INTRANASAL INOCULATION OF BORDETELLA-BRONCHISEPTICA IN MICE INDUCES LONG-LASTING ANTIBODY AND T-CELL MEDIATED IMMUNE-RESPONSES

Humoral and cellular immune responses were analysed in mice inoculated intranasally with Bordetella bronchiseptica. After infection, the num ber of bacteria that colonized the respiratory tract of the mice incre ased during the first day and decreased thereafter. Total IgG levels i ncreased as early as 14 days after infection and decreased with time a fter infection, whereas total IgA and IgM levels were lower but remain ed stable. Specific antibodies to the bacteria were mainly IgG2a and I gA and persisted up to 10 months after infection. Some of these specif ic antibodies were directed against adenylate cyclase-haemolysin, the bacterial factor that had been shown to be necessary for initiation of infection. The proliferation of Bordetella bronchiseptica-reactive sp leen cells occurred during the acute phase of infection. T cells from infected mice produced increasing amounts of IFN gamma and IL-2 after infection. Although very low levels of IL-10 were produced, no IL-4 wa s detected after bacterial stimulation in vitro. These results suggest that Bordetella bronchiseptica infection induces primarily a Th1-type T-cell response. Importantly, the authors demonstrated that antibody and T-cell responses directed against bacterial determinants of the vi rulent strain and to purified adenylate cyclase-haemolysin were longla sting. This observation could be due to the fact that Bordetella bronc hiseptica may persist intracellularly in the host as it was demonstrat ed in vitro.