Effect of ionizing radiation of the antigenic composition of typhoid bacteria

Changes in the antigenic composition of typhoid bacteria occurring during the exposure of microbial suspension to different doses of gamma irradiation [Co60] ranging between 0.5 and 3.0 Mrad were studied. Immunoelectrophoresis in agar was used to determine the antigenic composition of different samples of irradiated bacteria. The antigenic composition of bacteria irradiated with doses up to 2.5 Mrad was found to be similar to that of non-irradiated bacteria. Antigens demonstrated by means of Vi, H and O ontisera are preserved in these bacteria. However, all irradiated bacteria in general slightly differ from non-irradiated bacteria; this is manifest in a different configuration and position of the precipitation lines in the cathodic part of the immunophoreograms. The content of the component migrating rapidly towards the cathode, evidently the O antigen in the R form, in the irradiated bacteria increases with the dose of radiation. No new serologically active substances, non-existent in non-irradiated bacteria, were found to appear in the process of irradiation.