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Oral immunization with chlamydial major outer membrane protein (MOMP)
H R Taylor1, J Whittum-Hudson, J Schachter
1Wilmer Institute, Johns Hopkins Hospital, Baltimore, MD 21205.
Abstract:
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.
Insights
Vaccinating monkeys with a chlamydial major outer membrane protein (MOMP) vaccine showed limited success in preventing eye infections. While reducing inflammation, the vaccine did not shorten infection duration or significantly boost antibody responses.
Area of Science:
- Immunology
- Ophthalmology
- Microbiology
Background:
- Chlamydia trachomatis causes significant ocular infections.
- Developing effective vaccines against chlamydial eye infections remains a challenge.
- Stimulating mucosal immunity is a key strategy for preventing ocular infections.
Purpose of the Study:
- To evaluate the efficacy of a purified chlamydial major outer membrane protein (MOMP) subunit vaccine in stimulating mucosal immunity.
- To assess the vaccine's effect on subsequent ocular challenge with Chlamydia trachomatis in cynomolgus monkeys.
- To determine if different immunization schedules influence protection against chlamydial eye infection.
Main Methods:
- Cynomolgus monkeys were immunized with MOMP via intraperitoneal priming and oral boosting, with or without ocular boosting, or ocular immunization alone.
- Cholera toxin was used as an adjuvant for oral MOMP doses.
- Animals were challenged with live Chlamydia trachomatis elementary bodies 35 days post-immunization.
- Immune responses were assessed using immunoblotting and microimmunofluorescence (MicroIF) serology.
Main Results:
- Vaccination transiently decreased inflammatory responses in the eye but did not reduce infection duration.
- Anti-MOMP antibodies were detected in some orally vaccinated animals via immunoblotting.
- MicroIF serology showed similar antibody responses in vaccinated and non-vaccinated animals after ocular challenge.
- No significant reduction in infection duration or severity was observed across different immunization groups.
Conclusions:
- Stimulating mucosal immunity with a purified chlamydial MOMP vaccine provided only partial protection against ocular infection.
- The immunization regimens failed to induce a robust pre-challenge antibody response, potentially explaining the limited efficacy.
- Further research is needed to develop more effective vaccination strategies against chlamydial eye infections.