Immunization of the gastrointestinal tract with bacterial and viral antigens: implications in mucosal immunity

The effects of oral immunization with Pseudomonas aeruginosa (PAOI), Chlamydia trachomatis or respiratory syncytial virus (RSV) on the development of specific antibody responses in the intestine, respiratory tract and genital secretions was studied in several animal models. Oral immunization resulted in the development of specific immunity in distant mucosal sites. However, its role in influencing the outcome of reinfection challenge at the distant site varied with the antigen. Little or no protection was observed against infection with Pseudomonas aeruginosa in the respiratory tract. Limited protection was observed against respiratory tract infection with RSV. On the other hand oral immunization appeared to be quite effective in preventing respiratory or genital infection with Chlamydia trachomatis. Finally, preliminary studies have suggested that intestinal immunization via the process of breast feeding can also be employed as an effective means to induce anti-idiotypic immunity against RSV in the breast feeding neonates.