SHIGELLA LIPOPOLYSACCHARIDE ANTIBODIES IN PEDIATRIC POPULATIONS

Shigellosis is the most common cause of bacterial dysentery, To study the specific immunity to the two major groups causing shigellosis, we assayed antibodies to lipopolysaccharide (LPS) by enzyme-linked immuno adsorbent assay to both Shigella sonnei and Shigella flexneri 2a serot ypes in the following populations: (1) women immediately after deliver y and their infants to assess the transfer of passive immunity by plac enta and the presence of secretory antibodies in breast milk; (2) chil dren of different ages; and (3) the kinetics of antibody production in pediatric patients, who had culture-proved shigellosis, The sera of t hese women showed variable concentrations of antibodies of all three i sotypes to LPS of S. sonnei and S. flexneri 2a. These serotype-specifi c antibodies were not cross-reactive. Transfer of IgG anti-LPS across the placenta was significantly correlated with concentration of the sp ecific antibody in the mother (S. sonnei, r = 0.96; S. flexneri, r = 0 .84). Varying concentrations of anti-LPS IgA were present in colostrum , which was correlated with serum anti-LPS IgA titers in the case of S . sonnei (r = 0.44; P <0.05) but not S. flexneri (r = 0.17). Healthy c hildren between the ages of 6 months and 4 years in our population had undetectable or relatively low titers of anti S. sonnei IgG, More chi ldren had detectable antibody titers to S. flexneri 2a than to S. sonn ei. The relatively high concentrations of these natural antibodies are particularly noteworthy because there is a far lower incidence (<10% of patients) with S. flexneri than with S. sonnei disease in this popu lation, Determination of antibody titers from 15 patients, all of whom had S. sonnei infection, showed an increase in IgM and IgG antibody c oncentration in their convalescent sera, Therefore we speculate that t he presence of anti-LPS IgG correlates with protection from shigellosi s in pediatric populations.