Transmission of HIV drug resistance: lessons from sensitive screening assays

HIV DNA Sequencing to Detect Archived Antiretroviral Drug Resistance

INTRODUCTION

Proviral HIV DNA integrated within CD4 T-cells maintains an archive of viral variants that replicate during the course of the infection, including variants with reduced drug susceptibility. We considered studies that investigated archived drug resistance, with a focus on virologically suppressed patients and highlighted interpretative caveats and gaps in knowledge.

RESULTS

Either Sanger or deep sequencing can be used to investigate resistance-associated mutations (RAMs) in HIV DNA recovered from peripheral blood. Neither technique is free of limitations. Furthermore, evidence regarding the establishment, maintenance, expression and clinical significance of archived drug-resistant variants is conflicting. This in part reflects the complexity of the HIV proviral landscape and its dynamics during therapy. Clinically, detection of RAMs in cellular HIV DNA has a variable impact on treatment outcomes, modulated by the drugs affected, treatment duration and additional determinants of virological failure, including those leading to suboptimal drug exposure.

CONCLUSIONS

Sequencing cellular HIV DNA can provide helpful complementary information in treatment-experienced patients with suppressed plasma HIV RNA who require a change of regimen. However, care should be taken when interpreting the results. Presence of RAMs is not necessarily a barrier to treatment success. Conversely, even the most sensitive sequencing techniques will fail to provide a comprehensive view of the HIV DNA archive. To inform treatment decisions appropriately, the overall clinical and treatment history of a patient must always be considered alongside the results of resistance testing. Prospective controlled studies are needed to validate the utility of drug resistance testing using cellular HIV DNA.

Exploiting genomics to mitigate the public health impact of antimicrobial resistance

Antimicrobial resistance (AMR) is a major global public health threat, which has been largely driven by the excessive use of antimicrobials. Control measures are urgently needed to slow the trajectory of AMR but are hampered by an incomplete understanding of the interplay between pathogens, AMR encoding genes, and mobile genetic elements at a microbial level. These factors, combined with the human, animal, and environmental interactions that underlie AMR dissemination at a population level, make for a highly complex landscape. Whole-genome sequencing (WGS) and, more recently, metagenomic analyses have greatly enhanced our understanding of these processes, and these approaches are informing mitigation strategies for how we better understand and control AMR. This review explores how WGS techniques have advanced global, national, and local AMR surveillance, and how this improved understanding is being applied to inform solutions, such as novel diagnostic methods that allow antimicrobial use to be optimised and vaccination strategies for better controlling AMR. We highlight some future opportunities for AMR control informed by genomic sequencing, along with the remaining challenges that must be overcome to fully realise the potential of WGS approaches for international AMR control.

Surveillance of HIV-1 transmitted integrase strand transfer inhibitor resistance in the UK

Background

HIV treatment guidelines have traditionally recommended that all HIV-positive individuals are tested for evidence of drug resistance prior to starting ART. Testing for resistance to reverse transcriptase inhibitors and PIs is well established in routine care. However, testing for integrase strand transfer inhibitor (InSTI) resistance is less consistent.

Objectives

To inform treatment guidelines by determining the prevalence of InSTI resistance in a national cohort of recently infected individuals.

Patients and methods

Recent (within 4 months) HIV-1 infections were identified using a Recent Infection Testing Algorithm of new HIV-1 diagnoses in the UK. Resistance-associated mutations (RAMs) in integrase, protease and reverse transcriptase were detected by ultradeep sequencing, which allows for the sensitive estimation of the frequency of each resistant variant in a sample.

Results

The analysis included 655 randomly selected individuals (median age = 33 years, 95% male, 83% MSM, 78% white) sampled in the period 2014 to 2016 and determined to have a recent infection. These comprised 320, 138 and 197 samples from 2014, 2015 and 2016, respectively. None of the samples had major InSTI RAMs occurring at high variant frequency (≥20%). A subset (25/640, 3.9%) had major InSTI RAMs occurring only as low-frequency variants (2%–20%). In contrast, 47/588 (8.0%) had major reverse transcriptase inhibitor and PI RAMs at high frequency.

Conclusions

Between 2014 and 2016, major InSTI RAMs were uncommon in adults with recent HIV-1 infection, only occurring as low-frequency variants of doubtful clinical significance. Continued surveillance of newly diagnosed patients for evidence of transmitted InSTI resistance is recommended to inform clinical practice.

Virological outcomes of boosted protease inhibitor-based first-line ART in subjects harbouring thymidine analogue-associated mutations as the sole form of transmitted drug resistance

Objectives

In subjects with transmitted thymidine analogue mutations (TAMs), boosted PIs (PI/b) are often chosen to overcome possible resistance to the NRTI backbone. However, data to guide treatment selection are limited. Our aim was to obtain firmer guidance for clinical practice using real-world cohort data.

Methods

We analysed 1710 subjects who started a PI/b in combination with tenofovir or abacavir plus emtricitabine or lamivudine, and compared their virological outcomes with those of 4889 patients who started an NNRTI (predominantly efavirenz), according to the presence of ≥1 TAM as the sole form of transmitted drug resistance.

Results

Participants with ≥1 TAM comprised predominantly MSM (213 of 269, 79.2%), subjects of white ethnicity (206 of 269, 76.6%) and HIV-1 subtype B infections (234 of 269, 87.0%). Most (203 of 269, 75.5%) had singleton TAMs, commonly a revertant of T215Y or T215F (112 of 269, 41.6%). Over a median of 2.5 years of follow-up, 834 of 6599 (12.6%) subjects experienced viraemia (HIV-1 RNA >50 copies/mL). The adjusted HR for viraemia was 2.17 with PI/b versus NNRTI-based therapy (95% CI 1.88–2.51; P < 0.001). Other independent predictors of viraemia included injecting drug use, black ethnicity, higher viral load and lower CD4 cell count at baseline, and receiving abacavir instead of tenofovir. Resistance showed no overall impact (adjusted HR 0.77 with ≥1 TAM versus no resistance; 95% CI 0.54–1.10; P = 0.15).

Conclusions

In this cohort, patients harbouring ≥1 TAM as the sole form of transmitted drug resistance gained no apparent virological advantage from starting first-line ART with a PI/b.

Drug resistance outcomes of long-term ART with tenofovir disoproxil fumarate in the absence of virological monitoring

Objectives

The resistance profiles of patients receiving long-term ART in sub-Saharan Africa have been poorly described. This study obtained a sensitive assessment of the resistance patterns associated with long-term tenofovir-based ART in a programmatic setting where virological monitoring is yet to become part of routine care.

Methods

We studied subjects who, after a median of 4.2 years of ART, replaced zidovudine or stavudine with tenofovir disoproxil fumarate while continuing lamivudine and an NNRTI. Using deep sequencing, resistance-associated mutations (RAMs) were detected in stored samples collected at tenofovir introduction (T0) and after a median of 4.0 years (T1).

Results

At T0, 19/87 (21.8%) subjects showed a detectable viral load and 8/87 (9.2%) had one or more major NNRTI RAMs, whereas 82/87 (94.3%) retained full tenofovir susceptibility. At T1, 79/87 (90.8%) subjects remained on NNRTI-based ART, 5/87 (5.7%) had introduced lopinavir/ritonavir due to immunological failure, and 3/87 (3.4%) had interrupted ART. Whilst 68/87 (78.2%) subjects maintained or achieved virological suppression between T0 and T1, a detectable viral load with NNRTI RAMs at T0 predicted lack of virological suppression at T1. Each treatment interruption, usually reflecting unavailability of the dispensary, doubled the risk of T1 viraemia. Tenofovir, lamivudine and efavirenz selected for K65R, K70E/T, L74I/V and Y115F, alongside M184V and multiple NNRTI RAMs; this resistance profile was accompanied by high viral loads and low CD4 cell counts.

Conclusions

Viraemia on tenofovir, lamivudine and efavirenz led to complex resistance patterns with implications for continued drug activity and risk of onward transmission.

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.

Enhanced surveillance of HIV-1 drug resistance in recently infected MSM in the UK

OBJECTIVES

To determine the prevalence of inferred low-frequency HIV-1 transmitted drug resistance (TDR) in MSM in the UK and its predicted effect on first-line therapy.

METHODS

The HIV-1 pol gene was amplified from 442 newly diagnosed MSM identified as likely recently infected by serological avidity testing in 2011-13. The PCR products were sequenced by next-generation sequencing with a mutation frequency threshold of >2% and TDR mutations defined according to the 2009 WHO surveillance drug resistance mutations list.

RESULTS

The majority (75.6%) were infected with subtype B and 6.6% with rare complex or unique recombinant forms. At a mutation frequency threshold of >20%, 7.2% (95% CI 5.0%-10.1%) of the sequences had TDR and this doubled to 15.8% (95% CI 12.6%-19.6%) at >2% mutation frequency (P < 0.0001). The majority (26/42, 62%) of low-frequency variants were against PIs. The most common mutations detected at >20% and 2%-20% mutation frequency differed for each drug class, these respectively being: L90M (n = 7) and M46IL (n = 10) for PIs; T215rev (n = 9) and D67GN (n = 4) for NRTIs; and K103N (n = 5) and G190E (n = 2) for NNRTIs. Combined TDR was more frequent in subtype B than non-B (OR = 0.38; 95% CI = 0.17-0.88; P = 0.024) and had minimal predicted effect on recommended first-line therapies.

CONCLUSIONS

The data suggest differences in the types of low-frequency compared with majority TDR variants that require a better understanding of the origins and clinical significance of low-frequency variants. This will better inform diagnostic and treatment strategies.

Pre-treatment minority HIV-1 drug resistance mutations and long term virological outcomes: is prediction possible?

Background

Although the use of highly active antiretroviral therapy in HIV positive individuals has proved to be effective in suppressing the virus to below detection limits of commonly used assays, virological failure associated with drug resistance is still a major challenge in some settings. The prevalence and effect of pre-treatment resistance associated variants on virological outcomes may also be underestimated because of reliance on conventional population sequencing data which excludes minority species. We investigated long term virological outcomes and the prevalence and pattern of pre-treatment minority drug resistance mutations in individuals initiating HAART at a local HIV clinic.

Methods

Patient’s records of viral load results and CD4 cell counts from routine treatment monitoring were used and additional pre-treatment blood samples for Sanger sequencing were obtained. A selection of pre-treatment samples from individuals who experienced virological failure were evaluated for minority resistance associated mutations to 1 % prevalence and compared to individuals who achieved viral suppression.

Results

At least one viral load result after 6 months or more of treatment was available for 65 out of 78 individuals followed for up to 33 months. Twenty (30.8 %) of the 65 individuals had detectable viremia and eight (12.3 %) of them had virological failure (viral load > 1000 RNA copies/ml) after at least 6 months of HAART. Viral suppression, achieved by month 8 to month 13, was followed by low level viremia in 10.8 % of patients and virological failure in one patient after month 20. There was potentially reduced activity to Emtricitabine or Tenofovir in three out of the eight cases in which minority drug resistance associated variants were investigated but detectable viremia occurred in one of these cases while the activity of Efavirenz was generally reduced in all the eight cases.

Conclusions

Early viral suppression was followed by low level viremia for some patients which may be an indication of failure to sustain viral suppression over time. The low level viremia may also be representing early stages of resistance development. The mutation patterns detected in the minority variants showed potential reduced drug sensitivity which highlights their potential to dominate after treatment initiation.

Trial registration

Not applicable.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0628-x) contains supplementary material, which is available to authorized users.

HIV Drug Resistance Mutations (DRMs) Detected by Deep Sequencing in Virologic Failure Subjects on Therapy from Hunan Province, China

Objective

Determine HIV drug resistance mutations (DRMs) prevalence at low and high levels in ART-experienced patients experiencing virologic failure (VF).

Methods

29 subjects from 18 counties in Hunan Province that experienced VF were evaluated for the prevalence of DRMs (Stanford DRMs with an algorithm value ≥15, include low-, intermediate and high-level resistance) by both Sanger sequencing (SS) and deep sequencing (DS) to 1% frequency levels.

Results

DS was performed on samples from 29 ART-experienced subjects; the median viral load 4.95×10⁴ c/ml; 82.76% subtype CRF01_AE. 58 DRMs were detected by DS. 18 DRMs were detected by SS. Of the 58 mutations detected by DS, 40 were at levels <20% frequency (26 NNRTI, 12 NRTI and 2 PI) and the majority of these 95.00% (38/40) were not detected by standard genotyping. Of these 40 low-level DRMs, 16 (40%) were detected at frequency levels of 1–4% and 24 (60%) at levels of 5–19%. SS detected 15 of 17 (88.24%) DRMs at levels ≥ 20% that were detected by DS. The only variable associated with the detection of DRMs by DS was ART adherence (missed doses in the prior 7 days); all patients that reported missing a dose in the last 7 days had DRMs detected by DS.

Conclusions

DS of VF samples from treatment experienced subjects infected with primarily AE subtype frequently identified Stanford HIVdb NRTI and NNRTI resistance mutations with an algorithm value 15. Low frequency level resistant variants detected by DS were frequently missed by standard genotyping in VF specimens from antiretroviral-experienced subjects.