Immune mechanism in Pasteurella multocida-infected mice

Various immunizing procedures were tested for their effect on the growth of Pasteurella multocida in specific pathogen-free CD-1 mice. Two injections with killed vaccine incorporated into Freund complete adjuvant gave excellent protection against parenteral challenge, but less to control the growth of an aerogenic inoculum. Protection with adjuvant-treated preparation was always superior to that seen with non-adjuvant-treated vaccines. A killed saline-suspended vaccine introduced aerogenically marginally increased resistance to small (2 to 5 mean lethal doses) aerogenic challenges. Live mycobacterium bovis (BCG) vaccine immunopotentiated a single dose of heat-killed P. multocida vaccine in terms of the protective immune response against a subsequent footpad challenge. Hyperimmune mouse serum, administered intraperitoneally, intramuscularly, or intravenously 1 to 7 days prior to subcutaneous challenge with 500 to 5,000 P. multocida, was highly protective. Mice injected in the thigh with 0.2 ml of hyperimmune serum prior to footpad challenge frequently developed a severe inflammatory response with local swelling within 48 h; these lesions often became severly abscessed with time. The passively protected, footpad-infected mice developed active immunity against a subsequent challenge given into the opposite footpad.