title: Immunological response mounted by Aboriginal Australians living in the Northern Territory of Australia against Streptococcus pyogenes serum opacity factor.
abstract: Streptococcus pyogenes (Group A streptococcus) interacts with host fibronectin via a number of distinct surface components. The streptococcal serum opacity factor (SOF) is a cell-surface protein of S. pyogenes which causes opalescence of human serum and mediates bacterial binding to fibronectin. In this study, hexahistidyl-tagged fusion proteins encompassing full-length SOF, and domains of SOF encompassing opacity factor activity and fibronectin-binding regions, were used in the characterization of the Aboriginal immune response to SOF. Anti-SOF serum IgG responses were found to be significantly higher (P<0.0001) in Aboriginal adults and children when compared to a non-Aboriginal adult group. The Aboriginal immune response against the fibronectin-binding region of SOF was significantly reduced when compared to the response against the whole SOF protein and N-terminal domains examined in this study (P<0.001). This pattern of immune response was also observed in rabbits immunized with recombinant SOF. Comparison of the deduced amino acid sequence of SOF from a number of common Australian isolates with other SOF sequences revealed that the N-terminus of SOF exhibits sequence similarity values ranging from 42.9% to 96.5%. The C-terminus containing the fibronectin-binding domain and membrane-spanning regions was more highly conserved, exhibiting sequence similarity values ranging from 84.6% to 100% within the fibronectin-binding repeats. These data suggest that the immune response against SOF is directed toward the variable N-terminus of the SOF protein. Phylogenetic analysis indicated that the sof genes of S. pyogenes do not exhibit geographical variation.
authors.affiliation: Department of Biological Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Gillen
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Towers
authors.forename: David J
authors.initials: DJ
authors.lastname: McMillan
authors.forename: Armando
authors.initials: A
authors.lastname: Delvecchio
authors.forename: K S
authors.initials: KS
authors.lastname: Sriprakash
authors.forename: Bart
authors.initials: B
authors.lastname: Currie
authors.forename: Berndt
authors.initials: B
authors.lastname: Kreikemeyer
authors.forename: Gurusharan S
authors.initials: GS
authors.lastname: Chhatwal
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Walker
mesh_terms: D018829:Adhesins, Bacterial; D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000097:blood*; D001426:Bacterial Proteins / Q000276:immunology; D015153:Blotting, Western; D002352:Carrier Proteins / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008969:Molecular Sequence Data; D015876:Northern Territory; D010447:Peptide Hydrolases / Q000235:genetics / Q000276:immunology*; D010802:Phylogeny; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012463:Saliva / Q000276:immunology*; D013297:Streptococcus pyogenes / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D014774:Virulence
chemical_list: D018829:Adhesins, Bacterial; D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; D011994:Recombinant Proteins; C078635:fibronectin-binding proteins, bacterial; C021908:opacity factor; D010447:Peptide Hydrolases