Live tularemia vaccine but not proteins purified from Francisella tularensis can confer protection against lethal Listeria infection in mice.

Immunization of Balb/c mice with Francisella tularensis vaccine strain 15/10 conferred significant protection against subsequent listerial infection. Since immunostimulatory activities could apparently be relevant to surface components of the bacterium, a technique for purification of cell wall proteins was developed. The scheme designed consisted of Triton X-100 extraction with subsequent FPLC chromatography steps, and resulted in the isolation of homogeneous proteins with molecular masses of 54 kDa (pI = 6.7) and 82 kDa (pI = 5.3), and partially purified 50, 85 and 100 kDa components. It was shown that immunization with isolated proteins failed to protect mice against lethal Listeria monocytogenes infection. Possible reasons for failure are discussed.