Luminol-Enhanced Chemiluminescence for Evaluation of Type III Group B Streptococcal Opsonins in Human Sera

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Abstract
A luminol-enhanced chemiluminescence (CL) assay was developed to evaluate type III group B streptococcal opsonins. Sera from 11 adults that contained high (>25 μg/ml), intermediate (3–24 μg/ml), or low P < 0.005), IgG- and C3-IF values, and phagocytic and bactericidal indices. Heat-stable CL activity correlated with antibody concentration (P < 0.0001) and was related to IgG-IF values and phagocytic indices. Significant bactericidal activity was demonstrated in all sera containing >2 μg of antibody/ml, but no bactericidal activity was observed in heat-inactivated sera. Adsorption of heated sera with type III group B Streptococcus abolished CL activity, whereas CL values of MgEGTA-chelated sera were ∼80% of untreated sera. Thus, type-specific antibody in addition to heat-labile serum factors, including those of the alternative complement pathway, contribute to opsonization of type III group B Streptococcus.