PROTECTION AGAINST MURINE LISTERIOSIS BY AN ATTENUATED RECOMBINANT SALMONELLA-TYPHIMURIUM VACCINE STRAIN THAT SECRETES THE NATURALLY SOMATIC ANTIGEN SUPEROXIDE-DISMUTASE

A recombinant (r)-Salmonella typhimurium aroA vaccine strain was const ructed which secretes the naturally; somatic protein of Listeria monoc ytogenes, superoxide dismutase (SOD), by the HlyB/HlyD/TolC export mac hinery, Vaccine efficacy of the SOD-bearing carrier; strain was compar ed with that of the p60-secreting construct, S. typhimurium p60s (J. H ess, I, Gentschev, D. Mike, hi. Welzel, C. Ladel, W. Goebel, and S. Fl , E. Kaufmann, Proc, Natl, Acad, Sci, USA 93:1458-1463, 1996), Vaccina tion of mice with both constructs induced protection against a lethal challenge with the intracellular pathogen, L. monocytogenes. While the somatic Listerial antigen, SOD, is immunologically uncharacterized, t he naturally secreted protein of L. monocytogenes, p60, is known to be highly immunogenic. Our data emphasize the high vaccine potential of r-Salmonella constructs secreting antigens of somatic or secreted orig in, Moreover, they suggest that the HlyB/HlyD/TolC-based antigen deliv ery system with attenuated Salmonella spp. as the carrier is capable o f potentiating the immune response against foreign proteins independen t from their immunogenicity in and display by the natural host.