Effect of 20 and 22 amino acid on superantigen activity of staphylococcal enterotoxin C2 / 中国免疫学杂志

Objective:To investigate the improved superantigen activity of SEC2(T20L/G22E) compared with recombinant staphylococcal enterotoxins C 2 ( rSEC2 ).Methods: The proliferation of spleen lymphocytes and T-cell subpopulations induced by rSEC2 and SEC2(T20L/G22E) were examined by WST-1 and flow cytometry separately,and the gene expression of cytokines and Vβspecificities were quantified by real-time PCR.Results: WST-1 and Flow cytometry assays showed that the superantigen activity of SEC2(T20L/G22E) was improved due to enhanced T-cell stimulating potency,resulting in massive activation of T-cells,particularly CD4+and CD8+T-cells.Quantitative real-time PCR assay showed that despite similar Vβspecificities induced by rSEC 2 and SEC2 (T20L/G22E),the quantities of activated T-cells bearing specific Vβwere different,and SEC2(T20L/G22E) could stimulate more gene expression of associated cytokines simultaneously.Conclusion: The results strongly suggested that the increased SEC 2 ( T20L/G22 E)-TCR-binding affinity contributed to more T-cells activation and cytokine release ,which elicit powerful immune activition.

Effects of Zn2+and Zn2+-coordinating glutamic acid residues on the superantigenic activities of staph-ylococcal enterotoxin C2 / 中华微生物学和免疫学杂志

Objective To investigate the role of Zn 2+and Zn2+-coordinating glutamic acid residues ( 71Glu and 80Glu ) in the superantigenic activities of staphylococcal enterotoxin C2 ( SEC2 ) .Methods Over-lap PCR was used to amply genes encoding recombinant mutant proteins rSEC 2 ( E71A), rSEC2 (E80A) and rSEC2 (E71A/E80A).The mutant proteins were expressed in E.coli BL21 (DE3) and puri-fied by affinity chromatography .The differences of biological activities between rSEC 2 and its mutants were compared in vitro.The effects of Zn 2+on the superantigenic activities of rSEC 2 were evaluated by analyzing the proliferation of splenic lymphocytes in the presence or absence of ethylenediaminetetraacetic acid ( EDTA) .Results The substitution of glutamic acid residue at position 71 and 80 by alanine residue had no significant effects on the superantigenic activities and the conformational stability of rSEC 2 mutants.How-ever, traces of Zn2+(10μmol/L) could significantly enhance rSEC2-induced proliferation of splenic lympho-cytes, and only certain amount of Zn 2+could completely restore rSEC2-induced proliferation in the presence of EDTA.Conclusion This study indicated that mutations at Zn 2+-coordinating glutamic acid residues had no significant effects on the conformational stability and the superantigenic activities of SEC 2.Zn2+might play a role in regulating the superantigenic activities of SEC 2 through some indirect ways .

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolates with Toxic Shock Syndrome Toxin and Staphylococcal Enterotoxin C genes / 대한진단검사의학회지

BACKGROUND: Many methicillin-resistant Staphylococcus aureus (MRSA) isolates in Korea possess a specific profile of staphylococcal enterotoxins in that the toxic shock syndrome toxin gene (tst) coexists with the staphylococcal enterotoxin C gene (sec). Because the analysis of staphylococcal cassette chromosome mec (SCCmec), a mobile genetic element mecA gene encoding methicillin resistance, showed that majority of these are SCCmec type II, these MRSA isolates with tst and sec may be genetically related with each other. This study was performed to investigate the genetic relatedness of tstand sec-harboring MRSA strains isolated in Korea by using pulsed-field gel electrophoresis (PFGE). METHODS: A total of 59 strains of MRSA isolates of SCCmec type II possessing tst and sec were selected for PFGE and phylogenetic analyses. These isolates were collected from 13 health care facilities during nationwide surveillance of antimicrobial resistance in 2002. RESULTS: The 59 MRSA isolates were clustered into 11 PFGE types, including one major group of 26 strains (44.1%) isolated from 7 healthcare facilities. Seven PFGE types contained 2 or more isolates each, comprising 55 isolates in total. CONCLUSIONS: Most of SCCmec type II MRSA isolates containing tst and sec showed closely related PFGE patterns. Moreover, MRSA isolates collected from different healthcare facilities showed identical PFGE patterns. These findings suggested a clonal spread of MRSA strains possessing tst and sec in Korean hospitals.

Fusion Immunotoxin Anti-HER-2-scFv-SEC2 Expressed in E.coli With an Improved Expression Vector pASK75-EX: Its Construction and Functioning / 生物化学与生物物理进展

A tumor-targeting recombinant fusion immunotoxin B-L-SEC2 was constructed by fusing staphylococcal enterotoxin C2 (SEC2) and an anti-HER-2 single-chain Fv B1 through a peptide linker, and expressed in E. coli strain BL21 (DE3) with an improved expression vector pASK75-EX as inclusion body. The denatured inclusion body was purified with Ni-NTA chelate agarose, and then re-natured by dialysis. FACS and MTT assays indicated that the re-natured fusion immunotoxin B-L-SEC2 could target the HER-2 over-expressing breast tumor cell SK-Br-3 in vitro, and inhibit the growth of SK-Br-3.

Study on superantigen SEC against glioma / 中国药理学通报

AIM To probe into antitumor effect of lymphocyte activated by superantigen SEC against glioma. METHODS Lymphocyte subset was analysed with APAAP method after the lymphocyte had been activated by SEC. The cytotoxicity of lymphocyte against glioma in vitro was evaluated by MTT method. With established animal model of glioma xenografted and immunity embeded model of HuPBL-SCID, we observed the growth of glioma. RESULTS The lymphocyte activated was mainly composed of CD4 + T lymphocyte. Lymphocyte activated by SEC had killing activety against 8 glioma cells and the group of 1?10 3 U?L -1 had shown the strongest killing power. The growth curve showed that:each of the rate of producing A, C and B group different suppress effect on glioma its suppress rate was 58.5%,46.2% and 36.3% respectively. CONCLUSION Lymphocyte stimulated by superantigen SEC produces killing power against glioma.

Preparation and preliminary application of monoclonal antibody against Staphylococcal enterotoxin C2 / 中国免疫学杂志

Objective:To obtain monoclonal antibodies(McAb) against Staphylococcal enterotoxin C2(SEC2) and establish method for detecting SEC2.Methods:The secreted SEC2 from staphylococcus aureus was used as antigen to immune BALB/c mice. Monoclonal antibodies against SEC2 were prepared by normal hybridoma technique. By identifying the characters of McAbs, the quantitative detection ELISA test method were established and were preliminarily applied.Results:Four hybridmas producing antibodies against SEC2 were obtained. IgG isotypes of four McAbs were IgG1. Their binding site was different except two McAbs that shared the same binding site.The McAbs were proved to be specific for SEC2.The sandwich ELISA method had good specificity, sensitivity and reproducibility, and it was founded to be able to detect SEC2 at concentration from 0.5 to 20 ng/ml. Its recovery ranged between 97.8% and 101%,and CV value ranged between 2% and 5%.Conclusion:The prepared McAb against SEC2 can be used for SEC2 immunoassay. This work provides a basis for controlling the quality of JINPUSU and researching staphylococcal enterotoxin.