Mucosal immunity of nasopharynx: an experimental study in TCR-transgenic (OVA23-3) mice.

The ideal vaccine therapy has been warranted for activation of the mucosal immune response in the upper respiratory tract against various types of microbial infection. However, the precise study in regard to the mucosal route of vaccine administration and its mechanism of action remains to be further investigated. Therefore, to better understand the exact mechanism of nasopharyngeal mucosal immunology, from T-cell aspects, the antigen-specific antibody response was investigated in T cell receptor transgenic (OVA23-3) mice (Tg-mice) and wild type BALB/c mice, in comparison, which were stimulated with repeated nasal antigen challenges of ovalbumin (OVA) together with cholera toxin (CT) or OVA alone. OVA-specific IgA and IgG antibodies were not detected in nasal washings of BALB/c mice when these mice were intranasally stimulated with OVA alone. But they were detected in those of BALB/c mice stimulated with OVA and CT, as we have already reported. Interestingly, OVA-specific IgA and IgG antibodies were significantly higher in nasal washings of Tg-mice stimulated with OVA and CT or OVA alone rather than those of BALB/c mice stimulated with OVA and CT. In line with data of the antibody response, OVA-specific IgA and IgG antibody-producing cells significantly increased in number in nasal passage (NP), nasopharyngeal-associated lymphoreticular tissue (NALT), cervical lymph node (CLN), and spleen (SP) of these mice. In nasal washings of Tg-mice, interferon (IFN)-gamma and interleukin (IL)-4 was detected even with a small amount of antigen. To see the cytokine profile of NALT, NP, CLN, and SP of these mice, various cytokine concentrations were measured in supernatants of these cells cultured in vitro with OVA. As a result, IFN-gamma was detected at significantly higher levels in culture supernatants of lymphocytes sampled from NP, CLN, SP as well as NALT of mice having increased antibody titers in nasal washings. On the other hand, Th2 type cytokines such as IL-4, IL-6 and IL-13 were efficiently detected in culture supernatants of NP, CLN, and SP cells from Tg-mice mice, but not in those from NALT cells of those mice. All these data taken together indicate that helper T cells recruited into nasal mucosa and locally activated in an antigen-specific fashion, as well as NALT T cells, are essential for mounting local antigen-specific antibody responses.

Role of interleukin-15 in the development of mouse olfactory nerve.

Interleukin (IL)-15 interacts with components of the IL-2 receptor (R) and exhibits T cell-stimulating activity similar to that of IL-2. In addition, IL-15 is widely expressed in many cell types and tissues, including the central nervous system. We provide evidence of a novel role of IL-15 in olfactory neurogenesis. Both IL-15 and IL-15R alpha were expressed in neuronal precursor cells of the developing olfactory epithelium in mice. Adult IL-15R alpha knockout mice had fewer mature olfactory neurons and proliferating cells than wild-type. Our results suggest that IL-15 plays an important role in regulating cell proliferation in olfactory neurogenesis.

Efficient induction of oral tolerance by fusing cholera toxin B subunit with allergen-specific T-cell epitopes accumulated in rice seed.

Cholera toxin B (CTB) subunit is an efficient mucosal carrier molecule for induction of oral tolerance to antigens and allergens. Here, T-cell epitopes of Cry j 1 and Cry j 2, major allergens in Japanese cedar pollen, were expressed in rice seed as a fusion protein with either CTB or rice glutelin as a control. Feeding mice with rice seed containing CTB-fused T-cell epitopes suppressed allergen-specific IgE responses and pollen-induced clinical symptoms at 50-fold lower doses of T-cell epitopes than required when using control seed. Our findings present a novel potential strategy for immunotherapy of type-I allergy.

A rice-based edible vaccine expressing multiple T cell epitopes induces oral tolerance for inhibition of Th2-mediated IgE responses.

Peptide immunotherapy using multiple predominant allergen-specific T cell epitopes is a safe and promising strategy for the control of type I allergy. In this study, we developed transgenic rice plants expressing mouse dominant T cell epitope peptides of Cry j I and Cry j II allergens of Japanese cedar pollen as a fusion protein with the soybean seed storage protein glycinin. Under the control of the rice seed storage protein glutelin GluB-1 promoter, the fusion protein was specifically expressed and accumulated in seeds at a level of 0.5% of the total seed protein. Oral feeding to mice of transgenic rice seeds expressing the T cell epitope peptides of Cry j I and Cry j II before systemic challenge with total protein of cedar pollen inhibited the development of allergen-specific serum IgE and IgG antibody and CD4(+) T cell proliferative responses. The levels of allergen-specific CD4(+) T cell-derived allergy-associated T helper 2 cytokine production of IL-4, IL-5, and IL-13 and histamine release in serum were significantly decreased. Moreover, the development of pollen-induced clinical symptoms was inhibited in our experimental sneezing mouse model. These results indicate the potential of transgenic rice seeds in production and mucosal delivery of allergen-specific T cell epitope peptides for the induction of oral tolerance to pollen allergens.

NKT cells are dispensable in the induction of oral tolerance but are indispensable in the abrogation of oral tolerance by prostaglandin E.

NK1.1(+) alpha beta T cells (NKT cells) regulate the Th1/Th2 balance in response to dietary Ag, which may be involved in regulation of oral tolerance. OVA-specific IgE and IgG(1) Ab levels were significantly lower following an i.p. injection of OVA (in CFA) in C57BL/6 mice orally given a single, high dose (25 mg) of OVA than in those orally given PBS. The oral tolerance was normally induced in Jalpha281(-/-) mice which lack Valpha14(+) NKT cells, suggesting that NKT cells are dispensable for induction of oral tolerance. Treatment with PGE(1) or PGE(2 )abrogated the oral tolerance in Jalpha281(+/+) mice; this abrogation was accompanied by an OVA-specific Th2-dominant response. The abrogation of oral tolerance by PGE(1 )was not evident in Jalpha281(-/-) mice. Treatment with PGE(1) induced an early increase in IL-4 production by liver NKT cells in normal mice and neutralization of the early IL-4 by administration of anti-IL-4 mAb abolished PGE(1)-induced abrogation of oral tolerance. These results suggest that liver NKT cells producing IL-4 are responsible for the down-regulation of oral tolerance that is caused by the PGE molecules.

Overexpression of IL-15 in vivo increases antigen-driven memory CD8+ T cells following a microbe exposure.

To elucidate potential roles of IL-15 in the maintenance of memory CD8+ T cells, we followed the fate of Ag-specific CD8+ T cells directly visualized with MHC class I tetramers coupled with listeriolysin O (LLO)(91-99) in IL-15 transgenic (Tg) mice after Listeria monocytogenes infection. The numbers of LLO(91-99)-positive memory CD8+ T cells were significantly higher at 3 and 6 wk after infection than those in non-Tg mice. The LLO(91-99)-positive CD8+ T cells produced IFN-gamma in response to LLO(91-99), and an adoptive transfer of CD8+ T cells from IL-15 Tg mice infected with L. monocytogenes conferred a higher level of resistance against L. monocytogenes in normal mice. The CD44+ CD8+ T cells from infected IL-15 Tg mice expressed the higher level of Bcl-2. Transferred CD44+ CD8+ T cells divided more vigorously in naive IL-15 Tg mice than in non-Tg mice. These results suggest that IL-15 plays an important role in long-term maintenance of Ag-specific memory CD8+ T cells following microbial exposure via promotion of cell survival and homeostatic proliferation.

Soluble branched beta-(1,4)glucans from Acetobacter species show strong activities to induce interleukin-12 in vitro and inhibit T-helper 2 cellular response with immunoglobulin E production in vivo.

An extracellular polysaccharide, AC-1, produced by Acetobacter polysaccharogenes is composed of beta-(1,4)glucan with branches of glucosyl residues. We found that AC-1 showed a strong activity to induce production of interleukin-12 P40 and tumor necrosis factor-alpha by macrophage cell lines in vitro. Cellulase treatment completely abolished the activity of AC-1 to induce tumor necrosis factor-alpha production by macrophages, whereas treatment of AC-1 with polymyxin B or proteinase did not affect the activity. Results of experiments using toll-like receptor (TLR) 4-deficient mice and TLR4-transfected human cell line indicated that TLR4 is involved in pattern recognition of AC-1. In vivo administration of AC-1 significantly reduced the serum levels of ovalbumin (OVA)-specific IgE and interleukin-4 production by T cells in response to OVA in mice immunized with OVA. AC-1, a soluble branched beta-(1,4)glucan may be useful in prevention and treatment of allergic disorders With IgE production.