A recombinant (r)-Salmonella typhimurium aroA
vaccine strain was constructed which secretes the naturally somatic
protein of Listeria monocytogenes,
superoxide dismutase (SOD), by the HlyB/HlyD/TolC export machinery.
Vaccine efficacy of the SOD-bearing carrier strain was compared with that of the p60-secreting construct, S. typhimurium p60s (J. Hess, I. Gentschev, D. Miko, M. Welzel, C. Ladel, W. Goebel, and S. H. E. Kaufmann, Proc. Natl. Acad. Sci. USA 93:1458-1463, 1996). Vaccination 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, the 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 origin. Moreover, they suggest that the HlyB/HlyD/TolC-based
antigen delivery system with attenuated Salmonella spp. as the carrier is capable of potentiating the immune response against foreign
proteins independent from their immunogenicity in and display by the natural host.