Immunogenic arenavirus vector SIV vaccine reduces setpoint viral load in SIV-challenged rhesus monkeys.

HIV affects more than 38 million people worldwide. Although HIV can be effectively treated by lifelong combination antiretroviral therapy, only a handful of patients have been cured. Therapeutic vaccines that induce robust de novo immune responses targeting HIV proteins and latent reservoirs will likely be integral for functional HIV cure. Our study shows that immunization of naïve rhesus macaques with arenavirus-derived vaccine vectors encoding simian immunodeficiency virus (SIVSME543 Gag, Env, and Pol) immunogens is safe, immunogenic, and efficacious. Immunization induced robust SIV-specific CD8+ and CD4+ T-cell responses with expanded cellular breadth, polyfunctionality, and Env-binding antibodies with antibody-dependent cellular cytotoxicity. Vaccinated animals had significant reductions in median SIV viral load (1.45-log10 copies/mL) after SIVMAC251 challenge compared with placebo. Peak viral control correlated with the breadth of Gag-specific T cells and tier 1 neutralizing antibodies. These results support clinical investigation of arenavirus-based vectors as a central component of therapeutic vaccination for HIV cure.

Building global vaccine manufacturing capacity: Spotlight on Africa.

Africa is set to experience a three-fold increase in vaccine demand by 2040, yet the continent possesses few domestic capabilities for vaccine production. This lack of production capacity, heavy reliance on foreign aid, disruptions of hard-won immunization progress due to the effects of the COVID-19 pandemic, and fluctuating vaccine market dynamics threaten to hinder ongoing efforts to increase vaccination rates on the continent. In order meet the vaccine demands of a rapidly growing population, and to be able to provide novel vaccines to its population in the future, the African continent must develop a sustainable vaccine manufacturing infrastructure. The African Union, in partnership with the Africa Centres for Disease Control and Prevention, recently set forth its Program for African Vaccine Manufacturing Framework for Action, which sets the goal of Africa producing 60 % of its vaccine needs by 2040. To meet these goals, African governments and their multinational, philanthropic, and private sector partners must work to secure low-cost financing and provide a favourable regulatory environment for nascent African vaccine manufacturers. Doing so will save lives, safeguard the health of the continent's current and future citizens, and contribute to economic growth through the development of local bioeconomies.

A Qualitative Study Exploring Motivators and Barriers to COVID-19 Vaccine Uptake among Adults in South Africa and Zimbabwe.

While vaccines are a well-established method of controlling the spread of infectious diseases, vaccine hesitancy jeopardizes curbing the spread of COVID-19. Through the Vaccine Information Network (VIN), this study explored barriers and motivators to COVID-19 vaccine uptake. We conducted 18 focus group discussions with male and female community members, stratified by country, age group, and-for Zimbabwe only-by HIV status. Participants' median age across both countries was 40 years (interquartile range of 22-40), and most (65.9%) were female. We conceptualized the key themes within the World Health Organization's Strategic Advisory Group of Experts on Immunization (SAGE) 3C (convenience, confidence, complacency) vaccine hesitancy model. Barriers to vaccine uptake-lack of convenience, low confidence, and high complacency-included inaccessibility of vaccines and vaccination sites, vaccine safety and development concerns, and disbelief in COVID-19's existence. Motivators to vaccine uptake-convenience, confidence, and low complacency-included accessibility of vaccination sites, user-friendly registration processes, trust in governments and vaccines, fear of dying from COVID-19, and knowing someone who had died from or become infected with COVID-19. Overall, vaccine hesitancy in South Africa and Zimbabwe was influenced by inconvenience, a lack of confidence, and high complacency around COVID-19 vaccines.

Evaluation of HIV-1 reservoir size and broadly neutralizing antibody susceptibility in acute antiretroviral therapy-treated individuals.

OBJECTIVE: Persistence of the viral reservoir is the main barrier to curing HIV. Initiation of ART during acute HIV infection can limit the size and diversity of the reservoir. In depth characterization of the reservoir in individuals who initiate ART during acute infection will be critical for clinical trial design and cure strategies. METHODS: Four cohorts with participants who initiated ART during acute infection or during chronic infection were enrolled in a cross-sectional, noninterventional study. Viral reservoir was evaluated by the Intact Proviral DNA Assay (IPDA), the Total HIV DNA Assay (THDA) and the Quantitative Viral Outgrowth Assay (QVOA). Viral diversity and susceptibility to V3-glycan bNAbs were determined by genotyping of the viral envelope gene. RESULTS: Participants who initiated ART during the acute Fiebig I-IV stages had lower level of total HIV DNA than participants who initiated ART during chronic infection whereas no difference was observed in intact HIV DNA or outgrowth virus. Participants who initiated ART during Fiebig I-IV also had lower viral diversity and appeared to have higher susceptibility to bNAbs than participants initiating ART during chronic infection. CONCLUSION: Individuals initiating ART during Fiebig I-IV had small viral reservoirs, low viral diversity, and high susceptibility to bNAbs, and would be an optimal target population for proof-of-concept HIV cure trials.

Brief Report: Efficacy and Safety of Bictegravir/Emtricitabine/Tenofovir Alafenamide in Females Living With HIV: An Integrated Analysis of 5 Trials.

BACKGROUND: We characterized the efficacy and safety of bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF) in a broad population of pediatric/adolescent/adult/elderly females living with HIV (FWH). SETTING: Integrated analysis. METHODS: Available data from 5 trials were integrated. Week 48 virologic suppression (HIV-1 RNA <50 copies/mL), resistance, adverse events (AEs), and laboratory parameters were assessed. RESULTS: Three hundred and seventy-three FWH [304 virologically suppressed; 69 antiretroviral therapy (ART)-naive] received B/F/TAF [data from comparator regimens available for 306 individuals (236 virologically suppressed and 70 ART-naive participants)]. Virologic suppression rates with B/F/TAF at week 48 were high regardless of age in participants virologically suppressed at baseline (≥95%) and in ART-naive participants (≥87%). Virologic suppression rates were similar in B/F/TAF and comparator regimens (both virologically suppressed and ART-naive groups). Treatment-emergent resistance was not detected in the B/F/TAF group. AEs considered related to study drugs were experienced by 9.2% (B/F/TAF) and 5.5% (comparator regimen) of virologically suppressed participants and 15.9% (B/F/TAF) and 31.4% (comparator regimen) of ART-naive participants. For virologically suppressed and ART-naive FWH combined, only 1 of the 373 B/F/TAF-treated and 2 of the 306 comparator-regimen participants discontinued because of AEs (none were bone/renal/hepatic AEs); grade 3/4 AEs were experienced by 5.1% (B/F/TAF) and 7.8% (comparator regimen); and grade 3/4 elevation of low-density lipoprotein/total cholesterol occurred in 2.7%/0.3% (B/F/TAF) and 5.9%/2.0% (comparator regimen). At week 48, median changes from baseline estimated glomerular filtration rate in adults were <5 mL/min; results were similar in B/F/TAF and comparator-regimen groups. CONCLUSION: B/F/TAF treatment was effective and well tolerated over 48 weeks, confirming B/F/TAF as an option for a broad population of FWH.

Survival following screening and preemptive antifungal therapy for subclinical cryptococcal disease in advanced HIV infection.

OBJECTIVES: Our study's primary objective was to compare 1-year survival rates between serum cryptococcal antigen (sCrAg)-positive and sCrAg-negative HIV-positive individuals with CD4+ cell counts less than 100 cells/µl without symptoms of meningitis in Zimbabwe. DESIGN: This was a prospective cohort study. METHODS: Participants were enrolled as either sCrAg-positive or sCrAg-negative and followed up for 52 weeks or less, with death as the outcome. Lumbar punctures were recommended to all sCrAg-positives and inpatient management with intravenous amphotericin B and high-dose fluconazole was recommended to those with disseminated Cryptococcus. Antiretroviral therapy was initiated immediately in sCrAg-negatives and after at least 4 weeks following initiation of antifungals in sCrAg-positives. Multivariable logistic regression models were used to determine risk factors for mortality. RESULTS: We enrolled 1320 participants and 130 (9.8%) were sCrAg positive, with a median sCrAg titre of 1 : 20. Sixty-six (50.8%) sCrAg-positives had lumbar punctures and 16.7% (11/66) had central nervous system (CNS) dissemination. Cryptococcal blood cultures were performed in 129 sCrAg-positives, with 10 (7.8%) being positive. One-year (48-52 weeks) survival rates were 83.9 and 76.1% in sCrAg-negatives and sCrAg-positives, respectively, P = 0.011. Factors associated with increased mortality were a positive sCrAg, CD4+ cell count less than 50 cells/µl and having presumptive tuberculosis (TB) symptoms. CONCLUSION: Our study reports a high prevalence of subclinical cryptococcal antigenemia and reiterates the importance of TB and a positive sCrAg as risk factors for mortality in advanced HIV disease (AHD). Therefore, TB and sCrAg screening remains a crucial component of AHD package, hence it should always be part of the comprehensive clinical evaluation in AHD patients.

Diagnostic Accuracy of Pan-Degenerate Amplification and Adaptation Assay for HIV-1 Drug Resistance Mutation Analysis in Low- and Middle-Income Countries.

HIV drug resistance (HIVDR) is a barrier to sustained virologic suppression in low- and middle-income countries (LMICs). Point mutation assays targeting priority drug resistance mutations (DRMs) are being evaluated to improve access to HIVDR testing. In a cross-sectional study (June 2018 to September 2019), we evaluated the diagnostic accuracy of a simple and rapid HIVDR assay (the pan-degenerate amplification and adaptation [PANDAA] assay targeting the mutations K65R, K103NS, M184VI, Y181C, and G190A) compared to Sanger sequencing and next-generation sequencing (NGS). Plasma samples from adolescents and young adults (aged 10 to 24 years) failing antiretroviral therapy (viral load, >1,000 copies/ml on 2 consecutive occasions 1 month apart) were analyzed. Sensitivity and specificity of the PANDAA assay were determined by a proprietary application designed by Aldatu Biosciences. Agreement between genotyping methods was evaluated using Cohen's kappa coefficient. One hundred fifty samples previously characterized by Sanger sequencing were evaluated using PANDAA. For all DRMs detected, PANDAA showed a sensitivity and specificity of 98% and 94%, respectively. For nucleotide reverse transcriptase inhibitor DRMs, sensitivity and specificity were 98% (95% confidence interval [CI], 92% to 100%) and 100% (94% to 100%), respectively. For non-nucleotide reverse transcriptase inhibitor DRMs, sensitivity and specificity were 100% (97% to 100%) and 76% (61% to 87%), respectively. PANDAA showed strong agreement with Sanger sequencing for K65R, K103NS, M184VI, and G190A (kappa > 0.85) and substantial agreement for Y181C (kappa = 0.720). Of the 21 false-positive samples genotyped by PANDAA, only 6 (29%) were identified as low-abundance variants by NGS. With the high sensitivity and specificity to detect major DRMs, PANDAA could represent a simple and rapid alternative HIVDR assay in LMICs.

Plasma concentration of neurofilament light chain protein decreases after switching from tenofovir disoproxil fumarate to tenofovir alafenamide fumarate.

BACKGROUND: Because tenofovir alafenamide (TAF) leads to significantly lower plasma tenofovir concentrations than tenofovir disoproxil fumarate (TDF) and is a stronger substrate for P-glycoprotein (P-gp) than TDF, TAF could lead to decreased central nervous system (CNS) tenofovir exposure than TDF. We aimed to determine if switching from TDF to TAF increases the risk of neuronal injury, by quantifying plasma levels of neurofilament light protein (NfL), a sensitive marker of neuronal injury in HIV CNS infection. METHODS: Plasma NfL concentration was measured at baseline, week 24, and week 84 in stored plasma samples from 416 participants (272 switching to elvitegravir (E)/cobicistat (C)/emtricitabine (F)/TAF and 144 continuing E/C/F/TDF) enrolled in the randomized, active-controlled, multicenter, open-label, noninferiority Gilead GS-US-292-0109 trial. RESULTS: While plasma NfL levels in both groups were within the normal range, we found a small but significant decrease in the E/C/F/TAF arm after 84 weeks from a geometric mean of 9.3 to 8.8 pg/mL (5.4% decline, 95% CI 2.0-8.4, p = 0.002). This change was significantly different (p = 0.001) from that of the E/C/F/TDF arm, in which plasma NfL concentration changed from 9.7 pg/mL at baseline to 10.2 pg/mL at week 84 (5.8% increase, 95% CI -0.8-12.9, p = 0.085). This increase is in line with what could be expected in normal ageing. Plasma NfL concentrations significantly correlated with age. No correlation was found between plasma NfL and serum creatinine. CONCLUSIONS: We found no biomarker evidence of CNS injury when switching from TDF to TAF. It is unclear whether the small decrease in plasma NfL found after switch to TAF is of any clinical relevance, particularly with plasma NfL levels in both arms remaining within the limits found in HIV-negative controls. These results indicate that switching from TDF to TAF appears safe with regard to neuronal injury.

Switching to Fixed-Dose Bictegravir, Emtricitabine, and Tenofovir Alafenamide (B/F/TAF) in Virologically Suppressed HIV-1 Infected Women: A Randomized, Open-Label, Multicenter, Active-Controlled, Phase 3, Noninferiority Trial.

BACKGROUND: Bictegravir, coformulated with emtricitabine/tenofovir alafenamide as a fixed-dose combination (B/F/TAF), is recommended for treatment of HIV-1-infection. Multiple studies of B/F/TAF in treatment-naive and virologically suppressed cohorts have shown high efficacy and tolerability with no treatment-emergent resistance through 48 weeks. Participants in these studies have been predominantly men. We report 48-week results from a phase 3 study evaluating switching to B/F/TAF, specifically in a globally distributed trial population of women. METHODS: In this multicenter, randomized, open-label, active-controlled, noninferiority trial (ClinicalTrials.gov NCT02652624), women living with HIV who were virologically suppressed (HIV-1 RNA levels <50 copies/mL) on a regimen containing either TAF or tenofovir disoproxil fumarate were randomly assigned (1:1) to switch to B/F/TAF (50/200/25 mg) or stay on baseline regimen (SBR) once daily for 48 weeks. Primary endpoint was proportion of participants with plasma HIV-1 RNA ≥50 copies/mL at week 48 (U.S. Food and Drug Administration snapshot algorithm); prespecified noninferiority margin was 4%. FINDINGS: We randomized 472 participants and treated 470 (234 B/F/TAF, 236 SBR). Switching to B/F/TAF was noninferior to SBR for the primary outcome, as 1.7% (4/234) vs 1.7% (4/236) had HIV-1 RNA ≥50 copies/mL at week 48 (difference 0.0%, 95.001% confidence interval: -2.9% to 2.9%). No individual receiving B/F/TAF developed treatment-emergent resistance. Both treatments were well-tolerated; no participant discontinued treatment because of an adverse event. INTERPRETATION: Fixed-dose combination B/F/TAF provides a safe and efficacious option for ongoing treatment of HIV in women. This study contributes important data on safety, tolerability, and outcomes of antiretroviral therapy among women living with HIV.

Trends in Pretreatment HIV-1 Drug Resistance in Antiretroviral Therapy-naive Adults in South Africa, 2000-2016: A Pooled Sequence Analysis.

BACKGROUND: South Africa has the largest public antiretroviral therapy (ART) programme in the world. We assessed temporal trends in pretreatment HIV-1 drug resistance (PDR) in ART-naïve adults from South Africa. METHODS: We included datasets from studies conducted between 2000 and 2016, with HIV-1 pol sequences from more than ten ART-naïve adults. We analysed sequences for the presence of 101 drug resistance mutations. We pooled sequences by sampling year and performed a sequence-level analysis using a generalized linear mixed model, including the dataset as a random effect. FINDINGS: We identified 38 datasets, and retrieved 6880 HIV-1 pol sequences for analysis. The pooled annual prevalence of PDR remained below 5% until 2009, then increased to a peak of 11·9% (95% confidence interval (CI) 9·2-15·0) in 2015. The pooled annual prevalence of non-nucleoside reverse-transcriptase inhibitor (NNRTI) PDR remained below 5% until 2011, then increased to 10.0% (95% CI 8.4-11.8) by 2014. Between 2000 and 2016, there was a 1.18-fold (95% CI 1.13-1.23) annual increase in NNRTI PDR (p < 0.001), and a 1.10-fold (95% CI 1.05-1.16) annual increase in nucleoside reverse-transcriptase inhibitor PDR (p = 0.001). INTERPRETATION: Increasing PDR in South Africa presents a threat to the efforts to end the HIV/AIDS epidemic. These findings support the recent decision to modify the standard first-line ART regimen, but also highlights the need for broader public health action to prevent the further emergence and transmission of drug-resistant HIV. SOURCE OF FUNDING: This research project was funded by the South African Medical Research Council (MRC) with funds from National Treasury under its Economic Competitiveness and Support Package. DISCLAIMER: The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of CDC.

Antibody Responses in HIV-Infected Patients With Advanced Immunosuppression and Asymptomatic Cryptococcal Antigenemia.

BACKGROUND: There are no host biomarkers of risk for HIV-associated cryptococcal meningitis (CM) except CD4+ T-cell deficiency. At present, serum cryptococcal antigen (CrAg) screening of those with CD4 <100 cells/µL is used to identify persons at risk for HIV-associated CM. We determined if plasma antibody profiles could discriminate CrAg+ from CrAg- patients. METHODS: We performed serological analyses of 237 HIV-infected asymptomatic Zimbabwean patients with CD4 <100 cells/µL; 125 CrAg- and CrAg+ but cerebrospinal fluid CrAg- by CrAg lateral flow assay. We measured plasma immunoglobulin M (IgM), immunoglobulin G (IgG) 1, and IgG2 concentrations by Luminex, and titers of Cryptococcus neoformans (Cn) glucuronoxylomannan (GXM) polysaccharide and naturally occurring Laminarin (natural Lam, a ß-(1-3)-glucan linked polysaccharide)-binding IgM and IgG by enzyme-linked immunosorbent assay. RESULTS: GXM-IgG, -IgM, and -IgG2 levels were significantly higher in CrAg+ patients, whereas natural Lam-IgM and Lam-IgG were higher in CrAg- patients before and after adjustment for age, sex, and CD4 T-cell count, despite overlap of values. To address this variability and better discriminate the groups, we used Akaike Information Criteria to select variables that independently predicted CrAg+ status and included them in a receiver operating characteristic curve to predict CrAg status. By inclusion of CD4, GXM-IgG, GXM-IgM, and Lam-IgG, -IgG2, and -IgM, this model had an 80.4% probability (95% confidence interval, 0.75-0.86) of predicting CrAg+ status. CONCLUSIONS: Statistical models that include multiple serological variables may improve the identification of patients at risk for CM and inform new directions in research on the complex role that antibodies may play in resistance and susceptibility to CM.

Superior Efficacy and Improved Renal and Bone Safety After Switching from a Tenofovir Disoproxil Fumarate- to a Tenofovir Alafenamide-Based Regimen Through 96 Weeks of Treatment.

We previously demonstrated superior efficacy and safety advantages in HIV-infected, virologically suppressed adults switched to a regimen containing tenofovir alafenamide (TAF) as compared with those remaining on a tenofovir disoproxil fumarate (TDF) regimen through week 48. We now report long-term data through week 96. In this randomized, active-controlled, multicenter, open-label, noninferiority trial (ClinicalTrials.gov No. NCT01815736), we randomized virologically suppressed (HIV-1 RNA <50 copies/ml) adults (2:1) to receive a once-daily, single-tablet regimen containing elvitegravir (EVG), cobicistat (COBI), emtricitabine (FTC), and TAF group or to continue one of four TDF-containing regimens (TDF group) for 96 weeks. We evaluated efficacy (HIV-1 RNA <50 copies/ml using the FDA snapshot algorithm) and prespecified bone and renal endpoints at week 96. We randomized and treated 1,436 participants in this study (TAF n = 959, TDF n = 477). At week 96, TAF was superior to TDF in virologic efficacy, with 93% on TAF and 89% on TDF having HIV-1 RNA <50 copies/ml (difference 3.7%, 95% confidence interval: 0.4%-7.0%). Improvements in hip and spine bone mineral density for those assigned to TAF versus TDF continued through week 96 (p < .001). Significant improvements in urine protein or albumin to creatinine ratios were also seen among those in the TAF group versus TDF through week 96 (p < .001). There were no cases of investigator-reported proximal renal tubulopathy in the TAF group as compared with one case in the TDF group. Switching to EVG/COBI/FTC/TAF (E/C/F/TAF) was associated with statistically significant efficacy and safety advantages over remaining on a standard-of-care TDF-based regimen.

AMBITION-cm: intermittent high dose AmBisome on a high dose fluconazole backbone for cryptococcal meningitis induction therapy in sub-Saharan Africa: study protocol for a randomized controlled trial.

BACKGROUND: Cryptococcal meningitis (CM) is a leading cause of mortality among HIV-infected individuals in Africa. Poor outcomes from conventional antifungal therapies, unavailability of flucytosine, and difficulties administering 14 days of amphotericin B are key drivers of this mortality. Novel treatment regimes are needed. This study examines whether short-course high-dose liposomal amphotericin B (AmBisome), given with high dose fluconazole, is non-inferior (in terms of microbiological and clinical endpoints) to standard-dose 14-day courses of AmBisome plus high dose fluconazole for treatment of HIV-associated CM. METHODOLOGY/DESIGN: This is an adaptive open-label phase II/III randomised non-inferiority trial comparing alternative short course AmBisome regimens. Step 1 (phase II) will compare four treatment arms in 160 adult patients (≥ 18 years old) with a first episode of HIV-associated CM, using early fungicidal activity (EFA) as the primary outcome: 1) AmBisome 10 mg/kg day one (single dose); 2) AmBisome 10 mg/kg day one and AmBisome 5 mg/kg day three (two doses); 3) AmBisome 10 mg/kg day one, and AmBisome 5 mg/kg days three and seven (three doses); and 4) AmBisome 3 mg/kg/d for 14 days (control); all given with fluconazole 1200 mg daily for 14 days. STEP 2 (phase III) will enrol 300 participants and compare two treatment arms using all-cause mortality within 70 days as the primary outcome: 1) the shortest course AmBisome regimen found to be non-inferior in terms of EFA to the 14-day control arm in STEP 1, and 2) AmBisome 3 mg/kg/d for 14 days (control), both given with fluconazole 1200 mg daily for 14 days. STEP 2 analysis will include all patients from STEP 1 and STEP 2 taking the STEP 2 regimens. All patients will be followed for ten weeks, and mortality and safety data recorded. All patients will receive consolidation therapy with fluconazole 400-800 mg daily and ART in accordance with local guidelines. The primary analysis (for both STEP 1 and STEP 2) will be intention-to-treat. TRIAL REGISTRATION: ISRCTN10248064. Date of Registration: 22 January 2014.

'I was thinking too much': experiences of HIV-positive adults with common mental disorders and poor adherence to antiretroviral therapy in Zimbabwe.

OBJECTIVE: To document the lived experiences of people with both poor mental health and suboptimal adherence to antiretroviral therapy in high HIV prevalence settings. METHODS: In-depth qualitative interviews were conducted with 47 (female = 31) HIV-positive adults who scored above the cut-point on a locally validated scale for common mental disorders (CMDs). Purposive sampling was used to recruit participants with evidence of poor adherence. Six additional key informant interviews (female = 6) were conducted with healthcare workers. Data were collected and analysed inductively by an interdisciplinary coding team. RESULTS: The major challenges faced by participants were stressors (poverty, stigma, marital problems) and symptoms of CMDs ('thinking too much', changes to appetite and sleep, 'burdened heart' and low energy levels). Thinking too much, which appears closely related to rumination, was the symptom with the greatest negative impact on adherence to antiretroviral therapy among HIV-positive adults with CMDs. In turn, thinking too much was commonly triggered by the stressors faced by people living with HIV/AIDS, especially poverty. Finally, participants desired private counselling, access to income-generating activities and family engagement in mental health care. CONCLUSIONS: Better understanding of the local expression of mental disorders and of underlying stressors can inform the development of culturally sensitive interventions to reduce CMDs and poor adherence to antiretroviral therapy.

Setting the research agenda in a resource-limited setting--viewpoint.

The phenomenon of disproportionately large allocations of global health research resources to relatively limited components of the global health burden is widely acknowledged. Factors contributing to this are explored. The development of a national or regional research agenda is a critical step toward attempting to redress this imbalance. Key areas to be considered are a broad vision, dialogue, and commitment from those stakeholders comprising the "health research triangle": national policy makers and decision makers, key personnel in both health research and health care, and community representatives. The interdependent roles of human, material, and community resources are further examined.

Reciprocal recognition of an HLA-Cw4-restricted HIV-1 gp120 epitope by CD8+ T cells and NK cells.

OBJECTIVES: The HIV-1 Nef protein selectively downregulates human leukocyte antigen (HLA)-A and HLA-B but not HLA-C molecules on the surface of infected cells. This allows HIV-infected cells to evade recognition by most cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. We investigated the recognition of an HLA-Cw4-restricted HIV-1 gp120 epitope SFNCGGEFF (SF9) and its variant SFNCGGEFL (SL9) by T cells and NK receptors. DESIGN AND METHOD: Recognition of HIV-1 gp120 peptides (SF9 and SL9) by T-cell clones was measured by staining with HLA-Cw4-peptide tetrameric complexes and cytolytic assays using target cell pulsed with either peptides. KIR2DL1 binding to these two peptides was measured using surface plasmon resonance and tetramer staining of an NK cell line. RESULT: : CTLs could recognize SF9 better than the variant SL9, as shown by both tetramer staining and cytolytic assays. Intriguingly, an HLA-Cw4 tetramer folded with the 'escape' variant SL9 could bind to KIR2DL1 on NK cell lines with higher affinity than HLA-Cw4-SF9. The binding of KIR2DL1 to its ligand results in inhibition of NK cell function. Our results indicate that the HIV-1 gp120 variant peptide SL9 could potentially escape both from NK cell and CTL recognition by increasing its affinity for KIR2DL1 binding. CONCLUSION: These data suggest that HIV-1 can acquire mutations that are capable of escaping from both CTL and NK cell recognition, a phenomenon we have termed 'double escape'.