Immunohistochemistry of the nasal cavity-associated lymphoid tissue in the dolphin (Stenella coeruleoalba, Meyen 1833)

The striped dolphin (Stenella coeruleoalba) is a medium-sized pelagic dolphin with a single external nasal opening (blowhole) located in the rostral and dorsal regions of the skull. The nasal cavity is divided into three sections: the olfactory, respiratory, and vestibular areas. The surface epithelium lining the regio vestibularis is the first tissue in the nose to be directly affected by environmental antigens. Cetaceans have a significant amount of mucosa-associated lymphoid tissue (MALT) located throughout their bodies. The lymphoid tissue found in the nasal mucosa is known as nose- or nasopharynx-associated lymphoid tissue (NALT). NALT has not yet been studied in dolphins, but it has been identified and documented in humans and laboratory rodents. This study utilized toll-like receptor 2 (TLR2), CD4, Langerin/CD207, and inducible nitric oxide synthase to characterize, for the first time, immune cells in the mucosal regio vestibularis of the S. coeruleoalba nasal cavity using confocal microscopy immunofluorescence techniques. The findings revealed scattered immune cells immunoreactive to the tested antibodies, present in both the epithelial tissue lining the nasal cavity vestibulum and the underlying connective tissue. This study enhances our comprehension of the immune system of cetaceans. RESEARCH HIGHLIGHTS: This study provides new insights into NALT in S. coeruleoalba. This research deepens the knowledge of the skin of cetaceans.

Pandemic H1N1 influenza virus triggers a strong T helper cell response in human nasopharynx-associated lymphoid tissues

The pH1N1 belongs to influenza A family that is sometimes transmitted to humans via contact with pigs. Human tonsillar immune cells are widely used as in vitro models to study responses to influenza viruses. In the current study, human memory (M) and naïve (N) T cells responses in mononuclear cells of tonsil (TMCs) and peripheral blood (PBMCs) were stimulated by pH1N1/sH1N1, and then stained for estimation of T cells proliferation index. Individuals with an anti-pH1N1 hemagglutination (HA) inhibition (HAI) titer of forty or greater exhibited stronger HA-specific M-CD4+ T cells responses to pH1N1 in TMCs/PBMCs than those with an HAI titer of less than forty (P < 0.01). In addition, a positive correlation was observed between proliferation indices of M-CD4+ T cells induced by exposure to sH1N1/pH1N1 (p < 0.01). Moreover, a strong correlation (p < 0.001) was detected between subjects' age and their HA-specific M-CD4+ T cells induced by pH1N1 exposure, indicating that this response was age-dependent. Finally, stimulation of TMCs with pH1N1-HA resulted in a significant M-CD8+ T cells response (p < 0.05). In conclusion, pH1N1 HA elicits a strong M-CD4+ T cells response in TMCs. Additionally, this response correlates with the response to sH1N1 suggesting cross-reactivity in T cells epitopes directed against HAs of both viral strains.

Live attenuated influenza vaccine induces broadly cross-reactive mucosal antibody responses to different influenza strains in tonsils

Intranasal live attenuated influenza vaccine (LAIV) was used to stimulate tonsillar monocular cells (MNCs) following isolation. Haemagglutinin (HA) proteins of several influenza strains were used for the detection of HA-specific IgG, IgM and IgA antibodies using ELISA. Significant anti-sH1N1 HA IgG IgA and IgM antibody titres were detected in cell culture supernatants after stimulation (mean ± SE: 0.43 ± 0.09, mean ± SE: 0.23 ± 0.04 and mean ± SE: 0.47 ± 0.05 respectively, p < 0.01). LAIV stimulation of tonsillar MNCs induced significant IgG, IgA and IgM antibodies to the pH1N1 HA (mean ± SE:1.35 ± 0.12), (mean ± SE: 0.35 ± 0.06) and (mean ± SE: 0.58 ± 0.10) respectively, p < 0.01. Surprisingly, LAIV was shown to induce cross-reactive anti-aH5N1 HA antibodies (mean ± SE: 0.84 ± 0.20, p < 0.01) to avian influenza virus (aH5N1). Anti-H2N2 HA IgG antibody was also detected in the cell culture supernatants in a significant level after LAIV stimulation (mean ± SE: 0.93 ± 0.23, p < 0.01). High levels of anti-sH3N2 HA IgG antibody was discovered after LAIV stimulation of tonsillar MNCs, (mean ± SE: 1.2 ± 0.23p < 0.01). The current model of human nasal-associated lymphoid tissue (NALT) to evaluate B cells responses to LAIV was evident that it is a successful model to study future intranasal vaccines.

In vivo tracing of immunostimulatory raw starch microparticles after mucosal administration

Raw starch microparticles (SMPs) proved efficient antigen carriers with adjuvant properties when administered via the mucosal route; however, the underlying mechanisms associated with this bioactivity are unknown. In the present study, we explored the mucoadhesion properties, fate, and toxicity of starch microparticles after mucosal administration. Nasally administered microparticles were mainly retained in nasal turbinates, reaching the nasal-associated lymphoid tissue; this step is facilitated by the ability of the microparticles to penetrate through the mucous epithelium. Likewise, we found intraduodenally administered SMPs on the small intestinal villi, follicle-associated epithelium, and Peyer's patches. Furthermore, under simulated gastric and intestinal pH conditions, we detected mucoadhesion between the SMPs and mucins, regardless of microparticle swelling. SMPs' mucoadhesion and translocation to mucosal immune responses induction sites explain the previously reported role of these microparticles as vaccine adjuvants and immunostimulants.

Intranasal trans-sialidase-based vaccine against Trypanosoma cruzi triggers a mixed cytokine profile in the nasopharynx-associated lymphoid tissue and confers local and systemic immunogenicity

Trypanosoma cruzi, the agent of Chagas disease, can infect through conjunctive or oral mucosas. Therefore, the induction of mucosal immunity by vaccination is relevant not only to trigger local protection but also to stimulate both humoral and cell-mediated responses in systemic sites to control parasite dissemination. In a previous study, we demonstrated that a nasal vaccine based on a Trans-sialidase (TS) fragment plus the mucosal STING agonist c-di-AMP, was highly immunogenic and elicited prophylactic capacity. However, the immune profile induced by TS-based nasal vaccines at the nasopharyngeal-associated lymphoid tissue (NALT), the target site of nasal immunization, remains unknown. Hence, we analyzed the NALT cytokine expression generated by a TS-based vaccine plus c-di-AMP (TSdA+c-di-AMP) and their association with mucosal and systemic immunogenicity. The vaccine was administered intranasally, in 3 doses separated by 15 days each other. Control groups received TSdA, c-di-AMP, or the vehicle in a similar schedule. We demonstrated that female BALB/c mice immunized intranasally with TSdA+c-di-AMP boosted NALT expression of IFN-γ and IL-6, as well as IFN-β and TGF-β. TSdA+c-di-AMP increased TSdA-specific IgA secretion in the nasal passages and also in the distal intestinal mucosa. Moreover, T and B-lymphocytes from NALT-draining cervical lymph nodes and spleen showed an intense proliferation after ex-vivo stimulation with TSdA. Intranasal administration of TSdA+c-di-AMP provokes an enhancement of TSdA-specific IgG_2a and IgG₁ plasma antibodies, accompanied by an increase IgG_2a/IgG₁ ratio, indicative of a Th1-biased profile. In addition, immune plasma derived from TSdA+c-di-AMP vaccinated mice exhibit in-vivo and ex-vivo protective capacity. Lastly, TSdA+c-di-AMP nasal vaccine also promotes intense footpad swelling after local TSdA challenge. Our data support that TSdA+c-di-AMP nasal vaccine triggers a NALT mixed pattern of cytokines that were clearly associated with an evident mucosal and systemic immunogenicity. These data are useful for further understanding the immune responses elicited by the NALT following intranasal immunization and the rational design of TS-based vaccination strategies for prophylaxis against T. cruzi.

Particle Nanoarchitectonics for Nanomedicine and Nanotherapeutic Drugs with Special Emphasis on Nasal Drugs and Aging

Aging is a multifunctional physiological manifestation. The nasal cavity is considered a major site for easy and cost-effective drug and vaccine administration, due to high permeability, low enzymatic activity, and the presence of a high number of immunocompetent cells. This review article primarily focuses on aging genetics, physical parameters, and the use of nanoparticles as delivery systems of drugs and vaccines via the nasal cavity. Studies have identified various genes involved in centenarian and average-aged people. VEGF is a key mediator involved in angiogenesis. Different therapeutic approaches induce vascular function and angiogenesis. FOLR1 gene codes for folate receptor alpha protein that helps in regulating the transport of vitamin B folate, 5-methyltetrahydrofolate and folate analogs inside the cell. This gene also aids in slowing the aging process down by cellular regeneration and promotes healthy aging by reducing aging symptoms. It has been found through the literature that GATA 6, Yamanaka factors, and FOLR1 work in synchronization to induce healthy and delayed aging. The role and applications of genes including CBS, CISD, SIRT 1, and SIRT 6 play a significant role in aging.

Vaccination Route Determines the Kinetics and Magnitude of Nasal Innate Immune Responses in Rainbow Trout (Oncorhynchus mykiss)

Simple Summary

Many pathogens exploit the olfactory route to reach critical organs in the body such as the brain or lungs. Thus, effective onset of an early innate immune response in the nasal epithelium is key to stopping pathogen progression. The stimulation of nasal immunity by vaccines may depend on the type of vaccine and vaccination route. The goal of this study was to evaluate the ability of a live attenuated viral vaccine to stimulate innate immunity in the olfactory organ of rainbow trout, a teleost fish of commercial aquaculture value. The kinetics and magnitude of the innate immune response depended on the route of vaccination, with the strongest and fastest responses recorded in intranasally vaccinated fish. Injection vaccination had an intermediate effect, whereas immersion vaccination resulted in delayed and weak nasal innate immunity. Injection vaccination, even with the vehicle control, induced mortality in fingerlings, whereas nasal and immersion vaccines were safe. Challenge experiments with the live virus revealed that nasal and injected vaccines conferred very high and comparable levels of protection, but immersion vaccination only induced transient protection. In conclusion, the route of vaccination determines the type, magnitude and velocity of the innate immune response in the nasal epithelium of animals.

Abstract

Many pathogens infect animal hosts via the nasal route. Thus, understanding how vaccination stimulates early nasal immune responses is critical for animal and human health. Vaccination is the most effective method to prevent disease outbreaks in farmed fish. Nasal vaccination induces strong innate and adaptive immune responses in rainbow trout and was shown to be highly effective against infectious hematopoietic necrosis (IHN). However, direct comparisons between intranasal, injection and immersion vaccination routes have not been conducted in any fish species. Moreover, whether injection or immersion routes induce nasal innate immune responses is unknown. The goal of this study is to compare the effects of three different vaccine delivery routes, including intranasal (IN), intramuscular (i.m.) injection and immersion (imm) routes on the trout nasal innate immune response. Expression analyses of 13 immune-related genes in trout nasopharynx-associated lymphoid tissue (NALT), detected significant changes in immune expression in all genes analyzed in response to the three vaccination routes. However, nasal vaccination induced the strongest and fastest changes in innate immune gene expression compared to the other two routes. Challenge experiments 7 days post-vaccination (dpv) show the highest survival rates in the IN- and imm-vaccinated groups. However, survival rates in the imm group were significantly lower than the IN- and i.m.-vaccinated groups 28 dpv. Our results confirm that nasal vaccination of rainbow trout with live attenuated IHNV is highly effective and that the protection conferred by immersion vaccination is transient. These results also demonstrate for the first time that immersion vaccines stimulate NALT immune responses in salmonids.

Fish nasal immunity: From mucosal vaccines to neuroimmunology

Like terrestrial vertebrates, bony fishes have a nasopharynx-associated lymphoid tissue (NALT) that protects the host against invading pathogens. Despite nasal immunity being a relatively new field in fish immunology, the investigation of nasal immune systems has already illuminated fundamental aspects of teleost mucosal immune systems as well as neuroimmunology. In this review, we highlight the importance of nasal infections in bony fish and the progress that has been made towards understanding how fish respond locally and systemically to nasal infection or vaccination. We also want to highlight the complex interactions between neurons and immune cells that occur in the olfactory organ during the course of an immune response. We predict that similar neuroimmune interactions govern immune responses at all mucosal tissues in bony fish. Understanding the principles of mucosal immune responses in teleost NALT has therefore revealed important aspects of fish mucosal immunity that are critical for mucosal vaccination in aquaculture.

Impaired mucociliary motility enhances antigen-specific nasal IgA immune responses to a cholera toxin-based nasal vaccine

Nasal mucosal tissues are equipped with physical barriers, mucus and cilia, on their surface. The mucus layer captures inhaled materials, and the cilia remove the inhaled materials from the epithelial layer by asymmetrical beating. The effect of nasal physical barriers on the vaccine efficacy remains to be investigated. Tubulin tyrosine ligase-like family, member 1 (Ttll1) is an essential enzyme for appropriate movement of the cilia on respiratory epithelium, and its deficiency (Ttll1-KO) leads to mucus accumulation in the nasal cavity. Here, when mice were intra-nasally immunized with pneumococcal surface protein A (PspA, as vaccine antigen) together with cholera toxin (CT, as mucosal adjuvant), Ttll1-KO mice showed higher levels of PspA-specific IgA in the nasal wash and increased numbers of PspA-specific IgA-producing plasma cells in the nasal passages when compared with Ttll1 hetero (He) mice. Mucus removal by N-acetylcysteine did not affect the enhanced immune responses in Ttll1-KO mice versus Ttll1-He mice. Immunohistological and flow cytometry analyses revealed that retention time of PspA in the nasal cavity in Ttll1-KO mice was longer than that in Ttll1-He mice. Consistently, uptake of PspA by dendritic cells was higher in the nasopharynx-associated lymphoid tissue (NALT) of Ttll1-KO mice than that of Ttll1-He mice. These results indicate that the ciliary function of removing vaccine antigen from the NALT epithelial layer is a critical determinant of the efficacy of nasal vaccine.

CD4+ T cells induce productions of IL-5 and IL-13 through MHCII on ILC2s in a murine model of allergic rhinitis

OBJECTIVE

CD4⁺ T cells play an important role not only in the induction of allergy but also in allergic inflammation. Group 2 innate lymphoid cells (ILC2s) also mediate type 2 immune responses in allergic rhinitis (AR). However, the relationships between CD4⁺ T cells and ILC2s in allergic condition are currently not well defined. The study aimed to evaluate the potential influences of CD4⁺ T cells on ILC2s in the murine model of AR.

METHODS

A murine model of AR was established using ovalbumin (OVA), and OVA-induced ILC2s were sorted and purified from the mouse nasal-associated lymphoid tissue (NALT), and cultured in vitro. Then, the expression of major histocompatibility complex class II (MHCII) on ILC2s was examined. CD4⁺ T cells were separated from AR mice peripheral blood mononuclear cells (PBMCs). After that, productions of IL-5 and IL-13 on ILC2s cultures were assessed when CD4⁺ T cells or plus anti-MHCII antibody or anti-CD4 antibody were administered into the cultures. Finally, we adoptively transferred ILC2s alone or ILC2s plus anti-MHCII antibody to the murine model of AR to investigate their roles in the nasal allergic inflammation.

RESULTS

We showed that ILC2s could be induced by OVA in the mouse NALT. The number and percentage of ILC2s in AR mice were increased. MHCII was expressed on ILC2s, and its protein and mRNA were all enhanced in allergic condition. IL-5 and IL-13 proteins and mRNAs were elevated after CD4⁺ T cells administration, and were reduced after these cells plus anti-MHCII antibody or anti-CD4 antibody application. Numbers of sneezing and nasal rubbing as well as counts of eosinophils in nasal lavage fluid (NLF) were all enhanced after the adoptive transfer of ILC2s when compared to AR mice. IL-5 and IL-13 in the NLF of allergic mice were also increased in comparison with AR group. However, above parameters were all decreased after the transfer of ILC2s plus anti-MHCII antibody versus AR mice or ILC2s-treated ones.

CONCLUSION

These findings show that CD4⁺ T cells induce productions of IL-5 and IL-13 through MHCII on ILC2s in AR mice models.

Comparative models for human nasal infections and immunity

The human olfactory system is a mucosal surface and a major portal of entry for respiratory and neurotropic pathogens into the body. Understanding how the human nasopharynx-associated lymphoid tissue (NALT) halts the progression of pathogens into the lower respiratory tract or the central nervous system is key for developing effective cures. Although traditionally mice have been used as the gold-standard model for the study of human nasal diseases, mouse models present important caveats due to major anatomical and functional differences of the human and murine olfactory system and NALT. We summarize the NALT anatomy of different animal groups that have thus far been used to study host-pathogen interactions at the olfactory mucosa and to test nasal vaccines. The goal of this review is to highlight the strengths and limitations of each animal model of nasal immunity and to identify the areas of research that require further investigation to advance human health.

Tailoring Formulations for Intranasal Nose-to-Brain Delivery: A Review on Architecture, Physico-Chemical Characteristics and Mucociliary Clearance of the Nasal Olfactory Mucosa

The blood-brain barrier and the blood-cerebrospinal fluid barrier are major obstacles in central nervous system (CNS) drug delivery, since they block most molecules from entering the brain. Alternative drug delivery routes like intraparenchymal or intrathecal are invasive methods with a remaining risk of infections. In contrast, nose-to-brain delivery is a minimally invasive drug administration pathway, which bypasses the blood-brain barrier as the drug is directed from the nasal cavity to the brain. In particular, the skull base located at the roof of the nasal cavity is in close vicinity to the CNS. This area is covered with olfactory mucosa. To design and tailor suitable formulations for nose-to-brain drug delivery, the architecture, structure and physico-chemical characteristics of the mucosa are important criteria. Hence, here we review the state-of-the-art knowledge about the characteristics of the nasal and, in particular, the olfactory mucosa needed for a rational design of intranasal formulations and dosage forms. Also, the information is suitable for the development of systemic or local intranasal drug delivery as well as for intranasal vaccinations.

Allogenic Fc Domain-Facilitated Uptake of IgG in Nasal Lamina Propria: Friend or Foe for Intranasal CNS Delivery?

Background: The use of therapeutic antibodies for the treatment of neurological diseases is of increasing interest. Nose-to-brain drug delivery is one strategy to bypass the blood brain barrier. The neonatal Fc receptor (FcRn) plays an important role in transepithelial transcytosis of immunoglobulin G (IgG). Recently, the presence of the FcRn was observed in nasal respiratory mucosa. The aim of the present study was to determine the presence of functional FcRn in olfactory mucosa and to evaluate its role in drug delivery. Methods: Immunoreactivity and messenger RNA (mRNA) expression of FcRn was determined in ex vivo porcine olfactory mucosa. Uptake of IgG was performed in a side-by-side cell and analysed by immunofluorescence. Results: FcRn was found in epithelial and basal cells of the olfactory epithelium as well as in glands, cavernous bodies and blood vessels. Allogenic porcine IgGs were found time-dependently in the lamina propria and along axonal bundles, while only small amounts of xenogenic human IgGs were detected. Interestingly, lymphoid follicles were spared from allogenic IgGs. Conclusion: Fc-mediated transport of IgG across the nasal epithelial barrier may have significant potential for intranasal delivery, but the relevance of immune interaction in lymphoid follicles must be clarified to avoid immunogenicity.

Activation and Induction of Antigen-Specific T Follicular Helper Cells Play a Critical Role in Live-Attenuated Influenza Vaccine-Induced Human Mucosal Anti-influenza Antibody Response

There is increasing interest recently in developing intranasal vaccines against respiratory tract infections. The antibody response is critical for vaccine-induced protection, and T follicular helper cells (T_FH) are considered important for mediating the antibody response. Most data supporting the role for T_FH in the antibody response are from animal studies, and direct evidence from humans is limited, apart from the presence of T_FH-like cells in blood. We studied the activation and induction of T_FH and their role in the anti-influenza antibody response induced by a live-attenuated influenza vaccine (LAIV) in human nasopharynx-associated lymphoid tissue (NALT). T_FH activation in adenotonsillar tissues was analyzed by flow cytometry, and anti-hemagglutinin (anti-HA) antibodies were examined following LAIV stimulation of tonsillar mononuclear cells (MNC). Induction of antigen-specific T_FH by LAIV was studied by flow cytometry analysis of induced T_FH and CD154 expression. LAIV induced T_FH proliferation, which correlated with anti-HA antibody production, and T_FH were shown to be critical for the antibody response. Induction of T_FH from naive T cells by LAIV was shown in newly induced T_FH expressing BCL6 and CD21, followed by the detection of anti-HA antibodies. Antigen specificity of LAIV-induced T_FH was demonstrated by expression of the antigen-specific T cell activation marker CD154 upon challenge by H1N1 virus antigen or HA. LAIV-induced T_FH differentiation was inhibited by BCL6, interleukin-21 (IL-21), ICOS, and CD40 signaling blocking, and that diminished anti-HA antibody production. In conclusion, we demonstrated the induction by LAIV of antigen-specific T_FH in human NALT that provide critical support for the anti-influenza antibody response. Promoting antigen-specific T_FH in NALT by use of intranasal vaccines may provide an effective vaccination strategy against respiratory infections in humans.

IMPORTANCE Airway infections, such as influenza, are common in humans. Intranasal vaccination has been considered a biologically relevant and effective way of immunization against airway infection. The vaccine-induced antibody response is crucial for protection against infection. Recent data from animal studies suggest that one type of T cells, T_FH, are important for the antibody response. However, data on whether T_FH-mediated help for antibody production operates in humans are limited due to the lack of access to human immune tissue containing T_FH. In this study, we demonstrate the induction of T_FH in human immune tissue, providing critical support for the anti-influenza antibody response, by use of an intranasal influenza vaccine. Our findings provide direct evidence that T_FH play a critical role in vaccine-induced immunity in humans and suggest a novel strategy for promoting such cells by use of intranasal vaccines against respiratory infections.

Colonization-induced protection against invasive pneumococcal disease in mice is independent of CD103 driven adaptive immune responses

Nasopharyngeal colonization with Streptococcus pneumoniae (the pneumococcus) is known to mount protective adaptive immune responses in rodents and humans. However, the cellular response of the nasopharyngeal compartment to pneumococcal colonization and its importance for the ensuing adaptive immune response is only partially defined. Here we show that nasopharyngeal colonization with S. pneumoniae triggered substantial expansion of both integrin αE (CD103) positive dendritic cells (DC) and T lymphocytes in nasopharynx, nasal-associated lymphoid tissue (NALT) and cervical lymph nodes (CLN) of WT mice. However, nasopharyngeal de-colonization and pneumococcus-specific antibody responses were similar between WT and CD103 KO mice or Batf3 KO mice. Also, naïve WT mice passively immunized with antiserum from previously colonized WT and CD103 KO mice were similarly protected against invasive pneumococcal disease (IPD). In summary, the data show that CD103 is dispensable for pneumococcal colonization-induced adaptive immune responses in mice.

Co-localization of lymphoid aggregates and lymphatic networks in nose- (NALT) and lacrimal duct-associated lymphoid tissue (LDALT) of mice

Background

The lymphatic vascular pattern in the head of mice has rarely been studied, due to problems of sectioning and immunostaining of complex bony structures. Therefore, the association of head lymphoid tissues with the lymphatics has remained unknown although the mouse is the most often used species in immunology.

Results

Here, we studied the association of nasal and nasolacrimal duct lymphatics with lymphoid aggregates in 14-day-old and 2-month-old mice. We performed paraffin sectioning of whole, decalcified heads, and immunostaining with the lymphatic endothelial cell-specific antibodies Lyve-1 and Podoplanin. Most parts of the nasal mucous membrane do not contain any lymphatics. Only the region of the inferior turbinates contains lymphatic networks, which are connected to those of the palatine. Nose-associated lymphoid tissue (NALT) is restricted to the basal parts of the nose, which contain lymphatics. NALT is continued occipitally and can be found at both sides along the sphenoidal sinus, again in close association with lymphatic networks. Nasal lymphatics are connected to those of the ocular region via a lymphatic network along the nasolacrimal duct (NLD). By this means, lacrimal duct-associated lymphoid tissue (LDALT) has a dense supply with lymphatics.

Conclusions

NALT and LDALT play a key role in the immune system of the mouse head, where they function as primary recognition sites for antigens. Using the dense lymphatic networks along the NLD described in this study, these antigens reach lymphatics near the palatine and are further drained to lymph nodes of the head and neck region.

NALT and LDALT develop in immediate vicinity of lymphatic vessels. Therefore, we suggest a causative connection of lymphatic vessels and the development of lymphoid tissues.

Naegleria fowleri immunization modifies lymphocytes and APC of nasal mucosa

We investigated whether intranasal immunization with amoebic lysates plus cholera toxin modified the populations of T and B lymphocytes, macrophages and dendritic cells by flow cytometry from nose-associated lymphoid tissue (NALT), cervical lymph nodes (CN), nasal passages (NP) and spleen (SP). In all immunized groups, the percentage of CD4 was higher than CD8 cells. CD45 was increased in B cells from mice immunized. We observed IgA antibody-forming cell (IgA-AFC) response, mainly in NALT and NP. Macrophages from NP and CN expressed the highest levels of CD80 and CD86 in N. fowleri lysates with either CT or CT alone immunized mice, whereas dendritic cells expressed high levels of CD80 and CD86 in all compartment from immunized mice. These were lower than those expressed by macrophages. Only in SP from CT-immunized mice, these costimulatory molecules were increased. These results suggest that N. fowleri and CT antigens are taking by APCs, and therefore, protective immunity depends on interactions between APCs and T cells from NP and CN. Consequently, CD4 cells stimulate the differentiation from B lymphocytes to AFC IgA-positive; antibody that we previously found interacting with trophozoites in the nasal lumen avoiding the N. fowleri attachment to nasal epithelium.

cGAMP Promotes Germinal Center Formation and Production of IgA in Nasal-Associated Lymphoid Tissue

Induction of immunoglobulin (Ig) A in the mucosa of the upper respiratory tract and the nasal cavity protects against influenza virus infection. Cyclic dinucleotides (CDNs) are used as mucosal adjuvants to enhance the immunogenicity of intranasal influenza hemagglutinin (HA) vaccines. The adjuvant activity of 2'3' cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) on Ig production was investigated in nasal-associated lymphoid tissue (NALT), serum of wild-type C57BL/6J, and stimulator of interferon genes (STING)-deficient mice, which do not recognize cGAMP. Mice were vaccinated intranasally with a HA vaccine with or without the cGAMP adjuvant. IgA and IgG production, T-cell responses, germinal center formation, and cytokine expression in NALT were assayed. cGAMP enhanced IgA and IgG production, and promoted T-cell responses. Intranasal administration of cGAMP activated both NALT and systemic immune cells, induced a favorable cytokine environment for IgA induction, and promoted germinal center formation. The cGAMP effect was STING-dependent. Taken together, cGAMP as an HA vaccine adjuvant promoted a STING-dependent NALT environment suitable for the enhancement of IgA production.

Intranasal immunization with dry powder vaccines

Vaccination represents a cost-effective weapon for disease prevention and has proven to dramatically reduce the incidences of several diseases that once were responsible for significant mortality and morbidity worldwide. The nasal cavity constitutes the initial stage of the respiratory system and the first contact with inhaled pathogens. The intranasal (IN) route for vaccine administration is an attractive alternative to injection, due to the ease of administration as well as better patient compliance. Many published studies have demonstrated the safety and effectiveness of IN immunization with liquid vaccines. Currently, two liquid IN vaccines are available and both contain live attenuated influenza viruses. FluMist® was approved in 2003 in the United States, and Nasovac® H1N1 vaccine was approved in India in 2010. Preclinical studies showed that IN immunization with dry powder vaccines (DPVs) is feasible. Although there is not a commercially available DPV yet, DPVs have the inherent advantage of being relatively more stable than liquid vaccines. This review focuses on recent developments of DPVs as next-generation IN vaccines.

Murine models for mucosal tolerance in allergy

Immunity is established by a fine balance to discriminate between self and non-self. In addition, mucosal surfaces have the unique ability to establish and maintain a state of tolerance also against non-self constituents such as those represented by the large numbers of commensals populating mucosal surfaces and food-derived or air-borne antigens. Recent years have seen a dramatic expansion in our understanding of the basic mechanisms and the involved cellular and molecular players orchestrating mucosal tolerance. As a direct outgrowth, promising prophylactic and therapeutic models for mucosal tolerance induction against usually innocuous antigens (derived from food and aeroallergen sources) have been developed. A major theme in the past years was the introduction of improved formulations and novel adjuvants into such allergy vaccines. This review article describes basic mechanisms of mucosal tolerance induction and contrasts the peculiarities but also the interdependence of the gut and respiratory tract associated lymphoid tissues in that context. Particular emphasis is put on delineating the current prophylactic and therapeutic strategies to study and improve mucosal tolerance induction in allergy.

Nasal nanovaccines

Nasal administration of vaccines is convenient for the potential stimulation of mucosal and systemic immune protection. Moreover the easy accessibility of the intranasal route renders it optimal for pandemic vaccination. Nanoparticles have been identified as ideal delivery systems and adjuvants for vaccine application. Heterogeneous protocols have been used for animal studies. This complicates the understanding of the formulation influence on the immune response and the comparison of the different nanoparticles approaches developed. Moreover anatomical and immunological differences between rodents and humans provide an additional hurdle in the rational development of nasal nanovaccines. This review will give a comprehensive expertise of the state of the art in nasal nanovaccines in animals and humans focusing on the nanomaterial used.

Cytokine profile of NALT during acute stress and its possible effect on IgA secretion

Stress stimuli affect the immune system responses that occur at mucosal membranes, particularly IgA secretion. It has been suggested that acute stress increases the levels of IgA and that sympathetic innervation plays an important role in this process. We herein explore in a murine model how acute stress affects the Th1/Th2/Treg cytokine balance in NALT, and the possible role of glucocorticoids in this effect. Nine-week-old male CD1 mice were divided into three groups: unstressed (control), stressed (subjected to 4h of immobilization), and stressed after pretreatment with a single dose of the corticosterone receptor antagonist RU-486. The parameters evaluated included plasma corticosterone and epinephrine, IgA levels in nasal fluid (by ELISA), the percentage of CD19⁺B220⁺IgA⁺ lymphocytes and CD138⁺IgA⁺ plasma cells, and the mRNA expression of heavy α chain, J chain and pIgR. Moreover, the gene and protein expression of Th1 cytokines (TNFα, IL-2 and INF-γ), Th2 cytokines (IL-4 and IL-5) and Treg cytokines (IL-10 and TGFβ) were determined in nasal mucosa. The results show that acute stress generated a shift towards the dominance of an anti-inflammatory immune response (Th2 and Treg cytokines), evidenced by a significant rise in the amount of T cells that produce IL4, IL-5 and IL-10. This immune environment may favor IgA biosynthesis by CD138⁺IgA⁺ plasma cells, a process mediated mostly by glucocorticoids.

Nasopharyngeal colonization with Streptococcus pneumoniae triggers dendritic cell dependent antibody responses against invasive disease in mice

Nasopharyngeal colonization with Streptococcus pneumoniae (Spn) is an important precondition for the development of pneumococcal pneumonia. At the same time, nasopharyngeal colonization with Spn has been shown to mount adaptive immune responses against Spn in mice and humans. Cellular responses of the nasopharyngeal compartment, including the nasal-associated lymphoid tissue, to pneumococcal colonization and their importance for developing adaptive immune responses are poorly defined. We show that nasopharyngeal colonization with S. pneumoniae led to substantial expansion of dendritic cells (DCs) both in nasopharyngeal tissue and nasal-associated lymphoid tissue of mice. Depletion of DCs achieved by either diphtheria toxin (DT) treatment of chimeric zDC^+/DTR mice, or by use of FMS-like tyrosine kinase 3 ligand (Flt3L) KO mice exhibiting congenitally reduced DC pool sizes, significantly diminished antibody responses after colonization with Spn, along with impaired protective immunity against invasive pneumococcal disease. Collectively, the data show that classical DCs contribute to pneumococcal colonization induced adaptive immune responses against invasive pneumococcal disease in two different mouse models. These data may be useful for future nasopharyngeal vaccination strategies against pneumococcal diseases in humans.

Upregulated CCL28 expression in the nasal mucosa in experimental allergic rhinitis: Implication for CD4(+) memory T cell recruitment

During nasal immune responses, lymphocytes activated in the nasopharynx-associated lymphoid tissue (NALT) are thought to traffic to the nasal mucosa. Here we found a prominent infiltration of CD4(+) memory T cells into the nasal mucosa in a mouse model of allergic rhinitis. CCR3 and CCR10 mRNA was increased in the NALT, and CCR3- or CCR10-expressing CD4(+) T cells were present in the nasal mucosa. CCL28, a chemokine ligand for CCR3 and CCR10, was upregulated in nasal epithelial cells. Our results suggest that memory CD4(+) T cells traffic to the nasal mucosa in a process that may involve CCL28 and its receptors CCR3 and CCR10.

Nasal vaccination of young rainbow trout (Oncorhynchus mykiss) against infectious hematopoietic necrosis and enteric red mouth disease

Determining the earliest age at which farmed fish can be successfully vaccinated is a very important question for fish farmers. Nasal vaccines are novel mucosal vaccines that prevent aquatic infectious diseases of finfish. The present study investigates the ontogeny of the olfactory organ of rainbow trout by histology and aims to establish the earliest age for vaccination against infectious hematopoietic necrosis (IHN) and enteric red mouth (ERM) disease using the nasal route. Rainbow trout (Oncorhynchus mykiss) were vaccinated intranasally (I.N) at three different ages: 1050° days (DD) (group A); 450 DD (group B); and 360 DD (group C), or 70, 30 and 24 days post-hatch (dph), respectively. The mean weights of groups A, B and C were 4.69 g, 2.9 g and 2.37 g, respectively. Fish received either a live attenuated IHN virus vaccine, ERM formalin killed bacterin or saline (mock vaccinated). Fish were challenged to the corresponding live pathogen 28 days post-vaccination. IHN vaccine delivery at 360 DD resulted in 40% mortality likely due to residual virulence of the vaccine. No mortality was observed in the ERM nasal delivery groups. Following challenge, very high protection rates against IHN virus were recorded in all three age groups with survivals of 95%, 100% and 97.5% in groups A, B and C, respectively. Survival against ERM was 82.5%, 87.5% and 77.5% in groups A, B and C, respectively. Survival rates did not differ among ages for either vaccine. Our results indicate the feasibility and effectiveness of nasal vaccination as early as 360 DD and vaccination-related mortalities when a live attenuated viral vaccine was used in the youngest fish.

The evolution of nasal immune systems in vertebrates

The olfactory organs of vertebrates are not only extraordinary chemosensory organs but also a powerful defense system against infection. Nasopharynx-associated lymphoid tissue (NALT) has been traditionally considered as the first line of defense against inhaled antigens in birds and mammals. Novel work in early vertebrates such as teleost fish has expanded our view of nasal immune systems, now recognized to fight both water-borne and air-borne pathogens reaching the olfactory epithelium. Like other mucosa-associated lymphoid tissues (MALT), NALT of birds and mammals is composed of organized lymphoid tissue (O-NALT) (i.e., tonsils) as well as a diffuse network of immune cells, known as diffuse NALT (D-NALT). In teleosts, only D-NALT is present and shares most of the canonical features of other teleost MALT. This review focuses on the evolution of NALT in vertebrates with an emphasis on the most recent findings in teleosts and lungfish. Whereas teleost are currently the most ancient group where NALT has been found, lungfish appear to be the earliest group to have evolved primitive O-NALT structures.

Activation of innate immunity by bacterial ligands of toll-like receptors

Tγδ and B1 lymphocytes are essential components of the mucosal immune system, activated directly by different bacterial and viral ligands without additional costimulatory signals and preprocessing of other immune effectors. This ability enables the immune system to provide rapid protection against pathogens and contributes to the decoding mechanism of the sensitizing activity of mucosal antigens. The early interaction of these cells results in the production of antibodies of immunoglobulin M (IgM) and IgA isotypes, but not immunoglobulin E (IgE). We studied the subcutaneous, intranasal, and oral delivery as three major routes of potential entry for antigens of opportunistic microorganisms, using the immunomodulator Immunovac-VP-4, which is able to activate Tγδ and B1 lymphocytes. The subcutaneous and intranasal routes produced a significant increase of these cells in lymph nodes associated with the nasal cavity (NALT) and in those associated with bronchial tissue (BALT). The oral route significantly increased levels of these cells in the spleen, in NALT, BALT, and in nodes associated with the gut (GALT). We found that mucosal application of Immunovac-VP-4, which contains antigens of conditionally pathogenic microorganisms, in conjunction with the activation of Tγδ and B1, induces adaptive immune mechanisms not only in the lymphoid formations associated with the respiratory system and with GALT, but also in the spleen [increased expression of cluster of differentiation 3 (CD3), CD4, CD8, CD19, and CD25]. This indicates that there is migration of lymphoid cells from the regional lymph nodes and mucosal lymphoid tissues via the lymph and blood to distant organs, resulting in lymphoid development, and both local and systemic immunity. Mucosal application of Immunovac-VP-4 in mice potentiates the cytotoxic activity of NK cells in the NALT, BALT, and GALT. The highest cytotoxicity was observed in cells, derived from lymphoid tissue of the intestine after oral immunization. Although we found that cytokine production was increased by all three immunization routes, it was most intensive after subcutaneous injection. Our findings confirm that there is an intensive exchange of lymphocytes not only between lymphoid formations in the mucous membranes of the respiratory tract and of GALT, but also with the spleen, which means that if effective mucosal vaccines are developed, they can induce both local and systemic immunity.

Regulation of macrophage and dendritic cell function by pathogens and through immunomodulation in the avian mucosa

Macrophages (MPh) and dendritic cells (DC) are members of the mononuclear phagocyte system. In chickens, markers to distinguish MPh from DC are lacking, but whether MPh and DC can be distinguished in humans and mice is under debate, despite the availability of numerous markers. Mucosal MPh and DC are strategically located to ingest foreign antigens, suggesting they can rapidly respond to invading pathogens. This review addresses our current understanding of DC and MPh function, the receptors expressed by MPh and DC involved in pathogen recognition, and the responses of DC and MPh against respiratory and intestinal pathogens in the chicken. Furthermore, potential opportunities are described to modulate MPh and DC responses to enhance disease resistance, highlighting modulation through nutraceuticals and vaccination.

Secretory IgA: Designed for Anti-Microbial Defense

Prevention of infections by vaccination remains a compelling goal to improve public health. Mucosal vaccines would make immunization procedures easier, be better suited for mass administration, and most efficiently induce immune exclusion - a term coined for non-inflammatory antibody shielding of internal body surfaces, mediated principally by secretory immunoglobulin A (SIgA). The exported antibodies are polymeric, mainly IgA dimers (pIgA), produced by local plasma cells (PCs) stimulated by antigens that target the mucose. SIgA was early shown to be complexed with an epithelial glycoprotein - the secretory component (SC). A common SC-dependent transport mechanism for pIgA and pentameric IgM was then proposed, implying that membrane SC acts as a receptor, now usually called the polymeric Ig receptor (pIgR). From the basolateral surface, pIg-pIgR complexes are taken up by endocytosis and then extruded into the lumen after apical cleavage of the receptor - bound SC having stabilizing and innate functions in the secretory antibodies. Mice deficient for pIgR show that this is the only receptor responsible for epithelial export of IgA and IgM. These knockout mice show a variety of defects in their mucosal defense and changes in their intestinal microbiota. In the gut, induction of B-cells occurs in gut-associated lymphoid tissue, particularly the Peyer's patches and isolated lymphoid follicles, but also in mesenteric lymph nodes. PC differentiation is accomplished in the lamina propria to which the activated memory/effector B-cells home. The airways also receive such cells from nasopharynx-associated lymphoid tissue but by different homing receptors. This compartmentalization is a challenge for mucosal vaccination, as are the mechanisms used by the mucosal immune system to discriminate between commensal symbionts (mutualism), pathobionts, and overt pathogens (elimination).