Antiviral Activity of Lenacapavir Against HIV-2 Isolates and Drug-resistant HIV-2 Mutants.

The activity of lenacapavir against HIV-1 has been extensively evaluated in vitro, but comparable data for HIV-2 are scarce. We determined the anti-HIV-2 activity of lenacapavir using single-cycle infections of MAGIC-5A cells and multicycle infections of a T cell line. Lenacapavir exhibited low-nanomolar activity against HIV-2, but was 11- to 14-fold less potent against HIV-2 in comparison to HIV-1. Mutations in HIV-2 that confer resistance to other antiretrovirals did not confer cross-resistance to lenacapavir. Although lenacapavir-containing regimens might be considered for appropriate patients with HIV-2, more frequent viral load and/or CD4 testing may be needed to assess clinical response.

Effect of Human Immunodeficiency Virus Infection on Human Papillomavirus Clearance Among Women in Senegal, West Africa.

BACKGROUND: Persistent infection with high-risk human papillomavirus (HPV) is associated with development of invasive cervical cancer. METHODS: Longitudinal data was collected from 174 Senegalese women. We employed marginal Cox proportional hazards models to examine the effect of human immunodeficiency virus (HIV) status (HIV positive vs HIV negative) and HIV type (HIV-1 vs HIV-2 vs dual HIV-1/HIV-2) on clearance of type-specific HPV infection. Analyses were stratified by incident versus prevalent HPV infection. RESULTS: Incident HPV infections in HIV-positive women were less likely to clear than those in HIV-negative women (adjusted hazard ratio [HR] = 0.60; 95% confidence interval [CI], .38-.94). Among HIV-positive women, HIV-2-infected women and HIV-1/2 dually infected women were more likely to clear HPV incident infections than HIV-1-infected women (HR = 1.66; 95% CI, .95-2.92 and HR = 2.17; 95% CI, 1.12-4.22, respectively). Incident HPV infections in HIV-positive women with CD4 cell count ≤500 cells/µL were less likely to clear than those in HIV-positive women with CD4 cell count >500 cells/µL (HR = 0.65; 95% CI, .42-1.01). No significant associations were observed for prevalent HPV infections. CONCLUSIONS: HIV infection reduced the likelihood of clearance of incident HPV infection. Furthermore, among HIV-positive women, low CD4 cell count and dual HIV infection were each associated with reduced likelihood of clearance.

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.

Food insecurity predicts loss to follow-up among people living with HIV in Senegal, West Africa.

The goals of this study were to assess retention on antiretroviral therapy (ART) and to identify predictors of loss to follow-up (LTFU) among people living with HIV (PLHIV) in Senegal. HIV-positive individuals presenting for initiation of ART in Dakar and Ziguinchor were enrolled and followed for 12 months. Data were collected using interviews, clinical evaluations, laboratory analyses, chart review, and active patient tracing. Of the 207 individuals enrolled, 70% were female, 32% had no formal education, and 28% were severely food insecure. At the end of the follow-up period, 58% were retained on ART, 15% were deceased, 4% had transferred care, 5% had migrated, and 16% were lost to follow-up. Enrollment in Ziguinchor (OR 2.71 [1.01-7.22]) and severe food insecurity (OR 2.55 [1.09-5.96]) were predictive of LTFU. Sex, age, CD4 count, BMI <18.5, country of birth, marital status, number of children, household size, education, consultation with traditional healers, transportation time, and transportation cost were not associated with LTFU. The strongest predictor of severe food insecurity was lack of formal education (OR 2.75 [1.30-5.80]). Addressing the upstream drivers of food insecurity and implementing strategies to enhance food security for PLHIV may be effective approaches to reduce LTFU and strengthen the HIV care cascade in the region.

Long-term Experience and Outcomes of Programmatic Antiretroviral Therapy for Human Immunodeficiency Virus Type 2 Infection in Senegal, West Africa.

BACKGROUND: Programmatic treatment outcome data for people living with human immunodeficiency virus type 2 (HIV-2) in West Africa, where the virus is most prevalent, are scarce. METHODS: Adults with HIV-2 initiating or receiving antiretroviral therapy (ART) through the Senegalese national AIDS program were invited to participate in this prospective, longitudinal observational cohort study. We analyzed HIV-2 viral loads, CD4 cell counts, antiretroviral drug resistance, loss to follow-up, and mortality. We also examined changes in treatment guidelines over time and assessed progress toward the Joint United Nations Programme on HIV/AIDS (UNAIDS) 90-90-90 targets for HIV-2. RESULTS: We enrolled 291 participants at 2 sites for 926.0 person-years of follow-up over 13 years. Median follow-up time was 2.2 years per participant. There were 21 deaths reported (7.2%), and 117 individuals (40.2%) were lost to follow-up, including 43 (14.7%) who had an initial visit but never returned for follow-up. CD4 counts and HIV-2 viral suppression (< 50 copies/mL) at enrollment increased over calendar time. Over the study period, 76.7% of plasma viral loads for participants receiving ART were suppressed, and median CD4 gain was 84 cells/µL in participants' first 2 years on study. Since the UNAIDS 90-90-90 strategy was published, 88.1% of viral loads were suppressed. Fifteen percent of patients experienced virologic failure with no known resistance mutations, while 56% had evidence of multiclass drug resistance. CONCLUSIONS: Participants in the Senegalese national AIDS program are initiating ART earlier in the course of disease, and more modern therapeutic regimens have improved outcomes among those receiving therapy. Despite these achievements, HIV-2 treatment remains suboptimal, and significant challenges to improving care remain.

The impact of food insecurity on HIV outcomes in Senegal, West Africa: a prospective longitudinal study.

BACKGROUND: Understanding the impact of food insecurity on HIV outcomes is critical for the development and implementation of effective, evidence-based interventions to address food insecurity and improve the HIV care cascade. We conducted a prospective, longitudinal study to determine the impact of food insecurity on HIV outcomes in Senegal, West Africa. METHODS: HIV-infected individuals presenting for care and initiation of ART through the Senegalese National AIDS program in Dakar and Ziguinchor were eligible for enrollment. Data were collected using interviews, clinical evaluations, laboratory analyses, and chart review at enrollment, month 6, and month 12. Logistic regression was used to determine the association between food insecurity and HIV outcomes. RESULTS: Among the 207 participants in this study, 70% were female and the median age was 37 years. The majority (69%) were food insecure at enrollment, 29% were severely food insecure, and 38% were undernourished. Nearly a third (32%) had no formal education, 23% practiced agriculture, and 40% owned livestock. The median daily food expenditure per person was $0.58. The median round trip transportation time to clinic was 90 min (IQR 30-240). The median cost of transportation to clinic was $1.74. At month 12, 69% were food insecure, 23% were severely food insecure, and 14% were undernourished. At month 12, 43% had not disclosed their HIV status; food insecurity was associated with non-disclosure of HIV-status due to fear of stigmatization and feelings of shame. Severe food insecurity was a strong predictor of loss to follow-up (OR 3.13 [1.08-9.06]) and persistent severe food insecurity was associated with virologic failure (OR 5.14 [1.01-26.29]) and poor adherence to ART 8.00 [1.11-57.57]. Poor nutritional status was associated with poor immunologic recovery (OR 4.24 [1.56-11.47]), virologic failure (OR 3.39 [1.13-10.21]), and death (OR 3.35 [1.40-8.03]). CONCLUSION: Severity and duration of food insecurity are important factors in understanding the relationship between food insecurity and HIV outcomes. Our findings highlight the importance of nutritional status, socioeconomic opportunity, and self-stigmatization in the complex pathway between food insecurity and HIV outcomes. Interdisciplinary, multisectoral efforts are needed to develop and implement effective interventions to address food insecurity among people living with HIV.

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.

Large, Stable, Contemporary Interspecies Recombination Events in Circulating Human Herpes Simplex Viruses.

BACKGROUND: The ubiquitous human pathogens, herpes simplex virus (HSV)-1 and HSV-2, are distinct viral species that diverged approximately 6 million years ago. At least 4 small, ancient HSV-1 × HSV-2 interspecies recombination events have affected the HSV-2 genome, with recombinants and nonrecombinants at each locus circulating today. However, it is unknown whether interspecies recombination can affect other loci and whether new recombinants continue to be generated. METHODS: Using 255 newly sequenced and 230 existing HSV genome sequences, we comprehensively assessed interspecies recombination in HSV. RESULTS: Our findings show that the sizes and locations of interspecies recombination events in HSV-2 are significantly more variable than previously appreciated and that they can impact species-specific T-cell recognition of HSV. CONCLUSIONS: We describe 2 large (>5 kb) recombination events, one of which arose in its current host, demonstrating that interspecies recombination continues to occur today. These results raise concerns about the use of live-attenuated HSV-2 vaccines in high HSV-1 prevalence areas.

HIV-2 Drug Resistance Genotyping from Dried Blood Spots.

The treatment of HIV-2 in resource-limited settings (RLS) is complicated by the limited availability of HIV-2-active antiretroviral drugs and inadequate access to HIV-2 viral load and drug resistance testing. Dried blood spots (DBS)-based drug resistance testing, widely studied for HIV-1, has not been reported for HIV-2 and could present an opportunity to improve care for HIV-2-infected individuals. We selected 150 DBS specimens from ongoing studies of antiretroviral therapy (ART) for HIV-2 infection in Senegal and subjected them to genotypic drug resistance testing. Total nucleic acid was extracted from DBS, reverse transcribed, PCR amplified, and analyzed by population-based Sanger sequencing, and major drug resistance-associated mutations (RAM) were identified. Parallel samples from plasma and peripheral blood mononuclear cells (PBMC) were also genotyped. We obtained 58 protease/reverse transcriptase genotypes. Plasma viral load was significantly correlated with genotyping success (P < 0.001); DBS samples with corresponding plasma viral load >250 copies/ml had a success rate of 86.8%. In paired DBS-plasma genotypes, 83.8% of RAM found in plasma were also found in DBS, and replicate DBS genotyping revealed that a single test detected 86.7% of known RAM. These findings demonstrate that DBS-based genotypic drug resistance testing for HIV-2 is feasible and can be deployed in RLS with limited infrastructure.

Trends in Reported Sexual Behavior and Y-Chromosomal DNA Detection Among Female Sex Workers in the Senegal Preexposure Prophylaxis Demonstration Project.

BACKGROUND: Preexposure prophylaxis (PrEP) can reduce HIV acquisition among female sex workers (FSWs). However, changes in condomless sex frequency after PrEP initiation could reduce PrEP effectiveness when PrEP adherence is suboptimal as well as increase the risk of acquiring other sexually transmitted infections. Objective measures of condomless sex may be more accurate for determining changes in sexual behavior than self-reported measures. METHODS: We longitudinally measured self-reported condom use, number of clients, and presence of Y-chromosomal DNA (Yc-DNA) in vaginal swabs among 267 FSWs accessing PrEP at 4 clinics in Senegal between 2015 and 2016. We assessed trends in sexual behavior over time since PrEP initiation using generalized estimating equations and evaluated predictors of Yc-DNA detection. RESULTS: We found no increase in self-reported condomless sex with clients (odds ratio [OR], 0.94; 95% confidence interval [CI], 0.89-1.00), main partners (OR, 0.99; 95% CI, 0.96-1.02), or Yc-DNA detection (OR, 0.99; 95% CI, 0.90-1.08) over time since initiation. Y-chromosomal DNA was detected in 34 (22%) of 154 swabs tested and in 15 (26%) of 58 swabs from FSW reporting consistent condom use among both clients and main partners. Self-reported condom use with clients or main partners did not predict Yc-DNA detection. CONCLUSIONS: In a FSW PrEP demonstration project in Senegal, we found no evidence of risk compensation among FSWs on PrEP as measured by self-reported behavior or through Yc-DNA detection. Y-chromosomal DNA detection was frequently detected among FSWs reporting consistent condom use, highlighting limitations of self-reported sexual behavioral measures.

Large benefits to youth-focused HIV treatment-as-prevention efforts in generalized heterosexual populations: An agent-based simulation model.

Predominantly heterosexual HIV-1 epidemics like those in sub-Saharan Africa continue to have high HIV incidence in young people. We used a stochastic, agent-based model for age-disparate networks to test the hypothesis that focusing uptake and retention of ART among youth could enhance the efficiency of treatment as prevention (TasP) campaigns. We used the model to identify strategies that reduce incidence to negligible levels (i.e., < 0.1 cases/100 person-years) 20-25 years after initiation of a targeted TasP campaign. The model was parameterized using behavioral, demographic, and clinical data from published papers and national reports. To keep a focus on the underlying age effects we model a generalized heterosexual population with average risks (i.e., no MSM, no PWIDs, no sex workers) and no entry of HIV+ people from other regions. The model assumes that most people (default 95%, range in variant simulations 60-95%) are "linkable"; i.e., could get linked to effective care given sufficient resources. To simplify the accounting, we assume a rapid jump in the number of people receiving treatment at the start of the TasP campaign, followed by a 2% annual increase that continues until all linkable HIV+ people have been treated. Under historical scenarios of CD4-based targeted ART allocation and current policies of untargeted (random) ART allocation, our model predicts that viral replication would need to be suppressed in 60-85% of infected people at the start of the TasP campaign to drive incidence to negligible levels. Under age-based strategies, by contrast, this percentage dropped by 18-54%, depending on the strength of the epidemic and the age target. For our baseline model, targeting those under age 30 halved the number of people who need to be treated. Age-based targeting also minimized total and time-discounted AIDS deaths over 25 years. Age-based targeting yielded benefits without being highly exclusive; in a model in which 60% of infected people were treated, ~87% and ~58% of those initiating therapy during a campaign targeting those <25 and <30 years, respectively, fell outside the target group. Sensitivity analyses revealed that youth-focused TasP is beneficial due to age-related risk factors (e.g. shorter relationship durations), and an age-specific herd immunity (ASHI) effect that protects uninfected adolescents entering the sexually active population. As testing rates increase in response to UNAIDS 90-90-90 goals, efforts to link all young people to care and treatment could contribute enormously to ending the HIV epidemic.

Female genital mutilation and noninvasive cervical abnormalities and invasive cervical cancer in Senegal, West Africa: A retrospective study.

Female genital mutilation or cutting (FGM/C) is a traditional practice that affects a significant portion of women in sub-Saharan Africa, Egypt, areas of the Middle East and some countries in Asia. While clinical and epidemiological studies have established a close association between inflammation and carcinogenesis, particularly in epithelial cancers, the relationship between FGM/C and cervical cancer is not well known. We performed a secondary analysis using combined data from six research studies conducted in and around Dakar, Senegal from 1994 to 2012. Study subjects included both asymptomatic women who presented to outpatient clinics but were screened for cervical cancer, and women with cancer symptoms who were referred for cervical cancer treatment. We used unconditional logistic regression to estimate adjusted pooled odds ratios (ORs) and 95% confidence intervals (CI) for associations between FGM/C and (1) Invasive cervical cancer (ICC) and (2) noninvasive cervical abnormalities. After adjusting for confounding, women with ICC were 2.50 times more likely to have undergone FGM/C than women without cervical abnormalities (95% CI, 1.28-4.91). Restricting to HPV-positive women increased the strength of the association (OR = 4.23; 95% CI 1.73-10.32). No significant associations between FGM/C and noninvasive cervical abnormalities were observed, except in commercial sex workers with FGM/C (OR = 2.01; 95% CI 1.19-3.40). The potential increased risk for ICC suggested by our study warrants further examination. Study results may impact cancer prevention efforts in populations where FGM/C is practiced and draw awareness to the additional health risks associated with FGM/C.

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.

Prevalence, predictors, and management of advanced HIV disease among individuals initiating ART in Senegal, West Africa.

BACKGROUND: The WHO guidelines for the management of advanced HIV disease recommend a package of care consisting of rapid initiation of antiretroviral therapy (ART), enhanced screening and diagnosis of tuberculosis (TB) and cryptococcal meningitis, co-trimoxazole prophylaxis, isoniazid preventive therapy (IPT), fluconazole pre-emptive therapy, and adherence support. The goals of this study were to determine the prevalence of advanced HIV disease among individuals initiating ART in Senegal, to identify predictors of advanced disease, and to evaluate adherence to the WHO guidelines. METHODS: This study was conducted among HIV-positive individuals initiating ART in Dakar and Ziguinchor, Senegal. Clinical evaluations, laboratory analyses, questionnaires and chart review were conducted. Logistic regression was used to identify predictors of advanced disease. RESULTS: A total of 198 subjects were enrolled; 70% were female. The majority of subjects (71%) had advanced HIV disease, defined by the WHO as a CD4 count < 200 cells/mm3 or clinical stage 3 or 4. The median CD4 count was 185 cells/mm3. The strongest predictors of advanced disease were age ≥ 35 (OR 5.80, 95%CI 2.35-14.30) and having sought care from a traditional healer (OR 3.86, 95%CI 1.17-12.78). Approximately one third of subjects initiated ART within 7 days of diagnosis. Co-trimoxazole prophylaxis was provided to 65% of subjects with CD4 counts ≤350 cells/mm3 or stage 3 or 4 disease. TB symptom screening was available for 166 subjects; 54% reported TB symptoms. Among those with TB symptoms, 39% underwent diagnostic evaluation. Among those eligible for IPT, one subject received isoniazid. No subjects underwent CrAg screening or received fluconazole to prevent cryptococcal meningitis. CONCLUSIONS: This is the first study to report an association between seeking care from a traditional healer and presentation with WHO defined advanced disease in sub-Saharan Africa. Given the widespread use of traditional healers in sub-Saharan Africa, future studies to further explore this finding are indicated. Although the majority of individuals in this study presented with advanced disease and warranted management according to WHO guidelines, there were numerous missed opportunities to prevent HIV-associated morbidity and mortality. Programmatic evaluation is needed to identify barriers to implementation of the WHO guidelines and enhanced funding for operational research is indicated.

A Trial of a Single-tablet Regimen of Elvitegravir, Cobicistat, Emtricitabine, and Tenofovir Disoproxil Fumarate for the Initial Treatment of Human Immunodeficiency Virus Type 2 Infection in a Resource-limited Setting: 48-Week Results From Senegal, West Africa.

Background: There is an urgent need for safe and effective antiretroviral therapy (ART) for human immunodeficiency virus type 2 (HIV-2) infection. We undertook the first clinical trial of a single-tablet regimen containing elvitegravir, cobicistat, emtricitabine, and tenofovir disoproxil fumarate (E/C/F/TDF) to assess its effectiveness in HIV-2-infected individuals in Senegal, West Africa. Methods: HIV-2-infected, ART-naive adults with World Health Organization stage 3-4 disease or CD4 count <750 cells/µL were eligible for this 48-week, open-label trial. We analyzed HIV-2 viral loads (VL), CD4 counts, clinical and adverse events, mortality, and loss to follow-up. Results: We enrolled 30 subjects who initiated E/C/F/TDF. Twenty-nine subjects completed 48 weeks of follow-up. The majority were female (80%). There were no deaths, no new AIDS-associated clinical events, and 1 loss to follow-up. The median baseline CD4 count was 408 (range, 34-747) cells/µL, which increased by a median 161 (range, 27-547) cells/µL at week 48. Twenty-five subjects had baseline HIV-2 VL of <50 copies/mL of plasma. In those with detectable HIV-2 VL, the median was 41 (range, 10-6135) copies/mL. Using a modified intent-to-treat analysis (US Food and Drug Administration Snapshot method), 28 of 30 (93.3%; 95% confidence interval, 77.9%-99.2%) had viral suppression at 48 weeks. The 1 subject with virologic failure had multidrug-resistant HIV-2 (reverse transcriptase mutation: K65R; integrase mutations: G140S and Q148R) detected at week 48. There were 8 grade 3-4 adverse events; none were deemed study related. Adherence and acceptability were good. Conclusions: Our data suggest that E/C/F/TDF, a once-daily, single-tablet-regimen, is safe, effective, and well tolerated. Our findings support the use of integrase inhibitor-based regimens for HIV-2 treatment. Clinical Trials Registration: NCT02180438.

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.

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.

Four Amino Acid Changes in HIV-2 Protease Confer Class-Wide Sensitivity to Protease Inhibitors.

UNLABELLED: Protease is essential for retroviral replication, and protease inhibitors (PI) are important for treating HIV infection. HIV-2 exhibits intrinsic resistance to most FDA-approved HIV-1 PI, retaining clinically useful susceptibility only to lopinavir, darunavir, and saquinavir. The mechanisms for this resistance are unclear; although HIV-1 and HIV-2 proteases share just 38 to 49% sequence identity, all critical structural features of proteases are conserved. Structural studies have implicated four amino acids in the ligand-binding pocket (positions 32, 47, 76, and 82). We constructed HIV-2ROD9 molecular clones encoding the corresponding wild-type HIV-1 amino acids (I32V, V47I, M76L, and I82V) either individually or together (clone PRΔ4) and compared the phenotypic sensitivities (50% effective concentration [EC50]) of mutant and wild-type viruses to nine FDA-approved PI. Single amino acid replacements I32V, V47I, and M76L increased the susceptibility of HIV-2 to multiple PI, but no single change conferred class-wide sensitivity. In contrast, clone PRΔ4 showed PI susceptibility equivalent to or greater than that of HIV-1 for all PI. We also compared crystallographic structures of wild-type HIV-1 and HIV-2 proteases complexed with amprenavir and darunavir to models of the PRΔ4 enzyme. These models suggest that the amprenavir sensitivity of PRΔ4 is attributable to stabilizing enzyme-inhibitor interactions in the P2 and P2' pockets of the protease dimer. Together, our results show that the combination of four amino acid changes in HIV-2 protease confer a pattern of PI susceptibility comparable to that of HIV-1, providing a structural rationale for intrinsic HIV-2 PI resistance and resolving long-standing questions regarding the determinants of differential PI susceptibility in HIV-1 and HIV-2. IMPORTANCE: Proteases are essential for retroviral replication, and HIV-1 and HIV-2 proteases share a great deal of structural similarity. However, only three of nine FDA-approved HIV-1 protease inhibitors (PI) are active against HIV-2. The underlying reasons for intrinsic PI resistance in HIV-2 are not known. We examined the contributions of four amino acids in the ligand-binding pocket of the enzyme that differ between HIV-1 and HIV-2 by constructing HIV-2 clones encoding the corresponding HIV-1 amino acids and testing the PI susceptibilities of the resulting viruses. We found that the HIV-2 clone containing all four changes (PRΔ4) was as susceptible as HIV-1 to all nine PI. We also modeled the PRΔ4 enzyme structure and compared it to existing crystallographic structures of HIV-1 and HIV-2 proteases complexed with amprenavir and darunavir. Our findings demonstrate that four positions in the ligand-binding cleft of protease are the primary cause of HIV-2 PI resistance.