Rates of emergence of HIV drug resistance in resource-limited settings: a systematic review

Different trends of transmitted HIV-1 drug resistance in Madrid, Spain, among risk groups in the last decade

The presence of transmitted HIV drug resistance (TDR) threatens the efficacy of antiretroviral treatment. We aimed to assess the changes in TDR prevalence over the last decade in Madrid, Spain, to verify the role of the patients' risk groups in these changes. We analysed the trends of TDR between 2000 and 2011 in a cohort of 1,022 naïve HIV-infected patients in Madrid, Spain, whose pol sequences were available. They included, among others, 369 heterosexuals, 340 men who have sex with men (MSM), and 90 injection drug users (IDUs). TDR was reported following the WHO mutation list. The TDR rate in the whole cohort was 8.3 %, being the highest in MSM (9.1 %) and the lowest in IDUs (4.4 %). Over time, this rate decreased significantly (to 5.4 % in 2009-2011) since the period 2004-2006, when it peaked (10.7 %). Heterosexuals and IDUs showed similar trends, but in the 2009-2011 period, the TDR rate among MSM rebounded to 9.0 % (being absent among IDUs). TDR stabilized in the last years (2007-2011) for nucleoside reverse transcriptase inhibitors. The risk group also determined differences in the mutational profile, sex distribution, proportion of immigrants, and viral variants. In conclusion, the risk group caused different HIV sub-epidemics, determined by the patients' profiles. Despite the general decreasing trend in TDR, we observed a non-significant increase in TDR rate among MSM, a tendency that needs confirmation. Periodic TDR surveillance is important to prevent the widespread distribution of resistance, especially in MSM, given the growing HIV/AIDS epidemic in this high-risk population.

Increasing rate of TAMs and etravirine resistance in HIV-1-infected adults between 12 and 24 months of treatment: the VOLTART cohort study in Côte d'Ivoire, West Africa

BACKGROUND

In sub-Saharan Africa, most HIV-infected patients receive antiretroviral therapy (ART) without virological monitoring. Longitudinal data on secondary resistance are rare.

METHODS

We conducted a prospective cohort study of HIV-1-infected adults initiating ART in 3 clinics using computerized monitoring systems. Patients had plasma HIV-1 RNA viral load (VL) tests at months 12 (M12) and 24 (M24) after ART initiation and HIV-1 resistance genotype tests if VL was detectable (≥300 copies/mL).

RESULTS

Overall, 1573 patients initiated ART with stavudine/zidovudine plus lamivudine plus nevirapine/efavirenz. At M12 and M24, 944 and 844 patients, respectively, remained in active follow-up. Among them, 25% (M12) and 27% (M24) had detectable VLs and 12% (M12) and 19% (M24) had virus resistant to at least 1 antiretroviral drug, accounting for 54% (M12) and 75% (M24) of patients with detectable VLs. Among the resistant strains, 95% (M12) and 97% (M24) were resistant to lamivudine/emtricitabine, efavirenz, and/or nevirapine, the frequency of thymidine analog mutations increased from 8.1% (M12) to 14.7% (M24) and etravirine resistance increased from 13.5% (M12) to 24.5% (M24).

CONCLUSIONS

Of the patients with detectable VLs at M24, 25% still did not harbor resistant virus. Preventing mutations from emerging with adherence reinforcement in patients with detectable VLs remains important beyond M24. Switching therapy early in patients with resistance to 3 TC/FTC and/or to nonnucleoside reverse transcriptase inhibitors to prevent extended resistance to nucleoside reverse transcriptase inhibitors and etravirine resistance from occurring is also a major challenge.

Simultaneous detection of major drug resistance mutations in the protease and reverse transcriptase genes for HIV-1 subtype C by use of a multiplex allele-specific assay

High-throughput, sensitive, and cost-effective HIV drug resistance (HIVDR) detection assays are needed for large-scale monitoring of the emergence and transmission of HIVDR in resource-limited settings. Using suspension array technology, we have developed a multiplex allele-specific (MAS) assay that can simultaneously detect major HIVDR mutations at 20 loci. Forty-five allele-specific primers tagged with unique 24-base oligonucleotides at the 5' end were designed to detect wild-type and mutant alleles at the 20 loci of HIV-1 subtype C. The MAS assay was first established and optimized with three plasmid templates (C-wt, C-mut1, and C-mut2) and then evaluated using 148 plasma specimens from HIV-1 subtype C-infected individuals. All the wild-type and mutant alleles were unequivocally distinguished with plasmid templates, and the limits of detection were 1.56% for K219Q and K219E, 3.13% for L76V, 6.25% for K65R, K70R, L74V, L100I, K103N, K103R, Q151M, Y181C, and I47V, and 12.5% for M41L, K101P, K101E, V106A, V106M, Y115F, M184V, Y188L, G190A, V32I, I47A, I84V, and L90M. Analyses of 148 plasma specimens revealed that the MAS assay gave 100% concordance with conventional sequencing at eight loci and >95% (range, 95.21% to 99.32%) concordance at the remaining 12 loci. The differences observed were caused mainly by 24 additional low-abundance alleles detected by the MAS assay. Ultradeep sequencing analysis confirmed 15 of the 16 low-abundance alleles. This multiplex, sensitive, and straightforward result-reporting assay represents a new efficient genotyping tool for HIVDR surveillance and monitoring.

Low primary and secondary HIV drug-resistance after 12 months of antiretroviral therapy in human immune-deficiency virus type 1 (HIV-1)-infected individuals from Kigali, Rwanda

Treatment outcomes of HIV patients receiving antiretroviral therapy (ART) in Rwanda are scarcely documented. HIV viral load (VL) and HIV drug-resistance (HIVDR) outcomes at month 12 were determined in a prospective cohort study of antiretroviral–naïve HIV patients initiating first-line therapy in Kigali. Treatment response was monitored clinically and by regular CD4 counts and targeted HIV viral load (VL) to confirm drug failure. VL measurements and HIVDR genotyping were performed retrospectively on baseline and month 12 samples. One hundred and fifty-eight participants who completed their month 12 follow-up visit had VL data available at month 12. Most of them (88%) were virologically suppressed (VL≤1000 copies/mL) but 18 had virological failure (11%), which is in the range of WHO-suggested targets for HIVDR prevention. If only CD4 criteria had been used to classify treatment response, 26% of the participants would have been misclassified as treatment failure. Pre-therapy HIVDR was documented in 4 of 109 participants (3.6%) with an HIVDR genotyping results at baseline. Eight of 12 participants (66.7%) with virological failure and HIVDR genotyping results at month 12 were found to harbor mutation(s), mostly NNRTI resistance mutations, whereas 4 patients had no HIVDR mutations. Almost half (44%) of the participants initiated ART at CD4 count ≤200cell/µl and severe CD4 depletion at baseline (<50 cells/µl) was associated with virological treatment failure (p = 0.008).

Although the findings may not be generalizable to all HIV patients in Rwanda, our data suggest that first-line ART regimen changes are currently not warranted. However, the accumulation of acquired HIVDR mutations in some participants underscores the need to reinforce HIVDR prevention strategies, such as increasing the availability and appropriate use of VL testing to monitor ART response, ensuring high quality adherence counseling, and promoting earlier identification of HIV patients and enrollment into HIV care and treatment programs.

Nucleoside reverse transcriptase inhibitor resistance mutations associated with first-line stavudine-containing antiretroviral therapy: programmatic implications for countries phasing out stavudine

BACKGROUND

The World Health Organization Antiretroviral Treatment Guidelines recommend phasing-out stavudine because of its risk of long-term toxicity. There are two mutational pathways of stavudine resistance with different implications for zidovudine and tenofovir cross-resistance, the primary candidates for replacing stavudine. However, because resistance testing is rarely available in resource-limited settings, it is critical to identify the cross-resistance patterns associated with first-line stavudine failure.

METHODS

We analyzed HIV-1 resistance mutations following first-line stavudine failure from 35 publications comprising 1,825 individuals. We also assessed the influence of concomitant nevirapine vs. efavirenz, therapy duration, and HIV-1 subtype on the proportions of mutations associated with zidovudine vs. tenofovir cross-resistance.

RESULTS

Mutations with preferential zidovudine activity, K65R or K70E, occurred in 5.3% of individuals. Mutations with preferential tenofovir activity, ≥ two thymidine analog mutations (TAMs) or Q151M, occurred in 22% of individuals. Nevirapine increased the risk of TAMs, K65R, and Q151M. Longer therapy increased the risk of TAMs and Q151M but not K65R. Subtype C and CRF01_AE increased the risk of K65R, but only CRF01_AE increased the risk of K65R without Q151M.

CONCLUSIONS

Regardless of concomitant nevirapine vs. efavirenz, therapy duration, or subtype, tenofovir was more likely than zidovudine to retain antiviral activity following first-line d4T therapy.

When to start antiretroviral therapy: the need for an evidence base during early HIV infection

BACKGROUND

Strategies for use of antiretroviral therapy (ART) have traditionally focused on providing treatment to persons who stand to benefit immediately from initiating the therapy. There is global consensus that any HIV+ person with CD4 counts less than 350 cells/μl should initiate ART. However, it remains controversial whether ART is indicated in asymptomatic HIV-infected persons with CD4 counts above 350 cells/μl, or whether it is more advisable to defer initiation until the CD4 count has dropped to 350 cells/μl. The question of when the best time is to initiate ART during early HIV infection has always been vigorously debated. The lack of an evidence base from randomized trials, in conjunction with varying degrees of therapeutic aggressiveness and optimism tempered by the risks of drug resistance and side effects, has resulted in divided expert opinion and inconsistencies among treatment guidelines.

DISCUSSION

On the basis of recent data showing that early ART initiation reduces heterosexual HIV transmission, some countries are considering adopting a strategy of universal treatment of all HIV+ persons irrespective of their CD4 count and whether ART is of benefit to the individual or not, in order to reduce onward HIV transmission. Since ART has been found to be associated with both short-term and long-term toxicity, defining the benefit:risk ratio is the critical missing link in the discussion on earlier use of ART. For early ART initiation to be justified, this ratio must favor benefit over risk. An unfavorable ratio would argue against using early ART.

SUMMARY

There is currently no evidence from randomized controlled trials to suggest that a strategy of initiating ART when the CD4 count is above 350 cells/μl (versus deferring initiation to around 350 cells/μl) results in benefit to the HIV+ person and data from observational studies are inconsistent. Large, clinical endpoint-driven randomized studies to determine the individual health benefits versus risks of earlier ART initiation are sorely needed.

HIV Drug Resistance: Problems and Perspectives

Access to combination antiretroviral treatment (ART) has improved greatly over recent years. At the end of 2011, more than eight million HIV-infected people were receiving ART in low-income and middle-income countries. ART generally works well in keeping the virus suppressed and the patient healthy. However, treatment only works as long as the virus is not resistant against the drugs used. In the last decades, HIV treatments have become better and better at slowing down the evolution of drug resistance, so that some patients are treated for many years without having any resistance problems. However, for some patients, especially in low-income countries, drug resistance is still a serious threat to their health. This essay will review what is known about transmitted and acquired drug resistance, multi-class drug resistance, resistance to newer drugs, resistance due to treatment for the prevention of mother-to-child transmission, the role of minority variants (low-frequency drug-resistance mutations), and resistance due to pre-exposure prophylaxis.