Titres of class-specific antibodies against Shigella and Salmonella lipopolysaccharide antigens in colostrum and breast milk of Costa Rican, Swedish and Vietnamese mothers.

Enzyme immunoassays (EIA) were used to estimate titres of class-specific antibodies against purified and chemically defined phenol-water-extracted lipopolysaccharide (LPS) antigens of Salmonella serogroup B (BO), Shigella dysenteriae type I, Plesiomonas shigelloides (the same O-antigen as Shigella sonnei) and Shigella flexneri Y. Titres in colostrum and breast milk of Swedish, Vietnamese and Costa Rican mothers from various socioeconomic conditions were compared. The antibodies were mainly of the IgA isotype. IgM antibodies were also present, but only very low concentrations of IgG were found. In Costa Rican mothers, the IgA antibody titres were significantly higher (P less than 0.05) in women of low and middle socioeconomical conditions than were those in mothers of high socioeconomical level. The low titres in the last group were comparable to those found in Swedish mothers. The IgA antibody titres found in Vietnamese mothers were similar to those of Costa Rican mothers from the low and middle socioeconomic conditions, being highest against S. flexneri Y LPS. The IgM antibody titres were also highest in Vietnamese mothers, immediately followed by the Costa Rican mothers of low socioeconomic conditions. The low IgM titres in the Costa Rican women of high socioeconomic level were comparable to those seen in Swedish mothers. The results suggest that, in Costa Rica and Vietnam, S. flexneri is the most prevalent Shigella sp. causing infection and that Salmonella serogroup B infections are rare in all three countries. The results also show that the antibody repertoire in colostrum and breast milk varies. Furthermore, in addition to the prevalence of a specific micro-organism in a determined geographical area, such differences may be associated mainly with exposure to certain pathogens in particular socioeconomic conditions.

Antibodies against invasion plasmid coded antigens of shigellae in human colostrum and milk.

Colostral and milk samples of Swedish, Vietnamese and Costa Rican mothers living under various socioeconomic conditions were tested for the presence of shigella invasion plasmid coded antigen (Ipa) specific antibodies. IgA antibodies of this specificity were found in significantly higher titres in samples of Vietnamese (600 +/- 338) than in samples of Swedish or high income Costa Rican mothers (190 +/- 224 and 290 +/- 241, respectively; p < 0.05). Specific IgA titres in the low income group of Costa Rican mothers (470 +/- 338) did not differ significantly from the values obtained in Vietnam. While no Ipa specific IgM could be detected in any of the samples tested, specific IgG was found in 90% of the Vietnamese colostrum. These data indicate that antibodies which could be responsible for the dysentery-preventing effect of breast feeding are indeed present in human colostrum and milk in areas where shigellosis occurs with relatively high incidence.