Secretory IgA differentially promotes adherence of type 1-piliated Escherichia coli to immortalized vaginal epithelial cell lines

Abstract Objectives. To elucidate the factors that influence bacterial adherence to vaginal epithelium. We developed an in vitro model to examine the interaction of type 1-piliated Escherichia coli, strain HB101/p1-17, with immortalized vaginal epithelial cells (VEC) from postmenopausal donors with (patient 1) and without (patient 2) clinical histories of urinary tract infections (UTI). Methods. The VEC were incubated in microtiter plates in the presence of E. coli HB101/p1-17, and factors such as time, mannose concentration, and secretory immunoglobulin A (sIgA) concentration were assessed. After incubation, the numbers of bacteria bound per VEC were counted on a scintillation counter. Results. The E. coli adhered to the VEC and the adherence was inhibited in the presence of 100-mM mannose solution. Clinical donor UTI histories were reflected in the binding characteristics of the VEC cell lines, with cells from patient 1 having a 30% higher baseline binding capacity than cells from patient 2 and an enhanced binding response in the presence of increasing sIgA concentrations. The sIgA concentration did not affect the patient 2 cell–bacterial binding. Conclusions. These results indicate that our in vitro model is suitable for studying the factors influencing bacterial adherence to vaginal mucosa, and that after immortalization, vaginal mucosa maintains clinically relevant characteristics that can be studied. Our data suggest that E. coli adherence to vaginal mucosa from postmenopausal women susceptible to UTI is affected by intrinsic baseline bacterial binding capacity of the mucosa cells as well as by increased sIgA concentration in the women’s vaginal fluid. Increasing vaginal fluid sIgA concentration in this population may have a deleterious rather than beneficial effect.