CEACAM is not necessary for Neisseria gonorrhoeae to adhere to and invade female genital epithelial cells

Neisseria gonorrhoeae has a repertoire of up to 11 opacity-associated (Opa) proteins that are adhesins. Most Opa proteins adhere to CEACAM antigens an d when CEACAM molecules are present on the surface of transfected epithelia l cells their binding by Opa is thought to induce invasion of these cells b y gonococci. In this study, we investigated whether several malignant epith elial cell lines, normal cervical and fallopian tube epithelial cell cultur es, as well as normal fallopian tube tissue express several of the CEACAM m olecules, and whether gonococci use these molecules for adherence and invas ion of these female genital epithelial cells. A primary cervical cell cultu re and metastatic cervical cell line ME180 both expressed CEACAM as shown b y whole cell ELISA and flow cytometry, and increased the surface expression of total CEACAM during incubation with Opa(+) gonococci. Opa(+) gonococci both adhered to and invaded these cells; CEACAM-specific monoclonal antibod y (MAb) partially abolished this interaction. Two primary fallopian epithel ial tube cell cultures, a primary cervical cell culture and two malignant c ell lines, HEC-1-B and HeLa, did not express CEACAM nor was CEACAM mRNA pre sent. No evidence of either intracellular or secreted extracellular CEACAM was found with HEC-1-B and HeLa cells. Opa(+) gonococci both adhered to and invaded CEACAM non-expressing cells; however, Opa(+) gonococcal associatio n with these non-expressing cell lines could not be inhibited with CEACAM-s pecific MAb. These data show that CEACAM is not always expressed on female genital epithelial cells and is not essential for gonococcal adherence and invasion. However, when CEACAM is expressed, Opa(+) gonococci exploit it fo r the adherence to and invasion of these cells.