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A chlamydial major outer membrane protein extract as a trachoma vaccine candidate
1Conselho Brasileiro de Oftalmologia, Sao Paulo, Brazil.
Purpose:
As shown in infected humans and in animal models of chlamydial infection, the major outer membrane protein (MOMP) of Chlamydia trachomatis is immunogenically potent. The purpose of this investigation was to test in the cynomolgus monkey model of trachoma a new extract of MOMP as a candidate vaccine against ocular chlamydial infection.
Method:
The nonionic detergent octyl-beta-D glucopyranoside (OGP) was used to extract MOMP from purified C. trachomatis (serovar C) elementary bodies. Protective immunization with OGP-MOMP by mucosal and systemic routes was compared in the cynomolgus monkey model of trachoma. All control and immunized monkeys were challenged by topical application of infectious C. trachomatis to the conjunctivae 35 days after the initiation of immunization.
Results:
Immunization with OGP-extracted MOMP successfully induced chlamydia-specific local and systemic immunity to MOMP and to whole organism before challenge and early clearance of infection by systemically immunized monkeys. Although ocular disease was not significantly reduced in either immunized group compared to control animals, the lowest clinical and microbiologic disease scores developed in two animals in the mucosal group with the highest immunoglobulin A tear antibody titers at day 0 to 14, whereas higher tear and serum immunoglobulin G correlated with reduced disease in the systemically immunized group.
Conclusions:
These data demonstrate that despite evidence of vigorous MOMP-specific and other chlamydia-specific serologic and cell-mediated immunity, as well as anamnestic serologic responses to chlamydia, vaccination with OGP-MOMP was only partially protective against chlamydial ocular disease. The partial protection correlated best with tear immunoglobulin A responses after mucosal immunization and with local and systemic immunoglobulin G responses after peripheral immunization, suggesting that alternative chlamydial antigens may have to be considered in future vaccine development to induce more effective protective immunity and that evaluation of efficacy must be appropriate to route of immunization.
Insights
A new Chlamydia trachomatis major outer membrane protein (MOMP) vaccine showed partial protection against ocular infection in monkeys. Immunity varied by immunization route, suggesting alternative antigens may be needed for better vaccine development.
Area of Science:
- Ophthalmology
- Immunology
- Microbiology
Background:
- Chlamydia trachomatis major outer membrane protein (MOMP) is immunogenic.
- Chlamydial infections cause ocular disease and are a significant public health concern.
Purpose of the Study:
- To evaluate a novel octyl-beta-D glucopyranoside (OGP)-extracted MOMP as a candidate vaccine against ocular chlamydial infection.
- To compare mucosal and systemic immunization routes in the cynomolgus monkey model of trachoma.
Main Methods:
- MOMP was extracted from C. trachomatis elementary bodies using OGP.
- Cynomolgus monkeys were immunized via mucosal and systemic routes.
- Monkeys were challenged with C. trachomatis via topical conjunctival application.
Main Results:
- Immunization induced chlamydia-specific immunity and early infection clearance in systemically immunized monkeys.
- Ocular disease severity was not significantly reduced compared to controls.
- Partial protection correlated with specific immunoglobulin titers (IgA for mucosal, IgG for systemic).
Conclusions:
- Vaccination with OGP-MOMP provided only partial protection against chlamydial ocular disease.
- Immune responses varied by immunization route, with IgA and IgG titers correlating with protection.
- Future vaccine development may require alternative chlamydial antigens and route-specific efficacy evaluations.