A RAPID AND SENSITIVE CHEMILUMINESCENCE ASSAY FOR EVALUATION OF FUNCTIONAL OPSONIC ACTIVITY OF HAEMOPHILUS-INFLUENZAE TYPE B-SPECIFIC ANTIBODIES

Luminol-enhanced chemiluminescence (CL) of heterologous neutrophils wa s used to assess the capacity of a 1-ng/ml concentration of Haemophilu s influenzae type b (Hib)-specific antibodies to induce opsonization o f Hib with autologous heat-inactivated sera from children immunized wi th Hib capsular polysaccharide-polyribosylribitolphosphate (Hib-PRP) c onjugate vaccine, Serum samples from 15 of 36 children (42%) vaccinate d with Hib-PRP conjugate vaccine had protective levels of Hib-specific antibodies of greater than or equal to 1,000 ng/ml. Ten of these 15 ( 67%) had poor or nonfunctional opsonic activity. Of the 10 children wh ose sera lacked opsonic activity, 5 (50%) presented with recurrent Hib infection. In contrast, none of the sera of 20 healthy adults lacked opsonic capability. CL intensity was proportional to the concentration of anti-Hib antibodies used for opsonization. Furthermore, the titers of Hib-PRP-specific antibody in children and adults did not correlate with opsonic activity, These results suggest that luminol-enhanced CL as described here with minute concentrations of antibody for opsoniza tion can be used to assess functional capacity of anti-Hib antibodies after vaccination or natural infection in the evaluation of patients w ith recurrent infections.