Serum Antibody Titres to Shigella Lipopolysaccharides and Invasion Plasmid Antigens in Healthy Costa Rican and Swedish Women

Abstract

Specific serum antibody titres to defined lipopolysaccharides (LPS) of Shigella spp. and Salmonella serogroup B (BO) and Shigella invasion plasmid antigens (Ipa) were determined by enzyme immunoassays in healthy Costa Rican women from low (n = 34), middle (n = 36) and high (n = 19) socioeconomic conditions and from 64 Swedish women. Specific IgG antibody titres were the highest, in particular to the S. flexneri Y LP, with mean titres of 750 (SD = 360), 690 (380), and 820 (300) for the Low, Middle and High Costa Rican groups respectively. Lower titres were recorded against S. sonnei and S. dysenteriae type 1. Titres against Salmonella LPS were very low (< 250). In Swedish women, significantly lower serum anti-LPS titres were found (p < 0.05). No statistically significant differences regarding socioeconomic conditions or serum anti-LPS titres were seen in the Costa Rican groups (p > 0.05). Mean IgG-titres to the Ipa of 330 (150), 220 (170) and 140 (110) were found for the 3 Costa Rican groups, respectively. The IgG and IgM titres to Ipa in serum from the Low group were significantly higher than those of the High group (p < 0.05). The mean serum IgG titre of 70 (90) for the Swedish women was significantly lower than that of the Low and Middle groups (p < 0.05), but similar to that of the High group (p > 0.05). High IgG anti-Ipa titres were found in 38% from the Low, 19% from the Middle but none in the High group (mean value of the High group +2 SD). The anti-Ipa antibodies in the Costa Rican groups seemed to be a better indicator of Shigella exposure than were anti-LPS antibodies. A good degree of correlation was found between serum and colostrum IgA anti-Ipa titres (0.651, p < 0.001), and serum S. flexneri LPS and colostrum IgA anti-S. flexneri LPS antibody titres (0.607, p < 0.001).