COUGH PRODUCTION, LEUKOCYTOSIS AND SEROLOGY OF RATS INFECTED INTRABRONCHIALLY WITH BORDETELLA-PERTUSSIS

Adult Sprague-Dawley rats infected intrabronchially with Bordetella pe i pertussis strain 18-323 encased in agarose beads (BP-beads), develop ed a paroxysmal cough and leucocytosis, both of which peaked at around day 10. When animals were exposed to ether for 2 min after delivery o f the beads, there was an enhancement of the number of subsequent coug hing episodes. Inclusion of carrageenan in the beads also enhanced cou ghing. Control rats, given sterile beads or left untreated, showed onl y a low level of coughing or no coughing, depending upon their source. Rats challenged by the same route with heat-killed B. pertussis in be ads, or with live organisms in suspension (without beads) showed no co ugh induction or leucocytosis. However, intranasal delivery of B. pert ussis suspension gave rise to a moderate amount of coughing and leucoc ytosis. Serum IgG responses to B. pertussis antigens were greatest in rats infected with BP-beads and antibodies against both pertussis toxi n and filamentous haemagglutinin were detected. Since the rat is the o nly conveniently accessible laboratory animal species in which B. pert ussis induces an intermittent. paroxysmal cough, as in man, it merits further study for determining the mechanisms of pathogenesis and immun ity in pertussis.