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Salmonella enterica is a major cause of morbidity worldwide and mortality in children and immunocompromised individuals in sub-Saharan Africa. Outer membrane proteins of Salmonella are of significance because they 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. We demonstrated 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 intestinal Caco-2 epithelial cells. Immunization of mice with folded, full-length, purified SadA elicited an IgG response which provided limited protection against bacterial challenge. When anti-SadA IgG titers were enhanced by administering alum-precipitated protein, a modest additional protection was afforded. Therefore, despite SadA having pleiotropic functions, it is not a dominant, protective antigen for antibody-mediated protection against Salmonella.

Original publication

DOI

10.1128/IAI.05592-11

Type

Journal article

Journal

Infect Immun

Publication Date

11/2011

Volume

79

Pages

4342 - 4352

Keywords

Adhesins, Bacterial, Alum Compounds, Animals, Bacterial Adhesion, Biofilms, Caco-2 Cells, Escherichia coli K12, Gene Expression Regulation, Bacterial, Humans, Immunoglobulin G, Membrane Proteins, Mice, Phylogeny, Salmonella typhimurium, Virulence