Colonization in the rectum and uterine cervix with group B streptococci may induce specific antibody responses in cervical secretions of pregnant women

Abstract

We have studied the relationships between genital or rectal carriage of group B streptococci (GBS) with the levels of systemic and mucosal antibodies to GBS in 200 women at about week 17 of pregnancy. Secretions from the uterine cervix were collected with absorbent cylindrical wicks for quantification of antibody levels with whole cell enzyme-linked immunosorbent assay. GBS were cultured from the cervix (with or without concomitant rectal colonization) of 13.5%, from the rectum (with or without concomitant cervical colonization) of 12%, and from both culture sites of 8.5% of the women. Serotypes Ia, II, and III were predominant. Compared with culture-negative women, the group of women colonized rectally had markedly elevated levels of both immunoglobulin A (IgA) and IgG antibodies to GBS in cervical secretions and also had a moderate but significant elevation of IgA antibodies in sera. Women colonized only in the cervix had increases of specific IgA and IgG antibodies in cervical secretions, but their serum antibody levels were not elevated. In cervical secretions, the increase in antibody levels in the groups of colonized women was most pronounced for the IgG isotype, indicating a mucosal immune response involving IgG as well as IgA. A close correlation was found among the levels of antibodies to each of the three GBS serotypes tested. Evidence for such cross-reacting antibodies to different serotypes of GBS, as well as to group A streptococci, was also obtained from absorption experiments. Altogether, our results show that undiluted secretions for antibody determination can be easily collected from the uterine cervix with absorbent wicks and demonstrate that colonization of GBS in the rectum and the uterine cervix may induce a systemic as well as a pronounced local immune response in the female genital tract. The findings may have implications for the development of a mucosal vaccine against GBS disease.

Cervical Secretions in Pregnant Women Colonized Rectally with Group B Streptococci have High Levels of Antibodies to Serotype III Polysaccharide Capsular Antigen and Protein R

“…Previously, we reported the results of whole-cell GBS ELISA in arbitrary units by end-point titration using a reference serum [8]. We have now quantified (w/v) the amount of IgA and IgG antibodies in this serum to whole-cell GBS serotype III, as well as to purified protein R 4 and CPS III.…”

“…We have previously demonstrated induction of cervicovaginal antibodies after rectal immunization of mice [7]. Recently, we reported antibody levels to GBS serotypes Ia, II and III in serum and in cervical secretions from 200 pregnant women, using whole-cell GBS ELISA [8]. We found high levels of specific immunoglobulin (Ig)A and IgG antibodies in cervical secretions from women colonized with GBS in the rectum or in the uterine cervix, compared to non-colonized women.…”

“…Patients, collection of samples and bacteriological assessment. Details have been given previously [8]. Briefly, 200 pregnant women at about gestational week 17 were included in the study.…”

“…We have now quantified (w/v) the amount of IgA and IgG antibodies in this serum to whole-cell GBS serotype III, as well as to purified protein R 4 and CPS III. Part of the ELISA plate was assayed for the relevant antigen as described previously for whole-cell GBS [8], and below for protein R 4 and CPS III. Another part of the plate was coated either with 1:4000 dilutions in PBS of affinity-purified goat antibodies to human IgA (a chain-specific: Sigma) or F(ab 0 ) 2 fragments of affinity-purified goat antibodies to human IgG (g chain-specific: Sigma).…”

“…Determination of total IgA and IgG concentrations in sera and secretions has been described previously [8].…”