Examination of Neisseria Gonorrhoeae Opacity Protein Expression During Experimental Murine Genital Tract Infection

The opacity (Opa) proteins of Neisseria gonorrhoeae are a family of phasevariable outer membrane proteins that bind to host cells. Phase variable expression occurs via a reversible frameshift mechanism within each opa gene. Opa protein expression is selected for, or induced during experimental genital tract infection of female mice, similar to that which was reported in male volunteers. Using a genetically marked strain of FA1090 to follow recovery of a specific population of Opa variants during murine infection, here we showed that selection of a pre-existing population of Opa-positive gonococci present in the inoculum was responsible for the reisolation of mainly Opa-positive variants early during infection. We conclude that the preferential recovery of Opa-positive gonococci observed early during murine infection is due to selection of a pre-existing population of Opa-positive variants caused by factors other than binding to human CEACAM receptors. In long-term infection of mice, a cyclical pattern of Opa protein expression was observed in which a decreased recovery of Opapositive variants followed early selection for Opa protein expression; reemergence of Opa-positive gonococci occurred later in infection. The original document contains color images.