A multi-epitope vaccine based on Chlamydia trachomatis major outer membrane protein induces specific immunity in mice

We evaluated the immunogenicity and efficacy of a candidate vaccine comprising the major outer membrane protein (MOMP) multi-epitope of Chlamydia trachomatis. A short gene of multi-epitope derived from MOMP containing multiple T- and B-cell epitopes was artificially synthesized. The recombinant plasmid pET32a(+) containing codon optimized MOMP multi-epitope gene was constructed. Expression of the fusion protein Trx-His-MOMP multi-epitope in Escherichia coli was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blot analysis. Balb/c mice were inoculated with the purified fusion protein subcutaneously three times with 2-week intervals. Results showed that the MOMP multi-epitope elicited not only strong humoral immune responses to C. trachomatis by generating significantly high levels of specific antibodies (IgG1 and IgG2a), but also a cellular immune response by inducing robust cytotoxic T lymphocyte responses in mice. Furthermore, the MOMP multi-epitope substantially primed secretion of IFN-γ, revealing that this vaccine could induce a strong Th1 response. Finally, the mice vaccinated with the MOMP multi-epitope displayed a reduction of C. trachomatis shedding upon a chlamydial challenge and an accelerated clearance of the infected C. trachomatis. In conclusion, the MOMP multi-epitope vaccine may have the potentiality for the development of effective prophylactic and therapeutic vaccines against the C. trachomatis infection.