[Oral intestinal vaccines and their effectiveness in the rabbit intestinal loop model. III. Effectiveness of oral immunization with live and chemical vaccines].

The effectiveness of the oral immunization of rabbits was manifested by a decrease in the number of virulent Shigella penetrating enterocytes, by the limited proliferation of bacteria in the epithelium and by the less pronounced ulcerous inflammation of the mucous membrane in the intestinal loops even after infection with large doses (10(9) bacteria). In electron microscopy this was manifested by the destruction of Shigella cells in heterophagosomes formed in enterocytes. The degree of fluid accumulation in the injected intestinal loops of immunized animals did not correlate either with the manifest morphological changes, or with the level of serum antibodies. The effectiveness of immunization was more pronounced after the introduction of smaller doses of virulent Shigella (10(7)-10(8) bacteria), when even Boivin's vaccine, though less effective, led to a decrease in the number of Shigella cells penetrating enterocytes, prevented their proliferation in the epithelium, its destruction and the development of inflammation.