Membrane-Bound TNF Induces Protective Immune Responses to M. bovis BCG Infection: Regulation of memTNF and TNF Receptors Comparing Two memTNF Molecules

Several activities of the transmembrane form of TNF (memTNF) in immune responses to intracellular bacterial infection have been shown to be different from those exerted by soluble TNF. Evidence is based largely on studies in transgenic mice expressing memTNF, but precise cellular mechanisms are not well defined and the importance of TNF receptor regulation is unknown. In addition, memTNF activities are defined for a particular modification of the extracellular domain of TNF but a direct comparison of different mutant memTNF molecules has not been done in vivo

Dominant-Negative Tumor Necrosis Factor Protects from Mycobacterium bovis Bacillus Calmette-Guérin (BCG) and Endotoxin-Induced Liver Injury without Compromising Host Immunity to BCG and Mycobacterium tuberculosis

BackgroundTumor necrosis factor (TNF) is associated with the development of inflammatory pathologies. Antibodies and soluble TNF (solTNF) receptors that neutralize excessive TNF are effective therapies for inflammatory and autoimmune diseases. However, clinical use of TNF inhibitors is associated with an increased risk of infections MethodsA novel dominant-negative (DN) strategy of selective TNF neutralization, consisting of blocking solTNF while sparing transmembrane TNF (tmTNF), was tested in mouse models of mycobacterial infection and acute liver inflammation. XENP1595, a DN-TNF biologic, was compared with etanercept, a TNF receptor 2 (TNFR2)-IgG1 Fc fusion protein that inhibits murine solTNF and tmTNF ResultsXENP1595 protected mice from acute liver inflammation induced by endotoxin challenge in Mycobacterium bovis bacillus Calmette-Guérin (BCG)-infected mice, but, in contrast to etanercept, it did not compromise host immunity to acute M. bovis BCG and Mycobacterium tuberculosis infections in terms of bacterial burden, granuloma formation, and innate immune responses ConclusionsA selective inhibitor of solTNF efficiently protected mice from acute liver inflammation yet maintained immunity to mycobacterial infections. In contrast, nonselective inhibition of solTNF and tmTNF suppressed immunity to M. bovis BCG and M. tuberculosis. Therefore, selective inhibition of solTNF by DN-TNF biologics may represent a new therapeutic strategy for the treatment of inflammatory diseases without compromising host immunit

Differential Effects of Total and Partial Neutralization of Tumor Necrosis Factor on Cell-Mediated Immunity to Mycobacterium bovis BCG Infection

The effects of total and partial inhibition of tumor necrosis factor (TNF) on sensitivity to Mycobacterium bovis BCG infection were investigated by using transgenic mice in which hepatocytes produced different amounts of human soluble TNF receptor 1 (sTNFR1) fused to the Fc fragment of human immunoglobulin G3 that could be detected in the serum. Transgenic mice expressing high serum levels of sTNFR1, neutralizing all circulating TNF, failed to develop differentiated granulomas and bactericidal mechanisms, and they succumbed to BCG infection. sTNFR1 transgenic mice did not activate BCG-induced Th1-type cytokines early in infection, but uncontrolled cytokine release was found late in infection. In this work we also evaluated the effect of partial inhibition of TNF on resistance to BCG infection. Transgenic mice expressing low levels of sTNFR1 were protected against BCG infection, and they developed increased bactericidal mechanisms, such as enhanced inducible nitric oxide synthase activity, increased macrophage activation, and showed higher numbers of liver granulomas early in infection compared to their negative littermates. Our data suggest that while total inhibition of TNF prevented BCG-induced cell-mediated immune responses, partial inhibition of TNF could contribute to macrophage activation, induction of bactericidal mechanisms, and granuloma formation in the early phase of BCG infection

Fat diet and alcohol-induced steatohepatitis after LPS challenge in mice: role of bioactive TNF and Th1 type cytokines

Obesity with insulin resistance and alcohol are the most frequent causes of steatohepatitis. This work investigates the contribution of bioactive TNF and Th1 type cytokines in a mouse model of steatohepatitis induced by FAT alone or FAT+EtOH and endotoxin. The extent of liver injury and cytokine activation induced by endotoxin in chronic FAT-fed mice, FAT+EtOH-fed mice, or mice fed standard chow were analyzed. Endotoxin administration to either FAT-fed or FAT+EtOH-fed mice increased serum ALT and AST compared to standard chow mice. Immunoreactive TNF was strongly activated by LPS in FAT-fed and FAT+EtOH-fed mice which presented the highest levels, but low levels were found in standard chow mice. In contrast, bioactive TNF was only present in serum of FAT-fed and in particular the highest levels were found in FAT+EtOH-fed mice. Moreover, soluble TNFR2 but not TNFR1 was found in lower amounts in serum of FAT+EtOH-fed mice compared to FAT-fed mice. Steatohepatitis was associated with increased IL-6, IFN-gamma, and iNOS mRNA and proteins. Data show that a moderately FAT diet and low-dose EtOH concur to generate steatohepatitis and TNF liver expression after LPS. In this model, changes in the regulation of TNF are associated with increased expression of IL-6, IFN-gamma, and iNOS

Soluble TNF, but not membrane TNF, is critical in LPS-induced hepatitis

BACKGROUND & AIMS: : Bacillus Calmette-Guerin (BCG) infection causes hepatic injury following granuloma formation and secretion of cytokines which renders mice highly sensitive to endotoxin-mediated hepatotoxicity. Tumor necrosis factor (TNF) is required for granuloma formation and is one of the most important cytokines in liver injury. TNF inhibitors are effective therapies for inflammatory diseases. However, clinical use of non-selective TNF inhibitors is associated with an increased risk of infections. This work investigates the differential roles of soluble TNF (solTNF) and membrane TNF (memTNF) in BCG infection, BCG/LPS- and D-GALN/LPS-induced liver injury. METHODS: We have used both genetic and pharmacologic approaches and analyzed liver injury, TLR4, cytokine and iNOS activation induced by BCG, BCG/LPS and D-GALN/LPS. RESULTS: BCG infection-induced liver injury is seen in wild-type mice but not in TNF(-/-), memTNF knock-in (KI), and sTNFR1-Fc transgenic mice. Severity of BCG-induced liver injury is correlated with BCG-granuloma number and hepatic expression of TLR4 and iNOS. In addition, protection from liver damage caused by BCG/LPS or D-GALN/LPS administration was observed in TNF(-/-), memTNF KI and sTNFR1-Fc transgenic mice. To extend the genetic findings, we then evaluated whether selective pharmacological inhibition of solTNF by dominant-negative (DN)-TNF neutralization and non-selective inhibition of solTNF and memTNF by anti-TNF antibodies and etanercept (TNFR2-IgG1) can protect the mice from liver injury. Both selective and non-selective inhibition of solTNF protected mice from BCG/LPS and D-GALN/LPS-induced liver damage. CONCLUSIONS: These data suggest that memTNF is not mediating liver injury and that selective inhibition of solTNF sparing memTNF may represent a new therapeutic strategy to treat immune-mediated inflammatory liver diseases

Transmembrane TNF Induces an Efficient Cell-Mediated Immunity and Resistance to Mycobacterium bovis

The contribution of a transmembrane (Tm) form of TNF to protective immunity against Mycobacterium bovis bacillus Calmette-Guérin (BCG) was studied in transgenic (tg) mice expressing a noncleavable Tm TNF but lacking the TNF/lymphotoxin-alpha (LT-alpha) locus (Tm TNF tg mice). These mice were as resistant to BCG infection as wild-type mice, whereas TNF/LT-alpha(-/-), TNF(-/-), and LT-alpha(-/-) mice succumbed. Tm TNF tg mice developed granulomas of smaller size but at 2- to 4-fold increased frequencies compared with wild-type mice. Granulomas were mainly formed by monocytes and activated macrophages expressing Tm TNF mRNA and accumulating acid phosphatase. NO synthase 2 activation as a key macrophage bactericidal mechanism was low during the acute phase of infection in Tm TNF tg mice but was still sufficient to limit bacterial growth and increased in late infection. While infection with virulent Mycobacterium tuberculosis resulted in very rapid death of TNF/LT-alpha(-/-) mice, it also resulted in survival of Tm TNF tg mice which presented an increase in the number of CFU in spleen (5-fold) and lungs (10-fold) as compared with bacterial load of wild-type mice. In conclusion, the Tm form of TNF induces an efficient cell-mediated immunity and total resistance against BCG even in the absence of LT-alpha and secreted TNF. However, Tm TNF-mediated protection against virulent M. tuberculosis infection can also be efficient but not as strong as in BCG infection, in which cognate cellular interactions may play a more predominant role in providing long-term surveillance and containment of BCG-infected macrophages

Transmembrane TNF induces an efficient cell-mediated immunity and resistance to Mycobacterium bovis bacillus Calmette-Guérin infection in the absence of secreted TNF and lymphotoxin-alpha.

The contribution of a transmembrane (Tm) form of TNF to protective immunity against Mycobacterium bovis bacillus Calmette-Guérin (BCG) was studied in transgenic (tg) mice expressing a noncleavable Tm TNF but lacking the TNF/lymphotoxin-alpha (LT-alpha) locus (Tm TNF tg mice). These mice were as resistant to BCG infection as wild-type mice, whereas TNF/LT-alpha(-/-), TNF(-/-), and LT-alpha(-/-) mice succumbed. Tm TNF tg mice developed granulomas of smaller size but at 2- to 4-fold increased frequencies compared with wild-type mice. Granulomas were mainly formed by monocytes and activated macrophages expressing Tm TNF mRNA and accumulating acid phosphatase. NO synthase 2 activation as a key macrophage bactericidal mechanism was low during the acute phase of infection in Tm TNF tg mice but was still sufficient to limit bacterial growth and increased in late infection. While infection with virulent Mycobacterium tuberculosis resulted in very rapid death of TNF/LT-alpha(-/-) mice, it also resulted in survival of Tm TNF tg mice which presented an increase in the number of CFU in spleen (5-fold) and lungs (10-fold) as compared with bacterial load of wild-type mice. In conclusion, the Tm form of TNF induces an efficient cell-mediated immunity and total resistance against BCG even in the absence of LT-alpha and secreted TNF. However, Tm TNF-mediated protection against virulent M. tuberculosis infection can also be efficient but not as strong as in BCG infection, in which cognate cellular interactions may play a more predominant role in providing long-term surveillance and containment of BCG-infected macrophages

A role for lymphotoxin beta receptor in host defense against Mycobacterium bovis BCG infection

To investigate the role of membrane lymphotoxin (LT)alpha1 / beta2 and its LTbeta receptor (LTbetaR) in the protective immune response to Mycobacterium bovis bacillus Calmette-Guerin (BCG) infection, we have used a soluble fusion molecule (LTbetaR-IgG1). LTbetaR-Ig treatment interferes with granuloma formation mainly in the spleen by inhibiting macrophage activation and nitric oxide synthase activity. In addition, a large accumulation of eosinophils was observed in the spleen of LTbetaR-Ig-treated infected mice. Decreased blood levels of IFN-gamma and increased IL-4 were also observed, suggesting that the LTbetaR pathway is important in BCG infection to favor a Th1 type of immune response. The treatment of transgenic mice expressing high blood levels of a soluble TNFR1-IgG3 fusion protein with LTbetaR-Ig resulted in a still higher sensitivity to BCG infection, and extensive necrosis in the spleen. In conclusion, these results suggest that the LTbetaR and the TNFR pathways are not redundant in the course of BCG infection and protective granuloma formation: the LTbetaR pathway appears to be important in spleen granuloma formation, whereas the TNFR pathway has a predominant role in other tissues

In Vitro

Sclerocarya birrea is a medicinal plant used for the treatment of inflammatory- and bacterial-related diseases. The present study investigated in vitro and in vivo the effects of the stem bark methanol extract of S. birrea. Nitrite, TNF, IL-1beta, IL-6 and IL-12p40 production by bone marrow-derived macrophages (BMDM) pre-incubated with or without S. birrea, and stimulated with Lipopolysaccharide (LPS) or infected with live Mycobacterium bovis Bacillus Calmette Guerin (BCG) was evaluated. S. birrea extract inhibited, in a concentration-dependent manner, nitrite, TNF, IL-1beta, IL-6 and IL-12p40 production by BMDM stimulated with LPS or infected with live BCG. The iNOS expression was reduced by S. birrea after stimulation of BMDM with LPS. In addition, S. birrea inhibited the nuclear factor kB (NF-kB) activation by both LPS and BCG. The effects of the plant extract were also evaluated in an in vivo model of liver injury induced by D-galactosamine/LPS (D-GalN/LPS) administration in mice. S. birrea limited D-GalN/LPS-liver injury as assessed by a reduction in transaminases and TNF, IL-1beta, IL-6 serum levels, and translocation of NF-kB to the nucleus. Taken together, our data indicate that stem bark methanol extract of S. birrea possesses anti-inflammatory properties by inhibiting NF-kB activation and cytokine release induced by inflammatory or infectious stimuli