Therapeutic conserved elements (CE) DNA vaccine induces strong T-cell responses against highly conserved viral sequences during simian-human immunodeficiency virus infection

Efficient ex vivo expansion of conserved element vaccine-specific CD8+ T-cells from SHIV-infected, ART-suppressed nonhuman primates

HIV-specific T cells are necessary for control of HIV-1 replication but are largely insufficient for viral clearance. This is due in part to these cells' recognition of immunodominant but variable regions of the virus, which facilitates viral escape via mutations that do not incur viral fitness costs. HIV-specific T cells targeting conserved viral elements are associated with viral control but are relatively infrequent in people living with HIV (PLWH). The goal of this study was to increase the number of these cells via an ex vivo cell manufacturing approach derived from our clinically-validated HIV-specific expanded T-cell (HXTC) process. Using a nonhuman primate (NHP) model of HIV infection, we sought to determine i) the feasibility of manufacturing ex vivo-expanded virus-specific T cells targeting viral conserved elements (CE, CE-XTCs), ii) the in vivo safety of these products, and iii) the impact of simian/human immunodeficiency virus (SHIV) challenge on their expansion, activity, and function. NHP CE-XTCs expanded up to 10-fold following co-culture with the combination of primary dendritic cells (DCs), PHA blasts pulsed with CE peptides, irradiated GM-K562 feeder cells, and autologous T cells from CE-vaccinated NHP. The resulting CE-XTC products contained high frequencies of CE-specific, polyfunctional T cells. However, consistent with prior studies with human HXTC and these cells' predominant CD8+ effector phenotype, we did not observe significant differences in CE-XTC persistence or SHIV acquisition in two CE-XTC-infused NHP compared to two control NHP. These data support the safety and feasibility of our approach and underscore the need for continued development of CE-XTC and similar cell-based strategies to redirect and increase the potency of cellular virus-specific adaptive immune responses.

In silico design of a TLR4-mediating multiepitope chimeric vaccine against amyotrophic lateral sclerosis via advanced immunoinformatics

Amyotrophic lateral sclerosis (ALS) is the most prevalent motor neuron disorder worldwide. In ALS, progressing disease can result from misfolding and aggregation of superoxide dismutase-1 (SOD1) or TAR DNA-binding protein 43 kDa (TDP43). An efficient immunotherapy for ALS should spare intact SOD1 while eliminating its dysfunctional variant. We utilized advanced immunoinformatics to suggest a potential vaccine candidate against ALS by proposing a model of dynamic TLR4 mediation and induction of a specific Th2-biased shift against mutant SOD1, TDP43, and TRAF6, a protein that specifically interacts with dysfunctional SOD1. SOD1, TDP43, and TRAF6 were retrieved in FASTA. Immune Epitopes Database and CTLpred suggested T/B-cell epitopes from disease-specific regions of selected antigens. A TLR4-mediating adjuvant, RS01, was used. Sequences were assembled via suitable linkers. Tertiary structure of the protein was calculated. Refined protein structure and physicochemical features of the 3D structure were verified in silico. Differential immune induction was assessed via C-ImmSim. GROningen MAchine for Chemical Simulation was used to assess evolution of the docked vaccine-TLR4 complex in blood. Our protein showed high structural quality and was nonallergenic and immune inducing. Also, the vaccine-TLR4 complex stability was verified by RMSD, RMSF, gyration, and visual analyses of the molecular dynamic trajectory. Contact residues in the vaccine-TLR4 complex showed favorable binding energies. Immune stimulation analyses of the proposed candidate demonstrated a sustained memory cell response and a strong adaptive immune reaction. We proposed a potential vaccine candidate against ALS and verified its physicochemical and immune inducing features. Future studies should assess this vaccine in animal studies.

A novel DNA and protein combination COVID-19 vaccine formulation provides full protection against SARS-CoV-2 in rhesus macaques

The current study aims to develop a safe and highly immunogenic COVID-19 vaccine. The novel combination of a DNA vaccine encoding the full-length Spike (S) protein of SARS-CoV-2 and a recombinant S1 protein vaccine induced high level neutralizing antibody and T cell immune responses in both small and large animal models. More significantly, the co-delivery of DNA and protein components at the same time elicited full protection against intratracheal challenge of SARS-CoV-2 viruses in immunized rhesus macaques. As both DNA and protein vaccines have been proven safe in previous human studies, and DNA vaccines are capable of eliciting germinal center B cell development, which is critical for high-affinity memory B cell responses, the DNA and protein co-delivery vaccine approach has great potential to serve as a safe and effective approach to develop COVID-19 vaccines that provide long-term protection.

Effects of therapeutic vaccination on the control of SIV in rhesus macaques with variable responsiveness to antiretroviral drugs

A therapeutic vaccine that induces lasting control of HIV infection could eliminate the need for lifelong adherence to antiretroviral therapy. This study investigated a therapeutic DNA vaccine delivered with a single adjuvant or a novel combination of adjuvants to augment T cell immunity in the blood and gut-associated lymphoid tissue in SIV-infected rhesus macaques. Animals that received DNA vaccines expressing SIV proteins, combined with plasmids expressing adjuvants designed to increase peripheral and mucosal T cell responses, including the catalytic subunit of the E. coli heat-labile enterotoxin, IL-12, IL-33, retinaldehyde dehydrogenase 2, soluble PD-1 and soluble CD80, were compared to mock-vaccinated controls. Following treatment interruption, macaques exhibited variable levels of viral rebound, with four animals from the vaccinated groups and one animal from the control group controlling virus at median levels of 10³ RNA copies/ml or lower (controllers) and nine animals, among all groups, exhibiting immediate viral rebound and median viral loads greater than 10³ RNA copies/ml (non-controllers). Although there was no significant difference between the vaccinated and control groups in protection from viral rebound, the variable virological outcomes during treatment interruption enabled an examination of immune correlates of viral replication in controllers versus non-controllers regardless of vaccination status. Lower viral burden in controllers correlated with increased polyfunctional SIV-specific CD8⁺ T cells in mesenteric lymph nodes and blood prior to and during treatment interruption. Notably, higher frequencies of colonic CD4⁺ T cells and lower Th17/Treg ratios prior to infection in controllers correlated with improved responses to ART and control of viral rebound. These results indicate that mucosal immune responses, present prior to infection, can influence efficacy of antiretroviral therapy and the outcome of immunotherapeutic vaccination, suggesting that therapies capable of modulating host mucosal responses may be needed to achieve HIV cure.

Pediatric HIV: the Potential of Immune Therapeutics to Achieve Viral Remission and Functional Cure

PURPOSE OF REVIEW

In the absence of antiretroviral therapy (ART), more than 50% of perinatally HIV-infected children die by 2 years of age. Early ART from infancy is therefore a global recommendation and significantly improves immune health, child survival, and disease outcome. However, even early treatment does not prevent or eradicate the latent reservoir necessitating life-long ART. Adherence to life-long ART is challenging for children and longstanding ART during chronic HIV infection led to higher risks of non-AIDS co-morbidities and virologic failure in infected children. Thus, HIV-infected children are an important population for consideration for immune-based interventions to achieve ART-free remission and functional cure. This review summarizes how the uniqueness of the early life immune system can be harnessed for the development of ART-free remission and functional cure, which means complete virus control in absence of ART. In addition, recent advances in therapeutics in the HIV cure field and their potential for the treatment of pediatric HIV infections are discussed.

RECENT FINDINGS

Preclinical studies and clinical trials demonstrated that immune-based interventions target HIV replication, limit size of virus reservoir, maintain virus suppression, and delay time to virus rebound. However, these studies have been performed so far only in carefully selected HIV-infected adults, highlighting the need to evaluate the efficacy of immune-based therapeutics in HIV-infected children and to design interventions tailored to the early life maturing immune system. Immune-based therapeutics alone or in combination with ART should be actively explored as potential strategies to achieve viral remission and functional cure in HIV-infected pediatric populations.

Antiviral therapy for the sexually transmitted viruses: recent updates on vaccine development

INTRODUCTION

The sexually transmitted infections (STIs) caused by viruses including human T cell leukemia virus type-1 (HTLV-1), human immunodeficiency virus-1 (HIV-1), human simplex virus-2 (HSV-2), hepatitis C virus (HCV), hepatitis B virus (HBV), and human papillomavirus (HPV) are major public health issues. These infections can cause cancer or result in long-term health problems. Due to high prevalence of STIs, a safe and effective vaccine is required to overcome these fatal viruses.

AREAS COVERED

This review includes a comprehensive overview of the literatures relevant to vaccine development against the sexually transmitted viruses (STVs) using PubMed and Sciencedirect electronic search engines. Herein, we discuss the efforts directed toward development of effective vaccines using different laboratory animal models including mice, guinea pig or non-human primates in preclinical trials, and human in clinical trials with different phases.

EXPERT OPINION

There is no effective FDA approved vaccine against the sexually transmitted viruses (STVs) except for HBV and HPV as prophylactic vaccines. Many attempts are underway to develop vaccines against these viruses. There are several approaches for improving prophylactic or therapeutic vaccines such as heterologous prime/boost immunization, delivery system, administration route, adjuvants, etc. In this line, further studies can be helpful for understanding the immunobiology of STVs in human. Moreover, development of more relevant animal models is a worthy goal to induce effective immune responses in humans.

An Alphavirus-derived replicon RNA vaccine induces SARS-CoV-2 neutralizing antibody and T cell responses in mice and nonhuman primates

The coronavirus disease 2019 (COVID-19) pandemic, caused by infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is having a deleterious impact on health services and the global economy, highlighting the urgent need for an effective vaccine. Such a vaccine would need to rapidly confer protection after one or two doses and would need to be manufactured using components suitable for scale up. Here, we developed an Alphavirus-derived replicon RNA vaccine candidate, repRNA-CoV2S, encoding the SARS-CoV-2 spike (S) protein. The RNA replicons were formulated with lipid inorganic nanoparticles (LIONs) that were designed to enhance vaccine stability, delivery, and immunogenicity. We show that a single intramuscular injection of the LION/repRNA-CoV2S vaccine in mice elicited robust production of anti-SARS-CoV-2 S protein IgG antibody isotypes indicative of a type 1 T helper cell response. A prime/boost regimen induced potent T cell responses in mice including antigen-specific responses in the lung and spleen. Prime-only immunization of aged (17 months old) mice induced smaller immune responses compared to young mice, but this difference was abrogated by booster immunization. In nonhuman primates, prime-only immunization in one intramuscular injection site or prime/boost immunizations in five intramuscular injection sites elicited modest T cell responses and robust antibody responses. The antibody responses persisted for at least 70 days and neutralized SARS-CoV-2 at titers comparable to those in human serum samples collected from individuals convalescing from COVID-19. These data support further development of LION/repRNA-CoV2S as a vaccine candidate for prophylactic protection against SARS-CoV-2 infection.

Development and Preclinical Evaluation of an Integrase Defective Lentiviral Vector Vaccine Expressing the HIVACAT T Cell Immunogen in Mice

Cellular immune responses play a fundamental role in controlling viral replication and AIDS progression in human immunodeficiency virus (HIV)-infected subjects and in simian immunodeficiency virus (SIV)-infected macaques. Integrase defective lentiviral vector (IDLV) represents a promising vaccine candidate, inducing functional and durable immune responses in mice and non-human primates. Here, we designed HIV- and SIV-based IDLVs to express the HIVACAT T cell immunogen (HTI), a mosaic antigen designed to cover vulnerable sites in HIV-1 Gag, Pol, Vif, and Nef. We observed that HTI expression during lentiviral vector production interfered profoundly with IDLV particles release because of sequestration of both HIV- and SIV-Gag proteins in the cytoplasm of the vector-producing cells. However, modifications in IDLV design and vector production procedures greatly improved recovery of both HIV- and SIV-based IDLV-HTI. Immunization experiments in BALB/c mice showed that both IDLVs elicited HTI-specific T cell responses. However, immunization with HIV-based IDLV elicited also a T cell response toward exogenous HIV proteins in IDLV particles, suggesting that SIV-based IDLV may be a preferable platform to assess the induction of transgene-specific immune responses against rationally designed HIV structural antigens. These data support the further evaluation of IDLV as an effective platform of T cell immunogens for the development of an effective HIV vaccine.

Single-dose replicating RNA vaccine induces neutralizing antibodies against SARS-CoV-2 in nonhuman primates

The ongoing COVID-19 pandemic, caused by infection with SARS-CoV-2, is having a dramatic and deleterious impact on health services and the global economy. Grim public health statistics highlight the need for vaccines that can rapidly confer protection after a single dose and be manufactured using components suitable for scale-up and efficient distribution. In response, we have rapidly developed repRNA-CoV2S, a stable and highly immunogenic vaccine candidate comprised of an RNA replicon formulated with a novel Lipid InOrganic Nanoparticle (LION) designed to enhance vaccine stability, delivery and immunogenicity. We show that intramuscular injection of LION/repRNA-CoV2S elicits robust anti-SARS-CoV-2 spike protein IgG antibody isotypes indicative of a Type 1 T helper response as well as potent T cell responses in mice. Importantly, a single-dose administration in nonhuman primates elicited antibody responses that potently neutralized SARS-CoV-2. These data support further development of LION/repRNA-CoV2S as a vaccine candidate for prophylactic protection from SARS-CoV-2 infection.

Therapeutic vaccination with IDLV-SIV-Gag results in durable viremia control in chronically SHIV-infected macaques

Despite incredible scientific efforts, there is no cure for HIV infection. While antiretroviral treatment (ART) can help control the virus and prevent transmission, it cannot eradicate HIV from viral reservoirs established before the initiation of therapy. Further, HIV-infected individuals reliably exhibit viral rebound when ART is interrupted, suggesting that the host immune response fails to control viral replication in persistent reservoirs. Therapeutic vaccines are one current approach to improving antiviral host immune responses and enhance long term virus control. In the present study, we used an integrase defective lentiviral vector (IDLV) expressing SIV-Gag to boost anti-Gag specific immune responses in macaques chronically infected with the tier-2 SHIV-1157(QNE)Y173H. A single immunization with IDLV-SIV-Gag induced durable (>20 weeks) virus control in 55% of the vaccinated macaques, correlating with an increased magnitude of SIV-Gag specific CD8+ T-cell responses. IDLV-based therapeutic vaccines are therefore an effective approach to improve virus specific CD8+ T-cell responses and mediate virus control.

Dendrigraft poly-L-lysines delivery of DNA vaccine effectively enhances the immunogenic responses against H9N2 avian influenza virus infection in chickens

Biodegradable nanomaterials can protect antigens from degradation, promote cellular absorption, and enhance immune responses. We constructed a eukaryotic plasmid [pCAGGS-opti441-hemagglutinin (HA)] by inserting the optimized HA gene fragment of H9N2 AIV into the pCAGGS vector. The pCAGGS-opti441-HA/DGL was developed through packaging the pCAGGS-opti441-HA with dendrigraft poly-l-lysines (DGLs). DGL not only protected the pCAGGS-opti441-HA from degradation, but also exhibited high transfection efficiency. Strong cellular immune responses were induced in chickens immunized with the pCAGGS-opti441-HA/DGL. The levels of IFN-γ and IL-2, and lymphocyte transformation rate of the vaccinated chickens increased at the third week post the immunization. For the vaccinated chickens, T lymphocytes were activated and proliferated, the numbers of CD3+CD4+ and CD4+/CD8+ increased, and the chickens were protected completely against H9N2 AIV challenge. This study provides a method for the development of novel AIV vaccines, and a theoretical basis for the development of safe and efficient gene delivery carriers.

Updated Studies on the Development of HIV Therapeutic Vaccine

BACKGROUND

Among the various types of pharmaceuticals, vaccines have a special place. However, in the case of HIV, nearly after 40 years of its discovery, an effective vaccine still is not available. The reason lies in several facts mainly the variability and smartness of HIV as well as the complexity of the interaction between HIV and immune responses. A robust, effective, and longterm immunity is undoubtedly what a successful preventive vaccine should induce in order to prevent the infection of HIV. Failure of human trials to this end has led to the idea of developing therapeutic vaccines with the purpose of curing already infected patients by boosting their immune responses against the virus. Nevertheless, the exceptional ability of the virus to escape the immune system based on the genetically diverse envelope and variable protein products have made it difficult to achieve an efficient therapeutic vaccine.

OBJECTIVE

We aimed at studying and comparing different approaches to HIV therapeutic vaccines.

METHODS

In this review, we summarized the human trials undergoing on HIV therapeutic vaccination which are registered in the U.S. clinical trial database (clinicaltrials.gov). These attempts are divided into different tables, according to the type of formulation and application in order to classify and compare their results.

RESULT/CONCLUSION

Among several methods applied in studied clinical trials which are mainly divided into DNA, Protein, Peptide, Viral vectors, and Dendritic cell-based vaccines, protein vaccine strategy is based on Tat protein-induced anti-Tat Abs in 79% HIV patients. However, the studies need to be continued to achieve a durable efficient immune response against HIV-1.

Recent advances on HIV DNA vaccines development: Stepwise improvements to clinical trials

According to WHO (World Health Organization) reports, more than 770,000 people died from HIV and almost 1.7 million people becoming newly infected in the worldwide in 2018. Therefore, many attempts should be done to produce a forceful vaccine to control the AIDS. DNA-based vaccines have been investigated for HIV vaccination by researches during the recent 20 years. The DNA vaccines are novel approach for induction of both type of immune responses (cellular and humoral) in the host cells and have many advantages including high stability, fast and easy of fabrication and absence of severe side effects when compared with other vaccination methods. Recent studies have been focused on vaccine design, immune responses and on the use of adjuvants as a promising strategy for increased level of responses, delivery approaches by viral and non-viral methods and vector design for different antigens of HIV virus. In this review, we outlined the aforementioned advances on HIV DNA vaccines. Then we described the future trends in clinical trials as a strong strategy even in healthy volunteers and the potential developments in control and prevention of HIV.

T cell functionality in HIV-1, HIV-2 and dually infected individuals: correlates of disease progression and immune restoration

The role of suppressive anti-retroviral therapy (ART) in eliciting restoration of dysregulated immune function remains unclear in HIV-1 infection. Also, due to tailoring of therapeutic regimens towards HIV-1, this possible impairment of therapy may be even more pronounced in HIV-2 and dual (HIV-D) infection. Thus, we evaluated the impact of ART on immune restoration by assessing T cell functions, including HIV specific responses in HIV-1-, HIV-2- and HIV-D-infected individuals. Both ART-treated and naive infected subjects showed persistently altered frequency of CD4+ T cell subsets [regulatory T cells (Treg ), naive/central memory, effector memory], increased immune activation, cytoxicity and decreased frequency of natural killer T (NKT)- like cells and T helper type 17 (Th17)/Treg ratio with elevated microbial translocation. Further, HIV-specific responses were dominated by gag-specific CD4+ T cells in virologically suppressed HIV-D individuals, suggesting retention of T cell memory for both viruses. Increased antigen-specific responses, including dual-functional interleukin (IL)-2/interferon (IFN)-γ CD4+ T cells, were detected in therapy receiving HIV-2-infected individuals indicative of a greater and more functionally diverse T cell memory repertoire. We delineated immune signatures specific to therapy-naive single HIV infection, as well as a unique signature associated with HIV-2 disease progression and immune restoration. Circulating Treg frequency, T cell activation and microbial translocation levels correlated with disease progression and immune restoration among all types of HIV infection. Also, memory responses negatively correlated, irrespective of type of infection, in ART receiving infected individuals, with CD4 rebound and decreased pan T cell activation. Our data highlight the need for adjunct immunomodulatory therapeutic strategies to achieve optimal immune restoration in HIV infection.

Toward T Cell-Mediated Control or Elimination of HIV Reservoirs: Lessons From Cancer Immunology

As the AIDS epidemic unfolded, the appearance of opportunistic infections in at-risk persons provided clues to the underlying problem: a dramatic defect in cell-mediated immunity associated with infection and depletion of CD4⁺ T lymphocytes. Moreover, the emergence of HIV-associated malignancies in these same individuals was a clear indication of the significant role effective cellular immunity plays in combating cancers. As research in the HIV field progressed, advances included the first demonstration of the role of PD-1 in human T cell exhaustion, and the development of gene-modified T cell therapies, including chimeric antigen receptor (CAR) T cells. In the intervening years, the oncology field has capitalized on these advances, effectively mobilizing the cellular immune response to achieve immune-mediated remission or cure of previously intractable cancers. Although similar therapeutic advances have not yet been achieved in the HIV field, spontaneous CD8⁺ T cell mediated remission or functional cure of HIV infection does occur in very small subset of individuals in the absence of anti-retroviral therapy (ART). This has many similarities to the CD8⁺ T cell mediated functional control or elimination of cancers, and indicates that immunotherapy for HIV is a rational goal. In HIV infection, one major barrier to successful immunotherapy is the small, persistent population of infected CD4⁺ T cells, the viral reservoir, which evades pharmacological and immune-mediated clearance, and is largely maintained in secondary lymphoid tissues at sites where CD8⁺ T cells have limited access and/or function. The reservoir-enriched lymphoid microenvironment bears a striking resemblance to the tumor microenvironment of many solid tumors–namely high levels of anti-inflammatory cytokines, expression of co-inhibitory receptors, and physical exclusion of immune effector cells. Here, we review the parallels between CD8⁺ T cell-mediated immune control of HIV and cancer, and how advances in cancer immunotherapy may provide insights to direct the development of effective HIV cure strategies. Specifically, understanding the impact of the tissue microenvironment on T cell function and development of CAR T cells and therapeutic vaccines deserve robust attention on the path toward a CD8⁺ T cell mediated cure of HIV infection.

In Silico Design and Immunologic Evaluation of HIV-1 p24-Nef Fusion Protein to Approach a Therapeutic Vaccine Candidate

Background:

Acquired immune deficiency syndrome (HIV/AIDS) has been a major glob-al health concern for over 38 years. No safe and effective preventive or therapeutic vaccine has been developed although many products have been investigated. Computational methods have facilitated vaccine developments in recent decades. Among HIV-1 proteins, p24 and Nef are two suitable targets to provoke the cellular immune response. However, the fusion form of these two proteins has not been analyzed in silico yet.

Objective:

This study aimed at the evaluation of possible fusion forms of p24 and Nef in order to achieve a potential therapeutic subunit vaccine against HIV-1.

Method:

In this study, various computational approaches have been applied to predict the most effec-tive fusion form of p24-Nef including CTL (Cytotoxic T lymphocytes) response, immunogenicity, conservation and population coverage. Moreover, binding to MHC (Major histocompatibility com-plex) molecules was assessed in both human and BALB/c.

Results:

After analyzing six possible fusion protein forms using AAY linker, we came up with the most practical form of p24 from 80 to 231 and Nef from 120 to 150 regions (according to their refer-ence sequence of HXB2 strain) using an AAY linker, based on their peptides affinity to MHC mole-cules which are located in a conserved region among different virus clades. The selected fusion protein contains seventeen MHC I antigenic epitopes, among them KRWIILGLN, YKRWIILGL, DIAG-TTSTL and FPDWQNYTP are fully conserved between the virus clades. Furthermore, analyzed class I CTL epitopes showed greater affinity binding to HLA-B 57*01, HLA-B*51:01 and HLA-B 27*02 molecules. The population coverage with the rate of >70% coverage in the Persian population supports this truncated form as an appropriate candidate against HIV-I virus.

Conclusion:

The predicted fusion protein, p24-AAY-Nef in a truncated form with a high rate of T cell epitopes and high conservancy rate among different clades, provides a helpful model for developing a therapeutic vaccine candidate against HIV-1.

Induction of a Robust Humoral Response using HIV-1 VLPMPER-V3 as a Novel Candidate Vaccine in BALB/c Mice

Background:

Several approaches have not been successful to suppress HIV (Human immunodeficiency virus) infection among infected individuals or to prevent it yet. In order to expand strong HIV specific humoral and cellular responses, Virus-like particles (VLPs) as potential vaccines show significant increase in neutralizing antibodies secretion, T-cell count and also secretion of cytokines.

Objective:

This study aimed at immunological evaluation of VLPs harboring high copy of MPERV3 in BALB/c mice.

Methods:

Female BALB/c mice were immunized with homologous and heterologous primeboosting regimens of HIV-1 VLPMPER-V3. Their immune responses were evaluated for humoral responses (Total IgG and IgG isotyping) and cellular responses (IFN-γ, IL-5 secretion, in vitro CTL assay and T cell proliferation) and compared in immunized mice.

Results:

The data showed robust induction of humoral response in mice groups which received different regimens of VLP. Furthermore, analysis of cytokine profile indicated that the highest IL-5 secretion was related to VLP+M50 group and confirmed the dominance of Th2 immunity in this group.

Conclusion:

This study showed that VLP MPER-V3 as a potential vaccine candidate has the potency as an effective prophylactic vaccine and this finding guarantees further investigations to achieve a promising HIV-1 vaccine candidate.

Toward the Cure of HIV-1 Infection: Lessons Learned and Yet to be Learned as New Strategies are Developed

Here, we review the progress that has been made in achieving a cure of HIV-1 infection. To date, this has only occurred in one person after he received allogeneic stem cell transplants from a CCR5 ∆32 homozygous donor in addition to chemotherapy and radiation to treat his acute myelocytic leukemia. The general consensus is that achieving a sustained remission of infection in the absence of antiretroviral therapy will involve a combination of strategies that involve both the targeting of the latent proviral genome and the induction of more effective anti-HIV-1 immune responses. Efforts to reverse HIV-1 proviral DNA integration in the host cell genome and those to enhance anti-HIV immunity have been disappointing thus far. The lack of clinically validated assays to measure both effects has hampered the development of effective therapies. We suggest the consideration of genome editing as a new approach to reduce the latently integrated proviral genome. In addition, new approaches to therapeutic immunization, alterations of immunoregulatory pathways, anti-HIV-1 antibodies, and anti-HIV-1 chimeric antigen receptor T lymphocytes are in development.

Mucosal T Helper 17 and T Regulatory Cell Homeostasis Correlate with Acute Simian Immunodeficiency Virus Viremia and Responsiveness to Antiretroviral Therapy in Macaques

Depletion of gut T helper 17 (Th17) cells during HIV infection leads to decreased mucosal integrity and increased disease progression. Conversely, T regulatory (Treg) cells may inhibit antiviral responses or immune activation. In HIV elite controllers, a balanced Th17/Treg ratio is maintained in the blood, suggesting a role for these responses in controlling inflammation and viral replication. HIV-infected individuals exhibit a range in responsiveness to combination antiretroviral therapy (cART). Given the link between the Th17/Treg ratio and HIV disease, we reasoned these responses may play a role in cART responsiveness. In this study, we investigated the relationship between the mucosal Th17/Treg ratio to acute simian immunodeficiency virus (SIV) viremia and the response to cART. Nineteen rhesus macaques were infected with highly pathogenic SIVΔB670 virus and cART was initiated 6 weeks postinfection. Mucosal CD4 T cell subsets were assessed by intracellular cytokine staining in the colon and mesenteric lymph nodes. Higher baseline Th17/Treg ratios corresponded with increased acute SIV viremia. Th17/Treg ratios decreased during acute SIV infection and were not restored during cART, and this corresponded to increased gut immune activation (Ki67⁺), markers of microbial translocation (sCD14), and T cell exhaustion (TIGIT⁺). Animals that maintained a more balanced mucosal Th17/Treg ratio at the time of cART initiation exhibited a better virological response to cART and maintained higher peripheral CD4 counts. These results suggest mucosal Th17 and Treg homeostasis influences acute viremia and the response to cART, a result that suggests therapeutic interventions that improve the Th17/Treg ratio before or during cART may improve treatment of HIV.

Accelerating HIV vaccine development using non-human primate models

INTRODUCTION

The search for a preventative HIV vaccine is ongoing after three decades of research. Contributions of non-human primate (NHP) models to this research are irrefutable, however interpreting data obtained for translation to humans has been problematic. As knowledge concerning NHP models has accumulated, their utility and value in assessing immunogenicity and efficacy of novel vaccines have become apparent. NHP models have become a critical component of vaccine design.

AREAS COVERED

Beginning with early vaccine studies, we trace the development and evolution of NHP models concurrent with changes in HIV vaccine concepts and in response to their ability to predict clinical trial efficacy. The value of NHP studies in guiding vaccine design is highlighted along with their importance in opening new areas of investigation and facilitating movement of promising approaches into the clinic.

EXPERT COMMENTARY

Due to their close relatedness to humans, NHPs are an excellent choice for immunogenicity studies. The ability of NHP models to predict clinical efficacy has improved with the introduction of low-dose challenge viruses and recognition of confounding variables in study outcomes. Use of NHP models has opened new research areas with outstanding potential for generating vaccine efficacy against HIV and other infectious agents.

Computational Design of Epitope-Enriched HIV-1 Gag Antigens with Preserved Structure and Function for Induction of Broad CD8+ T Cell Responses

The partially protective phenotype observed in HIV-infected long-term-non-progressors is often associated with certain HLA alleles, thus indicating that cytotoxic T lymphocyte (CTL) responses play a crucial role in combating virus replication. However, both the vast variability of HIV and the HLA diversity impose a challenge on elicitation of broad and effective CTL responses. Therefore, we conceived an algorithm for the enrichment of CD8⁺ T cell epitopes in HIV’s Gag protein, respecting functional preservation to enable cross-presentation. Experimentally identified epitopes were compared to a Gag reference sequence. Amino-acid-substitutions (AAS) were assessed for their impact on Gag’s budding-function using a trained classifier that considers structural models and sequence conservation. Experimental assessment of Gag-variants harboring selected AAS demonstrated an apparent classifier-precision of 100%. Compatible epitopes were assigned an immunological score that incorporates features such as conservation or HLA-association in a user-defined weighted manner. Using a genetic algorithm, the epitopes were incorporated in an iterative manner into novel T-cell-epitope-enriched Gag sequences (TeeGag). Computational evaluation showed that these antigen candidates harbor a higher fraction of epitopes with higher score as compared to natural Gag isolates and other artificial antigen designs. Thus, these designer sequences qualify as next-generation antigen candidates for induction of broader CTL responses.