ANTI-POLYSACCHARIDE IMMUNOGLOBULIN ISOTYPE LEVELS AND OPSONIC ACTIVITY OF ANTISERA - RELATIONSHIPS WITH PROTECTION AGAINST STREPTOCOCCUS-PNEUMONIAE INFECTION IN MICE

Relationships between in vitro parameters (opsonic activity and anti-p neumococcal polysaccharide [PS] antibody subclasses) and in vivo mouse protection were established by logistic regression analysis. Data wer e from 158 mice challenged with pneumococci after vaccination with syn thetic oligosaccharide- and PS-protein conjugates in combination with the adjuvant Quil A. The hypothesis that serum opsonic activity has pr edictive value for protection against pneumococcal infection was teste d. Serum opsonic activity was well correlated with protection (chi(2) = 35.5, P < .001), although a stronger correlation was observed for an ti-PS IgM and IgG. The combined use of IgG and opsonic activity as pre dictor variables yielded the best fitting model for predicting protect ion (chi(2) = 74.1, P < .001). When opsonic activity data were added t o models that included various antibody isotypes, the statistical sign ificance of the models was enhanced. Thus, the opsonic activity of ant isera induced by pneumococcal vaccines can predict mouse protection.