Understanding the determinants of CD8+ T cell immunodominance in acute HIV infection

CD8+ T cells detect and clear virus-infected cells. During human immunodeficiency virus-1 (HIV-1) infection, different HIV-specific CD8+ T cell populations are expanded, each targeting a discreet epitope. These different HIV-specific CD8+ T cell populations do not arise equally, and instead establish a hierarchy (immunodominance) based on strength of T cell response to a given viral epitope. Our previous work has shown that relative immunodominance is a major determinant of the rate at which HIV can mutate to escape T cell immune pressure. The precise mechanism of how the first CD8+ T cell response to HIV is generated, and which factors determine T cell dominance is unclear. To investigate determinants of T cell immunodominance in acute HIV-1 infection (~45 days following infection), we determined all primary HIV-1 specific CD8+ T cell responses in 10 individuals in the RV217 early HIV cohort (ECHO). T cell responses were mapped against the unique infecting HIV virus/es in each individual using IFN-γ ELISpot. Across participants, the dominant T cell response mostly targeted variable regions of the HIV-1 genome. We detected a wide (4–13 epitopes) breadth of T cell response across our cohort that was independent of HLA haplotype, with all HIV-1 proteins targeted and different rates of virus escape observed. Ongoing studies are focusing on better understanding how factors, such as T cell receptor repertoire, avidity, antigen presentation and function contribute to T cell immunodominance, which in turn will inform HIV-1 vaccine design.

Comparison of Antibody Responses Induced by RV144, VAX003, and VAX004 Vaccination Regimens

The RV144 prime-boost regimen demonstrated efficacy against HIV acquisition while VAX003 and VAX004 did not. Although these trials differed by risk groups, immunization regimens, and immunogens, antibody responses may have contributed to the differences observed in vaccine efficacy. We assessed HIV-specific IgG, both total and subclass, and IgA binding to HIV envelope (Env): gp120 proteins and Cyclic V2 (CycV2) and CycV3 peptides and gp70 V1 V2 scaffolds in these 3 HIV vaccine trials. After two protein immunizations, IgG responses to 92TH023 gp120 (contained in ALVAC-HIV vaccine) were significantly higher in RV144 but responses to other Env were higher in the VAX trials lacking ALVAC-HIV. IgG responses declined significantly between vaccinations. All trials induced antibodies to gp70 V1 V2 but VAX004 responses to 92TH023 gp70 V1 V2 were weak. All CycV2 responses were undetectable in VAX004 while 92TH023 gp70 V1 V2 was detected in both RV144 and VAX003 but MN CycV2 was detected only in VAX003. Multiple protein vaccinations in VAX trials did not improve magnitude or durability of V1 V2 and CycV2 antibodies. Herpes simplex virus glycoprotein D (gD) peptide at the N terminus of AIDSVAX^® B/E and B/B gp120 proteins induced antibodies in all trials, although significantly higher in VAX trials. gD peptide induced IgA, IgG1, IgG2, and IgG3 but not IgG4. Multiple protein vaccinations decreased IgG3 and increased IgG4 changing subclass contribution to total IgG. Although confounded by different modes of HIV transmission, higher Env-specific IgA and IgG4 binding antibodies induced in the VAX trials compared to RV144 raises the hypothesis that these differences may have contributed to different vaccine efficacy results.

Antibody responses induced to the C1 region of HIV-1 gp120 in acute HIV-1 infection and after vaccination

Based on the analysis of secondary immune correlates, the RV144 phase III trial demonstrated a reduced risk of infection in vaccine recipients with high levels of ADCC activity and low HIV-1 Env specific plasma IgA antibodies (Abs). Ab responses to the HIV-1 Env constant 1 (C1) region constituted the dominant ADCC Ab response. To further explore the binding Ab profiles and determine differences in the Ab responses to the C1 region (100 amino acids) induced by vaccine versus natural HIV-1 infection, plasma samples from an early acute HIV-1 infection Thai cohort (RV217) and a phase II clinical trial, RV135 (ALVAC prime and gp120 SF2/CM235 boost adjuvanted with MF59) were evaluated by Biacore. Based on the sequencing data from 16 RV217 individuals at 3 time points (week 1, weeks 4–6 and weeks 21–27 post infection), consensus 40-mer C1 peptides with 10-mer-overlapping amino acid sequences were initially screened for binding responses in RV217 and RV135 plasma samples. This was then followed with 16-mer peptides with 8-mer overlapping amino acid sequences to match the viral sequences in individual RV217 patients at these 3 time points. Vaccinees (RV135) induced Ab responses that recognized linear C1 peptides spanning amino acids 31-46, 55-70, 61-76, 77-92, and 85-100, whereas HIV-1 infected individuals (RV217) recognized linear C1 peptides spanning amino acids 1-16, 55-70, and 77-92. Future experiments will examine the functional role of these C1-specific Abs, in particular ADCC activity.

HIV-1 Genetic Diversity Among Incident Infections in Mbeya, Tanzania

In preparation for vaccine trials, HIV-1 genetic diversity was surveyed between 2002 and 2006 through the Cohort Development study in the form of a retrospective and prospective observational study in and around the town of Mbeya in Tanzania's Southwest Highlands. This study describes the molecular epidemiology of HIV-1 strains obtained from 97 out of 106 incident HIV-1 infections identified in three subpopulations of participants (one rural, two urban) from the Mbeya area. Near full-genome or half-genome sequencing showed a subtype distribution of 40% C, 17% A1, 1% D, and 42% inter-subtype recombinants. Compared to viral subtyping results previously obtained from the retrospective phase of this study, the overall proportion of incident viral strains did not change greatly during the study course, suggesting maturity of the epidemic. A comparison to a current Phase I-II vaccine being tested in Africa shows ∼17% amino acid sequence difference between the gp120 of the vaccine and subtype C incident strains. Phylogenetic and recombinant breakpoint analysis of the incident strains revealed the emergence of CRF41_CD and many unique recombinants, as well as the presence of six local transmission networks most of which were confined to the rural subpopulation. In the context of vaccine cohort selection, these results suggest distinct infection transmission dynamics within these three geographically close subpopulations. The diversity and genetic sequences of the HIV-1 strains obtained during this study will greatly contribute to the planning, immunogen selection, and analysis of vaccine-induced immune responses observed during HIV-1 vaccine trials in Tanzania and neighboring countries.

Prospecting for an HIV vaccine

Human immunodeficiency virus (HIV) sets several challenges for the development of a preventative HIV vaccine. Predictable, protective natural immunity against HIV does not occur and so unlike most other diseases for which vaccines exist, there are few guideposts from natural infection. Nonetheless, six vaccine efficacy trials have occurred. One in particular, the Thai trial called RV144, showed partial protective efficacy and potential ways ahead to a better vaccine approach. This coupled with other lessons from studies of acute infections as well as an increasingly complex knowledge of HIV-related vaccine immunology bring hope that a vaccine solution might be reached for this pervasive and deadly pandemic.

Boosting of HIV envelope CD4 binding site antibodies with long variable heavy third complementarity determining region in the randomized double blind RV305 HIV-1 vaccine trial

The canary pox vector and gp120 vaccine (ALVAC-HIV and AIDSVAX B/E gp120) in the RV144 HIV-1 vaccine trial conferred an estimated 31% vaccine efficacy. Although the vaccine Env AE.A244 gp120 is antigenic for the unmutated common ancestor of V1V2 broadly neutralizing antibody (bnAbs), no plasma bnAb activity was induced. The RV305 (NCT01435135) HIV-1 clinical trial was a placebo-controlled randomized double-blinded study that assessed the safety and efficacy of vaccine boosting on B cell repertoires. HIV-1-uninfected RV144 vaccine recipients were reimmunized 6–8 years later with AIDSVAX B/E gp120 alone, ALVAC-HIV alone, or a combination of ALVAC-HIV and AIDSVAX B/E gp120 in the RV305 trial. Env-specific post-RV144 and RV305 boost memory B cell V_H mutation frequencies increased from 2.9% post-RV144 to 6.7% post-RV305. The vaccine was well tolerated with no adverse events reports. While post-boost plasma did not have bnAb activity, the vaccine boosts expanded a pool of envelope CD4 binding site (bs)-reactive memory B cells with long third heavy chain complementarity determining regions (HCDR3) whose germline precursors and affinity matured B cell clonal lineage members neutralized the HIV-1 CRF01 AE tier 2 (difficult to neutralize) primary isolate, CNE8. Electron microscopy of two of these antibodies bound with near-native gp140 trimers showed that they recognized an open conformation of the Env trimer. Although late boosting of RV144 vaccinees expanded a novel pool of neutralizing B cell clonal lineages, we hypothesize that boosts with stably closed trimers would be necessary to elicit antibodies with greater breadth of tier 2 HIV-1 strains.

Trial Registration: ClinicalTrials.gov NCT01435135

Developing a successful HIV-1 vaccine remains a high global health priority. Several HIV-1 vaccine trials have been performed with only the RV144 vaccine trial showing vaccine efficacy, albeit modest. No broadly neutralizing antibody activity was identified in RV144 and inducing sterilizing immunity against a complex pathogen like HIV-1 remains a major challenge. Here we characterize the B cell responses after RV144 vaccine-recipients received two additional boosts severals years after the conclusion of the RV144 vaccine trial. Delayed and repetitive boosting of RV144 vaccine-recipients was capable of increasing somatic hypermutation of the Env-reactive antibodies and expanding subdominant pools of neutralizing B cell clonal lineages. These data are pertinent to HIV-1 vaccine-regimen design.

Prospects for a Zika Virus Vaccine

A recent unprecedented outbreak of Zika virus (ZIKV) in the Americas has been associated with microcephaly and other congenital malformations in infants as well as Guillain-Barre syndrome in adults. The development of a safe and effective ZIKV vaccine is therefore an urgent global health priority. Promising data from preclinical vaccine studies in mice and monkeys suggest that an effective vaccine will likely be possible, but important scientific challenges remain. Here we review the current state of ZIKV vaccine development. We discuss different vaccination strategies and we highlight challenges facing clinical evaluation of ZIKV vaccine candidates.

A Recombinant Vesicular Stomatitis Virus Ebola Vaccine

BACKGROUND

The worst Ebola virus disease (EVD) outbreak in history has resulted in more than 28,000 cases and 11,000 deaths. We present the final results of two phase 1 trials of an attenuated, replication-competent, recombinant vesicular stomatitis virus (rVSV)-based vaccine candidate designed to prevent EVD.

METHODS

We conducted two phase 1, placebo-controlled, double-blind, dose-escalation trials of an rVSV-based vaccine candidate expressing the glycoprotein of a Zaire strain of Ebola virus (ZEBOV). A total of 39 adults at each site (78 participants in all) were consecutively enrolled into groups of 13. At each site, volunteers received one of three doses of the rVSV-ZEBOV vaccine (3 million plaque-forming units [PFU], 20 million PFU, or 100 million PFU) or placebo. Volunteers at one of the sites received a second dose at day 28. Safety and immunogenicity were assessed.

RESULTS

The most common adverse events were injection-site pain, fatigue, myalgia, and headache. Transient rVSV viremia was noted in all the vaccine recipients after dose 1. The rates of adverse events and viremia were lower after the second dose than after the first dose. By day 28, all the vaccine recipients had seroconversion as assessed by an enzyme-linked immunosorbent assay (ELISA) against the glycoprotein of the ZEBOV-Kikwit strain. At day 28, geometric mean titers of antibodies against ZEBOV glycoprotein were higher in the groups that received 20 million PFU or 100 million PFU than in the group that received 3 million PFU, as assessed by ELISA and by pseudovirion neutralization assay. A second dose at 28 days after dose 1 significantly increased antibody titers at day 56, but the effect was diminished at 6 months.

CONCLUSIONS

This Ebola vaccine candidate elicited anti-Ebola antibody responses. After vaccination, rVSV viremia occurred frequently but was transient. These results support further evaluation of the vaccine dose of 20 million PFU for preexposure prophylaxis and suggest that a second dose may boost antibody responses. (Funded by the National Institutes of Health and others; rVSV∆G-ZEBOV-GP ClinicalTrials.gov numbers, NCT02269423 and NCT02280408 .).

Tissue memory B cell repertoire analysis after ALVAC/AIDSVAX B/E gp120 immunization of rhesus macaques

The ALVAC prime/ALVAC + AIDSVAX B/E boost RV144 vaccine trial induced an estimated 31% efficacy in a low-risk cohort where HIV‑1 exposures were likely at mucosal surfaces. An immune correlates study demonstrated that antibodies targeting the V2 region and in a secondary analysis antibody-dependent cellular cytotoxicity (ADCC), in the presence of low envelope-specific (Env-specific) IgA, correlated with decreased risk of infection. Thus, understanding the B cell repertoires induced by this vaccine in systemic and mucosal compartments are key to understanding the potential protective mechanisms of this vaccine regimen. We immunized rhesus macaques with the ALVAC/AIDSVAX B/E gp120 vaccine regimen given in RV144, and then gave a boost 6 months later, after which the animals were necropsied. We isolated systemic and intestinal vaccine Env-specific memory B cells. Whereas Env-specific B cell clonal lineages were shared between spleen, draining inguinal, anterior pelvic, posterior pelvic, and periaortic lymph nodes, members of Env‑specific B cell clonal lineages were absent in the terminal ileum. Env‑specific antibodies were detectable in rectal fluids, suggesting that IgG antibodies present at mucosal sites were likely systemically produced and transported to intestinal mucosal sites.

Clinical indicators associated with HIV acquisition in the United States Air Force

Mandatory HIV screening of United States Air Force (USAF) personnel every two years effectively identifies incident cases, however testing frequency limits the ability to detect early HIV infection. Identifying clinical indicators of HIV in the USAF population is necessary to develop a supplemental provider-based targeted testing strategy. We conducted a matched case-control study of male active duty USAF personnel with a new HIV diagnosis (n = 452) between 1996 and 2011 matched to five randomly selected controls (n = 2176). The relationship between clinical diagnoses, determined by ICD-9 codes, and HIV infection was assessed using conditional logistic regression. In unadjusted analyses of ICD-9 codes ever and within the last two years before HIV diagnosis, the conditional odds of HIV infection were greater in those with clinical signs and symptoms of HIV (cOR 5.05, 95% CI 4.00-6.39), mental health diagnoses (cOR 2.61, 95% CI 1.86-3.67), and STI diagnoses (cOR 2.33, 95% CI 1.50-3.60). Compared to those with ≤10 medical encounters in the two years prior to HIV diagnosis, individuals with 11-35 medical encounters (cOR 2.19, 95% CI 1.73-2.79) and >35 medical encounters (cOR 4.15, 95% CI 2.69-6.39) had a higher odds of HIV acquisition. In multivariate analyses, clinical signs and symptoms of HIV within the last two years of HIV diagnosis (cOR 4.10, 95% CI 3.22-5.22) and ever having a mental health diagnosis (cOR 1.97, 95% CI 1.44-2.70) remained significant (p < .01). Clinical encounters, particularly those featuring clinical signs and symptoms of HIV or a history of mental health complaints, provide an opportunity for targeted testing as a supplement to mandated testing at two-year intervals. Provider education to increase HIV testing in persons at risk would enhance early HIV diagnosis and potentially reduce forward transmission in the USAF population.

Persistent, Albeit Reduced, Chronic Inflammation in Persons Starting Antiretroviral Therapy in Acute HIV Infection

BACKGROUND

 Serious non-AIDS events cause substantial disease and death despite human immunodeficiency virus (HIV) suppression with antiretroviral therapy (ART). Biomarkers of inflammation, coagulation cascade activation, and fibrosis predict these end-organ events. We aimed to determine whether ART initiation during acute HIV infection would attenuate changes in these biomarker levels.

METHODS

 Plasma samples were obtained from participants starting ART during acute or chronic HIV infection and from HIV-uninfected participants from Bangkok, Thailand. Biomarkers of inflammation (C-reactive protein [CRP], interleukin 6, soluble interleukin 6 receptor [sIL-6R], soluble gp130, tumor necrosis factor [TNF]), enterocyte turnover (intestinal fatty acid binding protein [I-FABP]), lipopolysaccharide-induced monocyte activation (soluble CD14 [sCD14]), coagulation cascade activation [D-dimer], and fibrosis (hyaluronic acid [HA]) were measured at baseline and through 96 weeks of ART.

RESULTS

 CRP, TNF, sIL-6R, I-FABP, sCD14, D-dimer, and HA levels were elevated in acute HIV infection. Early ART was associated with increased I-FABP levels but normalization of TNF, sIL-6R, and D-dimer levels. CRP, sCD14, and HA levels decreased during ART but remained elevated compared with HIV-uninfected participants. Higher sCD14, CRP, and D-dimer levels were associated with higher peripheral blood mononuclear cell and gut integrated HIV DNA levels. Decreases in sCD14 and CRP levels were correlated with increases in CD4 T-cell counts.

CONCLUSIONS

 ART initiated in early acute HIV infection was associated with normalization of the coagulation cascade and several systemic inflammatory biomarkers, but the acute-phase response, enterocyte turnover, monocyte activation, and fibrosis biomarkers remained elevated. Additional interventions to attenuate inflammation may be needed to optimize clinical outcomes in persons with HIV infection.

Protective efficacy of multiple vaccine platforms against Zika virus challenge in rhesus monkeys

Zika virus (ZIKV) is responsible for a major ongoing epidemic in the Americas and has been causally associated with fetal microcephaly. The development of a safe and effective ZIKV vaccine is therefore an urgent global health priority. Here we demonstrate that three different vaccine platforms protect against ZIKV challenge in rhesus monkeys. A purified inactivated virus vaccine induced ZIKV-specific neutralizing antibodies and completely protected monkeys against ZIKV strains from both Brazil and Puerto Rico. Purified immunoglobulin from vaccinated monkeys also conferred passive protection in adoptive transfer studies. A plasmid DNA vaccine and a single-shot recombinant rhesus adenovirus serotype 52 vector vaccine, both expressing ZIKV premembrane and envelope, also elicited neutralizing antibodies and completely protected monkeys against ZIKV challenge. These data support the rapid clinical development of ZIKV vaccines for humans.

Missed opportunity to screen and diagnose PTSD and depression among deploying shipboard US military personnel

BACKGROUND

Depression and post-traumatic stress disorder (PTSD) are significant risks for suicide and other adverse events among US military personnel, but prevalence data among ship-assigned personnel at the onset of deployment are unknown.

AIMS

To determine the prevalence of shipboard personnel who screen positive for PTSD and/or major depressive disorder (MDD) at the onset of deployment, and also those who reported these diagnoses made by a physician or healthcare professional in the year prior to deployment.

METHOD

Active-duty ship-assigned personnel (N = 2078) completed anonymous assessments at the beginning of deployment. Depression was measured using the Center for Epidemiologic Studies Depression Scale (CES-D; score of ≥22), and PTSD was assessed using the PTSD Checklist-Civilian Version (PCL-C; both score and symptom criteria were used).

RESULTS

In total, 7.3% (n = 151 of 2076) screened positive for PTSD and 22% (n = 461 of 2078) for MDD at deployment onset. Only 6% and 15% of those who screened positive for PTSD or MDD, respectively, had been diagnosed by a healthcare professional in the past year.

CONCLUSIONS

Missed opportunities for mental healthcare among screen-positive shipboard personnel reduce the benefits associated with early identification and linkage to care. Improved methods of mental health screening that promote early recognition and referral to care may mitigate psychiatric events in theatre.

DECLARATION OF INTEREST

This work was performed as part of the official duties of the authors as military service members or employees of the US Government.

COPYRIGHT AND USAGE

This work was prepared by military service members or employees of the US Government as part of their official duties. As such, copyright protection is not available for this work (Title 17, USC, §105).

Zanotto PM, Iampietro MJ, Badamchi-Zadeh A, Boyd M, Ng’ang’a D, Kirilova M, Nityanandam R, Mercado NB, Li Z, Moseley ET, Bricault CA, Borducchi EN, Giglio PB, Jetton D, Neubauer G, Nkolola JP, Maxfield LF, De La Barrera RA, Jarman RG, Eckels KH, Michael NL, Thomas SJ, Barouch DH. Vaccine protection against Zika virus from Brazil

Zika virus (ZIKV) is a flavivirus that is responsible for the current epidemic in Brazil and the Americas. ZIKV has been causally associated with fetal microcephaly, intrauterine growth restriction, and other birth defects in both humans and mice. The rapid development of a safe and effective ZIKV vaccine is a global health priority, but very little is currently known about ZIKV immunology and mechanisms of immune protection. Here we show that a single immunization with a plasmid DNA vaccine or a purified inactivated virus vaccine provides complete protection in susceptible mice against challenge with a strain of ZIKV involved in the outbreak in northeast Brazil. This ZIKV strain has recently been shown to cross the placenta and to induce fetal microcephaly and other congenital malformations in mice. We produced DNA vaccines expressing ZIKV pre-membrane and envelope (prM-Env), as well as a series of deletion mutants. The prM-Env DNA vaccine, but not the deletion mutants, afforded complete protection against ZIKV, as measured by absence of detectable viraemia following challenge, and protective efficacy correlated with Env-specific antibody titers. Adoptive transfer of purified IgG from vaccinated mice conferred passive protection, and depletion of CD4 and CD8 T lymphocytes in vaccinated mice did not abrogate this protection. These data demonstrate that protection against ZIKV challenge can be achieved by single-shot subunit and inactivated virus vaccines in mice and that Env-specific antibody titers represent key immunologic correlates of protection. Our findings suggest that the development of a ZIKV vaccine for humans is likely to be achievable.

Pre-deployment Alcohol Misuse Among Shipboard Active-Duty U.S. Military Personnel

INTRODUCTION

The burden of alcohol misuse is unknown among shipboard U.S. Navy and Marine Corps military personnel immediately prior to deployment and may be elevated.

METHODS

Anonymous survey data on hazardous, dependent, and binge alcohol misuse and involuntary drug consumption were collected during 2012-2014 among shipboard personnel within approximately 2 weeks of deployment. Using the Alcohol Use Disorders Identification Test Consumption (AUDIT-C), hazardous alcohol misuse was defined using two cut-point scoring criteria: (1) ≥3 for women and ≥4 for men; and (2) ≥4 for women and ≥5 for men; binge drinking as ≥4 drinks for women and ≥5 drinks for men on a typical day in past 30 days; and dependent alcohol misuse as an AUDIT-C score of ≥8. Demographic- and sex-stratified self-reported alcohol misuse prevalence was reported for analysis conducted during 2014-2015.

RESULTS

Among 2,351 male and female shipboard personnel, 39%-54% screened positive for hazardous, 27% for binge, and 15% for dependent alcohol use. Seven percent reported involuntary drug consumption history. A larger proportion of those aged 17-20 years screened positive for dependent alcohol use compared with the overall study population prevalence.

CONCLUSIONS

A large proportion of shipboard personnel screened positive for hazardous and dependent alcohol use (18% among those aged <21 years) at deployment onset. These data can inform interventions targeting shipboard personnel engaging in hazardous use before progression to dependent use and enable early identification and care for dependent users. Future studies should include more comprehensive assessment of factors associated with involuntary drug consumption.

Knowledge, attitudes, and beliefs about HIV pre-exposure prophylaxis among US Air Force Health Care Providers

Providers are central to effective implementation of HIV pre-exposure prophylaxis (PrEP). Primary care providers (PCP) and infectious disease physicians (ID) in the US Air Force (USAF) participated in a cross-sectional survey regarding knowledge, attitudes, and beliefs toward HIV PrEP. Characteristics associated with PrEP knowledge were assessed in univariate and multivariate analyses.Among 403 (40% of 1015 providers) participants, 9% (PCP 383, ID 20) ever prescribed PrEP. In univariate analysis, years in practice, number of HIV-infected patients treated in the past 12 months, past prescription of antiretrovirals for HIV prevention, frequency of prescribing PrEP in the past 12 months, and ever being questioned by a patient about PrEP were associated with PrEP knowledge (P < 0.05). In multivariate analysis, providers who had ever prescribed antiretrovirals to prevent HIV (AOR: 2.37, 95% CI: 1.27-4.42) had greater odds of high PrEP knowledge. Despite concerns about medication side effects (overall 67%: PCP 68%, ID 85%) and prescribing PrEP without clear evidence (overall 60%: PCP 65%, ID 62%), 64% (PCP 65%, ID 85%) of participants indicated PrEP should be offered in the Military Health System and 68% (PCP 70%, ID 100%) disagreed with the statement that their patient population was not at risk for HIV infection.Successful PrEP implementation in the USAF will require continued education and training of primary care providers to improve knowledge and mitigate concerns about PrEP.

Significant contribution of subtype G to HIV-1 genetic complexity in Nigeria identified by a newly developed subtyping assay specific for subtype G and CRF02_AG

While abundant sequence information is available from human immunodeficiency virus type 1 (HIV-1) subtypes A, B, C and CRF01_AE for HIV-1 vaccine design, sequences from West Africa are less represented. We sought to augment our understanding of HIV-1 variants circulating in 6 Nigerian cities as a step to subsequent HIV-1 vaccine development.The G/CRF02_AG multi-region hybridization assay (MHA) was developed to differentiate subtype G, CRF02_AG and their recombinants from other subtypes based on 7 HIV-1 segments. Plasma from 224 HIV-1 infected volunteers enrolled in a cohort examining HIV-1 prevalence, risk factor, and subtype from Makurdi (30), Abuja (18), Enugu (11), Kaduna (12), Tafa (95), and Ojo/Lagos (58) was analyzed using MHA. HIV-1 genomes from 42 samples were sequenced to validate the MHA and fully explore the recombinant structure of G and CRF02_AG variants.The sensitivity and specificity of MHA varied between 73-100% and 90-100%, respectively. The subtype distribution as identified by MHA among 224 samples revealed 38% CRF02_AG, 28% G, and 26% G/CRF02_AG recombinants while 8% remained nontypeable strains. In envelope (env) gp120, 38.84% of the samples reacted to a G probe while 31.25% reacted to a CRF02 (subtype A) probe. Full genome characterization of 42 sequences revealed the complexity of Nigerian HIV-1 variants.CRF02_AG, subtype G, and their recombinants were the major circulating HIV-1 variants in 6 Nigerian cities. High proportions of samples reacted to a G probe in env gp120 confirms that subtype G infections are abundant and should be considered in strategies for global HIV-1 vaccine development.

Altered Memory Circulating T Follicular Helper-B Cell Interaction in Early Acute HIV Infection

The RV254 cohort of HIV-infected very early acute (4thG stage 1 and 2) (stage 1/2) and late acute (4thG stage 3) (stage 3) individuals was used to study T helper- B cell responses in acute HIV infection and the impact of early antiretroviral treatment (ART) on T and B cell function. To investigate this, the function of circulating T follicular helper cells (cTfh) from this cohort was examined, and cTfh and memory B cell populations were phenotyped. Impaired cTfh cell function was observed in individuals treated in stage 3 when compared to stage 1/2. The cTfh/B cell cocultures showed lower B cell survival and IgG secretion at stage 3 compared to stage 1/2. This coincided with lower IL-10 and increased RANTES and TNF-α suggesting a role for inflammation in altering cTfh and B cell responses. Elevated plasma viral load in stage 3 was found to correlate with decreased cTfh-mediated B cell IgG production indicating a role for increased viremia in cTfh impairment and dysfunctional humoral response. Phenotypic perturbations were also evident in the mature B cell compartment, most notably a decrease in resting memory B cells in stage 3 compared to stage 1/2, coinciding with higher viremia. Our coculture assay also suggested that intrinsic memory B cell defects could contribute to the impaired response despite at a lower level. Overall, cTfh-mediated B cell responses are significantly altered in stage 3 compared to stage 1/2, coinciding with increased inflammation and a reduction in memory B cells. These data suggest that early ART for acutely HIV infected individuals could prevent immune dysregulation while preserving cTfh function and B cell memory.

The HIV-specific T cell memory response diminishes rapidly even after the initiation of anti-retroviral treatment (ART), and there is no control of viral rebound if treatment is interrupted. Restoration or preservation of memory T cells or B cells with treatment, to allow for control of virus replication after ART is stopped, is therefore very important. CD4⁺ T cells, in particular T follicular helper (Tfh) cells, have a major role in mediating antiviral immunity by providing help to B cells, which is key to a strong and efficient anti-HIV antibody response. The unique RV254 cohort provided the best setting to analyze immune responses during very early acute HIV, as the study was able to enroll individuals that were infected for less than 2 weeks and initiated treatment approximately 1–2 days after recruitment. We aimed to study the capacity of memory circulating Tfh (cTfh) cells to promote B cell help in acute HIV infection, and found the interaction to be dysfunctional in the later stage compared to the very early stages, accompanied by increased levels of proinflammatory cytokines and a reduction in regulatory cytokines. High levels of plasma viremia correlated with low cTfh-mediated B cell antibody production in later stage acute individuals; and memory B cells were significantly decreased but could be restored with ART, compared to chronically infected individuals, who could not normalize this compartment compared to healthy individuals. Overall, we show that the cTfh- B cell interaction and B cell memory compartment is altered in late stage acute infection, mainly attributed to an increase in inflammation and skewing of the response away from helper to proinflammatory. Identifying individuals for treatment in the earliest stages of acute infection, prior to immune damage, could preserve cTfh function and the anti-HIV B cell response, therefore reducing the chances of viral rebound upon the cessation of ART.

Initiation of Antiretroviral Therapy During Acute HIV-1 Infection Leads to a High Rate of Nonreactive HIV Serology

BACKGROUND

Third- and fourth-generation immunoassays (IAs) are widely used in the diagnosis of human immunodeficiency virus (HIV) infection. Antiretroviral therapy (ART) during acute HIV infection (AHI) may impact HIV-specific antibodies, with failure to develop antibody or seroreversion. We report on the ability of diagnostic tests to detect HIV-specific antibodies in Thai participants initiating ART during AHI.

METHODS

Participants with detectable plasma HIV RNA but nonreactive HIV-specific immunoglobulin G, enrolled in an AHI study, were offered immediate initiation of ART. Participants were tested at initiation and at 12 and 24 weeks following treatment using standard second-, third-, and fourth-generation IAs and Western blot (WB).

RESULTS

Participants (N = 234) initiating ART at a median of 19 days (range, 1-62 days) from HIV exposure demonstrated different frequencies of reactivity prior to and following 24 weeks of ART depending on the IA. Third-generation IA nonreactivity prior to ART was 48%, which decreased to 4% following ART (P < .001). Fourth-generation IA nonreactivity was 18% prior to ART and 17% following ART (P = .720). Negative WB results were observed in 89% and 12% of participants prior to and following 24 weeks of ART, respectively (P < .001). Seroreversion to nonreactivity during ART was observed to at least one of the tests in 20% of participants, with fourth-generation IA demonstrating the highest frequency (11%) of seroreversion.

CONCLUSIONS

HIV-specific antibodies may fail to develop and, when detected, may decline when ART is initiated during AHI. Although fourth-generation IA was the most sensitive at detecting AHI prior to ART, third-generation IA was the most sensitive during treatment.

CLINICAL TRIALS REGISTRATION

NCT00796146 and NCT00796263.

Sequential Dysfunction and Progressive Depletion of Candida albicans-Specific CD4 T Cell Response in HIV-1 Infection

Loss of immune control over opportunistic infections can occur at different stages of HIV-1 (HIV) disease, among which mucosal candidiasis caused by the fungal pathogen Candida albicans (C. albicans) is one of the early and common manifestations in HIV-infected human subjects. The underlying immunological basis is not well defined. We have previously shown that compared to cytomegalovirus (CMV)-specific CD4 cells, C. albicans-specific CD4 T cells are highly permissive to HIV in vitro. Here, based on an antiretroviral treatment (ART) naïve HIV infection cohort (RV21), we investigated longitudinally the impact of HIV on C. albicans- and CMV-specific CD4 T-cell immunity in vivo. We found a sequential dysfunction and preferential depletion for C. albicans-specific CD4 T cell response during progressive HIV infection. Compared to Th1 (IFN-γ, MIP-1β) functional subsets, the Th17 functional subsets (IL-17, IL-22) of C. albicans-specific CD4 T cells were more permissive to HIV in vitro and impaired earlier in HIV-infected subjects. Infection history analysis showed that C. albicans-specific CD4 T cells were more susceptible to HIV in vivo, harboring modestly but significantly higher levels of HIV DNA, than CMV-specific CD4 T cells. Longitudinal analysis of HIV-infected individuals with ongoing CD4 depletion demonstrated that C. albicans-specific CD4 T-cell response was preferentially and progressively depleted. Taken together, these data suggest a potential mechanism for earlier loss of immune control over mucosal candidiasis in HIV-infected patients and provide new insights into pathogen-specific immune failure in AIDS pathogenesis.

HIV infection is closely associated with enhanced host susceptibility to various opportunistic infections (OIs), among which mucosal candidiasis caused by the fungal pathogen Candida albicans (C. albicans) is an early and common manifestation. Even in the era of effective ART, mucosal candidiasis is still a clinically relevant presentation in HIV-infected patients. The underlying mechanisms are not well defined. CD4-mediated immunity is the major host defense mechanism against C. albicans. We here investigated a group of ART naïve, HIV-infected human subjects and examined longitudinally the impact of HIV on C. albicans-specific CD4 T-cell immunity as compared to CD4 T-cell immunity specific for CMV, another opportunistic pathogen that usually does not cause active disease in early HIV infection. We found that C. albicans-specific CD4 T cells were more susceptible to HIV in vivo and were preferentially depleted in progressive HIV-infected individuals as compared to CMV-specific CD4 T cells. Of importance, we also found that in these HIV-infected subjects C. albicans-specific CD4 T cell response manifested a sequential dysfunction with earlier impairment of Th17, but not Th1, functions. Our study suggests an immunological basis that helps explain the earlier and more common onsets of mucosal candidiasis in progressive HIV-infected patients.

Prospective Study of Acute HIV-1 Infection in Adults in East Africa and Thailand

BACKGROUND

Acute human immunodeficiency virus type 1 (HIV-1) infection is a major contributor to transmission of HIV-1. An understanding of acute HIV-1 infection may be important in the development of treatment strategies to eradicate HIV-1 or achieve a functional cure.

METHODS

We performed twice-weekly qualitative plasma HIV-1 RNA nucleic acid testing in 2276 volunteers who were at high risk for HIV-1 infection. For participants in whom acute HIV-1 infection was detected, clinical observations, quantitative measurements of plasma HIV-1 RNA levels (to assess viremia) and HIV antibodies, and results of immunophenotyping of lymphocytes were obtained twice weekly.

RESULTS

Fifty of 112 volunteers with acute HIV-1 infection had two or more blood samples collected before HIV-1 antibodies were detected. The median peak viremia (6.7 log10 copies per milliliter) occurred 13 days after the first sample showed reactivity on nucleic acid testing. Reactivity on an enzyme immunoassay occurred at a median of 14 days. The nadir of viremia (4.3 log10 copies per milliliter) occurred at a median of 31 days and was nearly equivalent to the viral-load set point, the steady-state viremia that persists durably after resolution of acute viremia (median plasma HIV-1 RNA level, 4.4 log10 copies per milliliter). The peak viremia and downslope were correlated with the viral-load set point. Clinical manifestations of acute HIV-1 infection were most common just before and at the time of peak viremia. A median of one symptom of acute HIV-1 infection was recorded at a median of two study visits, and a median of one sign of acute HIV-1 infection was recorded at a median of three visits.

CONCLUSIONS

The viral-load set point occurred at a median of 31 days after the first detection of plasma viremia and correlated with peak viremia. Few symptoms and signs were observed during acute HIV-1 infection, and they were most common before peak viremia. (Funded by the Department of Defense and the National Institute of Allergy and Infectious Diseases.).

HLA class II genes modulate vaccine-induced antibody responses to affect HIV-1 acquisition

In the RV144 vaccine trial, two antibody responses were found to correlate with HIV-1 acquisition. Because human leukocyte antigen (HLA) class II-restricted CD4(+) T cells are involved in antibody production, we tested whether HLA class II genotypes affected HIV-1-specific antibody levels and HIV-1 acquisition in 760 individuals. Indeed, antibody responses correlated with acquisition only in the presence of single host HLA alleles. Envelope (Env)-specific immunoglobulin A (IgA) antibodies were associated with increased risk of acquisition specifically in individuals with DQB1*06. IgG antibody responses to Env amino acid positions 120 to 204 were higher and were associated with decreased risk of acquisition and increased vaccine efficacy only in the presence of DPB1*13. Screening IgG responses to overlapping peptides spanning Env 120-204 and viral sequence analysis of infected individuals defined differences in vaccine response that were associated with the presence of DPB1*13 and could be responsible for the protection observed. Overall, the underlying genetic findings indicate that HLA class II modulated the quantity, quality, and efficacy of antibody responses in the RV144 trial.

Safety and Immunogenicity of a Randomized Phase 1 Prime-Boost Trial With ALVAC-HIV (vCP205) and Oligomeric Glycoprotein 160 From HIV-1 Strains MN and LAI-2 Adjuvanted in Alum or Polyphosphazene

BACKGROUND

Prime-boost regimens comprising ALVAC-HIV (prime) and human immunodeficiency virus type 1 (HIV) Env (boost) induce HIV-specific neutralizing antibody and cell-mediated immune responses, but the impact of boost schedule and adjuvant requires further definition.

METHODS

A phase 1 trial was conducted. In part A (open label), 19 volunteers received oligomeric glycoprotein 160 from HIV strains MN and LAI-2 (ogp160 MN/LAI-2) with dose escalation (25, 50, 100 μg) and either polyphosphazene (pP) or alum adjuvant. In part B, 72 volunteers received either placebo (n=12) or recombinant canarypox virus expressing HIV antigens (ALVAC-HIV [vCP205]) with different doses and schedules of ogp160 MN/LAI-2 in pP or alum (n = 60).

RESULTS

The vaccines were safe and well tolerated, with no vaccine-related serious adverse events. Anti-gp70 V1V2 antibody responses were detected in 17 of 19 part A volunteers (89%) and 10%-100% of part B volunteers. Use of a peripheral blood mononuclear cell-based assay revealed that US-1 primary isolate neutralization was induced in 2 of 19 recipients of ogp160 protein alone (10.5%) and 5 of 49 prime-boost volunteers (10.2%). Among ogp160 recipients, those who received pP were more likely than those who received alum to have serum that neutralized tier 2 viruses (12% vs 0%; P = .015).

CONCLUSIONS

Administration of ogp160 with pP induces primary isolate tier 2 neutralizing antibody responses in a small percentage of volunteers, demonstrating proof of concept and underscoring the importance of further optimization of prime-boost strategies for HIV infection prevention.

CLINICAL TRIALS REGISTRATION

NCT00004579.

Immunology of protection from Ebola virus infection

A December 2014 meeting reviewed Ebola virus immunology relevant to vaccine development, including Ebola prevention, immunity, assay standardization, and regulatory considerations. Vaccinated humans appear to achieve immune responses comparable in magnitude with those associated with protection in nonhuman primates, suggesting that immunological data could be used to demonstrate vaccine efficacy.