Secretory
antibodies in mucosal surfaces are known to play an essential role in protection against various
infectious diseases. To enhance the production of such
antibodies,
influenza HA
vaccine was inoculated intranasally into rabbits, together with
cholera toxin B subunit (CTB) which is known to augment antibody response to an unrelated
antigen. This combination resulted in high levels of serum
IgG antibody responses against HA and CTB molecules, 3-4 weeks after inoculation, compared with the inoculation of HA
vaccine alone. The adjuvant mechanism for CTB was studied by using Ussing chambers, in which nasal mucosa from rabbits were mounted. CTB was found to enhance the transepithelial flux of HA
vaccine, from the mucosal side (lumen) into the serosal side (lamina propria), indicating that the permeability of the membrane was changed by CTB. Moreover, to achieve effective flux of HA
vaccines, some interactions between the
vaccine and CTB across the membrane were found, which may effect the effectiveness of the
vaccine formulation. The results suggest that one of the mechanisms by which CTB enhances the production of mucosal antibody response is to enhance the transepithelial influx of
vaccine into the nasal mucosa, where the cells involved in the antibody production are located. CTB may be used as a potent adjuvant to induce antibody response, by nasal vaccination, against pathogens impinging on mucosal surfaces.