Little is known about the virulence SN-38 factors of SS2. To date, only a few SS2 virulence associated factors have been identified and characterized; these include the capsular polysaccharide (CPS) [1], suilysin (SLY) [6], muramidase-released protein (MRP) [7], extracellular protein factor (EF) [8], adhesin [9], cell wall-associated and extracellular proteins [10], fibronectin- and fibrinogen-binding protein (FBP) [11], a serum opacity factor [12], and the arginine deiminase system [13, 14]. An understanding of SS2-host molecular interactions is crucial for understanding

SS2 pathogenesis and immunology. Conventional genetic and biochemical approaches used to study SS2 virulence factors are unable to take into account in the complex and dynamic environmental stimuli associated with the infection process. Recently, several technologies, including in vivo expression technology (IVET), differential fluorescence induction (DFI), signature-tagged mutagenesis (STM), transcriptional and proteomic profiling, and in vivo-induced antigen technology (IVIAT) have been developed to identify the pathogen genes Lazertinib mw expressed during the infection process [15, 16]. IVIAT is a method that allows for the direct identification of microbial proteins expressed at sufficient levels during host infection to be immunogenic. A schematic of the IVIAT procedure was

described by Rollins et al [16]. The advantage of IVIAT is that it enables the identification of antigens expressed specifically during infection, but not during Rigosertib growth in standard laboratory media. It was speculated that the genes

and gene pathways identified by IVIAT may play a role in virulence or pathogenesis during bacterial infection [17, 18]. IVIAT has been successfully used to identify arrays of in vivo induced proteins in Salmonella enterica serovar Typhi [19], Escherichia coli O157 [18], Group A Streptococcus (GAS) [17], Vibrio cholerae [20], and others, and these proteins have been shown to contribute to the pathogenesis or virulence of the infecting organisms. When IVIAT was applied however to E. coli O157, it identified 223 O157 proteins expressed during human infection. Among these, four proteins–intimin-γ (an adhesin), QseA (a quorum-sensing transcriptional regulator), TagA (a lipoprotein), and MsbB2 (an acyltransferase)–had been previously identified as virulence-related proteins [18]. To identify SS2 proteins that are immunogenic and expressed uniquely during SS2 infection, we applied the newly developed and modified IVIAT method. Briefly, we screened a library of SS2 proteins expressed in E. coli to identify clones that were immunoreactive with convalescent-phase sera, which had been previously fully adsorbed against in vitro-grown SS2 and E. coli organisms.