Serum C-reactive protein and immune responses in dogs inoculated withBordetella bronchiseptica (phase I cells)

Eight Beagle dogs were inoculated intrabronchially with 5×109 live, avirulent cells ofBordetella bronchiseptica L-414 strain (phase I cells) (B. bronchiseptica) to investigate the serum levels of their C-reactive protein, the white blood cell counts, the antibody responses toB. bronchiseptica in the sera and tracheal secretions, and the effects of prednisolone given to four of the dogs on C-reactive protein (CRP), white blood cells (WBC) and immune responses. In two Beagle dogs inoculated intrabronchially with sterile physiological saline, the concentrations of CRP and the WBC counts did not increase. CRP was markedly increased one day after inoculation in the dogs inoculated withB. bronchiseptica to 385.0–720.0 µg/ml (mean 498±132 µg/ml) in the group given theB. bronchiseptica inoculation only, and to 372.0–649.0 µg/ml (mean 551±106 µg/ml) in the group treated with prednisolone following inoculation ofB. bronchiseptica, as determined by an enzyme-linked immunosorbent assay (ELISA). The CRP levels were 23–95 times the pre-inoculation values, which indicated that prednisolone had no effect on the production of CRP. In the prednisolone-treated group, the WBC count increased and stayed at an increased level for approximately 12 days. An indirect fluorescent antibody test led to the detection of anti-B. bronchiseptica IgM and IgG antibodies in the sera from 5 days afterB. bronchiseptica inoculation and S-IgA and IgG anti-B. bronchiseptica antibodies in the tracheal secretions on the day after the challenge exposure toB. bronchiseptica. The increase in CRP after challenge exposure toB. bronchiseptica was significantly (p<0.05) smaller than that found after the first inoculation ofB. bronchiseptica.