Effect of transforming growth factor beta on experimental Salmonella typhimurium infection in mice.

ABSTRACT

We have investigated the effect of the in vivo administration of recombinant transforming growth factor beta (rTGF-beta) on the pathogenic mechanisms involved in Salmonella typhimurium experimental infection in mice. The protective response elicited by macrophages was induced by rTGF-beta1 by 2 days after experimental infection, as demonstrated by an increased NO production, while the humoral protective effect began with cytokine mRNA expression 2 days after the challenge and continued after 5 days with cytokine release and lymphocyte activation. We demonstrated that all mice who received rTGF-beta1 survived 7 days after infection. The number of bacteria recovered in the spleens and in the livers of rTGF-beta1-treated mice 2 and 5 days after infection was significantly smaller than that found in the same organs after phosphate-buffered saline (PBS) inoculation. Furthermore, 2 and 5 days after infection, splenic macrophages from rTGF-beta1-treated mice showed a greater NO production than did those from PBS-treated mice. The effect of rTGF-beta1 on S. typhimurium infection in mice was correlated with the expression of cell costimulatory CD28 molecules. Five days after S. typhimurium infection, the percentage of CD28(+)-expressing T cells in splenic lymphocytes from rTGF-beta1-treated mice increased with respect to that from control mice. Gamma interferon (IFN-gamma) mRNA was present in a greater amount in spleen cells from rTGF-beta1-treated mice after 2 days, although the intensity of the band decreased 5 days after the challenge. A similar pattern was obtained with the mRNAs for interleukin-1alpha (IL-1alpha), IL-6, TGF-beta, and inducible nitric oxide synthase, which showed greater expression in cells obtained from rTGF-beta1-treated and S. typhimurium-infected mice 2 days after challenge. The treatment with rTGF-beta1 induced an increase in IL-1alpha and IFN-gamma release in the supernatant of splenocyte cultures 5 days after the experimental infection with S. typhimurium. Moreover, we demonstrated that 5 days after infection, the IFN-gamma titer was significantly greater in the sera of rTGF-beta-treated mice than in those of PBS-treated mice. Also, hsp60 showed greater expression 2 days after the challenge in splenocytes from rTGF-beta1-treated mice. The role played by proinflammatory and immunoregulatory cytokines and by CD28 is discussed.