Intensification of a failing regimen with zidovudine may cause sustained virologic suppression in the presence of resensitising mutations including K65R

Low-level viraemia despite emergence of dolutegravir-resistant variants

No abstract available.

Transmitted drug resistance mutations and subtype diversity amongst HIV-1 sero-positive voluntary blood donors in Accra, Ghana

Background

Detection of HIV-1 transmitted drug resistance (TDR) and subtype diversity (SD) are public health strategies to assess current HIV-1 regimen and ensure effective therapeutic outcomes of antiretroviral therapy (ART) among HIV-1 patients. Globally, limited data exist on TDR and SD among blood donors. In this study, drug resistance mutations (DRMs) and SD amongst HIV-1 sero-positive blood donors in Accra, Ghana were characterized.

Methods

Purposive sampling method was used to collect 81 HIV sero-positive blood samples from the Southern Area Blood Center and confirmed by INNO-LIA as HIV-1 and/or HIV-2. Viral RNA was only extracted from plasma samples confirmed as HIV-1 positive. Complementary DNA (cDNA) was synthesized using the RNA as a template and subsequently amplified by nested PCR with specific primers. The expected products were verified, purified and sequenced. Neighbour-joining tree with the Kimura’s 2-parameter distances was generated with the RT sequences using Molecular Evolutionary Genetic Analysis version 6.0 (MEGA 6.0).

Results

Out of the 81 plasma samples, 60 (74%) were confirmed as HIV-1 sero-positive by INNO-LIA HIVI/II Score kit with no HIV-2 and dual HIV-1/2 infections. The remaining samples, 21 (26%) were confirmed as HIV sero-negative. Of the 60 confirmed positive samples, (32) 53% and (28) 47% were successfully amplified in the RT and PR genes respectively. Nucleotide sequencing of amplified samples revealed the presence of major drug resistance mutations in two (2) samples; E138A in one sample and another with K65R. HIV-1 Subtypes including subtypes A, B, CRF02_AG and CRF09_cpx were found.

Conclusion

This study found major drug resistance mutations, E138A and K65R in the RT gene that confer high level resistance to most NNRTIs and NRTI respectively. CRF02_AG was most predominant, the recorded percentage of subtype B and the evolutionary relationship inferred by phylogenetic analysis may suggest possible subtype importation. However, a more prospective and detailed analysis is needed to establish this phenomenon. The data obtained would inform the selection of drugs for ART initiation to maximize therapeutic options in drug-naïve HIV-1 patients in Ghana.

Prevalence of K65R in patients treated with tenofovir disoproxil fumarate: recommendations based on the Frankfurt HIV Cohort Study Resistance Database (FHCS-RD)

Mutations in the genome of HIV-1 can compromise the success of antiretroviral treatments (ARTs) in HIV-1-infected individuals. The Frankfurt HIV Cohort Study Resistance Database (FHCS-RD) has previously documented a decline in the burden of resistance-associated mutations (RAMs) following the implementation of several new antiretroviral therapy regimens in 2007. In the current study, the annual burden of RAMs documented in the FHCS-RD in 2005-2013 was set in relation to the annual number of all cohort patients, drug regimens, available resistance tests, and prevalence for each RAM on relevant codons of reverse transcriptase (RT) and protease (PR) genes. A specific focus was put on the prevalence of the tenofovir disoproxil fumarate (TDF) signature mutation K65R in HIV-1 RT in relation to the application of TDF within ART. Between 2005 and 2012, a total of 4423 HIV genotyping data sets from 4509 patients were analysed. All mutations show a consistent decline, and the most impressive decrease was observed for thymidine analogue mutations (TAMs). The frequency of non-TAMs and PR mutations also decreased, but generally to a lower extent. The prevalence of K65R decreased from 2.6 % in 2005 to 0.2 % in 2012 despite increased use of TDF-containing ART. Both the improved strategic use of TDF in ARTs and generally more effective ART regimens may have resulted in decreasing RAM prevalences in FHCS-RD since 2007. These trends challenge the cost-effectiveness of resistance testing prior to failing ART.

Zidovudine as modern day salvage therapy for HIV infection

Resistance to the first-line NRTIs, tenofovir and emtricitabine, does not generally confer resistance to zidovudine. The objective of this study was to describe the efficacy of zidovudine as modern day salvage antiretroviral therapy. This was a single-center, retrospective, observational, cohort study. Adult HIV-positive patients prescribed a zidovudine-containing regimen between 2005 and 2010 were identified from a computer database. All patients had failed at least one prior antiretroviral regimen before zidovudine. The primary outcome measure was virologic success at 24 weeks. Other efficacy and safety outcomes were determined, including virologic success at 48 and 96 weeks, CD4 count change from baseline, and incidence of adverse effects. Sixty-nine subjects were enrolled. The mean age was 43 years, 70% were male, and 85.5% were black. Most patients were highly antiretroviral experienced. At 24 weeks, 63.8% and 72.5% of patients achieved HIV RNA less than 50 and 400 c/mL, respectively. The median change in CD4 count from baseline to week 24 was +70 cells/mm(3). The percent of patients who discontinued zidovudine due to adverse effects was 10%. In this highly treatment-experienced population, zidovudine as part of a salvage regimen appeared effective. Gastrointestinal adverse effects were reported, but zidovudine-associated metabolic effects were uncommon, suggesting zidovudine was generally well tolerated.

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.

Clinical management of HIV drug resistance

Combination antiretroviral therapy for HIV-1 infection has resulted in profound reductions in viremia and is associated with marked improvements in morbidity and mortality. Therapy is not curative, however, and prolonged therapy is complicated by drug toxicity and the emergence of drug resistance. Management of clinical drug resistance requires in depth evaluation, and includes extensive history, physical examination and laboratory studies. Appropriate use of resistance testing provides valuable information useful in constructing regimens for treatment-experienced individuals with viremia during therapy. This review outlines the emergence of drug resistance in vivo, and describes clinical evaluation and therapeutic options of the individual with rebound viremia during therapy.