Recombinant influenza virus expressing HIV-1 p24 capsid protein induces mucosal HIV-specific CD8 T-cell responses

An intranasal influenza virus vector vaccine protects against Helicobacter pylori in mice

Helicobacter pylori is a human pathogen that infects almost half of the population. Antibiotic resistance in H. pylori threatens health and increases the demand for prophylactic and therapeutic vaccines. Traditional oral vaccine research faces considerable challenges because of the epithelial barrier, potential enterotoxicity of adjuvants, and the challenging conditions of the gastric environment. We developed an intranasal influenza A virus (IAV) vector vaccine based on two live attenuated influenza viruses with modified acidic polymerase protein (PA) genes encoding the A subunit of H. pylori neutrophil-activating protein (NapA), named IAV-NapA, including influenza virus A/WSN/33 (WSN)-NapA and A/Puerto Rico/8/34 (PR8)-NapA. These recombinant influenza viruses were highly attenuated and exhibited strong immunogenicity in mice. Vaccination with IAV-NapA induced antigen-specific humoral and mucosal immune responses while stimulating robust Th1 and Th17 cell immune responses in mice. Our findings suggest that prophylactic and therapeutic vaccination with influenza virus vector vaccines significantly reduces colonization of H. pylori and inflammation in the stomach of mice.IMPORTANCEHelicobacter pylori is the most common cause of chronic gastritis and leads to severe gastroduodenal pathology in some patients. Many studies have shown that Th1 and Th17 cellular and gastric mucosal immune responses are critical in reducing H. pylori load. IAV vector vaccines can stimulate these immune responses while overcoming potential adjuvant toxicity and antigen dosing issues. To date, no studies have demonstrated the role of live attenuated IAV vector vaccines in preventing and treating H. pylori infection. Our work indicates that vaccination with IAV-NapA induces antigen-specific humoral, cellular, and mucosal immunity, producing a protective and therapeutic effect against H. pylori infection in BALB/c mice. This undescribed H. pylori vaccination approach may provide valuable information for developing vaccines against H. pylori infection.

Clade 2.3.4.4 H5 chimeric cold-adapted attenuated influenza vaccines induced cross-reactive protection in mice and ferrets

IMPORTANCE

Clade 2.3.4.4 H5Nx avian influenza viruses (AIVs) have circulated globally and caused substantial economic loss. Increasing numbers of humans have been infected with Clade 2.3.4.4 H5N6 AIVs in recent years. Only a few human influenza vaccines have been licensed to date. However, the licensed live attenuated influenza virus vaccine exhibited the potential of being recombinant with the wild-type influenza A virus (IAV). Therefore, we developed a chimeric cold-adapted attenuated influenza vaccine based on the Clade 2.3.4.4 H5 AIVs. These H5 vaccines demonstrate the advantage of being non-recombinant with circulated IAVs in the future influenza vaccine study. The findings of our current study reveal that these H5 vaccines can induce cross-reactive protective efficacy in mice and ferrets. Our H5 vaccines may provide a novel option for developing human-infected Clade 2.3.4.4 H5 AIV vaccines.

Bacterial Spore-Based Delivery System: 20 Years of a Versatile Approach for Innovative Vaccines

Mucosal vaccines offer several advantages over injectable conventional vaccines, such as the induction of adaptive immunity, with secretory IgA production at the entry site of most pathogens, and needle-less vaccinations. Despite their potential, only a few mucosal vaccines are currently used. Developing new effective mucosal vaccines strongly relies on identifying innovative antigens, efficient adjuvants, and delivery systems. Several approaches based on phages, bacteria, or nanoparticles have been proposed to deliver antigens to mucosal surfaces. Bacterial spores have also been considered antigen vehicles, and various antigens have been successfully exposed on their surface. Due to their peculiar structure, spores conjugate the advantages of live microorganisms with synthetic nanoparticles. When mucosally administered, spores expressing antigens have been shown to induce antigen-specific, protective immune responses. This review accounts for recent progress in the formulation of spore-based mucosal vaccines, describing a spore's structure, specifically the spore surface, and the diverse approaches developed to improve its efficiency as a vehicle for heterologous antigen presentation.

Dysregulated Microglial Cell Activation and Proliferation Following Repeated Antigen Stimulation

Upon reactivation of quiescent neurotropic viruses antigen (Ag)-specific brain resident-memory CD8+ T-cells (bT_RM) may respond to de novo-produced viral Ag through the rapid release of IFN-γ, which drives subsequent interferon-stimulated gene expression in surrounding microglia. Through this mechanism, a small number of adaptive bT_RM may amplify responses to viral reactivation leading to an organ-wide innate protective state. Over time, this brain-wide innate immune activation likely has cumulative neurotoxic and neurocognitive consequences. We have previously shown that HIV-1 p24 Ag-specific bT_RM persist within the murine brain using a heterologous prime-CNS boost strategy. In response to Ag restimulation, these bT_RM display rapid and robust recall responses, which subsequently activate glial cells. In this study, we hypothesized that repeated challenges to viral antigen (Ag) (modeling repeated episodes of viral reactivation) culminate in prolonged reactive gliosis and exacerbated neurotoxicity. To address this question, mice were first immunized with adenovirus vectors expressing the HIV p24 capsid protein, followed by a CNS-boost using Pr55Gag/Env virus-like particles (HIV-VLPs). Following the establishment of the bT_RM population [>30 days (d)], prime-CNS boost animals were then subjected to in vivo challenge, as well as re-challenge (at 14 d post-challenge), using the immunodominant HIV-1 AI9 CD8+ T-cell epitope peptide. In these studies, Ag re-challenge resulted in prolonged expression of microglial activation markers and an increased proliferative response, longer than the challenge group. This continued expression of MHCII and PD-L1 (activation markers), as well as Ki67 (proliferative marker), was observed at 7, 14, and 30 days post-AI9 re-challenge. Additionally, in vivo re-challenge resulted in continued production of inducible nitric oxide synthase (iNOS) with elevated levels observed at 7, 14 and 30 days post re-challenge. Interestingly, iNOS expression was significantly lower among challenged animals when compared to re-challenged groups. Furthermore, in vivo specific Ag re-challenge produced lower levels of arginase (Arg)-1 when compared with the challenged group. Taken together, these results indicate that repeated Ag-specific stimulation of adaptive immune responses leads to cumulative dysregulated microglial cell activation.

Programmed death ligand-1 induction restrains the cytotoxic T lymphocyte response against microglia

Microglial cells are the main reservoir for HIV-1 within the brain and potential exists for negative immune checkpoint blockade therapies to purge this viral reservoir. Here, we investigated cytolytic responses of CD8⁺ T lymphocytes against microglia loaded with peptide epitopes. Initially, flow cytometric analysis demonstrated efficient killing of HIV-1 p24 AI9 or YI9 peptide-loaded splenocytes in MHC-matched recipients. Cytolytic killing of microglia was first demonstrated using ovalbumin (OVA) as a model antigen for in vitro cytotoxic T lymphocyte (CTL) assays. Peptide-loaded primary microglia obtained from programmed death ligand (PD-L) 1 knockout (KO) animals showed significantly more killing than cells from wild-type (WT) animals when co-cultured with activated CD8⁺ T-cells isolated from rAd5-OVA primed animals. Moreover, when peptide loaded-microglial cells from WT animals were treated with neutralizing α-PD-L1 Ab, significantly more killing was observed compared to either untreated or IgG isotype-treated cells. Most importantly, significantly increased in vivo killing of HIV-1 p24 YI9 peptide-loaded microglia from PD-L1 KO animals, as well as AI9 peptide-loaded BALB/c microglial cells treated with α-PD-L1, was observed within brains of rAd5-p24 primed-CNS boosted C57BL/6 or BALB/c mice, respectively. Finally, ex vivo responses of brain CD8⁺ T-cells in response to AI9 stimulation showed significantly increased IFN-γ and IL-2 production when treated with α-PD-1 Abs. Greater proliferation of CD8+ T-cells from the brain was also observed following blockade. Taken together, these studies demonstrate that PD-L1 induction on microglia restrains CTL responses and indicate that immune checkpoint blockade targeting this pathway may be beneficial in clearing viral brain reservoirs.

Recall Responses from Brain-Resident Memory CD8+ T Cells (bTRM) Induce Reactive Gliosis

HIV-associated neurocognitive disorders (HAND) persist even during effective combination antiretroviral therapy (cART). Although the cause of HAND is unknown, studies link chronic immune activation, neuroinflammation, and cerebrospinal fluid viral escape to disease progression. In this study, we tested the hypothesis that specific, recall immune responses from brain-resident memory T cells (bT_RM) could activate glia and induce neurotoxic mediators. To address this question, we developed a heterologous prime-central nervous system (CNS) boost strategy in mice. We observed that the murine brain became populated with long-lived CD8⁺ bT_RM, some being specific for an immunodominant Gag epitope. Recall stimulation using HIV-1 AI9 peptide administered in vivo resulted in microglia displaying elevated levels of major histocompatibility complex class II and programmed death-ligand 1, and demonstrating tissue-wide reactive gliosis. Immunostaining further confirmed this glial activation. Taken together, these results indicate that specific, adaptive recall responses from bT_RM can induce reactive gliosis and production of neurotoxic mediators.

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Heterologous prime-CNS boost induced HIV-1-specific bT_RM, which persisted long term

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Recall responses from HIV-specific bT_RM induced tissue-wide reactive gliosis

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bT_RM induced-reactive gliosis likely has cumulative neurotoxic consequences

Recombinant influenza A viruses as vaccine vectors

INTRODUCTION

Various viruses, including poxviruses, adenoviruses and vesicular stomatitis virus, have been considered as vaccine vectors for the delivery of antigens of interest in the development of vaccines against newly emerging pathogens.

AREAS COVERED

Here, we review results that have been obtained with influenza A viruses (IAV) as vaccine vectors. With the advent of reverse genetics technology, IAV-based recombinant vaccine candidates have been constructed that induce protective immunity to a variety of different pathogens of interest, including West Nile virus, Plasmodium falciparum and respiratory syncytial virus. The various cloning strategies to produce effective and attenuated, safe to use IAV-based viral vectors are discussed.

EXPERT COMMENTARY

It was concluded that IAV-based vector system has several advantages and holds promise for further development.

Viral vector and route of administration determine the ILC and DC profiles responsible for downstream vaccine-specific immune outcomes

This study demonstrates that route and viral vector can significantly influence the innate lymphoid cells (ILC) and dendritic cells (DC) recruited to the vaccination site, 24 h post delivery. Intranasal (i.n.) vaccination induced ST2/IL-33R⁺ ILC2, whilst intramuscular (i.m.) induced IL-25R⁺ and TSLPR⁺ (Thymic stromal lymphopoietin protein receptor) ILC2 subsets. However, in muscle a novel ILC subset devoid of the known ILC2 markers (IL-25R^- IL-33R^- TSLPR^-) were found to express IL-13, unlike in lung. Different viral vectors also influenced the ILC-derived cytokines and the DC profiles at the respective vaccination sites. Both i.n. and i.m. recombinant fowlpox virus (rFPV) priming, which has been associated with induction of high avidity T cells and effective antibody differentiation exhibited low ILC2-derived IL-13, high NKp46⁺ ILC1/ILC3 derived IFN-γ and low IL-17A, together with enhanced CD11b⁺ CD103^- conventional DCs (cDC). In contrast, recombinant Modified Vaccinia Ankara (rMVA) and Influenza A vector priming, which has been linked to low avidity T cells, induced opposing ILC derived-cytokine profiles and enhanced cross-presenting DCs. These observations suggested that the former ILC/DC profiles could be a predictor of a balanced cellular and humoral immune outcome. In addition, following i.n. delivery Rhinovirus (RV) and Adenovius type 5 (Ad5) vectors that induced elevated ILC2-derived IL-13, NKp46⁺ ILC1/ILC3-derived-IFN-γ and no IL-17A, predominantly recruited CD11b^- B220⁺ plasmacytoid DCs (pDC). Knowing that pDC are involved in antibody differentiation, we postulate that i.n. priming with these vectors may favour induction of effective humoral immunity. Our data also revealed that vector-specific replication status and/or presence or absence of immune evasive genes can significantly alter the ILC and DC activity. Collectively, our findings suggest that understanding the route- and vector-specific ILC and DC profiles at the vaccination site may help tailor/design more efficacious viral vector-based vaccines, according to the pathogen of interest.

Induction of vaginal-resident HIV-specific CD8 T cells with mucosal prime-boost immunization

Tissue-resident memory (T_RM) CD8 T cells survey a range of non-lymphoid mucosal tissues where they rapidly mediate clearance of viral infections at the entry portals. Vaccines that establish CD8 T_RM cells in the cervicovaginal mucosa hold promise for effective immunity against sexually transmitted HIV. We demonstrate that HIV-specific CD8 T_RM cells can be established in the murine vaginal mucosa using a combined intranasal and intravaginal mucosal immunization with recombinant influenza-HIV vectors. Using in situ tetramer immunofluorescence microscopy, we found that this mucosally administered prime-boost immunization also resulted in the durable seeding of CD8 T cells in the frontline vaginal epithelial compartment as opposed to the vaginal submucosa. Upon cognate antigen recognition within the vaginal mucosa, these HIV-specific CD8 T_RM cells rapidly initiated a tissue-wide state of immunity. The activation of HIV-specific CD8 T_RM cells resulted in the upregulation of endothelial vessel addressin expression and substantial recruitment of both adaptive and innate immune cells in the vaginal mucosa. These findings suggest that the epithelial localization of HIV-specific CD8 T_RM cell populations and their capacity to rapidly activate both arms of the immune system could significantly augment frontline defenses against vaginal HIV infection.

The cell surface mucin MUC1 limits the severity of influenza A virus infection

Cell surface mucin (cs-mucin) glycoproteins are constitutively expressed at the surface of respiratory epithelia where pathogens such as influenza A virus (IAV) gain entry into cells. Different members of the cs-mucin family each express a large and heavily glycosylated extracellular domain that towers above other receptors on the epithelial cell surface, a transmembrane domain that enables shedding of the extracellular domain, and a cytoplasmic tail capable of triggering signaling cascades. We hypothesized that IAV can interact with the terminal sialic acids presented on the extracellular domain of cs-mucins, resulting in modulation of infection efficiency. Utilizing human lung epithelial cells, we found that IAV associates with the cs-mucin MUC1 but not MUC13 or MUC16. Overexpression of MUC1 by epithelial cells or the addition of sialylated synthetic MUC1 constructs, reduced IAV infection in vitro. In addition, Muc1^-/- mice infected with IAV exhibited enhanced morbidity and mortality, as well as greater inflammatory mediator responses compared to wild type mice. This study implicates the cs-mucin MUC1 as a critical and dynamic component of the innate host response that limits the severity of influenza and provides the foundation for exploration of MUC1 in resolving inflammatory disease.

Structures and Corresponding Functions of Five Types of Picornaviral 2A Proteins

Among the few non-structural proteins encoded by the picornaviral genome, the 2A protein is particularly special, irrespective of structure or function. During the evolution of the Picornaviridae family, the 2A protein has been highly non-conserved. We believe that the 2A protein in this family can be classified into at least five distinct types according to previous studies. These five types are (A) chymotrypsin-like 2A, (B) Parechovirus-like 2A, (C) hepatitis-A-virus-like 2A, (D) Aphthovirus-like 2A, and (E) 2A sequence of the genus Cardiovirus. We carried out a phylogenetic analysis and found that there was almost no homology between each type. Subsequently, we aligned the sequences within each type and found that the functional motifs in each type are highly conserved. These different motifs perform different functions. Therefore, in this review, we introduce the structures and functions of these five types of 2As separately. Based on the structures and functions, we provide suggestions to combat picornaviruses. The complexity and diversity of the 2A protein has caused great difficulties in functional and antiviral research. In this review, researchers can find useful information on the 2A protein and thus conduct improved antiviral research.

Engaging Natural Killer T Cells as 'Universal Helpers' for Vaccination

Conventional vaccine adjuvants enhance peptide-specific T-cell and B-cell responses by modifying peptide stability or uptake or by binding to pattern-recognition receptors on antigen-presenting cells (APCs). This article discusses the application of a distinct mechanism of adjuvant activity: the activation of type I, or invariant, natural killer T (iNKT) cells to drive cellular and humoral immune responses. Using a semi-invariant T-cell receptor (TCR), iNKT cells recognize glycolipid antigens presented on cluster of differentiation (CD)-1d molecules. When their ligands are presented in concert with peptides, iNKT cells can provide T-cell help, 'licensing' APCs to augment peptide-specific T-cell and antibody responses. We discuss the potential benefits and limitations of exploiting iNKT cells as 'universal helpers' to enhance vaccine responses for the treatment and prevention of cancer and infectious diseases.

Modulation of innate and adaptive cellular immunity relevant to HIV-1 vaccine design by seminal plasma

OBJECTIVES

Mucosal exposure to HIV-1 infection generally occurs in the presence of semen. Immunomodulation by seminal plasma is well described in the reproductive biology literature. Little is known, however, about the impact of seminal plasma on innate and adaptive anti-HIV-1 cellular immunity.

DESIGN

The study investigated the effects of seminal plasma on immune responses considered important for prophylactic HIV-1 vaccine development, namely innate and adaptive cellular immunity mediated by natural killer (NK) cells and T cells, respectively.

METHODS

The ability of seminal plasma to modulate direct, antibody-dependent and cytokine-stimulated NK cell activation was assessed utilizing intracellular cytokine staining. Direct and antibody-dependent cellular cytotoxicity was assessed using lactate dehydrogenase release assays. The effects of seminal plasma on T-cell activation upon stimulation with staphylococcus enterotoxin B or HIV-1 Gag peptides were assessed by intracellular cytokine staining. The impact of seminal plasma on redirected cytolysis mediated by T cells was measured using lactate dehydrogenase release assays.

RESULTS

Both direct and antibody-dependent NK cell activation were dramatically impaired by the presence of either HIV-1-uninfected or HIV-1-infected seminal plasma in a dose-dependent manner. Additionally, seminal plasma suppressed both direct and antibody-dependent NK cell-mediated cytolysis, including anti-HIV-1 antibody-dependent cytolysis of gp120-pulsed CEM.NKr-CCR5 cells. Finally, seminal plasma attenuated both HIV-1 Gag-specific and staphylococcus enterotoxin B-induced CTL activation.

CONCLUSIONS

Semen contains potent immunosuppressors of both NK cell and CD8 T-cell-mediated anti-HIV-1 immune responses. This could impede attempts to provide vaccine-induced immunity to HIV-1.