Priming with Chlamydia trachomatis major outer membrane protein (MOMP) DNAfollowed by MOMP ISCOM boosting enhances protection and is associated withincreased immunoglobulin A and Th1 cellular immune responses

We previously reported that DNA vaccination was able to elicit cellular imm une responses and partial protection against Chlamydia trachomatis infectio n. However, DNA immunization alone did not generate immune responses or pro tection as great as that induced by using live organisms. In this study, we evaluated the immunologic effects of a combinational vaccination approach using C. trachomatis mouse pneumonitis (MoPn) major outer membrane protein (MOMP) DNA priming followed by boosting with immune-stimulating complexes ( ISCOM) of MOMP protein (MOMP ISCOM) for protection of BALB/c mice against M oPn lung infection. Substantially better protection to challenge infection was observed in mice given combinational vaccination compared with mice giv en MOMP ISCOM immunization alone, and the protection approximated that indu ced by live organisms, Enhanced protection was correlated with stronger del ayed-type hypersensitivity, higher levels of gamma interferon production, a nd increased immunoglobulin A antibody responses in lung homogenates, The r esults indicate that DNA priming followed by ISCOM protein boosting may be useful in designing a fully protective chlamydial vaccine.