Studies on the immunizing capacity of orally administered particulate antigens. I. The efficiency of killed Bordetella pertussis cells.

The single i.p. injection of 2.5 times 10-8 killed B. pertussis cells protected 23 out of a group of 24 NMRI mice (95.8%) against the subsequent intracerebral infection, whilst 13 out of 24 mice (54.2%) survived the intracerebral challenge with virulent B. pertussis cells after prior oral administration of 2.5 times 10-11 killed B. pertussis cells, as demonstrated by the mouse protection test. Similar treatment with non-specific substances, such as egg white and saline, did not result in any increase of resistance. Systemic anaphylactic hypersensitivity to bovine serum albumin could also be achieved, when either both the protein antigen and the B. pertussis vaccine were given by the oral route or when the B. pertussis vaccine was injected intraperitoneally into mice which had received the soluble protein antigen by the oral route. Such effects were not produced at all in the reverse situation, when the B. pertussis vaccine was orally administered in mice, which were given the soluble protein antigen by the intraperitoneal route. After oral inoculation of 6 times 10-11 killed B. pertussis cells neither splenomegaly nor blood lymphocytosis became detectable. It is still unknown, in which manner the orally administered B. pertussis vaccine effects protection against the intracerebral infection with virulent bacteria as well as susceptibility for systemic anaphylaxis. The data presented do not favor the view that those effects are due to the phenomenon of persorption.