RESPONSES TO BORDETELLA-PERTUSSIS MUTANT STRAINS AND TO VACCINATION IN THE COUGHING VAT MODEL OF PERTUSSIS

Phase I strains 18-323, Tohama and L-84 of Bordetella pertussis produc ed paroxysmal coughing when encased in agarose beads and administered intrabronchially to adult Sprague-Dawley rats. In contrast, the Phase IV variant of strain L-84 was inactive in cough induction, as was stra in BP 357, a transposon-insertion mutant which is deficient only in pe rtussis toxin (PT). Strain BPM 1809, which lacks only the heat-labile toxin, was similar to the unmodified Phase I strains for cough inducti on, indicating that this toxin is not needed to induce coughing. B, pa rapertussis also was inactive as a cough inducer. These results indica te that PT, present in Phase I strains of B. pertussis, and absent fro m Phase IV strains, strain BP 357 and B. parapertussis, is essential f or the induction of paroxysmal coughing in this rat model of whooping cough. Prior injection of DTP (whole-cell) Vaccine greatly reduced the incidence of coughing in rats challenged subsequently with Phase I B. pertussis. Serological responses were monitored after intrabronchial infection with the various bacterial strains and after vaccination and challenge. The PT-positive or -negative status of the strains in vivo was confirmed by the appropriate presence or absence of anti-PT IgG i n the convalescent sera.