PROTECTIVE EFFECT ON LEISHMANIA-MAJOR INFECTION OF MIGRATION-INHIBITORY FACTOR, TNF-ALPHA, AND IFN-GAMMA ADMINISTERED ORALLY VIA ATTENUATEDSALMONELLA-TYPHIMURIUM

The genes encoding murine macrophage migration inhibitory factor (MIF) , IL-2, IFN-gamma or TNF-alpha were cloned individually into an expres sion plasmid under the control of the inducible promoter nirB and tran sfected into the aroA(-)aroD(-) deletion mutant strain of Salmonella t yphimurium (BRD509), These S, typhimurium derivatives (henceforward ca lled constructs and termed GIDMIF, GIDIL2, GIDIFN and GIDTNF) expresse d their respective cytokines in vitro under anaerobic conditions and s tably colonized BALB/c mice up to 14 days after oral administration, T he highly susceptible BALB/c mice that had received the constructs ora lly and that had been subsequently infected via the footpad with Leish mania major, developed significantly reduced disease compared with con trol mice administered the untransfected Salmonella strain (BRD509), I mportantly, a combination of GIDMIF, GIDIFN, and GIDTNF administered o rally after L, major infection was able to significantly limit lesion development and reduced parasite loads by up to three orders of magnit ude, Spleen and lymph node cells of mice administered this combination expressed markedly higher levels of inducible nitric oxide synthase ( iNOS) compared with those from mice receiving an equivalent dose of th e control strain of Salmonella (BRD509), These data therefore demonstr ate the feasibility of therapeutic treatment in an infectious disease model using cytokines delivered by attenuated Salmonella, The protecti ve effect observed correlates with the induction of inducible nitric o xide synthase in vivo.