Secretory immunoglobulin A (sIgA) in saliva versus virulence proteins of enteropathogenic Escherichia coli (EPEC) in ill and colonized children

Introduction: We evaluated the presence of sIgA in saliva, versus Escherichia coli secreted proteins (Esp) related to the type III secretion system (T3SS), and its semi-quantitative concentration in children under 2 years-old (no longer breastfed) who were previously colonized or infected with enteropathogenic E. coli (EPEC). Methods: We analyzed the presence of sIgA in 40 children, who previously had positive cultures for EPEC associated (n = 17) or not associated (n = 23) with diarrhea, using the Western Blot technique versus E. coli secreted proteins: EspABCD. A semi-quantitative measurement of the reaction for each protein was made by its density peaks (OD). Results: We found sIgA versus all or some EspABCD proteins in both groups. However, the ill patients had higher concentrations of these antibodies than colonized patients. Discussion: The presence of sIgA in saliva could reflect an intestinal immune response and their levels could be related to a greater exposure and/or bacterial load.