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.
Subject(s)
Antibodies, Bacterial/blood , Pregnancy Complications, Infectious/blood , Streptococcal Infections/blood , Streptococcus agalactiae/immunology , Adolescent , Adult , Antibodies, Bacterial/immunology , Antibody Specificity , Antigens, Surface/immunology , Bacteremia/blood , Bacterial Proteins/immunology , Case-Control Studies , Female , Fetal Blood/immunology , Humans , Immunoglobulin G/blood , Immunoglobulin M/blood , Infant, Newborn/blood , Phagocytosis/immunology , PregnancyABSTRACT
Group B Streptococcus (GBS) beta C protein elicits protective antibodies in experimental animals, making beta C protein an attractive component of a human GBS glycoconjugate vaccine. We determined whether natural exposure to beta C protein elicits antibodies in humans. Geometric mean concentrations (in micrograms per milliliter) of beta C-specific immunoglobulin (Ig) M and IgG as determined by enzyme-linked immunosorbent assay were similar in serum from 16 colonized (0.82 and 0.76, respectively) and 48 age-matched noncolonized (0.96 and 0.74, respectively) pregnant women. Serum from 3 women with beta C GBS bacteremia had significantly higher levels of IgM (6.0) and IgG (52.9) (P=.01 and 0.01, respectively). Invasive disease but not colonization elicits beta C-specific IgM and IgG.
