In vitro activity of dolutegravir against wild-type and integrase inhibitor-resistant HIV-2

Novel Dolutegravir and Lenacapavir Resistance Patterns in Human Immunodeficiency Virus Type 2 Infection: A Case Report

Background

The treatment management of human immunodeficiency virus (HIV)-2 infection presents greater challenges compared to HIV-1 infection, primarily because of inherent resistance against non-nucleoside reverse transcriptase inhibitors. Integrase strand transfer inhibitors, particularly dolutegravir, have improved treatment outcomes for people with HIV-2. Lenacapavir, a novel and potent antiretroviral capsid inhibitor, offers additional therapeutic options. However, limited knowledge exists regarding HIV-2 resistance against dolutegravir and lenacapavir.

Methods

We report the case of a treatment-experienced individual who did not achieve virological suppression with regimens containing dolutegravir and lenacapavir. Clinical monitoring, genotypic and phenotypic resistance assays, and in silico structural modeling were performed.

Results

Lenacapavir was added to a failing regimen of boosted darunavir, twice daily dolutegravir, and 2 nucleoside reverse transcriptase inhibitors. Initially, this addition led to a decline in the viral load and increase in CD4+ T-cell count, despite the identification of a previously unreported combination of integrase resistance mutations. However, virological suppression was not achieved and viral load, although reduced, resumed increasing. This rebound was associated with the development of an N73D capsid substitution in HIV-2, which conferred resistance against lenacapavir. Based on cell-based assays predicting hypersusceptibility to bictegravir, the regimen was adjusted to oral lenacapavir plus bictegravir/emtricitabine/tenofovir alafenamide, resulting in a resumption in viral load decline.

Conclusions

Although lenacapavir demonstrated therapeutic potential, our case underscores the critical need to combine it with other fully active antiretroviral agents to prevent the rapid emergence of resistance and achieve long-term virological control in treatment-experienced individuals with HIV-2.

Efficacy of Integrase Strand Transfer Inhibitors and the Capsid Inhibitor Lenacapavir against HIV-2, and Exploring the Effect of Raltegravir on the Activity of SARS-CoV-2

Retroviruses perpetuate their survival by incorporating a copy of their genome into the host cell, a critical step catalyzed by the virally encoded integrase. The viral capsid plays an important role during the viral life cycle, including nuclear importation in the case of lentiviruses and integration targeting events; hence, targeting the integrase and the viral capsid is a favorable therapeutic strategy. While integrase strand transfer inhibitors (INSTIs) are recommended as first-line regimens given their high efficacy and tolerability, lenacapavir is the first capsid inhibitor and the newest addition to the HIV treatment arsenal. These inhibitors are however designed for treatment of HIV-1 infection, and their efficacy against HIV-2 remains widely understudied and inconclusive, supported only by a few limited phenotypic susceptibility studies. We therefore carried out inhibition profiling of a panel of second-generation INSTIs and lenacapavir against HIV-2 in cell culture, utilizing pseudovirion inhibition profiling assays. Our results show that the tested INSTIs and lenacapavir exerted excellent efficacy against ROD-based HIV-2 integrase. We further evaluated the efficacy of raltegravir and other INSTIs against different variants of SARS-CoV-2; however, contrary to previous in silico findings, the inhibitors did not demonstrate significant antiviral activity.

Clinical Outcomes of Integrase Strand Transfer Inhibitors Containing Antiretroviral Therapy in HIV-2: A Narrative Review

The human immunodeficiency virus type 2 (HIV-2) is a particular subtype of HIV, which is endemic in West Africa and is characterized by a more indolent course than HIV-1. As people living with HIV-2 (PWH-2) are at risk for the development of acquired immunodeficiency syndrome and can transmit the virus, antiretroviral therapy is usually indicated. However, the optimal treatment of HIV-2 is unknown and historically the protease inhibitors (PIs) were a regular part of therapy. Nowadays, the use of integrase strand transfer inhibitors (INSTIs) in HIV-2 is increasing but the evidence supporting this approach is limited. In this narrative review, we outline the clinical data on the use of INSTI-containing antiretroviral therapy in HIV-2. We found that in the setting of treatment-naïve PWH-2, the use of INSTIs is successful, but also noted large heterogeneity in reported outcomes and that most cohorts are small with limited follow-up time. There is a lack of studies comparing the efficacy of INSTIs to other first-line options. For treatment-experienced PWH-2, the efficacy of INSTI is highly variable.

Safety and Efficacy of Triple Therapy With Dolutegravir Plus 2 Nucleoside Reverse Transcriptase Inhibitors in Treatment-Naive Human Immunodeficiency Virus Type 2 Patients: Results From a 48-Week Phase 2 Study

BACKGROUND

Integrase strand transfer inhibitor-based regimens are recommended for first-line therapy in human immunodeficiency virus type 2 (HIV-2). Nonetheless, dolutegravir (DTG) clinical trial data are lacking.

METHODS

We conducted a phase 2, single-arm, open-label trial to evaluate the safety and efficacy of a triple therapy regimen that included DTG in persons with HIV-2 (PWHIV-2) in Portugal. Treatment-naive adults receive DTG in combination with 2 nucleoside reverse transcriptase inhibitors (NRTIs). Treatment efficacy was evaluated by the proportion of patients who achieved a plasma viral load (pVL) <40 copies/mL and/or by the change from baseline in CD4+ T-cell count and in CD4/CD8 ratio at week 48.

RESULTS

A total of 30 patients were enrolled (22 women; median age, 55 years). At baseline, 17 (56.7%) individuals were viremic (median, pVL 190 copies/mL; interquartile range [IQR], 99-445). The median CD4 count was 438 cells/μL (IQR, 335-605), and the CD4/CD8 ratio was 0.8. Three patients discontinued the study. At week 48, all participants (27) had pVL <40 copies/mL. No virological failures were observed. Mean changes in CD4 count and CD4/CD8 ratio at week 48 were 95.59 cells/µL (95% confidence interval [CI], 28-163) and 0.32 (95% CI, .19 to .46). The most common drug-related adverse events were headache and nausea. One participant discontinued due to central nervous system symptoms. No serious adverse events were reported.

CONCLUSIONS

DTG plus 2 NRTIs is safe and effective as first-line treatment for PWHIV-2 with a tolerability profile previously known. No virological failures were observed that suggest a high potency of DTG in HIV-2 as occurs in HIV-1.

CLINICAL TRIALS REGISTRATION

M NCT03224338.

Antiretroviral Treatment of HIV-2 Infection: Available Drugs, Resistance Pathways, and Promising New Compounds

Currently, it is estimated that 1-2 million people worldwide are infected with HIV-2, accounting for 3-5% of the global burden of HIV. The course of HIV-2 infection is longer compared to HIV-1 infection, but without effective antiretroviral therapy (ART), a substantial proportion of infected patients will progress to AIDS and die. Antiretroviral drugs in clinical use were designed for HIV-1 and, unfortunately, some do not work as well, or do not work at all, for HIV-2. This is the case for non-nucleoside reverse transcriptase inhibitors (NNRTIs), the fusion inhibitor enfuvirtide (T-20), most protease inhibitors (PIs), the attachment inhibitor fostemsavir and most broadly neutralizing antibodies. Integrase inhibitors work well against HIV-2 and are included in first-line therapeutic regimens for HIV-2-infected patients. However, rapid emergence of drug resistance and cross-resistance within each drug class dramatically reduces second-line treatment options. New drugs are needed to treat infection with drug-resistant isolates. Here, we review the therapeutic armamentarium available to treat HIV-2-infected patients, as well as promising drugs in development. We also review HIV-2 drug resistance mutations and resistance pathways that develop in HIV-2-infected patients under treatment.

Intrinsic resistance of HIV-2 and SIV to the maturation inhibitor GSK2838232

GSK2838232 (GSK232) is a novel maturation inhibitor that blocks the proteolytic cleavage of HIV-1 Gag at the junction of capsid and spacer peptide 1 (CA/SP1), rendering newly-formed virions non-infectious. To our knowledge, GSK232 has not been tested against HIV-2, and there are limited data regarding the susceptibility of HIV-2 to other HIV-1 maturation inhibitors. To assess the potential utility of GSK232 as an option for HIV-2 treatment, we determined the activity of the compound against a panel of HIV-1, HIV-2, and SIV isolates in culture. GSK232 was highly active against HIV-1 isolates from group M subtypes A, B, C, D, F, and group O, with IC50 values ranging from 0.25-0.92 nM in spreading (multi-cycle) assays and 1.5-2.8 nM in a single cycle of infection. In contrast, HIV-2 isolates from groups A, B, and CRF01_AB, and SIV isolates SIVmac239, SIVmac251, and SIVagm.sab-2, were highly resistant to GSK232. To determine the role of CA/SP1 in the observed phenotypes, we constructed a mutant of HIV-2ROD9 in which the sequence of CA/SP1 was modified to match the corresponding sequence found in HIV-1. The resulting variant was fully susceptible to GSK232 in the single-cycle assay (IC50 = 1.8 nM). Collectively, our data indicate that the HIV-2 and SIV isolates tested in our study are intrinsically resistant to GSK232, and that the determinants of resistance map to CA/SP1. The molecular mechanism(s) responsible for the differential susceptibility of HIV-1 and HIV-2/SIV to GSK232 require further investigation.

High Instantaneous Inhibitory Potential of Bictegravir and the New Spiro-β-Lactam BSS-730A for HIV-2 Isolates from RAL-Naïve and RAL-Failing Patients

Integrase inhibitors (INIs) are an important class of drugs for treating HIV-2 infection, given the limited number of drugs active against this virus. While the clinical efficacy of raltegravir and dolutegravir is well established, the clinical efficacy of bictegravir for treating HIV-2 infected patients has not been determined. Little information is available regarding the activity of bictegravir against HIV-2 isolates from patients failing raltegravir-based therapy. In this study, we examined the phenotypic and matched genotypic susceptibility of HIV-2 primary isolates from raltegravir-naïve and raltegravir-failing patients to raltegravir, dolutegravir, and bictegravir, and to the new spiro-β-lactam BSS-730A. The instantaneous inhibitory potential (IIP) was calculated to help predict the clinical activity of bictegravir and BSS-730A. Isolates from raltegravir-naïve patients were highly sensitive to all INIs and BSS-730A. Combined integrase mutations E92A and Q148K conferred high-level resistance to raltegravir, and E92Q and T97A conferred resistance to raltegravir and dolutegravir. The antiviral activity of bictegravir and BSS-730A was not affected by these mutations. BSS-730A displayed strong antiviral synergism with raltegravir. Mean IIP values at Cmax were similar for all INIs and were not significantly affected by resistance mutations. IIP values were significantly higher for BSS-730A than for INIs. The high IIP values of bictegravir and BSS-730A for raltegravir-naïve and raltegravir-resistant HIV-2 isolates highlight their potential value for treating HIV-2 infection. Overall, the results are consistent with the high clinical efficacy of raltegravir and dolutegravir for HIV-2 infection and suggest a promising clinical profile for bictegravir and BSS-730A.

Treatment of Tuberculosis and the Drug Interactions Associated With HIV-TB Co-Infection Treatment

Tuberculosis (TB) is a communicable disease that is a major source of illness, one of the ten causes of mortality worldwide, and the largest cause of death from a single infectious agent Mycobacterium tuberculosis. HIV infection and TB are a fatal combination, with each speeding up the progression of the other. Barriers to integrated treatment as well as safety concerns on the co-management of HIV- TB co-infection do exist. Many HIV TB co-infected people require concomitant anti-retroviral therapy (ART) and anti-TB medication, which increases survival but also introduces certain management issues, such as drug interactions, combined drug toxicities, and TB immune reconstitution inflammatory syndrome which has been reviewed here. In spite of considerable pharmacokinetic interactions between antiretrovirals and antitubercular drugs, when the pharmacological characteristics of drugs are known and appropriate combination regimens, dosing, and timing of initiation are used, adequate clinical response of both infections can be achieved with an acceptable safety profile. To avoid undesirable drug interactions and side effects in patients, anti TB treatment and ART must be closely monitored. To reduce TB-related mortality among HIV-TB co-infected patients, ART and ATT (Anti Tuberculosis Treatment) outcomes must improve. Clinical practise should prioritise strategies to promote adherence, such as reducing treatment duration, monitoring and treating adverse events, and improving treatment success rates, to reduce the mortality risk of HIV-TB co-infection.

Spectrum of Activity of Raltegravir and Dolutegravir Against Novel Treatment-Associated Mutations in HIV-2 Integrase: A Phenotypic Analysis Using an Expanded Panel of Site-Directed Mutants

BACKGROUND

Integrase inhibitors (INIs) are a key component of antiretroviral therapy for human immunodeficiency virus-1 (HIV-1) and HIV-2 infection. Although INI resistance pathways are well-defined for HIV-1, mutations that emerge in HIV-2 in response to INIs are incompletely characterized.

METHODS

We performed systematic searches of GenBank and HIV-2 drug resistance literature to identify treatment-associated mutations for phenotypic evaluation. We then constructed a library of 95 mutants of HIV-2ROD9 that contained single or multiple amino acid changes in the integrase protein. Each variant was tested for susceptibility to raltegravir and dolutegravir using a single-cycle indicator cell assay.

RESULTS

We observed extensive cross-resistance between raltegravir and dolutegravir in HIV-2ROD9. HIV-2-specific integrase mutations Q91R, E92A, A153G, and H157Q/S, which have not been previously characterized, significantly increased the half maximum effective concentration (EC50) for raltegravir when introduced into 1 or more mutational backgrounds; mutations E92A/Q, T97A, and G140A/S conferred similar enhancements of dolutegravir resistance. HIV-2ROD9 variants encoding G118R alone, or insertions of residues SREGK or SREGR at position 231, were resistant to both INIs.

CONCLUSIONS

Our analysis demonstrates the contributions of novel INI-associated mutations to raltegravir and dolutegravir resistance in HIV-2. These findings should help to improve algorithms for genotypic drug resistance testing in HIV-2-infected individuals.

In vitro analysis of the replicative capacity and phenotypic susceptibility to integrase inhibitors of HIV-2 mutants with integrase insertions

BACKGROUND

HIV-2 resistance to integrase strand-transfer inhibitors (INSTIs) is characterized by two main pathways: (i) mutations at codons 143, 148 and155; and (ii) amino acid insertion after integrase codon 231 (231ins).

OBJECTIVES

To complete INSTI resistance data on HIV-2 by determining the viral replicative capacity and INSTI phenotypic susceptibility of integrase mutants obtained through site-directed mutagenesis.

METHODS

Site-directed mutants (SDMs) were constructed and viral stocks produced. Viral replicative capacity was assessed by measuring HIV-2 viral load at days 3, 7 and 14. In vitro phenotypic susceptibility was measured using the ANRS PBMC assay.

RESULTS

Viruses bearing 231ins did not present impaired replicative capacity, except the 231ins GIRGK mutant. A 231ins GK SDM was resistant to raltegravir and cabotegravir, but remained susceptible to dolutegravir and bictegravir. SDMs harbouring a 5 amino acid insertion (GYKGK or SREGK) were both resistant to all INSTIs. The SDM with T97A+N155H, with or without E92Q, was resistant to all INSTIs, except bictegravir.

CONCLUSIONS

These first data on the newly described resistance pathway 231ins, using site-directed mutagenesis, showed no measurable impact on viral fitness and confirmed the decreased susceptibility to a first-generation INSTI (raltegravir) and cabotegravir. Resistance to second-generation INSTIs (dolutegravir and bictegravir) occurred for mutants with a 5 amino acid 231ins.

Effectiveness of dolutegravir-based antiretroviral treatment for HIV-2 infection: retrospective observational study from Western India

BACKGROUND

Data on the use of dolutegravir for treatment of HIV-2 infection are limited.

OBJECTIVES

To assess the effectiveness of dolutegravir in people living with HIV-2 (PLHIV-2).

METHODS

A retrospective chart review was performed in two clinics in Western India. PLHIV-2 initiated on dolutegravir-based regimens were included. Response to treatment in both treatment-naive (TN) and treatment-experienced (TE; substitution and not in the context of failure) was assessed by CD4 counts and HIV-2 viral load (VL) in a proportion of individuals. The primary objective was to assess immunological effectiveness (absence of a drop in absolute CD4 counts by more than 30% of baseline). Change in absolute CD4 counts was assessed by fitting a mixed-effects model.

RESULTS

Sixty-two PLHIV-2 treated with dolutegravir were included. The immunological effectiveness rates (95% CI) were 91.9% (82.4%-96.5%), 92% (81.1%-96.8%) and 91.6% (64.6%-98.5%) amongst all, TE and TN individuals, respectively. Median change in absolute CD4 counts at 6, 12 and 18 months were +29 cells/mm3, +101 cells/mm3 and +72 cells/mm3, respectively. The virological effectiveness rates (HIV-2 VL <100 copies/mL) (95% CI) for all, TE and TN individuals were 88.8% (74.6%-95%), 89.6% (73.6%-96.4%) and 85.7% (48.6%-97.4%), respectively. Three clinical events were documented: spinal tuberculosis, relapsed non-Hodgkin's lymphoma and herpes simplex virus retinitis. One individual reported self-limiting somnolence.

CONCLUSIONS

Dolutegravir was well tolerated and associated with immunological, virological and clinical effectiveness in both TN and TE PLHIV-2 in a large cohort from Western India. Dolutegravir-based ART is an excellent option for treatment of individuals with HIV-2 infection.

Expanded Spectrum of Antiretroviral-Selected Mutations in Human Immunodeficiency Virus Type 2

BACKGROUND

HIV-1 and HIV-2 differ in their antiretroviral (ARV) susceptibilities and drug resistance mutations (DRMs).

METHODS

We analyzed published HIV-2 pol sequences to identify HIV-2 treatment-selected mutations (TSMs). Mutation prevalences were determined by HIV-2 group and ARV status. Nonpolymorphic mutations were those in <1% of ARV-naive persons. TSMs were those associated with ARV therapy after multiple comparisons adjustment.

RESULTS

We analyzed protease (PR) sequences from 483 PR inhibitor (PI)-naive and 232 PI-treated persons; RT sequences from 333 nucleoside RT inhibitor (NRTI)-naive and 252 NRTI-treated persons; and integrase (IN) sequences from 236 IN inhibitor (INSTI)-naive and 60 INSTI-treated persons. In PR, 12 nonpolymorphic TSMs occurred in ≥11 persons: V33I, K45R, V47A, I50V, I54M, T56V, V62A, A73G, I82F, I84V, F85L, L90M. In RT, 9 nonpolymorphic TSMs occurred in ≥10 persons: K40R, A62V, K70R, Y115F, Q151M, M184VI, S215Y. In IN, 11 nonpolymorphic TSMs occurred in ≥4 persons: Q91R, E92AQ, T97A, G140S, Y143G, Q148R, A153G, N155H, H156R, R231 5-amino acid insertions. Nine of 32 nonpolymorphic TSMs were previously unreported.

CONCLUSIONS

This meta-analysis confirmed the ARV association of previously reported HIV-2 DRMs and identified novel TSMs. Genotypic and phenotypic studies of HIV-2 TSMs will improve approaches to predicting HIV-2 ARV susceptibility and treating HIV-2-infected persons.

Survival among antiretroviral-experienced HIV-2 patients experiencing virologic failure with drug resistance mutations in Cote d'Ivoire West Africa

INTRODUCTION

The long-term prognosis of HIV-2-infected patients receiving antiretroviral therapy (ART) is still challenging, due to the intrinsic resistance to non-nucleoside reverse transcriptase inhibitors (NNRTI) and the suboptimal response to some protease inhibitors (PI). The objective was to describe the 5-years outcomes among HIV-2 patients harboring drug-resistant viruses.

METHODS

A clinic-based cohort of HIV-2-patients experiencing virologic failure, with at least one drug resistance mutation was followed from January 2012 to August 2017 in Côte d'Ivoire. Follow-up data included death, lost to follow-up (LTFU), immuno-virological responses. The Kaplan-Meier curve was used to estimate survival rates.

RESULTS

A total of 31 HIV-2 patients with virologic failure and with at least one drug resistance mutation were included. Two-third of them were men, 28(90.3%) were on PI-based ART-regimen at enrolment and the median age was 50 years (IQR = 46-54). The median baseline CD4 count and viral load were 456 cells/mm3 and 3.7 log10 c/mL respectively, and the participants have been followed-up in median 57 months (IQR = 24-60). During this period, 21 (67.7%) patients switched at least one antiretroviral drug, including two (6.5%) and three (9.7%) who switched to a PI-based and an integrase inhibitor-based regimen respectively. A total of 10(32.3%) patients died and 4(12.9%) were LTFU. The 36 and 60-months survival rates were 68.5% and 64.9%, respectively. Among the 17 patients remaining in care, six(35.3%) had an undetectable viral load (<50 c/mL) and for the 11 others, the viral load ranged from 2.8 to 5.6 log10 c/mL. Twelve patients were receiving lopinavir at the time of first genotype, five(42%) had a genotypic susceptibility score (GSS) ≤1 and 4(33%) a GSS >2.

CONCLUSIONS

The 36-months survival rate among ART-experienced HIV-2 patients with drug-resistant viruses is below 70%,lower than in HIV-1. There is urgent need to improve access to second-line ART for patients living with HIV-2 in West Africa.

Clinical experience with integrase inhibitors in HIV-2-infected individuals in Spain

BACKGROUND

HIV-2 is a neglected virus despite estimates of 1-2 million people being infected worldwide. The virus is naturally resistant to some antiretrovirals used to treat HIV-1 and therapeutic options are limited for patients with HIV-2.

METHODS

In this retrospective observational study, we analysed all HIV-2-infected individuals treated with integrase strand transfer inhibitors (INSTIs) recorded in the Spanish HIV-2 cohort. Demographics, treatment modalities, laboratory values, quantitative HIV-2 RNA and CD4 counts as well as drug resistance were analysed.

RESULTS

From a total of 354 HIV-2-infected patients recruited by the Spanish HIV-2 cohort as of December 2017, INSTIs had been given to 44, in 18 as first-line therapy and in 26 after failing other antiretroviral regimens. After a median follow-up of 13 months of INSTI-based therapy, undetectable viraemia for HIV-2 was achieved in 89% of treatment-naive and in 65.4% of treatment-experienced patients. In parallel, CD4 gains were 82 and 126 cells/mm3, respectively. Treatment failure occurred in 15 patients, 2 being treatment-naive and 13 treatment-experienced. INSTI resistance changes were recognized in 12 patients: N155H (5), Q148H/R (3), Y143C/G (3) and R263K (1).

CONCLUSIONS

Combinations based on INSTIs are effective and safe treatment options for HIV-2-infected individuals. However, resistance mutations to INSTIs are selected frequently in failing patients, reducing the already limited treatment options.

A New Mechanism of Resistance of Human Immunodeficiency Virus Type 2 to Integrase Inhibitors: A 5-Amino-Acid Insertion in the Integrase C-Terminal Domain

BACKGROUND

Integrase strand transfer inhibitors (INSTIs) are crucial for the treatment of human immunodeficiency virus (HIV) type 2 infection, due to limited available therapeutic options. Recently, bictegravir has been approved for HIV-1, but no data are currently available for HIV-2.

METHODS

We assessed the phenotypic susceptibility of 12 HIV-2 clinical isolates, obtained from 2 antiretroviral-naive and 10 antiretroviral-experienced patients, to 5 INSTIs (bictegravir, cabotegravir, dolutegravir, elvitegravir, and raltegravir) at the virological failure of an INSTI-based regimen. The 50% inhibitory concentrations (IC50s) were determined. Phenotypic inhibitory quotients were determined using trough INSTI plasma concentrations.

RESULTS

Wild-type viruses were susceptible to the 5 INSTIs, with IC50s in the nanomolar range. Bictegravir had a lower IC50 than the other INSTIs on those HIV-2 isolates bearing major, resistance-associated mutations (codons 143, 148, and 155). We identified a new resistance profile-a 5-amino-acid insertion at codon 231 of the HIV-2 integrase (231INS)-in 6 patients at the virological failure of a raltegravir-based regimen. Those patients had adequate raltegravir concentrations, but harbored multiresistant viruses with low genotypic susceptibility scores (median = 1.5). This insertion rendered isolates highly resistant to raltegravir and elvitegravir, and moderately resistant to dolutegravir and cabotegravir. Regarding bictegravir, 2 isolates remained susceptible and 2 had a slight increase in IC50 (3- to 5-fold change).

CONCLUSIONS

Our results confirm the potency of INSTI on HIV-2 clinical isolates with wild-type integrase. In addition, we identified a new resistance pathway, 231INS, selected in antiretroviral-experienced patients with multiresistant HIV-2 viruses. This highlights the need of close follow-up of those patients initiating an INSTI-based regimen.

HIV treatment in Guinea-Bissau: room for improvement and time for new treatment options

Despite advances in the treatment quality of HIV throughout the world, several countries are still facing numerous obstacles in delivering HIV treatment at a sufficiently high quality, putting patients' lives in jeopardy. The aim of this status article is to give an overview of HIV treatment outcomes in the West African country, Guinea-Bissau, and to assess how newer treatment strategies such as long-acting injectable drugs or an HIV cure may limit or stop the HIV epidemic in this politically unstable and low-resource setting. Several HIV cohorts in Guinea-Bissau have been established and are used as platforms for epidemiological, virological, immunological and clinical studies often with a special focus on HIV-2, which is prevalent in the country. The Bandim Health Project, a demographic surveillance site, has performed epidemiological HIV surveys since 1987 among an urban population in the capital Bissau. The Police cohort, an occupational cohort of police officers, has enabled analyses of persons seroconverting with estimated times of seroconversion among HIV-1 and HIV-2-infected individuals, allowing incidence measurements while the Bissau HIV Cohort and a newer Nationwide HIV Cohort have provided clinical data on large numbers of HIV-infected patients. The HIV cohorts in Guinea-Bissau are unique platforms for research and represent real life in many African countries. Poor adherence, lack of HIV viral load measurements, inadequate laboratory facilities, high rates of loss to follow-up, mortality, treatment failure and resistance development, are just some of the challenges faced putting the goal of "90-90-90″ for Guinea-Bissau well out of reach by 2020. Maintaining undetectable viral loads on treatment as a prerequisite of a cure strategy seems not possible at the moment. Thinking beyond one-pill-once-a-day, long-acting antiretroviral treatment options such as injectable drugs or implants may be a better treatment option in settings like Guinea-Bissau and may even pave the way for an HIV cure. If the delivery of antiretroviral treatment in sub-Saharan Africa in a sustainable way for the future should be improved by focusing on existing treatment options or through focusing on new treatment options remains to be determined.

Management of Virologic Failure and HIV Drug Resistance

Approximately 20% of people with HIV in the United States prescribed antiretroviral therapy are not virally suppressed. Thus, optimal management of virologic failure has a critical role in the ability to improve viral suppression rates to improve long-term health outcomes for those infected and to achieve epidemic control. This article discusses the causes of virologic failure, the use of resistance testing to guide management after failure, interpretation and relevance of HIV drug resistance patterns, considerations for selection of second-line and salvage therapies, and management of virologic failure in special populations.

Synthetic routes and structure-activity relationships (SAR) of anti-HIV agents: A key review

The worldwide increase of AIDS, an epidemic infection in constant development has an essential and still requires potent antiretroviral chemotherapeutic agents for reducing the integer of deaths caused by HIV. Thus, there is an urgent need for new anti-HIV drug candidates with increased strength, new targets, superior pharmacokinetic properties, and compact side effects. From this viewpoint, we first review present strategies of anti-HIV drug innovation and the synthesis of heterocyclic or natural compound as anti-HIV agents for facilitating the development of more influential and successful anti-HIV agents.

Comparison of the Antiviral Activity of Bictegravir against HIV-1 and HIV-2 Isolates and Integrase Inhibitor-Resistant HIV-2 Mutants

We compared the activity of the integrase inhibitor bictegravir against HIV-1 and HIV-2 using a culture-based, single-cycle assay. Values of 50% effective concentrations ranged from 1.2 to 2.5 nM for 9 HIV-1 isolates and 1.4 to 5.6 nM for 15 HIV-2 isolates. HIV-2 integrase mutants G140S/Q148R and G140S/Q148H were 34- and 110-fold resistant to bictegravir, respectively; other resistance-associated mutations conferred ≤5-fold changes in bictegravir susceptibility. Our findings indicate that bictegravir-based antiretroviral therapy should be evaluated in HIV-2-infected individuals.

90-90-90 for HIV-2? Ending the HIV-2 epidemic by enhancing care and clinical management of patients infected with HIV-2

Distinct from HIV-1 and often neglected in the global campaign to end the AIDS epidemic, HIV-2 presents unique and underappreciated challenges in diagnosis, clinical care, antiretroviral therapy (ART), and HIV programmatic management. Here, we review the epidemiology and natural history of HIV-2, diagnostics and algorithms for accurately diagnosing and differentiating HIV-2 from HIV-1, the unique features of HIV-2 ART and drug resistance, and the clinical care and management of patients infected with HIV-2 in both developed and resource-limited settings. Ultimately, further research is needed to address the gaps in our knowledge of HIV-2 infection, increased resources are needed to specifically target HIV-2 as part of the UNAIDS/WHO 90-90-90 campaign to end AIDS, and increased determination is needed to better advocate for inclusion of people living with HIV-2 in global HIV/AIDS initiatives.

In Vitro Antiviral Activity of Cabotegravir against HIV-2

We examined the antiviral activity of the integrase inhibitor (INI) cabotegravir against HIV-2 isolates from INI-naive individuals. HIV-2 was sensitive to cabotegravir in single-cycle and spreading-infection assays, with 50% effective concentrations (EC₅₀s) in the low to subnanomolar range; comparable results were obtained for HIV-1 in both assay formats. Our findings suggest that cabotegravir should be evaluated in clinical trials as a potential option for antiretroviral therapy and preexposure prophylaxis in HIV-2-prevalent settings.

Drug resistance mutations in HIV-2 patients failing raltegravir and influence on dolutegravir response

Background

A broader extent of amino acid substitutions in the integrase of HIV-2 compared with HIV-1 might enable greater cross-resistance between raltegravir and dolutegravir in HIV-2 infection. Few studies have examined the virological response to dolutegravir in HIV-2 patients that failed raltegravir.

Methods

All patients recorded in the HIV-2 Spanish cohort were examined. The integrase coding region was sequenced in viraemic patients. Changes associated with resistance to raltegravir and dolutegravir in HIV-1 were recorded.

Results

From 319 HIV-2-infected patients recorded in the HIV-2 Spanish cohort, 53 integrase sequences from 30 individuals were obtained (20 raltegravir naive and 10 raltegravir experienced). Only one secondary mutation (E138A) was found in one of the 20 raltegravir-naive HIV-2 patients. For raltegravir-experienced individuals, the resistance mutation profile in 9 of 10 viraemic patients was as follows: N155H + A153G/S (four); Y143G + A153S (two); Q148R + G140A/S (two); and Y143C + Q91R (one). Of note, all patients with Y143G and N155H developed a rare non-polymorphic mutation at codon 153. Rescue therapy with dolutegravir was given to 5 of these 10 patients. After >6 months on dolutegravir therapy, three patients with baseline N155H experienced viral rebound. In two of them N155H was replaced by Q148K/R and in another by G118R.

Conclusions

A wide repertoire of resistance mutations in the integrase gene occur in HIV-2-infected patients failing on raltegravir. Although dolutegravir may allow successful rescue in most HIV-2 raltegravir failures, we report and characterize three cases of dolutegravir resistance in HIV-2 patients, emerging variants Q148K and Q148R and a novel change G118R.

Antiretroviral treatment of HIV-2 infection

HIV-2 is a neglected virus despite estimates of 1–2 million people being infected worldwide. AIDS develops more slowly in HIV-2 than HIV-1. Outside endemic regions, HIV-2 is mostly found in immigrants from west Africa or their sex partners. There are four major caveats when treating HIV-2. First, some antiretrovirals are not or only partially active against HIV-2. Second, CD4 declines in HIV-2 occur slowly, but CD4 recovery is smaller with antiretroviral treatment. Third, both virological failure and rapid emergence of drug resistance occur more frequently in HIV-2 than HIV-1. Finally, misdiagnosis of HIV-2 in patients wrongly considered as infected with HIV-1 or in those dually infected may result in treatment failures with undetectable HIV-1 RNA. Integrase inhibitors, and especially dolutegravir, should be part of any preferred HIV-2 antiretroviral combination nowadays.

MK-8591 (4'-Ethynyl-2-Fluoro-2'-Deoxyadenosine) Exhibits Potent Activity against HIV-2 Isolates and Drug-Resistant HIV-2 Mutants in Culture

There is a pressing need to identify more effective antiretroviral drugs for HIV-2 treatment. Here, we show that the investigational compound MK-8591 (4'-ethynyl-2-fluoro-2'-deoxyadenosine [EFdA]) is highly active against group A and B isolates of HIV-2; 50% effective concentrations [EC₅₀] for HIV-2 were, on average, 4.8-fold lower than those observed for HIV-1. MK-8591 also retains potent activity against multinucleoside-resistant HIV-2 mutants (EC₅₀ ≤ 11 nM). These data suggest that MK-8591 may have antiviral activity in HIV-2-infected individuals.

Clinical benefit of dolutegravir in HIV-1 management related to the high genetic barrier to drug resistance

This manuscript reviews the reasons why Integrase inhibitors should now routinely constitute a part of first line antiretroviral therapy for the treatment of HIV disease. The use of these drugs that are generally well tolerated has resulted in far less drug resistance than was the case with most other categories of antiviral compounds. In addition, the integrase inhibitor family of drugs has been less prone to the problem of transmitted drug resistance which is due to a wide variety of substitutions in the HIV genome that can be sexually transmitted from one person to another. However, the use of integrase inhibitors in first line therapy may unfortunately not soon happen in developing country settings where non-nucleoside reverse transcriptase inhibitors continue to be a mainstay of initial therapy, primarily for reasons of cost. As long as this situation continues, problems of drug resistance and transmitted drug resistance will be common in such settings. Current evidence also suggests that the use of dolutegravir as a first line integrase inhibitor may limit development of drug resistance to an extent that exceeds the use of other members of this family of drugs. This may be due to particular patterns of resistance involving dolutegravir, whereby the mutations that are associated with resistance against this compound may actually diminish both HIV replication capacity as well as integrase enzymatic activity in a far-reaching and unique manner. This gives potential hope that the use of dolutegravir in first line therapy could actually form part of the long-sought goal of attainment of a functional cure for HIV disease.

Foamy-like endogenous retroviruses are extensive and abundant in teleosts

Recent discoveries indicate that the foamy virus (FV) (Spumavirus) ancestor may have been among the first retroviruses to appear during the evolution of vertebrates, demonstrated by foamy endogenous retroviruses present within deeply divergent hosts including mammals, coelacanth, and ray-finned fish. If they indeed existed in ancient marine environments hundreds of millions of years ago, significant undiscovered diversity of foamy-like endogenous retroviruses might be present in fish genomes. By screening published genomes and by applying PCR-based assays of preserved tissues, we discovered 23 novel foamy-like elements in teleost hosts. These viruses form a robust, reciprocally monophyletic sister clade with sarcopterygian host FV, with class III mammal endogenous retroviruses being the sister group to both clades. Some of these foamy-like retroviruses have larger genomes than any known retrovirus, exogenous or endogenous, due to unusually long gag-like genes and numerous accessory genes. The presence of genetic features conserved between mammalian FV and these novel retroviruses attests to a foamy-like replication biology conserved for hundreds of millions of years. We estimate that some of these viruses integrated recently into host genomes; exogenous forms of these viruses may still circulate.

Susceptibility of porcine endogenous retrovirus to anti-retroviral inhibitors

BACKGROUND

Porcine endogenous retrovirus (PERV) is an endogenous retrovirus that poses a risk of iatrogenic transmission in the context of pig-to-human xenotransplantation. The lack of a means to control PERV infection in the context of pig-to-human xenotransplantation is a major concern in the field. In this study, we set out to evaluate the ability of currently licensed anti-HIV drugs, and other types of anti-retroviral compounds, to inhibit PERV infection in vitro.

METHODS

We used target cells stably expressing one of the known PERV viral receptors, an infectious molecular clone, PERV-A 14/220, and at least one drug from each class of anti-retroviral inhibitors as well as off-label drugs shown to have anti-viral activities. The susceptibility of PERV-A 14/220 LacZ to the anti-retroviral drugs was determined from infected cells by histochemical staining.

RESULTS

We extend the results of previous studies by showing that, in addition to raltegravir, dolutegravir is found to have a potent inhibitory activity against PERV replication (IC50 8.634 ±0.336 and IC50 3.06 ± 0.844 nM, respectively). The anti-HIV drug zidovudine (AZT) showed considerable anti-PERV activity with IC50 of 1.923 ±0.691 μM as well.

CONCLUSIONS

The study results indicate that some of the licensed anti-retroviral drugs may be useful for controlling PERV infection. However, the efficacy at nanomolar concentrations put forward integrase inhibitors as a drug that has the potential to be useful in the event that xenotransplantation recipients have evidence of PERV transmission and replication.

HIV-1 Group O Resistance Against Integrase Inhibitors

BACKGROUND

HIV-1 group O (HIV-O) is a rare variant that is characterized by a high number of natural polymorphisms in the integrase coding region that may impact on susceptibility to integrase strand transfer inhibitors (INSTIs) and on the emergence of resistance substitutions. We previously reported that HIV-O is more susceptible to RAL than HIV-1 group M (HIV-M).

METHODS

The aim of this study was to assess pathways of resistance to INSTIs in group 0 variants. Accordingly, we selected for resistance to each of raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG) in cord blood mononuclear cells using HIV group O subtypes A and B, an HIV-O divergent isolate, and HIV-1 group M (subtype B, which served as a reference). Site-directed mutagenesis was performed on the pCOM2.5 HIV group 0 infectious clone to ascertain the impact of INSTI resistance substitutions at positions Q148R, N155H, and R263K within integrase on susceptibility to INSTIs and infectiousness.

RESULTS

Cell culture selections of group O variants yielded similar patterns of resistance to RAL, EVG, and DTG as observed for subtype B. In the DTG selections, subtype B yielded S153Y, whereas a natural S153A polymorphism sometimes led to A153V in group O. The pCMO2.5/Q148R and pCMO2.5/N155H variants displayed far higher levels of resistance to DTG (>1000 FC) than was seen for group M viruses.

CONCLUSIONS

HIV-O harboring Q148R and N155H shows higher resistance to DTG compared with HIV-M subtype B.

The Nucleoside Analog BMS-986001 Shows Greater In Vitro Activity against HIV-2 than against HIV-1

Treatment options for individuals infected with human immunodeficiency virus type 2 (HIV-2) are restricted by the intrinsic resistance of the virus to nonnucleoside reverse transcriptase inhibitors (NNRTIs) and the reduced susceptibility of HIV-2 to several protease inhibitors (PIs) used in antiretroviral therapy (ART). In an effort to identify new antiretrovirals for HIV-2 treatment, we evaluated the in vitro activity of the investigational nucleoside analog BMS-986001 (2',3'-didehydro-3'-deoxy-4'-ethynylthymidine; also known as censavudine, festinavir, OBP-601, 4'-ethynyl stavudine, or 4'-ethynyl-d4T). In single-cycle assays, BMS-986001 inhibited HIV-2 isolates from treatment-naive individuals, with 50% effective concentrations (EC50s) ranging from 30 to 81 nM. In contrast, EC50s for group M and O isolates of HIV-1 ranged from 450 to 890 nM. Across all isolates tested, the average EC50 for HIV-2 was 9.5-fold lower than that for HIV-1 (64 ± 18 nM versus 610 ± 200 nM, respectively; mean ± standard deviation). BMS-986001 also exhibited full activity against HIV-2 variants whose genomes encoded the single amino acid changes K65R and Q151M in reverse transcriptase, whereas the M184V mutant was 15-fold more resistant to the drug than the parental HIV-2ROD9 strain. Taken together, our findings show that BMS-986001 is an effective inhibitor of HIV-2 replication. To our knowledge, BMS-986001 is the first nucleoside analog that, when tested against a diverse collection of HIV-1 and HIV-2 isolates, exhibits more potent activity against HIV-2 than against HIV-1 in culture.