THE INFLUENCE OF SUBLETHAL X-IRRADIATION ON THE IMMUNITY OF GUINEA PIGS ADMINISTERED LIVE TULAREMIA VACCINE
ARMY BIOLOGICAL LABS FREDERICK MD
Pagination or Media Count:
Reports from this laboratory have demonstrated that exposure of guinea pigs to sublethal X-irradiation three days before the administration of innocuous respiratory doses of live tularemia vaccine resulted in maximal mortality 23 per cent in comparison with other X-irradiation schedules investigated. However, agglutinin production and development of immunity was not markedly altered in these animals by the X-irradiation procedure. The present study was performed to determine if the subcutaneous route of vaccination of irradiated animals would result in a decrease in the mortality rate and yet provide resistance to subsequent virulent challenge. Guinea pigs received 140 roentgens r of whole-body X-irradiation at intervals ranging from 12 days before to 3 days after subcutaneous vaccination with 10exp5 viable cells of live tularemia vaccine. Serological studies of animals from each group were performed at nine post-vaccination intervals. The over-all mortality rate attributable to the combined irradiation-vaccination was fourfold less than that observed among irradiated animals vaccinated by the respiratory route. Three weeks following vaccination 20 animals of each irradiated-vaccinated group and the various control groups were challenged by a respiratory exposure to virulent P. tularensis SCHU S4. The serological study deorstrated that there was no significant inhibition of agglutinin production among the irradiated-vaccinated groups, regardless of the time of irradiation. All vaccinated animals, both irradiated and nonirradiated, developed comparable resistance to virulent challenge.