Abstract:

Objective To investigate specific immune responses in mice induced by recombinant major outer membrane protein （rMOMP） of C. trachomatis serovar E. Methods Thirty-six female BALB/c mice aged 3 to 4 weeks were divided into three groups, i.e., adjuvant group vaccinated with purified rMOMP and Freund′s adjutant, solitary group vaccinated with rMOMP only and control group vaccinated with phosphate buffered saline （PBS）. All the mice were intramuscularly vaccinated on week 0, 2 and 4. Blood samples and vaginal washes were obtained from these mice on week 6, then, mice were challenged with elementary body （EB） of C. trachomatis serovar E at the footpad followed by the observation of delayed hypersensitivity. On week 7, mice were genitally infected with C. trachomatis EB; one week later, blood samples and vaginal washes were obtained again; six weeks later, spleen lymphocytes were isolated from the mice and stimulated by C. trachomatis or ConA followed by the detection of cell proliferation with MTT assay. In vitro neutralization assay was also performed. ELISA was used to determine the titers of Chlamydia-specific IgG antibody in sera and IgA antibody in vaginal washes, as well as the level of IFN-γ in culture supernatant of lymphocytes and sera of mice. Vaginal swabs were collected after genital challenge and subjected to C. trachomatis culture. Results The absorbance at 405 nm of Chlamydia-specific IgG antibody and proliferation index of lymphocytes were 0.641 ± 0.059 and 5.085 ± 1.291, respectively, in mice immunized with rMOMP and Freund′s adjuvant, significantly higher than those in mice immunized with rMOMP only （0.424 ± 0.015 and 3.123 ± 0.840, both P < 0.05）. The thickness of right hind footpad increased by 0.324 ± 0.054 mm and 0.272 ± 0.064 mm, respectively, in solitary group and adjuvant group, respectively, with significant difference between the two groups （P < 0.05）. A significant increase was also observed in the adjuvant group compared with the control group in the above three parameters （all P < 0.01）. Conclusion The rMOMP of C. trachomatis could efficiently induce Chlamydia-specific humoral and cellular immune responses in mice.