Development of a multi-specificity opsonophagocytic killing assay

The opsonophagocytic-killing assay (OPKA) is one of the primary surrogate a ssays for evaluating the pneumococcal capsular polysaccharide-protein conju gates under development as vaccines. Because each vaccine contains seven or more different conjugates, multiple OPKA must be performed on each serum. Moreover, the large number of assays can deplete serum samples from infants . To reduce the amount of serum and effort required to conduct OPKA we deve loped a multi-specificity OPKA using antibiotic resistant pneumococci. Equa l numbers of optochin-resistant serotype GB and streptomycin-resistant 19F pneumococci were used as the target bacteria. Surviving bacteria of each se rotype were enumerated by plating on agar containing the appropriate antibi otic. In an examination of 25 immune sera the results obtained with this ne w assay correlated well with those obtained when bacterial targets were exa mined individually. By using additional antibiotic resistance markers, more than two specificities can be examined in a single assay. (C) 2000 Elsevie r Science Ltd. All rights reserved.