In the summer of 1975, aS

In the summer of 1975, aS.zooepidemicusdisease outbreak occurred among pigs in the Sichuan province, China. Furthermore, the adherence ofS. zooepidemicusto HEp-2 cells was inhibited by anti-rSzP antibodies in a dose-dependent manner. We employed a Pentiapine random 12-peptide phage display library for screening of immunodominant mimics of the SzP, which were recognized by an anti-SzP specific monoclonal antibody (mAb 2C8). Initial positive phage clones were identified by ELISA, followed by assays to determine the adherence-inhibiting ability of the peptide. == Results == Ten out of fourteen selected positive clones showed high reactivity that effectively inhibited the binding of mAb 2C8 to rSzP. The motif XSLSRX was highly conserved among six of the ten clones. == Conclusion == Collectively, our findings suggest that the motif XSLSRX may represent an immunodominant mimic epitope of the SzP ofS. zooepidemicusstrain ATCC 35246, and that the same epitope may be used to mediate SzP binding to HEp-2 cells. == Background == Streptococcus equisubsp. zooepidemicus(S. zooepidemicus), which belongs to Lancefield group C streptococci, is an important animal pathogen, especially in horse [1]. It has a broad host spectrum and occasionally infects humans. Human infections may occur following ingestion of unpasteurized milk or dairy products [2], or after contact with pigs [3]. In China,S. zooepidemicusis the main pig pathogen. In the summer of 1975, aS.zooepidemicusdisease outbreak occurred among pigs in the Sichuan province, China. Clinical symptoms of the diseased pigs included painful swelling of the joints, respiratory disturbances, and diarrhea. More than 300,000 pigs died within two weeks. According to bacteriological examinations,S. zooepidemicuswas isolated from most of the diseased pigs, and it appeared to be one of the major causative brokers [4]. M protein is an important virulence factor of group A streptococci: this fibrillar, surface-exposed protein deters opsonization of the organism using the alternate complement pathway [5,6]. Strains of group A streptococci expressing M protein are resistant to phagocytosis by human polymorphonuclear leukocytes, whereas strains that fail to express M protein are avirulent [7]. Previous studies exhibited thatS. zooepidemicuscarry antigens with characteristics of the antiphagocytic M protein of the Lancefield group A and G streptococci; it was named Pentiapine M-like protein (SzP) [8]. Cloning of the gene encoding SzP from an equine strain of subsp.zooepidemicusrevealed a single open reading frame of 1 1,128 bp [9], whereas the SzP gene (GenBank accession number:AY263781) from a pig strain of subsp.zooepidemicusshowed a single open reading frame of 1 1,137 bp (GenBank accession number:U04620) [10]. Similar to other streptococcal species,S.zooepidemicusbinds to a number of host proteins, including immunoglobulin G [11], serum Pentiapine albumin [12], fibronectin, collagen [13], and -macro-globulin [14] through cell surface components. These host-parasite recognition components may function as virulence factors by acting as adhesions or antiopsonins. Bacterial adhesion to the host cell is the first step in bacterial infection. The M protein of streptococcus group A is an adhesin that can bind to the host cell, however it Pentiapine is not known whether the SzP ofS. zooepidemicusalso functions as an adhesion, and the adhesion mechanism of SzP binding to host cell is usually unclear. Here, we report the adhesive function of the SzP to human HEp-2 epithelial cells. Furthermore, we identified several immunodominant mimic epitopes of SzP using random peptide phage library in combination with ELISA and binding-inhibition assays. Alignment of the phage display peptides yielded a conserved motif, XSLSRX, which represents an immunodominant Mouse monoclonal to CD48.COB48 reacts with blast-1, a 45 kDa GPI linked cell surface molecule. CD48 is expressed on peripheral blood lymphocytes, monocytes, or macrophages, but not on granulocytes and platelets nor on non-hematopoietic cells. CD48 binds to CD2 and plays a role as an accessory molecule in g/d T cell recognition and a/b T cell antigen recognition mimic epitope of the SzP ofS. zooepidemicusstrain ATCC 35246 and may mediate binding to HEp-2 cells. == Results == == Molecular characterization of M-like Pentiapine protein == Nucleotide sequence analysis revealed a single open reading frame in theszpgene ofS. zooepidemicusATCC 35246 isolated from pigs; translation of this open reading frame revealed a protein of 379 amino acids. Theszpgene showed 86.9% homology at the nucleotide level with.