and by quantitative real-time PCR analysis. Cell viability was measured by colorimetric 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assays.

RESULTS

In virus-infectivity assays, resveratrol did not inhibit replication of wild-type NL4-3 (resveratrol EC50 > 10 μmol/l), but it inhibited NL4-3 184V mutant (resveratrol EC50 = 5.8 μmol/l). These results were confirmed by real-time PCR analysis of early and late products of reverse transcription. Resveratrol inhibited molecular clones and primary isolates carrying M184V, alone or in combination with other reverse transcriptase mutations (resveratrol EC50 values ranging from 2.5 to 7.7 μmol/l).

CONCLUSIONS

Resveratrol inhibits HIV-1 strains carrying the M184V mutation in reverse transcriptase. We propose resveratrol as a potential adjuvant in HIV-1 therapy, particularly in resource-limited settings, to help control emtricitabine-resistant M184V HIV-1 mutants.

Antiretroviral treatment French guidelines 2013: economics influencing science

Guidelines for the preferred choice of initial combination antiretroviral therapy in those living with HIV are provided by several national and international committees. Following the recent presentation of the 2013 French guidelines on antiretroviral therapy, there has been a debate regarding whether and/or how economics should influence guideline decisions and to what extent this should counterbalance valid scientific evidence. We discuss here the reasons for the unique nature of some of the proposals made by the French guidelines panel. Indeed, some recommendations are debatable. In the new French guidelines, economic considerations significantly influence and, in some instances, take precedence over the scientific evidence, leading to guidelines that are significantly different from those of other national and international committees.

The emergence of drug resistant HIV variants at virological failure of HAART combinations containing efavirenz, tenofovir and lamivudine or emtricitabine within the UK Collaborative HIV Cohort

BACKGROUND

Lamivudine (3TC) and emtricitabine (FTC) are guideline choices for combination highly active antiretroviral therapy (HAART). 3TC has a shorter intracellular half life than FTC and may be more likely to lead to the development of drug resistant HIV variants.

METHODS

In this study we analysed linked data from the observational UK Collaborative HIV Cohort (CHIC) Study and UK HIV Drug Resistance Database (HDRD) to investigate the rate of development of K65R or M184V resistance mutations in patients failing on combinations containing tenofovir (TDF) and efavirenz (EFV) with either 3TC or FTC. Virological failure was defined as 1 viral load >400 copies/ml. Rates were stratified by demographic variables, baseline viral load, current CD4 count, current viral load and year of starting regimen. Significant associations were identified using Poisson regression models and multivariable analyses were performed adjusting for the variables above. Logistic regression was used to determine whether there were any significant associations between type of regimen and detection of resistance mutation.

RESULTS

5455 patients received either (or both) 3TC, TDF and EFV or FTC, TDF and EFV contributing 6465 treatment episodes over 9962 person-years follow up. 47 of these episodes were preceded by resistance tests showing development of K65R or M184V mutation and were hence excluded. The majority of treatment episodes consisted of FTC- (n = 5190) rather than 3TC- (n = 1228) based regimens. 21 cases of K65R were detected over the course of follow up, giving an overall event rate of 0.21 (95% CI: 0.12-0.31)/100 person years follow up (PYFU). The overall event rate for detection of M184V was 0.38 (95% CI: 0.26-0.5)/100 PYFU. 201 patients receiving either regimen for the first time experienced virological failure. Of those receiving 3TC (n = 53), 7 (13.2%), 12 (22.6%) and 15 (28.3%) developed K65R, M184V and either K65R or M184V respectively. Of those receiving FTC (n = 148), 13 (8.8%), 20 (13.5%) and 26 (17.6%) developed K65R, M184V and either K65R or M184V respectively. Although patients on 3TC were more likely to develop resistance, this was not statistically significant in univariable (OR 1.85 (95% CI: 0.89-3.85, p = 0.09)) or multivariable analyses (OR 1.89 (95% CI: 0.89-4.01, p = 0.1)).

CONCLUSIONS

We have not found evidence of an increased risk of development of M184V and K65R in patients exposed to 3TC.

Emtricitabine/tenofovir in the treatment of HIV infection: current PK/PD evaluation

INTRODUCTION

Emtricitabine/tenofovir disoproxil fumarate fixed-dose combination (FTC/TDF FDC) is the co-formulation of a nucleoside and a nucleotide, respectively. After oral administration, both drugs exhibit plasma and intracellular half-lives suitable for once-daily dosing. Within the host cells, active metabolites FTC-TP and TFV-DP act as chain terminators to the newly synthesized proviral DNA, showing synergy at enzymatic level (viral reverse transcriptase). When given in HAART combinations, FTC/TDF FDC has a remarkable effectiveness in controlling HIV replication and securing a significant CD4(+) cell recovery. If patients treated with FTC/TDF FDC fail, a lower incidence of TDF-associated K65R resistance mutation seems to develop. Furthermore, cytidine analog-associated M184V is less likely to appear with FTC than with lamivudine when both are given with TDF. FTC and TFV are not metabolized by CYP450 enzymes and are eliminated by the renal route. TFV may accumulate in tubular cells and cause a decrease in GFR and a loss of phosphates. As a onsequence, patients treated with FTC/TDF FCD may experience varied degrees of renal impairment and osteopenia/osteoporosis.

AREAS COVERED

This paper has focused on the PK/PD features of FTC and TDF, when given as single agent or when administered as FDC. The interpretation of efficacy/toxicity was guided by PK/PD features. The review of the available literature included also conference presentations and recent guidelines (as of May 2012).

EXPERT OPINION

FTC/TDF FDC is a potent and reliable component of most HAART combinations due to its maintained activity across time, as demonstrated in many trials and studies. Toxicity issues (kidney, bone) are still to be entirely elucidated and the drug-induced component well separated from patient- and HIV-related ones. However, the clinical gain associated with the use of FTC/TDF FDC is fully acknowledged by its leading position in most current treatment guidelines.

Cost analysis of HIV treatment and drug-related adverse events when fixed-dose combinations of antiretrovirals (FDCs) were stopped, versus continuation with FDCs

BACKGROUND

The lower sales price of generic lamivudine has caused healthcare administrators to consider abolishing fixed-dose antiretroviral combinations (FDCs) that contain lamivudine and emtricitabine. The alternative is to administer the individual components of the FDCs separately, thus incorporating the new generic lamivudine medication.

METHODS

The Balearic Islands Health Service ordered the discontinuation of the treatment with FDCs in July 2010, but FDCs were reintroduced in August 2010. At that point, an independent, retrospective cost analysis was performed by Son Llàtzer Hospital. A total of 75 patients who were treated from July to August 2010 underwent replacement of their FDC treatment with the individual components. Additionally, 150 patients who continued using FDCs were randomly selected. For both patient groups, the antiretroviral therapy that was administered and the costs associated with management of adverse events were recorded. The study period used for the cost calculations was the average number of days that patients used separate components of FDCs (120 days). An alternative analysis was performed to consider the costs of the extra follow-up visit (consultation and clinical tests) that was required for patients who changed their antiretroviral therapy.

RESULTS

Considering antiretroviral therapies and adverse events, the administration of the separate components increased the total daily cost by 0.72 € per patient compared to treatment with FDCs. When the cost of an extra follow-up visit was considered, the daily cost increased by 3.61 € per patient.

CONCLUSIONS

Our study suggests that the discontinuation of FDC treatment and the replacement with the administration of separate antiretroviral agents could lead to an increase in healthcare costs due to the higher rate of adverse events that was observed with the discontinuation of FDCs.

Trends in HIV-1 reverse transcriptase resistance-associated mutations and antiretroviral prescription data from 2003-2010

BACKGROUND

The selection of antiretroviral (ARV) drugs for treatment of HIV-1 infection is based on several factors including potency, toxicity, resistance and ease of administration. Emtricitabine (FTC) or lamivudine (3TC), components of recommended initial ARV regimens, are structurally related and share the same resistance mutation (M184V/I). However they differ with respect to potency and incidence of M184V/I.

METHODS

Resistance-associated mutation (RAM) prevalence data were obtained from genotype test results performed in a large reference laboratory from 2003-2010; subsets of data were defined by mutation pattern to resemble those following failure of non-nucleoside reverse transcriptase inhibitor (NNRTI)-based combination therapy. Mutational trend data were compared to contemporaneous ARV prescription information.

RESULTS

In the unfiltered data set (n=107,231), the prevalence in 2010 decreased compared to 2003 for all nucleoside/nucleotide reverse transcriptase inhibitor (NRTI) RAMs, such as M184V/I (44.0% to 17.9%), T215Y (22.7% to 4.1%), and K65R (4.3% to 2.1%). Among samples resembling those typical of first-line NNRTI-based failures, prevalence of K103N increased slightly, but prevalence of M184V/I decreased (49.8% to 36.8%), as did other NRTI RAMs. These decreases were coincident with a shift in ARV prescriptions away from zidovudine and 3TC towards tenofovir and FTC, and an increase in use of fixed-dose combinations.

CONCLUSIONS

RAM prevalence decreased substantially since 2003 among samples submitted for resistance testing in the US. The causes of this decrease are multifactorial, but our results suggest a possible role of increased use of potent ARVs that are available as fixed-dose combinations or as single-tablet regimens.

Antiretroviral therapy in Indian setting: when & what to start with, when & what to switch to?

With the rapid scale up of antiretroviral therapy, there is a dramatic decline in HIV related morbidity and mortality in both developed and developing countries. Several new safe antiretroviral, and newer class of drugs and monitoring assays are developed recently. As a result the treatment guideline for the management of HIV disease continue to change. This review focuses on evolving science on Indian policy - antiretroviral therapy initiation, which drugs to start with, when to change the initial regimen and what to change.

Cytosine deoxyribonucleoside anti-HIV analogues: a small chemical substitution allows relevant activities

The search for new nucleoside analogue compounds targeting the virally encoded reverse transcriptase was developed by modifying the nucleoside structure to create inhibitor compounds. In this review, the structure-activity relationship of antiviral compounds synthesised from the naturally existing cytosine deoxyribonucleoside (dC) was evaluated. The line of research starting from dC led to the synthesis of 2',3'-dideoxycytidine (ddC; zalcitabine), 2',3'-dideoxy-3'-thiacytidine (3TC; lamivudine) and 2',3'-dideoxy-5-fluoro-3'-thiacytidine (FTC; emtricitabine) and looks very interesting because each product comes from a single small change in the chemical structure of the former compound, resulting in a progressive improvement in terms of activity, pharmacokinetics, tolerability and emergence of resistance.

Comparative outcomes of tenofovir-based and zidovudine-based antiretroviral therapy regimens in Lusaka, Zambia

BACKGROUND

Although tenofovir (TDF) is a common component of antiretroviral therapy (ART), recent evidence suggests inferior outcomes when it is combined with nevirapine (NVP).

METHODS

We compared outcomes among patients initiating TDF + emtricitabine or lamivudine (XTC) + NVP, TDF + XTC + efavirenz (EFV), zidovudine (ZDV) + lamuvidine (3TC) + NVP, and ZDV + 3TC + EFV. We categorized drug exposure by initial ART dispensation by a time-varying analysis that accounted for drug substitutions and by predominant exposure (>75% of drug dispensations) during an initial window period. Risks for death and program failure were estimated using Cox proportional hazard models. All regimens were compared with ZDV + 3TC + NVP.

RESULTS

Between July 2007 and November 2010, 18,866 treatment-naive adults initiated ART: 18.2% on ZDV + 3TC + NVP, 1.8% on ZDV + 3TC + EFV, 36.2% on TDF + XTC + NVP, and 43.8% on TDF + XTC + EFV. When exposure was categorized by initial prescription, patients on TDF + XTC + NVP [adjusted hazard ratio (AHR): 1.45; 95% confidence interval (CI): 1.03 to 2.06] had a higher post-90-day mortality. TDF + XTC + NVP was also associated with an elevated risk for mortality when exposure was categorized as time-varying (AHR: 1.51; 95% CI: 1.18 to 1.95) or by predominant exposure over the first 90 days (AHR: 1.91, 95% CI: 1.09 to 3.34). However, these findings were not consistently observed across sensitivity analyses or when program failure was used as a secondary outcome.

CONCLUSION

TDF + XTC + NVP was associated with higher mortality when compared with ZDV + 3TC + NVP but not consistently across sensitivity analyses. These findings may be explained in part by inherent limitations to our retrospective approach, including residual confounding. Further research is urgently needed to compare the effectiveness of ART regimens in use in resource-constrained settings.

Control of M184V HIV-1 mutants by CD8 T-cell responses

Antiretroviral treatment directed against HIV is highly effective, yet limited by drug resistance mutations. We hypothesized that CD8 T cells targeting drug-resistant HIV mutants are able to inhibit viral replication in the setting of a failing therapeutic regimen. We evaluated CD8 T-cell responses and mapped epitopes in HIV-infected patients by interferon-gamma Elispot and intracellular cytokine staining. Autologous virus was sequenced by RT-PCR. Viral replication inhibition assays were performed using M184V mutant virus and CD8 T cell lines. CD8 T-cell responses toward the regions of viral drug resistance mutations in Pol are frequent. Focusing on the M184V mutation, A*02:01-YQYVDDLYV and A*02:01-VIYQYVDDLYV were identified as optimal epitopes for the majority of study subjects. Viral replication of M184V HIV mutants was inhibited by CD8 T cell lines in vitro. In case of a failing lamivudine/emtricitabine containing regimen, individuals with a CD8 T-cell response toward M184V had a significant lower viral load than those without a CD8 response (p = 0.005). Two study subjects even achieved an undetectable viral load. Our data suggest that control of M184V mutant virus by CD8 T-cell responses is possible in vitro and in vivo. This control has important implications for therapeutic vaccination strategies.

Abacavir/lamivudine versus tenofovir DF/emtricitabine as part of combination regimens for initial treatment of HIV: final results

BACKGROUND

AIDS Clinical Trials Group A5202 compared blinded abacavir/lamivudine (ABC/3TC) to tenofovir DF/emtricitabine (TDF/FTC) with efavirenz (EFV) or atazanavir/ritonavir (ATV/r) in human immunodeficiency virus (HIV)-infected treatment-naive patients, stratified by screening HIV RNA (< or ≥ 10(5) copies/mL). Due to higher virologic failure with ABC/3TC in the high HIV RNA stratum, blinded treatment was stopped in this group, but study follow-up continued for all patients.

METHODS

Primary endpoints were times to virologic failure, regimen modification, and safety event.

RESULTS

In the low HIV RNA stratum, time to virologic failure was similar for ABC/3TC vs TDF/FTC with ATV/r (hazard ratio [HR] 1.25, 95% confidence interval [CI] 0.76, 2.05) or EFV (HR 1.23, 95% CI 0.77, 1.96), with significantly shorter times to regimen modification for ABC/3TC with EFV or ATV/r and to safety events with EFV. Prior to stopping blinded treatment in the high stratum, higher virologic failure rates were seen with ABC/3TC with EFV (HR 2.46, 95% CI 1.20, 5.05) or ATV/r (HR 2.22, 95% CI 1.19, 4.14).

CONCLUSIONS

In the low HIV RNA stratum, times to virologic failure for ABC/3TC or TDF/FTC were not different with EFV or ATV/r. In the high stratum, virologic failure rate was significantly higher for ABC/3TC than for TDF/FTC when given with either EFV or ATV/r.

Clinical implications of fixed-dose coformulations of antiretrovirals on the outcome of HIV-1 therapy

The substitution by generic equivalents of some of the drugs included in fixed-dose antiretroviral coformulations (FDACs) poses the potential risk of disrupting these combinations and administering the components separately in order to incorporate the new generic drug, which offers a more competitive sales price. This may represent a step backwards in the advances achieved in simplicity and adherence to therapy, posing an increased risk of selective noncompliance of some of the separately administered drug substances. Available antiretroviral drugs must be administered for life in the affected individuals - both children and adults. The FDACs represent a significant advance in the simplification of antiretroviral therapy, facilitating adherence to complex and chronic treatments, and contributing to a quantifiable improvement in patient quality of life. These drug coformulations reduce the risk of treatment error, are associated with a lower risk of hospitalization, and can lessen the possibility of covert monotherapy in situations of selective noncompliance. Thus, FDACs can reduce the risk of selection of HIV-1 resistances, which not only adversely affect the treatment options of the individual patient but also constitute a public health problem, and further increase the cost and complexity of therapy. With the exception of those cases requiring dose adjustments, the preferential use of FDACs should be recommended for the treatment of HIV-1 infection in those situations when the agents included in the coformulation are drugs of choice.

The risk of HIV drug resistance following implementation of pre-exposure prophylaxis

PURPOSE OF REVIEW

Results of trials determining if pre-exposure prophylaxis (PrEP) with antiretroviral drugs prevents transmission of HIV are expected soon. Tenofovir and emtricitabine--currently evaluated as PrEP--are popular in treatment of HIV. Drug resistance could, therefore, be critical in the use of PrEP. We review the literature regarding risks associated with drug resistance owing to PrEP.

RECENT FINDINGS

Few studies addressed the issue of drug resistance to tenofovir and/or emtricitabine. Studies in HIV-1-infected individuals followed small numbers of patients for a short time. Studies in macaques were well designed, but used SHIV, which has an attenuated course of infection. The available information suggests that the probability of emergence of drug resistance is small. Infections that occurred despite use of PrEP had reduced peak viremia, which could reduce HIV transmissibility. Mathematical modeling suggests that, although transmitted drug resistance may under some circumstances increase, the benefits of PrEP outweigh the risks associated with resistance.

SUMMARY

Tenofovir and emtricitabine are recommended in first-line treatment. The potentially limited impact of drug resistance should, therefore, be confirmed in daily practice. Surveillance of drug resistance is recommended in areas where PrEP is used. Patients that became infected despite use of PrEP should be closely monitored for virological failure.