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The development of an effective and broadly protective influenza vaccine against circulating and emerging strains remains elusive. In this study, we evaluated a potentially universal influenza vaccine based on single-component self-assembling protein nanoparticles (1c-SApNPs) presenting the conserved matrix protein 2 ectodomain (M2e) from influenza A and B viruses (IAV and IBV, respectively). We previously designed a tandem antigen comprising three IAV M2e domains of human, avian/swine, and human/swine origins (termed M2ex3). The M2ex3-presenting 1c-SApNPs conferred complete protection in mice against sequential lethal challenges with H1N1 and H3N2. To broaden this protection to cover IBVs, we designed a series of antigens incorporating different arrangements of three IAV M2e domains and three copies of IBV M2e. Tandem repeats of IAV and IBV (termed influenza A-B) M2e arrayed on the I3-01v9a 60-mer 1c-SApNP, when formulated with an oil-in-water emulsion adjuvant, generated greater M2e-specific immunogenicity and protective efficacy than the soluble influenza A-B M2e trimer, indicated by higher survival rates and reduced weight loss post-challenge. Importantly, one of the influenza A-B M2e SApNP constructs elicited 100% protection against a lethal influenza A/Puerto Rico/8/1934 (H1N1) challenge in mice and 70% protection against a lethal influenza B/Florida/4/2006 (Yamagata lineage) challenge, the latter of which has not been reported in the literature to date. Our study thus provides a promising M2e-based single-component universal vaccine candidate against the two major types of influenza virus circulating in humans. [ABSTRACT FROM AUTHOR]

ABSTRACTIntroduction Vaccination is the most effective method to control the prevalence of seasonal influenza and the most widely used influenza vaccine is the inactivated influenza vaccine (IIV). Each season, the influenza vaccine must be updated to be most effective against current circulating variants. Therefore, developing a universal influenza vaccine (UIV) that can elicit both broad and durable protection is of the utmost importance.Area covered This review summarizes and compares the available influenza vaccines in the market and inactivation methods used for manufacturing IIVs. Then, we discuss the latest progress of the UIV development in the IIV format and the challenges to address for moving these vaccine candidates to clinical trials and commercialization. The literature search was based on the Centers for Disease Control and Prevention (CDC) and the PubMed databases.Expert opinion The unmet need for UIV is the primary aim of developing the next generation of influenza vaccines. The IIV has high antigenicity and a refined manufacturing process compared to most other formats. Developing the UIV in IIV format is a promising direction with advanced biomolecular technologies and next-generation adjuvant. It also inspires the development of universal vaccines for other infectious diseases.

Introduction. Influenza is a disease caused by a widespread virus with pandemic potential. Frequently, individuals vaccinated against seasonal influenza virus are still susceptible to the disease, indicating the need to improve the immunogenic potential of existing vaccines. To assess the efficacy of influenza virus vaccines, immune response only to a single viral antigen — hemagglutinin molecule, is taken into consideration. However, according to preclinical and clinical studies, neuraminidase (NA) stimulates cross-protective immunity, which is effective against not only homologous but also drifted variants of influenza A virus. Materials and methods. In the present study, we investigated the ability of previously selected conserved linear B-cell NA epitopes (SGYSGK, SWPDGK, EECSCYPK, VELIRGRK) to enhance the immunogenicity of an inactivated whole-virion influenza vaccine based on the model strain PR8 (iPR8). BALB/c mice were injected with iPR8 in combination with one of the peptides intramuscularly three times at two-week intervals. Blood samples were collected 14 days after the last immunization, after which the mice were challenged with heterosubtypic influenza viruses H1N1pdm09 and H3N2. Results. All immunized mice showed induction of H1N1 (PR8)-specific IgG antibodies two weeks after the third immunization. The group of mice immunized with the iPR8 vaccine preparation in combination with VELIRGRK peptide showed the most pronounced induction of IgG antibodies to the H6N1 reassortant strain, the NA of which corresponds to the iPR8 virus, indicating the ability of the NA peptide to stimulate the production of NA-specific antibodies. However, the antibodies produced after immunization were not capable to inhibit the NA enzymatic activity. Despite this, mice immunized with iPR8 in combination with anti-NA peptides showed a higher survival rate after infection with heterologous virulent influenza viruses: A/California/07/09 (H1N1pdm09) and A/Philippines/2/82 (H3N2) compared to the PBS and iPR8 groups. Conclusion. Thus, the study demonstrated the immune-potentiating effect of individual peptides corresponding to conservative linear epitopes of the NA molecule in combination with a standard inactivated influenza vaccine, which made it possible to improve the protective effect of the vaccine against heterosubtypic influenza viruses.

Vaccination with transiently activated replication-competent controlled herpesviruses (RCCVs) expressing influenza A virus hemagglutinins broadly protects mice against lethal influenza virus challenges. The non-replicating RCCVs can be activated to transiently replicate with high efficiency. Activation involves a brief heat treatment to the epidermal administration site in the presence of a drug. The drug co-control is intended as a block to inadvertent reactivation in the nervous system and, secondarily, viremia under adverse conditions. While the broad protective effects observed raise an expectation that RCCVs may be developed as universal flu vaccines, the need for administering a co-activating drug may dampen enthusiasm for such a development. To replace the drug co-control, we isolated keratin gene promoters that were active in skin cells but inactive in nerve cells and other cells in vitro. In a mouse model of lethal central nervous system (CNS) infection, the administration of a recombinant that had the promoter of the infected cell protein 8 (ICP8) gene of a wild-type herpes simplex virus 1 (HSV-1) strain replaced by a keratin promoter did not result in any clinical signs, even at doses of 500 times wild-type virus LD50. Replication of the recombinant was undetectable in brain homogenates. Second-generation RCCVs expressing a subtype H1 hemagglutinin (HA) were generated in which the infected cell protein 4 (ICP4) genes were controlled by a heat switch and the ICP8 gene by the keratin promoter. In mice, these RCCVs replicated efficiently and in a heat-controlled fashion in the epidermal administration site. Immunization with the activated RCCVs induced robust neutralizing antibody responses against influenza viruses and protected against heterologous and cross-group influenza virus challenges. [ABSTRACT FROM AUTHOR]

Currently, vaccination with influenza vaccines is still an effective strategy to prevent infection by seasonal influenza virus in spite of some drawbacks with them. However, due to the rapid evolution of influenza viruses, including seasonal influenza viruses and emerging zoonotic influenza viruses, there is an urgent need to develop broad-spectrum influenza vaccines to cope with the evolution of influenza viruses. Nucleic acid vaccines might meet the requirements well. Nucleic acid vaccines are classified into DNA vaccines and RNA vaccines. Both types induced potent cellular and humoral immune responses, showing great promise for the development of universal influenza vaccines. In this review, the current status of an influenza universal nucleic acid vaccine was summarized. [ABSTRACT FROM AUTHOR]

Every year, influenza virus infections cause significant morbidity and mortality worldwide. They pose a substantial burden of disease, in terms of not only health but also the economy. Owing to the ability of influenza viruses to continuously evolve, annual seasonal influenza vaccines are necessary as a prophylaxis. However, current influenza vaccines against seasonal strains have limited effectiveness and require yearly reformulation due to the virus undergoing antigenic drift or shift. Vaccine mismatches are common, conferring suboptimal protection against seasonal outbreaks, and the threat of the next pandemic continues to loom. Therefore, there is a great need to develop a universal influenza vaccine (UIV) capable of providing broad and durable protection against all influenza virus strains. In the quest to develop a UIV that would obviate the need for annual vaccination and formulation, a multitude of strategies is currently underway. Promising approaches include targeting the highly conserved epitopes of haemagglutinin (HA), neuraminidase (NA), M2 extracellular domain (M2e) and internal proteins of the influenza virus. The identification and characterization of broadly neutralizing antibodies (bnAbs) targeting conserved regions of the viral HA protein, in particular, have provided important insight into novel vaccine designs and platforms. This review discusses universal vaccine approaches presently under development, with an emphasis on those targeting the highly conserved stalk of the HA protein, recent technological advancements used and the future prospects of a UIV in terms of its advantages, developmental obstacles and potential shortcomings. [ABSTRACT FROM AUTHOR]

The nucleoprotein (NP) is a vital target for the heterosubtypic immunity of CD8+ cytotoxic T lymphocytes (CTLs) due to its conservation among influenza virus subtypes. To further enhance the T cell immunity of NP, autophagy-inducing peptide C5 (AIP-C5) from the CFP10 protein of Mycobacterium tuberculosis was used. Mice were immunized intranasally (i.n.) with human adenoviral vectors, HAd-C5-NP(H7N9) or HAd-NP(H7N9), expressing NP of an H7N9 influenza virus with or without the AIP-C5, respectively. Both vaccines developed similar levels of NP-specific systemic and mucosal antibody titers; however, there was a significantly higher number of NP-specific CD8 T cells secreting interferon-gamma (IFN-γ) in the HAd-C5-NP(H7N9) group than in the HAd-NP(H7N9) group. The HAd-C5-NP(H7N9) vaccine provided better protection following the challenge with A/Puerto Rico/8/1934(H1N1), A/Hong Kong/1/68(H3N2), A/chukkar/MN/14951-7/1998(H5N2), A/goose/Nebraska/17097/2011(H7N9), or A/Hong Kong/1073/1999(H9N2) influenza viruses compared to the HAd-NP(H7N9) group. The autophagy transcriptomic gene analysis of the HAd-C5-NP(H7N9) group revealed the upregulation of some genes involved in the positive regulation of the autophagy process. The results support further exploring the use of NP and AIP-C5 for developing a universal influenza vaccine for pandemic preparedness. [ABSTRACT FROM AUTHOR]

Summary: Background: The development of a universal influenza virus vaccine, to protect against both seasonal and pandemic influenza A viruses, is a long-standing public health goal. The conserved stalk domain of haemagglutinin (HA) is a promising vaccine target. However, the stalk is immunosubdominant. As such, innovative approaches are required to elicit robust immunity against this domain. In a previously reported observer-blind, randomised placebo-controlled phase I trial (NCT03300050), immunisation regimens using chimeric HA (cHA)-based immunogens formulated as inactivated influenza vaccines (IIV) −/+ AS03 adjuvant, or live attenuated influenza vaccines (LAIV), elicited durable HA stalk-specific antibodies with broad reactivity. In this study, we sought to determine if these vaccines could also boost T cell responses against HA stalk, and nucleoprotein (NP). Methods: We measured interferon-γ (IFN-γ) responses by Enzyme-Linked ImmunoSpot (ELISpot) assay at baseline, seven days post-prime, pre-boost and seven days post-boost following heterologous prime:boost regimens of LAIV and/or adjuvanted/unadjuvanted IIV-cHA vaccines. Findings: Our findings demonstrate that immunisation with adjuvanted cHA-based IIVs boost HA stalk-specific and NP-specific T cell responses in humans. To date, it has been unclear if HA stalk-specific T cells can be boosted in humans by HA-stalk focused universal vaccines. Therefore, our study will provide valuable insights for the design of future studies to determine the precise role of HA stalk-specific T cells in broad protection. Interpretation: Considering that cHA-based vaccines also elicit stalk-specific antibodies, these data support the further clinical advancement of cHA-based universal influenza vaccine candidates. Funding: This study was funded in part by the Bill and Melinda Gates Foundation (BMGF).

The development of an effective and broadly protective influenza vaccine against circulating and emerging strains remains elusive. In this study, we evaluated a potentially universal influenza vaccine based on single-component self-assembling protein nanoparticles (1c-SApNPs) presenting the conserved matrix protein 2 ectodomain (M2e) from influenza A and B viruses (IAV and IBV, respectively). We previously designed a tandem antigen comprising three IAV M2e domains of human, avian/swine, and human/swine origins (termed M2ex3). The M2ex3-presenting 1c-SApNPs conferred complete protection in mice against sequential lethal challenges with H1N1 and H3N2. To broaden this protection to cover IBVs, we designed a series of antigens incorporating different arrangements of three IAV M2e domains and three copies of IBV M2e. Tandem repeats of IAV and IBV (termed influenza A-B) M2e arrayed on the I3-01v9a 60-mer 1c-SApNP, when formulated with an oil-in-water emulsion adjuvant, generated greater M2e-specific immunogenicity and protective efficacy than the soluble influenza A-B M2e trimer, indicated by higher survival rates and reduced weight loss post-challenge. Importantly, one of the influenza A-B M2e SApNP constructs elicited 100% protection against a lethal influenza A/Puerto Rico/8/1934 (H1N1) challenge in mice and 70% protection against a lethal influenza B/Florida/4/2006 (Yamagata lineage) challenge, the latter of which has not been reported in the literature to date. Our study thus provides a promising M2e-based single-component universal vaccine candidate against the two major types of influenza virus circulating in humans.

Zoonotic transmission of H5N1 highly pathogenic avian influenza virus (HPAIV) into the human population is an increasing global threat. The recent 2022 HPAIV outbreak significantly highlighted this possibility, increasing concern in the general population. The clinical outcomes of H5N1 influenza virus exposure can be determined by an individual’s primary influenza virus infection (imprinting) or vaccination status. Immunological imprinting with Group 1 - (H1N1, H2N2, and H2N3) increases survival rates following H5N1 viral infection compared to Group 2 - (H3N2) imprinted individuals. Vaccination against H5N1 influenza viruses can offer protection to at-risk populations; however, stockpiled inactivated H5N1 influenza vaccines are not readily available to the public. We hypothesize that the immunological response to vaccination and subsequent clinical outcome following H5N1 influenza virus infection is correlated with the immunological imprinting status of an individual. To test this hypothesis, our lab established a ferret pre-immune model of disease. Naïve ferrets were intranasally inoculated with seasonal influenza viruses and allowed to recover for 84  days prior to H5N1 virus infection. Ferrets imprinted following H1N1 and H2N3 virus infections were completely protected against lethal H5N1 influenza virus challenge (100% survival), with few to no clinical symptoms. In comparison, H3N2 influenza virus)imprinted ferrets had severe clinical symptoms, delayed disease progression, and a sublethal phenotype (40% mortality). Consecutive infections with H1N1 influenza viruses followed by an H3N2 influenza virus infection did not abrogate the immune protection induced by the original H1N1 influenza virus infection. In addition, ferrets consecutively infected with H1N1 and H2N3 viruses had no clinical symptoms or weight loss. H3N2 pre-immune ferrets were vaccinated with a broadly reactive H5 HA-based or H1 NA-based vaccine (Hu-CO 2). These ferrets were protected against H5N1 influenza virus challenge, whereas ferrets vaccinated with the H1N1 wild-type CA/09 rHA vaccine had similar phenotypes as non-vaccinated H3N2-imprinted ferrets with 40% survival. Overall, Group 2 imprinted ferrets, which were vaccinated with heterologous Group 1 HA vaccines, had redirected immune responses to Group 1 influenza viral antigens and rescued a sublethal phenotype to complete protection. [ABSTRACT FROM AUTHOR]

Currently, vaccination with influenza vaccines is still an effective strategy to prevent infection by seasonal influenza virus in spite of some drawbacks with them. However, due to the rapid evolution of influenza viruses, including seasonal influenza viruses and emerging zoonotic influenza viruses, there is an urgent need to develop broad-spectrum influenza vaccines to cope with the evolution of influenza viruses. Nucleic acid vaccines might meet the requirements well. Nucleic acid vaccines are classified into DNA vaccines and RNA vaccines. Both types induced potent cellular and humoral immune responses, showing great promise for the development of universal influenza vaccines. In this review, the current status of an influenza universal nucleic acid vaccine was summarized.

Zoonotic transmission of H5N1 highly pathogenic avian influenza virus (HPAIV) into the human population is an increasing global threat. The recent 2022 HPAIV outbreak significantly highlighted this possibility, increasing concern in the general population. The clinical outcomes of H5N1 influenza virus exposure can be determined by an individual’s primary influenza virus infection (imprinting) or vaccination status. Immunological imprinting with Group 1 - (H1N1, H2N2, and H2N3) increases survival rates following H5N1 viral infection compared to Group 2 - (H3N2) imprinted individuals. Vaccination against H5N1 influenza viruses can offer protection to at-risk populations; however, stockpiled inactivated H5N1 influenza vaccines are not readily available to the public. We hypothesize that the immunological response to vaccination and subsequent clinical outcome following H5N1 influenza virus infection is correlated with the immunological imprinting status of an individual. To test this hypothesis, our lab established a ferret pre-immune model of disease. Naïve ferrets were intranasally inoculated with seasonal influenza viruses and allowed to recover for 84 days prior to H5N1 virus infection. Ferrets imprinted following H1N1 and H2N3 virus infections were completely protected against lethal H5N1 influenza virus challenge (100% survival), with few to no clinical symptoms. In comparison, H3N2 influenza virus-imprinted ferrets had severe clinical symptoms, delayed disease progression, and a sublethal phenotype (40% mortality). Consecutive infections with H1N1 influenza viruses followed by an H3N2 influenza virus infection did not abrogate the immune protection induced by the original H1N1 influenza virus infection. In addition, ferrets consecutively infected with H1N1 and H2N3 viruses had no clinical symptoms or weight loss. H3N2 pre-immune ferrets were vaccinated with a broadly reactive H5 HA-based or H1 NA-based vaccine (Hu-CO 2). These ferrets were protected against H5N1 influenza virus challenge, whereas ferrets vaccinated with the H1N1 wild-type CA/09 rHA vaccine had similar phenotypes as non-vaccinated H3N2-imprinted ferrets with 40% survival. Overall, Group 2 imprinted ferrets, which were vaccinated with heterologous Group 1 HA vaccines, had redirected immune responses to Group 1 influenza viral antigens and rescued a sublethal phenotype to complete protection.

Antigenic changes in surface proteins of the influenza virus may cause the emergence of new variants that necessitate the reformulation of influenza vaccines every year. Universal influenza vaccine that relies on conserved regions can potentially be effective against all strains regardless of any antigenic changes and as a result, it can bring enormous public health impact and economic benefit worldwide. Here, a conserved peptide (HA288–107) on the stalk domain of hemagglutinin glycoprotein is identified among highly pathogenic influenza viruses. Five top-ranked B-cell and twelve T-cell epitopes were recognized by epitope mapping approaches and the corresponding Human Leukocyte Antigen alleles to T-cell epitopes showed high population coverage (>99%) worldwide. Moreover, molecular docking analysis indicated that VLMENERTL and WTYNAELLV epitopes have high binding affinity to the antigen-binding groove of the HLA-A*02:01 and HLA-A*68:02 molecules, respectively. Theoretical physicochemical properties of the peptide were assessed to ensure its thermostability and hydrophilicity. The results suggest that the HA288–107 peptide can be a promising antigen for universal influenza vaccine design. However, in vitro and in vivo analyses are needed to support and evaluate the effectiveness of the peptide as an immunogen for vaccine development. [ABSTRACT FROM AUTHOR]

The nucleoprotein (NP) is a vital target for the heterosubtypic immunity of CD8+ cytotoxic T lymphocytes (CTLs) due to its conservation among influenza virus subtypes. To further enhance the T cell immunity of NP, autophagy-inducing peptide C5 (AIP-C5) from the CFP10 protein of Mycobacterium tuberculosis was used. Mice were immunized intranasally (i.n.) with human adenoviral vectors, HAd-C5-NP(H7N9) or HAd-NP(H7N9), expressing NP of an H7N9 influenza virus with or without the AIP-C5, respectively. Both vaccines developed similar levels of NP-specific systemic and mucosal antibody titers; however, there was a significantly higher number of NP-specific CD8 T cells secreting interferon-gamma (IFN-γ) in the HAd-C5-NP(H7N9) group than in the HAd-NP(H7N9) group. The HAd-C5-NP(H7N9) vaccine provided better protection following the challenge with A/Puerto Rico/8/1934(H1N1), A/Hong Kong/1/68(H3N2), A/chukkar/MN/14951-7/1998(H5N2), A/goose/Nebraska/17097/2011(H7N9), or A/Hong Kong/1073/1999(H9N2) influenza viruses compared to the HAd-NP(H7N9) group. The autophagy transcriptomic gene analysis of the HAd-C5-NP(H7N9) group revealed the upregulation of some genes involved in the positive regulation of the autophagy process. The results support further exploring the use of NP and AIP-C5 for developing a universal influenza vaccine for pandemic preparedness.

Influenza A viruses (IAVs) exist as distinct serological subtypes, with limited antibody cross reactivity compared with T‐cell responses, leading to universal vaccines that elicit robust T‐cell responses entering clinical trials to combat pandemic and zoonotic outbreaks. Previously we have extensively characterized the viral‐vectored universal vaccine, Wyeth/IL‐15/5flu, a group 1 hemagglutinin, H5N1‐based vaccine using a vaccinia backbone with interleukin (IL)‐15. The vaccine elicits robust T‐cell responses to provide heterosubtypic protection from lethal infection; however, we have also observed short‐term morbidity of vaccinated mice with a disparity between the effects of sublethal infection with group 1 and 2 IAV strains. At day 3 of H3N2 (group 2 IAV) infection, there was a heavily skewed T helper type 1 response in vaccinated infected mice with overproduction of cytokines and reduced chemokines, whereas H1N1 (group 1 IAV) infection had increased innate cellular responses. These findings suggest that increased and early immune activation by T‐cell activating vaccines may induce mild immunopathology when there is a mismatch between non‐neutralizing antibody and cross‐reactive memory T‐cell responses leading to exuberant cytokine production. Therefore, to avoid overstimulating proinflammatory immune responses upon infection, universal influenza vaccines that elicit strong T‐cell immunity will need a robust cross‐reactive antibody response. [ABSTRACT FROM AUTHOR]

The highly conserved matrix protein 2 ectodomain (M2e) of influenza viruses presents a compelling vaccine antigen candidate for stemming the pandemic threat of the mutation‐prone pathogen, yet the low immunogenicity of the diminutive M2e peptide renders vaccine development challenging. A highly potent M2e nanoshell vaccine that confers broad and durable influenza protectivity under a single vaccination is shown. Prepared via asymmetric ionic stabilization for nanoscopic curvature formation, polymeric nanoshells co‐encapsulating high densities of M2e peptides and stimulator of interferon genes (STING) agonists are prepared. Robust and long‐lasting protectivity against heterotypic influenza viruses is achieved with a single administration of the M2e nanoshells in mice. Mechanistically, molecular adjuvancy by the STING agonist and nanoshell‐mediated prolongation of M2e antigen exposure in the lymph node follicles synergistically contribute to the heightened anti‐M2e humoral responses. STING agonist‐triggered T cell helper functions and extended residence of M2e peptides in the follicular dendritic cell network provide a favorable microenvironment that induces Th1‐biased antibody production against the diminutive antigen. These findings highlight a versatile nanoparticulate design that leverages innate immune pathways for enhancing the immunogenicity of weak immunogens. The single‐shot nanovaccine further provides a translationally viable platform for pandemic preparedness. [ABSTRACT FROM AUTHOR]

Abstract Introduction Despite improvements in medical science and public health, mortality of community-acquired pneumonia (CAP) has barely changed throughout the last 15 years. The current SARS-CoV-2 pandemic has once again highlighted the central importance of acute respiratory infections to human health. The “network of excellence on Community Acquired Pneumonia” (CAPNETZ) hosts the most comprehensive CAP database worldwide including more than 12,000 patients. CAPNETZ connects physicians, microbiologists, virologists, epidemiologists, and computer scientists throughout Europe. Our aim was to summarize the current situation in CAP research and identify the most pressing unmet needs in CAP research. Methods To identify areas of future CAP research, CAPNETZ followed a multiple-step procedure. First, research members of CAPNETZ were individually asked to identify unmet needs. Second, the top 100 experts in the field of CAP research were asked for their insights about the unmet needs in CAP (Delphi approach). Third, internal and external experts discussed unmet needs in CAP at a scientific retreat. Results Eleven topics for future CAP research were identified: detection of causative pathogens, next generation sequencing for antimicrobial treatment guidance, imaging diagnostics, biomarkers, risk stratification, antiviral and antibiotic treatment, adjunctive therapy, vaccines and prevention, systemic and local immune response, comorbidities, and long-term cardio-vascular complications. Conclusion Pneumonia is a complex disease where the interplay between pathogens, immune system and comorbidities not only impose an immediate risk of mortality but also affect the patients’ risk of developing comorbidities as well as mortality for up to a decade after pneumonia has resolved. Our review of unmet needs in CAP research has shown that there are still major shortcomings in our knowledge of CAP.

Influenza is a global health concern with millions of infections occurring yearly. Seasonal flu vaccines are one way to combat this virus; however, they are poorly protective against influenza as the virus is constantly mutating, particularly at the immunodominant hemagglutinin (HA) head group. A more broadly acting approach involves Computationally Optimized Broadly Reactive Antigen (COBRA). COBRA HA generates a broad immune response that is capable of protecting against mutating strains. Unfortunately, protein-based vaccines are often weekly immunogenic, so to help boost the immune response, we employed the use of acetalated dextran (Ace-DEX) microparticles (MPs) two ways: one to conjugate COBRA HA to the surface and a second to encapsulate cGAMP. To conjugate the COBRA HA to the surface of the Ace-DEX MPs, a poly(L-lactide)-polyethylene glycol co-polymer with a vinyl sulfone terminal group (PLLA-PEG-VS) was used. MPs encapsulating the STING agonist cGAMP were co-delivered with the antigen to form a broadly active influenza vaccine. This vaccine approach was evaluated in vivo with a prime-boost-boost vaccination schedule and illustrated generation of a humoral and cellular response that could protect against a lethal challenge of A/California/07/2009 in BALB/c mice. [ABSTRACT FROM AUTHOR]

Neuraminidase (NA) is an important surface protein on influenza virions, playing an essential role in the viral life cycle and being a key target of the immune system. Despite the importance of NA-based immunity, current vaccines are focused on the hemagglutinin (HA) protein as the target for protective antibodies, and the amount of NA is not standardized in virion-based vaccines. Antibodies targeting NA are predominantly protective, reducing infection severity and viral shedding. Recently, NA-specific monoclonal antibodies have been characterized, and their target epitopes have been identified. This review summarizes the characteristics of NA, NA-specific antibodies, the mechanism of NA inhibition, and the recent efforts towards developing NA-based and NA-incorporating influenza vaccines. [ABSTRACT FROM AUTHOR]

Current seasonal influenza A virus (IAV) vaccines only protect against specific virus and require annual reconstitution to accommodate the viral mutations. A universal influenza vaccination that protects against all IAV strains is urgently needed. The influenza matrix protein 2 ectodomain (M2e) is a potential universal IAV vaccine candidate, but it has a low immunogenicity. ΔA146Ply was proved to be an effective protein adjuvant. Therefore, ΔA146Ply was used as an adjuvant of M2e in this study to evaluate its protective effect against IAV-related infection. Herein, a novel rM2e protein containing multiple M2e originated from different species of IAV was constructed and expressed in Escherichia coli (E. coli). Meanwhile, we also constructed and expressed the rM2e-ΔPly protein in E. coli. These proteins were administered intramuscularly to BALB/c mice. rM2e-ΔPly protein induces higher levels of humoral and cellular responses compared with their comprising protein mixture or rM2e alone. rM2e-ΔPly protein enhances the survival rate, reduces viral loads and inflammatory response in lung challenged with PR8. The serum induced by rM2e-ΔPly protein can protect against PR8 by passive immunity and cross-react with multiple M2e peptides derived from different IAV subtypes. After IAV and Streptococcus pneumoniae (S. pneumoniae) co-infection, rM2e-Ply protein can improve survival, lower viral and bacterial burdens, and diminish inflammatory response in the lungs. These results demonstrate that rM2e-ΔPly protein can significantly protect against influenza virus, IAV and S. pneumoniae co-infection, indicating that rM2e-ΔPly protein has the potential to become a universal influenza vaccine. • ΔA146Ply protein can enhance the humoral and cellular responses of M2e protein. • rM2e-ΔPly protein can significantly protect against influenza A virus and its co-infection with Streptococcus pneumoniae. • rM2e-ΔPly protein has the potential to become a universal influenza vaccine. [ABSTRACT FROM AUTHOR]

Antigenic changes in surface proteins of the influenza virus may cause the emergence of new variants that necessitate the reformulation of influenza vaccines every year. Universal influenza vaccine that relies on conserved regions can potentially be effective against all strains regardless of any antigenic changes and as a result, it can bring enormous public health impact and economic benefit worldwide. Here, a conserved peptide (HA288–107) on the stalk domain of hemagglutinin glycoprotein is identified among highly pathogenic influenza viruses. Five top-ranked B-cell and twelve T-cell epitopes were recognized by epitope mapping approaches and the corresponding Human Leukocyte Antigen alleles to T-cell epitopes showed high population coverage (>99%) worldwide. Moreover, molecular docking analysis indicated that VLMENERTL and WTYNAELLV epitopes have high binding affinity to the antigen-binding groove of the HLA-A*02:01 and HLA-A*68:02 molecules, respectively. Theoretical physicochemical properties of the peptide were assessed to ensure its thermostability and hydrophilicity. The results suggest that the HA288–107 peptide can be a promising antigen for universal influenza vaccine design. However, in vitro and in vivo analyses are needed to support and evaluate the effectiveness of the peptide as an immunogen for vaccine development.

The imperfect effectiveness of seasonal influenza vaccines is often blamed on antigenic mismatch, but even when the match appears good, effectiveness can be surprisingly low. Seasonal influenza vaccines also stand out for their variable effectiveness by age group from year to year and by recent vaccination status. These patterns suggest a role for immune history in influenza vaccine effectiveness, but inference is complicated by uncertainty about the contributions of bias to the estimates themselves. In this review, we describe unexpected patterns in the effectiveness of seasonal influenza vaccination and explain how these patterns might arise as consequences of study design, the dynamics of immune memory, or both. Resolving this uncertainty could lead to improvements in vaccination strategy, including the use of universal vaccines in experienced populations, and the evaluation of vaccine efficacy against influenza and other antigenically variable pathogens.

Introduction: Despite improvements in medical science and public health, mortality of community-acquired pneumonia (CAP) has barely changed throughout the last 15 years. The current SARS-CoV-2 pandemic has once again highlighted the central importance of acute respiratory infections to human health. The "network of excellence on Community Acquired Pneumonia" (CAPNETZ) hosts the most comprehensive CAP database worldwide including more than 12,000 patients. CAPNETZ connects physicians, microbiologists, virologists, epidemiologists, and computer scientists throughout Europe. Our aim was to summarize the current situation in CAP research and identify the most pressing unmet needs in CAP research.Methods: To identify areas of future CAP research, CAPNETZ followed a multiple-step procedure. First, research members of CAPNETZ were individually asked to identify unmet needs. Second, the top 100 experts in the field of CAP research were asked for their insights about the unmet needs in CAP (Delphi approach). Third, internal and external experts discussed unmet needs in CAP at a scientific retreat.Results: Eleven topics for future CAP research were identified: detection of causative pathogens, next generation sequencing for antimicrobial treatment guidance, imaging diagnostics, biomarkers, risk stratification, antiviral and antibiotic treatment, adjunctive therapy, vaccines and prevention, systemic and local immune response, comorbidities, and long-term cardio-vascular complications.Conclusion: Pneumonia is a complex disease where the interplay between pathogens, immune system and comorbidities not only impose an immediate risk of mortality but also affect the patients' risk of developing comorbidities as well as mortality for up to a decade after pneumonia has resolved. Our review of unmet needs in CAP research has shown that there are still major shortcomings in our knowledge of CAP. [ABSTRACT FROM AUTHOR]

Influenza viruses are responsible for millions of cases globally and significantly threaten public health. Since pandemic and zoonotic influenza viruses have emerged in the last 20 years and some of the viruses have resulted in high mortality in humans, a universal influenza vaccine is needed to provide comprehensive protection against a wide range of influenza viruses. Current seasonal influenza vaccines provide strain-specific protection and are less effective against mismatched strains. The rapid antigenic drift and shift in influenza viruses resulted in time-consuming surveillance and uncertainty in the vaccine protection efficacy. Most recent universal influenza vaccine studies target the conserved antigen domains of the viral surface glycoproteins and internal proteins to provide broader protection. Following the development of advanced vaccine technologies, several innovative strategies and vaccine platforms are being explored to generate robust cross-protective immunity. This review provides the latest progress in the development of universal influenza vaccines. [ABSTRACT FROM AUTHOR]

Recent efforts have been directed toward the development of universal influenza vaccines inducing broadly neutralizing antibodies to conserved antigenic supersites of Hemagglutinin (HA). Although several studies raise the importance of glycosylation in HA antigen design, whether this theory can be widely confirmed remains unclear; which influenza HA with an altered glycosylation profile could impact the amplitude and focus of the host immune response. Here, we evaluated the characteristics and efficacy of deglycosylated modified HA proteins, including monoglycosylated HA (HAmg), unglycosylated HA (HAug), and fully glycosylated HA (HAfg), without treatment with H3N2 Wisconsin/67/2005. Our results showed that HAug could induce a cross-strain protective immune response in mice against both H3N2 and H7N9 subtypes with better antibody-dependent cellular cytotoxicity (ADCC) than the HAmg- and HAfg-immunized groups, which suggested that highly conserved epitopes that were masked by surface glycosylation may be exposed and thus promote the induction of broad antibodies that recognize the hidden epitopes. This strategy may also supplement the direction of deglycosylated modified HA for universal influenza vaccines. [ABSTRACT FROM AUTHOR]

Antigen-specific lung-resident memory T cells (TRMs) constitute the first line of defense that mediates rapid protection against respiratory pathogens and inspires novel vaccine designs against infectious pandemic threats, yet effective means of inducing TRMs, particularly via non-viral vectors, remain challenging. Here, we demonstrate safe and potent induction of lung-resident TRMs using a biodegradable polymeric nanoshell that co-encapsulates antigenic peptides and TLR9 agonist CpG-oligodeoxynucleotide (CpG-ODN) in a virus-mimicking structure. Through subcutaneous priming and intranasal boosting, the combinatorial nanoshell vaccine elicits prominent lung-resident CD4+ and CD8+ T cells that surprisingly show better durability than live viral infections. In particular, nanoshells containing CpG-ODN and a pair of conserved class I and II major histocompatibility complex-restricted influenza nucleoprotein-derived antigenic peptides are demonstrated to induce near-sterilizing immunity against lethal infections with influenza A viruses of different strains and subtypes in mice, resulting in rapid elimination of replicating viruses. We further examine the pulmonary transport dynamic and optimal composition of the nanoshell vaccine conducive for robust TRM induction as well as the benefit of subcutaneous priming on TRM replenishment. The study presents a practical vaccination strategy for inducing protective TRM-mediated immunity, offering a compelling platform and critical insights in the ongoing quest toward a broadly protective vaccine against universal influenza as well as other respiratory pathogens.

Introduction. Influenza is a socially significant infection that causes profound damage to populational health and national economy annually. Preventive vaccination is the most effective means to manage influenza and its complications. Diverse influenza vaccines exist, but their common drawback is the narrow specificity, the need for annual renewal of the strain composition, not always satisfactory immunogenicity and effectiveness. In this regard, close attention is paid to developing universal influenza vaccines aimed to induce cross-reactive immune-related cues against most conserved parts of viral proteins. Antibodies against neuraminidase (NA) are able to provide heterosubtypic protection, which is important due to potential threat posed by influenza viruses differed in hemagglutinin and neuraminidase sequence in comparison to currently circulating viruses. The present study is aimed to search for new and analysis of earlier predicted NA linear B-cell epitopes conserved among all influenza A virus subtypes. Results. Eight conserved linear B-cell epitopes were identified around the active site of neuraminidase, three of which (MNPNQKIITIGS, ILRTQESEC, and DNWKGSNRP) were synthesized de novo, conjugated with bovine serum albumin to be next used for mouse immunization. IgG antibodies were detected by ELISA in the sera of immunized mice. Antibodies were found to specifically bind to various influenza A viruses containing NA subtypes N1, N2, N3, and N9. Immunization with NA peptides did not protect mice from substantial body weight loss after infection with lethal H1N1 influenza virus. However, all immunized mice survived during the observation period, whereas in the control group the survival rate was as low as 28.6%. Analyzing lung viral load in the mice infected with the H1N1 virus revealed no differences in virus titers on either day 4 or 8 post-infection. Nevertheless, the protective effect lacked after the mice were challenged with lethal H7N9 influenza virus: Mortality rate, body weight loss, and lung virus titers were comparable in immunized and control mice. Conclusions. The data obtained evidenced about serum cross-reactive anti-NA antibodies induced by immunization with NA peptides, as well as protective efficacy against infection caused by H1N1 virus, but not H7N9 virus. Such results hold promise and indicate that NA linear B-cell epitopes can be used for designing epitope-directed influenza vaccines, but a deeper and more comprehensive study on the specificity of conserved NA epitopes, as well as optimization of immunization schemes for achieving higher protective efficacy are required.

Summary: Infection and vaccination repeatedly expose individuals to antigens that are conserved between influenza virus subtypes. Nevertheless, antibodies recognizing variable influenza epitopes greatly outnumber antibodies reactive against conserved epitopes. Elucidating factors contributing to the paucity of broadly reactive influenza antibodies remains a major obstacle for developing a universal influenza vaccine. Here, we report that inducing broadly reactive influenza antibodies increases autoreactive antibodies in humans and mice and exacerbates disease in four distinct models of autoimmune disease. Importantly, transferring broadly reactive influenza antibodies augments disease in the presence of inflammation or autoimmune susceptibility. Further, broadly reactive influenza antibodies spontaneously arise in mice with defects in B cell tolerance. Together, these data suggest that self-tolerance mechanisms limit the prevalence of broadly reactive influenza antibodies, which can exacerbate disease in the context of additional risk factors.

Every influenza season, uptake of the flu vaccine falls short of the Healthy People 2020 goal of at least 70% of adults being vaccinated. Mixed methods research finds multiple factors associated with this phenomenon including misconceptions about the vaccine, skepticism about an annual vaccine, concerns about efficacy and safety, lack of knowledge, perceived risk, among others. The national goal to develop, test and produce an effective universal influenza vaccine requires a significant scientific and financial investment in research. However, there is no true investment in the social and behavioral science research necessary to ensure that once a universal vaccine is available, the public will take that new vaccine. This article highlights some qualitative and quantitative research results to provide some understanding of the challenges to increasing vaccine uptake. We also identify research questions necessary to ensure adoption of new universal vaccines.

Neuraminidase (NA) is an important surface protein on influenza virions, playing an essential role in the viral life cycle and being a key target of the immune system. Despite the importance of NA-based immunity, current vaccines are focused on the hemagglutinin (HA) protein as the target for protective antibodies, and the amount of NA is not standardized in virion-based vaccines. Antibodies targeting NA are predominantly protective, reducing infection severity and viral shedding. Recently, NA-specific monoclonal antibodies have been characterized, and their target epitopes have been identified. This review summarizes the characteristics of NA, NA-specific antibodies, the mechanism of NA inhibition, and the recent efforts towards developing NA-based and NA-incorporating influenza vaccines.

Background: Broadly protective, long-lasting universal influenza vaccines are under development in response to low-moderate seasonal vaccine effectiveness, frequent genetic changes in circulating viruses and extended turnaround for vaccine manufacture. Because a long-lasting vaccine might be less effective than a seasonal vaccine that has been matched to current circulating strains, the public health impact of its introduction should be evaluated. Methods: A modified agent-based model (ABM) examined multi-year effects of a universal vaccine among 18 to 49-year-olds, given in Year 1 only. The proportion of vaccinated 18 to 49-year-olds who received universal vaccine was varied from 0% to 100%. Model parameters were drawn from US databases and the medical literature. Outcomes were 4-year cumulative and annual influenza cases as well as annual cases averted/100,000 population for 3 age groups, 0–17 years, 18–49 years and 50+ years. Results: In Year 1 when universal vaccine was given to 50% or 100% of all vaccinated 18 to 49-year-olds, more influenza cases occurred, compared to no universal vaccine, but fewer cases occurred in Years 2–4 as overall protection increased. Cumulative averted cases over 4 years in 18 to 49-year-olds were 892/100,000 and 1,687/100,000 population for the 50% and 100% universal vaccine for 18 to 49-year-olds scenarios, respectively, with additional benefits to children and older adults through indirect effects. Conclusions: In ABM, the universal vaccine with a conservative VE estimate given once to 18 to 49-year-olds reduced influenza cases among all age groups in Years 2–4 following its introduction. Reduced influenza burden may occur sooner if VE of universal vaccines exceeds that assumed in these models.

Background: The development of a universal influenza virus vaccine, to protect against both seasonal and pandemic influenza A viruses, is a long-standing public health goal. The conserved stalk domain of haemagglutinin (HA) is a promising vaccine target. However, the stalk is immunosubdominant. As such, innovative approaches are required to elicit robust immunity against this domain. In a previously reported observer-blind, randomised placebo-controlled phase I trial (NCT03300050), immunisation regimens using chimeric HA (cHA)-based immunogens formulated as inactivated influenza vaccines (IIV) -/+ AS03 adjuvant, or live attenuated influenza vaccines (LAIV), elicited durable HA stalk-specific antibodies with broad reactivity. In this study, we sought to determine if these vaccines could also boost T cell responses against HA stalk, and nucleoprotein (NP)., Methods: We measured interferon-γ (IFN-γ) responses by Enzyme-Linked ImmunoSpot (ELISpot) assay at baseline, seven days post-prime, pre-boost and seven days post-boost following heterologous prime:boost regimens of LAIV and/or adjuvanted/unadjuvanted IIV-cHA vaccines., Findings: Our findings demonstrate that immunisation with adjuvanted cHA-based IIVs boost HA stalk-specific and NP-specific T cell responses in humans. To date, it has been unclear if HA stalk-specific T cells can be boosted in humans by HA-stalk focused universal vaccines. Therefore, our study will provide valuable insights for the design of future studies to determine the precise role of HA stalk-specific T cells in broad protection., Interpretation: Considering that cHA-based vaccines also elicit stalk-specific antibodies, these data support the further clinical advancement of cHA-based universal influenza vaccine candidates., Funding: This study was funded in part by the Bill and Melinda Gates Foundation (BMGF)., Competing Interests: Declaration of interests The Icahn School of Medicine at Mount Sinai (ISMMS) has filed patent applications regarding universal influenza virus vaccines naming AGC, PP, RN and FK as inventors. AGC, PP and FK have also received royalties and research support for their laboratories from GSK in the past and are currently receiving research support from Dynavax for development of influenza virus vaccines. FK has consulting agreements with Pfizer, GSK, Third Rock Ventures and Avimex. The AG-S. laboratory has also received research support from Pfizer, Senhwa Biosciences, Kenall Manufacturing, Blade Therapeutics, Avimex, Johnson & Johnson, 7Hills Pharma, Pharmamar, ImmunityBio, Accurius, Nanocomposix, Hexamer, N-fold LLC, Model Medicines, Atea Pharma, Applied Biological Laboratories and Merck, outside of the reported work. A.G.-S. has consulting agreements for the following companies: Esperovax, Farmak, Applied Biological Laboratories, Pharmamar, 7Hills Pharma, Avimex, Paratus, Synairgen, Accurius, Pfizer and Nanocomposix outside of the reported work. A.G.-S has consulting agreements for the following companies involving cash and/or stock: Castlevax, Amovir, Vaxalto, Pagoda, Contrafect, CureLab Oncology, CureLab Veterinary and Vivaldi Biosciences outside of the reported work. A.G.-S. has been an invited speaker in meeting events organised by Seqirus, Janssen, Abbott and AstraZeneca. JTG is an employee of Argenx US. RN is an employee and shareholder of Moderna. DIB serves on the Data Safety Monitoring Board and Advisory Board for Moderna. AN is an employee of GSK and has vested stocks in GSK. EBW has received funding support from Pfizer, Moderna, Sequiris, Najit Technologies Inc, Leidos Biomedical and Clinetic for the conduct of clinical trials and clinical research. EBW has served as an advisor to Vaxcyte, a consultant to ILiAD biotechnologies and a data safety monitoring board member for Shionogi., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Several candidates of universal influenza vaccine (UIV) have entered phase III clinical trials, which are expected to improve the willingness and coverage of the population substantially. The impact of UIV on the seasonal influenza epidemic in low influenza vaccination coverage regions like China remains unclear. We proposed a new compartmental model involving the transmission of different influenza subtypes to evaluate the effects of UIV. We calibrated the model by weekly surveillance data of influenza in Xi’an City, Shaanxi Province, China, during 2010/11–2018/19 influenza seasons. We calculated the percentage of averted infections under 2-month (September to October) and 6-month (September to the next February) vaccination patterns with varied UIV effectiveness and coverage in each influenza season, compared with no UIV scenario. A total of 195 766 influenza-like illness (ILI) cases were reported during the nine influenza seasons (2010/11–2018/19), of which the highest ILI cases were among age group 0–4 (59.60%) years old, followed by 5–14 (25.22%), 25–59 (8.19%), 15–24 (3.75%) and ⩾60 (3.37%) years old. The influenza-positive rate for all age groups among ILI cases was 17.51%, which is highest among 5–14 (23.75%) age group and followed by 25–59 (16.44%), 15–24 (16.42%), 0–4 (14.66%) and ⩾60 (13.98%) age groups, respectively. Our model showed that UIV might greatly avert influenza infections irrespective of subtypes in each influenza season. For example, in the 2018/19 influenza season, 2-month vaccination pattern with low UIV effectiveness (50%) and coverage (10%), and high UIV effectiveness (75%) and coverage (30%) could avert 41.6% (95% CI 27.8–55.4%) and 83.4% (80.9–85.9%) of influenza infections, respectively; 6-month vaccination pattern with low and high UIV effectiveness and coverage could avert 32.0% (15.9–48.2%) and 74.2% (69.7–78.7%) of influenza infections, respectively. It would need 11.4% (7.9–15.0%) of coverage to reduce half of the influenza infections for 2-month vaccination pattern with low UIV effectiveness and 8.5% (5.0–11.2%) of coverage with high UIV effectiveness, while it would need 15.5% (8.9–20.7%) of coverage for 6-month vaccination pattern with low UIV effectiveness and 11.2% (6.5–15.0%) of coverage with high UIV effectiveness. We conclude that UIV could significantly reduce the influenza infections even for low UIV effectiveness and coverage. The 2-month vaccination pattern could avert more influenza infections than the 6-month vaccination pattern irrespective of influenza subtype and UIV effectiveness and coverage. [ABSTRACT FROM AUTHOR]

The licensed seasonal influenza vaccines predominantly induce neutralizing antibodies against immunodominant hypervariable epitopes of viral surface proteins, with limited protection against antigenically distant influenza viruses. Strategies have been developed to improve vaccines' performance in terms of broadly reactive and long-lasting immune response induction. We have summarized the advancements in the development of cross-protective influenza vaccines and discussed the challenges in evaluating them in preclinical and clinical trials. Here, the literature regarding the current stage of development of universal influenza vaccine candidates was reviewed Although various strategies aim to redirect adaptive immune responses from variable immunodominant to immunosubdominant antigens, more conserved epitopes are being investigated. Approaches that improve antibody responses to conserved B cell epitopes have increased the protective efficacy of vaccines within a subtype or phylogenetic group of influenza viruses. Vaccines that elicit significant levels of T cells recognizing highly conserved viral epitopes possess a high cross-protective potential and may cover most circulating influenza viruses. However, the development of T cell-based universal influenza vaccines is challenging owing to the diversity of MHCs in the population, unpredictable degree of immunodominance, lack of adequate animal models, and difficulty in establishing T cell immunity in humans. cHA: chimeric HA; HBc: hepatitis B virus core protein; HA: hemagglutinin; HLA: human leucocyte antigen; IIV: inactivated influenza vaccine; KLH: keyhole limpet hemocyanin; LAH: long alpha helix; LAIV: live attenuated influenza vaccine; M2e: extracellular domain of matrix 2 protein; MHC: major histocompatibility complex; mRNA: messenger ribonucleic acid; NA: neuraminidase; NS1: non-structural protein 1; qNIV: quadrivalent nanoparticle influenza vaccine; TRM: tissue-resident memory T cells; VE: vaccine effectiveness; VLP: virus-like particles; VSV: vesicular stomatitis virus [ABSTRACT FROM AUTHOR]

Recent efforts have been directed toward the development of universal influenza vaccines inducing broadly neutralizing antibodies to conserved antigenic supersites of Hemagglutinin (HA). Although several studies raise the importance of glycosylation in HA antigen design, whether this theory can be widely confirmed remains unclear; which influenza HA with an altered glycosylation profile could impact the amplitude and focus of the host immune response. Here, we evaluated the characteristics and efficacy of deglycosylated modified HA proteins, including monoglycosylated HA (HAmg), unglycosylated HA (HAug), and fully glycosylated HA (HAfg), without treatment with H3N2 Wisconsin/67/2005. Our results showed that HAug could induce a cross-strain protective immune response in mice against both H3N2 and H7N9 subtypes with better antibody-dependent cellular cytotoxicity (ADCC) than the HAmg- and HAfg-immunized groups, which suggested that highly conserved epitopes that were masked by surface glycosylation may be exposed and thus promote the induction of broad antibodies that recognize the hidden epitopes. This strategy may also supplement the direction of deglycosylated modified HA for universal influenza vaccines.

[Display omitted] • Universal influenza vaccine providing long-term protection : • Antigens: Conserved influenza A virus proteins NP, M2, or influenza B virus NP. • Mucosal administration, single dose. • Both humoral and cellular immunity persist for at least a year. • Protection effective against diverse challenge viruses persists for at least a year. • Public health benefits : • Use off-the-shelf when matched vaccines are not available. • Reduce illness, death during unexpected outbreaks and pandemics. Current influenza vaccines rely on inducing antibody responses to the rapidly evolving hemagglutinin (HA) and neuraminidase (NA) proteins, and thus need to be strain-matched. However, predictions of strains that will circulate are imperfect, and manufacturing of new vaccines based on them takes months. As an alternative, universal influenza vaccines target highly conserved antigens. In proof of concept studies of universal vaccine candidates in animal models challenge is generally conducted only a short time after vaccination, but protective immunity lasting far longer is important for the intended public health impact. We address the challenge of providing long-term protection. We demonstrate here broad, powerful, and long-lasting immune protection for a promising universal vaccine candidate. A single intranasal dose of recombinant adenoviruses (rAd) expressing influenza A nucleoprotein (A/NP) and matrix 2 (M2) was used. Extending our previous studies of this type of vaccine, we show that antibody and T-cell responses persist for over a year without boosting, and that protection against challenge persists a year after vaccination and remains broad, covering both group 1 and 2 influenza A viruses. In addition, we extend the work to influenza B. Immunization with influenza B nucleoprotein (B/NP)-rAd also gives immune responses that last a year without boosting and protect against challenge with influenza B viruses of mismatched HA lineages. Despite host immunity to adenoviral antigens, effective readministration is possible a year after primary vaccination, as shown by successful immunization to a transgene product the animals had not seen before. Protection against challenge with divergent and highly pathogenic A/H7N9 virus was weaker but was enhanced by a second dose of vaccine. Thus, this mucosal vaccination to conserved influenza antigens confers very long-lasting immune protection in animals against a broad range of influenza A and B viruses. [ABSTRACT FROM AUTHOR]

Current influenza vaccines, live attenuated or inactivated, do not protect against antigenically novel influenza A viruses (IAVs) of pandemic potential, which has driven interest in the development of universal influenza vaccines. Universal influenza vaccine candidates targeting highly conserved antigens of IAV nucleoprotein (NP) are promising as vaccines that induce T cell immunity, but concerns have been raised about the safety of inducing robust CD8 T cell responses in the lungs. Using a mouse model, we systematically evaluated effects of recombinant adenovirus vectors (rAd) expressing IAV NP (A/NP-rAd) or influenza B virus (IBV) NP (B/NP-rAd) on pulmonary inflammation and function after vaccination and following live IAV challenge. After A/NP-rAd or B/NP-rAd vaccination, female mice exhibited robust systemic and pulmonary vaccine-specific B cell and T cell responses and experienced no morbidity (e.g., body mass loss). Both in vivo pulmonary function testing and lung histopathology scoring revealed minimal adverse effects of intranasal rAd vaccination compared with unvaccinated mice. After IAV challenge, A/NP-rAd-vaccinated mice experienced significantly less morbidity, had lower pulmonary virus titers, and developed less pulmonary inflammation than unvaccinated or B/ NP-rAd-vaccinated mice. Based on analysis of pulmonary physiology using detailed testing not previously applied to the question of T cell damage, mice protected by vaccination also had better lung function than controls. Results provide evidence that, in this model, adenoviral universal influenza vaccine does not damage pulmonary tissue. In addition, adaptive immunity, in particular, T cell immunity in the lungs, does not cause damage when restimulated but instead mitigates pulmonary damage following IAV infection. [ABSTRACT FROM AUTHOR]

Abstract The influenza A virus was isolated for the first time in 1931, and the first attempts to develop a vaccine against the virus began soon afterwards. In addition to causing seasonal epidemics, influenza viruses can cause pandemics at random intervals, which are very hard to predict. Vaccination is the most effective way of preventing the spread of influenza infection. However, seasonal vaccination is ineffective against pandemic influenza viruses because of antigenic differences, and it takes approximately six months from isolation of a new virus to develop an effective vaccine. One of the possible ways to fight the emergence of pandemics may be by using a new type of vaccine, with a long and broad spectrum of action. The extracellular domain of the M2 protein (M2e) of influenza A virus is a conservative region, and an attractive target for a universal influenza vaccine. This review gives a historical overview of the study of M2 protein, and summarizes the latest developments in the preparation of M2e-based universal influenza vaccines.

ABSTRACTCurrent influenza vaccines provide hemagglutinin strain-specific protection, but rarely provide cross-protection against divergent strains. It is, therefore, particularly important to develop a universal vaccine against conserved proteins or conserved regions of the virus. In this study, we used N-terminal extracellular region of the influenza virus M2 protein (M2e) as the target antigen and constructed two optimized M2e DNA vaccines (p-tPA-p3M2e and p-p3M2e) with increased antigenic epitope density and enhanced antigen secretion. Both vaccines induced high M2e-specific humoral and cellular immune responses in the vaccinated mice. These two vaccines also conferred protection against a lethal infection of homo-subtypic H1N1 virus, with p-tPA-p3M2e being the most effective. In addition, p-tPA-p3M2e also showed cross-protection against different subtypes of the influenza virus (H9N2, H6N6, and H10N8) at varying rates (80%, 40%, and 20%, respectively). After passive immunization, M2e DNA vaccine-induced antibodies in the sera provided complete protection against homologous virus challenge. An analysis of the mechanism underlying this immunization-mediated protection indicates that M2e-specific IgG and T-cell immune responses may play critical roles in the prevention of infection and viral clearance. Taken together, our results indicate that this optimized M2e DNA vaccine is a promising candidate for the development of a universal, broad-spectrum influenza virus vaccine.

Influenza viruses are responsible for millions of cases globally and significantly threaten public health. Since pandemic and zoonotic influenza viruses have emerged in the last 20 years and some of the viruses have resulted in high mortality in humans, a universal influenza vaccine is needed to provide comprehensive protection against a wide range of influenza viruses. Current seasonal influenza vaccines provide strain-specific protection and are less effective against mismatched strains. The rapid antigenic drift and shift in influenza viruses resulted in time-consuming surveillance and uncertainty in the vaccine protection efficacy. Most recent universal influenza vaccine studies target the conserved antigen domains of the viral surface glycoproteins and internal proteins to provide broader protection. Following the development of advanced vaccine technologies, several innovative strategies and vaccine platforms are being explored to generate robust cross-protective immunity. This review provides the latest progress in the development of universal influenza vaccines.

Introduction: The current seasonal influenza vaccine confers only limited protection due to waning antibodies or the antigenic shift and drift of major influenza surface antigens. A universal influenza vaccine which induces broad cross-protection against divergent influenza viruses with a comparable or better efficacy to seasonal influenza vaccines against matched strains will negate the need for an annual update of vaccine strains and protect against possible influenza pandemics. Areas covered: In this review, we summarize the recent progress in nanoparticle-based universal influenza vaccine development. We compared the most potent nanoparticle categories, focusing on how they encapsulate conserved influenza epitopes, stimulate the innate and adaptive immune systems, exhibit antigen depot effect, extend the period for antigen-processing and presentation, and exert an intrinsic adjuvant effect on inducing robust immune responses. Expert commentary: The development of an effective universal influenza vaccine is an urgent task. Traditional influenza vaccine approaches are not sufficient for preventing recurrent epidemics or occasional pandemics. Nanoparticles are compatible with different immunogens and immune stimulators and can overcome the intrinsically low immunogenicity of conserved influenza virus antigens. We foresee that an affordable universal influenza vaccine will be available within ten years by integrating nanoparticles with other targeted delivery and controlled release technology.

Abstract The current seasonal inactivated influenza vaccine protects only against a narrow range of virus strains as it triggers a dominant antibody response toward the hypervariable hemagglutinin (HA) head region. The discovery of rare broadly protective antibodies against conserved regions in influenza virus proteins has propelled research on distinct antigens and delivery methods to efficiently induce broad immunity toward drifted or shifted virus strains. Here, we report that adeno‐associated virus (AAV) vectors expressing influenza virus HA or chimeric HA protected mice against homologous and heterologous virus challenges. Unexpectedly, immunization even with wild‐type HA induced antibodies recognizing the HA‐stalk and activating FcγR‐dependent responses indicating that AAV‐vectored expression balances HA head‐ and HA stalk‐specific humoral responses. Immunization with AAV‐HA partially protected also ferrets against a harsh virus challenge. Results from this study provide a rationale for further clinical development of AAV vectors as influenza vaccine platform, which could benefit from their approved use in human gene therapy.

Influenza virus is a respiratory pathogen that can cause disease in humans, with symptoms ranging from mild to life-threatening. The vast majority of influenza virus infections in humans are observed during seasonal epidemics and occasional pandemics. Given the substantial public health burden associated with influenza virus infection, yearly vaccination is recommended for protection against seasonal influenza viruses. Despite vigilant surveillance for new variants and careful selection of seasonal vaccine strains, the efficacy of seasonal vaccines can vary widely from year to year. This often results in lowered protection within the population, regardless of vaccination status. In order to broaden the protection afforded by seasonal influenza vaccines, the National Institute of Allergy and Infectious Diseases (NIAID) has deemed the development of a universal influenza virus vaccine to be a priority in influenza virus vaccine research. This universal vaccine would provide protection against all influenza virus strains, eliminating the need for the yearly reformulations of seasonal influenza vaccines. In addition to universal influenza vaccine efforts, substantial progress has been made in developing novel influenza virus therapeutics that utilize broadly neutralizing antibodies to provide protection against influenza virus infection and to mitigate disease outcomes during infection. In this review, we discuss various approaches toward the goal of improving influenza virus vaccine efficacy through a universal influenza virus vaccine. We also address the novel methods of discovery and utilization of broadly neutralizing antibodies to improve influenza disease outcomes.

The current seasonal inactivated influenza vaccine protects only against a narrow range of virus strains as it triggers a dominant antibody response toward the hypervariable hemagglutinin (HA) head region. The discovery of rare broadly protective antibodies against conserved regions in influenza virus proteins has propelled research on distinct antigens and delivery methods to efficiently induce broad immunity toward drifted or shifted virus strains. Here, we report that adeno‐associated virus (AAV) vectors expressing influenza virus HA or chimeric HA protected mice against homologous and heterologous virus challenges. Unexpectedly, immunization even with wild‐type HA induced antibodies recognizing the HA‐stalk and activating FcγR‐dependent responses indicating that AAV‐vectored expression balances HA head‐ and HA stalk‐specific humoral responses. Immunization with AAV‐HA partially protected also ferrets against a harsh virus challenge. Results from this study provide a rationale for further clinical development of AAV vectors as influenza vaccine platform, which could benefit from their approved use in human gene therapy. Synopsis: The study shows that immunization with adeno‐associated virus vectors protects against divergent lethal influenza A virus infections. Protection correlated with induction of antibodies targeting the head and stalk regions of the viral protein HA, and activating FcγR‐dependent responses. Adeno‐associated virus (AAV) vectors expressing viral antigens were studied for the induction of immune responses protecting against challenge infection with influenza A viruses.Immunization of mice with AAV‐vectored HA constructs elicited broadly reactive antibodies recognizing the HA‐head and ‐stalk regions, respectively, and inducing Fcγ receptor‐dependent responses.Immunized mice were protected against lethal homologous or heterologous viral challenges.Intranasal immunization with AAV‐HA elicited protective responses towards a viral challenge also in ferrets. [ABSTRACT FROM AUTHOR]

Animal models that can recapitulate the human immune system are essential for the preclinical development of safe and efficacious vaccines. Development and optimization of representative animal models are key components of the NIAID strategic plan for the development of a universal influenza vaccine. To gain insight into the current landscape of animal model usage in influenza vaccine development, NIAID convened a workshop in Rockville, Maryland that brought together experts from academia, industry and government. Panelists discussed the benefits and limitations of the field's most widely-used animal models, identified currently available and critically needed resources and reagents, and suggested areas for improvement based on inadequacies of existing models. Although appropriately-selected animal models can be useful for evaluating safety, mechanism-of-action, and superiority over existing vaccines, workshop participants concluded that multiple animal models will likely be required to sufficiently test all aspects of a novel vaccine candidate. Refinements are necessary for all current model systems, for example, to better represent special human populations, and will be facilitated by the development and broader availability of new reagents. NIAID continues to support progress towards increasing the predictive value of animal models. [ABSTRACT FROM AUTHOR]

Influenza virus is a respiratory pathogen that can cause disease in humans, with symptoms ranging from mild to life-threatening. The vast majority of influenza virus infections in humans are observed during seasonal epidemics and occasional pandemics. Given the substantial public health burden associated with influenza virus infection, yearly vaccination is recommended for protection against seasonal influenza viruses. Despite vigilant surveillance for new variants and careful selection of seasonal vaccine strains, the efficacy of seasonal vaccines can vary widely from year to year. This often results in lowered protection within the population, regardless of vaccination status. In order to broaden the protection afforded by seasonal influenza vaccines, the National Institute of Allergy and Infectious Diseases (NIAID) has deemed the development of a universal influenza virus vaccine to be a priority in influenza virus vaccine research. This universal vaccine would provide protection against all influenza virus strains, eliminating the need for the yearly reformulations of seasonal influenza vaccines. In addition to universal influenza vaccine efforts, substantial progress has been made in developing novel influenza virus therapeutics that utilize broadly neutralizing antibodies to provide protection against influenza virus infection and to mitigate disease outcomes during infection. In this review, we discuss various approaches toward the goal of improving influenza virus vaccine efficacy through a universal influenza virus vaccine. We also address the novel methods of discovery and utilization of broadly neutralizing antibodies to improve influenza disease outcomes. [ABSTRACT FROM AUTHOR]

Introduction: Annual vaccination is one of the most efficient and cost-effective strategies to prevent and control influenza epidemics. Most of the currently available influenza vaccines are strong inducers of antibody responses against viral surface proteins, hemagglutinin (HA) and neuraminidase (NA), but are poor inducers of cell-mediated immune responses against conserved internal proteins. Moreover, due to the high variability of viral surface proteins because of antigenic drift or antigenic shift, many of the currently licensed vaccines confer little or no protection against drift or shift variants. Areas covered: Next generation influenza vaccines that can induce humoral immune responses to receptor-binding epitopes as well as broadly neutralizing conserved epitopes, and cell-mediated immune responses against highly conserved internal proteins would be effective against variant viruses as well as a novel pandemic influenza until circulating strain-specific vaccines become available. Here we discuss vaccine approaches that have the potential to provide broad spectrum protection against influenza viruses. Expert commentary: Based on current progress in defining cross-protective influenza immunity, it seems that the development of a universal influenza vaccine is feasible. It would revolutionize the strategy for influenza pandemic preparedness, and significantly impact the shelf-life and protection efficacy of seasonal influenza vaccines.

Identification of a universal influenza vaccine candidate has remained a global challenge for both humans and animals. This study describes an approach that uses consensus sequence building to generate chimeric HAs (cHAs): two resultant H1 HA-based chimeras comprising of conserved sequences (within several areas spanning the head and stalk regions) of H1 and H5 or H9 HAs. These cHAs expressed in Drosophila cells (S2) were used to immunize mice. All immunized mice were protected from an infectious H1 virus challenge. Seroconverted mice sera to the H1 cHAs inhibited both the challenge virus and an H5 virus isolate by haemagglutination inhibition (HI) assay. These findings further emphasize that cHAs induce cross-reactive antibodies against conserved areas of both head and stalk regions of the seasonal influenza A (H1N1) pdm09 virus’ HA and holds potential for further development of a universal influenza vaccine.

The development of an influenza vaccine with broad protection and durability remains an attractive idea due to the high mutation rate of the influenza virus. An extracellular domain of Matrix 2 protein (M2e) is among the most attractive target for the universal influenza vaccine owing to its high conservancy rate. Here, we generated two recombinant live attenuated influenza vaccine (LAIV) candidates encoding four M2e epitopes representing consensus sequences of human, avian and swine influenza viruses, and studied them in a preclinical ferret model. Both LAIV+4M2e viruses induced higher levels of M2e-specific antibodies compared to the control LAIV strain, with the LAIV/HA+4M2e candidate being significantly more immunogenic than the LAIV/NS+4M2e counterpart. A high-dose heterosubtypic influenza virus challenge revealed the highest degree of protection after immunization with LAIV/HA+4M2e strain, followed by the NS-modified LAIV and the classical LAIV virus. Furthermore, only the immune sera from the LAIV/HA+4M2e-immunized ferrets protected mice from a panel of lethal influenza viruses encoding M genes of various origins. These data suggest that the improved cross-protection of the LAIV/HA+4M2e universal influenza vaccine candidate was mediated by the M2e-targeted antibodies. Taking into account the safety profile and improved cross-protective potential, the LAIV/HA+4M2e vaccine warrants its further evaluation in a phase I clinical trial.

Introduction: Influenza A virus causes unpredictable epidemics and pandemics by creating antigenic variations. With the appearance of each new strain, rapid emergency countermeasures are taken against this new strain. Hence, designing an applicable and cross protective strategy to counter this virus is of great importance. To achieve this, choosing conserved antigenic regions in influenza virus proteins for making a universal vaccine is one of the best options. M2 channel in influenza virus membrane has a conserved sequence in ectodomain region called M2e. This region is the same between the majority of influenza A virus strains. But this peptide region is not a good stimulant for the immune system due to its short length. Immunoadjuvant property of Salmonella Typhimurium flagellin (FliC) has been previously shown to arouse immunity in the mucosal region. A combination of M2e and FliC was used in a construct in this study. Methods: To increase the possibility of immunugencity of this construct, in silico predictions of this fusion peptide construct were performed first. Three repeats of M2e gene and FliC sequence were cloned into pET28 vector and then were sub-cloned to pHT43. Finally, the construct was transformed into Bacillus subtilis by electroporation. After IPTG induction, the total cell protein and the supernatant protein were analyzed via protein analyses methods. Results: Based on in silico immunogenicity results, the designed recombinant peptide was deemed suitable to be used as a universal influenza vaccine candidate. The validity of pHT43.3M2e.FliC construct was confirmed by restriction map analysis. Western-blotting confirmed the presence of recombinant protein. Conclusion: The fusion peptide produced in this research, is the first step in designing a universal influenza vaccine which needs to be assessed in animal models alongside proper control groups in future studies.