Continued Follow-Up of Phambili Phase 2b Randomized HIV-1 Vaccine Trial Participants Supports Increased HIV-1 Acquisition among Vaccinated Men

Vaccine Strategies to Elicit Mucosal Immunity

Vaccines are essential tools to prevent infection and control transmission of infectious diseases that threaten public health. Most infectious agents enter their hosts across mucosal surfaces, which make up key first lines of host defense against pathogens. Mucosal immune responses play critical roles in host immune defense to provide durable and better recall responses. Substantial attention has been focused on developing effective mucosal vaccines to elicit robust localized and systemic immune responses by administration via mucosal routes. Mucosal vaccines that elicit effective immune responses yield protection superior to parenterally delivered vaccines. Beyond their valuable immunogenicity, mucosal vaccines can be less expensive and easier to administer without a need for injection materials and more highly trained personnel. However, developing effective mucosal vaccines faces many challenges, and much effort has been directed at their development. In this article, we review the history of mucosal vaccine development and present an overview of mucosal compartment biology and the roles that mucosal immunity plays in defending against infection, knowledge that has helped inform mucosal vaccine development. We explore new progress in mucosal vaccine design and optimization and novel approaches created to improve the efficacy and safety of mucosal vaccines.

Risk Factors Associated with HIV Acquisition in Males Participating in HIV Vaccine Efficacy Trials in South Africa

In South Africa, HIV acquisition risk has been studied less in people assigned male at birth. We studied the associations between risk behaviors, clinical features and HIV incidence amongst males in two South African HIV preventive vaccine efficacy trials. We used Cox proportional hazards models to test for associations between demographics, sexual behaviors, clinical variables and HIV acquisition among males followed in the HVTN 503 (n = 219) and HVTN 702 (n = 1611) trials. Most males reported no male sexual partners (99.09% in HVTN 503) or identified as heterosexual (88.08% in HVTN 702). Annual HIV incidence was 1.39% in HVTN 503 (95% CI 0.76-2.32%) and 1.33% in HVTN 702 (95% CI 0.80-2.07%). Increased HIV acquisition was significantly associated with anal sex (HR 6.32, 95% CI 3.44-11.62), transactional sex (HR 3.42, 95% CI 1.80-6.50), and non-heterosexual identity (HR 16.23, 95%CI 8.13-32.41) in univariate analyses and non-heterosexual identity (HR 14.99, 95% CI 4.99-45.04; p < 0.01) in multivariate analysis. It is appropriate that prevention efforts in South Africa, although focused on the severe epidemic in young women, also encompass key male populations, including men who have sex with men, but also men who engage in anal or transactional sex.

Use of Varied Screening Risk Criteria and HIV Incidence in Phase 1 and 2 HIV Vaccine Trials in South Africa

Many early phase HIV prevention studies define HIV risk-related eligibility criteria. We conducted a retrospective review of HIV Vaccine Trials Network (HVTN) Phase 1 and 2 HIV vaccine clinical trials completed in South Africa from 2003 to 2020, evaluating HIV incidence by protocol-defined risk criteria. Comparisons between groups controlled for age, gender and year of trial initiation. Across 12 trials, 1 did not specify risk criteria, and 11 specified various low risk criteria thematically categorized under sexual behaviors, clinical characteristics, and/or drug use behavior. Of the 11 trials, 6 used low sexual risk eligibility criteria standardized by the HVTN in 2009. Of the 1249 participants, median age 23.0 years, 66% were enrolled with the HVTN 2009 standardized low risk criteria, 15% using other sets of low risk criteria, and 19% using no risk criteria. Compared with the standardized low risk criteria group [2.3], HIV incidence per 100 person-years was significantly higher in the non-standardized low risk criteria group [5.0] and in the no risk criteria group [4.8]. In South Africa, cohorts with low HIV incidence can be identified primarily through sexual behavior and clinical characteristics.

The Failure of AIDS Vaccine Efficacy Trials: Where to Go from Here

The seven AIDS vaccine efficacy trials have yielded extremely disappointing results at great expense. Greater stringency is needed for government support of AIDS vaccine efficacy trials.

Strategies for HIV-1 vaccines that induce broadly neutralizing antibodies

After nearly four decades of research, a safe and effective HIV-1 vaccine remains elusive. There are many reasons why the development of a potent and durable HIV-1 vaccine is challenging, including the extraordinary genetic diversity of HIV-1 and its complex mechanisms of immune evasion. HIV-1 envelope glycoproteins are poorly recognized by the immune system, which means that potent broadly neutralizing antibodies (bnAbs) are only infrequently induced in the setting of HIV-1 infection or through vaccination. Thus, the biology of HIV-1-host interactions necessitates novel strategies for vaccine development to be designed to activate and expand rare bnAb-producing B cell lineages and to select for the acquisition of critical improbable bnAb mutations. Here we discuss strategies for the induction of potent and broad HIV-1 bnAbs and outline the steps that may be necessary for ultimate success.

The repeated setbacks of HIV vaccine development laid the groundwork for SARS-CoV-2 vaccines

The decades-long effort to produce a workable HIV vaccine has hardly been a waste of public and private resources. To the contrary, the scientific know-how acquired along the way has served as the critical foundation for the development of vaccines against the novel, pandemic SARS-CoV-2 virus. We retell the real-world story of HIV vaccine research – with all its false leads and missteps – in a way that sheds light on the current state of the art of antiviral vaccines. We find that HIV-related R&D had more than a general spillover effect. In fact, the repeated failures of phase 2 and 3 clinical trials of HIV vaccine candidates have served as a critical stimulus to the development of successful vaccine technologies today. We rebut the counterargument that HIV vaccine development has been no more than a blind alley, and that recently developed vaccines against COVID-19 are really descendants of successful vaccines against Ebola, MERS, and SARS. These successful vaccines likewise owe much to the vicissitudes of HIV vaccine development. We then discuss how the failures of HIV vaccine development have taught us how adapt SARS-CoV-2 vaccines to immune escape from emerging variants. Finally, we inquire whether recent advances in the development of vaccines against SARS-CoV-2 might in turn further the development of an HIV vaccine - what we describe as a reverse spillover effect.

Adenovirus-based vaccines - a platform for pandemic preparedness against emerging viral pathogens

Zoonotic viruses continually pose a pandemic threat. Infection of humans with viruses for which we typically have little or no prior immunity can result in epidemics with high morbidity and mortality. These epidemics can have public health and economic impact and can exacerbate civil unrest or political instability. Changes in human behavior in the past few decades—increased global travel, farming intensification, the exotic animal trade, and the impact of global warming on animal migratory patterns, habitats, and ecosystems—contribute to the increased frequency of cross-species transmission events. Investing in the pre-clinical advancement of vaccine candidates against diverse emerging viral threats is crucial for pandemic preparedness. Replication-defective adenoviral (Ad) vectors have demonstrated their utility as an outbreak-responsive vaccine platform during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Ad vectors are easy to engineer; are amenable to rapid, inexpensive manufacturing; are relatively safe and immunogenic in humans; and, importantly, do not require specialized cold-chain storage, making them an ideal platform for equitable global distribution or stockpiling. In this review, we discuss the progress in applying Ad-based vaccines against emerging viruses and summarize their global safety profile, as reflected by their widespread geographic use during the SARS-CoV-2 pandemic.

COVID-19 vaccines for low- and middle-income countries

The COVID-19 pandemic is the biggest threat to public health in a century. Through hard work and ingenuity, scientists have developed a number of safe and effective vaccines against COVID-19 disease. However, demand far outstrips supply and countries around the world are competing for available vaccines. This review describes how low- and middle-income countries access COVID-19 vaccines, what is being done to distribute vaccines fairly, as well as the challenges ahead.

An overview of current COVID-19 vaccine platforms

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) pandemic that emerged in December 2019 in Wuhan city, China. An effective vaccine is urgently needed to protect humans and to mitigate the economic and societal impacts of the pandemic. Despite standard vaccine development usually requiring an extensive process and taking several years to complete all clinical phases, there are currently 184 vaccine candidates in pre-clinical testing and another 88 vaccine candidates in clinical phases based on different vaccine platforms as of April 13, 2021. Moreover, three vaccine candidates have recently been granted an Emergency Use Authorization by the United States Food and Drug Administration (for Pfizer/BioNtech, Moderna mRNA vaccines, and Johnson and Johnson viral vector vaccine) and by the UK government (for University of Oxford/AstraZeneca viral vector vaccine). Here we aim to briefly address the current advances in reverse genetics system of SARS-CoV-2 and the use of this in development of SARS-CoV-2 vaccines. Additionally, we cover the essential points concerning the different platforms of current SARS-CoV-2 vaccine candidates and the advantages and drawbacks of these platforms. We also assess recommendations for controlling the COVID-19 pandemic and future pandemics using the benefits of genetic engineering technology to design effective vaccines against emerging and re-emerging viral diseases with zoonotic and/or pandemic potential.

Benign ethnic neutropenia in a South African population, and its association with HIV acquisition and adverse event reporting in an HIV vaccine clinical trial

Benign ethnic neutropenia (BEN) is defined as a neutrophil count of <1.5×10⁹ cells/L in healthy individuals and is more common in populations of certain ethnicities, e.g. African or Middle Eastern ethnicity. Neutrophil values are commonly included in eligibility criteria for research participation, but little is known about the relationship between BEN, HIV acquisition, and the occurrence of adverse events during clinical trials. We investigated these relationships using data from an HIV vaccine efficacy trial of healthy adults from 5 South African sites. We analysed data from the double-blind, placebo-controlled, randomized trial HVTN 503, and its follow-on study HVTN 503-S to assess the prevalence of BEN, its association with HIV infection, and adverse event reporting. These data were then compared with a time- and age-matched, non-pregnant cohort from the National Health and Nutrition Examination Survey (NHANES) conducted between 2007–2008 in the United States (US). The 739 South African participants had a median age of 22.0 years (interquartile range = 20–26) and 56% (n = 412) were male. Amongst the US cohort of 845 participants, the median age was 26 (IQR: 21–30) and the majority (54%, 457/745) were also male. BEN was present at enrolment in 7.0% (n = 52) of South African participants (6% in the placebo group versus 8% in the vaccine group); 81% (n = 42) of those with BEN were male. Pretoria North had the highest prevalence of BEN (11.6%, 5/43), while Cape Town had the lowest (0.7%, 1/152). Participants with BEN had a lower median neutrophil count (1.3 vs. 3.2x10⁹ cells/L; p<0.001) and BMI (20.8 vs. 22.3 kg/m²; p<0.001) when compared to those without BEN. A greater proportion of Black South Africans had neutrophil counts <1.5×10⁹ cells/L compared to US non-Hispanic Whites from the NHANES cohort (7% [52/739] vs. 0.6% [3/540]; p<0.001). BEN did not increase the odds for HIV infection (adjusted odds ratio [aOR]: 1.364, 95% confidence interval [95% CI]: 0.625–2.976; p = 0.4351). However, female gender (aOR: 1.947, 95% CI: 1.265–2.996; p = 0.0025) and cannabis use (aOR: 2.192, 95% CI: 1.126–4.266; p = 0.0209) increased the odds of HIV acquisition. The incidence rates of adverse events were similar between participants in the placebo group with BEN, and those without: 12.1 (95% CI: 7.3–20.1) vs. 16.5 (95% CI: 14.6–18.7; p = 0.06) events per 100 person-years (py) were noted in the infections and infestations system organ class, respectively. The vaccine group had an event incidence rate of 19.7 (95% CI: 13.3–29.2) vs. 14.8 (95% CI: 13.0–16.8; p = 0.07) events per 100py in the group with, and without BEN, respectively. BEN is more prevalent in Black South Africans compared to US Non-Hispanic Whites. Our data do not support excluding populations from HIV vaccine trials because of BEN. BEN was not associated with increased risk for HIV infection or Adverse events on a vaccine trial. Predictors of HIV infection risk were females and cannabis use, underlying the continued importance of prevention programmes in focusing on these populations.

Review of preventative HIV vaccine clinical trials in South Africa

New HIV infections continue relentlessly in southern Africa, demonstrating the need for a vaccine to prevent HIV subtype C. In South Africa, the country with the highest number of new infections annually, HIV vaccine research has been ongoing since 2003 with collaborative public-private-philanthropic partnerships. So far, 21 clinical trials have been conducted in South Africa, investigating seven viral vectors, three DNA plasmids, four envelope proteins, five adjuvants and three monoclonal antibodies. Active vaccine candidates have spanned subtypes A, B, C, E and multi-subtype mosaic sequences. All were well tolerated. Four concepts were investigated for efficacy: rAd5-gag/pol/nef showed increased HIV acquisition in males, subtype C ALVAC/gp120/MF59 showed no preventative efficacy, and the trials for the VRC01 monoclonal antibody and Ad26.Mos4.HIV/subtype C gp140/ aluminum phosphate are ongoing. Future trials are planned with DNA/viral vector plus protein combinations in concert with pre-exposure prophylaxis, and sequential immunization studies with transmitted/founder HIV envelope to induce broadly neutralizing antibodies. Finally, passive immunization trials are underway to build on the experience with VRC01, including single and combination antibody trials with an antibody derived from a subtype-C-infected South African donor. Future consideration should be given to the evaluation of novel strategies, for example, inactivated-whole-virus vaccines.

Long-term mucosal T cell activation and homing phenotypes in recipients of an Ad5-vectored HIV vaccine

BACKGROUND

Vaccine-induced mucosal immune responses may be critical for protection against HIV infection, but may also result in short or long-term changes that enhance susceptibility to infection in some individuals, such as those with baseline seroreactivity to vaccine vector antigens. We examined cellular immune responses in blood and gut mucosal tissue roughly two years following vaccination with placebo or the Step study vaccine MRKAd5/HIV-1.

METHODS

Participants vaccinated with either placebo or MRKAd5/HIV-1 during participation in HVTN 071, and HVTN 502/Merck 023 underwent phlebotomy and colonic mucosal biopsies via flexible sigmoidoscopy at two timepoints roughly six months apart. After isolation of mononuclear cells, we compared cellular phenotypes and intracellular cytokine responses in vaccine and placebo recipients with and without baseline serological reactivity to Ad5.

RESULTS

Surface expression of activation and gut-homing markers were elevated on CD4 + and CD8 + gut mucosal mononuclear cells (GMMC) in comparison with PBMC (p < 0.01), but were not significantly affected by baseline Ad5 serostatus or receipt of MRKAd5/HIV-1. ICS responses to stimulation with vaccine antigens were of low frequency and magnitude. Ad5 vector responses were seen in vaccinees and baseline seropositive individuals. CD4 + responses to vector antigens were more common in GMMC than PBMC (p < 0.01) and CD8 + responses to HIV gag insert antigens were more frequent in Ad5 seropositive than Ad5 seronegative individuals (p = 0.03).

CONCLUSION

Vaccination with the Ad5 vectored candidate HIV vaccine MRKAd5/HIV-1 does not lead to long-term changes in the activation state of mucosal CD4 + or CD8 + T lymphocytes regardless of baseline Ad5 serostatus. The findings of this study do not reveal a basis for enhanced susceptibility to HIV infection two years post vaccination.

Overcoming immunogenicity issues of HIV p24 antigen by the use of innovative nanostructured lipid carriers as delivery systems: evidences in mice and non-human primates

HIV is one of the deadliest pandemics of modern times, having already caused 35 million deaths around the world. Despite the huge efforts spent to develop treatments, the virus cannot yet be eradicated and continues to infect new people. Spread of the virus remains uncontrolled, thus exposing the worldwide population to HIV danger, due to the lack of efficient vaccines. The latest clinical trials describe the challenges associated with developing an effective prophylactic HIV vaccine. These immunological obstacles will only be overcome by smart and innovative solutions applied to the design of vaccine formulations. Here, we describe the use of nanostructured lipid carriers (NLC) for the delivery of p24 protein as a model HIV antigen, with the aim of increasing its immunogenicity. We have designed vaccine formulations comprising NLC grafted with p24 antigen, together with cationic NLC optimized for the delivery of immunostimulant CpG. This tailored system significantly enhanced immune responses against p24, in terms of specific antibody production and T-cell activation in mice. More importantly, the capacity of NLC to induce specific immune responses against this troublesome HIV antigen was further supported by a 7-month study on non-human primates (NHP). This work paves the way toward the development of a future HIV vaccine, which will also require the use of envelope antigens.

To date, HIV vaccines have resulted in poor or absent protection. A team led by Fabrice P. Navarro at the CEA LETI use the conserved HIV capsid protein p24 vectorized into cationic nanostructured lipid carriers (NLC-p24) along with NLC-delivered CpG. Owing to their small size, NLCs gain access to lymph nodes and deliver antigen directly to antigen presenting cells. Anti-p24 responses have been associated with effective HIV control, making them an attractive vaccine antigen, but they are poorly immunogenic. NLC-p24 shows a good safety profile while at the same time being able to elicit robust humoral and cellular immune responses in both mice and Cynomolgus macaques. NLC-mediated delivery of both p24 and CpG results in more effective immune stimulation than delivery of free antigen and adjuvant. These findings demonstrate the possibility of priming effective responses to a potent but otherwise poorly immunogenic HIV antigen.

Regulatory T cell abundance and activation status before and after priming with HIVIS-DNA and boosting with MVA-HIV/rgp140/GLA-AF may impact the magnitude of the vaccine-induced immune responses

BACKGROUND

Little is known about regulatory CD4 T cells (Tregs) in the context of HIV vaccines. Tregs can be differentiated into resting (FoxP3⁺CD45RA⁺ - rTregs), activated (FoxP3^HighCD45RA^- - aTregs) and memory (FoxP3^LowCD45RA^- - mTregs). Tregs, as CD4 T cells, are also frequent targets for HIV infection. We studied how the abundance and phenotypes of Tregs in terms of activation status and expression of HIV-1 binding molecules would have changed during vaccination in healthy volunteers participating in a phase IIa HIV vaccine clinical trial. Subjects were primed three times with HIVIS-DNA and boosted twice with MVA-CMDR-HIV alone (n = 12) or MVA-CMDR combined with protein CN54rgp140 (n = 13). The proportions of β7 integrin in all CD4 T cells and in the Tregs subset decreased moderately after the final vaccination (p = 0.001 and p = 0.033, respectively) and the rTregs proportion within the total Tregs were also decreased after the final vaccination (p = 0.038). All these proportions returned to normal values within the three months after the final vaccination. The magnitude of HIV-Envelope-specific IFNγ + T cells after vaccination (r = 0.66; p = 0.021) correlated directly with the proportion of Tregs, and correlated inversely correlated with ratios of Th17/Tregs (r = -0.75; p = 0.0057) and Th17/mTregs (r = -0.78; p = 0.0065). Higher titers of IgG gp140 antibodies were observed in subjects with higher mTregs proportions (r = 0.52; p = 0.022). Interestingly, pre-vaccination levels of mTregs correlated with vaccine-induced Env-binding antibodies (r = 0.57; p = 0.01) and presence of neutralizing antibodies (r = 0.61; p = 0.01), while the pre-vaccination Th17/mTregs ratio correlated inversely with the magnitude of cellular IFN-γ ELISpot responses (r = -0.9; p = 0.002). Taken together, these results suggest that pre- and post-vaccination Tregs, their activation status, the Th17/Tregs ratio and other host factors affecting Treg abundance, have an impact on the magnitude of HIV vaccine-induced immune responses. Moreover, the DNA-HIVIS/MVA-HIV regimen, alone or in combination with CN54rgp140 induced moderate and temporary alterations of the Tregs activation status. We also show a decrease in expression of the HIV-1 ligand β7 integrin on Tregs and all CD4 T cells.

Pathology-Based Research in Africa

The process of conducting pathology research in Africa can be challenging. But the rewards in terms of knowledge gained, quality of collaborations, and impact on communities affected by infectious disease and cancer are great. This report reviews 3 different research efforts: fatal malaria in Malawi, mucosal immunity to HIV in South Africa, and cancer research in Uganda. What unifies them is the use of pathology-based approaches to answer vital questions, such as physiology, pathogenesis, predictors of clinical course, and diagnostic testing schemes.

Daily and non-daily pre-exposure prophylaxis in African women (HPTN 067/ADAPT Cape Town Trial): a randomised, open-label, phase 2 trial

BACKGROUND

The relative feasibility and acceptability of daily versus non-daily dosing of oral HIV pre-exposure prophylaxis (PrEP) among women are unknown. We aimed to investigate the feasibility of non-daily PrEP regimens in adult women.

METHODS

We did a randomised, open-label, phase 2 clinical trial (HPTN 067/ADAPT) of oral PrEP with emtricitabine plus tenofovir disoproxil fumarate at a research centre in Cape Town, South Africa. Participants were adult women (age ≥18 years) who received directly observed dosing once a week for 5 weeks followed by random assignment (1:1:1) at week 6 to one of three unblinded PrEP regimens for self-administered dosing over 24 weeks: daily; time-driven (twice a week plus a post-sex dose); or event-driven (one tablet both before and after sex). Primary outcomes were PrEP coverage (at least one dose within the 4 days before sex and one dose within 24 h after sex), pills needed or used to achieve regimen-specific adherence and coverage, and symptoms and side-effects. All analyses were by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01327651; the trial is completed and this report presents the final analysis.

FINDINGS

Between Sept 12, 2011, and Oct 3, 2012, 191 women were enrolled to the trial. 178 (93%) completed directly observed dosing and were randomly assigned one of the three PrEP regimens for the self-administered phase: 59 were allocated the daily regimen, 59 the time-driven regimen, and 60 the event-driven regimen. Median age of women was 26 years (IQR 21-37; range 18-52). In women allocated the daily regimen, 1459 (75%) of 1952 sex events were covered by PrEP, compared with 599 (56%) of 1074 sex events among those assigned the time-driven regimen (odds ratio [OR] 2·35, 95% CI 1·43-3·83; p=0·0007) and 798 (52%) of 1542 sex events among those allotted the event-driven regimen (2·76, 1·68-4·53; p<0·0001). Fewer pills were needed for complete adherence in women allocated non-daily regimens (vs daily regimen, relative mean 2·53 [95% CI 2·39-2·69] for the time-driven regimen and 4·16 [3·59-4·82] for the event-driven regimen; p<0·0001). Side-effects were uncommon. Eight HIV seroconversions occurred overall, with four documented during the self-administered phase (two with the time-driven regimen and two with the event-driven regimen). Adherence to the assigned regimen was 75% (7283 of 9652 doses taken) for women allocated the daily regimen compared with 65% for those assigned the time-driven regimen (2367 of 3616 doses taken; p=0·0028) and 53% for those allotted the event-driven regimen (1161 of 2203 doses taken; p<0·0001). When sex was reported in the previous week, PrEP drugs were detected (above the lower limits of quantification) more frequently in women assigned the daily regimen (73 [68%] of 107 samples) than in those allocated the time-driven regimen (42 [58%] of 72 samples) and the event-driven regimen (41 [41%] of 99 samples).

INTERPRETATION

Daily PrEP dosing resulted in higher coverage of sex events, increased adherence to the regimen, and augmented drug concentrations than did either time-driven or event-driven dosing. These findings support recommendations for daily use of PrEP with oral emtricitabine plus tenofovir disoproxil fumarate in women.

FUNDING

HIV Prevention Trials Network.

Sieve analysis of breakthrough HIV-1 sequences in HVTN 505 identifies vaccine pressure targeting the CD4 binding site of Env-gp120

Although the HVTN 505 DNA/recombinant adenovirus type 5 vector HIV-1 vaccine trial showed no overall efficacy, analysis of breakthrough HIV-1 sequences in participants can help determine whether vaccine-induced immune responses impacted viruses that caused infection. We analyzed 480 HIV-1 genomes sampled from 27 vaccine and 20 placebo recipients and found that intra-host HIV-1 diversity was significantly lower in vaccine recipients (P ≤ 0.04, Q-values ≤ 0.09) in Gag, Pol, Vif and envelope glycoprotein gp120 (Env-gp120). Furthermore, Env-gp120 sequences from vaccine recipients were significantly more distant from the subtype B vaccine insert than sequences from placebo recipients (P = 0.01, Q-value = 0.12). These vaccine effects were associated with signatures mapping to CD4 binding site and CD4-induced monoclonal antibody footprints. These results suggest either (i) no vaccine efficacy to block acquisition of any viral genotype but vaccine-accelerated Env evolution post-acquisition; or (ii) vaccine efficacy against HIV-1s with Env sequences closest to the vaccine insert combined with increased acquisition due to other factors, potentially including the vaccine vector.

Development of targeted adjuvants for HIV-1 vaccines

Finding new adjuvants is an integrated component of the efforts in developing an effective HIV-1 vaccine. Compared with traditional adjuvants, a modern adjuvant in the context of HIV-1 prevention would elicit a durable and potent memory response from B cells, CD8⁺ T cells, and NK cells but avoid overstimulation of HIV-1 susceptible CD4⁺ T cells, especially at genital and rectal mucosa, the main portals for HIV-1 transmission. We briefly review recent advances in the studies of such potential targeted adjuvants, focusing on three classes of molecules that we study: TNFSF molecules, TLRs agonists, and NODs agonists.

Using surrogate vaccines to assess feasibility and acceptability of future HIV vaccine trials in men: a randomised trial in inner-city Johannesburg, South Africa

BACKGROUND

Developing an effective HIV vaccine is the overriding priority for HIV prevention research. Enrolling and maintaining cohorts of men into HIV vaccine efficacy trials is a necessary prerequisite for the development and licensure of a safe and efficacious vaccine.

METHODS

One hundred-fifty consenting HIV-negative men were enrolled into a pilot 1:1 randomised controlled trial of immediate vaccination with a three-dose hepatitis B vaccine compared to deferred vaccination (at 12 months) to investigate feasibility and acceptability of a future HIV vaccine trial in this population. Adverse events, changes in risk behaviour, acceptability of trial procedures and motivations for participation in future trials were assessed.

RESULTS

Men were a median 25 years old (inter-quartile range = 23-29), 53% were employed, 90% secondary school educated and 67% uncircumcised. Of the 900 scheduled study visits, 90% were completed in the immediate vaccination arm (405/450) and 88% (396/450) in the delayed arm (P = 0.338). Acceptability of trial procedures and services was very high overall. However, only 65% of the deferred group strongly liked being randomised compared to 90% in the immediate group (P = 0.001). Informed consent processes were viewed favourably by 92% of the delayed and 82% of the immediate group (P = 0.080). Good quality health services, especially if provided by a male nurse, were rated highly. Even though almost all participants had some concern about the safety of a future HIV vaccine (98%), the majority were willing to participate in a future trial. Future trial participation would be motivated mainly by the potential for accessing an effective vaccine (81%) and altruism (75%), rather than by reimbursement incentives (2%).

CONCLUSIONS

Recruitment and retention of men into vaccine trials is feasible and acceptable in our setting. Findings from this surrogate vaccine trial show a high willingness to participate in future HIV vaccine trials. While access to potentially effective vaccines is important, quality health services are an equally compelling incentive for enrolment.

Synthetic biology approach for the development of conditionally replicating HIV-1 vaccine

While the combined antiretroviral therapy has resulted in a significant decrease in HIV-1 related morbidity and mortality, the HIV-1 pandemic has not been substantially averted. To curtail the 2.4 million new infections each year, a prophylactic HIV-1 vaccine is urgently needed. This review first summarizes four major completed clinical efficacy trials of prophylactic HIV-1 vaccine and their outcomes. Next, it discusses several other approaches that have not yet advanced to clinical efficacy trials, but provided valuable insights into vaccine design. Among them, live-attenuated vaccines (LAVs) provided excellent protection in a non-human primate model. However, safety concerns have precluded the current version of LAVs from clinical application. As the major component of this review, two synthetic biology approaches for improving the safety of HIV-1 LAVs through controlling HIV-1 replication are discussed. Particular focus is on a novel approach that uses unnatural amino acid-mediated suppression of amber nonsense codon to generate conditionally replicating HIV-1 variants. The objective is to attract more attention towards this promising research field and to provoke creative designs and innovative utilization of the two control strategies.

Current views on the potential for development of a HIV vaccine

INTRODUCTION

Despite many recent advances in the HIV prevention landscape, an effective vaccine remains the most promising tool to end the HIV-1 pandemic. Areas covered: This review summarizes past HIV vaccine efficacy trials and current vaccine strategies as well as new approaches about to move into first-in-human trials. Expert opinion: Despite many setbacks in early HIV vaccine efficacy trials, the success of RV144 has provided the glimmer of hope necessary to invigorate the vaccine field, and has led to the development of a large number of vaccine strategies aiming at inducing an array of different immune responses. The follow-up pox-protein trials, developed to replicate and enhance the polyfunctional antibody responses induced by the RV144 regimen, are already reaching efficacy trials, while a large body of work providing a more complete understanding of the development of broadly neutralizing antibodies is now being translated into immunogen design using several different strategies. T-cell based vaccines, fallen out of favor after Ad5-based trials showed increased infection rates in Ad5 seropositive vaccine recipients, are experiencing a comeback based in part on the promising results from non-human primate challenge studies using rhCMV-based immunogens. This diverse array of vaccine candidates may finally allow us to identify a broadly effective HIV vaccine able to contain the epidemic.

Trained Immunity and Susceptibility to HIV

In this issue of Clinical and Vaccine Immunology, K. Jensen et al. (Clin Vaccine Immunol 24:e00360-16, 2017, https://doi.org/10.1128/CVI.00360-16) describe a dual-purpose attenuated Mycobacterium tuberculosis-simian immunodeficiency virus vaccine (AMTB-SIV). Interestingly, immunized infant macaques required fewer oral exposures to SIV to become infected relative to nonimmunized animals. The authors hypothesized that augmented susceptibility to SIV was due to activation of CD4⁺ T cells through trained immunity. This commentary explores the possible relationship between trained immunity, enhanced CD4 T cell responses, and increased susceptibility to human immunodeficiency virus (HIV).

Approaches to preventative and therapeutic HIV vaccines

Novel strategies are being researched to discover vaccines to prevent and treat HIV-1. Non-efficacious preventative vaccine approaches include bivalent recombinant gp120 alone, HIV gene insertion into an Adenovirus 5 (Ad5) virus vector and the DNA prime/Ad5 boost vaccine regimen. However, the ALVAC-HIV prime/AIDSVAX® B/E gp120 boost regimen showed 31.2% efficacy at 3.5 years, and is being investigated as clade C constructs with an additional boost. Likewise, although multiple therapeutic vaccines have failed in the past, in a non-placebo controlled trial, a Tat vaccine demonstrated immune cell restoration, reduction of immune activation, and reduced HIV-1 DNA viral load. Monoclonal antibodies for passive immunization or treatment show promise, with VRC01 entering advanced clinical trials.

HIV-1 prophylactic vaccines: state of the art

The quest for an effective HIV-1 vaccine began early in the course of the HIV pandemic. Over time, the paradigm has evolved from B cell- towards T cell-based vaccines. Results from initial Phase II/III trials have been disappointing; however, while modest, the unexpected results of the Phase II/III RV144 trial in Thailand have re-energised the field. Indeed a clear correlation was demonstrated in this trial between protection and immunological biomarkers, namely non-neutralising antibodies against the V1V2 region. Recent data obtained from cohorts of recently HIV-1-infected individuals have enabled exploration of the role of neutralising antibodies and their potential use in HIV-1 prevention. Results from non-human primate models using a cytomegalovirus vector have also shown the potential for a prophylactic HIV vaccine to induce effective T cell responses. Finally, the development of new vaccine vectors and trial strategies has also allowed progress in the field. Therefore, HIV-1 vaccine research remains a dynamic field that has also been stimulated by the recent positive results of pre-exposure prophylaxis strategies with antiretrovirals.