Serotype-Specific Cell-Mediated Immunity Associated With Clearance of Homotypic Group B Streptococcus Rectovaginal Colonization in Pregnant Women

We investigated the association between group B Streptococcus (GBS) serotype-specific capsular polysaccharide cellular immunity, measured with enzyme-linked immunospot (ELISPOT) interferon gamma release assay at 20 weeks gestation in pregnant women, and its effect on rectovaginal serotype-specific GBS colonization up to 37 weeks gestation. Among women colonized by serotype III at enrollment, interferon gamma ELISPOT positivity was more common in those in whom colonization was cleared (44.4%) than in those in whom colonization persisted (7.4%; P = .008), with a similar trend observed for serotype Ia. Presence of serotype-specific capsular polysaccharide cell-mediated immunity contributes to the clearance of GBS rectovaginal colonization.