Analysis of 'natural' and vaccine-induced Haemophilus influenzae type B capsular polysaccharide serum antibodies for 3H1, a V3-23-associated idiotope

The variable (V-) region repertoire of antibodies (Abs) to Haemophilus infl uenzae capsular polysaccharide (Hib PS) has been extensively studied in ind ividuals vaccinated against the microbe, but to a lesser extent in subjects who generated such Abs in response to a 'natural' encounter with this micr obe or its antigenic mimics. To gain an insight into the repertoire of Hib PS-reactive Abs in vaccinated and non-vaccinated individuals, we used a mon oclonal Ab, 3H1, which detects an idiotypic marker associated with an Ab V- region gene, V3-23. We show here that Hib PS-reactive Abs with detectable 3 H1 idiotope can be quantified by an indirect inimunoezymatic assay in serum samples of non-vaccinated healthy adults as well as of recently vaccinated healthy infants. The percentage of Abs that was simultaneously Hib PS-reac tive and 3H1-positive ranged widely (from 0 to 68%) among individual serum samples from both groups of subjects. No dramatic differences in the expres sion of 3H1 idiotope on Hib PS-reactive Abs were found between vaccinated a nd non-vaccinated individuals. Our results are consistent with the hypothes is that the utilization of V-region genes in Hib PS-reactive Abs that indiv iduals generate after a 'natural' encounter with Hib PS or its mimics is si milar to that in these Abs elicited by Hib PS conjugate vaccines. (C) 2000 Elsevier Science B.V. All rights reserved.