The preservation of Vi antigen in T.A.B.C. vaccine: With a note on combined active immunization with T.A.B.C. vaccine in tetanus formol-toxoid

Abstract

1. V strains of Bact. typhosum can be sterilized by means of merthiolate or colloidal silver without destructive effect on either the Vi or O antigens.2. Suspensions in physiological saline sterilized and preserved by the addition of either merthiolate or silver retain their property of stimulating Vi antibody formation in the rabbit for at least one year if stored at 0–2° C, but when stored at 23–25° C. this property is lost after 4 months' storage.3. The Vi antibody-stimulating property of a merthiolate-killed and preserved suspension in physiological saline is almost completely destroyed by an exposure of 5 days at 37° C. or 4 hr. at 60° C.4. Bact. typhosum bacilli killed with merthiolate or alcohol, and dried with acetone, show no loss of Vi antigen when stored in the dry state for 1 year at 23–25° C, or after 3 months at 37° C.5. Suspensions sterilized and preserved with merthiolate in 32% saline will withstand 50 days' storage at 37° C, or 7 months at 23–25° C, without significant loss of their Vi antibody-stimulating properties.6. Suspensions in 32% saline can be sterilized by an exposure to 60° C. for 2 hr., and even after 4 hr. exposure at this temperature, show no loss of Vi antigen content.7. Suspensions killed by merthiolate or alcohol, and preserved by the addition of 25% alcohol in physiological saline, failed to stimulate Vi antibody formation in the rabbit after being stored for 20 days at 37° C.8. The application of these findings to the production of a stable T.A.B.C. vaccine of enhanced immunological qualities is discussed.9. The effect of mixing Bact. typhosum with tetanus formol-toxoid has been examined, and the advisability of employing heat-killed-phenolized vaccine mixed with tetanus formol-toxoid for combined immunization against tetanus and typhoid infections is discussed.10. A suggested technique for the preparation, supply, and administration of two new types of T.A.B.C. vaccine is described.