Protection against experimental Bordetella bronchiseptica infection in mice by active immunization with killed vaccine

Abstract

Mice immunized with a killed vaccine of phase I Brodetella bronchiseptica were challenged with various numbers of virulent B. bronchiseptica by intraperitoneal, intracerebral, or intranasal routes. The course of infection was compared among these routes, and the protective effect of vaccination was quantitatively analyzed. In ddN mice infected intraperitoneally with 1.8 x 108 cells (ca. 80 times the 50% lethal dose [LD50]) the organisms rapidly increased in the intraperitoneal fluid, spleen, and liver within few days and caused splenic atrophy, septicemia, and death. However, immunizations with 5 x 109 cells gave the mice a high agglutinin titer and suppressed the increase in the number of organisms. With four immunizations, the lungs and livers were clear within 3 days, and with one or two immunizations, they were clear within 7 days. These immunizations effectively protected the mice from death but did not protect them from splenic atrophy. In the intracerebral infection with 1.4 x 106 cells (ca. 1.2 x 105 LD50), the number of organisms rapidly increased in the brain and caused encephalitis, splenic atrophy, and death. However, four or five immunizations completely suppressed the increase in the brain and protected the mice from death and splenic atrophy. After intranasal infection with 4 x 106 cells (ca. 25 LD50), the organisms rapidly increased in the nasal cavity and lungs and caused pneumonia and death.

Electron Microscopic Observations on Tracheal Epithelia of Mice Infected with Bordetella bronchiseptica

“…The specific adherence of the organisms to ciliated epithelial cells has been shown by electron microscopy in tracheal organ cultures (4, 6, 10, 19, 20, 23-25, 32, 33). In a previous study (29), we observed that infection with a small dose of B. bronchiseptica was sufficient to colonize the respiratory epithelium for a long period of time.…”

“…Viable count. Immediately after the inoculations, the bacterial suspension was tested for viable cells by the method previously described (29). The infected tracheas of surviving mice were homogenized individually in a mortar with 2 ml of Casamino Acids diluent and a small amount of glass beads.…”

“…However, the mechanism by which these bacteria interact with ciliated epithelial cells, inducing tissue damage and ciliostasis, is not well understood. In previous studies, we demonstrated that a small number of B. bronchiseptica cells was sufficient to effectively colonize for a long time the upper and lower respiratory tracts of mice (29). In the present work, we employed this mouse model to observe in detail by scanning and transmission electron microscopes, the pathological changes on the ciliated epithelium of mouse tracheas caused by B. bronchiseptica infection.…”

Electron Microscopic Observations on Ciliated Epithelium of Tracheal Organ Cultures Infected with Bordetella bronchiseptica

“…In the experimental bordetellosis including B. pertussis in various animal models, it has been shown that bacteria superficially attach to the cilia of tracheal epithelium (2,3,7,(9)(10)(11)(12)15), and subsequently induce the selective destruction of ciliated cells. In a previous in vivo study (16), we demonstrated in mice that a rupture of the cell membrane of cilia, resulting in destruction of tracheal epithelia, is an initially important step of the pathogenesis of B. bronchiseptica subsequently after the colonization.…”

“…Viable count. The viable count of the bacterial suspension was done by the method previously described (15). places had completely disappeared (Fig.…”