Immune responses induced by the recombinant major outer membrane protein vaccine against Chlamydia trachomatis E serotype in rhesus monkeys

Abstract

[Objective] To observe the specific immune responses induced by the recombinant major outer membrane protein (rMOMP) vaccine against Chlamydia trachomatis E serotype in rhesus monkeys.[Methods] Six rhesus monkeys were equally divided into three groups:adjuvant and protein group vaccinated with purified rMOMP and Freund's adjuvants,adjuvant group immunized with Freund's adjuvants only,and control group immunized with phosphate buffer.All the rhesus monkeys were intramuscularly immunized in the triceps brachii for 3 times at a 2-week interval.Two weeks after the last vaccination,serum,vaginal wash and venous blood samples were collected from the rhesus monkeys,and lymphocytes were isolated from the blood samples.Enzyme linked immunosorbent assay (ELISA) was performed to determine the specific IgG antibody and interferon level in sera and secretory IgA (sIgA) level in wash samples,and methyl thiazolyl tetrazolium (MTT) assay to evaluate the proliferation of lymphocytes after stimulation with Chlaraydia trachomatis serotype E elementary bodies.Delayed hypersensitivity was observed in rhesus monkeys challenged by inactivated Chlamydia trachomatis serotype E elementary bodies.In vitro antibody neutralization assay was conducted with the serum from rhesus monkeys.Indirect immunofluorescenee was used to detect Chlamydia trachomatis in exfoliative vaginal cells from rhesus monkeys from week 1 to 10 after challenge with Chlamydia trachomatis.Data were statistically analyzed by using one-way analysis of variance and least significant difference (LSD) test with the SPSS 14.0 software.[Results] The adjuvant and protein group differed statistically from the adjuvant group and control group in the serum level of specific IgG antibody (1.718 ± 0.213 vs.0.841 ± 0.315 and 0.791 ±0.437,both P＜ 0.05),interferon ((1086 ± 121.730) ng/L vs.(409 + 53.440) ng/L and (162 ± 48.046) ng/L,both P＜ 0.05),lymphocyte proliferation index (7.012 ± 1.026 vs.4.473 ± 1.850 and 1A26 ± 1.104,both P＜0.01 ) and the diameter of nodus in delayed hypersensitivity assay ( ( 1 1 ± 2.134) mm vs.(3 ± 0.914) mm and 0,both P ＜ 0.01 ).After attack,the exfoliative cells kept positive for Chlamydia trachomatis in the adjuvant and protein group from week 1 to 5,and in the other 2 groups from week 1 to 10,but were negative in the adjuvant and protein group from week 6 to 10.[Conclusion] The rMOMP vaccine can induce a specific,protective,humoral and cellular immune response against Chlamydia tracbomatis in rhesus monkeys. Key words: Chlamydia trachomatis Bacterial outer membrane proteins; Vaccines; Animal experimentation