Background Tuberculosis remains one of the world's deadliest transmissible diseases despite the widespread use of BCG. MTBVAC is a new live tuberculosis vaccine based on a genetically attenuated phoP-/fadD26-deletion mutant of M. tuberculosis that expresses most antigens present in human isolates in contrast to BCG. Methods We conducted this randomized, double-blind, controlled phase I study at CHUV, Lausanne, Switzerland, to compare MTBVAC to BCG in healthy, PPD-negative adults. Primary outcome was safety in all vaccinated participants. Secondary outcome included whole blood cell mediated immune response to live MTBVAC and BCG as well as interferon-gamma release assay (IGRA) on peripheral blood mononuclear cells. Volunteers fulfilling the inclusion criteria were randomly allocated (on a 3:1 basis) in a dose-escalation manner to three cohorts. Each cohort included 9 subjects who were injected with MTBVAC 5x10 3 , 5x10 4 , or 5x10 5 colony forming units (CFU) in 0.1 mL and 3 subjects with BCG (single dose of 5x10 5 CFU in 0.1 mL). Each subject received a single intradermal injection in the non-dominant arm starting with the lowest MTBVAC dose. Findings Thirty-six volunteers were recruited. Vaccination with MTBVAC (5x10 3 , 5x10 4 , 5x10 5 CFU/0.1mL) was as safe as with BCG, and did not induce serious adverse events. All individuals were IGRA negative at the end of follow-up (D210). After whole blood stimulation with live MTBVAC or BCG, MTBVAC was immunogenic in a dosedependent manner. At the same dose level as BCG (5x10 5 CFU), although no

Following infection with the protozoan parasite Leishmania major, C57BL/6 mice develop a small lesion that heals spontaneously. Resistance to infection is associated with the development of CD4 ؉ Th1 cells producing gamma interferon (IFN-␥) and tumor necrosis factor (TNF), which synergize in activating macrophages to their microbicidal state. We show here that C57BL/6 mice lacking both TNF and Fas ligand (FasL) (gld TNF ؊/؊ mice) infected with L. major neither resolved their lesions nor controlled Leishmania replication despite the development of a strong Th1 response. Comparable inducible nitric oxide synthase (iNOS) activities were detected in lesions of TNF ؊/؊ , gld TNF ؊/؊ , and gld mice, but only gld and gld TNF ؊/؊ mice failed to control parasite replication. Parasite numbers were high in gld mice and even more elevated in gld TNF ؊/؊ mice, suggesting that, in addition to iNOS, the Fas/FasL pathway is required for successful control of parasite replication and that TNF contributes only a small part to this process. Furthermore, FasL was shown to synergize with IFN-␥ for the induction of leishmanicidal activity within macrophages infected with L. major in vitro. Interestingly, TNF ؊/؊ mice maintained large lesion size throughout infection, despite being able to largely control parasite numbers. Thus, IFN-␥, FasL, and iNOS appear to be essential for the complete control of parasite replication, while the contribution of TNF is more important in controlling inflammation at the site of parasite inoculation.In the experimental murine model of infection with the intracellular protozoan Leishmania major, susceptibility to infection has been correlated with the development of lesions associated with a Th2 type of immune response, while healing of lesions in resistant mice has been correlated with the development of a Th1 type of immune response (reviewed in reference 27). The resolution of lesions has been shown to involve several factors contributing to the killing of L. major within macrophages. The most efficient mechanism of parasite destruction involves the production of gamma interferon (IFN-␥) by CD4 ϩ Th1 cells, which induces the synthesis of inducible nitric oxide synthase (iNOS), generating the production of reactive nitrogen radicals toxic for the intracellular parasite (reviewed in reference 4). Tumor necrosis factor (TNF) has also been shown to be involved in parasite killing in a process that depends on NO production, and endogenously produced TNF has been reported to be necessary for NO production by macrophages in vitro (3,12,17,33).The importance of TNF in the control of infection with Leishmania has been studied extensively, but its exact role remains unclear. Mice resistant to infection with L. major were shown to produce significant amounts of TNF in their draining lymph nodes during the course of infection, while no TNF was detectable in susceptible animals (35). Injections of recombinant human TNF (rhTNF) into either resistant or susceptible strains of mice had a therapeutic effect on the co...

Upon infection with the protozoan parasite Leishmania major, susceptible BALB/c mice develop unhealing lesions associated with the maturation of CD4(+)Th2 cells secreting IL-4. In contrast, resistant C57BL/6 mice heal their lesions, because of expansion and secretion of IFN-gamma of CD4(+) Th1 cells. The Fas-FasL pathway, although not involved in Th cell differentiation, was reported to be necessary for complete resolution of lesions. We investigate here the role of IFN-gamma and IL-4 on Fas-FasL nonapoptotic signaling events leading to the modulation of macrophage activation. We show that addition of FasL and IFN-gamma to BMMø led to their increased activation, as reflected by enhanced secretion of TNF, IL-6, NO, and the induction of their microbicidal activity, resulting in the killing of intracellular L. major. In contrast, the presence of IL-4 decreased the synergy of IFN-gamma/FasL significantly on macrophage activation and the killing of intracellular L. major. These results show that FasL synergizes with IFN-gamma to activate macrophages and that the tight regulation by IFN-gamma and/or IL-4 of the nonapoptotic signaling events triggered by the Fas-FasL pathway affects significantly the activation of macrophages to a microbicidal state and may thus contribute to the pathogenesis of L. major infection.