title: Alpha C protein-specific immunity in humans with group B streptococcal colonization and invasive disease.
abstract: Alpha C protein, found in 76% of non-type III strains of group B Streptococcus (GBS), elicits antibodies protective against alpha C-expressing strains in experimental animals, making it an appealing carrier for a GBS conjugate vaccine. We determined whether natural exposure to alpha C elicits antibodies in women. Geometric mean concentrations of alpha C-specific IgM and IgG were similar by ELISA in sera from 58 alpha C GBS strain colonized and 174 age-matched non-colonized women (IgG 245 and 313 ng/ml; IgM 257 and 229 ng/ml, respectively), but acute sera from 13 women with invasive alpha C-expressing GBS infection had significantly higher concentrations (IgM 383 and IgG 476 ng/ml [p=0.036 and 0.038, respectively]). Convalescent sera from 5 of these women 16-49 days later had high alpha C-specific IgM and IgG concentrations (1355 and 4173 ng/ml, respectively). In vitro killing of alpha C-expressing GBS correlated with total alpha C-specific antibody concentration. Invasive disease but not colonization elicits alpha C-specific IgM and IgG in adults.
authors.affiliation: Section of Infectious Diseases, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX 77030, USA. pannaraj@bcm.tmc.edu
authors.forename: Pia S
authors.initials: PS
authors.lastname: Pannaraj
authors.forename: Joanna K
authors.initials: JK
authors.lastname: Kelly
authors.forename: Marcia A
authors.initials: MA
authors.lastname: Rench
authors.forename: Lawrence C
authors.initials: LC
authors.lastname: Madoff
authors.forename: Morven S
authors.initials: MS
authors.lastname: Edwards
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Baker
mesh_terms: D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood* / Q000276:immunology; D000918:Antibody Specificity; D000954:Antigens, Surface / Q000276:immunology; D016470:Bacteremia / Q000097:blood; D001426:Bacterial Proteins / Q000276:immunology; D016022:Case-Control Studies; D005260:Female; D005312:Fetal Blood / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007231:Infant, Newborn / Q000097:blood; D010587:Phagocytosis / Q000276:immunology; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000097:blood*; D013290:Streptococcal Infections / Q000097:blood*; D013292:Streptococcus agalactiae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; C077961:alpha C protein, group B streptococci