Studies in Active Immunization Against Undulant Fever

Abstract

Summary Mice are susceptible to virulent Br. abortus and Br. melitensis upon intraabdominal inoculation with large numbers and succumb to peritonitis with an associated septicemia. They have been found suitable for protective tests with the sera of rabbits immunized with a heat-killed vaccine of Br. abortus. The sera of rabbits immunized simultaneously by subcutaneous injections of heat-killed vaccines of B. typhosus and Br. abortus showed as much agglutinin and protective antibody for B. typhosus as did those immunized with the typhoid vaccine alone. Rabbits immunized simultaneously with subcutaneous injections of vaccines of heat-killed Br. abortus and B. typhosus produced agglutinins and bacteriotropins for brucella to the same degree as those immunized with brucella vaccine alone. The sera of normal rabbits and of those immunized with typhoid vaccine are occasionally very slightly protective for mice inoculated intraabdominally with lethal doses of Br. abortus and Br. melitensis. The sera of rabbits immunized with a heat-killed vaccine of Br. abortus contained larger amounts of protective antibody for mice inoculated intraabdominally with lethal doses of virulent Br. abortus and much larger amounts for virulent Br. melitensis. The sera of rabbits immunized simultaneously with heat-killed vaccines of Br. abortus and B. typhosus were found to contain as much protective antibody against virulent Br. abortus and Br. melitensis as those immunized with the brucella vaccine alone. The possibility of effective simultaneous immunization of human beings against typhoid and undulant fevers with a mixed heat-killed vaccine is discussed.