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.Japanese cedar pollinosis ͉ peptide immunotherapy ͉ seed-specific expression

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 LLO91–99-positive memory CD8+ T cells were significantly higher at 3 and 6 wk after infection than those in non-Tg mice. The LLO91–99-positive CD8+ T cells produced IFN-γ in response to LLO91–99, 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.

IL-15, a pleiotropic cytokine, is involved in the inflammatory responses in various infectious and autoimmune diseases. We have recently constructed IL-15-transgenic (Tg) mice, which have an increased number of memory-type CD8+ T cells in the peripheral lymphoid tissues. In the present study, we found that eosinophilia and Th2-type cytokine production in the airway were severely attenuated in OVA-sensitized IL-15-Tg mice following OVA inhalation. IL-15-Tg mice preferentially developed Tc1 responses mediated by CD8+ T cells after OVA sensitization, and in vivo depletion of CD8+ T cells by anti-CD8 mAb aggravated the allergic airway inflammation in IL-15-Tg mice following OVA inhalation. Adoptive transfer of CD8+ T cells from OVA-sensitized IL-15-Tg mice into normal mice before OVA sensitization suppressed Th2 response to OVA in the normal mice. These results suggest that overexpression of IL-15 in vivo suppresses Th2-mediated-allergic airway response via induction of CD8+ T cell-mediated Tc1 response.

An extracellular polysaccharide, AC-1, produced by Acetobacter polysaccharogenes is composed of ␤-(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-␣ by macrophage cell lines in vitro. Cellulase treatment completely abolished the activity of AC-1 to induce tumor necrosis factor-␣ 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 ␤-(1,4)glucan may be useful in prevention and treatment of allergic disorders with IgE production.

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We recently constructed IL‐15 transgenic (Tg) mice using cDNA encoding a secretable isoform of the IL‐15 precursor protein under the control of an MHC class I promoter. The IL‐15 Tg mice exhibited resistance against a primary infection with Listeria monocytogenes. The numbers of memory CD8+ T cells were markedly increased in the IL‐15 Tg mice following Listeria infection accompanied by sustained IL‐15 production. The increased CD44+CD8+ T cells in the infected IL‐15 Tg mice were not specialized to recognize Listeria‐specific antigen but produced a large amount of IFN‐γ in response to bystander stimulation exogenous IL‐15 in combination with IL‐12. Furthermore, Listeria‐specific Th1 response by CD4+ T cells was significantly augmented in the IL‐15 Tg mice compared with control mice following Listeria infection. In vivo depletion of the CD8+ T cells by anti‐CD8 monoclonal antibody and adoptive transfer of the T cells from naive IL‐15 Tg mice indicated that the CD8+ T cells functioned not only to eliminate bacteria at the early stage of infection but also to promote Th1 response to L. monocytogenes. Overexpression of IL‐15 shed light on a novel role of memory CD8+ T cells in early protection and promotion of Th1 response against a primary infection with L. monocytogenes.

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NK1.1+ § g 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 J § 281 -/-mice which lack V § 14 + 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 J § 281 +/+ mice; this abrogation was accompanied by an OVA-specific Th2-dominant response. The abrogation of oral tolerance by PGE 1 was not evident in J § 281 -/-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.