Intranasal inactivated influenza vaccines for the prevention of seasonal influenza epidemics

Multilayer Adjuvanted Influenza Protein Nanoparticles Improve Intranasal Delivery and Antigen-Specific Immunity

Intranasal vaccination is a desired route for protection against influenza viruses by mucosal and systemic immunity. However, the nasal mucosa impedes the intranasal delivery of vaccines. Here, we formulated layer-by-layer (LBL) influenza vaccine nanoparticles for effective intranasal delivery by coating them with alternating mucoadhesive cationic chitosan and muco-inert anionic CpG adjuvants. The nanoparticle cores were formed by desolvating influenza M2e antigen and coating it with hemagglutinin (HA) antigen via biotin-streptavidin conjugation. LBL modification promoted nasal delivery and interaction with the resident immune cells. Intranasal administration with LBL nanoparticles significantly improved cellular and humoral immune responses against HA and M2e including high IgA titers, a hallmark of potent mucosal immunity and persistence of immune responses. Distinct trends for antigen-specific immune responses were observed for different routes of vaccination. The enhanced immune responses conferred mice protection against the influenza challenge and prominently reduced viral titers, demonstrating the effectiveness of intranasal LBL vaccine nanoparticles.

Respiratory delivered vaccines: Current status and perspectives in rational formulation design

The respiratory tract is susceptible to various infections and can be affected by many serious diseases. Vaccination is one of the most promising ways that prevent infectious diseases and treatment of some diseases such as malignancy. Direct delivery of vaccines to the respiratory tract could mimic the natural process of infection and shorten the delivery path, therefore unique mucosal immunity at the first line might be induced and the efficiency of delivery can be high. Despite considerable attempts at the development of respiratory vaccines, the rational formulation design still warrants attention, i.e., how the formulation composition, particle properties, formulation type (liquid or solid), and devices would influence the immune outcome. This article reviews the recent advances in the formulation design and development of respiratory vaccines. The focus is on the state of the art of delivering antigenic compounds through the respiratory tract, overcoming the pulmonary bio-barriers, enhancing delivery efficiencies of respiratory vaccines as well as maintaining the stability of vaccines during storage and use. The choice of devices and the influence of deposition sites on vaccine efficiencies were also reviewed.

Intranasal Immunization with Nasal Immuno-Inducible Sequence-Fused Antigens Elicits Antigen-Specific Antibody Production

Intranasal immunization is one of the most effective methods for eliciting lung mucosal immunity. Multiple intranasal immunization with bacterial polypeptide, termed as a modified PnxIIIA (MP3) protein, is known to elicit production of a specific antibody in mice. In this study, a nasal immuno-inducible sequence (NAIS) was designed to remove the antigenicity of the MP3 protein that can induce mucosal immunity by intranasal immunization, and was examined to induce antigen-specific antibodies against the fused bacterial thioredoxin (Trx) as a model antigen. A NAIS was modified and generated to remove a large number of predicted MHC (Major Histocompatibility Complex)-I and MHC-II binding sites in parent protein PnxIIIA and MP3 in order to reduce the number of antigen epitope sites. For comparative analysis, full-length NAIS291, NAIS230, and NAIS61 fused with Trx and 6× His tag and Trx-fused 6× His tag were used as antigen variants for the intranasal immunization of BALB/c mice every two weeks for three immunizations. Anti-Trx antibody titers in serum and bronchoalveolar lavage fluid (BALF) IgA obtained from NAIS291-fused Trx-immunized mice were significantly higher than those from Trx-immunized mice. The antibody titers against NAIS alone were significantly lower than those against Trx alone in the serum IgG, serum IgA, and BALF IgA. These results indicate that the NAIS contributes to antibody elicitation of the fused antigen as an immunostimulant in intranasal vaccination vaccines. The results indicate that the NAIS and target inactivated antigen fusions can be applied to intranasal vaccine systems.

Pharmacokinetics of intranasal drugs, still a missed opportunity?

The intranasal (IN) route of administration is important for topical drugs and drugs intended to act systemically. More recently, direct nose-to-brain input was considered to bypass the blood-brain barrier.Processes related to IN absorption and nose-to-brain distribution are complex and depend, sometimes in contrasting ways, on chemico-physical and structural parameters of the compounds, and on formulation options.Due to the intricacies of these processes and despite the large number of articles published on many different IN compounds, it appears that absorption after IN dosing is not yet fully understood. In particular, at variance of the understanding and modelling approaches that are available for predicting the pharmacokinetics (PK) following oral administration of xenobiotics, it appears that there is not a similar understanding of the chemico-physical and structural determinants influencing drug absorption and disposition of compounds after IN administration, which represents a missed opportunity for this research field. This is even more true regarding the understanding of the direct nose-to-brain input. Due to this, IN administrations may represent an interesting and open research field for scientists aiming to develop PK property predictions tools, mechanistic PK models describing rate and extent of IN absorption, and translational tools to anticipate the clinical PK following IN dosing based on in vitro and in vivo non clinical experiments.This review intends to provide: i) some basic knowledge related to the physiology of PK after IN dosing, ii) a non-exhaustive list of preclinical and clinical examples related to compounds explored for the potential nose-to-blood and nose-to-brain passage, and iii) the identification of some areas requiring improvements, the understanding of which may facilitate the development of IN drug candidates.

A Glycolipid α-GalCer Derivative, 7DW8-5 as a Novel Mucosal Adjuvant for the Split Inactivated Influenza Vaccine

Influenza virus infects the host and transmits through the respiratory tract (i.e., the mouth and nose); therefore, the development of intranasal influenza vaccines that mimic the natural infection, coupled with an efficient mucosal adjuvant, is an attractive alternative to current parenteral vaccines. However, with the withdrawal of cholera toxin and Escherichia coli heat-labile endotoxin from clinical use due to side effects, there are no approved adjuvants for intranasal vaccines. Therefore, safe and effective mucosal adjuvants are urgently needed. Previously, we reported that one derivative of α-Galactosylceramide (α-GalCer), 7DW8-5, could enhance the protective efficacy of split influenza vaccine by injection administration. However, the mucosal adjuvanticity of 7DW8-5 is still unclear. In this study, we found that 7DW8-5 promotes the production of secret IgA antibodies and IgG antibodies and enhances the protective efficacy of the split influenza vaccine by intranasal administration. Furthermore, co-administration of 7DW8-5 with the split influenza vaccine significantly reduces the virus shedding in the upper and lower respiratory tract after lethal challenge. Our results demonstrate that 7DW8-5 is a novel mucosal adjuvant for the split influenza vaccine.

mRNA-based therapeutics: powerful and versatile tools to combat diseases

The therapeutic use of messenger RNA (mRNA) has fueled great hope to combat a wide range of incurable diseases. Recent rapid advances in biotechnology and molecular medicine have enabled the production of almost any functional protein/peptide in the human body by introducing mRNA as a vaccine or therapeutic agent. This represents a rising precision medicine field with great promise for preventing and treating many intractable or genetic diseases. In addition, in vitro transcribed mRNA has achieved programmed production, which is more effective, faster in design and production, as well as more flexible and cost-effective than conventional approaches that may offer. Based on these extraordinary advantages, mRNA vaccines have the characteristics of the swiftest response to large-scale outbreaks of infectious diseases, such as the currently devastating pandemic COVID-19. It has always been the scientists’ desire to improve the stability, immunogenicity, translation efficiency, and delivery system to achieve efficient and safe delivery of mRNA. Excitingly, these scientific dreams have gradually been realized with the rapid, amazing achievements of molecular biology, RNA technology, vaccinology, and nanotechnology. In this review, we comprehensively describe mRNA-based therapeutics, including their principles, manufacture, application, effects, and shortcomings. We also highlight the importance of mRNA optimization and delivery systems in successful mRNA therapeutics and discuss the key challenges and opportunities in developing these tools into powerful and versatile tools to combat many genetic, infectious, cancer, and other refractory diseases.

Impact of Refutational Two-Sided Messages on Attitudes Toward Novel Vaccines Against Emerging Infectious Diseases During the COVID-19 Pandemic

Two-sided messages that include two perspectives (i.e., risks and benefits) are more effective than one-sided messages that convey only one perspective (usually only the benefits). Refutational two-sided messages are effective for communicating risks regarding vaccines. To examine the effectiveness of refutational two-sided messages in risk communication regarding novel vaccines against emerging infectious diseases, we conducted the randomized controlled study based on a 3 × 3 × 2 mixed design (Intervention 1: vaccines against subcutaneous influenza, “novel severe infectious disease,” or intranasal influenza; intervention 2: one-sided, non-refutational two-sided, or refutational two-sided messages; two questionnaires) using a Japanese online panel. Participants completed questionnaires before and after receiving an attack message (negative information). We evaluated the impact of attack messages on the willingness to be vaccinated, and the anticipated regret of inaction (ARI). Among 1,184 participants, there was a significant difference in the willingness to be vaccinated among the message groups (p < 0.01). After receiving the attack message, willingness to be vaccinated decreased in the one-sided message group and increased in the non-refutational two-sided and refutational two-sided message groups. Additionally, ARI in the refutational two-sided message groups was significantly higher than in the one-sided groups (p = 0.03). In conclusion, two-sided messages are more effective than one-sided messages in terms of willingness to be vaccinated. Furthermore, the high ARI in the refutational two-sided message group indicated that refutational two-sided messages were more effective than one-sided messages for communicating the risks of vaccines, especially those against emerging infectious diseases.

Saliva as a useful tool for evaluating upper mucosal antibody response to influenza

Mucosal immunity plays a crucial role in controlling upper respiratory infections, including influenza. We established a quantitative ELISA to measure the amount of influenza virus-specific salivery IgA (sIgA) and salivary IgG (sIgG) antibodies using a standard antibody broadly reactive to the influenza A virus. We then analyzed saliva and serum samples from seven individuals infected with the A(H1N1)pdm09 influenza virus during the 2019-2020 flu seasons. We detected an early (6-10 days post-infection) increase of sIgA in five of the seven samples and a later (3-5 weeks) increase of sIgG in six of the seven saliva samples. Although the conventional parenteral influenza vaccine did not induce IgA production in saliva, vaccinated individuals with a history of influenza infection had higher basal levels of sIgA than those without a history. Interestingly, we observed sIgA and sIgG in an asymptomatic individual who had close contact with two influenza cases. Both early mucosal sIgA secretion and late systemically induced sIgG in the mucosal surface may protect against virus infection. Despite the small sample size, our results indicate that the saliva test system can be useful for analyzing upper mucosal immunity in influenza.

A Live Olfactory Mouse Cytomegalovirus Vaccine, Attenuated for Systemic Spread, Protects against Superinfection

Vaccination against the betaherpesvirus, human cytomegalovirus (HCMV) is a public health goal. However, HCMV has proved difficult to vaccinate against. Vaccination against single HCMV determinants has not worked, suggesting that immunity to a wider antigenic profile may be required. Live attenuated vaccines provide the best prospects for protection, but the question remains as to how to balance vaccine virulence with safety. Animal models of HCMV infection provide insights into identifying targets for virus attenuation and understanding how host immunity blocks natural, mucosal infection. Here, we evaluated the vaccine potential of a mouse cytomegalovirus (MCMV) vaccine deleted of a viral G protein-coupled receptor (GPCR), designated M33, that renders it attenuated for systemic spread. A single noninvasive olfactory ΔM33 MCMV vaccine replicated locally, but as a result of the loss of the M33 GPCR, it failed to spread systemically and was attenuated for latent infection. Vaccination did not prevent host entry of a superinfecting MCMV but spread from the mucosa was blocked. This approach to vaccine design may provide a viable alternative for a safe and effective betaherpesvirus vaccine. IMPORTANCE Human cytomegalovirus (HCMV) is the most common cause of congenital infection for which a vaccine is not yet available. Subunit vaccine candidates have failed to achieve licensure. A live HCMV vaccine may prove more efficacious, but it faces safety hurdles which include its propensity to persist and to establish latency. Understanding how pathogens infect guide rational vaccine design. However, HCMV infections are asymptomatic and thus difficult to capture. Animal models of experimental infection provide insight. Here, we investigated the vaccine potential of a mouse cytomegalovirus (MCMV) attenuated for systemic spread and latency. We used olfactory vaccination and virus challenge to mimic its natural acquisition. We provide proof of concept that a single olfactory MCMV that is deficient in systemic spread can protect against wild-type MCMV superinfection and dissemination. This approach of deleting functional counterpart genes in HCMV may provide safe and effective vaccination against congenital HCMV disease.

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.

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.

Emerging Role of Mucosal Vaccine in Preventing Infection with Avian Influenza A Viruses

Avian influenza A viruses (AIVs), as a zoonotic agent, dramatically impacts public health and the poultry industry. Although low pathogenic avian influenza virus (LPAIV) incidence and mortality are relatively low, the infected hosts can act as a virus carrier and provide a resource pool for reassortant influenza viruses. At present, vaccination is the most effective way to eradicate AIVs from commercial poultry. The inactivated vaccines can only stimulate humoral immunity, rather than cellular and mucosal immune responses, while failing to effectively inhibit the replication and spread of AIVs in the flock. In recent years, significant progresses have been made in the understanding of the mechanisms underlying the vaccine antigen activities at the mucosal surfaces and the development of safe and efficacious mucosal vaccines that mimic the natural infection route and cut off the AIVs infection route. Here, we discussed the current status and advancement on mucosal immunity, the means of establishing mucosal immunity, and finally a perspective for design of AIVs mucosal vaccines. Hopefully, this review will help to not only understand and predict AIVs infection characteristics in birds but also extrapolate them for distinction or applicability in mammals, including humans.

Human immune responses elicited by an intranasal inactivated H5 influenza vaccine

Intranasally administered influenza vaccines could be more effective than injected vaccines, because intranasal vaccination can induce virus-specific immunoglobulin A (IgA) antibodies in the upper respiratory tract, which is the initial site of infection. In this study, immune responses elicited by an intranasal inactivated vaccine of influenza A(H5N1) virus were evaluated in healthy individuals naive for influenza A(H5N1) virus. Three doses of intranasal inactivated whole-virion H5 influenza vaccine induced strong neutralizing nasal IgA and serum IgG antibodies. In addition, a mucoadhesive excipient, carboxy vinyl polymer, had a notable impact on the induction of nasal IgA antibody responses but not on serum IgG antibody responses. The nasal hemagglutinin (HA)-specific IgA antibody responses clearly correlated with mucosal neutralizing antibody responses, indicating that measurement of nasal HA-specific IgA titers could be used as a surrogate for the mucosal antibody response. Furthermore, increased numbers of plasma cells and vaccine antigen-specific Th cells in the peripheral blood were observed after vaccination, suggesting that peripheral blood biomarkers may also be used to evaluate the intranasal vaccine-induced immune response. However, peripheral blood immune cell responses correlated with neutralizing antibody titers in serum samples but not in nasal wash samples. Thus, analysis of the peripheral blood immune response could be a surrogate for the systemic immune response to intranasal vaccination but not for the mucosal immune response. The current study suggests the clinical potential of intranasal inactivated vaccines against influenza A(H5N1) viruses and highlights the need to develop novel means to evaluate intranasal vaccine-induced mucosal immune responses.

The human antibody response to influenza A virus infection and vaccination

The adaptive immune response to influenza virus infection is multifaceted and complex, involving antibody and cellular responses at both systemic and mucosal levels. Immune responses to natural infection with influenza virus in humans are relatively broad and long-lived, but influenza viruses can escape from these responses over time owing to their high mutation rates and antigenic flexibility. Vaccines are the best available countermeasure against infection, but vaccine effectiveness is low compared with other viral vaccines, and the induced immune response is narrow and short-lived. Furthermore, inactivated influenza virus vaccines focus on the induction of systemic IgG responses but do not effectively induce mucosal IgA responses. Here, I review the differences between natural infection and vaccination in terms of the antibody responses they induce and how these responses protect against future infection. A better understanding of how natural infection induces broad and long-lived immune responses will be key to developing next-generation influenza virus vaccines.

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

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

Mucosal Immunity against Neuraminidase Prevents Influenza B Virus Transmission in Guinea Pigs

Recently, the protective effect of anti-neuraminidase immunity has been highlighted by several studies in humans and animal models. However, so far the role that anti-neuraminidase immunity plays in inhibition of virus transmission has not been explored. In addition, neuraminidase has been ignored as an antigen for influenza virus vaccines. We show here that neuraminidase-based vaccines can inhibit the transmission of influenza virus. Therefore, neuraminidase should be considered as an antigen for improved influenza virus vaccines that not only protect individuals from disease but also inhibit further spread of the virus in the population.

Despite efforts to control influenza virus infection and transmission, influenza viruses still cause significant morbidity and mortality in the global human population each year. Most of the current vaccines target the immunodominant hemagglutinin surface glycoprotein of the virus. However, reduced severity of disease and viral shedding have also been linked to antibodies targeting the second viral surface glycoprotein, the neuraminidase. Importantly, antineuraminidase immunity was shown to be relatively broad, in contrast to vaccine-induced antibodies to the hemagglutinin head domain. In this study, we assessed recombinant neuraminidase protein vaccination for its ability to prevent or limit virus transmission. We vaccinated guinea pigs either intramuscularly or intranasally with a recombinant influenza B virus neuraminidase to assess whether neuraminidase vaccination via these routes could prevent transmission of the homologous virus to a naive recipient. Guinea pigs vaccinated with neuraminidase showed reduced virus titers; however, only vaccination via the intranasal route fully prevented virus transmission to naive animals. We found high levels of antineuraminidase antibodies capable of inhibiting neuraminidase enzymatic activity in the nasal washes of intranasally vaccinated animals, which may explain the observed differences in transmission. We also determined that mucosal immunity to neuraminidase impaired the transmission efficiency of a heterologous influenza B virus, although to a lesser extent. Finally, we found that neuraminidase-vaccinated animals were still susceptible to infection via the airborne and contact transmission routes. However, significantly lower virus titers were detected in these vaccinated recipients. In summary, our data suggest that supplementing vaccine formulations with neuraminidase and vaccinating via the intranasal route may broadly prevent transmission of influenza B viruses.