Are the enzyme immunoassays for antibodies to pneumococcal capsular polysaccharides serotype specific?

The specificity of antibody binding to pneumococcal capsular polysaccharide s (Pnc PSs) measured by enzyme immunoassay (EIA) was studied by inhibition of antibody binding by homologous and heterologous PSs, We found extensive cross-reactivity of antibody binding to type 6B, 19F, and 23F PSs but not t o type 14 PS, even after treatment with cell wall PS (CPS), The cross-react ive antibody was highly prevalent in sera of infants and adults with natura lly acquired antibody, but not in sera of infants and adults immunized with pneumococcal vaccines, However, a type 11A antibody response was seen afte r vaccination with heterologous PSs, Monoclonal antibodies prepared against a type 6B PS-tetanus toroid conjugate recognized also other than the speci fic type of PS in the EIA, implying the possible existence of a cross-react ive epitope, Remarkable differences in specificity among type 6B PS prepara tions from different manufacturers were found. Moreover, different lots of type 11A PS from the same manufacturer showed differences in specificity. T he results suggest that some Pnc PS preparations may contain cross-reactive epitopes or impurities, other than CPS, that are common to many types of P nc PS, The specificity of antibodies, especially in sera from nonimmunized subjects, measured by EW can be questioned.