Intranasal sensitization of Japanese cedar pollen by the co-administration of low doses of cholera toxin but not its recombinant B subunit to mice.

We evaluated the effects of cholera toxin (CT) and the B subunit of cholera toxin (CTB) on the intranasal sensitization of Japanese cedar pollen (JCP) in mice. JCP suspended in phosphate-buffered saline was administered into the nostrils of mice in combination with varying doses of CT or recombinant CTB(r-CTB) once a week for 5 weeks. Antibody responses specific to sugi basic protein (SBP) were monitored by ELISA for seven weeks. The sensitization of JCP alone did not induce IgG1, IgG2b, IgG2a, IgE or IgA. In contrast, sensitization of JCP in combination with CT (JCP/CT) elicited the prominent production of SBP-specific IgG1 and low levels of IgG2b and IgG2a on Day 49. IgE production was detected only in the serum of mice which were treated with JCP/CT, and not under any other protocol. Using spleen cells from these mice, cytokine production was examined by ELISA in culture supernatants after they had been stimulated in vitro with major cedar pollen allergens, Cry j 1, Cry j 2 or SBP. Notable responses were an increase of IFN-gamma as well as IL-4 in JCP/CT-sensitized cells stimulated with Cry j 2, but not in those stimulated with Cry j 1. No significant differences were detected in IL-5 production among the experimental groups. Histopathological examination, however, showed that eosinophil infiltration was evident in the nasal mucosa of the JCP/CT-sensitized mice following challenge with JCP/CT, but weak with BSA/CT or CT alone. Thus, the immunological and histological analyses indicated that the co-administration of a low dose of CT in combination with JCP allows the induction of pollen-allergic states in mice.