Induction of innate immunity by nasal influenza vaccine administered in combination with an adjuvant (cholera toxin)

Oral mucosa immunity: ultimate strategy to stop spreading of pandemic viruses

Global pandemics are most likely initiated via zoonotic transmission to humans in which respiratory viruses infect airways with relevance to mucosal systems. Out of the known pandemics, five were initiated by respiratory viruses including current ongoing coronavirus disease 2019 (COVID-19). Striking progress in vaccine development and therapeutics has helped ameliorate the mortality and morbidity by infectious agents. Yet, organism replication and virus spread through mucosal tissues cannot be directly controlled by parenteral vaccines. A novel mitigation strategy is needed to elicit robust mucosal protection and broadly neutralizing activities to hamper virus entry mechanisms and inhibit transmission. This review focuses on the oral mucosa, which is a critical site of viral transmission and promising target to elicit sterile immunity. In addition to reviewing historic pandemics initiated by the zoonotic respiratory RNA viruses and the oral mucosal tissues, we discuss unique features of the oral immune responses. We address barriers and new prospects related to developing novel therapeutics to elicit protective immunity at the mucosal level to ultimately control transmission.

Oral vaccination with recombinant Lactobacillus casei with surface displayed OmpK fused to CTB as an adjuvant against Vibrio mimicus infection in Carassius auratus

Vibrio mimicus (V. mimicus) is a pathogenic bacterium that causes diseases in humans and various aquatic animals. A particularly efficient way to provide protection against V. mimicus is through vaccination. However, there are few commercial vaccines against V. mimics, especially oral vaccines. In our study, two surface-display recombinant Lactobacillus casei (L. casei) Lc-pPG-OmpK and Lc-pPG-OmpK-CTB were constructed using L. casei ATCC393 as an antigen delivery vector, outer membrane protein K (OmpK) of V. mimicus as an antigen, and cholera toxin B subunit (CTB) as a molecular adjuvant; furthermore, the immunological effects of recombinant L.casei in Carassius auratus (C. auratus) were assessed. The results indicated that oral recombinant L.casei Lc-pPG-OmpK and Lc-pPG-OmpK-CTB stimulated higher levels of serum-specific immunoglobulin M (IgM) and increased the activity of acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD), lysozyme (LYS), lectin, C3, and C4 in C. auratus, compared with control groups (Lc-pPG group and PBS group). Furthermore, the expression of interleukin-1β (IL-1β), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) in the liver, spleen, head kidney, hind intestine and gills of C. auratus was significantly increased, compared with that in the controls. These results demonstrated that the two recombinant L. casei strains could effectively trigger humoral and cellular immunity in C. auratus. In addition, two recombinant L.casei strains were able to survive and colonize the intestine of C. auratus. Importantly, after being challenged with V. mimicus, C. auratus fed Lc-pPG-OmpK and Lc-pPG-OmpK-CTB exhibited greater survival rates than the controls (52.08% and 58.33%, respectively). The data showed that recombinant L. casei could elicit a protective immunological response in C. auratus. The effect of the Lc-pPG-OmpK-CTB group was better than that of the Lc-pPG-OmpK group, and Lc-pPG-OmpK-CTB was found to be an effective candidate for oral vaccination.

Oral Bacteria Combined with an Intranasal Vaccine Protect from Influenza A Virus and SARS-CoV-2 Infection

The gut microbiota plays a critical role in the induction of adaptive immune responses to influenza virus infection. However, the role of nasal bacteria in the induction of the virus-specific adaptive immunity is less clear. Here, we found that disruption of nasal bacteria by intranasal application of antibiotics before influenza virus infection enhanced the virus-specific antibody response in a MyD88-dependent manner. Similarly, disruption of nasal bacteria by lysozyme enhanced antibody responses to intranasally administered influenza virus hemagglutinin (HA) vaccine in a MyD88-dependent manner, suggesting that intranasal application of antibiotics or lysozyme could release bacterial pathogen-associated molecular patterns (PAMPs) from disrupted nasal bacteria that act as mucosal adjuvants by activating the MyD88 signaling pathway. Since commensal bacteria in the nasal mucosal surface were significantly lower than those in the oral cavity, intranasal administration of HA vaccine alone was insufficient to induce the vaccine-specific antibody response. However, intranasal supplementation of cultured oral bacteria from a healthy human volunteer enhanced antibody responses to an intranasally administered HA vaccine. Finally, we demonstrated that oral bacteria combined with an intranasal vaccine protect from influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Our results reveal the role of nasal bacteria in the induction of the virus-specific adaptive immunity and provide clues for developing better intranasal vaccines.

Nonthermal plasma as part of a novel strategy for vaccination

Vaccination has been one of the most effective health intervention mechanisms to reduce morbidity and mortality associated with infectious diseases. Vaccines stimulate the body's protective immune responses through controlled exposure to modified versions of pathogens that establish immunological memory. However, only a few diseases have effective vaccines. The biological effects of nonthermal plasma on cells suggest that plasma could play an important role in improving efficacy of existing vaccines and overcoming some of the limitations and challenges with current vaccination strategies. This review summarizes the opportunities for nonthermal plasma for immunization and therapeutic purposes.

Mucosal Vaccination for Influenza Protection Enhanced by Catalytic Immune-Adjuvant

Influenza poses a severe threat to global health. Despite the whole inactivated virus (WIV)-based nasal vaccine being a promising strategy for influenza protection, the mucosal barrier is still a bottleneck of the nasal vaccine. Here, a catalytic mucosal adjuvant strategy for an influenza WIV nasal vaccine based on chitosan (CS) functionalized iron oxide nanozyme (IONzyme) is developed. The results reveal that CS-IONzyme increases antigen adhesion to nasal mucosa by 30-fold compared to H1N1 WIV alone. Next, CS-IONzyme facilitates H1N1 WIV to enhance CCL20-driven submucosal dendritic cell (DC) recruitment and transepithelial dendrite(TED) formation for viral uptake via the toll-like receptor(TLR) 2/4-dependent pathway. Moreover, IONzyme with enhanced peroxidase (POD)-like activity by CS modification catalyzes a reactive oxygen species (ROS)-dependent DC maturation, which further enhances the migration of H1N1 WIV-loaded DCs into the draining lymph nodes for antigen presentation. Finally, CS-IONzyme-based nasal vaccine triggers an 8.9-fold increase of IgA-mucosal adaptive immunity in mice, which provides a 100% protection against influenza, while only a 30% protection by H1N1 WIV alone. This work provides an antiviral alternative for designing nasal vaccines based on IONzyme to combat influenza infection.

Intranasal Inactivated Influenza Vaccines: a Reasonable Approach to Improve the Efficacy of Influenza Vaccine?

Influenza is a contagious, acute respiratory disease caused by the influenza virus. The mucosal lining in the host respiratory tract is not only the site of virus infection, but also the site of defense; it is at this site that the host immune response targets the virus and protects against reinfection. One of the most effective methods to prevent influenza is to induce specific antibody (Ab) responses in the respiratory tract by vaccination. Two types of influenza vaccines, intranasal live attenuated influenza virus (LAIV) vaccines and parenteral (injectable) inactivated vaccines, are currently used worldwide. These vaccines are approved by the European Medicines Agency (EMA) and the US Food and Drug Administration. Live attenuated vaccines induce both secretory IgA (S-IgA) and serum IgG antibodies (Abs), whereas parenteral vaccines induce only serum IgG Abs. However, intranasal administration of inactivated vaccines together with an appropriate adjuvant induces both S-IgA and IgG Abs. Several preclinical studies on adjuvant-combined, nasal-inactivated vaccines revealed that nasal S-IgA Abs, a major immune component in the upper respiratory tract, reacted with homologous virus hemagglutinin (HA) and were highly cross-reactive with viral HA variants, resulting in protection and cross-protection against infection by both homologous and variant viruses, respectively. Serum-derived IgG Abs, which are present mainly in the lower respiratory tract, are less cross-reactive and cross-protective. In addition, our own clinical trials have shown that nasal-inactivated whole virus vaccines, including a built-in adjuvant (single-stranded RNA), induced serum hemagglutination inhibition (HI) Ab titers that fulfilled the EMA criteria for vaccine efficacy. The nasal-inactivated whole virus vaccines also induced high levels of nasal HI and neutralizing Ab titers, although we have not yet evaluated the nasal HI titers due to the lack of official criteria to establish efficacy based on this parameter. Data suggest that adjuvant-combined nasal-inactivated vaccines have advantages over the current injectable vaccine because the former induce both S-IgA and serum IgG Abs. In addition, nasal-inactivated vaccines seem to be superior to the LAIV vaccines, because non-infectious preparations could be used in high-risk groups. Thus, the development of intranasal inactivated vaccines is recommended, because such vaccines are expected to improve the efficacy of influenza vaccines.

Antigen-Independent Restriction of Pneumococcal Density by Mucosal Adjuvant Cholera Toxin Subunit B

For many bacterial respiratory infections, development of (severe) disease is preceded by asymptomatic colonization of the upper airways. For Streptococcus pneumoniae, the transition to severe lower respiratory tract infection is associated with an increase in nasopharyngeal colonization density. Insight into how the mucosal immune system restricts colonization may provide new strategies to prevent clinical symptoms. Several studies have provided indirect evidence that the mucosal adjuvant cholera toxin subunit B (CTB) may confer nonspecific protection against respiratory infections. Here, we show that CTB reduces the pneumococcal load in the nasopharynx, which required activation of the caspase-1/11 inflammasome, mucosal T cells, and macrophages. Our findings suggest that CTB-dependent activation of the local innate response synergizes with noncognate T cells to restrict bacterial load. Our study not only provides insight into the immunological components required for containment and clearance of pneumococcal carriage, but also highlights an important yet often understudied aspect of adjuvants.

Evaluation of dual nasal delivery of infectious hematopoietic necrosis virus and enteric red mouth vaccines in rainbow trout (Oncorhynchus mykiss)

Farmed fish are susceptible to different infectious disease agents including viruses and bacteria. Thus, multivalent vaccines or vaccination programs against two or more pathogens are valuable tools in aquaculture. Recently, nasal vaccines have been shown to be very effective in rainbow trout. The current study investigates, for the first time, the use of the nasal route in dual vaccination trials against two important aquatic diseases, infectious hematopoietic necrosis virus (IHN) and enteric red mouth (ERM) disease. Rainbow trout received live attenuated IHN virus (IHNV) vaccine and the ERM bacterin using four different vaccine delivery methods and were challenged with virulent IHNV or Yersinia ruckeri 7 (100 deg day) and 28 (400 deg day) days post-vaccination. The highest survival rates against IHNV at day 7 were obtained by nasal vaccination either when IHNV and ERM were delivered separately into each nare or when they were premixed and delivered to both nasal rosettes (group D). Protection at 28 days against IHNV was similar in all four vaccinated groups. Early protection against ERM was highest in fish that received each vaccine in separate nares (group B), whereas protection at 28 days was highest in the i.p. vaccinated group (group E), followed by the nasally vaccinated group (group B). Survival results were supported by histological observations of the left and right olfactory organ which showed strong immune responses one day (14 deg days) after vaccination in group B vaccinated fish. These data indicate that dual vaccination against two different pathogens via the nasal route is a very effective vaccination strategy for use in aquaculture, particularly when each nare is used separately during delivery. Further long-term studies should evaluate the contribution of adaptive immunity to the protection levels observed.

Intranasal coadministration of Cholera toxin with amoeba lysates modulates the secretion of IgA and IgG antibodies, production of cytokines and expression of pIgR in the nasal cavity of mice in the model of Naegleria fowleri meningoencephalitis

The nasal mucosa is the first contact with antigens to induce IgA response. The role of this site has rarely been studied. We have shown than intranasal administration with Naegleria fowleri lysates plus Cholera toxin (CT) increased the protection (survival up to 100%) against N. fowleri infection in mice and apparently antibodies IgA and IgG together with polymorphonuclear (PMN) cells avoid the attachment of N. fowleri to apical side of the nasal epithelium. We also observed that nasal immunization resulted in the induction of antigen-specific IgG subclasses (IgG1 and IgG2a) in nasal washes at days 3 and 9 after the challenge and IgA and IgG in the nasal cavity, compared to healthy and infected mice. We found that immunization with both treatments, N. fowleri lysates plus CT or CT alone, increased the expression of the genes for alpha chain, its receptor (pIgR), and it also increased the expression of the corresponding proteins evidenced by the ∼65 and ∼74kDa bands, respectively. Since the production of pIgR, IgA and IgG antibodies, is up-regulated by some factors, we analyzed the expression of genes for IL-10, IL-6, IFN-γ, TNF-α and IL-1β by using RT-PCR of nasal passages. Immunization resulted in an increased expression of IL-10, IL-6, and IFN-γ cytokines. We also aimed to examine the possible influences of immunization and challenge on the production of inflammatory cytokines (TNF-α and IL-1β). We observed that the stimulus of immunization inhibits the production of TNF-α compared to the infected group where the infection without immunization causes an increase in it. Thus, it is possible that the coexistence of selected cytokines produced by our immunization model may provide a highly effective immunological environment for the production of IgA, IgG and pIgR as well as a strong activation of the PMN in mucosal effector tissue such as nasal passages.

Partial protection against chlamydial reproductive tract infection by a recombinant major outer membrane protein/CpG/cholera toxin intranasal vaccine in the guinea pig Chlamydia caviae model

Chlamydia trachomatis is a major cause of sexually transmitted diseases worldwide. There is currently no vaccine to protect against chlamydial infection of the female reproductive tract. Vaccine development has predominantly utilised the murine model; however, infection of female guinea pigs with Chlamydia caviae more closely resembles chlamydial infection of the human female reproductive tract, and presents a better model to assess potential human chlamydial vaccines. We immunised female guinea pigs intranasally with recombinant major outer membrane protein (r-MOMP) combined with CpG-10109 and cholera toxin adjuvants. Both systemic and mucosal immune responses were elicited in immunised animals, with MOMP-specific IgG and IgA present in the vaginal mucosae, and high levels of MOMP-specific IgG detected in the serum. Antibodies from the vaginal mucosae were also capable of neutralising C. caviae in vitro. Following immunisation, animals were challenged intravaginally with 10(2) inclusion forming units of live C. caviae. We observed a decrease in the duration of infection and a significant (p<0.025) reduction in infection load in r-MOMP-immunised animals, compared with animals immunised with adjuvant only. Importantly, we also observed a marked reduction in upper reproductive tract pathology in r-MOMP-immunised animals. Intranasal immunisation of female guinea pigs with r-MOMP was able to provide partial protection against C. caviae infection, by reducing not only chlamydial burden, but also upper reproductive tract pathology. This data demonstrates the value of using the guinea pig model to evaluate potential chlamydial vaccines for protection against infection and disease pathology caused by C. trachomatis in the female reproductive tract.

Adjuvanted, antigen loaded N-trimethyl chitosan nanoparticles for nasal and intradermal vaccination: adjuvant- and site-dependent immunogenicity in mice

N-trimethyl chitosan (TMC) nanoparticles have been shown to increase the immunogenicity of subunit antigens after nasal and intradermal administration. This work describes a second generation of TMC nanoparticles containing ovalbumin as a model antigen (TMC/OVA nanoparticles) and an immunopotentiator (TMC/OVA/immunopotentiator nanoparticles). The selection of immunopotentiators included Toll-like receptor (TLR) ligands lipopolysaccharide (LPS), PAM(3)CSK(4) (PAM), CpG DNA, the NOD-like receptor 2 ligand muramyl dipeptide (MDP) and the GM1 ganglioside receptor ligand, cholera toxin B subunit (CTB). The TMC/OVA/immunopotentiator nanoparticles were characterised physico-chemically and their immunogenicity was assessed by determining the serum IgG, IgG1, IgG2a titres and secretory IgA levels in nasal washes after intradermal and nasal vaccination in mice. After nasal vaccination, TMC/OVA nanoparticles containing LPS or MDP elicited higher IgG, IgG1 and sIgA levels than non-adjuvanted TMC/OVA particles, whereas nanoparticles containing CTB, PAM or CpG did not. After intradermal vaccination, the TMC/OVA/CpG and TMC/OVA/LPS nanoparticles provoked higher IgG titres than plain TMC/OVA particles. Altogether, our results show that co-encapsulation of an additional immunopotentiator with the antigen into TMC nanoparticles can further improve the immunogenicity of the vaccine. However, the strength and quality of the response depends on the immunopotentiator as well as the route of administration.

A lack of antibody formation against inactivated influenza virus after aerosol vaccination in presence or absence of adjuvantia

In the poultry industry, infections with avian influenza virus (AIV) can result in significant economic losses. The risk and the size of an outbreak might be restricted by vaccination of poultry. A vaccine that would be used for rapid intervention during an outbreak should be safe to use, highly effective after a single administration and be suitable for mass application. A vaccine that could be applied by spray or aerosol would be suitable for mass application, but respiratory applied inactivated influenza is poorly immunogenic and needs to be adjuvanted. We chose aluminum OH, chitosan, cholera toxin B subunit (CT-B), and Stimune as adjuvant for an aerosolized vaccine with inactivated H9N2. Each adjuvant was tested in two doses. None of the adjuvanted vaccines induced AIV-specific antibodies after single vaccination, measured 1 and 3 weeks after vaccination by aerosol, in contrast to the intramuscularly applied vaccine. The aerosolized vaccine did enter the chickens' respiratory tract as CT-B-specific serum antibodies were detected after 1 week in chickens vaccinated with the CT-B-adjuvanted vaccine. Chickens showed no adverse effects after the aerosol vaccination based on weight gain and clinical signs. The failure to detect AIV-specific antibodies might be due to the concentration of the inactivated virus.

Multistrain influenza protection induced by a nanoparticulate mucosal immunotherapeutic

All commercial influenza vaccines elicit antibody responses that protect against seasonal infection, but this approach is limited by the need for annual vaccine reformulation that precludes efficient responses against epidemic and pandemic disease. In this study we describe a novel vaccination approach in which a nanoparticulate, liposome-based agent containing short, highly conserved influenza-derived peptides is delivered to the respiratory tract to elicit potent innate and selective T cell-based adaptive immune responses. Prepared without virus-specific peptides, mucosal immunostimulatory therapeutic (MIT) provided robust, but short-lived, protection against multiple, highly lethal strains of influenza in mice of diverse genetic backgrounds. MIT prepared with three highly conserved epitopes that elicited virus-specific memory T-cell responses but not neutralizing antibodies, termed MITpep, provided equivalent, but more durable, protection relative to MIT. Alveolar macrophages were more important than dendritic cells in determining the protective efficacy of MIT, which induced both canonical and non-canonical antiviral immune pathways. Through activation of airway mucosal innate and highly specific T-cell responses, MIT and MITpep represent novel approaches to antiviral protection that offer the possibility of universal protection against epidemic and pandemic influenza.

Prophylactic administration of bacterially derived immunomodulators improves the outcome of influenza virus infection in a murine model

Prophylactic or therapeutic immunomodulation is an antigen-independent strategy that induces nonspecific immune system activation, thereby enhancing host defense to disease. In this study, we investigated the effect of prophylactic immunomodulation on the outcome of influenza virus infection using three bacterially derived immune-enhancing agents known for promoting distinct immunological profiles. BALB/c mice were treated nasally with either cholera toxin (CT), a mutant form of the CT-related Escherichia coli heat-labile enterotoxin designated LT(R192G), or CpG oligodeoxynucleotide. Mice were subsequently challenged with a lethal dose of influenza A/PR/8/34 virus 24 h after the last immunomodulation treatment and either monitored for survival or sacrificed postchallenge for viral and immunological analysis. Treatment with the three immunomodulators prevented or delayed mortality and weight loss, but only CT and LT(R192G) significantly reduced initial lung viral loads as measured by plaque assay. Analysis performed 4 days postinfection indicated that prophylactic treatments with CT, LT(R192G), or CpG resulted in significantly increased numbers of CD4 T cells, B cells, and dendritic cells and altered costimulatory marker expression in the airways of infected mice, coinciding with reduced expression of pulmonary chemokines and the appearance of inducible bronchus-associated lymphoid tissue-like structures in the lungs. Collectively, these results suggest that, despite different immunomodulatory mechanisms, CT, LT(R192G), and CpG induce an initial inflammatory process and enhance the immune response to primary influenza virus challenge while preventing potentially damaging chemokine expression. These studies provide insight into the immunological parameters and immune modulation strategies that have the potential to enhance the nonspecific host response to influenza virus infection.

Effects of the administration of cholera toxin as a mucosal adjuvant on the immune and protective response induced by Proteus mirabilis MrpA fimbrial protein in the urinary tract

Proteus mirabilis is commonly associated with complicated UTI and expresses several virulence factors, including MR/P fimbriae. In the present study mice were immunised nasally with MrpA, the structural subunit of MR/P, with or without CT as a mucosal adjuvant. The animals were then challenged with P. mirabilis and induction of specific serum and urine IgG and IgA, IFN-gamma production and bacterial kidney and bladder colonization were assessed. MrpA-immunised mice exhibited significant induction of serum IgA and urine IgA and IgG. MrpA/CT-immunised mice showed both significant serum and urine IgA and IgG production. Only this group showed significant IFN-y production. Both groups of animals had significant decrease in bacterial colonization of kidneys but not of bladders. No correlation between specific antibody induction in serum and CFU decrease was observed in any group of animals. Our results suggest that a mucosal adjuvant (CT) in the urinary tract enhanced humoral and cytokine response although it did not influence the degree of protection against UTI provided by MrpA. Further studies are necessary to understand immune modulation in the urinary tract.

Incorporation of membrane-bound, mammalian-derived immunomodulatory proteins into influenza whole virus vaccines boosts immunogenicity and protection against lethal challenge

Background

Influenza epidemics continue to cause morbidity and mortality within the human population despite widespread vaccination efforts. This, along with the ominous threat of an avian influenza pandemic (H5N1), demonstrates the need for a much improved, more sophisticated influenza vaccine. We have developed an in vitro model system for producing a membrane-bound Cytokine-bearing Influenza Vaccine (CYT-IVAC). Numerous cytokines are involved in directing both innate and adaptive immunity and it is our goal to utilize the properties of individual cytokines and other immunomodulatory proteins to create a more immunogenic vaccine.

Results

We have evaluated the immunogenicity of inactivated cytokine-bearing influenza vaccines using a mouse model of lethal influenza virus challenge. CYT-IVACs were produced by stably transfecting MDCK cell lines with mouse-derived cytokines (GM-CSF, IL-2 and IL-4) fused to the membrane-anchoring domain of the viral hemagglutinin. Influenza virus replication in these cell lines resulted in the uptake of the bioactive membrane-bound cytokines during virus budding and release. In vivo efficacy studies revealed that a single low dose of IL-2 or IL-4-bearing CYT-IVAC is superior at providing protection against lethal influenza challenge in a mouse model and provides a more balanced Th₁/Th₂ humoral immune response, similar to live virus infections.

Conclusion

We have validated the protective efficacy of CYT-IVACs in a mammalian model of influenza virus infection. This technology has broad applications in current influenza virus vaccine development and may prove particularly useful in boosting immune responses in the elderly, where current vaccines are minimally effective.

FimH adhesin of type 1 fimbriae is a potent inducer of innate antimicrobial responses which requires TLR4 and type 1 interferon signalling

Components of bacteria have been shown to induce innate antiviral immunity via Toll-like receptors (TLRs). We have recently shown that FimH, the adhesin portion of type 1 fimbria, can induce the innate immune system via TLR4. Here we report that FimH induces potent in vitro and in vivo innate antimicrobial responses. FimH induced an innate antiviral state in murine macrophage and primary MEFs which was correlated with IFN-beta production. Moreover, FimH induced the innate antiviral responses in cells from wild type, but not from MyD88(-/-), Trif(-/-), IFN-alpha/betaR(-/-) or IRF3(-/-) mice. Vaginal delivery of FimH, but not LPS, completely protected wild type, but not MyD88(-/-), IFN-alpha/betaR(-/-), IRF3(-/-) or TLR4(-/-) mice from subsequent genital HSV-2 challenge. The FimH-induced innate antiviral immunity correlated with the production of IFN-beta, but not IFN-alpha or IFN-gamma. To examine whether FimH plays a role in innate immune induction in the context of a natural infection, the innate immune responses to wild type uropathogenic E. coli (UPEC) and a FimH null mutant were examined in the urinary tract of C57Bl/6 (B6) mice and TLR4-deficient mice. While UPEC expressing FimH induced a robust polymorphonuclear response in B6, but not TLR4(-/-) mice, mutant bacteria lacking FimH did not. In addition, the presence of TLR4 was essential for innate control of and protection against UPEC. Our results demonstrate that FimH is a potent inducer of innate antimicrobial responses and signals differently, from that of LPS, via TLR4 at mucosal surfaces. Our studies suggest that FimH can potentially be used as an innate microbicide against mucosal pathogens.

Roles of adjuvant and route of vaccination in antibody response and protection engendered by a synthetic matrix protein 2-based influenza A virus vaccine in the mouse

Background

The M2 ectodomain (M2e) of influenza A virus (IAV) strains that have circulated in humans during the past 90 years shows remarkably little structural diversity. Since M2e-specific antibodies (Abs) are capable of restricting IAV replication in vivo but are present only at minimal concentration in human sera, efforts are being made to develop a M2e-specific vaccine. We are exploring a synthetic multiple antigenic peptide (MAP) vaccine and here report on the role of adjuvants (cholera toxin and immunostimulatory oligodeoxynucleotide) and route of immunization on Ab response and strength of protection.

Results

Independent of adjuvants and immunization route, on average 87% of the M2e-MAP-induced Abs were specific for M2e peptide and a variable fraction of these M2e(pep)-specific Abs (average 15%) cross-reacted with presumably native M2e expressed by M2-transfected cells. The titer of these cross-reactive M2e(pep-nat)-specific Abs in sera of parenterally immunized mice displayed a sigmoidal relation to level of protection, with EC₅₀ of ~20 μg Ab/ml serum, though experiments with passive M2e(pep-nat) Abs indicated that serum Abs did not fully account for protection in parenterally vaccinated mice, particularly in upper airways. Intranasal vaccination engendered stronger protection and a higher proportion of G2a Abs than parenteral vaccination, and the strength of protection failed to correlate with M2e(pep-nat)-specific serum Ab titers, suggesting a role of airway-associated immunity in protection of intranasally vaccinated mice. Intranasal administration of M2e-MAP without adjuvant engendered no response but coadministration with infectious IAV slightly enhanced the M2e(pep-nat) Ab response and protection compared to vaccination with IAV or adjuvanted M2e-MAP alone.

Conclusion

M2e-MAP is an effective immunogen as ~15% of the total M2e-MAP-induced Ab response is of desired specificity. While M2e(pep-nat)-specific serum Abs have an important role in restricting virus replication in trachea and lung, M2e-specific T cells and/or locally produced Abs contribute to protection in upper airways. Intranasal vaccination is preferable to parenteral vaccination, presumably because of induction of local protective immunity by the former route. Intranasal coadministration of M2e-MAP with infectious IAV merits further investigation in view of its potential applicability to human vaccination with live attenuated IAV.

A phenotypic and functional characterization of NK cells in adenoids

Adenoids are part of the MALT. In the present study, we analyzed cell surface markers and cytolytic activity of adenoidal NK (A-NK) cells and compared them with NK cells derived from blood of the same donors (B-NK). NK cells comprised 0.67% (0.4-1.2%) of the total lymphoid population isolated from adenoids. The majority (median=92%) of the A-NK cells was CD56(bright)CD16(-). A-NK cells were characterized by the increased expression of activation-induced receptors. NKp44 was detected on >60%, CD25 on >40%, and HLA-DR on >50% of freshly isolated A-NK cells. Functional assays indicated that the cytotoxic machinery of A-NK is intact, and sensitive target cells are killed via natural cytotoxicity receptors, such as NKG2D. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1; CD66) expression was up-regulated in 23% (median) of the A-NK cells by IL-2 activation but unchanged in B-NK cells. CEACAM1 inhibited the A-NK killing of target cells. CXCR4 was expressed on more than 40% A-NK cells prior to activation. Its ligand, CXCL12, was found in endothelial cells of the capillaries within the adenoid and in cells of the epithelial lining. In addition, A-NK cells migrated in vitro toward a gradient of CXCL12 in a dose-responsive manner, suggesting a role for this chemokine in A-NK cell recruitment and trafficking. We conclude that the A-NK cells are unique in that they display an activated-like phenotype and are different from their CD16(-) B-NK cell counterparts. This phenotype presumably reflects the chronic interaction of A-NK cells with antigens penetrating the body through the nasal route.

Oral intake of Lactobacillus fermentum CECT5716 enhances the effects of influenza vaccination

OBJECTIVE

We studied the coadjuvant capability of oral consumption of the breast-milk-isolated strain Lactobacillus fermentum (CECT5716) for an anti-influenza vaccine.

METHODS

A randomized, double-blinded, placebo-controlled human clinical trial including 50 volunteers (31 male and 19 female) was performed to address the immunologic effects of an intramuscular anti-influenza vaccine in adults (33.0 +/- 7.7 y old). Fifty percent of volunteers received an oral daily dose of methylcellulose (placebo) or probiotic bacteria (1 x 10(10) colony-forming units/d) 2 wk before vaccination and 2 wk after vaccination.

RESULTS

Two weeks after vaccination there was an increase in the proportion of natural killer cells in the probiotic group but not in the placebo group. The vaccination induced an increase in T-helper type 1 cytokine concentrations and in T-helper and T-cytotoxic proportions in both groups; however, the probiotic group showed a significant higher induction in some of these parameters. Regarding the humoral effects, induction of antibody response in the placebo group could not be detected. In the case of the probiotic group, a significant increase in antigen specific immunoglobulin A was detected. Although an increase in total immunoglobulin M was observed, changes in anti-influenza antigen specific immunoglobulin M were not observed. The incidence of an influenza-like illness during 5 mo after vaccination (October to February) was lower in the group consuming the probiotic bacteria.

CONCLUSION

Oral administration of the strain L. fermentum CECT5716 potentates the immunologic response of an anti-influenza vaccine and may provide enhanced systemic protection from infection by increasing the T-helper type 1 response and virus-neutralizing antibodies.

Intranasal immunization with the cholera toxin B subunit-pneumococcal surface antigen A fusion protein induces protection against colonization with Streptococcus pneumoniae and has negligible impact on the nasopharyngeal and oral microbiota of mice

One of the candidate proteins for a mucosal vaccine antigen against Streptococcus pneumoniae is PsaA (pneumococcal surface antigen A). Vaccines targeting mucosal immunity may raise concerns as to possible alterations in the normal microbiota, especially in the case of PsaA, which was shown to have homologs with elevated sequence identity in other viridans group streptococci. In this work, we demonstrate that intranasal immunization with a cholera toxin B subunit-PsaA fusion protein is able to protect mice against colonization with S. pneumoniae but does not significantly alter the natural oral or nasopharyngeal microbiota of mice.

Intranasal coadministration of the Cry1Ac protoxin with amoebal lysates increases protection against Naegleria fowleri meningoencephalitis

Cry1Ac protoxin has potent mucosal and systemic adjuvant effects on antibody responses to proteins or polysaccharides. In this work, we examined whether Cry1Ac increased protective immunity against fatal Naegleria fowleri infection in mice, which resembles human primary amoebic meningoencephalitis. Higher immunoglobulin G (IgG) than IgA anti-N. fowleri responses were elicited in the serum and tracheopulmonary fluids of mice immunized by the intranasal or intraperitoneal route with N. fowleri lysates either alone or with Cry1Ac or cholera toxin. Superior protection against a lethal challenge with 5 x 10(4) live N. fowleri trophozoites was achieved for immunization by the intranasal route. Intranasal immunization of N. fowleri lysates coadministered with Cry1Ac increased survival to 100%; interestingly, immunization with Cry1Ac alone conferred similar protection to that achieved with amoebal lysates alone (60%). When mice intranasally immunized with Cry1Ac plus lysates were challenged with amoebae, both IgG and IgA mucosal responses were rapidly increased, but only the increased IgG response persisted until day 60 in surviving mice. The brief rise in the level of specific mucosal IgA does not exclude the role that this isotype may play in the early defense against this parasite, since higher IgA responses were detected in nasal fluids of mice intranasally immunized with lysates plus either Cry1Ac or cholera toxin, which, indeed, were the treatments that provided the major protection levels. In contrast, serum antibody responses do not seem to be related to the protection level achieved. Both acquired and innate immune systems seem to play a role in host defense against N. fowleri infection, but further studies are required to elucidate the mechanisms involved in protective effects conferred by Cry1Ac, which may be a valuable tool to improve mucosal vaccines.

The Cholera Toxin-Derived CTA1-DD Vaccine Adjuvant Administered Intranasally Does Not Cause Inflammation or Accumulate in the Nervous Tissues

Although highly effective, the use of GM1-receptor binding holotoxins as nasal mucosal adjuvants has recently been cautioned due to the risk for their accumulation in the brain and other nervous tissues. Therefore we have explored the efficacy of the CTA1-DD adjuvant for its ability to enhance nasal immune responses in mice. We found that despite the lack of a mucosal binding element, the B cell-targeted CTA1-DD molecule was an equally strong adjuvant as cholera toxin (CT). The potency of CTA1-DD was not a result of endotoxin contamination because more than a 50-fold higher dose of LPS was needed to achieve a similar enhancement. Moreover, the adjuvant effect was TLR4-independent and absent in mutant CTA1-E112K-DD, lacking enzymatic activity. The CTA1-DD adjuvant augmented germinal center formations and T cell priming in the draining lymph nodes, and contrary to CT, promoted a balanced Th1/Th2 response with little effect on IgE Ab production. CTA1-DD did not induce inflammatory changes in the nasal mucosa, and most importantly did not bind to or accumulate in the nervous tissues of the olfactory bulb, whereas CT bound avidly to the nervous tissues. We believe that the nontoxic CTA1-DD adjuvant is an attractive solution to the current dilemma between efficacy and toxicity encountered in CT-holotoxin adjuvant or Escherichia coli heat-labile toxin-holotoxin adjuvant strategies and provides a safe and promising candidate to be included in future vaccines for intranasal administration.

Non-replicating mucosal and systemic vaccines: quantitative and qualitative differences in the Ag-specific CD8(+) T cell population in different tissues

Directed dissemination of Ag-specific CD8(+) T cells to infected organs or cancerous tissues is a prerequisite for optimal immunotherapy. Ag-specific CD8(+) T cells were quantitated in systemic and mucosal tissues after nasal, rectal, or cutaneous immunization with CTL epitope peptide and the adjuvant cholera toxin (CT). Mucosal and cutaneous immunization induced Ag-specific CD8(+) lymphocytes that were detectable in both mucosal and systemic compartments, suggesting a less strict distribution pattern than that known for B cells. However, optimal localization, activation and phenotype of these cells correlated with the route of immunization. In accordance with this observation, protection against a mucosal challenge with a virus expressing the CTL epitope was superior in mucosally-immunized animals.

Nasal drug delivery--possibilities, problems and solutions

This paper discusses the problems associated with nasal drug delivery and how it is possible, sometimes by means of quite simple concepts, to improve transport across the nasal membrane. In this way it is feasible to deliver efficiently challenging drugs such as small polar molecules, peptides and proteins and even the large proteins and polysaccharides used in vaccines or DNA plasmids exploited for DNA vaccines. The transport of drugs from the nasal cavity directly to the brain is also described and examples of studies in man, where this has been shown to be feasible, are discussed. Recent results from Phase I/II studies in man with a novel nasal chitosan vaccine delivery system are also described. Finally, the author's thoughts about the future for nasal drug delivery are also depicted.

B- and T-cell responses to the mycobacterium surface antigen PstS-1 in the respiratory tract and adjacent tissues. Role of adjuvants and routes of immunization

Induction of mucosal immunity in the respiratory tract is crucial for protection against respiratory infections. Here, we have investigated the effects of the routes of immunization as well as of three different adjuvants on the induction of mucosal immune responses. Mice were immunized using intranasal (i.n.) or intraperitoneal (i.p.) routes with the mycobacterium PstS-1 antigen. Cholera toxin (CT), detoxified pertussis toxin (detPT) and RU 41.740 from Klebsiella pneumoniae were compared as mucosal adjuvants. Our data showed that i.n. route of immunization induced the most favorable stimulation of mucosal antigen-specific IgA responses supported by mixed Th cells producing IL-4, IL-5, IFN-gamma. In contrast, i.p. immunizations elicited only enhancement of systemic responses, predominantly of the Th2 type. Furthermore, the use of CT as mucosal adjuvant resulted in the stimulation of a mixed Th cell response whereas detPT evoked mainly Th2 type of responses. Likewise CT, the RU 41.740 adjuvant elicited a mixed Th cell response, albeit supported by much lower numbers of CD4(+) T-cells. Thus, i.n. route of immunization favors the induction of mucosal and systemic immune responses, while the Th cell development at mucosal inductive site is influenced by the adjuvant used for immunizations.

Trachea, lung, and tracheobronchial lymph nodes are the major sites where antigen-presenting cells are detected after nasal vaccination of mice with human papillomavirus type 16 virus-like particles

Vaccination by the nasal route has been successfully used for the induction of immune responses. Either the nasal-associated lymphoid tissue (NALT), the bronchus-associated lymphoid tissue, or lung dendritic cells have been mainly involved. Following nasal vaccination of mice with human papillomavirus type 16 (HPV16) virus-like-particles (VLPs), we have previously shown that interaction of the antigen with the lower respiratory tract was necessary to induce high titers of neutralizing antibodies in genital secretions. However, following a parenteral priming, nasal vaccination with HPV16 VLPs did not require interaction with the lung to induce a mucosal immune response. To evaluate the contribution of the upper and lower respiratory tissues and associated lymph nodes (LN) in the induction of humoral responses against HPV16 VLPs after nasal vaccination, we localized the immune inductive sites and identified the antigen-presenting cells involved using a specific CD4(+) T-cell hybridoma. Our results show that the trachea, the lung, and the tracheobronchial LN were the major sites responsible for the induction of the immune response against HPV16 VLP, while the NALT only played a minor role. Altogether, our data suggest that vaccination strategies aiming to induce efficient immune responses against HPV16 VLP in the female genital tract should target the lower respiratory tract.

Intranasal gene transfer by chitosan-DNA nanospheres protects BALB/c mice against acute respiratory syncytial virus infection

Respiratory syncytial virus (RSV) infection is often associated in infancy with life-threatening bronchiolitis, which is also a major risk factor for the development of asthma. At present, no effective prophylaxis is available against RSV infection. Herein, we describe an effective prophylactic intranasal gene transfer strategy utilizing chitosan-DNA nanospheres (IGT), containing a cocktail of plasmid DNAs encoding all RSV antigens, except L. A single administration of IGT (25 microg/mouse) induces expression of the mRNA and proteins of all antigens in the lung and results in a significant reduction of viral titers and viral antigen load after acute RSV infection of these mice. IGT-administered mice show no significant change in airway reactivity to methacholine and no apparent pulmonary inflammation. Furthermore, IGT results in significant induction of RSV-specific IgG antibodies, nasal IgA antibodies, cytotoxic T lymphocytes, and interferon-gamma production in the lung and splenocytes compared with controls. Together, these results demonstrate the potential of IGT against acute RSV infection.

Protection against influenza virus infection in polymeric Ig receptor knockout mice immunized intranasally with adjuvant-combined vaccines

The role of secretory IgA in conferring cross-protective immunity was examined in polymeric (p)IgR knockout (KO) mice immunized intranasally with different inactivated vaccines prepared from A/PR/8/34 (H1N1), A/Yamagata/120/86 (H1N1), A/Beijing/262/95 (H1N1), and B/Ibaraki/2/85 viruses and infected with the A/PR/8/34 virus in the upper respiratory tract (RT)-restricting volume. In wild-type mice, immunization with A/PR/8/34 or its variant (A/Yamagata/120/86 and A/Beijing/262/95) vaccines conferred complete protection or partial cross-protection against infection, while the B-type virus vaccine failed to provide protection. The protection or cross-protection was accompanied by an increase in the nasal A/PR/8/34 hemagglutinin-reactive IgA concentration, which was estimated to be >30 times the serum IgA concentration and much higher than the nasal IgG concentration. In contrast, the blockade of transepithelial transport of dimeric IgA in pIgR-KO mice reduced the degree of protection or cross-protection, in parallel with the marked increase in serum IgA concentration and the decrease in nasal IgA concentration (about 20 and 0.3 times those in wild-type mice, respectively). The degree of the reduction of protection or cross-protection was moderately reversed by the low but non-negligible level of nasal IgA, transudates from the accumulated serum IgA. These results, together with the absence of the IgA-dependent cross-protection in the lower RT and the unaltered level of nasal or serum IgG in wild-type and pIgR-KO mice, confirm that the actively secreted IgA plays an important role in cross-protection against variant virus infection in the upper RT, which cannot be substituted by serum IgG.

Chitosan as a novel nasal delivery system for vaccines

A variety of different types of nasal vaccine systems has been described to include cholera toxin, microspheres, nanoparticles, liposomes, attenuated virus and cells and outer membrane proteins (proteosomes). The present review describes our work on the use of the cationic polysaccharide, chitosan as a delivery system for nasally administered vaccines. Several animal studies have been carried out on influenza, pertussis and diphtheria vaccines with good results. After nasal administration of the chitosan-antigen nasal vaccines it was generally found that the nasal formulation induced significant serum IgG responses similar to and secretory IgA levels superior to what was induced by a parenteral administration of the vaccine. Animals vaccinated via the nasal route with the various chitosan-antigen vaccines were also found to be protected against the appropriate challenge. So far the nasal chitosan vaccine delivery system has been tested for vaccination against influenza in human subjects. The results of the study showed that the nasal chitosan influenza vaccine was both effective and protective according to the CPMP requirements. The mechanism of action of the chitosan nasal vaccine delivery system is also discussed.