RELATIONS BETWEEN ANTIGENIC COMPONENTS AND PROTECTIVE POTENCY OF HEMOPHILUS PERTUSSIS^(a)

Abstract

There are three antigens in H. pertussis, i. e. capsular themolabile L, relatively stable S, and somatic stable O antigen. H. pertussis can be classified serologically into three phases with the aid of factor serum. There are various phases in freshly isolated strains. Phase I organisms show a trend to change to intermediates and phase III. Phase I organisms have a high protective potency in mice and that of phase III is low. The efficacy of H. pertussisvaccines depends on the presence of the capsular antigen, especially of the L antigen. The amount of capsular K antigen of phase I organisms diminishes under various unsuitable cultural conditions.