Background: Immunity to chlamydia is thought to rely on interferon (IFN)-gamma-secreting T helper cells type 1 (Th1) with an additional effect of secreted antibodies. A need for Th1-polarizing adjuvants in experimental chlamydia vaccines has been demonstrated, and antigen conformation has also been reported as being important for raising protective immunity.
Methods: C57BL/6 mice vaccinated with native refolded Chlamydia muridarum major outer membrane protein (MOMP) adjuvanted with either Th1-promoting cationic adjuvant formulation 1 (CAF01) or T helper cells type 2-promoting aluminum hydroxide (alum) received a genital inoculation of 1.5 x 10(5) inclusion-forming units of C. muridarum. The role played by CD4(+) T cells in MOMP/CAF01-raised immunity was investigated by depleting CD4(+) T cells in vaccinated mice, and antigen conformation dependence was evaluated by vaccination with recombinant MOMP.
Results: Mice vaccinated with MOMP/alum displayed a strong anti-MOMP humoral response with high IgG1 titers, low levels of IFN-gamma and tumor necrosis factor (TNF)-alpha, and only a slight reduction in chlamydial load. Mice vaccinated with MOMP/CAF01 displayed high titers of IgG2b, IFN-gamma, and TNF-alpha and a profoundly reduced vaginal chlamydial load, compared with control mice. The protection was CD4(+) T cell dependent and was not dependent on MOMP conformation.
Conclusion: CAF01 adjuvant facilitates a protective anti-MOMP CD4(+) T cell response independent of MOMP conformation.