Preparation and Evaluation of an Irradiated Toxoid from the Toxin of Shigella Dysenteriae

Abstract

By means of ultraviolet irradiation of a filtered autolysate of a culture of Shigella dysenteriae (Shiga) the neurotoxin (exotoxin) can be rendered completely non-toxic for mice and rabbits. This detoxified material is still antigenic. Mice vaccinated with it are resistant to injections of the toxin and also to infection with living Shiga bacteria. Rabbits immunized with these toxoids develop measurable amounts of antitoxin. Serum from them protects mice against the toxin and also to a less constant degree, against infection with living culture. There is still a factor, or factors, in these toxoids which can cause a moderately severe reaction when injected into man. The filtered autolysates which were the basis of these studies have been made from whole cells and have contained both exotoxin (neurotoxin) and endotoxin. The endotoxin, which we have found difficult to demonstrate in animals except as an antigen, is probably responsible for the toxic reaction in man. Complete detoxification for man of these antigens by ultraviolet irradiation has not yet been accomplished.