RESUMEN
Salmonella enterica is a major cause of morbidity worldwide and mortality in children and immunocompromisedindividuals in sub-Saharan Africa. Outer membrane proteins of Salmonella are of significance becausethey are at the interface between the pathogen and the host, they can contribute to adherence, colonization, and virulence, and they are frequently targets of antibody-mediated immunity. In this study, the properties of SadA,a purported trimeric autotransporter adhesin of Salmonella enterica serovar Typhimurium, were examined. Wedemonstrated that SadA is exposed on the Salmonella cell surface in vitro and in vivo during infection of mice.Expression of SadA resulted in cell aggregation, biofilm formation, and increased adhesion to human intestinalCaco-2 epithelial cells. Immunization of mice with folded, full-length, purified SadA elicited an IgG responsewhich provided limited protection against bacterial challenge. When anti-SadA IgG titers were enhanced byadministering alum-precipitated protein, a modest additional protection was afforded. Therefore, despite SadAhaving pleiotropic functions, it is not a dominant, protective antigen for antibody-mediated protection againstSalmonella.