Global burden of transmitted HIV drug resistance and HIV-exposure categories: a systematic review and meta-analysis

Distinct region-specific neutralization profiles of contemporary HIV-1 clade C against best-in-class broadly neutralizing antibodies

While broadly neutralizing antibodies (bnAbs) have been clinically shown to prevent HIV-1 acquisition, their relative effectiveness against regionally relevant HIV-1 forms is not clear. In the present study, we examined the extent of neutralization susceptibility of contemporary HIV-1 Indian clade C at a population level along with a head-to-head comparison with that from South Africa against a panel of clinically relevant best-in-class bnAbs. Env-pseudotyped viruses encoding HIV-1 India clade C env were found to be best neutralized by the V3 glycan-directed bnAbs (10-1074 and BG18) and select CD4 binding site (CD4bs)-directed bnAbs (VRC07, N6, and 1-18); however, they demonstrated significant resistance to V1/V2 apex-directed bnAbs. Interestingly, the magnitude of the neutralization sensitivity differed between contemporary India and South Africa clade C. Neutralization resistance to key bnAbs was observed to be associated with differences in residues on Env that form bnAb contact sites, gp120 loop lengths, and potential N-linked glycans. Notably, the second generation CD4bs bnAbs (VRC07, N6, 1-18) showed neutralization of VRC01- and 3BNC117-resistant viruses but with two- to sevenfold reduced potency compared to the VRC01-sensitive counterparts, likely due to the enrichment of resistance-associated residues observed in loop D. Predictive analysis indicated that the combination of BG18, N6, and PGDM1400 can provide over 95% neutralization coverage of contemporary India clade C at 1 µg/mL (IC80), an observation distinct from that observed with Africa clade C. Our study clearly highlights that both the complementarity of bnAb classes and the regionally relevant HIV-1 forms are important in achieving clinical effectiveness.IMPORTANCEWhile the development of vaccines to prevent HIV infection remains a global priority, their potential effectiveness is limited by the extraordinarily diversified circulating forms of HIV-1. The prospect of best-in-class broadly neutralizing antibodies (bnAbs) as a potential prevention option has been demonstrated in several studies, including the phase 2b Antibody-Mediated Prevention trials; however, to be broadly applicable, bnAbs will need to overcome the substantial variability of HIV env circulating globally, beyond the regions where efficacy trials are conducted. The present study highlights that the region-specific contemporary HIV-1 clade C viruses not only vary in their degree of susceptibility to the best-in-class clinically relevant bnAbs, but also are evolving at a population level to become increasingly resistant to the best-in-class bnAbs. Overall, the outcome of this study highlights the need for periodic assessment of sequence and neutralization profiles of the circulating regionally relevant HIV-1 forms toward prioritizing the bnAb combination suitable for effective intervention.

Evaluating HIV drug resistance in the middle East and North Africa and its associated factors: a systematic review

OBJECTIVE

One of the obstacles to achieving successful treatment of HIV infections is the development and spread of mutations linked to resistance. Thus, it is important to monitor the prevalence and occurrence of drug resistance in HIV consistently. This study aimed to investigate how drug resistance affects the effectiveness of ART.

METHODS

This systematic review focused on surveying ART resistance in both treatment-naïve and treatment-experienced PWH from 2004 to 2024.

RESULTS

Out of 101 potential publications, 41 studies were included in this review. ART-experienced PWH in MENA countries commonly receive a regimen consisting of two NRTI drugs in combination with one NNRTI drug. The most frequent mutations were found in NRTIs (M184V, D67N, V75M, M41L, and T69N), NNRTIs (K103N, K101E, V106A, and G190S), and PIs (M36I and H69K). The ART-experienced groups in Israel and Iran presented the highest rates of resistance, reaching 52.78% and 43.03%, respectively, whereas the ART-naïve group in Turkey presented a resistance rate of 53.57%. The most prevalent HIV-1 subtypes in the region were B, CRF35-AD, CRF01-AE, A1, CR02-AG, C, and D. A high frequency of drug resistance mutations, such as M184V and K103N/S, was observed in the CRF35-AD, A, and C subtypes.

CONCLUSION

This is the first report to provide deep insight into ART resistance patterns in the MENA region among both ART-naïve and ART-experienced PWH. The results revealed a significant occurrence of drug resistance to RTIs, PIs, and INSTIs among both groups. This finding highlights the importance of prescribing the INTIs in native and PWH with resistance to RTIs and/or PIs to increase the chance of response to ART as well as regular monitoring of resistance to ART in MENA countries. This also involves identifying the key factors contributing to drug resistance, including inadequate adherence to ART and a lack of adequate monitoring systems to prevent treatment failure. Since the MENA region is significant as an economic challenge, PWH with poor adherence to ART medication and insufficient monitoring systems may hinder successful infection control; therefore, HIV control strategies may prevent viruses from spreading in other countries.

CLINICAL TRIAL NUMBER

Not applicable.

Stability in human serum and plasma of the HIV peptide drug candidate CIGB-210 and improved variants

The peptide CIGB-210 inhibits HIV replication, inducing a rearrangement of vimentin intermediate filaments. The assessment of the in vitro serum and plasma stability of this peptide is important to develop an optimal pharmacological formulation. A half-life of 17.68 ± 0.59 min was calculated for CIGB-210 in human serum by reverse-phase high-performance liquid chromatography (HPLC) and mass spectrometry (MS). Eight metabolites of CIGB-210 were identified with this methodology, all of them lacking the N-terminal moiety. A previously developed CIGB-210 in-house competitive ELISA was used to compare the stability of CIGB-210 derivatives containing either D-amino acids, acetylation at the N-terminus, or both modifications. The half-life of CIGB-210 in serum was five times higher when measured by ELISA than by HPLC/MS, and twice higher in plasma as compared to serum. The substitution of D-asparagine on position 6 doubled the half-life, while D-amino acids on positions 8 and 9 did not improve the stability. The acetylation of the N-terminus resulted in a 24-fold more stable peptide in plasma. The positive effect of N-terminal acetylation on CIGB-210 serum stability was confirmed by the HPLC/MS method, as the half-life of the peptide was not reached after 2 h of incubation, which represents more than a 6.8-fold increase in the half-life with respect to the original peptide.

Detection of Antiretroviral Drug-Resistant Mutations and HIV-1 Subtypes in Circulation Among Men Who Have Sex With Men, SEM Females, and Female Sex Workers: Results of Vietnam's HIV Sentinel Surveillance Plus System, 2018-2020

BACKGROUND

HIV drug resistance can reduce the effectiveness of antiretroviral drugs in preventing morbidity and mortality, limit options for treatment, and prevention. Our study aimed to assess HIV-1 subtypes and HIV drug resistance among key populations in HIV Sentinel Surveillance Plus Behavior in 2018 and 2020.

METHODS

One-stage venue-based cluster sampling was used to recruit participants at hotspots identified for men who have sex with men (MSM) in 7 provinces and sexual minority females and female sex workers (FSW) in 13 provinces. Participants completed a standard questionnaire about risk and preventive behaviors, and antiretroviral therapy history, and provided intravenous blood for HIV testing. HIV drug resistance testing was conducted on HIV-positive samples with viral load >1000 copies/mL.

RESULTS

A total of 185 of 435 (42.5%) HIV-positive samples had viral load ≥1000 copies/mL, of which 130 of 136 from MSM and 26 of 49 from FSW were successfully sequenced. Six HIV-1 subtypes were detected (CRF01_AE, A, CRF07/08_BC, B, C, CRF25_cpx), with CRF01_AE (82.7%, 129/156) the most common. Drug resistance mutations were detected in 16.7% of participants overall (26/156), in 15.4% (20/130) of MSM, and in 23.1% (6/26) of FSW. Mutations associated with resistance to non-nucleoside reverse transcriptase inhibitor (NNRTI) were the most frequently detected (73.1%, 19/26). The high level of resistance was presented in NNRTI and nucleoside reverse transcriptase inhibitors classes. There are 10 major resistance mutations detected with nucleoside reverse transcriptase inhibitors (M184VI-25.0%, K65KR-50.0%, Y115F-25%), NNRTI (K103N-21.1%, E138A-10.5%, V106M-5.3%, K101E-5.3%, G190A-5.3%), protease inhibitors (L33F-40.0%, M46L-20.0%).

CONCLUSIONS

Vietnam's HIV Sentinel Surveillance Plus system identified an emerging strain of HIV-1 and mutations associated with resistance to multiple drug classes among MSM and FSW.

Beware of resistance to 2nd-generation integrase inhibitors: A systematic meta-analysis of HIV-1 integrase inhibitors resistance and drug resistance mutations

OBJECTIVE

Assessing the prevalence of resistance and drug resistance mutations (DRMs) in HIV/AIDS patients towards integrase strand transfer inhibitors (INSTIs), particularly the 2nd-generation INSTIs, provides evidence for rational clinical drug use.

METHODS

A systematic search was conducted on five databases to identify relevant literature reporting original data on INSTIs resistance. Meta-analyses, cumulative meta-analyses, subgroup analyses and meta-regression analyses were performed using selected models based on the results of heterogeneity tests.

RESULTS

A total of 81 studies were included in this analysis. The prevalence of pre-treatment drug resistance (PDR) to 1st-generation INSTIs and 2nd-generation INSTIs were 0.41% (95% CI: 0.19%-0.70%) and 0.04% (95% CI: 0.00%-0.13%), respectively; and the prevalence of acquired drug resistance (ADR) were 7.60% (95% CI: 3.54%-12.92%) and 4.93% (95% CI: 1.78%-9.36%), respectively, and ADR showed an increasing and then decreasing time trend. The results of subgroup analyses showed differences in ADR to 2nd-generation INSTIs between regions and economic levels, with the highest ADR of 12.83% (95% CI: 3.24%-27.17%) in the European region. DRMs varied among HIV patients and reduced drug sensitivity to varying degrees.

CONCLUSION

The prevalence of PDR and DRMs in 2nd-generation INSTIs is currently low, but as the use of DTG-based ART expands, population-level drug resistance monitoring and individual-level genetic testing should be strengthened in order to maximise treatment efficacy. Additionally, attention should be paid to ADR to INSTIs to provide personalised treatments for HIV-infected patients.

Combating antimicrobial resistance in malaria, HIV and tuberculosis

Antimicrobial resistance poses a significant threat to the sustainability of effective treatments against the three most prevalent infectious diseases: malaria, human immunodeficiency virus (HIV) infection and tuberculosis. Therefore, there is an urgent need to develop novel drugs and treatment protocols capable of reducing the emergence of resistance and combating it when it does occur. In this Review, we present an overview of the status and underlying molecular mechanisms of drug resistance in these three diseases. We also discuss current strategies to address resistance during the research and development of next-generation therapies. These strategies vary depending on the infectious agent and the array of resistance mechanisms involved. Furthermore, we explore the potential for cross-fertilization of knowledge and technology among these diseases to create innovative approaches for minimizing drug resistance and advancing the discovery and development of new anti-infective treatments. In conclusion, we advocate for the implementation of well-defined strategies to effectively mitigate and manage resistance in all interventions against infectious diseases.

Emergence failure of early epidemics: A mathematical modeling approach

Epidemic or pathogen emergence is the phenomenon by which a poorly transmissible pathogen finds its evolutionary pathway to become a mutant that can cause an epidemic. Many mathematical models of pathogen emergence rely on branching processes. Here, we discuss pathogen emergence using Markov chains, for a more tractable analysis, generalizing previous work by Kendall and Bartlett about disease invasion. We discuss the probability of emergence failure for early epidemics, when the number of infected individuals is small and the number of the susceptible individuals is virtually unlimited. Our formalism addresses both directly transmitted and vector-borne diseases, in the cases where the original pathogen is 1) one step-mutation away from the epidemic strain, and 2) undergoing a long chain of neutral mutations that do not change the epidemiology. We obtain analytic results for the probabilities of emergence failure and two features transcending the transmission mechanism. First, the reproduction number of the original pathogen is determinant for the probability of pathogen emergence, more important than the mutation rate or the transmissibility of the emerged pathogen. Second, the probability of mutation within infected individuals must be sufficiently high for the pathogen undergoing neutral mutations to start an epidemic, the mutation threshold depending again on the basic reproduction number of the original pathogen. Finally, we discuss the parameterization of models of pathogen emergence, using SARS-CoV1 as an example of zoonotic emergence and HIV as an example for the emergence of drug resistance. We also discuss assumptions of our models and implications for epidemiology.

Prevalence of transmitted drug resistance and phylogenetic analysis of HIV-1 among antiretroviral therapy-naïve patients in Northern Vietnam from 2019 to 2022

Since the rapid expansion of antiretroviral therapy (ART) for HIV, transmitted drug resistance (TDR) has become a major concern in Vietnam. HIV services there are transitioning to be covered by social insurance. Access to pre-exposure prophylaxis (PrEP) is being expanded to tackle the growing HIV epidemic among men who have sex with men. Therefore, a cross-sectional study was conducted at 10 ART facilities in Northern Vietnam from 9th December 2019 to 9th June 2022 to investigate the prevalence and pattern of TDR among ART-naïve people living with HIV (PLWH). TDR mutations were defined according to the World Health Organization 2009 List of Mutations for Surveillance of Transmitted Drug Resistant HIV Strains. Mutation transmission dynamics and TDR clusters were investigated via phylogenetic analysis. We enrolled 391 ART-naïve PLWH. The overall TDR prevalence was 4.6%, with an annual prevalence of 6.0% in 2019/2020, 4.8% in 2021, and 1.3% in 2022. TDR mutations to non-nucleoside reverse transcriptase inhibitors (2.8%), including K103N were the most common. Less commonly, the protease inhibitor-associated mutation M46I and mutations to nucleoside reverse transcriptase inhibitors, including M184V/ I, were observed. CRF01_AE was the most common subtype (77.0%). CRF07_BC (14.3%), which had been rare in Vietnam, was also observed. No genetic association was observed between HIV-1 sequences with TDR mutations. In conclusion, the overall prevalence of TDR was stably low in this region. The phylogenetic tree suggests that TDR clusters have not formed. Continuous monitoring of HIV TDR and strains is crucial to maintaining ART and PrEP efficacy.

Characterizing the Development of Research Landscapes in Substance Use and HIV/AIDS During 1990 to 2021

Mitigating the impacts of Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome (HIV/AIDS) and substance use requires comprehensive and systematic thinking in designing interventions and developing policies. This study describes the growth of research publications from 1991 to 2021 in the Web of Science database and points out current research landscapes in the fields of HIV/AIDS and substance use. Latent Dirichlet Allocation was used for classifying 21 359 papers into corresponding topics. The most common topics were HIV transmission, HIV infection, quality of life and mental health of substance users, and the biomedical effect of substance use. Emerging research landscapes include vulnerabilities of people who inject drugs to HIV transmission and related health problems. This study found a lack of research on health services, interdisciplinary and inter-sectoral in combination with clinical evaluation and treatment services. Future investment and implementation of HIV/AIDS and substance use programs should focus on research of health services and clinical evaluation, especially context-specific interventions.

HIV treatment, antiretroviral adherence and AIDS mortality in people who inject drugs: a scoping review

BACKGROUND

People who inject drugs (PWID) are a key population for the prevention and care of HIV infection.

METHODS

This scoping review covers recent (post-2010) systematic reviews on engagement of PWID in sequential stages of HIV care from uptake, to achieving viral suppression, and to avoiding AIDS-related mortality.

RESULTS

We found that data on engagement of PWID into antiretroviral therapy (ART) were particularly scarce, but generally indicated very low engagement in ART. Studies of adherence and achieving viral suppression showed varying results, with PWID sometimes doing as well as other patient groups. The severity of social, medical and psychiatric disability in this population poses significant treatment challenges and leads to a marked gap in AIDS mortality between PWID and other population groups.

CONCLUSIONS

Given the multi-level barriers, it will be difficult to reach current targets (UNAIDS fast-track targets of 95-95-95) for ART for PWID in many locations. We suggest giving priority to reducing the likelihood that HIV seropositive PWID will transmit HIV to others and reducing morbidity and mortality from HIV infection and from other comorbidities.

Disparity of HIV-1 Pretreatment Drug Resistance in Men Who Have Sex With Men and the Heterosexual Population in Guangxi, China

Background

The prevalence of human immunodeficiency type 1 (HIV-1) pretreatment drug resistance (PDR) in men who have sex with men (MSM) in Guangxi remains unclear, and its effect on antiretroviral therapy (ART) needs to be further studied.

Methods

Individuals newly diagnosed with HIV in Guangxi from 2016 to 2020, which mainly included MSM and the heterosexual (HES) population, were recruited in this study. Pol sequences were sequenced to analyze PDR and construct a genetic network. The risk factors for PDR and the effect on ART were respectively analyzed.

Results

The PDR of MSM in Guangxi was 4.7% (34/716), consisting of nonnucleoside reverse transcriptase inhibitors (3.5%), protease inhibitors (0.8%), integrase strand transfer inhibitors (0.7%), and nucleoside reverse transcriptase inhibitors (0.4%), and lower than that of HES (9.3% [77/827]). The subtype was associated with PDR, and MSM was lower than HES (CRF01_AE: 3.0% vs 8.0%; CRF07_BC: 4.1% vs 7.2%). CRF55_01B (adjusted odds ratio [aOR], 3.35) was a risk factor for PDR in MSM, while CRF08_BC (aOR, 2.34) and older (aOR, 2.75) were risk factors for PDR in HES. Six of 18 (33.3%) PDR of MSM in the network connected to each other, lower than that of HES (61.1% [22/36]). CRF55_01B (aOR, 5.69) was a risk factor for PDR transmission in MSM, while CRF08_BC (aOR, 4.08) was a risk factor in HES. Pretreatment CD4⁺ T-cell count, age, infection route, and subtype were associated with recovery of CD4⁺ count and suppression of viral load.

Conclusions

The prevalence of PDR was different between MSM and HES, which may be associated with subtype. Thus, the monitoring of subtype and PDR should be strengthened.

HIV drug resistance in a community-randomized trial of universal testing and treatment: HPTN 071 (PopART)

INTRODUCTION

Universal HIV testing and treatment (UTT) has individual and public health benefits. HPTN 071 (PopART), a community-randomized trial in Zambia and South Africa, demonstrated that UTT decreased HIV incidence. This endpoint was assessed in a cohort of >48,000 randomly selected adults in the study communities. We evaluated the impact of UTT on HIV drug resistance in this cohort and compared other resistance-related outcomes in participants with recent versus non-recent HIV infection.

METHODS

Two years after the start of HPTN 071 (2016-2017), 6259 participants were HIV positive and 1902 were viremic (viral load >400 copies/ml). HIV genotyping and antiretroviral (ARV) drug testing were performed for viremic participants in three groups: seroconverters (infected <1 year), non-seroconverters (infected >1 year, random subset) and participants with unknown duration of infection (random subset). A two-stage cluster-based approach was used to assess the impact of the study intervention on drug resistance. Treatment failure was defined as being viremic with ARV drugs detected. Participants were classified as ARV naïve based on self-report and ARV drug testing.

RESULTS

Genotyping results were obtained for 758 participants (143 seroconverters; 534 non-seroconverters; and 81 unknown duration of infection). The estimated prevalence of resistance in the study communities was 37% for all viremic persons and 11% for all HIV-positive persons. There was no association between UTT and drug resistance. Resistance was detected in 14.0% of seroconverters and 40.8% of non-seroconverters (non-nucleoside reverse transcriptase inhibitor resistance: 14.0% and 39.9%; nucleoside/nucleotide reverse transcriptase inhibitor resistance: 0.7% and 15.5%; protease inhibitor resistance: 0% and 1.9%; multi-class resistance: 0.7% and 16.1%, respectively). ARV drugs were detected in 2/139 (1.4%) of seroconverters and 94/534 (17.6%) of non-seroconverters tested. These participants were classified as failing ART; 88 (93.6%) of the non-seroconverters failing ART had resistance. Mutations used for surveillance of transmitted drug resistance were detected in 10.5% of seroconverters and 15.1% of non-seroconverters who were ARV naive.

CONCLUSIONS

UTT was not associated with an increase in drug resistance in this cohort. Higher rates of drug resistance and multi-class resistance were observed in non-seroconverters compared to seroconverters.

Reduced and highly diverse peripheral HIV-1 reservoir in virally suppressed patients infected with non-B HIV-1 strains in Uganda

BACKGROUND

Our understanding of the peripheral human immunodeficiency virus type 1 (HIV-1) reservoir is strongly biased towards subtype B HIV-1 strains, with only limited information available from patients infected with non-B HIV-1 subtypes, which are the predominant viruses seen in low- and middle-income countries (LMIC) in Africa and Asia.

RESULTS

In this study, blood samples were obtained from well-suppressed ART-experienced HIV-1 patients monitored in Uganda (n = 62) or the U.S. (n = 50), with plasma HIV-1 loads < 50 copies/ml and CD4+ T-cell counts > 300 cells/ml. The peripheral HIV-1 reservoir, i.e., cell-associated HIV-1 RNA and proviral DNA, was characterized using our novel deep sequencing-based EDITS assay. Ugandan patients were slightly younger (median age 43 vs 49 years) and had slightly lower CD4+ counts (508 vs 772 cells/ml) than U.S. individuals. All Ugandan patients were infected with non-B HIV-1 subtypes (31% A1, 64% D, or 5% C), while all U.S. individuals were infected with subtype B viruses. Unexpectedly, we observed a significantly larger peripheral inducible HIV-1 reservoir in U.S. patients compared to Ugandan individuals (48 vs. 11 cell equivalents/million cells, p < 0.0001). This divergence in reservoir size was verified measuring proviral DNA (206 vs. 88 cell equivalents/million cells, p < 0.0001). However, the peripheral HIV-1 reservoir was more diverse in Ugandan than in U.S. individuals (8.6 vs. 4.7 p-distance, p < 0.0001).

CONCLUSIONS

The smaller, but more diverse, peripheral HIV-1 reservoir in Ugandan patients might be associated with viral (e.g., non-B subtype with higher cytopathicity) and/or host (e.g., higher incidence of co-infections or co-morbidities leading to less clonal expansion) factors. This highlights the need to understand reservoir dynamics in diverse populations as part of ongoing efforts to find a functional cure for HIV-1 infection in LMICs.

Evolution of HIV-1 Surveillance Drug Resistance Mutations Over 10 Years in New South Wales, Australia

New South Wales has the greatest burden of HIV in Australia, with 2012 and 2013 recording the highest rates of new diagnoses in 20 years. Concurrently, there has been significant changes in antiretroviral treatments and testing paradigms. We compiled a statewide resistance database to characterize changes in HIV-1 resistance mutations over time. Genotypic antiretroviral resistance testing (GART) was performed on request at three reference laboratories using commercial and in-house methods. In total, 7629 HIV-1 polymerase sequences obtained from GART from 2004 to 2013 were retrospectively collated, reformatted, de-identified, and analyzed using Stanford HIVdb program 7.0 and the 2009 World Health Organization (WHO) surveillance drug resistance mutations (SDRMs). Analyses were performed on subgroups of known treatment naives, treatment experienced, and seroconverters. There has been a decrease in overall rates of prevalent drug resistance mutations from 57.8% in 2004 to 21% in 2013. Dual and triple class resistance mutations have decreased from 32.7% in 2004 to 5.8% in 2013 and 16.4% to 1.2%, respectively. In treatment-naive individuals (n = 450), the frequency of protease inhibitor (PI) mutations remains low at 2.7%. In seroconverters, rates of transmitted drug resistance (TDR) are 6.6%, 3%, 3%, and 1.5% for overall, PI, non-nucleoside reverse transcription inhibitor (NNRTI), and NRTI, respectively. In treatment experienced, rates remain stable with 36.0%, 18.9%, 29.1%, and 6.4% for overall, NNRTI, NRTI, and PI mutations. The most common mutations in treatment experienced occurred at position M184, T215 (NRTI); K103 (NNRTI); I54 (PI). Apparent decreases in prevalent SDRMs can be attributed to changes in GART testing indications over time. In treatment-naive and -experienced subgroups, rates have been stable with low rates of TDR in seroconverters.

Diversity of HIV-1 subtypes and transmitted drug-resistance mutations among minority HIV-1 variants in a Turkish cohort

BACKGROUND

The World Health Organization (WHO) recommends the surveillance of transmitted drug resistance mutations (TDRMs) to ensure the effectiveness and sustainability of HIV treatment programs.

OBJECTIVE

Our aim was to determine the TDRMs and evaluate the distribution of HIV-1 subtypes using and compared next-generation sequencing (NGS) and Sanger-based sequencing (SBS) in a cohort of 44 antiretroviral treatment-naïve patients.

METHODS

All samples that were referred to the microbiology laboratory for HIV drug resistance analysis between December 2016 and February 2018 were included in the study. After exclusions, 44 treatment-naive adult patients with a viral load of >1000 copies/mL were analyzed. DNA sequencing for reverse transcriptase and protease regions was performed using both DeepChek ABL single round kit and Sanger-based ViroSeq HIV-1 Genotyping System. The mutations and HIV-1 subtypes were analyzed using the Stanford HIVdb version 8.6.1 Genotypic Resistance software, and TDRMs were assessed using the WHO surveillance drug-resistance mutation database. HIV-1 subtypes were confirmed by constructing a maximum-likelihood phylogenetic tree using Los Alamos IQ-Tree software.

RESULTS

NGS identified nucleos(t)ide reverse transcriptase inhibitor (NRTI)-TDRMs in 9.1% of the patients, non-nucleos(t)ide reverse transcriptase inhibitor (NNRTI)-TDRMs in 6.8% of the patients, and protease inhibitor (PI)-TDRMs in 18.2% of the patients at a detection threshold of ≥1%. Using SBS, 2.3% and 6.8% of the patients were found to have NRTI- and NNRTI-TDRMs, respectively, but no major PI mutations were detected. M41L, L74I, K65R, M184V, and M184I related to NRTI, K103N to NNRTI, and N83D, M46I, I84V, V82A, L24I, L90M, I54V to the PI sites were identified using NGS. Most mutations were found in low-abundance (frequency range: 1.0% - 4.7%) HIV-1 variants, except M41L and K103N. The subtypes of the isolates were found as follows; 61.4% subtype B, 18.2% subtype B/CRF02_AG recombinant, 13.6% subtype A, 4.5% CRF43_02G, and 2.3% CRF02_AG. All TDRMs, except K65R, were detected in HIV-1 subtype B isolates.

CONCLUSION

The high diversity of protease site TDRMs in the minority HIV-1 variants and prevalence of CRFs were remarkable in this study. All minority HIV-1 variants were missed by conventional sequencing. TDRM prevalence among minority variants appears to be decreasing over time at our center.

High prevalence of HIV-1 transmitted drug resistance and factors associated with time to virological failure and viral suppression in Taiwan

BACKGROUND

Integrase strand transfer inhibitor (InSTI)-based regimens have become the major first-line treatment for HIV-1-infected patients in Taiwan. Transmitted drug resistance (TDR) and several clinical characteristics are associated with time to virological failure or viral suppression; however, these have not been investigated in Taiwan.

OBJECTIVES

To determine the impact of several factors on treatment outcomes in HIV-1-infected patients in Taiwan.

METHODS

The cohort included 164 HIV-1 treatment-naive patients in Taiwan from 2018 to 2020. Blood specimens were collected to determine the genotypic drug resistance using the Stanford University HIV drug resistance database. Cox proportional hazards models were used to identify factors associated with time to virological failure or viral suppression.

RESULTS

The prevalence of TDR in Taiwan was 27.4% and an increasing trend was seen from 2018 to 2020. TDR mutations related to NNRTIs were the most prevalent (21%) while TDR to InSTIs remained at a relatively low level (1.3%). A baseline HIV-1 viral load of ≥100 000 copies/mL was associated with a shorter time to virological failure [multivariate hazard ratio (mHR) 7.84; P = 0.018] and longer time to viral suppression (mHR 0.46; P < 0.001). Time to viral suppression was shorter in patients receiving InSTI-based regimens (mHR 2.18; P = 0.006). Different InSTI-based regimens as initial treatment did not affect the treatment outcomes.

CONCLUSIONS

This study found an increasing trend of HIV-1 TDR prevalence from 2018 to 2020 in Taiwan. Baseline HIV-1 viral load and receiving InSTI-based regimens are important factors associated with time to virological failure or viral suppression.

Three-year study of pre-existing drug resistance substitutions and efficacy of bictegravir/emtricitabine/tenofovir alafenamide in HIV-1 treatment-naive participants

OBJECTIVES

Two Phase 3, randomized, double-blind, active-controlled studies of initial HIV-1 treatment demonstrated that bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF) was non-inferior to dolutegravir/abacavir/lamivudine (DTG/ABC/3TC; Study 1489) or to DTG+F/TAF (Study 1490) through 144 weeks. In both studies, there was no emergent resistance to study drugs. Here, the 3 year resistance analysis and impact of baseline resistance substitutions on treatment response are described.

METHODS

Population sequencing of HIV-1 protease and reverse transcriptase (RT) was performed at screening. Retrospective baseline next generation sequencing of protease, RT and integrase (IN) was analysed at a ≥ 15% cutoff. Resistance analyses were performed on participants with confirmed viral rebound of HIV-1 RNA ≥200 copies/mL through Week 144 or last visit who did not resuppress to <50 copies/mL while on study drug.

RESULTS

Transmitted primary drug resistance substitutions were present in the following proportions of participants: integrase strand transfer inhibitor (INSTI) resistance (-R) in 1.3% (17/1270) of participants; NRTI-R in 2.7% (35/1274); NNRTI-R in 14.1% (179/1274); and PI-R in 3.5% (44/1274). These pre-existing resistance substitutions not associated with study drug did not affect treatment outcomes. One participant in the B/F/TAF group had pre-existing bictegravir and dolutegravir resistance substitutions (Q148H+G140S in integrase) at baseline and suppressed and maintained HIV-1 RNA <50 copies/mL through Week 144. In total, 21 participants qualified for resistance testing [1.3% (8/634) B/F/TAF; 1.9% (6/315) DTG/ABC/3TC; 2.2% (7/325) DTG+F/TAF]; none had emergent resistance to study drugs.

CONCLUSIONS

Treatment with B/F/TAF, DTG/ABC/3TC, or DTG+F/TAF achieved high, durable rates of virological suppression in HIV-1 treatment-naive participants. The presence of pre-existing resistance substitutions did not affect treatment outcomes, and there was no treatment-emergent resistance.

Current Pharmaceutical Aspects of Synthetic Quinoline Derivatives

Quinoline derivatives are considered broad-spectrum pharmacological compounds that exhibit a wide range of biological activities. Integration of quinoline moiety can improve its physical and chemical properties and also pharmacological behavior. Due to its wide range of pharmaceutical applications, it is a very popular compound to design new drugs for the treatment of multiple diseases like cancer, dengue fever, malaria, tuberculosis, fungal infections, AIDS, Alzheimer's disease and diabetes. In this review, our major focus is to pay attention to the biological activities of quinoline compounds in the treatment of these diseases such as anti-viral, anti-cancer, anti-malarial, antibacterial, anti-fungal, anti-tubercular and anti-diabetic.

Transmitted drug resistance among HIV-1 drug-naïve patients in Greece

OBJECTIVES

Despite the success of antiretroviral treatment (ART), the persisting transmitted drug resistance (TDR) and HIV genetic heterogeneity affect the efficacy of treatment. This study explored the prevalence of TDR among ART-naïve HIV patients in Greece during the period 2016-2019.

METHODS

Genotypic resistance testing was available for 438 ART-naïve HIV patients. Multivariable Poisson regression models were fitted.

RESULTS

The majority of patients were male, and there was a slight predominance of Hellenic (26.5%) over non-Hellenic (21.9%) nationality. The prevalence of TDR was 7.8%. There was a predominance of mutations for non-nucleoside reverse-transcriptase inhibitors (5.7%) over nucleoside reverse-transcriptase inhibitors (0.2%). No mutations to protease inhibitors were detected. The prevalence of resistance was 22.1% based on all mutations identified through the HIVdb interpretation system. The most frequent resistance sites were E138A (9.6%), K103N (6.4%), and K101E (2.1%). The majority of detected mutations were confined to subtype A (52.6%), followed by B (19.6%). Non-Hellenic nationality was significantly associated with an increased risk of TDR (relative risk 1.32, 95% confidence interval 1.04-1.69).

CONCLUSIONS

Non-B HIV infections predominate in Greece, with an increasing trend in recent years. The prevalence of TDR remains stable. Ongoing surveillance of resistance testing is needed to secure the long-term success of ART.

Failure is not an option: Barriers to HIV treatment adherence in Kampala, Uganda

This study seeks to investigate challenges to combined antiretroviral therapy (cART) treatment adherence and treatment outcomes in Kampala, Uganda. Data was collected from a survey administered to two cohorts of patients with human immunodeficiency virus type 1 (HIV-1) receiving care and cART from the Joint Clinical Research Center (JCRC) in Kampala. Cohort I consisted of 93 individuals successfully treated on cART for a period of three years, while Cohort II consisted of 56 individuals who have experienced treatment failure with first-line cART within two years. We hypothesize that distance to the treatment facility would be a predictor of poor adherence and thus treatment failure. However, results suggested otherwise, whereby participants living more than 2 h away from their treatment facility were actually less likely to miss their daily dose of cART (OR = 0.33, p < .05), compared to those living in proximity to the treatment center. Further, high-income employment (OR = 3.82, p < .05) and partnered relationship status (OR = 4.28, p < .05) were predicted to increase the probability of missing doses. These findings may be explained by the deep-seated stigma which has remained pervasive in the lives of HIV-positive population in Kampala, even 30 years after the peak of the HIV/AIDS epidemic.

Prevalence of pretreatment HIV drug resistance in key populations: a systematic review and meta-analysis

INTRODUCTION

WHO's 2019 report on HIV drug resistance (HIVDR) documents a high prevalence of pretreatment drug resistance (PDR) among populations initiating first-line antiretroviral therapy (ART) in low- and middle-income countries (LMIC). However, systematic evidence on the prevalence of PDR among key populations remains limited. We performed a systematic review to characterize levels of PDR in key population groups and compared them to levels of PDR in the "general population" across different geographical regions.

METHODS

Ten electronic databases were searched for papers published until February 2019 that included predefined search terms. We included studies that reported the number of successfully tested genotypes and the number of genotypes with drug resistance mutations among antiretroviral therapy treatment naïve people, recently infected people, or people initiating first-line ART from key populations. To assess the prevalence of PDR for each key population, we pooled estimates using random-effects meta-analysis of proportions. Where possible, we computed the differences in the odds of PDR (any, and by drug class) present in each key population compared to the "general population". The I2 statistic (a measure of heterogeneity between studies) is reported.

RESULTS AND DISCUSSION

A total of 332 datasets (from 218 studies) and 63,111 people with successful HIVDR genotyping were included in the analysis. The pooled prevalence estimate of any PDR was high among men who have sex with men (13.0%, 95% CI 11.0 to 14.0%, I2  = 93.19), sex workers (17.0%, 95% CI 6.0 - 32.0, I2  = 87.31%) and people in prisons (18.0%, 95% CI 11.0 to 25.0, I2  = 70.18%), but less so among people who inject drugs (7.0%, 95% CI 5.0 to 10.0, I2  = 90.23). Overall, men who have sex with men were more likely to carry any PDR compared to the "general population," a finding which was statistically significant (odds ratio (OR) 1.28, 95% CI 1.13 - 1.46, I2 48.9%).

CONCLUSIONS

High prevalence of PDR found in key populations highlights the need to increase access to effective first-line HIV treatment. The low prevalence of nucleotide reverse transcriptase inhibitor (NRTI) PDR suggests that current WHO recommendations for pre-exposure prophylaxis (PrEP) regimens will remain effective and can be scaled up to prevent new HIV infections in high-risk groups.

Transmitted, pre-treatment and acquired antiretroviral drug resistance among men who have sex with men and transgender women living with HIV in Nigeria

BACKGROUND

Across sub-Saharan Africa, men who have sex with men (MSM) and transgender women (TGW) have disproportionately poor HIV treatment outcomes. Stigma and criminalization create barriers to health-care engagement and adherence to antiretroviral therapy (ART), potentially promoting the development of HIV drug resistance (HIVDR). We evaluated transmitted, pre-treatment and acquired HIVDR among MSM and TGW in Lagos and Abuja, Nigeria.

METHODS

Adults with HIV RNA ≥1,000 copies/ml in the TRUST/RV368 cohort, including incident cases diagnosed via 3-monthly screening, underwent HIVDR testing using the Sanger sequencing method. Major mutations conferring resistance to nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs) were identified from the 2017 IAS-USA list. World Health Organization surveillance drug resistance mutations (SDRMs) were identified in ART-naive participants.

RESULTS

From March 2013 to June 2017, 415 participants with median age 24 (interquartile range [IQR] 21-27) years, CD4⁺ T-cell count 370 (IQR 272-502) cells/mm³, and HIV RNA 4.73 (IQR 4.26-5.15) log₁₀ copies/ml underwent HIVDR testing. SDRMs were observed in 36 of 373 ART-naive participants (9.7%, 95% confidence interval [95% CI 6.8, 13.1%]), including 8 of 39 incident cases (20.5%, [95% CI] 9.3, 36.5%). Among 42 ART-experienced participants, NNRTI resistance was detected in 18 (42.9%, 95% CI 27.7, 59.0%) and NRTI resistance in 10 (23.8%, 95% CI 12.0, 39.4%). No PI resistance was detected.

CONCLUSIONS

The high prevalence of transmitted and acquired drug resistance among Nigerian MSM and TGW living with HIV suggests the need for programmatic solutions to improve uninterrupted access to ART and timely switch to second-line regimens in cases of viral failure.

HIV-1 transmitted drug resistance surveillance: shifting trends in study design and prevalence estimates

INTRODUCTION

HIV-1 transmitted drug resistance (TDR) prevalence increased during the initial years of the antiretroviral therapy (ART) global scale-up. Few studies have examined recent trends in TDR prevalence using published genetic sequences and described the characteristics of ART-naïve persons from whom these published sequences have been obtained.

METHODS

We identified 125 studies published between 2014 and 2019 for which HIV-1 reverse transcriptase (RT) with or without protease from ≥50 ART-naïve adult persons were submitted to the GenBank sequence database. The population characteristics and TDR prevalence were compared to those in 122 studies published in the preceding five years between 2009 and 2013. TDR prevalence was analysed using median study-level and person-level data.

RESULTS AND DISCUSSION

The 2009 to 2013 and 2014 to 2019 studies reported sequence data from 32,866 and 41,724 ART-naïve persons respectively. Studies from the low- and middle-income country (LMIC) regions in sub-Saharan Africa, South/Southeast Asia and Latin America/Caribbean accounted for approximately two-thirds of the studies during each period. Between the two periods, the proportion of studies from sub-Saharan Africa and from South/Southeast Asia countries other than China decreased from 43% to 32% and the proportion of studies performed at sentinel sites for recent HIV-1 infection decreased from 33% to 22%. Between 2014 and 2019, median study-level TDR prevalence was 4.1% in South/Southeast Asia, 6.0% in sub-Saharan Africa, 9.1% in Latin America/Caribbean, 8.5% in Europe and 14.2% in North America. In the person-level analysis, there was an increase in overall, NNRTI and two-class NRTI/NNRTI resistance in sub-Saharan Africa; an increase in NNRTI resistance in Latin America/Caribbean, and an increase in overall, NNRTI and PI resistance in North America.

CONCLUSIONS

Overall, NNRTI and dual NRTI/NNRTI-associated TDR prevalence was significantly higher in sub-Saharan Africa studies published between 2014 and 2019 compared with those published between 2009 and 2013. The decreasing proportion of studies from the hardest hit LMIC regions and the shift away from sentinel sites for recent infection suggests that global TDR surveillance efforts and publication of findings require renewed emphasis.

Sub-attomole detection of HIV-1 using padlock probes and rolling circle amplification combined with microfluidic affinity chromatography

Despite significant progress in diagnostics and disease management during the past decades, human immunodeficiency virus (HIV) infections are still responsible for nearly 1 million deaths every year, mostly in resource-limited settings. Thus, novel, accurate and cost-effective tools for viral load monitoring become crucial to allow specific diagnostics and the effective monitoring of the associated antiviral therapies. Herein, we report an effective combination of a (1) padlock probe (PLP)-mediated rolling circle amplification (RCA) bioassay and an (2) agarose bead-based microfluidic device for the affinity chromatography-based capture and detection of RCA products (RCPs) pre-labelled simultaneously with biotin and an organic fluorophore. This method allowed the efficient capture of ~1 μm-sized RCPs followed by their quantification either as discrete signals or an average fluorescence signal, thus being compatible with both high-resolution imaging for maximum sensitivity as well as simpler optical detection setups. A limit of detection < 30 fM was obtained for HIV-1 synthetic target with just a single round of RCA, comparable to recently reported procedures requiring technically complex amplification strategies such as hyperbranching and/or enzymatic digestion/amplification. Furthermore, targeting a set of five conserved regions in the HIV-1 gag gene, the method could specifically detect HIV-1 in 293T cell culture supernatants, as well as a set of 11 HIV-1 NIH reference samples with four different subtypes. The reported method provides simplicity of operation, unique versatility of signal transduction (i.e. average or discrete signals), and potential coupling with previously reported miniaturized photodetectors. These combined features hold promise for bringing RCA-based molecular diagnostics closer to the point-of-care.

The crosstalk between antiretrovirals pharmacology and HIV drug resistance

INTRODUCTION

The clinical development of antiretroviral drugs has been followed by a rapid and concomitant development of HIV drug resistance. The development and spread of HIV drug resistance is due on the one hand to the within-host intrinsic HIV evolutionary rate and on the other to the wide use of low genetic barrier antiretrovirals.

AREAS COVERED

We searched PubMed and Embase on 31 January 2020, for studies reporting antiretroviral resistance and pharmacology. In this review, we assessed the molecular target and mechanism of drug resistance development of the different antiretroviral classes focusing on the currently approved antiretroviral drugs. Then, we assessed the main pharmacokinetic/pharmacodynamic of the antiretrovirals. Finally, we retraced the history of antiretroviral treatment and its interconnection with antiretroviral worldwide resistance development both in , and middle-income countries in the perspective of 90-90-90 World Health Organization target.

EXPERT OPINION

Drug resistance development is an invariably evolutionary driven phenomenon, which challenge the 90-90-90 target. In high-income countries, the antiretroviral drug resistance seems to be stable since the last decade. On the contrary, multi-intervention strategies comprehensive of broad availability of high genetic barrier regimens should be implemented in resource-limited setting to curb the rise of drug resistance.

A single variant sequencing method for sensitive and quantitative detection of HIV-1 minority variants

HIV drug resistance is a major threat to achieving long-term viral suppression in HIV-positive individuals. Drug resistant HIV variants, including minority variants, can compromise response to antiretroviral therapy. Many studies have investigated the clinical relevance of drug resistant minority variants, but the level at which minority variants become clinically relevant remains unclear. A combination of Primer-ID and deep sequencing is a promising approach that may quantify minority variants more accurately compared to standard deep sequencing. However, most studies that used the Primer-ID method have analyzed clinical samples directly. Thus, its sensitivity and quantitative accuracy have not been adequately validated using known controls. Here, we constructed defined proportions of artificial RNA and virus quasispecies and measured their relative proportions using the Primer-ID based, quantitative single-variant sequencing (qSVS) assay. Our results showed that minority variants present at 1% of quasispecies were detected reproducibly with minimal variations between technical replicates. In addition, the measured frequencies were comparable to the expected frequencies. These data validate the accuracy and reproducibility of the qSVS assay in quantifying authentic HIV minority variants, and support the use of this approach to examine the impacts of minority HIV variants on virologic response and clinical outcome.

HIV drug resistance in a cohort of HIV-infected MSM in the United States

OBJECTIVE

To analyze HIV drug resistance among MSM recruited for participation in the HPTN 078 study, which evaluated methods for achieving and maintaining viral suppression in HIV-infected MSM.

METHODS

Individuals were recruited at four study sites in the United States (Atlanta, Georgia; Baltimore, Maryland; Birmingham, Alabama; and Boston, Massachusetts; 2016-2017). HIV genotyping was performed using samples collected at study screening or enrollment. HIV drug resistance was evaluated using the Stanford v8.7 algorithm. A multiassay algorithm was used to identify individuals with recent HIV infection. Clustering of HIV sequences was evaluated using phylogenetic methods.

RESULTS

High-level HIV drug resistance was detected in 44 (31%) of 142 individuals (Atlanta: 21%, Baltimore: 29%, Birmingham: 53%, Boston: 26%); 12% had multiclass resistance, 16% had resistance to tenofovir or emtricitabine, and 8% had resistance to integrase strand transfer inhibitors (INSTIs); 3% had intermediate-level resistance to second-generation INSTIs. In a multivariate model, self-report of ever having been on antiretroviral therapy (ART) was associated with resistance (P = 0.005). One of six recently infected individuals had drug resistance. Phylogenetic analysis identified five clusters of study sequences; two clusters had shared resistance mutations.

CONCLUSION

High prevalence of drug resistance was observed among MSM. Some had multiclass resistance, resistance to drugs used for preexposure prophylaxis (PrEP), and INSTI resistance. These findings highlight the need for improved HIV care in this high-risk population, identification of alternative regimens for PrEP, and inclusion of integrase resistance testing when selecting ART regimens for MSM in the United States.

Trend of HIV transmitted drug resistance before and after implementation of HAART regimen restriction in the treatment of HIV-1 infected patients in southern Taiwan

Background

The use of fixed combination antiretroviral therapy with a low genetic barrier for the treatment of patients infected with human immunodeficiency virus (HIV) may affect the local HIV transmitted drug resistance (TDR) pattern. The present study aimed to investigate changes in the prevalence of HIV TDR following the implementation of a fixed regimen of HIV treatment in Taiwan in 2012.

Methods

TDR was measured in antiretroviral treatment-naïve HIV-1-infected individuals who participated in voluntary counseling and testing between 2007 and 2015 in southern Taiwan. Antiretroviral resistance mutations were interpreted using the HIVdb program from the Stanford University HIV Drug Resistance Database.

Results

Sequences were obtained from 377 consecutive individuals between 2007 and 2015. The overall prevalence rates of TDR HIV among the study population from 2007 to 2011 and 2012–2015 were 10.6 and 7.9%, respectively. Among the detected mutations, K103 N and V179D + K103R were more frequently observed after 2012. Four HIV-infected patients with K103 N variants were detected after 2012, and 4 of the 5 patients with V179D + K103R variants were found after 2012. No significant differences were observed in the TDRs among nucleoside reverse transcriptase inhibitors (NRTIs), non-NRTIs (NNRTIs), protease inhibitors, multiple drug resistance, and any drug resistance between period 1 (2007–2011) and period 2 (2012–2015).

Conclusions

A fixed treatment regimen with zidovudine/lamivudine + efavirenz or nevirapine as first-line therapy for treatment-naïve patients infected with HIV did not significantly increase the TDR during the 4-year follow-up period. Due to the increase in NNRTI resistance associated with mutations after 2012, a longer follow-up period and larger sample size are needed in future studies.

Analysis of transmitted HIV drug resistance from 2005 to 2015 in Victoria, Australia: a comparison of the old and the new

Background Baseline genotyping is part of standard-of-care treatment. It reveals that transmitted drug resistance (TDR) continues to be important for the management of HIV infection. Attention is typically focused on determining whether resistance to the protease inhibitors (PI) and reverse transcriptase inhibitors (RTI) occurs. However, the increasing use of integrase inhibitors (INIs) raises a concern that TDR to this class of antiretroviral drug may also occur.

METHODS

PI and RTI drug resistance genotyping was performed on blood samples collected between 2005 and 2015 from 772 treatment-naïve Victorian patients infected with HIV within the previous 12 months. Integrase genotyping was performed on 461 of the 485 patient samples collected between 2010 and 2015.

RESULTS

In the period 2005-10, 39 of 343 patients (11.4%) had at least one PI- or RTI-associated mutation, compared with 34 of 429 (7.9%) during the period 2011-15. Compared with 2005-10, during 2011-15 there was a significant decline in the prevalence of the non-nucleoside-associated mutation K103N and the nucleoside-associated mutations at codons M41 and T215. One patient was detected with a major INI resistance mutation, namely G118R. However, this mutation is rare and its effect on susceptibility is unclear. A small number of patients (n=12) was infected with HIV containing accessory resistance mutations in the integrase gene.

CONCLUSIONS

The lack of transmitted resistance to INIs is consistent with a low level of resistance to this class of drugs in the treated population. However, continued surveillance in the newly infected population is warranted as the use of INIs increases.

Resistance Analysis of Bictegravir-Emtricitabine-Tenofovir Alafenamide in HIV-1 Treatment-Naive Patients through 48 Weeks

In clinical studies GS-US-380-1489 (study 1489) and GS-US-380-1490 (study 1490), bictegravir-emtricitabine-tenofovir alafenamide (B-F-TAF), dolutegravir-abacavir-lamivudine (DTG-ABC-3TC), and dolutegravir plus emtricitabine-tenofovir alafenamide (DTG+F-TAF) treatment achieved high rates of virologic suppression in HIV-1 treatment-naive participants through week 48. Preexisting primary drug resistance was present at levels of 1.3% integrase strand transfer inhibitor resistance (INSTI-R), 2.7% nucleoside reverse transcriptase inhibitor resistance (NRTI-R), 14.1% nonnucleoside reverse transcriptase inhibitor resistance (NNRTI-R), and 3.5% protease inhibitor resistance (PI-R) in the 1,274 participants from these studies. These mutations did not affect treatment outcomes. Resistance analyses in 13 virologic failures found no emergent resistance to study drugs.

Presence, persistence and effects of pre-treatment HIV-1 drug resistance variants detected using next generation sequencing: A Retrospective longitudinal study from rural coastal Kenya

BACKGROUND

The epidemiology of HIV-1 drug resistance (HIVDR) determined by Sanger capillary sequencing, has been widely studied. However, much less is known about HIVDR detected using next generation sequencing (NGS) methods. We aimed to determine the presence, persistence and effect of pre-treatment HIVDR variants detected using NGS in HIV-1 infected antiretroviral treatment (ART) naïve participants from rural Coastal Kenya.

METHODS

In a retrospective longitudinal study, samples from HIV-1 infected participants collected prior [n = 2 time-points] and after [n = 1 time-point] ART initiation were considered. An ultra-deep amplicon-based NGS assay, calling for nucleotide variants at >2.0% frequency of viral population, was used. Suspected virologic failure (sVF) was defined as a one-off HIV-1 viral load of >1000 copies/ml whilst on ART.

RESULTS

Of the 50 eligible participants, 12 (24.0% [95% CI: 13.1-38.2]) had at least one detectable pre-treatment HIVDR variant against Protease Inhibitors (PIs, n = 6 [12%]), Nucleoside Reverse Transcriptase Inhibitors (NRTIs, n = 4 [8.0%]) and Non-NRTIs (n = 3 [6.0%]). Overall, 15 pre-treatment resistance variants were detected (frequency, range: 2.3-92.0%). A positive correlation was observed between mutation frequency and absolute load for NRTI and/or NNRTI variants (r = 0.761 [p = 0.028]), but not for PI variants (r = -0.117 [p = 0.803]). Participants with pre-treatment NRTI and/or NNRTI resistance had increased odds of sVF (OR = 6.0; 95% CI = 1.0-36.9; p = 0.054).

CONCLUSIONS

Using NGS, pre-treatment resistance variants were common, though observed PI variants were unlikely transmitted, but rather probably generated de novo. Even when detected from a low frequency, pre-treatment NRTI and/or NNRTI resistance variants may adversely affect treatment outcomes.

A competitive ELISA for the quantitative determination of the novel anti-HIV drug candidate CIGB-210 in biological fluids

The synthetic peptide CIGB-210 is a promising anti-HIV drug candidate shown to inhibit HIV replication in MT4 cells at the nanomolar range by triggering the rearrangement of vimentin intermediate filaments. Sensitive and specific analytical methods are required for pharmacological studies of CIBG-210 in animals. In this study, we describe the development of a competitive ELISA for the quantitative determination of CIGB-210 using an anti-CIGB-210 hyperimmune serum. After optimization of all the steps, the assay exhibited a dynamic range from 11.87 to 0.0095 µg/mL. The intra-assay coefficient of variation (CV) was lower than or close to 5% for all the six concentrations of the calibrator, and the inter-assay CV was below 10% in five out of the six concentrations tested. No interference of either murine or human plasma was observed. The analyte was stable in plasma after five freeze-thaw cycles, while the hyperimmune serum maintained its binding capacity after 10 freeze-thaw cycles. Furthermore, the ELISA was able to detect the two main metabolites of CIGB-210, although with a tenfold decrease in sensitivity. Our results demonstrate the utility and feasibility of this analytical method for pharmacological experiments in animals as humans.

Antiretroviral resistance testing in HIV-positive people

BACKGROUND

Resistance to antiretroviral therapy (ART) among people living with human immunodeficiency virus (HIV) compromises treatment effectiveness, often leading to virological failure and mortality. Antiretroviral drug resistance tests may be used at the time of initiation of therapy, or when treatment failure occurs, to inform the choice of ART regimen. Resistance tests (genotypic or phenotypic) are widely used in high-income countries, but not in resource-limited settings. This systematic review summarizes the relative merits of resistance testing in treatment-naive and treatment-exposed people living with HIV.

OBJECTIVES

To evaluate the effectiveness of antiretroviral resistance testing (genotypic or phenotypic) in reducing mortality and morbidity in HIV-positive people.

SEARCH METHODS

We attempted to identify all relevant studies, regardless of language or publication status, through searches of electronic databases and conference proceedings up to 26 January 2018. We searched MEDLINE, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), in the Cochrane Library, the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), and ClinicalTrials.gov to 26 January 2018. We searched Latin American and Caribbean Health Sciences Literature (LILACS) and the Web of Science for publications from 1996 to 26 January 2018.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs) and observational studies that compared resistance testing to no resistance testing in people with HIV irrespective of their exposure to ART.Primary outcomes of interest were mortality and virological failure. Secondary outcomes were change in mean CD4-T-lymphocyte count, clinical progression to AIDS, development of a second or new opportunistic infection, change in viral load, and quality of life.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed each reference for prespecified inclusion criteria. Two review authors then independently extracted data from each included study using a standardized data extraction form. We analysed data on an intention-to-treat basis using a random-effects model. We performed subgroup analyses for the type of resistance test used (phenotypic or genotypic), use of expert advice to interpret resistance tests, and age (children and adolescents versus adults). We followed standard Cochrane methodological procedures.

MAIN RESULTS

Eleven RCTs (published between 1999 and 2006), which included 2531 participants, met our inclusion criteria. All of these trials exclusively enrolled patients who had previous exposure to ART. We found no observational studies. Length of follow-up time, study settings, and types of resistance testing varied greatly. Follow-up ranged from 12 to 150 weeks. All studies were conducted in Europe, USA, or South America. Seven studies used genotypic testing, two used phenotypic testing, and two used both phenotypic and genotypic testing. Only one study was funded by a manufacturer of resistance tests.Resistance testing made little or no difference in mortality (odds ratio (OR) 0.89, 95% confidence interval (CI) 0.36 to 2.22; 5 trials, 1140 participants; moderate-certainty evidence), and may have slightly reduced the number of people with virological failure (OR 0.70, 95% CI 0.56 to 0.87; 10 trials, 1728 participants; low-certainty evidence); and probably made little or no difference in change in CD4 cell count (mean difference (MD) -1.00 cells/mm³, 95% CI -12.49 to 10.50; 7 trials, 1349 participants; moderate-certainty evidence) or progression to AIDS (OR 0.64, 95% CI 0.31 to 1.29; 3 trials, 809 participants; moderate-certainty evidence). Resistance testing made little or no difference in adverse events (OR 0.89, 95% CI 0.51 to 1.55; 4 trials, 808 participants; low-certainty evidence) and probably reduced viral load (MD -0.23, 95% CI -0.35 to -0.11; 10 trials, 1837 participants; moderate-certainty evidence). No studies reported on development of new opportunistic infections or quality of life. We found no statistically significant heterogeneity for any outcomes, and the I² statistic value ranged from 0 to 25%. We found no subgroup effects for types of resistance testing (genotypic versus phenotypic), the addition of expert advice to interpretation of resistance tests, or age. Results for mortality were consistent when we compared studies at high or unclear risk of bias versus studies at low risk of bias.

AUTHORS' CONCLUSIONS

Resistance testing probably improved virological outcomes in people who have had virological failure in trials conducted 12 or more years ago. We found no evidence in treatment-naive people. Resistance testing did not demonstrate important patient benefits in terms of risk of death or progression to AIDS. The trials included very few participants from low- and middle-income countries.

HIV-1 subtype diversity, transmitted drug resistance and phylogenetics in Australia

Australia has maintained a low prevalence of HIV, with a mainly concentrated epidemic and successful public health response. With the widespread availability of HIV genotyping for resistance testing, and development of phylogenetic methodologies, the field of molecular epidemiology has evolved a deeper understanding of diversity and transmission dynamics of HIV. Studies combining HIV genotype with epidemiological data have allowed insights to be gained into the changing subtype diversity, rates of transmitted drug resistance and transmission networks of HIV in Australia. This review provides an overview of HIV molecular epidemiology studies in Australia.

Prevalence and Transmission Dynamics of HIV-1 Transmitted Drug Resistance in a Southeastern Cohort

Background

Transmitted drug resistance (TDR) compromises clinical management and outcomes. Transmitted drug resistance surveillance and identification of growing transmission clusters are needed in the Southeast, the epicenter of the US HIV epidemic. Our study investigated prevalence and transmission dynamics in North Carolina.

Methods

We analyzed surveillance drug resistance mutations (SDRMs) using partial pol sequences from patients presenting to 2 large HIV outpatient clinics from 1997 to 2014. Transmitted drug resistance prevalence was defined as ≥1 SDRMs among antiretroviral therapy (ART)–naïve patients. Binomial regression was used to characterize prevalence by calendar year, drug class, and demographic and clinical factors. We assessed the transmission networks of patients with TDR with maximum likelihood trees and Bayesian methods including background pol sequences (n = 15 246).

Results

Among 1658 patients with pretherapy resistance testing, ≥1 SDRMs was identified in 199 patients, with an aggregate TDR prevalence of 12% (95% confidence interval, 10% to 14%) increasing over time (P = .02). Resistance to non-nucleoside reverse transcriptase inhibitors (NNRTIs; 8%) was common, followed by nucleoside reverse transcriptase inhibitors (4%) and protease inhibitors (2%). Factors associated with TDR were being a man reporting sex with men, white race, young age, higher CD4 cell count, and being a member of a transmission cluster. Transmitted drug resistance was identified in 106 clusters ranging from 2 to 26 members. Cluster resistance was primarily NNRTI and dominated by ART-naïve patients or those with unknown ART initiation.

Conclusions

Moderate TDR prevalence persists in North Carolina, predominantly driven by NNRTI resistance. Most TDR cases were identified in transmission clusters, signifying multiple local transmission networks and TDR circulation among ART-naïve persons. Transmitted drug resistance surveillance can detect transmission networks and identify patients for enhanced services to promote early treatment.

RNA and DNA Sanger sequencing versus next-generation sequencing for HIV-1 drug resistance testing in treatment-naive patients

Background

Sanger sequencing of plasma RNA is the standard method for HIV-1 drug resistance testing in treatment-naive patients, but is limited by the non-detection of resistance-associated mutations (RAMs) with prevalence below approximately 20%.

Objectives

We compared RNA and DNA Sanger sequencing (RSS and DSS) with RNA next-generation sequencing (NGS) for RAM detection in HIV-1 reverse transcriptase (RT), protease (PR) and integrase (IN) genes.

Methods

Sanger sequencing was performed on RNA and DNA, following the recommendations of the French Agency for AIDS Research (ANRS). NGS was performed on RNA using the HIV-1 Drug Resistance Assay, v. 3.0 (Roche) on the 454 GS Junior sequencer. The IAS-USA list was used to identify RAMs. ANRS, Rega and Stanford algorithms were used for drug resistance interpretation.

Results

The study included 48 ART-naive patients. The number of patients with at least one major RAM was 3, 3, 4 and 8 when using RSS, DSS, NGS 20% and NGS 5%, respectively. Numerous minor mutations were detected in patients, especially in the protease gene. None of the methods detected any major mutation in the integrase gene. Overall, the mutation detection rate was similar between RSS and DSS, and higher with NGS 20%. Differences in drug resistance interpretation were found between algorithms. No impact of the minority RAMs detected by NGS was found on the short-term treatment outcome.

Conclusions

DSS does not clearly improve the detection of RAMs in ART-naive patients, as compared with RSS. NGS allows detection of additional minority RAMs; however, their clinical relevance requires further investigation.

Patterns of Transmitted Drug Resistance and Virological Response to First-line Antiretroviral Treatment Among Human Immunodeficiency Virus-Infected People Who Use Illicit Drugs in a Canadian Setting

Background

Transmitted drug resistance (TDR) may compromise response to antiretroviral therapy (ART). However, there are limited data on TDR patterns and impacts among people who use illicit drugs (PWUD).

Methods

Data were drawn from 2 prospective cohorts of PWUD in Vancouver, Canada. We characterized patterns of TDR among human immunodeficiency virus (HIV)-infected PWUD, and assessed its impacts on first-line ART virological outcomes.

Results

Between 1996 and 2015, among 573 ART-naive PWUD (18% with recent HIV infection), the overall TDR prevalence was 9.8% (95% confidence interval [CI], 7.3%-12.2%), with an increasing trend over time, from 8.5% in 1996-1999 to 21.1% in 2010-2015 (P = .003), mainly driven by resistance to nonnucleoside reverse transcriptase inhibitors (NNRTIs). TDR-associated mutations were more common for NNRTIs (5.4%), followed by nucleoside reverse transcriptase inhibitors (3.0%) and protease inhibitors (1.9%). TDR prevalence was lower among recently infected PWUD (adjusted odds ratio, 0.39 [95% CI, .15-.87]). Participants with TDR had higher risk of virological failure than those without TDR (log-rank P = .037) in the first year of ART.

Conclusions

Between 1996 and 2015, TDR prevalence increased significantly among PWUD in Vancouver. Higher risk of virological failure among PWUD with TDR may be explained by some inappropriate ART prescribing, as well as undetected minority resistant variants in participants with chronic HIV infection. Our findings support baseline resistance testing early in the course of HIV infection to guide ART selection among PWUD in our setting.

The global burden of HIV-1 drug resistance in the past 20 years

Genotypic drug resistance testing has been an integral part of the clinical management of HIV patients for almost 20 years, not only assisting treatment choices but also informing drug development. Accurate estimations on the worldwide circulation of drug resistance are difficult to obtain, particularly in low/middle-income countries. In this work, we queried two of the largest public HIV sequence repositories in the world—Los Alamos and Stanford HIVdb—to derive global prevalence, time trends and geodemographic predictors of HIV drug resistance. Different genotypic interpretation systems were used to ascertain resistance to reverse transcriptase and protease inhibitors. Continental, subtype-specific (including circulating recombinant forms) stratification as well as analysis on drug-naïve isolates were performed. Geographic information system analysis correlated country-specific drug resistance to sociodemographic and health indicators obtained from the World Bank. By looking at over 33,000 sequences worldwide between 1996 and 2016, increasing drug resistance trends with non-B subtypes and recombinants were found; transmitted drug resistance appeared to remain stable in the last decade. While an increase in drug resistance is expected with antiretroviral therapy rollout in resource-constrained areas, the plateau effect in areas covered by the most modern drug regimens warns against the downgrading of the resistance issue.

High prevalence of HIV-1 transmitted drug resistance among therapy-naïve Burmese entering travelers at Dehong ports in Yunnan, China

BACKGROUND

The overall success of Human immunodeficiency virus type 1 (HIV-1) antiretroviral therapy (ART) was heavily challenged upon the occurrence of drug resistance. Dehong Prefecture witnessed not only the first report of HIV-1 infection but also the experimental adoption of antiviral treatment in China. The transmission and epidemic of HIV-1 in Dehong is impacted by cross-border activities. The characteristics of HIV-1 drug resistance among therapy-naïve Burmese entering travelers in Yunnan and their speculated origin are still not clarified.

METHODS

Two hundred ninety-eight HIV-1 infected Burmese entering travelers at Dehong ports were recruited between 2003 and 2012. The partial HIV-1 pol gene fragments were amplified and sequenced for the analysis of drug-resistance mutations (DRMs). Phylogenetic analysis on gag-pol gene was conducted to elucidate phylogenetic and evolutionary characteristics of these drug resistant strains.

RESULTS

It was figured out that the occurrence ratio of HIV-1 drug resistance among HIV-1 infected entering travelers from Myanmar was up to 12.8%. The resistant mutations covered several types, including one type of PI mutations (L33F), six types of NRTI mutations and seven types of NNRTI. Close genetic relationship was observed in the phylogenetic analysis on gag-pol gene among the drug resistant strains respectively from Dehong, other Yunnan areas, neighboring provinces (Guangxi) and neighboring countries (Thailand and Myanmar).

CONCLUSIONS

The findings in this study revealed that HIV drug resistant locus is spreading from the population who is receiving drug-resistance treatment to the new infectors, which indicates the urgency of surveillance work on drug resistance among the migrant population with high risks of HIV infection.

HIV-1 transmitted drug resistance in Slovenia and its impact on predicted treatment effectiveness: 2011-2016 update

HIV-positive individuals that have a detected transmitted drug resistance (TDR) at baseline have a higher risk of virological failure with antiretroviral therapy (ART). This study offers an update on the prevalence of TDR in Slovenia, looks for onward transmission of TDR, and reassesses the need for baseline drug resistance testing. Blinded questionnaires and partial pol sequences were obtained from 54.5% (168/308) of all of the patients diagnosed with HIV-1 from 2011 to 2016. Subtype B was detected in 82.7% (139/168) of patients, followed by subtype A (8.3%), subtype C (2.4%), and CRF01_AE (1.8%). Surveillance drug resistance mutations (SDRMs) were found in four individuals (2.4%), all of them men who have sex with men (MSM) and infected with subtype B. K103N was detected in two patients and T68D and T215D in one person each, corresponding to a prevalence of 0%, 1.2%, and 1.2% of TDR to protease inhibitors (PIs), nucleoside reverse transcriptase inhibitors (NRTIs), and non-NRTIs (NNRTIs), respectively. The impact of mutations on drug susceptibility was found to be most pronounced for NNRTIs. No forward spread of TDR within the country was observed; however, phylogenetic analysis revealed several new introductions of HIV into Slovenia in recent years, possibly due to increased risky behavior by MSM. This was indirectly confirmed by a substantial increase in syphilis cases and HIV-1 non-B subtypes during the study period. A drug-resistant HIV variant with good transmission fitness is thus more likely to be imported into Slovenia in the near future, and so TDR should be closely monitored.

Key issues review: evolution on rugged adaptive landscapes

Adaptive landscapes represent a mapping between genotype and fitness. Rugged adaptive landscapes contain two or more adaptive peaks: allele combinations with higher fitness than any of their neighbors in the genetic space. How do populations evolve on such rugged landscapes? Evolutionary biologists have struggled with this question since it was first introduced in the 1930s by Sewall Wright. Discoveries in the fields of genetics and biochemistry inspired various mathematical models of adaptive landscapes. The development of landscape models led to numerous theoretical studies analyzing evolution on rugged landscapes under different biological conditions. The large body of theoretical work suggests that adaptive landscapes are major determinants of the progress and outcome of evolutionary processes. Recent technological advances in molecular biology and microbiology allow experimenters to measure adaptive values of large sets of allele combinations and construct empirical adaptive landscapes for the first time. Such empirical landscapes have already been generated in bacteria, yeast, viruses, and fungi, and are contributing to new insights about evolution on adaptive landscapes. In this Key Issues Review we will: (i) introduce the concept of adaptive landscapes; (ii) review the major theoretical studies of evolution on rugged landscapes; (iii) review some of the recently obtained empirical adaptive landscapes; (iv) discuss recent mathematical and statistical analyses motivated by empirical adaptive landscapes, as well as provide the reader with instructions and source code to implement simulations of evolution on adaptive landscapes; and (v) discuss possible future directions for this exciting field.

Drug resistance in B and non-B subtypes amongst subjects recently diagnosed as primary/recent or chronic HIV-infected over the period 2013-2016: Impact on susceptibility to first-line strategies including integrase strand-transfer inhibitors

OBJECTIVES

To characterize the prevalence of transmitted drug resistance mutations (TDRMs) by plasma analysis of 750 patients at the time of HIV diagnosis from January 1, 2013 to November 16, 2016 in the Veneto region (Italy), where all drugs included in the recommended first line therapies were prescribed, included integrase strand transfer inhibitors (InNSTI).

METHODS

TDRMs were defined according to the Stanford HIV database algorithm.

RESULTS

Subtype B was the most prevalent HIV clade (67.3%). A total of 92 patients (12.3%) were expected to be resistant to one drug at least, most with a single class mutation (60/68-88.2% in subtype B infected subjectsand 23/24-95.8% in non-B subjects) and affecting mainly NNRTIs. No significant differences were observed between the prevalence rates of TDRMs involving one or more drugs, except for the presence of E138A quite only in patients with B subtype and other NNRTI in subjects with non-B infection. The diagnosis of primary/recent infection was made in 73 patients (9.7%): they had almost only TDRMs involving a single class. Resistance to InSTI was studied in 484 subjects (53 with primary-recent infection), one patient had 143C in 2016, a total of thirteen 157Q mutations were detected (only one in primary/recent infection).

CONCLUSIONS

Only one major InSTI-TDRM was identified but monitoring of TDRMs should continue in the light of continuing presence of NNRTI-related mutation amongst newly diagnosed subjects, sometime impacting also to modern NNRTI drugs recommended in first-line therapy.

Decreasing prevalence of transmitted drug resistance among ART-naive HIV-1-infected patients in Iceland, 1996-2012

Introduction: Resistance to antiretroviral drugs can complicate the management of HIV-1 infection and impair control of its spread. The aim of the current study was to investigate the prevalence and transmission of HIV-1 drug resistance among 106 antiretroviral therapy (ART)-naïve patients diagnosed in Iceland (1996-2012). Methods: HIV-1 polymerase sequences were analysed using the Calibrated Population Resistance tool. Domestic spread of transmitted drug resistance (TDR) was investigated through maximum likelihood and Bayesian approaches. Results: Among ART-naïve patients, the prevalence of TDR to any of the following classes (NRTIs, NNRTIs and PIs) was 8.5% (95% CI: 4.5%- 15.4%): 6.6% to NRTIs, 0.9% to NNRTIs, and 1.9% to PIs. The most frequent NRTI mutation detected was T215C/D (n=7, 5.7%). The only NNRTI mutation detected was K103N (n=1, 0.9%). PI mutations detected were M46I (n=1, 0.9%) and L90M (n=1, 0.9%). Six patients harbouring T215C/D, were linked in a supported phylogenetic cluster. No significant association was found between TDR and demographic or risk groups. Trend analysis showed a decrease in the prevalence of TDR (1996-2012, p=0.003). Conclusions: TDR prevalence in Iceland was at a moderate level and decreased during 1996-2012. Screening for TDR is recommended to limit its local spread and to optimize HIV-1 therapy. Abbreviations: ART: Anti-retroviral therapy; ARV: antiretroviral; ATV/r: atazanavir/ritonavir; AZT: azidothymidine; BEAST: Bayesian evolutionary analysis by sampling trees; CI: confidence interval; CPR: calibrated population resistance; CRF: circulating recombinant form; d4T: stavudine; EFV: efavirenz; FET: Fishers' exact test; FPV/r: fosamprenavir/ritonavir; HET: heterosexual; IDU: injection drug use; IDV/r: indinavir/ritonavir; LPV/r: lopinavir/ritonavir; MSM: men who have sex with men; M-W: Mann-Whitney U test; NFV: nelfinavir; NNRTIs: non-nucleoside reverse transcriptase inhibitors; NRTIs: nucleoside reverse transcriptase inhibitors; NVP: nevirapine; PIs: protease inhibitors; pol: polymerase gene; SDRM: surveillance drug resistance mutation; SQV/r: saquinavir/ritonavir; TDR: transmitted drug resistance.

Prevalence of Transmitted Drug-Resistance Mutations and Polymorphisms in HIV-1 Reverse Transcriptase, Protease, and gp41 Sequences Among Recent Seroconverters in Southern Poland

Background

Monitoring of drug resistance-related mutations among patients with recent HIV-1 infection offers an opportunity to describe current patterns of transmitted drug resistance (TDR) mutations.

Material/Methods

Of 298 individuals newly diagnosed from March 2008 to February 2014 in southern Poland, 47 were deemed to have recent HIV-1 infection by the limiting antigen avidity immunoassay. Proviral DNA was amplified and sequenced in the reverse transcriptase, protease, and gp41 coding regions. Mutations were interpreted according to the Stanford Database algorithm and/or the International Antiviral Society USA guidelines. TDR mutations were defined according to the WHO surveillance list.

Results

Among 47 patients with recent HIV-1 infection only 1 (2%) had evidence of TDR mutation. No major resistance mutations were found, but the frequency of strains with ≥1 accessory resistance-associated mutations was high, at 98%. Accessory mutations were present in 11% of reverse transcriptase, 96% of protease, and 27% of gp41 sequences. Mean number of accessory resistance mutations in the reverse transcriptase and protease sequences was higher in viruses with no compensatory mutations in the gp41 HR2 domain than in strains with such mutations (p=0.031).

Conclusions

Despite the low prevalence of strains with TDR mutations, the frequency of accessory mutations was considerable, which may reflect the history of drug pressure among transmitters or natural viral genetic diversity, and may be relevant for future clinical outcomes. The accumulation of the accessory resistance mutations within the pol gene may restrict the occurrence of compensatory mutations related to enfuvirtide resistance or vice versa.