title: Mitogenic effect contributes to increased virulence of Streptococcus suis sequence type 7 to cause streptococcal toxic shock-like syndrome.
abstract: Streptococcus suis serotype 2 sequence type 7 strains emerged in 1996 and caused a streptococcal toxic shock-like syndrome in 1998 and 2005 in China. Evidence indicated that the virulence of S. suis sequence type 7 had increased, but the mechanism was unknown. The sequence type 7 strain SC84, isolated from a patient with streptococcal toxic shock-like syndrome during the Sichuan outbreak, and the sequence type 1 strain 31533, a typical highly pathogenic strain isolated from a diseased pig, were used in comparative studies. In this study we show the mechanisms underlying cytokine production differed between the two types of strains. The S. suis sequence type 7 strain SC84 possesses a stronger capacity to stimulate T cells, naive T cells and peripheral blood mononuclear cell proliferation than does S. suis sequence type 1 strain 31533. The T cell response to both strains was dependent upon the presence of antigen-presenting cells. Histo-incompatible antigen-presenting cells were sufficient to provide the accessory signals to naive T cell stimulated by the two strains, indicating that both sequence type 7 and 1 strains possess mitogens; however, the mitogenic effect was different. Therefore, we propose that the difference in the mitogenic effect of sequence type 7 strain SC84 compared with the sequence type 1 strain 31533 of S. suis may be associated with the clinical, epidemiological and microbiological difference, where the ST 7 strains have a larger mitogenic effect.
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China.
authors.forename: H
authors.initials: H
authors.lastname: Zheng
authors.forename: C
authors.initials: C
authors.lastname: Ye
authors.forename: M
authors.initials: M
authors.lastname: Segura
authors.forename: M
authors.initials: M
authors.lastname: Gottschalk
authors.forename: J
authors.initials: J
authors.lastname: Xu
mesh_terms: D000818:Animals; D001769:Blood / Q000382:microbiology; D015169:Colony Count, Microbial; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D006801:Humans; D008099:Liver / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D012772:Shock, Septic / Q000382:microbiology*; D013154:Spleen / Q000382:microbiology; D013290:Streptococcal Infections / Q000382:microbiology*; D017011:Streptococcus suis / Q000302:isolation & purification / Q000472:pathogenicity*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D013577:Syndrome; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D016207:Cytokines