A study on bacteriological lines of the antigens derived from Bact. dysenteriae Shiga and of their antisera in protective tests against the living organisms

Abstract

1. An examination by bacteriological methods has been made of the antigens present in the washed bacilli of smooth Shiga strains and certain derived variants, including the rough type.2. The washed formol-killed smooth bacilli kill mice only in massive doses of the order of 5000 millions, suggesting death from protein shock; no protection against a fatal issue is afforded by antibacterial sera. This finding is discussed in relation to recently acquired information obtained by chemical methods on the occurrence of a specific enterotropic toxin in the smooth bacilli, as distinct from the enterotropic toxin present together with a neurotoxin in autolysates of smooth and rough bacilli.3. Antibacterial sera prepared by immunization with the smooth antigen have high protective value against infection with the living smooth bacilli but not against pure toxin, whereas purely antitoxic sera have no value against infection with the living smooth bacilli.4. From experiments so far performed, protection against infection with the living rough bacilli has been afforded only by sera prepared from formol-killed rough bacilli and from acetone-killed rough bacilli.5. From findings reported in (3) inferences are drawn with regard to improvements in the manufacture of dysentery serum for use in man, both prophylactically and therapeutically.6. The presence of two distinct antigens in the Shiga bacillus has been clearly demonstrated, since the protective values of their corresponding antisera are sharply defined, and do not overlap. The existence of the neurotoxin as a separate entity, unrelated to the smooth ‘endotoxin’, has also been shown by its derivation from a completely ‘rough’ strain, but though the smooth somatic antigen gives rise to a highly protective antiserum, in these experiments it has not been shown, per se, to be a specific toxin.The writer wishes to thank Sir John. Ledingham and Dr G. F. Petrie for their advice and criticism during this work, and Dr D. W. Henderson, by whom the experiments were first suggested.