Oral immunization with chlamydial major outer membrane protein (MOMP).

The effect of vaccination to stimulate mucosal immunity with a purified subunit vaccine of chlamydial major outer membrane protein (MOMP) on subsequent ocular challenge with Chlamydia trachomatis was studied in cynomolgus monkeys. Monkeys were immunized with MOMP by intraperitoneal priming plus oral boosting, with or without ocular boosting, or by ocular immunization alone. Cholera toxin was used as an adjuvant with the oral doses of MOMP vaccine. Animals were challenged with viable purified elementary bodies 35 days after the first immunization. The immunizing schedules used provided a transient decrease in the potentially deleterious inflammatory response in the eye but no reduction in duration of infection. Immunoblotting studies showed that anti-MOMP antibodies were induced by oral vaccination in some animals, but the antibody response following ocular challenge as determined by microimmunofluorescence (MicroIF) serology was similar in vaccinated and nonvaccinated animals. This study demonstrates that the stimulation of mucosal immunity by a vaccine of purified chlamydial MOMP was only partially effective in protecting against chlamydial eye infection. The lack of clear protection in these studies may be due to the failure of the various immunizing regimes to induce an antibody response prior to challenge.