Contribution of the B oligomer to the protective activity of genetically attenuated pertussis toxin.

An enzymatically deficient recombinant S1 subunit, in which Arg-9 was replaced by Lys, was combined with native B oligomer to form a mutant holotoxin molecule. This molecule exhibited decreased leukocytosis-promoting and histamine-sensitizing activities compared with those of the native toxin, supporting the view that the B oligomer is not responsible for these activities. The protective activity of this genetically attenuated pertussis toxin was compared with that of B oligomer alone. The mutant pertussis toxin and B oligomer were similarly capable of protecting mice against a respiratory infection with Bordetella pertussis, suggesting that the B oligomer makes a significant contribution to the protection afforded by the genetically attenuated holotoxin.