A single intraperitoneal administration of Bordetella pertussis vaccine produced within a few days an increased resistance in mice against intracerebral infection with B. pertussis strain 18–323 such as has previously been described by Evans and Perkins as early or interference immunity.
Intraperitoneal administration of the endotoxin of B. pertussis induced a relatively transient resistance against intracerebral infection with Salmonella typhi strain Ty2, but not against intracerebral infection with B. pertussis organisms.
When the treatment was made intracerebrally however, heterologous and homologous endotoxins as well as a synthetic double-stranded RNA complex of polyriboinosinic and polyribocytidylic acids (poly I.C) could increase the resistance of mice against intracerebral infection with B. pertussis organisms. In brains of animals thus treated, evident suppression of bacterial growth comparable to that in a passive immunity experiment was seen.
By the use of brain extract prepared from mice or rats treated intracerebrally with heterologous endotoxin, the non-specific resistance could be successfully induced in mice.
To substantiate any possible relation of such a non-specific resistance induced by endotoxins to the early immunity seen after the intraperitoneal injection of B. pertussis vaccine further efforts are necessary.