title: Variable susceptibility to opsonophagocytosis of group A streptococcus M-1 strains by human immune sera.
abstract: Immunity to group A streptococci (GAS) is thought to be related to the acquisition of type-specific antibody directed against the M protein. However, recent work suggests that immunity may only be strain and not M-type specific. Therefore, susceptibility of 70 different GAS M-1 strains to opsonization and killing by convalescent sera was compared by using a highly sensitive chemiluminescence assay and by standard bactericidal assay. Sequencing of the emm1 gene in 10 strains with variable susceptibility to opsonization revealed 100% homology in 9 strains. Several substitutions in the N-terminal and 2 in the A3 repeat regions of strain CS-190 were associated with profound resistance to opsonization. Thus amino acid substitutions within different regions of the M-1 protein molecule may adversely affect opsonization by immune sera. In addition, non-M protein factors from identical M types influence susceptibility to phagocytosis. These findings may in part explain the persistently high prevalence of M-1 strains worldwide over the last 15 years.
authors.affiliation: Centro de Investigacion Biomedica de Occidente (CIBO), Instituto Mexicano del Seguro Social, Guadalajara, Mexico.
authors.forename: A
authors.initials: A
authors.lastname: Villaseñor-Sierra
authors.forename: W M
authors.initials: WM
authors.lastname: McShan
authors.forename: D
authors.initials: D
authors.lastname: Salmi
authors.forename: E L
authors.initials: EL
authors.lastname: Kaplan
authors.forename: D R
authors.initials: DR
authors.lastname: Johnson
authors.forename: D L
authors.initials: DL
authors.lastname: Stevens
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D001770:Blood Bactericidal Activity; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D003165:Complement System Proteins / Q000276:immunology; D006801:Humans; D007106:Immune Sera / Q000276:immunology*; D008163:Luminescent Measurements; D008969:Molecular Sequence Data; D009895:Opsonin Proteins / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology*; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013290:Streptococcal Infections / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000145:classification / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D007106:Immune Sera; D009895:Opsonin Proteins; C014689:streptococcal M protein; D003165:Complement System Proteins