Immunization with recombinant Corynebacterium pseudotuberculosis heat-shock protein (Hsp)-60 is able to induce an immune response in mice, but fails to confer protection against infection

Corynebacterium pseudotuberculosis is the etiological agent of caseous lymphadenitis (CLA), a chronic small ruminant's disease. C. pseudotuberculosis Hsp60 expressed in E. coli was purified and tested as a vaccine candidate against CLA. Immunization of BALB/c mice with recombinant Hsp60 (rHsp60) induced a significant anti-Hsp60 IgG re- sponse, with greater production of IgG1 than of IgG2a. Cell-mediated immune responses induced by immunization were characterized by elevated production of gamma interferon (IFN- ) and interleukin (IL)-10, while IL-4 concentrations were not significantly increased. Otherwise, mice challenged with 10 6 c.f.u. of a virulent C. pseudotuberculosis strain devel- oped abscesses and other signs of morbidity at the site of inoculation. The rate of survival of the animals immunized with rHsp60 was slightly higher than that of mice immunized with PBS; however, all the animals died within two weeks after challenge. We concluded that subcutaneous administration of rHsp60 does not induce effective protection against intrape- ritoneal infection with C. pseudotuberculosis.