THE V-REGION REPERTOIRE OF HAEMOPHILUS-INFLUENZAE TYPE-B POLYSACCHARIDE ANTIBODIES INDUCED BY IMMUNIZATION OF INFANTS

Haemophilus influenzae type b (Hib) is a significant pathogen for youn g children, and three Hib vaccines (named PRP-OMPC, HbOC, and PRP-T) a re currently available for young children. Extensive studies of anti-H ib polysaccharide (PS) antibodies (Abs) have shown that the V regions of Abs against the Hib PS comprise a VH gene in the VH3 gene family an d a VL gene from various V-kappa and V-lambda subgroups. To study immu nogenic properties of the three vaccines in young children, we determi ned the VL subgroups and avidities of anti-Hib-PS Abs induced by the t hree clinically available conjugate vaccines. Ab avidity was measured by determining the concentration of a Hib-PS oligomer that abrogates h alf of the binding of immunoglobulin G anti-EIib-PS Abs to microwells. The PRP-OMPC vaccine induced lower-avidity Abs than the prelicensure HbOC vaccine (P = 0.05). When we compared anti-Bib-PS Abs expressing V (kappa)Ia, VkappaII, and V-lambda subgroups, a greater Ab response was induced by the prelicensure HbOC vaccine than other vaccines (P < 0.0 5). When anti-Hib-PS Abs with the VkappaII subgroup were compared, how ever, both PRP-T and prelicensure HbOC vaccines induced a comparable r esponse, which in turn was greater than those induced by the PRP-OMPC or the postlicensure HbOC vaccine (P < 0.001). The VL repertoire of Ab s induced with the prelicensure HbOC or PRP-T vaccine in young childre n is dominated (about 80%) by anti-Hib-PS Abs using subgroup VkappaII. However, anti-Hib-PS using VkappaII VL accounts for only about 49% of the total anti-Hib-PS Abs induced with the PRP-OMPC vaccine or the po stlicensure HbOC. Our data suggest that immunogenic properties of Hib vaccines in young children vary depending on the vaccine preparations as well as the vaccine types.