Outer membrane protein a of Salmonella enterica serovar Typhimurium activates dendritic cells and enhances Th1 polarization

We purified OmpA from S. enterica serovar Typhimurium (OmpA-sal) and characterized the role of OmpA-sal in promoting adaptive and innate immune responses. OmpA-sal functionally activated bone marrow-derived dendritic cells by augmenting expression of CD80, CD86, and major histocompatibility complex classes I and II. Interestingly, OmpA-sal induced production of interferon-γ from T cells in mixed lymphocyte reactions, thus indicating Th1-polarizing capacity. The expression of surface markers and cytokine production in dendritic cells was mediated by the TLR4 signaling pathway in a TLR4 Knock-out system.Our findings suggest that OmpA-sal modulates the adaptive immune responses to S. enterica serovar Typhimurium by activating dendritic cells and driving Th1 polarization, which are important properties to consider in the development of effective S. enterica serovar Typhimurium vaccines and immunotherapy adjuvant.Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that play key roles in the regulation of immune responses to a variety of antigens and immune sentinels as initiators of T cell responses against microbial pathogens [1-3]. In addition, during inflammation or infection, DCs are mobilized in and out of the peripheral tissues. Activated DCs are targeted to secondary lymphoid organs and toward T cell activation by antigen presentation [4,5]. DCs can capture degraded bacteria or protein of bacteria and present their antigens on major histocompatibility complex (MHC) class molecules to T cells [6]. As a result, an adaptive immune response that specifically targets bacteria-derived antigens is initiated. Maturing DCs then migrate to the lymphoid organs, where they activate na？ve T cells by stimulating antigenic peptide-presenting MHC type I and II receptors and their co-stimulatory molecules [7]. Therefore, DCs provide a link between innate and adaptive immune responses.Salmonella species cause typhoid fever and gastroenteritis in humans and pose a