Mice immunized with a chlamydial extract have no increase in early protective immunity despite increased inflammation following genital infection by the mouse pneumonitis agent of Chlamydia trachomatis.

We have determined that immunization with a detergent extract of the mouse pneumonitis agent of Chlamydia trachomatis fails to induce a protective inflammatory immune response following genital infection by C. trachomatis. We demonstrated that mice immunized with the detergent extract have increased cutaneous delayed-type hypersensitivity and increased splenic T-cell proliferation in response to the chlamydial extract. After genital infection by C. trachomatis, extract-sensitized mice had significantly increased genital inflammation (P = 0.044) compared with controls. The inflammation was characterized by significantly increased eosinophils in the genitalia (P < 0.0005) and increased genital edema (P < 0.0005). However, the increased genital inflammation of extract-sensitized mice provided no increase in protection against infection (P = 0.92).