D-092. Antibody Respose Patterns to Bordetella pertussis Antigens in Vaccinated (primed) and Unvaccinated (unprimed) Young Children with Pertussis

J. D. Cherry1, U. Heininger2;
1David Geffen Sch. of Med., Univ. of California, Los Angeles, CA, 2Univ. Children's Hosp., Basel, SWITZERLAND.

Background: It is generally thought that the antibody response pattern occurs earlier in primed compared with unprimed persons. However this has not been quantitated in regard to pertussis in previously vaccinated and unvaccinated children. Methods: The ELISA antibody values to B. pertussis antigens PT, FHA, PRN and FIM-2 were analyzed by time of sera collection after onset of illness in 183 children with pertussis who were vaccine failures or were previously unvaccinated. The vaccine failures had received a DTaP vaccine which contained PT, FHA, PRN and FIM-2. Results: For sera collected from 0 to 15 days after illness onset, the GMTs for all 4 antigens were significantly lower in the unvaccinated group as compared to children who had received DTaP (PT 3 vs 24 EU/ml; FHA 3 vs 51 EU/ml; PRN 4 vs 69 EU/ml; FIM-2 0.9 vs 2.4 EU/ml). In the unvaccinated group the GMT of PT antibody rose rapidly over time so that it was similar to that of DTaP recipients at the 16-30 day period (32 vs 37 EU/ml; p=0.8) and at > 50 days was higher than the GMT of the DTaP group (160 vs 46 EU/ml; p=0.2). The FHA antibody pattern rise was less marked than that of PT in the unvaccinated subjects and its peak was lower than that in the previous DTaP recipients (28 vs 171 EU/ml; p=0.004). The PRN antibody pattern in the unvaccinated was less marked than that in DTaP group and the peak titer was > 10 fold less (13 vs 266 EU/ml; p= <0.0001). The response to FIM-2 was delayed and minimal in the unvaccinated children as compared with the former DTaP vaccinees (1.2 vs 2.4 EU/ml; p= 0.1). Conclusions: The findings in this study may support the idea of a quicker antibody response in primed vs unprimed children but the higher values could be due to residual values from immunization. Over time the response to FHA, PRN and FIM-2 was greater in the primed vs the unprimed. However the response to FIM-2 was minimal in both groups. Interestingly the response to PT in the unprimed had a sharp response curve and the final GMT was higher (but not significantly so) than that in the primed children.