Cross-protection against influenza virus infection by intranasal administration of nucleoprotein-based vaccine with compound 48/80 adjuvant

Expression and purification of an NP-hoc fusion protein: Utilizing influenza a nucleoprotein and phage T4 hoc protein

Influenza poses a substantial health risk, with infants and the elderly being particularly susceptible to its grave impacts. The primary challenge lies in its rapid genetic evolution, leading to the emergence of new Influenza A strains annually. These changes involve punctual mutations predominantly affecting the two main glycoproteins: Hemagglutinin (HA) and Neuraminidase (NA). Our existing vaccines target these proteins, providing short-term protection, but fall short when unexpected pandemics strike. Delving deeper into Influenza's genetic makeup, we spotlight the nucleoprotein (NP) - a key player in the transcription, replication, and packaging of RNA. An intriguing characteristic of the NP is that it is highly conserved across all Influenza A variants, potentially paving the way for a more versatile and broadly protective vaccine. We designed and synthesized a novel NP-Hoc fusion protein combining Influenza A nucleoprotein and T4 phage Hoc, cloned using Gibson assembly in E. coli, and purified via ion affinity chromatography. Simultaneously, we explore the T4 coat protein Hoc, typically regarded as inconsequential in controlled viral replication. Yet, it possesses a unique ability: it can link with another protein, showcasing it on the T4 phage coat. Fusing these concepts, our study designs, expresses, and purifies a novel fusion protein named NP-Hoc. We propose this protein as the basis for a new generation of vaccines, engineered to guard broadly against Influenza A. The excitement lies not just in the immediate application, but the promise this holds for future pandemic resilience, with NP-Hoc marking a significant leap in adaptive, broad-spectrum influenza prevention.

A Live Attenuated H1N1 Influenza Vaccine Based on the Mutated M Gene

The influenza vaccines currently approved for clinical use mainly include inactivated influenza virus vaccines and live attenuated influenza vaccines (LAIVs). LAIVs have multiple advantages, such as ease of use and strong immunogenicity, and can provide cross-protection. In this study, the M gene of the PR8 virus was mutated as follows (G11T, C79G, G82C, C85G, and C1016A), and a live attenuated influenza virus containing the mutated M gene was rescued and obtained using reverse genetic technology as a vaccine candidate. The replication ability of the rescued virus was significantly weakened in both MDCK cells and mice with attenuated virulence. Studies on immunogenicity found that 1000 TCID50 of mutated PR8 (mPR8) can prime strong humoral and cellular immune responses. Single-dose immunization of 1000 TCID50 mPR8 was not only able to counter the challenge of the homologous PR8 virus but also provided cross-protection against the heterologous H9N2 virus.

Outlining recent updates on influenza therapeutics and vaccines: A comprehensive review

Influenza virus has presented a considerable healthcare challenge during the past years, particularly in vulnerable groups with compromised immune systems. Therapeutics and vaccination have always been in research annals since the spread of influenza. Efforts have been going on to develop an antiviral therapeutic approach that could assist in better disease management and reduce the overall disease complexity, resistance development, and fatality rates. On the other hand, vaccination presents a chance for effective, long-term, cost-benefit, and preventive response against the morbidity and mortality associated with the influenza. However, the issues of resistance development, strain mutation, antigenic variability, and inability to cure wide-spectrum and large-scale strains of the virus by available vaccines remain there. The article gathers the updated data for the therapeutics and available influenza vaccines, their mechanism of action, shortcomings, and trials under clinical experimentation. A methodological approach has been adopted to identify the prospective therapeutics and available vaccines approved and within the clinical trials against the influenza virus. Review contains influenza therapeutics, including traditional and novel antiviral drugs and inhibitor therapies against influenza virus as well as research trials based on newer drug combinations and latest technologies such as nanotechnology and organic and plant-based natural products. Most recent development of influenza vaccine has been discussed including some updates on traditional vaccination protocols and discussion on next-generation and upgraded novel technologies. This review will help the readers to understand the righteous approach for dealing with influenza virus infection and for deducing futuristic approaches for novel therapeutic and vaccine trials against Influenza.

Immunogenicity, safety, and preliminary efficacy evaluation of OVX836, a nucleoprotein-based universal influenza A vaccine candidate: a randomised, double-blind, placebo-controlled, phase 2a trial

BACKGROUND

OVX836, a recombinant vaccine containing the nucleoprotein of the influenza A virus A/WSN/1933 (H1N1) and the oligomerisation domain OVX313, has displayed a good safety profile and elicited dose-dependent humoral and cellular immune responses at 90 μg or 180 μg (intramuscularly) in previous clinical trials. The aim of this study was to explore higher doses, since no maximum tolerated dose had been reached.

METHODS

In this phase 2a, randomised, double-blind, placebo-controlled study, we recruited 137 healthy adults aged 18-55 years in a single centre in Belgium. Participants were randomly assigned (interactive web response system; block size=4) using SAS (version 9.4) to receive one single intramuscular administration of OVX836 influenza vaccine at three doses (180 μg [n=33], 300 μg [n=35], and 480 μg [n=36]) or placebo (n=33). The two primary endpoints were the safety and the cell-mediated immune response to OVX836 at the three doses in terms of change of nucleoprotein-specific IFNγ spot forming cell (SFC) frequencies in the peripheral blood mononuclear cell (PBMC) population, measured by IFNγ ELISpot, at day 8 versus pre-injection baseline (day 1). The population used for the safety analysis is the modified intention-to-treat cohort. The population used for the immunogenicity analysis is the per-protocol cohort. This trial is registered with ClinicalTrials.gov, NCT05060887, and EudraCT, 2021-002535-39.

FINDINGS

Participants were recruited between Nov 15, 2021, and Feb 1, 2022. OVX836 had a favourable safety profile up to 480 μg without reaching the maximum tolerated dose, and showed a good safety profile at all doses with mild local and systemic reactogenicity. 7 days after vaccination, although no significant differences were observed between the doses, OVX836 increased the frequency of nucleoprotein-specific IFNγ SFCs per million PBMCs from days 1 to 8 (primary endpoint): by 124 SFCs per 106 PMBCs (95% CI 67 to 180; p=0·002) at 180 μg; by 202 SFCs per 106 PMBCs (95% CI 138 to 267; p<0·0001) at 300 μg; by 223 SFCs per 106 PMBCs (95% CI 147 to 299; p<0·0001) at 480 μg; and decreased by 1 SFCs per 106 PMBCs (95% CI -24 to 22] in the placebo group (Kruskal-Wallis test p<0·0001 followed by Mann-Whitney's tests; per-protocol cohort). Dose-dependent and polyfunctional nucleoprotein-specific CD4 T-cell responses were observed, and CD8 T-cell responses were elicited at 300 μg and 480 μg (secondary endpoints).

INTERPRETATION

OVX836 appears to be a safe and well tolerated candidate vaccine that elicits humoral and cellular nucleoprotein-specific immune responses (including CD8 T cells at the highest dose levels) and showed a preliminary signal of protection against influenza. Therefore, OVX836 is a promising vaccine candidate for universal influenza A prevention, that warrants further trials.

FUNDING

OSIVAX, Bpifrance, Wallonia Region, and the EUs Horizon 2020 Research and Innovation Program.

Nucleoprotein as a Promising Antigen for Broadly Protective Influenza Vaccines

Annual vaccination is considered as the main preventive strategy against seasonal influenza. Due to the highly variable nature of major viral antigens, such as hemagglutinin (HA) and neuraminidase (NA), influenza vaccine strains should be regularly updated to antigenically match the circulating viruses. The influenza virus nucleoprotein (NP) is much more conserved than HA and NA, and thus seems to be a promising target for the design of improved influenza vaccines with broad cross-reactivity against antigenically diverse influenza viruses. Traditional subunit or recombinant protein influenza vaccines do not contain the NP antigen, whereas live-attenuated influenza vaccines (LAIVs) express the viral NP within infected cells, thus inducing strong NP-specific antibodies and T-cell responses. Many strategies have been explored to design broadly protective NP-based vaccines, mostly targeted at the T-cell mode of immunity. Although the NP is highly conserved, it still undergoes slow evolutionary changes due to selective immune pressure, meaning that the particular NP antigen selected for vaccine design may have a significant impact on the overall immunogenicity and efficacy of the vaccine candidate. In this review, we summarize existing data on the conservation of the influenza A viral nucleoprotein and review the results of preclinical and clinical trials of NP-targeting influenza vaccine prototypes, focusing on the ability of NP-specific immune responses to protect against diverse influenza viruses.

Protective Efficacy of a Mucosal Influenza Vaccine Formulation Based on the Recombinant Nucleoprotein Co-Administered with a TLR2/6 Agonist BPPcysMPEG

Current influenza vaccines target highly variable surface glycoproteins; thus, mismatches between vaccine strains and circulating strains often diminish vaccine protection. For this reason, there is still a critical need to develop effective influenza vaccines able to protect also against the drift and shift of different variants of influenza viruses. It has been demonstrated that influenza nucleoprotein (NP) is a strong candidate for a universal vaccine, which contributes to providing cross-protection in animal models. In this study, we developed an adjuvanted mucosal vaccine using the recombinant NP (rNP) and the TLR2/6 agonist S-[2,3-bispalmitoyiloxy-(2R)-propyl]-R-cysteinyl-amido-monomethoxyl-poly-ethylene-glycol (BPPcysMPEG). The vaccine efficacy was compared with that observed following parenteral vaccination of mice with the same formulation. Mice vaccinated with 2 doses of rNP alone or co-administered with BPPcysMPEG by the intranasal (i.n.) route showed enhanced antigen-specific humoral and cellular responses. Moreover, NP-specific humoral immune responses, characterized by significant NP-specific IgG and IgG subclass titers in sera and NP-specific IgA titers in mucosal territories, were remarkably increased in mice vaccinated with the adjuvanted formulation as compared with those of the non-adjuvanted vaccination group. The addition of BPPcysMPEG also improved NP-specific cellular responses in vaccinated mice, characterized by robust lymphoproliferation and mixed Th1/Th2/Th17 immune profiles. Finally, it is notable that the immune responses elicited by the novel formulation administered by the i.n. route were able to confer protection against the influenza H1N1 A/Puerto Rico/8/1934 virus.

Respiratory Syncytial Virus Infection: Treatments and Clinical Management

Respiratory syncytial virus (RSV) is a major healthcare concern, especially for immune-compromised individuals and infants below 5 years of age. Worldwide, it is known to be associated with incidences of morbidity and mortality in infants. Despite the seriousness of the issue and continuous rigorous scientific efforts, no approved vaccine or available drug is fully effective against RSV. The purpose of this review article is to provide insights into the past and ongoing efforts for securing effective vaccines and therapeutics against RSV. The readers will be able to confer the mechanism of existing therapies and the loopholes that need to be overcome for future therapeutic development against RSV. A methodological approach was applied to collect the latest data and updated results regarding therapeutics and vaccine development against RSV. We outline the latest throughput vaccination technologies and prophylactic development efforts linked with RSV. A range of vaccination approaches with the already available vaccine (with limited use) and those undergoing trials are included. Moreover, important drug regimens used alone or in conjugation with adjuvants or vaccines are also briefly discussed. After reading this article, the audience will be able to understand the current standing of clinical management in the form of the vaccine, prophylactic, and therapeutic candidates against RSV. An understanding of the biological behavior acting as a reason behind the lack of effective therapeutics against RSV will also be developed. The literature indicates a need to overcome the limitations attached to RSV clinical management, drugs, and vaccine development that could be explained by dealing with the challenges of current study designs with continuous improvement and further work and approval on novel therapeutic applications.

Recent Progress in Recombinant Influenza Vaccine Development Toward Heterosubtypic Immune Response

Flu, a viral infection caused by the influenza virus, is still a global public health concern with potential to cause seasonal epidemics and pandemics. Vaccination is considered the most effective protective strategy against the infection. However, given the high plasticity of the virus and the suboptimal immunogenicity of existing influenza vaccines, scientists are moving toward the development of universal vaccines. An important property of universal vaccines is their ability to induce heterosubtypic immunity, i.e., a wide immune response coverage toward different influenza subtypes. With the increasing number of studies and mounting evidence on the safety and efficacy of recombinant influenza vaccines (RIVs), they have been proposed as promising platforms for the development of universal vaccines. This review highlights the current progress and advances in the development of RIVs in the context of heterosubtypic immunity induction toward universal vaccine production. In particular, this review discussed existing knowledge on influenza and vaccine development, current hemagglutinin-based RIVs in the market and in the pipeline, other potential vaccine targets for RIVs (neuraminidase, matrix 1 and 2, nucleoprotein, polymerase acidic, and basic 1 and 2 antigens), and deantigenization process. This review also provided discussion points and future perspectives in looking at RIVs as potential universal vaccine candidates for influenza.

Randomized, Double-Blind, Reference-Controlled, Phase 2a Study Evaluating the Immunogenicity and Safety of OVX836, A Nucleoprotein-Based Influenza Vaccine

OVX836 is a recombinant protein-based vaccine targeting the highly conserved influenza nucleoprotein (NP), which aims to confer a broad-spectrum protection against influenza. In a Phase 1 study, OVX836, administered intramuscularly, has been found safe and immunogenic. The 90µg and 180µg dose levels were selected to be further evaluated in this randomized, monocenter, reference-controlled (Influvac Tetra™: quadrivalent seasonal influenza subunit vaccine), parallel group, double-blind, Phase 2a study in 300 healthy volunteers, aged 18-65 years, during the 2019/2020 flu season. Safety, influenza-like illness episodes (ILI; based on the Flu-PRO^® questionnaire) and immunogenicity were assessed up to 180 days post-vaccination. OVX836 was safe and presented a reactogenicity profile similar to Influvac Tetra. It induced a significant increase in terms of NP-specific interferon-gamma (IFNγ) spot forming cells (SFCs), NP-specific CD4+ T-cells (essentially polyfunctional cells) and anti-NP IgG responses. OVX836 was superior to Influvac Tetra for all immunological parameters related to NP, and the 180µg dose was significantly superior to the 90µg dose for SFCs and CD4+ T-cells expressing IFNγ. Both the CD4+ T-cell and the anti-NP IgG responses persisted up to Day 180. An efficacy signal was observed with OVX836 at 180µg through reduction of ILI episodes occurring during the flu season as of 14 days post-vaccination. In conclusion, these results encourage further clinical evaluation of OVX836 in order to confirm the signal of efficacy on ILIs and/or laboratory-confirmed influenza cases. NCT04192500 (https://clinicaltrials.gov/ct2/show/study/NCT04192500).

Nasal Immunization With Small Molecule Mast Cell Activators Enhance Immunity to Co-Administered Subunit Immunogens

Mast cell activators are a novel class of mucosal vaccine adjuvants. The polymeric compound, Compound 48/80 (C48/80), and cationic peptide, Mastoparan 7 (M7) are mast cell activators that provide adjuvant activity when administered by the nasal route. However, small molecule mast cell activators may be a more cost-efficient adjuvant alternative that is easily synthesized with high purity compared to M7 or C48/80. To identify novel mast cell activating compounds that could be evaluated for mucosal vaccine adjuvant activity, we employed high-throughput screening to assess over 55,000 small molecules for mast cell degranulation activity. Fifteen mast cell activating compounds were down-selected to five compounds based on in vitro immune activation activities including cytokine production and cellular cytotoxicity, synthesis feasibility, and selection for functional diversity. These small molecule mast cell activators were evaluated for in vivo adjuvant activity and induction of protective immunity against West Nile Virus infection in BALB/c mice when combined with West Nile Virus envelope domain III (EDIII) protein in a nasal vaccine. We found that three of the five mast cell activators, ST101036, ST048871, and R529877, evoked high levels of EDIII-specific antibody and conferred comparable levels of protection against WNV challenge. The level of protection provided by these small molecule mast cell activators was comparable to the protection evoked by M7 (67%) but markedly higher than the levels seen with mice immunized with EDIII alone (no adjuvant 33%). Thus, novel small molecule mast cell activators identified by high throughput screening are as efficacious as previously described mast cell activators when used as nasal vaccine adjuvants and represent next-generation mast cell activators for evaluation in mucosal vaccine studies.

Cytokine Storm Syndrome in SARS-CoV-2 Infections: A Functional Role of Mast Cells

Cytokine storm syndrome is a cascade of escalated immune responses disposing the immune system to exhaustion, which might ultimately result in organ failure and fatal respiratory distress. Infection with severe acute respiratory syndrome-coronavirus-2 can result in uncontrolled production of cytokines and eventually the development of cytokine storm syndrome. Mast cells may react to viruses in collaboration with other cells and lung autopsy findings from patients that died from the coronavirus disease that emerged in 2019 (COVID-19) showed accumulation of mast cells in the lungs that was thought to be the cause of pulmonary edema, inflammation, and thrombosis. In this review, we present evidence that a cytokine response by mast cells may initiate inappropriate antiviral immune responses and cause the development of cytokine storm syndrome. We also explore the potential of mast cell activators as adjuvants for COVID-19 vaccines and discuss the medications that target the functions of mast cells and could be of value in the treatment of COVID-19. Recognition of the cytokine storm is crucial for proper treatment of patients and preventing the release of mast cell mediators, as impeding the impacts imposed by these mediators could reduce the severity of COVID-19.

M2e-Based Influenza Vaccines with Nucleoprotein: A Review

Discovery of conserved antigens for universal influenza vaccines warrants solutions to a number of concerns pertinent to the currently licensed influenza vaccines, such as annual reformulation and mismatching with the circulating subtypes. The latter causes low vaccine efficacies, and hence leads to severe disease complications and high hospitalization rates among susceptible and immunocompromised individuals. A universal influenza vaccine ensures cross-protection against all influenza subtypes due to the presence of conserved epitopes that are found in the majority of, if not all, influenza types and subtypes, e.g., influenza matrix protein 2 ectodomain (M2e) and nucleoprotein (NP). Despite its relatively low immunogenicity, influenza M2e has been proven to induce humoral responses in human recipients. Influenza NP, on the other hand, promotes remarkable anti-influenza T-cell responses. Additionally, NP subunits are able to assemble into particles which can be further exploited as an adjuvant carrier for M2e peptide. Practically, the T-cell immunodominance of NP can be transferred to M2e when it is fused and expressed as a chimeric protein in heterologous hosts such as Escherichia coli without compromising the antigenicity. Given the ability of NP-M2e fusion protein in inducing cross-protective anti-influenza cell-mediated and humoral immunity, its potential as a universal influenza vaccine is therefore worth further exploration.

Broadly Protective CD8+ T Cell Immunity to Highly Conserved Epitopes Elicited by Heat Shock Protein gp96-Adjuvanted Influenza Monovalent Split Vaccine

Currently, immunization with inactivated influenza virus vaccines is the most prevalent method to prevent infections. However, licensed influenza vaccines provide only strain-specific protection and need to be updated and administered yearly; thus, new vaccines that provide broad protection against multiple influenza virus subtypes are required. In this study, we demonstrated that intradermal immunization with gp96-adjuvanted seasonal influenza monovalent H1N1 split vaccine could induce cross-protection against both group 1 and group 2 influenza A viruses in BALB/c mouse models. Vaccination in the presence of gp96 induced an apparently stronger antigen-specific T cell response than split vaccine alone. Immunization with the gp96-adjuvanted vaccine also elicited an apparent cross-reactive CD8⁺ T cell response that targeted the conserved epitopes across different influenza virus strains. These cross-reactive CD8⁺ T cells might be recalled from a pool of memory cells established after vaccination and recruited from extrapulmonary sites to facilitate viral clearance. Of note, six highly conserved CD8⁺ T epitopes from the viral structural proteins hemagglutinin (HA), M1, nucleoprotein (NP), and PB1 were identified to play a synergistic role in gp96-mediated cross-protection. Comparative analysis showed that most of conservative epitope-specific cytotoxic T lymphocytes (CTLs) apparently induced by heterologous virus infection were also activated by gp96-adjuvanted vaccine, thus resulting in broader protective CD8⁺ T cell responses. Our results demonstrated the advantage of adding gp96 to an existing seasonal influenza vaccine to improve its ability to provide better cross-protection.IMPORTANCE Owing to continuous mutations in hemagglutinin (HA) or neuraminidase (NA) or recombination of the gene segments between different strains, influenza viruses can escape the immune responses developed by vaccination. Thus, new strategies aimed to efficiently activate immune response that targets to conserved regions among different influenza viruses are urgently needed in designing broad-spectrum influenza vaccine. Heat shock protein gp96 is currently the only natural T cell adjuvant with special ability to cross-present coupled antigen to major histocompatibility complex class I (MHC-I) molecule and activate the downstream antigen-specific CTL response. In this study, we demonstrated the advantages of adding gp96 to monovalent split influenza virus vaccine to improve its ability to provide cross-protection in the BALB/c mouse model and proved that a gp96-activated cross-reactive CTL response is indispensable in our vaccine strategy. Due to its unique adjuvant properties, gp96 might be a promising adjuvant for designing new broad-spectrum influenza vaccines.

Enhancing Immune Response and Heterosubtypic Protection Ability of Inactivated H7N9 Vaccine by Using STING Agonist as a Mucosal Adjuvant

Influenza vaccines for H7N9 subtype have shown low immunogenicity in human clinical trials. Using novel adjuvants might represent the optimal available option in vaccine development. In this study, we demonstrated that the using of the STING agonist cGAMP as a mucosal adjuvant is effective in enhancing humoral, cellular and mucosal immune responses of whole virus, inactivated H7N9 vaccine in mice. A single dose of immunization was able to completely protect mice against a high lethal doses of homologous virus challenge with an significant dose-sparing effect. We also found that intranasal co-administration of H7N9 vaccine with cGAMP could provide effective cross protection against H1N1, H3N2, and H9N2 influenza virus. Furthermore, cGAMP induced significantly higher nucleoprotein specific CD4⁺ and CD8⁺ T cells responses in immunized mice, as well as upregulated the IFN-γ and Granzyme B expression in the lung tissue of mice in the early stages post a heterosubtypic virus challenge. These results indicated that STING agonist cGAMP was expected to be an effective mucosal immune adjuvant for pre-pandemic vaccines such as H7N9 vaccines, and the cGAMP combined nasal inactivated influenza vaccine will also be a promising strategy for development of broad-spectrum influenza vaccines.

Improving Cross-Protection against Influenza Virus Using Recombinant Vaccinia Vaccine Expressing NP and M2 Ectodomain Tandem Repeats

Conventional influenza vaccines need to be designed and manufactured yearly. However, they occasionally provide poor protection owing to antigenic mismatch. Hence, there is an urgent need to develop universal vaccines against influenza virus. Using nucleoprotein (NP) and extracellular domain of matrix protein 2 (M2e) genes from the influenza A virus A/Beijing/30/95 (H3N2), we constructed four recombinant vaccinia virus-based influenza vaccines carrying NP fused with one or four copies of M2e genes in different orders. The recombinant vaccinia viruses were used to immunize BALB/C mice. Humoral and cellular responses were measured, and then the immunized mice were challenged with the influenza A virus A/Puerto Rico/8/34 (PR8). NP-specific humoral response was elicited in mice immunized with recombinant vaccinia viruses carrying full-length NP, while robust M2e-specific humoral response was elicited only in the mice immunized with recombinant vaccinia viruses carrying multiple copies of M2e. All recombinant viruses elicited NP- and M2e-specific cellular immune responses in mice. Only immunization with RVJ-4M2eNP induced remarkably higher levels of IL-2 and IL-10 cytokines specific to M2e. Furthermore, RVJ-4M2eNP immunization provided the highest cross-protection in mice challenged with 20 MLD₅₀ of PR8. Therefore, the cross-protection potentially correlates with both NP and M2e-specific humoral and cellular immune responses induced by RVJ-4M2eNP, which expresses a fusion antigen of full-length NP preceded by four M2e repeats. These results suggest that the rational fusion of NP and multiple M2e antigens is critical toward inducing protective immune responses, and the 4M2eNP fusion antigen may be employed to develop a universal influenza vaccine.

Identification of Novel Mast Cell Activators Using Cell-Based High-Throughput Screening

Mast cells (MCs) are known to regulate innate and adaptive immunity. MC activators have recently been described as safe and effective vaccine adjuvants. Many currently known MC activators are inadequate for in vivo applications, however, and research on identifying novel MC activators is limited. In this study, we identified novel MC activators by using high-throughput screening (HTS) assays using approximately 55,000 small molecules. Data sets obtained by the primary HTS assays were statistically evaluated using quality control rules and the B-score calculation, and compounds with B-scores of >3.0 were chosen as mast cell activators (hits). These hits were re-evaluated with secondary and tertiary HTS assays, followed by further statistical analysis. From these hits, we selected 15 compounds that caused degranulation in murine and human MCs, with potential for flexible chemical modification for further study. Among these 15 compounds, ST101036, ST029248, and ST026567 exhibited higher degranulation potency than other hit compounds in both human and mouse MCs. In addition, the 15 compounds identified promote de novo synthesis of cytokines and induce the release of eicosanoids from human and mouse MCs. HTS enabled us to identify small-molecule MC activators with unique properties that may be useful as vaccine adjuvants.

Nucleoprotein vaccine induces cross-protective cytotoxic T lymphocytes against both lineages of influenza B virus

Purpose

The influenza B virus diverges into two antigenically distinct lineages: B/Yamagata and B/Victoria. Influenza B is the dominant circulating virus during some influenza seasons, and recent data demonstrated that influenza A and B infection similarly cause severe clinical symptoms in hospitalized patients. Nucleoprotein (NP) is a good target for a universal influenza vaccine. This study investigated whether NP epitope variation within two lineages affects the dominant cytotoxic T lymphocyte (CTL) responses induced by vaccination and the resultant protective immunity.

Materials and Methods

The NP of B/Yamagata/16/1988, the representative strain of the Yamagata lineage, includes a dominant CTL epitope, FSPIRITFL, while B/Shangdong/7/1997 from the Victoria lineage has one amino acid difference in this sequence, FSPIRVTFL. Two recombinant replication-deficient adenovirus (rAd)-vectored vaccines expressing either NP were prepared (rAd/B-NP(I) and rAd/B-NP(V), respectively) and administered to BALB/c mice intranasally. To examine the efficacy of vaccination, antibody responses, CTL responses, and morbidity/mortality after challenge were measured.

Results

Both vaccines induce similar antibody and CD8 T-cell responses cross-reacting to both epitopes, and also confer cross-protection against both lineages regardless of amino acid difference.

Conclusion

The rAd-vectored vaccine expressing the NP could be developed as universal influenza B vaccine which provides broader protection.

OVX836 a recombinant nucleoprotein vaccine inducing cellular responses and protective efficacy against multiple influenza A subtypes

Inactivated influenza vaccines (IIVs) lack broad efficacy. Cellular immunity to a conserved internal antigen, the nucleoprotein (NP), has been correlated to protection against pandemic and seasonal influenza and thus could have the potential to broaden vaccine efficacy. We developed OVX836, a recombinant protein vaccine based on an oligomerized NP, which shows increased uptake by dendritic cells and immunogenicity compared with NP. Intramuscular immunization in mice with OVX836 induced strong NP-specific CD4+ and CD8+ T-cell systemic responses and established CD8+ tissue memory T cells in the lung parenchyma. Strikingly, OVX836 protected mice against viral challenge with three different influenza A subtypes, isolated several decades apart and induced a reduction in viral load. When co-administered with IIV, OVX836 was even more effective in reducing lung viral load.

Circulating influenza A virus (IAV) strains differ in their surface proteins each year, and vaccines eliciting an immune response to these proteins are often only partially protective. Internal viral proteins, such as the nucleoprotein (NP), are highly conserved, and cellular immunity to NP has been correlated with protection from diverse strains. However, current IAV vaccines induce a poor immune response to NP. In this study, led by Fergal Hill from Osivax, researchers develop an oligomeric version of NP with improved immunogenicity. Vaccination of mice with oligomeric NP results in an improved NP-specific T-cell response, including CD8⁺ tissue memory T cells in the lung, and protects mice against three different IAV subtypes. Co-administration with the currently used inactivated influenza vaccine further improves protection against virus infection in mice. These results encourage further pre-clinical and clinical development for this vaccine candidate.

Production and application of anti-nucleoprotein IgY antibodies for influenza A virus detection in swine

Influenza A virus (IAV) causes an important respiratory disease in mammals and birds leading to concerns in animal production industry and public health. Usually, antibodies produced in mammals are employed in diagnostic tests. However, due to animal welfare concerns, technical advantages and the high cost of production, alternatives to the production of antibodies in mammals have been investigated. The aim of this study was to produce egg yolk immunoglobulin (IgY) in laying hens against a highly conserved protein (nucleoprotein- NP) of IAV and to evaluate the application of anti-NP IgY antibodies in virus detection by immunocytochemistry (ICC) and immunohistochemistry (IHC). Three laying hens of the White Leghorn line were inoculated seven times with a recombinant NP protein and their eggs collected seven days after the 3rd, 5th and 7th inoculations. Immunoglobulin Y antibodies were purified from egg yolk through precipitation with ammonium sulfate. The titers and specificity of the purified antibodies were determined by ELISA, western blotting, ICC and IHC. High levels of specific anti-NP antibodies were detected by ELISA after the 5th inoculation, reaching a peak after the 7th inoculation. The mean yield of total protein in yolk after the 7th inoculation was 13.5 mg/mL. The use of western blotting and ICC demonstrated that anti-NP IgY binds specifically to NP protein. Moreover, the use of anti-NP IgY antibody in ICC test revealed positive staining of MDCK cells infected with IAV of the three subtypes circulating in swine (H1N1, H1N2, and H3N2). However, no staining was observed in lung tissues through the IHC test. The data obtained showed that anti-NP IgY antibodies bound specifically to influenza virus NP protein, detecting the main virus subtypes circulating in swine, reinforcing their usefulness in the influenza diagnosis.

Mast cell activator compound 48/40 is not an effective adjuvant for UV-attenuated Toxoplasma gondii vaccine

Toxoplasma gondii (T. gondii, Tg) is a globally distributed parasitic protozoan causing different forms of toxoplasmosis in humans. Mast cells (MCs) play a role during T. gondii infection. Several studies suggest that MC activator compound 48/80 (C48/80) may be an effective vaccine adjuvant resulting in a potent and protective antigen-specific immune response against bacteria or virus infections. The present study was performed to determine whether C48/80 had adjuvant activity for ultraviolet (UV)-attenuated T. gondii vaccine to induce protective immune responses against T. gondii in mouse model. Kunming mice were divided into the following groups: naive mice, naive mice administrated with C48/80 intraperitoneal (i.p.) injection, mice infected by i.p. injection of 10⁴ T. gondii RH strain alone (Tg group), mice infected with 10⁴ RH tachyzoites plus C48/80 administration (Tg + C48/80), mice immunized with UV-Tg alone, and mice immunized with UV-Tg plus C48/80 administration (UV-Tg + C48/80). All the vaccinated mice were challenged with 10⁴ tachyzoites of T. gondii RH strain at the same time as the primary infection. The survival rates, liver histopathologies, liver parasite burdens, and mRNA expression levels of Th1 and Th2 cytokines in the livers and spleens detected by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) were compared among the aforementioned groups after primary infection or challenge infection. The results showed that, compared to the Tg group or Tg + C48/80 group, the UV-Tg + Tg group and UV-Tg + C48/80 + Tg group had significantly prolonged survival time, lower liver histopathological scores, decreased liver parasite burdens, and increased levels of Th1 and Th2 cytokines in the livers and spleens. There was no significant difference of survival time between the UV-Tg + Tg group and the UV-Tg + C48/80 + Tg group; however, the UV-Tg + C48/80 + Tg group showed higher parasite burden, more severe liver histopathology, and decreased IL-4 level compared to the UV-Tg + Tg group. These results indicate that C48/80 had no adjuvant activity for the immunization induced by UV-attenuated T. gondii vaccine.

Presenting Influenza A M2e Antigen on Recombinant Spores of Bacillus subtilis

Effective vaccination against influenza virus infection is a serious problem mainly due to antigenic variability of the virus. Among many of investigated antigens, the extracellular domain of the M2 protein (M2e) features high homology in all strains of influenza A viruses and antibodies against M2e and is protective in animal models; this makes it a potential candidate for generation of a universal influenza vaccine. However, due to the low immunogenicity of the M2e, formulation of a vaccine based on this antigen requires some modification to induce effective immune responses. In this work we evaluated the possible use of Bacillus subtilis spores as a carrier of the Influenza A M2e antigen in mucosal vaccination. A tandem repeat of 4 consensus sequences coding for human-avian-swine-human M2e (M2eH-A-S-H) peptide was fused to spore coat proteins and stably exposed on the spore surface, as demonstrated by the immunostaining of intact, recombinant spores. Oral immunization of mice with recombinant endospores carrying M2eH-A-S-H elicited specific antibody production without the addition of adjuvants. Bacillus subtilis endospores can serve as influenza antigen carriers. Recombinant spores constructed in this work showed low immunogenicity although were able to induce antibody production. The System of influenza antigen administration presented in this work is attractive mainly due to the omitting time-consuming and cost-intensive immunogen production and purification. Therefore modification should be made to increase the immunogenicity of the presented system.