STUDIES ON INFECTION AND IMMUNITY IN EXPERIMENTAL TYPHOID FEVER

Abstract

Chimpanzees recovered from typhoid fever induced by ingestion of large numbers of phage-type T S. typhosa were rechallenged approximately a year and a half later with a like number of a phage-type E₁ strain. Control animals exhibited febrile responses, bacteriemia, and other significant laboratory and clinical findings, including increases in C-reactive protein levels and sedimentation rates. All of the previously infected and recovered chimpanzees were negative with respect to the aforementioned observations, and appeared to have resisted significant re-infection. On the other hand, recovery from typhoid fever induced by smaller numbers of S. typhosa failed to protect completely against rechallenge with larger numbers of these organisms.