Intranasal Administration of Whole Inactivated Influenza Virus Vaccine as a Promising Influenza Vaccine Candidate

Evaluation of the cross-protection of the Vero cell-derived attenuated influenza vaccines with compound adjuvant, through intranasal immunization

This study was to evaluate the sufficient safety and effect of the novel influenza vaccine program. It prepared new reassortant influenza virus, with high yield on Vero cells. According to the plaque counting, one dose LAIV was composed with 105 PFU of H1, H3, BY, and BV, respectively. Then mixed this LAIV with compound adjuvant, containing 500 μg/mL of carbopol971P and 50 μg/mL of tetanus toxin. That vaccination was called catt-flu. And it employed the GYZZ02 vaccine (commercialized freeze-dried LAIV, listed in China) as cohort analysis control. All mice received two doses of the vaccine, administered on days 0 and 14, respectively. That catt-flu program could induce more cross-protection with neutralizing antibody against heterogeneous types of influenza virus, not only based on HA but also NA protective antigen, through convenient nasal immunization, which had non-inferiority titter compared with the chicken embryo-derived GYZZ02 vaccine on safe and effect. The Vero cell-derived vaccine (LAIV) combined compound catt adjuvant (contain carbopol971P and tetanus toxin) could provide another safety and protective program of influenza vaccine by intranasal administration, as catt-flu program.

Filling two needs with one deed: a combinatory mucosal vaccine against influenza A virus and respiratory syncytial virus

Influenza A Virus (IAV) and Respiratory Syncytial Virus (RSV) are both responsible for millions of severe respiratory tract infections every year worldwide. Effective vaccines able to prevent transmission and severe disease, are important measures to reduce the burden for the global health system. Despite the strong systemic immune responses induced upon current parental immunizations, this vaccination strategy fails to promote a robust mucosal immune response. Here, we investigated the immunogenicity and efficacy of a mucosal adenoviral vector vaccine to tackle both pathogens simultaneously at their entry site. For this purpose, BALB/c mice were immunized intranasally with adenoviral vectors (Ad) encoding the influenza-derived proteins, hemagglutinin (HA) and nucleoprotein (NP), in combination with an Ad encoding for the RSV fusion (F) protein. The mucosal combinatory vaccine induced neutralizing antibodies as well as local IgA responses against both viruses. Moreover, the vaccine elicited pulmonary CD8+ and CD4+ tissue resident memory T cells (TRM) against the immunodominant epitopes of RSV-F and IAV-NP. Furthermore, the addition of Ad-TGFβ or Ad-CCL17 as mucosal adjuvant enhanced the formation of functional CD8+ TRM responses against the conserved IAV-NP. Consequently, the combinatory vaccine not only provided protection against subsequent infections with RSV, but also against heterosubtypic challenges with pH1N1 or H3N2 strains. In conclusion, we present here a potent combinatory vaccine for mucosal applications, which provides protection against two of the most relevant respiratory viruses.

An inactivated whole-virion vaccine for Enterovirus D68 adjuvanted with CpG ODN or AddaVax elicits potent protective immunity in mice

Enterovirus D68 (EV-D68), a pathogen that causes respiratory symptoms, mainly in children, has been implicated in acute flaccid myelitis, which is a poliomyelitis-like paralysis. Currently, there are no licensed vaccines or treatments for EV-D68 infections. Here, we investigated the optimal viral inactivation reagents, vaccine adjuvants, and route of vaccination in mice to optimize an inactivated whole-virion (WV) vaccine against EV-D68. We used formalin, β-propiolactone (BPL), and hydrogen peroxide as viral inactivation reagents and compared their effects on antibody responses. Use of any of these three viral inactivation reagents effectively induced neutralizing antibodies. Moreover, the antibody response induced by the BPL-inactivated WV vaccine was enhanced when adjuvanted with cytosine phosphoguanine oligodeoxynucleotide (CpG ODN) or AddaVax (MF59-like adjuvant), but not with aluminum hydroxide (alum). Consistent with the antibody response results, the protective effect of the inactivated WV vaccine against the EV-D68 challenge was enhanced when adjuvanted with CpG ODN or AddaVax, but not with alum. Further, while the intranasal inactivated WV vaccine induced EV-D68-specific IgA antibodies in the respiratory tract, it was less protective against EV-D68 challenge than the injectable vaccine. Thus, an injectable inactivated EV-D68 WV vaccine prepared with appropriate viral inactivation reagents and an optimal adjuvant is a promising EV-D68 vaccine.

Crossprotection induced by virus-like particles containing influenza dual-hemagglutinin and M2 ectodomain

Aims: To develop an effective universal vaccine against antigenically different influenza viruses. Materials & methods: We generated influenza virus-like particles (VLPs) expressing the H1 and H3 antigens with or without M2e5x. VLP-induced immune responses and crossprotection against H1N1, H3N2 or H5N1 viruses were assessed to evaluate their protective efficacy. Results: H1H3M2e5x immunization elicited higher crossreactive IgG antibodies than H1H3 VLPs. Upon challenge, both VLPs enhanced lung IgG, IgA and germinal center B-cell responses compared with control. While these VLPs conferred protection, H1H3M2e5x showed greater lung viral load reduction than H1H3 VLPs with minimal body weight loss. Conclusion: Utilizing VLPs containing dual-hemagglutinin, along with M2e5x, can be a vaccination strategy for inducing crossprotection against influenza A viruses.

SARS-CoV-2 mRNA vaccination induces an intranasal mucosal response characterized by neutralizing antibodies

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccine-induced systemic antibody profiles are well characterized; however, little is known about whether intranasal mucosal antibodies are induced or can neutralize virus in response to mRNA vaccination.

Objective

We sought to evaluate intranasal mucosal antibody production with SARS-CoV-2 mRNA vaccination.

Methods

SARS-CoV-2-specific IgG and IgA concentrations and neutralization activity from sera and nasal mucosa via nasal epithelial lining fluid (NELF) collection were measured in SARS-CoV-2 mRNA-vaccinated healthy volunteers (N = 29) by using multiplex immunoassays. Data were compared before and after vaccination, between mRNA vaccine brands, and by sex.

Results

SARS-CoV-2 mRNA vaccination induced an intranasal immune response characterized by neutralizing mucosal antibodies. IgG antibodies displayed greater Spike 1 (S1) binding specificity than did IgA in serum and nasal mucosa. Nasal antibodies displayed greater neutralization activity against the receptor-binding domain than serum. Spikevax (Moderna)-vaccinated individuals displayed greater SARS-CoV-2-specific IgG and IgA antibody concentrations than did Comirnaty (BioNTech/Pfizer)-vaccinated individuals in their serum and nasal epithelial lining fluid. Sex-dependent differences in antibody response were not observed.

Conclusion

SARS-CoV-2 mRNA vaccination induces a robust systemic and intranasal antibody production with neutralizing capacity. Spikevax vaccinations elicit a greater antibody response than does Comirnaty vaccination systemically and intranasally.

Advances in intranasal vaccine delivery: A promising non-invasive route of immunization

The importance of vaccination has been proven particularly significant the last three years, as it is revealed to be the most efficient weapon for the prevention of several infections including SARS-COV-2. Parenteral vaccination is the most applicable method of immunization, for the prevention of systematic and respiratory infections, or central nervous system disorders, involving T and B cells to a whole-body immune response. However, the mucosal vaccines, such as nasal vaccines, can additionally activate the immune cells localized on the mucosal tissue of the upper and lower respiratory tract. This dual stimulation of the immune system, along with their needle-free administration favors the development of novel nasal vaccines to produce long-lasting immunity. In recent years, the nanoparticulate systems have been extensively involved in the formulation of nasal vaccines as polymeric, polysaccharide and lipid ones, as well as in the form of proteosomes, lipopeptides and virosomes. Advanced delivery nanosystems have been designed and evaluated as carriers or adjuvants for nasal vaccination. To this end, several nanoparticulate vaccines are undergone clinical trials as promising candidates for nasal immunization, while nasal vaccines against influenza type A and B and hepatitis B have been approved by health authorities. This comprehensive literature review aims to summarize the critical aspects of these formulations and highlight their potential for the future establishment of nasal vaccination. Both preclinical (in vitro and in vivo) and clinical studies are incorporated, summarized, and critically discussed, as well as the limitations of nasal immunization.

A Comparison of Etiology, Pathogenesis, Vaccinal and Antiviral Drug Development between Influenza and COVID-19

Influenza virus and coronavirus, two kinds of pathogens that exist widely in nature, are common emerging pathogens that cause respiratory tract infections in humans. In December 2019, a novel coronavirus SARS-CoV-2 emerged, causing a severe respiratory infection named COVID-19 in humans, and raising a global pandemic which has persisted in the world for almost three years. Influenza virus, a seasonally circulating respiratory pathogen, has caused four global pandemics in humans since 1918 by the emergence of novel variants. Studies have shown that there are certain similarities in transmission mode and pathogenesis between influenza and COVID-19, and vaccination and antiviral drugs are considered to have positive roles as well as several limitations in the prevention and control of both diseases. Comparative understandings would be helpful to the prevention and control of these diseases. Here, we review the study progress in the etiology, pathogenesis, vaccine and antiviral drug development for the two diseases.

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.

Emerging antiviral therapies and drugs for the treatment of influenza

INTRODUCTION

Both vaccines and antiviral drugs represent the mainstay for preventing and treating influenza. However, approved M2 ion channel inhibitors, neuraminidase inhibitors, polymerase inhibitors, and various vaccines cannot meet therapeutic needs because of viral resistance. Thus, the discovery of new targets for the virus or host and the development of more effective inhibitors are essential to protect humans from the influenza virus.

AREAS COVERED

This review summarizes the latest progress in vaccines and antiviral drug research to prevent and treat influenza, providing the foothold for developing novel antiviral inhibitors.

EXPERT OPINION

Vaccines embody the most effective approach to preventing influenza virus infection, and recombinant protein vaccines show promising prospects in developing next-generation vaccines. Compounds targeting the viral components of RNA polymerase, hemagglutinin and nucleoprotein, and the modification of trusted neuraminidase inhibitors are future research directions for anti-influenza virus drugs. In addition, some host factors affect the replication of virus in vivo, which can be used to develop antiviral drugs.

Needle-free, spirulina-produced Plasmodium falciparum circumsporozoite vaccination provides sterile protection against pre-erythrocytic malaria in mice

Antibodies against the Plasmodium falciparum circumsporozoite protein (PfCSP) can block hepatocyte infection by sporozoites and protect against malaria. Needle-free vaccination strategies are desirable, yet most PfCSP-targeted vaccines like RTS,S require needle-based administration. Here, we evaluated the edible algae, Arthrospira platensis (commonly called 'spirulina') as a malaria vaccine platform. Spirulina were genetically engineered to express virus-like particles (VLPs) consisting of the woodchuck hepatitis B core capsid protein (WHcAg) displaying a (NANP)₁₅ PfCSP antigen on its surface. PfCSP-spirulina administered to mice intranasally followed by oral PfCSP-spirulina boosters resulted in a strong, systemic anti-PfCSP immune response that was protective against subcutaneous challenge with PfCSP-expressing P. yoelii. Unlike male mice, female mice did not require Montanide adjuvant to reach high antibody titers or protection. The successful use of spirulina as a vaccine delivery system warrants further development of spirulina-based vaccines as a useful tool in addressing malaria and other diseases of global health importance.

Neutralizing antibodies and cellular immune response after two doses of inactivated SARS-CoV-2 vaccine in China

BACKGROUND

As of 2022, inactivated SARS-CoV-2 vaccines had been used in more than 91 countries. However, limited information was available on the immune responses of the inactivated SARS-CoV-2 vaccine in the real world.

METHODS

We used SARS-CoV-2 pseudovirus to determine neutralizing antibodies (NAbs) to wild type and several global variants and utilized enzyme-linked immunosorbent assay to investigate IFN-γ-secreting T-cell responses to SARS-CoV-2 among 240 vaccinees after two doses of inactivated vaccine in China.

RESULTS

A majority of vaccinees (>90%) have developed robust NAbs and T-cell responses to SARS-CoV-2 in the first two months after the second dose. After six months, only 37.0% and 44.0% of vaccinees had NAbs and T-cell immunity to SARS-CoV-2, respectively. Immune serum retained most of neutralizing potency against Alpha and Iota variants, but significantly lost neutralizing potency against Beta, Kappa, Delta, and Omicron variants. Only 40% vaccine-sera remained low-level neutralization activities to Omicron, with a 14.7-fold decrease compared to wild type.

CONCLUSION

The inactivated SARS-CoV-2 vaccine stimulated robust NAbs and T-cell immune responses in the first two months after the second dose but the immune effect drops rapidly, which highlights that a third or more dose boost shot may be required to boost immunity against SARS-CoV-2.

Examining the Interactions of GalahadTM Compound with Viruses to Develop a Novel Inactivated Influenza A Virus Vaccine

Galahad™ is a proanthocyanidin complexed with polysaccharides that inactivates viruses and indicates potential for an innovative approach to making protective vaccines. The polysaccharide portion of Galahad™ consists mainly of arabinan and arabinogalactan. In a seven-day toxicity study in rats, it was not toxic even when tested undiluted. Galahad™ inactivated a wide range of DNA and RNA viruses including adenoviruses, corona viruses such as SARS-CoV-2, and influenza viruses. Electron microscopy studies showed that exposure to Galahad™ caused extensive clumping of virions followed by lack of detection of virions after longer periods of exposure. Based on the viral inactivation data, the hypotheses tested is that Galahad™ inactivation of virus can be used to formulate a protective inactivated virus vaccine. To evaluate this hypothesis, infectious influenza A virus (H5N1, Duck/MN/1525/81) with a titer of 10^5.7 CCID₅₀/0.1 ml was exposed for 10 min to Galahad™. This treatment caused the infectious virus titer to be reduced to below detectable limits. The Galahad™ -inactivated influenza preparation without adjuvant or preservative was given to BALB/c mice using a variety of routes of administration and dosing regimens. The most protective route of administration and dosing regimen was when mice were given the vaccine twice intranasally, the second dose coming 14 days after the primary vaccine dose. All the mice receiving this vaccine regimen survived the virus challenge while only 20% of the mice receiving placebo survived. This suggests that a Galahad™-inactivated influenza virus vaccine can elicit a protective immune response even without the use of an adjuvant. This technology should be investigated further for its potential to make effective human vaccines.

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Discovery of novel virus-inactivating agent: polysaccharide/catechin (Galahad™).

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Non-toxic: inactivates/lowers titers in 25 viruses, including Avian H5N1, COVID-19.

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Agent used to make whole virus vaccine; tested in 400 animal mouse model.

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Galahad™-inactivated vaccine 100% successful intranasally vs. lethal H5N1 challenge.

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Platform offers possible benefits—in time, cost, & mass distribution.

Strategies to Develop a Mucosa-Targeting Vaccine against Emerging Infectious Diseases

Numerous pathogenic microbes, including viruses, bacteria, and fungi, usually infect the host through the mucosal surfaces of the respiratory tract, gastrointestinal tract, and reproductive tract. The mucosa is well known to provide the first line of host defense against pathogen entry by physical, chemical, biological, and immunological barriers, and therefore, mucosa-targeting vaccination is emerging as a promising strategy for conferring superior protection. However, there are still many challenges to be solved to develop an effective mucosal vaccine, such as poor adhesion to the mucosal surface, insufficient uptake to break through the mucus, and the difficulty in avoiding strong degradation through the gastrointestinal tract. Recently, increasing efforts to overcome these issues have been made, and we herein summarize the latest findings on these strategies to develop mucosa-targeting vaccines, including a novel needle-free mucosa-targeting route, the development of mucosa-targeting vectors, the administration of mucosal adjuvants, encapsulating vaccines into nanoparticle formulations, and antigen design to conjugate with mucosa-targeting ligands. Our work will highlight the importance of further developing mucosal vaccine technology to combat the frequent outbreaks of infectious diseases.

Potentiating Lung Mucosal Immunity Through Intranasal Vaccination

Yearly administration of influenza vaccines is our best available tool for controlling influenza virus spread. However, both practical and immunological factors sometimes result in sub-optimal vaccine efficacy. The call for improved, or even universal, influenza vaccines within the field has led to development of pre-clinical and clinical vaccine candidates that aim to address limitations of current influenza vaccine approaches. Here, we consider the route of immunization as a critical factor in eliciting tissue resident memory (Trm) populations that are not a target of current licensed intramuscular vaccines. Intranasal vaccination has the potential to boost tissue resident B and T cell populations that reside within specific niches of the upper and lower respiratory tract. Within these niches, Trm cells are poised to respond rapidly to pathogen re-encounter by nature of their anatomic localization and their ability to rapidly deliver anti-pathogen effector functions. Unique features of mucosal immunity in the upper and lower respiratory tracts suggest that antigen localized to these regions is required for the elicitation of protective B and T cell immunity at these sites and will need to be considered as an important attribute of a rationally designed intranasal vaccine. Finally, we discuss outstanding questions and areas of future inquiry in the field of lung mucosal immunity.

Intranasal immunization with chitosan microparticles enhances lack-dna vaccine protection and induces specific long-lasting immunity against visceral leishmaniasis

Development of a protective vaccine against Leishmania depends on antigen formulation and adjuvants that induce specific immunity and long-lasting immune responses. We previously demonstrated that BALB/c mice intranasally vaccinated with a plasmid DNA encoding the p36/LACK leishmanial antigen (LACK-DNA) develop a protective immunity for up to 3 months after vaccination, which was linked with the systemic expression of vaccine mRNA in peripheral organs. In this study, LACK-DNA vaccine was associated with biocompatible chitosan microparticles cross-linked with glyceraldehyde (CMC) to boost the long-lasting immunity against the late L. infantum challenge. Infection at 7 days, 3 or 6 months after vaccination resulted in significantly lower parasite loads when compared with non-vaccinated controls. Besides, LACK-DNA-chitosan vaccinated mice showed long-time protection observed after the late time point challenge. The achieved protection was correlated with an enhanced spleen cell responsiveness to parasite antigens, marked by increased proliferation and IFN-γ as well as decreased IL-10 production. Moreover, we found diminished systemic levels of TNF-α that was compatible with the better health condition observed in LACK-DNA/CMC vaccinated-infected mice. Together, our data indicate the feasibility of chitosan microparticles as a delivery system tool to extend the protective immunity conferred by LACK-DNA vaccine, which may be explored in vaccine formulations against Leishmania parasite infections.

The potential of neuraminidase as an antigen for nasal vaccines to increase cross-protection against influenza viruses

Despite the availability of vaccines that efficiently reduce the severity of clinical symptoms, influenza viruses still cause substantial morbidity and mortality worldwide. In this regard, nasal influenza vaccines-because they induce virus-specific IgA-may be more effective than traditional parenteral formulations in preventing infection of the upper respiratory tract. In addition, the neuraminidase (NA) of influenza virus has shown promise as a vaccine antigen to confer broad cross-protection, in contrast to hemagglutinin (HA), the target of most current vaccines, which undergoes frequent antigenic changes leading to vaccine ineffectiveness against mismatched heterologous strains. However, the usefulness of NA as an antigen for nasal vaccines is unclear. Here, we compared NA and HA as antigens for nasal vaccines in mice. Intranasal immunization with recombinant NA (rNA) plus adjuvant protected mice against not only homologous but also heterologous virus challenge in the upper respiratory tract, whereas intranasal immunization with rHA failed to protect against heterologous challenge. In addition, intranasal immunization with rNA, but not rHA, conferred cross-protection even in the absence of adjuvant in virus infection-experienced mice; this strong cross-protection was due to the broader binding capacity of NA-specific antibodies to heterologous virus. Furthermore, the NA-specific IgA in the upper respiratory tract that was induced through rNA intranasal immunization recognized more epitopes than did the NA-specific IgG and IgA in plasma, again increasing cross-protection. Together, our findings suggest the potential of NA as an antigen for nasal vaccines to provide broad cross-protection against both homologous and heterologous influenza viruses. IMPORTANCE Because mismatch between vaccine strains and epidemic strains cannot always be avoided, the development of influenza vaccines that induce broad cross-protection against antigenically mismatched heterologous strains is needed. Although the importance of NA-specific antibodies to cross-protection in humans and experimental animals is becoming clear, the potential of NA as an antigen for providing cross-protection through nasal vaccines is unknown. We show here that intranasal immunization with NA confers broad cross-protection in the upper respiratory tract, where virus transmission is initiated, by inducing NA-specific IgA that recognizes a wide range of epitopes. These data shed new light on NA-based nasal vaccines as powerful anti-influenza tools that confer broad cross-protection.

Influenza Vaccination for the Prevention of Cardiovascular Disease in the Americas: Consensus document of the Inter-American Society of Cardiology and the Word Heart Federation

Background

Cardiovascular mortality is decreasing but remains the leading cause of death world-wide. Respiratory infections such as influenza significantly contribute to morbidity and mortality in patients with cardiovascular disease. Despite of proven benefits, influenza vaccination is not fully implemented, especially in Latin America.

Objective

The aim was to develop a regional consensus with recommendations regarding influenza vaccination and cardiovascular disease.

Methods

A multidisciplinary team composed by experts in the management and prevention of cardiovascular disease from the Americas, convened by the Inter-American Society of Cardiology (IASC) and the World Heart Federation (WHF), participated in the process and the formulation of statements. The modified RAND/UCLA methodology was used. This document was supported by a grant from the WHF.

Results

An extensive literature search was divided into seven questions, and a total of 23 conclusions and 29 recommendations were achieved. There was no disagreement among experts in the conclusions or recommendations.

Conclusions

There is a strong correlation between influenza and cardiovascular events. Influenza vaccination is not only safe and a proven strategy to reduce cardiovascular events, but it is also cost saving. We found several barriers for its global implementation and potential strategies to overcome them.

Induction of mucosal immunity by pulmonary administration of a cell-targeting nanoparticle

We previously found that a nanoparticle constructed with an antigen, benzalkonium chloride (BK) and γ-polyglutamic acid (γ-PGA) showed high Th1 and Th2-type immune induction after subcutaneous administration. For prophylaxis of respiratory infections, however, mucosal immunity should be induced. In this study, we investigated the effect of pulmonary administration of a nanoparticle comprising ovalbumin (OVA) as a model antigen, BK, and γ-PGA on induction of mucosal immunity in the lungs and serum. The complex was strongly taken up by RAW264.7 and DC2.4cells. After pulmonary administration, lung retention was longer for the OVA/BK/γ-PGA complex than for OVA alone. OVA-specific serum immunoglobulin (Ig)G was highly induced by the complex. High IgG and IgA levels were also induced in the bronchoalveolar lavage fluid, and in vivo toxicities were not observed. In conclusion, we effectively and safely induced mucosal immunity by pulmonary administration of an OVA/BK/γ-PGA complex.

Advances in Development and Application of Influenza Vaccines

Influenza A virus is one of the most important zoonotic pathogens that can cause severe symptoms and has the potential to cause high number of deaths and great economic loss. Vaccination is still the best option to prevent influenza virus infection. Different types of influenza vaccines, including live attenuated virus vaccines, inactivated whole virus vaccines, virosome vaccines, split-virion vaccines and subunit vaccines have been developed. However, they have several limitations, such as the relatively high manufacturing cost and long production time, moderate efficacy of some of the vaccines in certain populations, and lack of cross-reactivity. These are some of the problems that need to be solved. Here, we summarized recent advances in the development and application of different types of influenza vaccines, including the recent development of viral vectored influenza vaccines. We also described the construction of other vaccines that are based on recombinant influenza viruses as viral vectors. Information provided in this review article might lead to the development of safe and highly effective novel influenza vaccines.

Nasal-subcutaneous prime-boost regimen for inactivated whole-virus influenza vaccine efficiently protects mice against both upper and lower respiratory tract infections

Although influenza vaccines are effective for reducing viral transmission and the severity of clinical symptoms, influenza viruses still induce considerable morbidity and mortality worldwide. Seasonal influenza viruses infect the upper respiratory tract initially but then often induce severe pulmonary complications in the lower respiratory tract. Therefore, influenza vaccines that prevent viral infection at both the upper and lower respiratory tracts are highly anticipated. Here, we examined whether using different vaccination routes for priming and boosting achieved protection in both regions of the respiratory tract. To this end, we used inactivated whole-virion influenza vaccines to immunize mice either subcutaneously or intranasally for both priming and boosting. Regardless of the route used for boosting, the levels of virus-specific IgG in plasma were higher in mice primed subcutaneously than those in control mice, which received PBS only. In addition, intranasal priming followed by subcutaneous boosting induced higher levels of virus-specific IgG in plasma than those in control mice. The levels of virus-specific nasal IgA were higher in mice that were primed intranasally than in control mice or in mice primed subcutaneously. Furthermore, intranasal priming but not subcutaneous priming provided protection against viral challenge in the upper respiratory tract. In addition, when coupled with subcutaneous boosting, both subcutaneous and intranasal priming protected against viral challenge in the lower respiratory tract. These results indicate that intranasal priming followed by subcutaneous boosting induces both virus-specific IgG in plasma and IgA in nasal washes and protects against virus challenge in both the upper and lower respiratory tracts. Our results will help to develop novel vaccines against influenza viruses and other respiratory viruses.

An influenza HA stalk reactive polymeric IgA antibody exhibits anti-viral function regulated by binary interaction between HA and the antibody

IgA antibodies, which are secreted onto the mucosal surface as secretory IgA antibodies (SIgAs), play an important role in preventing influenza virus infection. A recent study reported that anti-hemagglutinin (HA) head-targeting antibodies increase anti-viral functions such as hemagglutination inhibition (HI) and virus neutralization (NT), in addition to HA binding activity (reactivity) via IgA polymerization. However, the functional properties of anti-viral IgA antibodies with mechanisms of action distinct from those of anti-HA head-targeting antibodies remain elusive. Here, we characterized the functional properties of IgG, monomeric IgA, and polymeric IgA anti-HA stalk-binding clones F11 and FI6, and B12 (a low affinity anti-HA stalk clone), as well as Fab-deficient (ΔFab) IgA antibodies. We found that IgA polymerization impacts the functional properties of anti-HA stalk antibodies. Unlike anti-HA head antibodies, the anti-viral functions of anti-HA stalk antibodies were not simply enhanced by IgA polymerization. The data suggest that two modes of binding (Fab paratope-mediated binding to the HA stalk, and IgA Fc glycan-mediated binding to the HA receptor binding site (RBS)) occur during interaction between anti-stalk HA IgA antibodies and HA. In situations where Fab paratope-mediated binding to the HA stalk exceeded IgA Fc glycan-mediated binding to HA RBS, IgA polymerization increased anti-viral functions. By contrast, when IgA Fc glycan-mediated binding to the HA RBS was dominant, anti-viral activity will fall upon IgA polymerization. In summary, the results suggest that coordination between these two independent binding modules determines whether IgA polymerization has a negative or positive effect on the anti-viral functions of anti-HA stalk IgA antibodies.

Vaccine effect of recombinant single-chain hemagglutinin protein as an antigen

Vaccination is one of the most effective interventions for preventing the spread of influenza viruses at the population level. Currently most influenza vaccines are produced by using embryonated chicken eggs, but alternative methods that achieve more rapid large-scale production are highly desirable for vaccines against both pandemic and seasonal influenza viruses. The use of recombinant hemagglutinin (HA), a key virus surface protein, as an antigen is an attractive candidate alternative approach, because of the potential for high protein yields and the ease of cloning new antigenic variants. Although fusion of HA with trimerization domains is needed to stabilize the trimeric structure and enhance the immunogenicity of the recombinant HA protein, whether the trimerization domains are immunogenic must be considered. Here, we generated recombinant multimeric HA without trimerization domains by using a short peptide linker, termed a single-chain HA (scHA), and evaluated scHAs as potential antigens for generating vaccines against influenza virus. Using mammalian cells, we succeeded in making three types of recombinant scHAs—two dimeric scHAs and a trimeric scHA. After immunization with aluminium salts in mice, one of the dimeric scHAs induced the greatest HA-specific IgG response among the scHAs and protected against virus challenge as strongly as the typically used trimeric HA containing a trimerization domain. We did not observe IgGs specific for the short peptide linker in mice immunized with the dimeric scHA, although IgGs specific for the trimerization domain occurred in mice immunized with the trimeric HA containing that domain. Furthermore, changing to another adjuvant did not diminish the utility of the dimeric scHA. These results suggest the potential usefulness of dimeric scHA as a vaccine antigen. We believe that single-chain antigens may represent new alternatives for production of recombinant antigen–based vaccines.

Vaccines to Prevent Infectious Diseases in the Older Population: Immunological Challenges and Future Perspectives

Infectious diseases are a major cause for morbidity and mortality in the older population. Demographic changes will lead to increasing numbers of older persons over the next decades. Prevention of infections becomes increasingly important to ensure healthy aging for the individual, and to alleviate the socio-economic burden for societies. Undoubtedly, vaccines are the most efficient health care measure to prevent infections. Age-associated changes of the immune system are responsible for decreased immunogenicity and clinical efficacy of most currently used vaccines in older age. Efficacy of standard influenza vaccines is only 30-50% in the older population. Several approaches, such as higher antigen dose, use of MF59 as adjuvant and intradermal administration have been implemented in order to specifically target the aged immune system. The use of a 23-valent polysaccharide vaccine against Streptococcus pneumoniae has been amended by a 13-valent conjugated pneumococcal vaccine originally developed for young children several years ago to overcome at least some of the limitations of the T cell-independent polysaccharide antigens, but still is only approximately 50% protective against pneumonia. A live-attenuated vaccine against herpes zoster, which has been available for several years, demonstrated efficacy of 51% against herpes zoster and 67% against post-herpetic neuralgia. Protection was lower in the very old and decreased several years after vaccination. Recently, a recombinant vaccine containing the viral glycoprotein gE and the novel adjuvant AS01B has been licensed. Phase III studies demonstrated efficacy against herpes zoster of approx. 90% even in the oldest age groups after administration of two doses and many countries now recommend the preferential use of this vaccine. There are still many infectious diseases causing substantial morbidity in the older population, for which no vaccines are available so far. Extensive research is ongoing to develop vaccines against novel targets with several vaccine candidates already being clinically tested, which have the potential to substantially reduce health care costs and to save many lives. In addition to the development of novel and improved vaccines, which specifically target the aged immune system, it is also important to improve uptake of the existing vaccines in order to protect the vulnerable, older population.

Current and New Approaches for Mucosal Vaccine Delivery

Mucosal surfaces are the interface between the host’s internal milieu and the external environment, and they have dual functions, serving as physical barriers to foreign antigens and as accepting sites for vital materials. Mucosal vaccines are more favored to prevent mucosal infections from the portal of entry. Although mucosal vaccination has many advantages, licensed mucosal vaccines are scarce. The most widely studied mucosal routes are oral and intranasal. Licensed oral and intranasal vaccines are composed mostly of whole cell killed or live attenuated microorganisms serving as both delivery systems and built-in adjuvants. Future mucosal vaccines should be made with more purified antigen components, which will be relatively less immunogenic. To induce robust protective immune responses against well-purified vaccine antigens, an effective mucosal delivery system is an essential requisite. Recent developments in biomaterials and nanotechnology have enabled many innovative mucosal vaccine trials. For oral vaccination, the vaccine delivery system should be able to stably carry antigens and adjuvants and resist harsh physicochemical conditions in the stomach and intestinal tract. Besides many nano/microcarrier tools generated by using natural and chemical materials, the development of oral vaccine delivery systems using food materials should be more robustly researched to expand vaccine coverage of gastrointestinal infections in developing countries. For intranasal vaccination, the vaccine delivery system should survive the very active mucociliary clearance mechanisms and prove safety because of the anatomical location of nasal cavity separated by a thin barrier. Future mucosal vaccine carriers, regardless of administration routes, should have certain common characteristics. They should maintain stability in given environments, be mucoadhesive, and have the ability to target specific tissues and cells.

Nasal priming with immunobiotic lactobacilli improves the adaptive immune response against influenza virus

The nasal priming with Lactobacillus rhamnosus CRL1505 modulates the respiratory antiviral innate immune response and improves protection against influenza virus (IFV) challenge in mice. However, the potential beneficial effect of the CRL1505 strain on the adaptive immune response triggered by IFV infection or vaccination was not evaluated before. In this work, we demonstrated that nasally administered L. rhamnosus CRL1505 is able to improve both the humoral and cellular adaptive immune responses induced by IFV infection or vaccination. Higher levels of IFV-specific IgA and IgG as well as IFN-γ were found in the serum and the respiratory tract of CRL1505-treated mice after IFV challenge. Lactobacilli treated mice also showed reduced concentrations of IL-17 and improved levels of IL-10 during IFV infection. The differential balance of inflammatory and regulatory cytokines induced by L. rhamnosus CRL1505 contributed to the protection against IFV by favoring an effective effector immune response without inducing inflammatory-mediated lung damage. The optimal immunomodulatory effect of the CRL1505 strain was achieved with viable bacteria. However, non-viable L. rhamnosus CRL1505 was also efficient in improving the adaptive immune responses generated by IFV challenges and therefore, emerged as an interesting alternative for vaccination of immunocompromised hosts. Similar to other immunomodulatory properties of lactobacilli, it was shown here that the adjuvant effect in the context of IFV vaccination was a strain dependent ability, since differences were found when L. rhamnosus CRL1505 and the immunomodulatory strain L. rhamnosus IBL027 were compared. This investigation represents a thorough exploration of the role of immunobiotic lactobacilli in improving humoral and cellular adaptive immune responses against IFV in the context of both infection and vaccination.

A double-blind, randomized controlled trial to evaluate the safety and immunogenicity of an intranasally administered trivalent inactivated influenza vaccine with the adjuvant LTh(αK): A phase II study

BACKGROUND

Intranasal influenza vaccines may provide protective efficacy by inducing both systemic antibodies and local secretory IgA. Live attenuated intranasal vaccines are not feasible for high-risk groups. A previously constructed inactivated vaccine with adjuvant revealed an association with neurological events in some studies. In this phase II trial, we aimed to evaluate the safety and immunogenicity of an intranasal influenza vaccine with a novel adjuvant, heat-labile enterotoxin (LT)-derived from E. coli (LTh(αK)).

METHODS

This study is a multicenter, randomized controlled, double-blind, phase II trial of an intranasal influenza vaccine containing 22.5 μg of the hemagglutinin (HA) antigen of three influenza strains in combination with 2 different LTh(αK) adjuvant doses (group 1: 30 μg; group 2: 45 μg) in subjects 20-70 years old. The control vaccine was 22.5 μg of influenza HA antigen alone (group 3). The vaccine was intranasally administered on days 1 and 8. Serum anti-HA antibody and nasal secretory IgA were measured, and adverse events (AEs) were recorded prevaccination and 29 (±2) days postvaccination.

RESULTS

Of 354 participants randomized in the study, 340 received two vaccine doses. AEs were mostly mild, and there was no discontinuation related to the vaccine. Only a higher frequency of diarrhea after the first dose was noted among group 2 (11.5%) than among group 3 (2.8%), and there was no significant difference after the second dose. The three groups had comparable serum anti-HA antibody immunogenicity. However, the adjuvanted vaccines induced greater mucosal IgA antibody production than the control vaccine. In a subgroup analysis, group 1 participants achieved adequate immunogenicity among both 20- to 60- and 61- to 70-year-old participants.

CONCLUSION

The intranasal influenza vaccine adjuvanted with LTh(αK) is generally safe and could provide systemic and local antibody responses. Adjuvanted vaccines were significantly more immunogenic than the nonadjuvanted control vaccine in mucosal immunity. ClinicalTrials.gov Identifier: NCT03784885.

Parenteral Vaccination With a Tuberculosis Subunit Vaccine in Presence of Retinoic Acid Provides Early but Transient Protection to M. Tuberculosis Infection

Most microbes invading through mucosal surfaces cause disease and therefore strategies to induce mucosal immune responses are strongly needed. Vitamin A metabolites, such as retinoic acid (RA), play crucial roles in programming T and B cells to home to mucosal compartments, therefore we evaluated the capacity of RA to elicit mucosal immune responses against tuberculosis (TB) after parenteral vaccination. We found that mice immunized through subcutaneous injections with the TB subunit vaccine (CAF01+H56) in presence of RA show enhanced mucosal H56-specific IgA responses and enhanced Ag-specific CD4⁺ T lymphocytes homing to the lung as compared with control mice. Immunization with CAF01+H56 in presence of RA resulted in lower bacterial loads in the lungs of mice 14 days after challenge with virulent Mycobacterium tuberculosis (Mtb) as compared to mice immunized in the absence of RA or vaccinated with BCG. Higher amounts of IFNγ and IL-17 pro-inflammatory cytokines were found in lung homogenates of mice immunized with CAF01+H56 and RA 24 h after Mtb infection. However, 6 weeks after infection the protection was comparable in vaccinated mice with or without RA even though treatment with RA during immunization is able to better contain the inflammatory response by the host. Furthermore, at later stage of the infection a higher percentage of Mtb specific CD4⁺PD1⁺ T lymphocytes were found in the lungs of mice immunized with CAF01+H56 and RA. These data show that an enhanced mucosal immune response is generated during parenteral vaccination in presence of RA. Furthermore, RA treatment contained the bacterial growth at an early stage of the infection and limited the inflammatory response in the lung at later time points.

Pam3CSK4 adjuvant given intranasally boosts anti-Leishmania immunogenicity but not protective immune responses conferred by LaAg vaccine against visceral leishmaniasis

The use of adjuvants in vaccine formulations is a well-established practice to improve immunogenicity and protective immunity against diseases. Previously, we have demonstrated the feasibility of intranasal vaccination with the antigen of killed Leishmania amazonensis promastigotes (LaAg) against experimental leishmaniasis. In this work, we sought to optimize the immunogenic effect and protective immunity against murine visceral leishmaniasis conferred by intranasal delivery of LaAg in combination with a synthetic TLR1/TLR2 agonist (Pam3CSK4). Intranasal vaccination with LaAg/PAM did not show toxicity or adverse effects, induced the increase of delayed-type hypersensitivity response and the production of inflammatory cytokines after parasite antigen recall. However, mice vaccinated with LaAg/PAM and challenged with Leishmania infantum presented significant reduction of parasite burden in both liver and spleen, similar to those vaccinated with LaAg. Although LaAg/PAM intranasal vaccination had induced higher frequencies of specific CD4⁺ and CD8⁺ T cells and increased levels of IgG2a antibody isotype in serum, both LaAg and LaAg/PAM groups presented similar levels of IL-4 and IFN-y and decreased production of IL-10 when compared to controls. Our results provide the first evidence of the feasibility of intranasal immunization with antigens of killed Leishmania in association with a TLR agonist, which may be explored for developing an effective and alternative strategy for vaccination against visceral leishmaniasis.

Could the Olfactory System Be a Target for Homeopathic Remedies as Nanomedicines?

Homeopathic remedies (HRs) contain odorant molecules such as flavonoids or terpenes and can lose their efficiency in presence of some competitive odors. Such similarities, along with extreme sensitivity of the olfactory system, widespread presence of olfactory receptors over all organic tissues (where they have metabolic roles besides perception of odors), and potential direct access to the brain through olfactory nerves (ONs) and trigeminal nerves, may suggest the olfactory system as target for HRs. Recent works highlighted that HRs exist in a dual form, that is, a still molecular form at low dilution and a nanoparticulate form at high dilution, and that remnants of source remedy persist in extremely high dilutions. From the literature, both odorants and nanoparticles (NPs) can enter the body through inhalation, digestive absorption, or through the skin, especially, NPs or viruses can directly reach the brain through axons of nerves. Assuming that HRs are recognized by olfactory receptors, their information could be transmitted to numerous tissues through receptor-ligand interaction, or to the brain by either activating the axon potential of ONs and trigeminal nerves or, in their nanoparticulate form, by translocating through axons of these nerves. Moreover, the nanoparticulate form may activate the immune system at multiple levels, induce systemic various biological responses through the pituitary axis and inflammation factors, or modulate gene expression at the cellular level. As immunity, inflammation, pituitary axis, and olfactory system are closely linked together, their permanent interaction triggered by olfactory receptors may thus ensure homeostasis.

Intranasal inactivated influenza vaccines for the prevention of seasonal influenza epidemics

INTRODUCTION

Intranasal influenza vaccines are expected to confer protection among vaccine recipients by successful induction of mucosal immune response in the upper respiratory tract. Though only live attenuated influenza virus vaccines (LAIVs) are licensed and available for intranasal use in humans today, intranasal inactivated influenza vaccines (IIVs) are currently under reconsideration as a promising intranasal influenza vaccine.

AREAS COVERED

This review addresses the history of intranasal IIV research and development, along with a summary of the studies done so far to address the mechanism of action of intranasal IIVs.

EXPERT COMMENTARY

From numerous in vitro and in vivo studies, it has been shown that intranasal IIVs can protect hosts from a broad spectrum of influenza virus strains. In-depth studies of the mucosal antibody response following intranasal IIV administration have also elucidated the detailed functions of secretory IgA (immunoglobulin A) antibodies which are responsible for the mechanism of action of intranasal vaccines. Safe and effective intranasal IIVs are expected to be an important tool to combat seasonal influenza.

Seroprevalence of Human Parainfluenza Virus Types 1-4 Among Healthy Children Under 5 Years of Age in Korea

Human parainfluenza viruses (HPIVs) are among the major causes of respiratory infections in children, worldwide, including in Korea. There are four types of HPIVs, each with different epidemiological characteristics. HPIV3 is the most frequently circulating HPIV type, while the epidemiology of HPIV4 remains unclear. The aim of this study was to investigate the age-stratified seropositivity rates of HPIV types 1-4 among children in Korea. These data will be useful to determine vaccine requirements. This study included 245 participants categorized into four age groups: 6-11 months, 1 year, 2 years, and 3-5 years. Hemagglutination inhibition (HAI) assay was used to measure the antibody titers in the serum samples of the subjects. Overall, a significantly higher seropositivity rate (68%) was observed for HPIV3 (p < 0.001), indicating the predominant circulation of this type. In the 3- to 5-year-old group, 97% of the participants displayed seropositivity for HPIV3, suggesting that most Korean children acquire HPIV3 infection by the age of 5 years. The seropositivity rate for HPIV3 increased with age (p < 0.001); a prompt rise was observed between the 6-11 months age group and the 1-year age group. The seropositivity rates of HPIV1, HPIV2, and HPIV4 were found to increase with age (p < 0.001), with a marked increase recorded after the age of 2 years. HPIV1, HPIV2, and HPIV4 tended to infect children later than HPIV3. Older children showed high antibody titer ranges for HPIV3 (p < 0.001), suggesting that children experience multiple HPIV3 infections. An increasing trend of HPIV4 seropositivity rates with age was observed and this was comparable to theHPIV1 and HPIV2 seropositivity rates, indicating that its incidence may have been underestimated. To reduce HPIV infection, the administration of a HPIV3 vaccine to children 1 year of age is likely to be the most effective option.