Induction of Local Secretory IgA and Multifunctional CD4⁺ T-helper Cells Following Intranasal Immunization with a H5N1 Whole Inactivated Influenza Virus Vaccine in BALB/c Mice

Vaccine Strategies to Elicit Mucosal Immunity

Vaccines are essential tools to prevent infection and control transmission of infectious diseases that threaten public health. Most infectious agents enter their hosts across mucosal surfaces, which make up key first lines of host defense against pathogens. Mucosal immune responses play critical roles in host immune defense to provide durable and better recall responses. Substantial attention has been focused on developing effective mucosal vaccines to elicit robust localized and systemic immune responses by administration via mucosal routes. Mucosal vaccines that elicit effective immune responses yield protection superior to parenterally delivered vaccines. Beyond their valuable immunogenicity, mucosal vaccines can be less expensive and easier to administer without a need for injection materials and more highly trained personnel. However, developing effective mucosal vaccines faces many challenges, and much effort has been directed at their development. In this article, we review the history of mucosal vaccine development and present an overview of mucosal compartment biology and the roles that mucosal immunity plays in defending against infection, knowledge that has helped inform mucosal vaccine development. We explore new progress in mucosal vaccine design and optimization and novel approaches created to improve the efficacy and safety of mucosal vaccines.

Effectiveness of VSV vectored SARS-CoV-2 spike when administered through intranasal, intramuscular or a combination of both

A critical feature of the VSV vector platform is the ability to pseudotype the virus with different glycoproteins from other viruses, thus altering cellular tropism of the recombinant virus. The route of administration is critical in triggering local and systemic immune response and protection. Most of the vaccine platforms used at the forefront are administered by intramuscular injection. However, it is not known at what level ACE2 is expressed on the surface of skeletal muscle cells, which will have a significant impact on the efficiency of a VSV-SARS-CoV-2 spike vaccine to mount a protective immune response when administered intramuscularly. In this study, we investigate the immunogenicity and efficacy of a prime-boost immunization regimen administered intranasally (IN), intramuscularly (IM), or combinations of the two. We determined that the prime-boost combinations of IM followed by IN immunization (IM + IN) or IN followed by IN immunization (IN + IN) exhibited strong spike-specific IgG, IgA and T cell response in vaccinated K18 knock-in mice. Hamsters vaccinated with two doses of VSV expressing SARS-CoV-2 spike, both delivered by IN or IM + IN, showed strong protection against SARS-CoV-2 variants of concern Alpha and Delta. This protection was also observed in aged hamsters. Our study underscores the highly crucial role immunization routes have with the VSV vector platform to elicit a strong and protective immune response.

Recombinant single-cycle influenza virus with exchangeable pseudotypes allows repeated immunization to augment anti-tumour immunity with immune checkpoint inhibitors

Virus-based tumour vaccines offer many advantages compared to other antigen-delivering systems. They generate concerted innate and adaptive immune response, and robust CD8⁺ T cell responses. We engineered a non-replicating pseudotyped influenza virus (S-FLU) to deliver the well-known cancer testis antigen, NY-ESO-1 (NY-ESO-1 S-FLU). Intranasal or intramuscular immunization of NY-ESO-1 S-FLU virus in mice elicited a strong NY-ESO-1-specific CD8⁺ T cell response in lungs and spleen that resulted in the regression of NY-ESO-1-expressing lung tumour and subcutaneous tumour, respectively. Combined administration with anti-PD-1 antibody, NY-ESO-1 S-FLU virus augmented the tumour protection by reducing the tumour metastasis. We propose that the antigen delivery through S-FLU is highly efficient in inducing antigen-specific CD8⁺ T cell response and protection against tumour development in combination with PD-1 blockade.

A Dual Adjuvant System for Intranasal Boosting of Local and Systemic Immunity for Influenza Vaccination

Systemically vaccinated individuals against COVID-19 and influenza may continue to support viral replication and shedding in the upper airways, contributing to the spread of infections. Thus, a vaccine regimen that enhances mucosal immunity in the respiratory mucosa is needed to prevent a pandemic. Intranasal/pulmonary (IN) vaccines can promote mucosal immunity by promoting IgA secretion at the infection site. Here, we demonstrate that an intramuscular (IM) priming-IN boosting regimen with an inactivated influenza A virus adjuvanted with the liposomal dual TLR4/7 adjuvant (Fos47) enhances systemic and local/mucosal immunity. The IN boosting with Fos47 (IN-Fos47) enhanced antigen-specific IgA secretion in the upper and lower respiratory tracts compared to the IM boosting with Fos47 (IM-Fos47). The secreted IgA induced by IN-Fos47 was also cross-reactive to multiple influenza virus strains. Antigen-specific tissue-resident memory T cells in the lung were increased after IN boosting with Fos47, indicating that IN-Fos47 established tissue-resident T cells. Furthermore, IN-Fos47 induced systemic cross-reactive IgG antibody titers comparable to those of IM-Fos47. Neither local nor systemic reactogenicity or adverse effects were observed after IN delivery of Fos47. Collectively, these results indicate that the IM/IN regimen with Fos47 is safe and provides both local and systemic anti-influenza immune responses.

Distinct Immunological Profiles Help in the Maintenance of Salivary Secretory IgA Production in Mild Symptoms COVID-19 Patients

Background

Relevant aspects regarding the SARS-CoV-2 pathogenesis and the systemic immune response to this infection have been reported. However, the mucosal immune response of the upper airways two months after SARS-CoV-2 infection in patients with mild/moderate symptoms is still not completely described. Therefore, we investigated the immune/inflammatory responses of the mucosa of the upper airways of mild/moderate symptom COVID-19 patients two months after the SARS-CoV-2 infection in comparison to a control group composed of non-COVID-19 healthy individuals.

Methods

A cohort of 80 volunteers (age 37.2 ± 8.2), including non-COVID-19 healthy individuals (n=24) and COVID-19 patients (n=56) who presented mild/moderate symptoms during a COVID-19 outbreak in Brazil in November and December of 2020. Saliva samples were obtained two months after the COVID-19 diagnosis to assess the levels of SIgA by ELISA and the cytokines by multiplex analysis.

Results

Salivary levels of SIgA were detected in 39 volunteers into the COVID-19 group and, unexpectedly, in 14 volunteers in the control group. Based on this observation, we distributed the volunteers of the control group into without SIgA or with SIgA sub-groups, and COVID-19 group into without SIgA or with SIgA sub-groups. Individuals with SIgA showed higher levels of IL-10, IL-17A, IFN-γ, IL-12p70, IL-13, and IFN-α than those without SIgA. In intergroup analysis, the COVID-19 groups showed higher salivary levels of IL-10, IL-13, IL-17A, and IFN-α than the control group. No statistical differences were verified in the salivary levels of IL-6 and IFN-β. Lower IL-12p70/IL-10 and IFN-γ/IL-10 ratios were found in the control group without SIgA than the control group with SIgA and the COVID-19 group with SIgA.

Conclusion

We were able to present, for the first time, that associations between distinct immunological profiles can help the mucosal immunity to maintain the salivary levels of SIgA in COVID-19 patients two months after the SARS-CoV-2 infection.

In Nasal Mucosal Secretions, Distinct IFN and IgA Responses Are Found in Severe and Mild SARS-CoV-2 Infection

Likely as in other viral respiratory diseases, SARS-CoV-2 elicit a local immune response, which includes production and releasing of both cytokines and secretory immunoglobulin (SIgA). Therefore, in this study, we investigated the levels of specific-SIgA for SARS-CoV-2 and cytokines in the airways mucosa 37 patients who were suspected of COVID-19. According to the RT-PCR results, the patients were separated into three groups: negative for COVID-19 and other viruses (NEGS, n = 5); negative for COVID-19 but positive for the presence of other viruses (OTHERS, n = 5); and the positive for COVID-19 (COVID-19, n = 27). Higher specific-SIgA for SARS-CoV-2, IFN-β, and IFN-γ were found in the COVID-19 group than in the other groups. Increased IL-12p70 levels were observed in OTHERS group as compared to COVID-19 group. When the COVID-19 group was sub stratified according to the illness severity, significant differences and correlations were found for the same parameters described above comparing severe COVID-19 to the mild COVID-19 group and other non-COVID-19 groups. For the first time, significant differences are shown in the airway's mucosa immune responses in different groups of patients with or without respiratory SARS-CoV-2 infection.

Elderly Subjects Supplemented with L-Glutamine Shows an Improvement of Mucosal Immunity in the Upper Airways in Response to Influenza Virus Vaccination

BACKGROUND

Although glutamine is able to improve the immune response, its action in the upper airway immunity against the influenza virus vaccine remains unclear. Therefore, we aimed to evaluate the L-glutamine supplementation effect on the mucosal immune/inflammatory response of elderly subjects vaccinated against the influenza virus.

METHODS

Saliva sampling from 83 physically active elderly volunteers were collected pre- and 30 days after influenza virus vaccination and supplementation with L-glutamine (Gln, n = 42) or placebo (PL, n = 41).

RESULTS

Gln group showed higher salivary levels of interleukin (IL)-17, total secretory immunoglobulin A (SIgA), and specific-SIgA post-vaccination than values found pre-vaccination and in the PL group post-vaccination. Whereas higher salivary levels of IL-6 and IL-10 were observed post-vaccination in the Gln group, IL-37 levels were lower post-vaccination in both groups than the values pre-vaccination. Tumor necrosis factor (TNF)-α levels were unchanged. Positive correlations between IL-6 and IL-10 were found in all volunteer groups pre- and post-vaccination and also between IL-17 and IL-6 or IL-10 in the Gln group post-vaccination. A negative correlation between IL-37 and IL-10 was found pre- and post-vaccination in the PL group.

CONCLUSION

Gln supplementation was able to modulate salivary cytokine profile and increase SIgA levels, both total and specific to the influenza virus vaccine, in physically active elderly subjects.

Induction of protective immune response to intranasal administration of influenza virus-like particles in a mouse model

Human influenza A viruses (IAVs) cause global pandemics and epidemics, which remains a nonignorable serious concern for public health worldwide. To combat the surge of viral outbreaks, new treatments are urgently needed. Here, we design a new vaccine based on virus-like particles (VLPs) and show how intranasal administration of this vaccine triggers protective immunity, which can be exploited for the development of new therapies. H1N1 VLPs were produced in baculovirus vectors and were injected into BALB/c mice by the intramuscular (IM) or intranasal (IN) route. We found that there were significantly higher inflammatory cell and lymphocyte concentrations in bronchoalveolar lavage samples and the lungs of IN immunized mice; however, the IM group had little signs of inflammatory responses. On the basis of our results, immunization with H1N1 influenza VLP elicited a strong T cell immunity in BALB/c mice. Despite T cell immunity amplification after both IN and IM vaccination methods in mice, IN-induced T cell responses were significantly more intense than IM-induced responses, and this was likely related to an increased number of both CD11b^high and CD103⁺ dendritic cells in mice lungs after IN administration of VLP. Furthermore, evaluation of interleukin-4 and interferon gamma cytokines along with several chemokine receptors showed that VLP vaccination via IN and IM routes leads to a greater CD4⁺ Th1 and Th2 response, respectively. Our findings indicated that VLPs represent a potential strategy for the development of an effective influenza vaccine; however, employing relevant routes for vaccination can be another important part of the universal influenza vaccine puzzle.

Intranasal administration of inactivated avian influenza virus of H5N1 subtype vaccine-induced systemic immune response in chicken and mice

Aim

The need for non-parenteral administration of inactivated avian influenza virus of H5N1 subtype (AIV-H5N1) vaccine is paramount. Here, we provide preliminary data on the immune response of chicken and mice after intranasal administration of AIV-H5N1-inactivated vaccine with ISCOMS, Inmunair (INM), and combined ISCOMS and INM as an adjuvant.

Materials and Methods

The AIV isolate of A/Chicken/Denpasar/01/2004 (H5N1) was cultivated in specific pathogen-free chicken eggs and inactivated with formaldehyde. The vaccine preparation was added with those adjuvants for intranasal administration and aluminum hydroxide for subcutaneous injection. The chicken and mouse were vaccinated at the age of 3 weeks or 1 month and repeated 2 weeks thereafter. In one experiment, chicken was injected with Newcastle disease virus (NDV) at the same time with AIV vaccine. The sera were collected at one (serum 1) and 2 w (serum 2) after booster vaccination. The anti-AIV-H5 and NDV antibodies in chicken sera were detected using hemagglutination inhibition (HI) assay. Mouse IgG anti-AIV-H5N1 antibody was detected using ELISA.

Results

The result shows that the geometric mean titers (GMTs) of chicken sera of intranasal vaccinated with inactivated AIV-H5N1 vaccine with mixed ISCOM- INM as adjuvant were <2^0.0 and 2^2.7 unit HI-unit (HIU) in serum 1 and serum 2, respectively. The GMTs of the positive control group were 2^3.7 and 2^5.7 HIU in serum 1 and serum 2, respectively. The result of the second experiment shows that IgG anti-AIV-H5N1 was detected in mouse sera. In the third experiment, the GMTs of anti-NDV in chicken vaccinated subsequently with inactivated NDV vaccine and AIV-H5N1 with mixed ISCOMS-INM administrated intranasally and aluminum hydroxide adjuvant administrated through subcutaneous injection as well as positive control group receiving NDV vaccine only were 2^8.0, 2^8.0, and 2^7.4 HIU in serum 1 while were 2^9.6, 2^9.2, and 2^8.2 HIU in serum 2, respectively.

Conclusion

Intranasal administration of inactivated AIV-H5N1 vaccine-induced a systemic immune response in chicken and mice after adding ISCOMS and/or INM as adjuvants. The adjuvant and the intranasal administration caused no immunosuppressive effect on the chicken immune response to NDV vaccine.

Evaluation of multivalent H2 influenza pandemic vaccines in mice

Subtype H2 Influenza A viruses were the cause of a severe pandemic in the winter of 1957. However, this subtype no longer circulates in humans and is no longer included in seasonal vaccines. As a result, individuals under 50years of age are immunologically naïve. H2 viruses persist in aquatic birds, which were a contributing source for the 1957 pandemic, and have also been isolated from swine. Reintroduction of the H2 via zoonotic transmission has been identified as a pandemic risk, so pre-pandemic planning should include preparation and testing of vaccine candidates against this subtype. We evaluated the immunogenicity of two inactivated, whole virus influenza vaccines (IVV) in mice: a monovalent IVV containing human pandemic virus A/Singapore/1/1957 (H2N2), and a multivalent IVV containing human A/Singapore/1/1957, avian A/Duck/HongKong/319/1978 (H2N2), and swine A/Swine/Missouri/2124514/2006 (H2N3) viruses. While both vaccines induced protective immunity compared to naïve animals, the multivalent formulation was advantageous over the monovalent in terms of level and breadth of serological responses, neutralization of infectious virus, and reduction of clinical disease and respiratory tissue replication in mice. Therefore, multivalent pandemic H2 vaccines containing diverse viruses from animal reservoirs, are a potential option to improve the immune responses in a pre-pandemic scenario where antigenic identity cannot be predicted.

Vaccine-induced Th17 cells are established as resident memory cells in the lung and promote local IgA responses

The ability to mount accelerated and efficient mucosal immune responses is critically important to prevent the establishment of many infections. Secretion of immunoglobulin A (IgA) is a key component in this first line of defense, but the underlying cellular mechanisms are still not completely understood. We have evaluated different routes of immunization and examined the requirements for IgA induction in the airway mucosa. We demonstrate that subcutaneous priming with a recombinant antigen in a T helper (Th)17-inducing adjuvant followed by airway boosting promotes high and sustained levels of IgA in the lungs. This response is associated with germinal center formation in the lung-draining lymph nodes. The lung IgA response is dependent on Th17 cells and absent if interleukin (IL)-17 is depleted or when priming with vaccines inducing only Th1 or Th2 responses. We used intravascular staining to demonstrate that IgA+ B cells and chemokine receptor 6 (CCR6)+Th17 cells are recruited to the lung parenchyma after the airway booster immunization. Once recruited to the lung parenchyma, the Th17 cells transform into resident lymphocytes that persist in the lung tissue for at least 10 weeks. Here, they facilitate the accelerated recruitment of T and B cells resulting in an accelerated IgA recall response to a second airway booster immunization.

Responses of primary human nasal epithelial cells to EDIII-DENV stimulation: the first step to intranasal dengue vaccination

Background

About half of the world’s population are living in the endemic area of dengue viruses implying that a rapid-mass vaccination may be required. In addition, a major target of dengue vaccine are children, thus, a needle-free administration is more attractive. These problems may be overcome by the alternative route of vaccination such as topical, oral and intranasal vaccination. Here, we investigated the possibility to deliver a dengue immunogen intranasally, a painless route of vaccination. The tested immunogen was the domain III of dengue serotype-3 E protein (EDIII-D3) loaded into trimethyl chitosan nanoparticles (EDIII-D3 TMC NPs). The primary human nasal epithelial cells, HNEpCs, were used as an in vitro model for nasal responses.

Results

At tested concentrations, EDIII-D3 TMC NPs not only exerted no detectable toxicity toward HNEpC cultures but also efficiently delivered EDIII-D3 immunogens into HNEpCs. Moreover, HNEpCs quickly and strongly produced proinflammatory cytokines (IL-1β, IL-6, TNF-α), type-I IFN, the growth factors (GM-CSF, IL-7), the chemokines (MCP-1, MIP-1β, IL-8), Th1-related cytokines (IL-2, IL-12p70, IL-17, IFN-γ) and Th2-related cytokine (IL-4) in response to EDIII-D3 TMC NPs treatment.

Conclusions

A potential mucosal delivery system for dengue immunogens was revealed and found to stimulate a strong local innate antiviral response which possibly leading to a systemic adaptive immunity.

Cross-protective efficacies of highly-pathogenic avian influenza H5N1 vaccines against a recent H5N8 virus

To investigate cross-protective vaccine efficacy of highly-pathogenic avian influenza H5N1 viruses against a recent HPAI H5N8 virus, we immunized C57BL/6 mice and ferrets with three alum-adjuvanted inactivated whole H5N1 vaccines developed through reverse-genetics (Rg): [Vietnam/1194/04xPR8 (clade 1), Korea/W149/06xPR8 (clade 2.2), and Korea/ES223N/03xPR8 (clade 2.5)]. Although relatively low cross-reactivities (10-40 HI titer) were observed against heterologous H5N8 virus, immunized animals were 100% protected from challenge with the 20 mLD50 of H5N8 virus, with the exception of mice vaccinated with 3.5μg of Rg Vietnam/1194/04xPR8. Of note, the Rg Korea/ES223N/03xPR8 vaccine provided not only effective protection, but also markedly inhibited viral replication in the lungs and nasal swabs of vaccine recipients within five days of HPAI H5N8 virus challenge. Further, we demonstrated that antibody-dependent cell-mediated cytotoxicity (ADCC) of an antibody-coated target cell by cytotoxic effector cells also plays a role in the heterologous protection of H5N1 vaccines against H5N8 challenge.

Intranasal Immunization of Mice to Avoid Interference of Maternal Antibody against H5N1 Infection

Maternally-derived antibodies (MDAs) can protect offspring against influenza virus infection but may also inhibit active immune responses. To overcome MDA- mediated inhibition, active immunization of offspring with an inactivated H5N1 whole-virion vaccine under the influence of MDAs was explored in mice. Female mice were vaccinated twice via the intraperitoneal (IP) or intranasal (IN) route with the vaccine prior to mating. One week after birth, the offspring were immunized twice via the IP or IN route with the same vaccine and then challenged with a lethal dose of a highly homologous virus strain. The results showed that, no matter which immunization route (IP or IN) was used for mothers, the presence of MDAs severely interfered with the active immune response of the offspring when the offspring were immunized via the IP route. Only via the IN immunization route did the offspring overcome the MDA interference. These results suggest that intranasal immunization could be a suitable inoculation route for offspring to overcome MDA interference in the defense against highly pathogenic H5N1 virus infection. This study may provide references for human and animal vaccination to overcome MDA-induced inhibition.