Current approaches to HIV vaccine development: a narrative review

Harnessing Nanotechnology in HIV Therapy: Exploring Molecular Pathogenesis and Treatment Strategies with Special Reference to Chemotherapy and Immunotherapy

Human immunodeficiency virus (HIV) continues to be a global threat, contributing substantially to social and economic burdens worldwide. Synthetic ARV drugs are classified into six different classes viz NRTIs, NNRTIs, PIs, IIs, INSTIs, and FIs. Highly active anti-retroviral therapy (HAART) which is a combination of two or more ARV drugs from different classes is gaining immense popularity in the HIV therapy regimen due to its better therapeutic outcome. However, despite its successful endeavor in significant viral suppression, synthetic drugs are associated with numerous adverse effects. To mitigate this issue, scientists are exploring ARV agents derived from various natural sources like plants, and marine organisms that can exhibit potent anti-HIV activity with minimal side effects. Nevertheless, both synthetically and naturally derived ARV agents have failed to exhibit eradication of HIV from latent reservoirs. Henceforth, researchers are shifting their attention towards formulating a drug-encapsulated nano-delivery system to ensure a significant amount of drug delivery into these reservoirs. Additionally, the discovery of a novel HIV vaccine that can induce robust immune responses against multiple HIV strains and facilitate complete removal of the virus before the establishment of a latent reservoir is the need of an hour. Briefly, we discussed various synthetic and natural chemotherapeutic agents along with their specificity and limitations, different drug-delivery devices for ART, immunotherapy, vaccines, and lastly, challenges and strategies associated with vaccine development.

In danger: HIV vaccine research and development in Europe

Highly effective antiretroviral-based HIV prevention plays an important role in ending the global HIV/AIDS epidemic. However, the sustainable control of the epidemic is hampered by unequal access to prevention options, including HIV testing, alongside with drug resistance and ongoing barriers to accessing sustainable HIV treatment. Therefore, an HIV vaccine, combined with effective prevention and treatment, remains an absolute necessity to control the epidemic. Yet, the recent discontinuation of four major vaccine efficacy studies is raising concerns about the future of HIV vaccine research and development globally, and particularly in the European region where funding for vaccine research and development has shrinked. This viewpoint emphasises that supporting HIV vaccine research and development at the European level remains crucial: it is not only necessary to control the epidemic, but it promotes innovation, strengthens health security, epidemic preparedness, and health sovereignty while contributing to the economies of European nations.

Vaccination for prevention of hearing loss: a scoping review

BACKGROUND

Infectious diseases in childhood and adolescence are significant and often preventable causes of hearing loss, especially in low- and middle-income countries. We conducted a scoping review to examine the extent, range and nature of available evidence on the role of vaccination for prevention of hearing loss worldwide.

METHODS

We reviewed the published scientific literature to identify studies providing quantitative information on the relationship between vaccination and hearing loss. We searched four databases: MEDLINE, EMBASE, Cochrane Library and Global Index Medicus. No date, language, or geographical restrictions were imposed. Two independent reviewers assessed eligibility and charted data.

RESULTS

Here we show that vaccination may be a key, underexploited strategy for primary prevention of child and adolescent hearing loss. Although the important contributions of rubella and meningitis vaccinations to hearing loss prevention are widely recognised, we identify 26 distinct known or potential infectious causes of hearing loss that are preventable or possibly preventable through vaccination. Notwithstanding, we find a dearth of empirical evidence on the impacts of vaccination on hearing loss prevention. In addition, the review identifies no research from low- and middle-income countries, which bear the overwhelming burden of child and adolescent hearing loss. Finally, it shows that numerous vaccines that address priority infectious diseases relevant to hearing loss are in development and could be brought into use.

CONCLUSIONS

We recommend strategic investment in research concerning vaccination as a strategy for primary prevention of child and adolescent hearing loss.

Modern approaches to predicting vaccine hesitancy: A scoping review

Introduction

Motivated by the disproportionate burden of infectious diseases on vulnerable populations and the risk of future pandemics, we conducted a scoping review to analyze the state of the literature about "vaccine uptake indices," defined as models that predict vaccination rates by geospatial area. We analyzed novel vaccine uptake indices created in response to the recent COVID-19 pandemic. The aim of this scoping review is to survey the state of the literature regarding vaccine uptake indices relating to COVID-19 and other infectious diseases.

Methods

We conducted a scoping review with a systematic search strategy to identify relevant articles from the databases Embase, PubMed, and Web of Science with title and abstract screening, full-text review, and data extraction.

Results

Database searches resulted in 3,615 potential articles, of which 229 reports were included. Fifteen studies (7%) were determined to be methodologically advanced vaccine uptake indices that had at least three of the following characteristics: the use of individual- and population-level predictor variables (100 [44%]), geo-spatiotemporal analysis (58 [25%]), data usage agnostic to vaccine specificity (50 [22%]), or sociobehavioral frameworks of health (such as the Health Belief Model and Theory of Planned Behavior) (30 [13%]).

Conclusion

This scoping review offers suggestions for future research of next-generation vaccine uptake indices before use in vaccination campaigns of recurring or novel infectious diseases. Areas to pursue include utilizing individual-level data about vaccination behaviors in conjunction with administrative data, solving the challenge of implementing small-area spatiotemporal analysis, using vaccine-agnostic methods that consider data from more than one infectious disease, and assisting causal inference with theoretical frameworks.

Determinants of Potential HIV Vaccine Uptake Among Young Sexual Minoritized Men 17-24 Year Old

BACKGROUND

Failures in prior rollout of HIV prevention efforts have widened disparities in HIV incidence by race/ethnicity among young sexual minoritized men (YSMM). We hypothesized greater perceptions of medical mistrust would be associated with lower willingness to get an HIV vaccine, mediating the relationship between race/ethnicity and willingness to accept a future HIV vaccine.

METHODS

HIV-negative and unknown-status YSMM 17-24 years old (n = 229) recruited through social media and men-for-men networking apps completed online surveys from September 2021 to March 2022. Participants were asked about demographics, medical mistrust (health care-related sexual orientation stigma, health care-related race stigma, global medical mistrust, and trust in health care providers), and willingness to accept a future HIV vaccine.

RESULTS

Vaccine willingness was highest among White YSMM (96.0%) and lower among Black (71.0%), Latino (83.6%), and multiracial or another race/ethnicity YSMM (80.0%). Even after accounting for medical mistrust constructs as mediators, compared with White participants, Black participants had lower odds of being willing to accept a future HIV vaccine. Participants with greater trust in health care providers had higher odds of willingness to accept a future HIV vaccine.

DISCUSSION

Gaps in willingness to get an HIV vaccine are evident among YSMM by race/ethnicity, indicating potential further widening of disparities in HIV incidence when a vaccine becomes available without intervention.

Neutralizing antibodies elicited in macaques recognize V3 residues on altered conformations of HIV-1 Env trimer

Eliciting broadly neutralizing antibodies that protect against diverse HIV-1 strains is a primary goal of AIDS vaccine research. We characterized Ab1456 and Ab1271, two heterologously-neutralizing antibodies elicited in non-human primates by priming with an engineered V3-targeting SOSIP Env immunogen and boosting with increasingly native-like SOSIP Envs derived from different strain backgrounds. Structures of Env trimers in complex with these antibodies revealed V3 targeting, but on conformational states of Env distinct from the typical closed, prefusion trimeric SOSIP structure. Env trimers bound by Ab1456 adopted conformations resembling CD4-bound open Env states in the absence of soluble CD4, whereas trimers bound by Ab1271 exhibited a trimer apex-altered conformation to accommodate antibody binding. The finding that elicited antibodies cross-neutralized by targeting altered, non-closed, prefusion Env trimer conformations provides important information about Env dynamics that is relevant for HIV-1 vaccine design aimed at raising antibodies to desired epitopes on closed pre-fusion Env trimers.

Research on Maternal Vaccination for HIV Prevention

Despite increased uptake of antiretroviral therapy (ART) among pregnant people living with human immunodeficiency virus (HIV), vertical transmission remains the most important route of pediatric HIV acquisition. The numbers of HIV acquisitions in infancy have remained alarmingly stagnant in recent years. It is evident that additional strategies that can synergize with ART will be required to end the pediatric HIV epidemic. In this review, we discuss the potential for immune-based interventions that can be administered in conjunction with current ART-based strategies to the birthing parent for prevention of vertical transmission of HIV-1, and the potential challenges associated with each approach.

Biotech's role in advancing HIV vaccine development

HIV vaccine development has been hindered by significant challenges over four decades. Despite persistent efforts, all efficacy trials to date have yielded disappointing results. This has pushed the field back to the discovery phase and created uncertainty about the future involvement of large pharmaceutical companies. Currently, the HIV vaccine landscape is dominated by startup biotech firms, which face a complex array of obstacles. These include evolving HIV prevention methods, waning interest in vaccine research, and difficulties securing sustainable funding. This viewpoint explores the challenges faced by these biotech companies and the support mechanisms necessary for their continued involvement in HIV vaccine development. By leveraging insights from both pharmaceutical and biotech sectors, we propose a multi-faceted approach that includes enhanced communication, fostering innovation, and implementing strategic funding models.

Mosaic HIV-1 vaccine and SHIV challenge strain V2 loop sequence identity and protection in primates

The failure of human vaccine efficacy trials assessing a mosaic HIV-1 vaccine calls into question the translatability of preclinical SHIV challenge studies that demonstrated high efficacy of this vaccine in primates. Here we present a post hoc immune correlates analysis of HIV-1 Env peptide-binding antibody responses from the NHP13-19 study identifying the V2 loop as the principal correlate of protection in primates. Moreover, we found high V2 loop sequence identity between the Mos1 vaccine component and the SHIV challenge strain, while the vaccine showed considerably lower V2 identity to globally circulating HIV-1 sequences. Thus, the induction of immune responses against the V2 epitope, which had exceptional identity between the vaccine and challenge Env strains, may have contributed to the high protection in primates.

Human Immunodeficiency Virus Vaccine: Promise and Challenges

Development of a safe and effective human immunodeficiency virus (HIV) vaccine is a persistent challenge despite decades of research. Previous strategies utilizing protein subunit and viral vector vaccines were safe but not protective. Current strategies seek to induce broadly neutralizing antibodies, with multiple early phase trials in progress seeking to achieve this through sequential vaccination, mRNA, or updated viral-vectored vaccines. A safe and effective vaccine is critical to ending the HIV epidemic.

Clinical trials and recent progress in HIV vaccine development

The greatest obstacle for scientists is to develop an effective HIV vaccine. An effective vaccine represents the last hope for halting the unstoppable global spread of HIV and its catastrophic clinical consequences. Creating this vaccine has been challenging due to the virus's extensive genetic variability and the unique role of cytotoxic T lymphocytes (CTL) in containing it. Innovative methods to stimulate CTL have demonstrated significant therapeutic advantages in nonhuman primate model systems, unlike traditional vaccination techniques that are not expected to provide safe and efficient protection against HIV. Human clinical trials are currently evaluating these vaccination strategies, which involve plasmid DNA and live recombinant vectors. This review article covers the existing vaccines and ongoing trial vaccines. It also explores the different approaches used in developing HIV vaccines, including their molecular mechanisms, target site effectiveness, and potential side effects.

Non-HIV Vaccine-Induced Immune Responses as Potential Baseline Immunogenicity Predictors of ALVAC-HIV and AIDSVAX B/E-Induced Immune Responses

Identifying correlations between immune responses elicited via HIV and non-HIV vaccines could aid the search for correlates of HIV protection and increase statistical power in HIV vaccine-efficacy trial designs. An exploratory objective of the HVTN 097 phase 1b trial was to assess whether immune responses [focusing on those supported as correlates of risk (CoR) of HIV acquisition] induced via the RV144 pox-prime HIV vaccine regimen correlated with those induced via tetanus toxoid (TT) and/or hepatitis B virus (HBV) vaccines. We measured TT-specific and HBV-specific IgG-binding antibody responses and TT-specific and HBV-specific CD4+ T-cell responses at multiple time points in HVTN 097 participants, and we assessed their correlations at peak time points with HIV vaccine (ALVAC-HIV and AIDSVAX B/E)-induced responses. Four correlations were significant [false discovery rate-adjusted p-value (FDR) ≤ 0.2]. Three of these four were with IgG-binding antibody responses to TT measured one month after TT receipt, with the strongest and most significant correlation [rho = 0.368 (95% CI: 0.096, 0.588; p = 0.008; FDR = 0.137)] being with IgG-binding antibody responses to MN gp120 gDneg (B protein boost) measured two weeks after the second ALVAC-HIV and AIDSVAX B/E boost. The fourth significant correlation [(rho = 0.361; 95% CI: 0.049, 0.609; p = 0.021; FDR = 0.137)] was between CD4+ T-cell responses to a hepatitis B surface antigen peptide pool, measured 2 weeks after the third HBV vaccination, and IgG-binding antibody responses to gp70BCaseAV1V2 (B V1V2 immune correlate), measured two weeks after the second ALVAC-HIV and AIDSVAX B/E boost. These moderate correlations imply that either vaccine, TT or HBV, could potentially provide a moderately useful immunogenicity predictor for the ALVAC-HIV and AIDSVAX B/E HIV vaccine regimen.

Protein Dose-Sparing Effect of AS01B Adjuvant in a Randomized Preventive HIV Vaccine Trial of ALVAC-HIV (vCP2438) and Adjuvanted Bivalent Subtype C gp120

BACKGROUND

HVTN 120 is a phase 1/2a randomized double-blind placebo-controlled human immunodeficiency virus (HIV) vaccine trial that evaluated the safety and immunogenicity of ALVAC-HIV (vCP2438) and MF59- or AS01B-adjuvanted bivalent subtype C gp120 Env protein at 2 dose levels in healthy HIV-uninfected adults.

METHODS

Participants received ALVAC-HIV (vCP2438) alone or placebo at months 0 and 1. At months 3 and 6, participants received either placebo, ALVAC-HIV (vCP2438) with 200 μg of bivalent subtype C gp120 adjuvanted with MF59 or AS01B, or ALVAC-HIV (vCP2438) with 40 μg of bivalent subtype C gp120 adjuvanted with AS01B. Primary outcomes were safety and immune responses.

RESULTS

We enrolled 160 participants, 55% women, 18-40 years old (median age 24 years) of whom 150 received vaccine and 10 placebo. Vaccines were generally safe and well tolerated. At months 6.5 and 12, CD4+ T-cell response rates and magnitudes were higher in the AS01B-adjuvanted groups than in the MF59-adjuvanted group. At month 12, HIV-specific Env-gp120 binding antibody response magnitudes in the 40 μg gp120/AS01B group were higher than in either of the 200 μg gp120 groups.

CONCLUSIONS

The 40 μg dose gp120/AS01B regimen elicited the highest CD4+ T-cell and binding antibody responses. Clinical Trials Registration . NCT03122223.

Engineered ClearColi™-derived outer membrane vesicles as functional carriers for development of HIV-1 therapeutic vaccine candidate

Bacteria-derived outer membrane vesicles (OMVs) can be engineered to incorporate foreign antigens. This study explored the potential of ClearColi™-derived OMVs as a natural adjuvant and a carrier (recombinant OMVs or rOMVs) for development of an innovative therapeutic vaccine candidate harboring HIV-1 Nef and Nef-Tat antigens. Herein, the rOMVs containing CytolysinA (ClyA)-Nef and ClyA-Nef-Tat fusion proteins were isolated from ClearColi™ strain. The presence of Nef and Nef-Tat proteins on their surface (rOMVNef and rOMVNef-Tat) was confirmed by western blotting after proteinase K treatment. Immune responses induced by Nef and Nef-Tat proteins emulsified with Montanide® ISA720 or mixed with OMVs, and also rOMVNef and rOMVNef-Tat were investigated in BALB/c mice. Additionally, the potency of splenocytes exposed to single-cycle replicable (SCR) HIV-1 virions was assessed for the secretion of cytokines in vitro. Our findings showed that the rOMVs as an antigen carrier (rOMVNef and rOMVNef-Tat) induced higher levels of IgG2a, IFN-γ and granzyme B compared to OMVs as an adjuvant (Nef + OMV and Nef-Tat + OMV), and also Montanide® ISA720 (Nef + Montanide and Nef-Tat + Montanide). Moreover, IFN-γ level in splenocytes isolated from mice immunized with rOMVNef-Tat was higher than other regimens after exposure to SCR virions. Generally, ClearColi™-derived rOMVs can serve as potent carriers for developing effective vaccines against HIV-1 infection.

Safety and Efficacy of Antiviral Drugs and Vaccines in Pregnant Women: Insights from Physiologically Based Pharmacokinetic Modeling and Integration of Viral Infection Dynamics

Addressing the complexities of managing viral infections during pregnancy is essential for informed medical decision-making. This comprehensive review delves into the management of key viral infections impacting pregnant women, namely Human Immunodeficiency Virus (HIV), Hepatitis B Virus/Hepatitis C Virus (HBV/HCV), Influenza, Cytomegalovirus (CMV), and SARS-CoV-2 (COVID-19). We evaluate the safety and efficacy profiles of antiviral treatments for each infection, while also exploring innovative avenues such as gene vaccines and their potential in mitigating viral threats during pregnancy. Additionally, the review examines strategies to overcome challenges, encompassing prophylactic and therapeutic vaccine research, regulatory considerations, and safety protocols. Utilizing advanced methodologies, including PBPK modeling, machine learning, artificial intelligence, and causal inference, we can amplify our comprehension and decision-making capabilities in this intricate domain. This narrative review aims to shed light on diverse approaches and ongoing advancements, this review aims to foster progress in antiviral therapy for pregnant women, improving maternal and fetal health outcomes.

Stabilized trimeric peptide immunogens of the complete HIV-1 gp41 N-heptad repeat and their use as HIV-1 vaccine candidates

Efforts to develop an HIV-1 vaccine include those focusing on conserved structural elements as the target of broadly neutralizing monoclonal antibodies. MAb D5 binds to a highly conserved hydrophobic pocket on the gp41 N-heptad repeat (NHR) coiled coil and neutralizes through prevention of viral fusion and entry. Assessment of 17-mer and 36-mer NHR peptides presenting the D5 epitope in rodent immunogenicity studies showed that the longer peptide elicited higher titers of neutralizing antibodies, suggesting that neutralizing epitopes outside of the D5 pocket may exist. Although the magnitude and breadth of neutralization elicited by NHR-targeting antigens are lower than that observed for antibodies directed to other epitopes on the envelope glycoprotein complex, it has been shown that NHR-directed antibodies are potentiated in TZM-bl cells containing the FcγRI receptor. Herein, we report the design and evaluation of covalently stabilized trimeric 51-mer peptides encompassing the complete gp41 NHR. We demonstrate that these peptide trimers function as effective antiviral entry inhibitors and retain the ability to present the D5 epitope. We further demonstrate in rodent and nonhuman primate immunization studies that our 51-mer constructs elicit a broader repertoire of neutralizing antibody and improved cross-clade neutralization of primary HIV-1 isolates relative to 17-mer and 36-mer NHR peptides in A3R5 and FcγR1-enhanced TZM-bl assays. These results demonstrate that sensitive neutralization assays can be used for structural enhancement of moderately potent neutralizing epitopes. Finally, we present expanded trimeric peptide designs which include unique low-molecular-weight scaffolds that provide versatility in our immunogen presentation strategy.

The molecular immune modulator adenosine deaminase-1 enhances HIV specific humoral and cellular responses to a native-like HIV envelope trimer DNA vaccine

There is currently no prophylactic vaccine available for human immunodeficiency virus (HIV). Research efforts have resulted in improved immunogens that mimic the native envelope (Env) glycoprotein structure. Recently, a novel triple tandem trimer (TTT) platform has been used to generate a plasmid encoding Env immunogen (pBG505-TTT) that expresses only as trimers, making it more suitable for nucleic acid vaccines. We have previously demonstrated that adenosine deaminase-1 (ADA-1) is critical to the T follicular helper (TFH) function and improves vaccine immune responses in vivo. In this study, we demonstrate that co-delivery of plasmid-encoded adenosine deaminase 1 (pADA) with pBG505-TTT enhances the magnitude, durability, isotype switching and functionality of HIV-specific antibodies in a dose-sparing manner. Co-delivery of the molecular immune modulator ADA-1 also enhances HIV-specific T cell polyfunctionality, activation, and degranulation as well as memory B cell responses. These data demonstrate that pADA enhances HIV-specific cellular and humoral immunity, making ADA-1 a promising immune modulator for HIV-targeting vaccines.

CoPoP liposomes displaying stabilized clade C HIV-1 Env elicit tier 2 multiclade neutralization in rabbits

One of the strategies towards an effective HIV-1 vaccine is to elicit broadly neutralizing antibody responses that target the high HIV-1 Env diversity. Here, we present an HIV-1 vaccine candidate that consists of cobalt porphyrin-phospholipid (CoPoP) liposomes decorated with repaired and stabilized clade C HIV-1 Env trimers in a prefusion conformation. These particles exhibit high HIV-1 Env trimer decoration, serum stability and bind broadly neutralizing antibodies. Three sequential immunizations of female rabbits with CoPoP liposomes displaying a different clade C HIV-1 gp140 trimer at each dosing generate high HIV-1 Env-specific antibody responses. Additionally, serum neutralization is detectable against 18 of 20 multiclade tier 2 HIV-1 strains. Furthermore, the peak antibody titers induced by CoPoP liposomes can be recalled by subsequent heterologous immunization with Ad26-encoded membrane-bound stabilized Env antigens. Hence, a CoPoP liposome-based HIV-1 vaccine that can generate cross-clade neutralizing antibody immunity could potentially be a component of an efficacious HIV-1 vaccine.

The Question of HIV Vaccine: Why Is a Solution Not Yet Available?

Ever since its discovery, human immunodeficiency virus type 1 (HIV-1) infection has remained a significant public health concern. The number of HIV-1 seropositive individuals currently stands at 40.1 million, yet definitive treatment for the virus is still unavailable on the market. Vaccination has proven to be a potent tool in combating infectious diseases, as evidenced by its success against other pathogens. However, despite ongoing efforts and research, the unique viral characteristics have prevented the development of an effective anti-HIV-1 vaccine. In this review, we aim to provide an historical overview of the various approaches attempted to create an effective anti-HIV-1 vaccine. Our objective is to explore the reasons why specific methods have failed to induce a protective immune response and to analyze the different modalities of immunogen presentation. This trial is registered with NCT05414786, NCT05471076, NCT04224701, and NCT01937455.

Prophylactic HIV-1 vaccine trials: past, present, and future

An effective HIV-1 vaccine is a global health priority but has remained elusive for more than 40 years. Key scientific hurdles that have hampered vaccine development are the unprecedented genetic variability of the virus, the rapid establishment of persistent viral latency, and the challenges associated with induction of broadly neutralising antibodies. Clinical trials have been instrumental in evaluating scientific concepts and testing vaccine strategies. This Review discusses lessons learned from clinical trials of HIV-1 vaccines, current technologies that are being explored, and future considerations in the development of a safe and effective HIV-1 vaccine.

Heterologous DNA Prime/Protein Boost Immunization Targeting Nef-Tat Fusion Antigen Induces Potent T-cell Activity and in vitro Anti-SCR HIV-1 Effects

BACKGROUND

Heterologous combinations in vaccine design are an effective approach to promote T cell activity and antiviral effects. The goal of this study was to compare the homologous and heterologous regimens targeting the Nef-Tat fusion antigen to develop a human immunodeficiency virus-1 (HIV-1) therapeutic vaccine candidate.

METHODS

At first, the DNA and protein constructs harboring HIV-1 Nef and the first exon of Tat as linked form (pcDNA-nef-tat and Nef-Tat protein) were prepared in large scale and high purity. The generation of the Nef-Tat protein was performed in the E. coli expression system using an IPTG inducer. Then, we evaluated and compared immune responses of homologous DNA prime/ DNA boost, homologous protein prime/ protein boost, and heterologous DNA prime/protein boost regimens in BALB/c mice. Finally, the ability of mice splenocytes to secret cytokines after exposure to single-cycle replicable (SCR) HIV-1 was compared between immunized and control groups in vitro.

RESULTS

The nef-tat gene was successfully subcloned in eukaryotic pcDNA3.1 (-) and prokaryotic pET-24a (+) expression vectors. The recombinant Nef-Tat protein was generated in the E. coli Rosetta strain under optimized conditions as a clear band of ~ 35 kDa detected on SDS-PAGE. Moreover, transfection of pcDNA-nef-tat into HEK-293T cells was successfully performed using Lipofectamine 2000, as confirmed by western blotting. The immunization studies showed that heterologous DNA prime/protein boost regimen could significantly elicit the highest levels of Ig- G2a, IFN-γ, and Granzyme B in mice as compared to homologous DNA/DNA and protein/protein regimens. Moreover, the secretion of IFN-γ was higher in DNA/protein regimens than in DNA/DNA and protein/protein regimens after exposure of mice splenocytes to SCR HIV-1 in vitro.

CONCLUSION

The chimeric HIV-1 Nef-Tat antigen was highly immunogenic, especially when applied in a heterologous prime/ boost regimen. This regimen could direct immune response toward cellular immunity (Th1 and CTL activity) and increase IFN-γ secretion after virus exposure.

Immunogenicity of Recombinant Lipid-Based Nanoparticle Vaccines: Danger Signal vs. Helping Hand

Infectious diseases are a predominant problem in human health. While the incidence of many pathogenic infections is controlled by vaccines, some pathogens still pose a challenging task for vaccine researchers. In order to face these challenges, the field of vaccine development has changed tremendously over the last few years. For non-replicating recombinant antigens, novel vaccine delivery systems that attempt to increase the immunogenicity by mimicking structural properties of pathogens are already approved for clinical applications. Lipid-based nanoparticles (LbNPs) of different natures are vesicles made of lipid layers with aqueous cavities, which may carry antigens and other biomolecules either displayed on the surface or encapsulated in the cavity. However, the efficacy profile of recombinant LbNP vaccines is not as high as that of live-attenuated ones. This review gives a compendious picture of two approaches that affect the immunogenicity of recombinant LbNP vaccines: (i) the incorporation of immunostimulatory agents and (ii) the utilization of pre-existing or promiscuous cellular immunity, which might be beneficial for the development of tailored prophylactic and therapeutic LbNP vaccine candidates.

Evolution of HIV-1 envelope towards reduced neutralization sensitivity, as demonstrated by contemporary HIV-1 subtype B from the United States

Subtype B HIV-1 has been the primary driver of the HIV-1 epidemic in the United States (U.S.) for over forty years and is also a prominent subtype in the Americas, Europe, Australia, the Middle East and North Africa. In this study, the neutralization profiles of contemporary subtype B Envs from the U.S. were assessed to characterize changes in neutralization sensitivities over time. We generated a panel of 30 contemporary pseudoviruses (PSVs) and demonstrated continued diversification of subtype B Env from the 1980s up to 2018. Neutralization sensitivities of the contemporary subtype B PSVs were characterized using 31 neutralizing antibodies (NAbs) and were compared with strains from earlier in the HIV-1 pandemic. A significant reduction in Env neutralization sensitivity was observed for 27 out of 31 NAbs for the contemporary as compared to earlier-decade subtype B PSVs. A decline in neutralization sensitivity was observed across all Env domains; the NAbs that were most potent early in the pandemic suffered the greatest decline in potency over time. A meta-analysis demonstrated this trend across multiple subtypes. As HIV-1 Env diversification continues, changes in Env antigenicity and neutralization sensitivity should continue to be evaluated to inform the development of improved vaccine and antibody products to prevent and treat HIV-1.

Conjugation of HIV-1 envelope to hepatitis B surface antigen alters vaccine responses in rhesus macaques

An effective HIV-1 vaccine remains a critical unmet need for ending the AIDS epidemic. Vaccine trials conducted to date have suggested the need to increase the durability and functionality of vaccine-elicited antibodies to improve efficacy. We hypothesized that a conjugate vaccine based on the learned response to immunization with hepatitis B virus could be utilized to expand T cell help and improve antibody production against HIV-1. To test this, we developed an innovative conjugate vaccine regimen that used a modified vaccinia virus Ankara (MVA) co-expressing HIV-1 envelope (Env) and the hepatitis B virus surface antigen (HBsAg) as a prime, followed by two Env-HBsAg conjugate protein boosts. We compared the immunogenicity of this conjugate regimen to matched HIV-1 Env-only vaccines in two groups of 5 juvenile rhesus macaques previously immunized with hepatitis B vaccines in infancy. We found expansion of both HIV-1 and HBsAg-specific circulating T follicular helper cells and elevated serum levels of CXCL13, a marker for germinal center activity, after boosting with HBsAg-Env conjugate antigens in comparison to Env alone. The conjugate vaccine elicited higher levels of antibodies binding to select HIV Env antigens, but we did not observe significant improvement in antibody functionality, durability, maturation, or B cell clonal expansion. These data suggests that conjugate vaccination can engage both HIV-1 Env and HBsAg specific T cell help and modify antibody responses at early time points, but more research is needed to understand how to leverage this strategy to improve the durability and efficacy of next-generation HIV vaccines.

Modulation of immune responses to liposomal vaccines by intrastructural help

The encapsulation of HIV-unrelated T helper peptides into liposomal vaccines presenting trimers of the HIV-1 envelope glycoprotein (Env) on the surface (T helper liposomes) may recruit heterologous T cells to provide help for Env-specific B cells. This mechanism called intrastructural help can modulate the HIV-specific humoral immune response. In this study, we used cationic T helper liposomes to induce intrastructural help effects in a small animal model. The liposomes were functionalized with Env trimers by a tag-free approach designed to enable a simplified GMP production. The pre-fusion conformation of the conjugated Env trimers was verified by immunogold electron microscopy (EM) imaging and flow cytometry. The liposomes induced strong activation of Env-specific B cells in vitro. In comparison to previously established anionic liposomes, cationic T helper liposomes were superior in CD4+ T cell activation after uptake by dendritic cells. Moreover, the T helper liposomes were able to target Env-specific B cells in secondary lymphoid organs after intramuscular injection. We also observed efficient T helper cell activation and proliferation in co-cultures with Env-specific B cells in the presence of cationic T helper liposomes. Mouse immunization experiments with cationic T helper liposomes further revealed a modulation of the Env-specific IgG subtype distribution and enhancement of the longevity of antibody responses by ovalbumin- and Hepatitis B (HBV)-specific T cell help. Thus, clinical evaluation of the concept of intrastructural help seems warranted.

In Vivo Treatment with Insulin-like Growth Factor 1 Reduces CCR5 Expression on Vaccine-Induced Activated CD4+ T-Cells

At the heart of the DNA/ALVAC/gp120/alum vaccine's efficacy in the absence of neutralizing antibodies is a delicate balance of pro- and anti-inflammatory immune responses that effectively decreases the risk of SIVmac251 acquisition in macaques. Vaccine efficacy is linked to antibodies recognizing the V2 helical conformation, DC-10 tolerogenic dendritic cells eliciting the clearance of apoptotic cells via efferocytosis, and CCR5 downregulation on vaccine-induced gut homing CD4+ cells. RAS activation is also linked to vaccine efficacy, which prompted the testing of IGF-1, a potent inducer of RAS activation with vaccination. We found that IGF-1 changed the hierarchy of V1/V2 epitope recognition and decreased both ADCC specific for helical V2 and efferocytosis. Remarkably, IGF-1 also reduced the expression of CCR5 on vaccine-induced CD4+ gut-homing T-cells, compensating for its negative effect on ADCC and efferocytosis and resulting in equivalent vaccine efficacy (71% with IGF-1 and 69% without).

HIV infection

The AIDS epidemic has been a global public health issue for more than 40 years and has resulted in ~40 million deaths. AIDS is caused by the retrovirus, HIV-1, which is transmitted via body fluids and secretions. After infection, the virus invades host cells by attaching to CD4 receptors and thereafter one of two major chemokine coreceptors, CCR5 or CXCR4, destroying the host cell, most often a T lymphocyte, as it replicates. If unchecked this can lead to an immune-deficient state and demise over a period of ~2-10 years. The discovery and global roll-out of rapid diagnostics and effective antiretroviral therapy led to a large reduction in mortality and morbidity and to an expanding group of individuals requiring lifelong viral suppressive therapy. Viral suppression eliminates sexual transmission of the virus and greatly improves health outcomes. HIV infection, although still stigmatized, is now a chronic and manageable condition. Ultimate epidemic control will require prevention and treatment to be made available, affordable and accessible for all. Furthermore, the focus should be heavily oriented towards long-term well-being, care for multimorbidity and good quality of life. Intense research efforts continue for therapeutic and/or preventive vaccines, novel immunotherapies and a cure.

Enhancement of Neutralization Responses through Sequential Immunization of Stable Env Trimers Based on Consensus Sequences from Select Time Points by Mimicking Natural Infection

HIV-1 vaccines have been challenging to develop, partly due to the high level of genetic variation in its genome. Thus, a vaccine that can induce cross-reactive neutralization activities will be needed. Studies on the co-evolution of antibodies and viruses indicate that mimicking the natural infection is likely to induce broadly neutralizing antibodies (bnAbs). We generated the consensus Env sequence for each time point in subject CH505, who developed broad neutralization activities, and selected five critical time points before broad neutralization was detected. These consensus sequences were designed to express stable Env trimers. Priming with the transmitted/founder Env timer and sequential boosting with these consensus Env trimers from different time points induced broader and more potent neutralizing activities than the BG505 Env trimer in guinea pigs. Analysis of the neutralization profiles showed that sequential immunization of Env trimers favored nAbs with gp120/gp41 interface specificity while the BG505 Env trimer favored nAbs with V2 specificity. The unique features such as consensus sequences, stable Env trimers and the sequential immunization to mimic natural infection likely has allowed the induction of improved neutralization responses.

Advances in the treatment and prevention of HIV: what you need to know

The global epidemic of HIV/AIDs has seen many advances in the development of effective treatments, including antiretroviral therapy that provides increasing sustained viral suppression, robust immune reconstitution and fewer side effects than before. Early HIV treatment regimens were notoriously complex, comprising up to 22 pills that needed to be taken at different times of the day. However, the advent of a single fixed dose combination drug formation simplified the treatment regimen so this could be taken once daily. Novel drugs are constantly being developed to provide better tolerated medications with robust, sustained viral suppression and immune reconstitution; these include long-acting injectables and implants, and preventative treatments for pre-exposure prophylaxis. This article provides an overview of emerging therapeutics for the treatment and prevention of HIV infection.

The Mechanism of bnAb Production and Its Application in Mutable Virus Broad-Spectrum Vaccines: Inspiration from HIV-1 Broad Neutralization Research

Elite controllers among HIV-1-infected individuals have demonstrated a stronger ability to control the viral load in their bodies. Scientists have isolated antibodies with strong neutralizing ability from these individuals, which can neutralize HIV-1 variations; these are known as broadly neutralizing antibodies. The nucleic acid of some viruses will constantly mutate during replication (such as SARS-CoV-2), which will reduce the protective ability of the corresponding vaccines. The immune escape caused by this mutation is the most severe challenge faced by humans in the battle against the virus. Therefore, developing broad-spectrum vaccines that can induce broadly neutralizing antibodies against various viruses and their mutated strains is the best way to combat virus mutations. Exploring the mechanism by which the human immune system produces broadly neutralizing antibodies and its induction strategies is crucial in the design process of broad-spectrum vaccines.

Towards Novel HIV-1 Serodiagnostic Tests without Vaccine-Induced Seroreactivity

Vaccine-induced seroreactivity/positivity (VISR/P) poses a significant and common challenge to HIV vaccine implementation, as up to 95% of vaccine recipients may be misclassified as having HIV infection by current HIV screening and confirmatory serological assays. We investigated whether internal HIV proteins could be used to overcome VISR and discovered a set of 4 antigens (gp41 endodomain, p31 integrase, p17 matrix protein, and Nef) that are recognized by antibodies produced in individuals with HIV infection but not in vaccinated individuals. When evaluated in a multiplex double-antigen bridging ELISA, this antigen combination had specificities of 98.1% prevaccination and 97.1% postvaccination, demonstrating the assay is minimally impacted by vaccine-induced antibodies. The sensitivity was 98.5%, further increasing to 99.7% when p24 antigen testing was included. Results were similar across HIV-1 clades. Although more technical advancements will be desired, this research provides the groundwork for the development of new fourth-generation HIV tests unaffected by VISR. IMPORTANCE While the detection of HIV infection is accomplished by several methods, the most common are serological tests that detect host antibodies produced in response to viral infection. However, the use of current serological tests may present a significant challenge to the adoption of an HIV vaccine in the future because the antibodies to HIV antigens detected in currently available tests also tend to be included as antigens in the HIV vaccines in development. The use of these serological tests may thus result in the misclassification of vaccinated HIV-negative individuals, which can have potential for significant harms for individuals and could prevent the widespread adoption and implementation of HIV vaccines. Our study aimed to identify and evaluate target antigens for inclusion in new serological tests that can be used to identify HIV infections without interference from vaccine-induced antibodies but also fit within existing platforms for HIV diagnostics.

Recent advances in CD8+ T cell-based immune therapies for HIV cure

Achieving a cure for HIV infection is a global priority. There is substantial evidence supporting a central role for CD8⁺ T cells in the natural control of HIV, suggesting the rationale that these cells may be exploited to achieve remission or cure of this infection. In this work, we review the major challenges for achieving an HIV cure, the models of HIV remission, and the mechanisms of HIV control mediated by CD8⁺ T cells. In addition, we discuss strategies based on this cell population that could be used in the search for an HIV cure. Finally, we analyze the current challenges and perspectives to translate this basic knowledge toward scalable HIV cure strategies.

Optimizing the Production of gp145, an HIV-1 Envelope Glycoprotein Vaccine Candidate and Its Encapsulation in Guanosine Microparticles

We have developed a pipeline to express, purify, and characterize HIV envelope protein (Env) gp145 from Chinese hamster ovary cells, to accelerate the production of a promising vaccine candidate. First in shake flasks, then in bioreactors, we optimized the growth conditions. By adjusting the pH to 6.8, we increased expression levels to 101 mg/L in a 50 L bioreactor, nearly twice the previously reported titer value. A battery of analytical methods was developed in accordance with current good manufacturing practices to ensure a quality biopharmaceutical. Imaged capillary isoelectric focusing verified proper glycosylation of gp145; dynamic light scattering confirmed the trimeric arrangement; and bio-layer interferometry and circular dichroism analysis demonstrated native-like properties (i.e., antibody binding and secondary structure). MALDI-TOF mass spectrometry was used as a multi-attribute platform for accurate mass determination, glycans analysis, and protein identification. Our robust analysis demonstrates that our gp145 product is very similar to a reference standard and emphasizes the importance of accurate characterization of a highly heterogeneous immunogen for the development of an effective vaccine. Finally, we present a novel guanosine microparticle with gp145 encapsulated and displayed on its surface. The unique properties of our gp145 microparticle make it amenable to use in future preclinical and clinical trials.

Pharmacophore Variants of the Macrocyclic Peptide Triazole Inactivator of HIV-1 Env

Previously we established a family of macrocyclic peptide triazoles (cPTs) that inactivate the Env protein complex of HIV-1, and identified the pharmacophore that engages Env's receptor binding pocket. Here, we examined the hypothesis that the side chains of both components of the triazole Pro - Trp segment of cPT pharmacophore work in tandem to make intimate contacts with two proximal subsites of the overall CD4 binding site of gp120 to stabilize binding and function. Variations of the triazole Pro R group, which previously had been significantly optimized, led to identification of a variant MG-II-20 that contains a pyrazole substitution. MG-II-20 has improved functional properties over previously examined variants, with Kd for gp120 in the nM range. In contrast, new variants of the Trp indole side chain, with either methyl- or bromo- components appended, had disruptive effects on gp120 binding, reflecting the sensitivity of function to changes in this component of the encounter complex. Plausible in silico models of cPT:gp120 complex structures were obtained that are consistent with the overall hypothesisof occupancy by the triazole Pro and Trp side chains, respectively, into the β20/21 and Phe43 sub-cavities. The overall results strengthen the definition of the cPT-Env inactivator binding site and provide a new lead composition (MG-II-20) as well as structure-function findings to guide future HIV-1 Env inactivator design.

Glycan masking in vaccine design: Targets, immunogens and applications

Glycan masking is a novel technique in reverse vaccinology in which sugar chains (glycans) are added on the surface of immunogen candidates to hide regions of low interest and thus focus the immune system on highly therapeutic epitopes. This shielding strategy is inspired by viruses such as influenza and HIV, which are able to escape the immune system by incorporating additional glycosylation and preventing the binding of therapeutic antibodies. Interestingly, the glycan masking technique is mainly used in vaccine design to fight the same viruses that naturally use glycans to evade the immune system. In this review we report the major successes obtained with the glycan masking technique in epitope-focused vaccine design. We focus on the choice of the target antigen, the strategy for immunogen design and the relevance of the carrier vector to induce a strong immune response. Moreover, we will elucidate the different applications that can be accomplished with glycan masking, such as shifting the immune response from hyper-variable epitopes to more conserved ones, focusing the response on known therapeutic epitopes, broadening the response to different viral strains/sub-types and altering the antigen immunogenicity to elicit higher or lower immune response, as desired.

Nano-vaccines for gene delivery against HIV-1 infection

INTRODUCTION

Over the last four decades, human immunodeficiency virus type 1 (HIV-1) infection has been a major public health concern. It is acknowledged that an effective vaccine remains the best hope for eliminating the HIV-1 pandemic. The prophylaxis of HIV-1 infection remains a central theme because of the absence of an available HIV-1 vaccine. The incapability of conventional delivery strategies to induce potent immunity is a crucial task to overcome and ultimately lead to a major obstacle in HIV-1 vaccine research.

AREAS COVERED

The literature search was conducted in the following databases: PubMed, Web of Science, and Embase. Nano-platforms based vaccines have proven prophylaxis of various diseases for effectively activating the immune system. Nano-vaccines, including non-viral and viral vectored nano-vaccines, are in a position to improve the effectiveness of HIV-1 antigen delivery and enhance the innate and adaptive immune responses against HIV-1. Compared to traditional vaccination strategies, genetic immunization can elicit a long-term immune response to provide protective immunity for HIV-1 prevention.

EXPERT OPINION

The research progress on nano-vaccines for gene delivery against HIV-1 was discussed. The vaccine strategies based on nano-platforms that are being applied to stimulate effective HIV-1-specific cellular and humoral immune responses were particularly emphasized.

Safety of COVID-19 Vaccines in Patients with Autoimmune Diseases, in Patients with Cardiac Issues, and in the Healthy Population

The coronavirus disease 2019 (COVID-19) has been a challenge for the whole world since the beginning of 2020, and COVID-19 vaccines were considered crucial for disease eradication. Instead of producing classic vaccines, some companies pointed to develop products that mainly function by inducing, into the host, the production of the antigenic protein of SARS-CoV-2 called Spike, injecting an instruction based on RNA or a DNA sequence. Here, we aim to give an overview of the safety profile and the actual known adverse effects of these products in relationship with their mechanism of action. We discuss the use and safety of these products in at-risk people, especially those with autoimmune diseases or with previously reported myocarditis, but also in the general population. We debate the real necessity of administering these products with unclear long-term effects to at-risk people with autoimmune conditions, as well as to healthy people, at the time of omicron variants. This, considering the existence of therapeutic interventions, much more clearly assessed at present compared to the past, and the relatively lower aggressive nature of the new viral variants.

Scratching the Surface Takes a Toll: Immune Recognition of Viral Proteins by Surface Toll-like Receptors

Early innate viral recognition by the host is critical for the rapid response and subsequent clearance of an infection. Innate immune cells patrol sites of infection to detect and respond to invading microorganisms including viruses. Surface Toll-like receptors (TLRs) are a group of pattern recognition receptors (PRRs) that can be activated by viruses even before the host cell becomes infected. However, the early activation of surface TLRs by viruses can lead to viral clearance by the host or promote pathogenesis. Thus, a plethora of research has attempted to identify specific viral ligands that bind to surface TLRs and mediate progression of viral infection. Herein, we will discuss the past two decades of research that have identified specific viral proteins recognized by cell surface-associated TLRs, how these viral proteins and host surface TLR interactions affect the host inflammatory response and outcome of infection, and address why controversy remains regarding host surface TLR recognition of viral proteins.

Recent HIV Infection: Diagnosis and Public Health Implications

The early period of infection with human immunodeficiency virus (HIV) has been associated with higher infectiousness and, consequently, with more transmission events. Over the last 30 years, assays have been developed that can detect viral and immune biomarkers during the first months of HIV infection. Some of them depend on the functional properties of antibodies including their changing titers or the increasing strength of binding with antigens over time. There have been efforts to estimate HIV incidence using antibody-based assays that detect recent HIV infection along with other laboratory and clinical information. Moreover, some interventions are based on the identification of people who were recently infected by HIV. This review summarizes the evolution of efforts to develop assays for the detection of recent HIV infection and to use these assays for the cross-sectional estimation of HIV incidence or for prevention purposes.

Vaccines against Emerging and Neglected Infectious Diseases: An Overview

Neglected Tropical Diseases (NTDs) are a group of diseases that are highly prevalent in tropical and subtropical regions, and closely associated with poverty and marginalized populations. Infectious diseases affect over 1.6 billion people annually, and vaccines are the best prophylactic tool against them. Along with NTDs, emerging and reemerging infectious diseases also threaten global public health, as they can unpredictably result in pandemics. The recent advances in vaccinology allowed the development and licensing of new vaccine platforms that can target and prevent these diseases. In this work, we discuss the advances in vaccinology and some of the difficulties found in the vaccine development pipeline for selected NTDs and emerging and reemerging infectious diseases, including HIV, Dengue, Ebola, Chagas disease, malaria, leishmaniasis, zika, and chikungunya.

V2 hotspot optimized MVA vaccine expressing stabilized HIV-1 Clade C envelope Gp140 delays acquisition of heterologous Clade C Tier 2 challenges in Mamu-A*01 negative Rhesus Macaques

Stabilized HIV envelope (Env) trimeric protein immunogens have been shown to induce strong autologous neutralizing antibody response. However, there is limited data on the immunogenicity and efficacy of stabilized Env expressed by a viral vector-based immunogen. Here, we compared the immunogenicity and efficacy of two modified vaccinia Ankara (MVA) vaccines based on variable loop 2 hotspot (V2 HS) optimized C.1086 envelope (Env) sequences, one expressing the membrane anchored gp150 (MVA-150) and the other expressing soluble uncleaved pre-fusion optimized (UFO) gp140 trimer (MVA-UFO) in a DNA prime/MVA boost approach against heterologous tier 2 SHIV1157ipd3N4 intrarectal challenges in rhesus macaques (RMs). Both MVA vaccines also expressed SIVmac239 Gag and form virus-like particles. The DNA vaccine expressed SIVmac239 Gag, C.1086 gp160 Env and rhesus CD40L as a built-in adjuvant. Additionally, all immunizations were administered intradermally (ID) to reduce induction of vaccine-specific IFNγ+ CD4 T cell responses. Our results showed that both MVA-150 and MVA-UFO vaccines induce comparable Env specific IgG responses in serum and rectal secretions. The vaccine-induced serum antibody showed ADCC and ADCVI activities against the challenge virus. Comparison with a previous study that used similar immunogens via intramuscular route (IM) showed that ID immunizations induced markedly lower SHIV specific CD4 and CD8 T cell responses compared to IM immunizations. Following challenge, MVA-UFO vaccinated animals showed a significant delay in acquisition of SHIV1157ipd3N4 infection but only in Mamu-A*01 negative macaques with an estimated vaccine efficacy of 64% per exposure. The MVA-150 group also showed a trend (p=0.1) for delay in acquisition of SHIV infection with an estimated vaccine efficacy of 57%. The vaccine-induced IFNγ secreting CD8 T cell responses showed a direct association and CD4 T cells showed an inverse association with delay in acquisition of SHIV infection. These results demonstrated that both MVA-150 and MVA-UFO immunogens induce comparable humoral and cellular immunity and the latter provides marginally better protection against heterologous tier 2 SHIV infection. They also demonstrate that DNA/MVA vaccinations delivered by ID route induce better antibody and lower CD4 and CD8 T cell responses compared to IM.

Natural Immunity against HIV-1: Progression of Understanding after Association Studies

Natural immunity against HIV has been observed in many individuals in the world. Among them, a group of female sex workers enrolled in the Pumwani sex worker cohort remained HIV uninfected for more than 30 years despite high-risk sex work. Many studies have been carried out to understand this natural immunity to HIV in the hope to develop effective vaccines and preventions. This review focuses on two such examples. These studies started from identifying immunogenetic or genetic associations with resistance to HIV acquisition, and followed up with an in-depth investigation to understand the biological relevance of the correlations of protection, and to develop and test novel vaccines and preventions.

Containing the spread of COVID-19 virus facing to its high mutation rate: approach to intervention using a nonspecific way of blocking its entry into the cells

Viruses have multiple mutation rates that are higher than any other member of the kingdom of life. This gives them the ability to evolve, even within the course of a single infection, and to evade multiple host defenses, thereby impacting pathogenesis. Additionally, there are also interplays between mutation and recombination and the high multiplicity of infection (MOI) that enhance viral adaptability and increase levels of recombination leading to complex and conflicting effects on genome selection, and the net results is difficult to predict. Recently, the outbreak of COVID-19 virus represents a pandemic threat that has been declared a public health emergency of international concern. Up to present, however, due to the high mutation rate of COVID-19 virus, there are no effective procedures to contain the spread of this virus across the globe. For such a purpose, there is then an urgent need to explore new approaches. As an opinion, the present approach emphasizes on (a) the use of a nonspecific way of blocking the entry of COVID-19 virus as well as its variants into the cells via a therapeutic biocompatible compound (ideally, "in a pill") targeting its spike (S) glycoprotein; and (b) the construction of expression vectors via the glycosyl-phosphatidylinositol, GPI, anchor for studying intermolecular interactions between the spike S of COVID-19 virus as well as its variants and the angiotensin-converting enzyme 2 (ACE2) of its host receptor for checking the efficacy of any therapeutic biocompatible compound of the nonspecific way of blocking. Such antiviral drug would be safer than the ACE1 and ACE2 inhibitors/angiotensin receptor blockers, and recombinant human ACE2 as well as nucleoside analogs or protease inhibitors used for fighting the spread of the virus inside the cells, and it would also be used as a universal one for any eventual future pandemic related to viruses, especially the RNA viruses with high mutation rates.

High-Throughput B Cell Epitope Determination by Next-Generation Sequencing

Development of novel technologies for the discovery of human monoclonal antibodies has proven invaluable in the fight against infectious diseases. Among the diverse antibody repertoires elicited by infection or vaccination, often only rare antibodies targeting specific epitopes of interest are of potential therapeutic value. Current antibody discovery efforts are capable of identifying B cells specific for a given antigen; however, epitope specificity information is usually only obtained after subsequent monoclonal antibody production and characterization. Here we describe LIBRA-seq with epitope mapping, a next-generation sequencing technology that enables residue-level epitope determination for thousands of single B cells simultaneously. By utilizing an antigen panel of point mutants within the HIV-1 Env glycoprotein, we identified and confirmed antibodies targeting multiple sites of vulnerability on Env, including the CD4-binding site and the V3-glycan site. LIBRA-seq with epitope mapping is an efficient tool for high-throughput identification of antibodies against epitopes of interest on a given antigen target.

Structure-guided envelope trimer design in HIV-1 vaccine development: a narrative review

INTRODUCTION

The development of a human immunodeficiency virus 1 (HIV-1) vaccine remains a formidable challenge. An effective vaccine likely requires the induction of broadly neutralizing antibodies (bNAbs), which likely involves the use of native-like HIV-1 envelope (Env) trimers at some or all stages of vaccination. Development of such trimers has been very difficult, but much progress has been made in the past decade, starting with the BG505 SOSIP trimer, elucidation of its atomic structure and implementing subsequent design iterations. This progress facilitated understanding the weaknesses of the Env trimer, fuelled structure-guided HIV-1 vaccine design and assisted in the development of new vaccine designs. This review summarizes the relevant literature focusing on studies using structural biology to reveal and define HIV-1 Env sites of vulnerability; to improve Env trimers, by creating more stable versions; understanding antibody responses in preclinical vaccination studies at the atomic level; understanding the glycan shield; and to improve "on-target" antibody responses versus "off-target" responses.

METHODS

The authors conducted a narrative review of recently published articles that made a major contribution to HIV-1 structural biology and vaccine design efforts between the years 2000 and 2021.

DISCUSSION

The field of structural biology is evolving at an unprecedented pace, where cryo-electron microscopy (cryo-EM) and X-ray crystallography provide complementary information. Resolving protein structures is necessary for defining which Env surfaces are accessible for the immune system and can be targeted by neutralizing antibodies. Recently developed techniques, such as electron microscopy-based polyclonal epitope mapping (EMPEM) are revolutionizing the way we are analysing immune responses and shed light on the immunodominant targets on new vaccine immunogens. Such information accelerates iterative vaccine design; for example, by reducing undesirable off-target responses, while improving immunogens to drive the more desirable on-target responses.

CONCLUSIONS

Resolving high-resolution structures of the HIV-1 Env trimer was instrumental in understanding and improving recombinant HIV-1 Env trimers that mimic the structure of viral HIV-1 Env spikes. Newly emerging techniques in structural biology are aiding vaccine design efforts and improving immunogens. The role of structural biology in HIV-1 vaccine design has indeed become very prominent and is unlikely to diminish any time soon.