Phenotypic and functional characterization of lung resident lymphocytes of BCG vaccinated mice

Mycobacterium tuberculosis (Mtb) remains to be a leading cause of morbidity and mortality, causing an estimated 1.3 million deaths annually. It is known that intranasal Mycobacterium bovis Bacille Calmette-Guérin (BCG) vaccination in mice has proven to provide superior protection against pulmonary TB, as compared to parenterally administered BCG. In the current study, we determined the phenotype and function of lung-resident lymphocytes in intranasally BCG vaccinated mice. C57BL/6 mice were vaccinated intranasally with live-attenuated BCG and lung lymphocytes were isolated and stained for immunophenotyping via flow cytometry at 24, 48, and 72 hours post-vaccination. At 48 hours post-vaccination, we have observed an expansion of CD69+, CD103+, and CD69+CD103+ lymphocytes within the lung of vaccinated mice. Studies are underway to determine the phenotype and function of lung-resident lymphocyte subsets and their expansion capacity at three months after BCG vaccination and Mtb infection.

Ornithine-A urea cycle metabolite enhances autophagy and controls Mycobacterium tuberculosis infection

Alveolar macrophages (AMs) are the first cells encountered by TB pathogen and serve as the primary defense against Mycobacterium tuberculosis (Mtb) in the lungs. Studies have shown that liver macrophages (Kupffer cells; KCs) can control Mtb growth but, it is not clear how KCs completely eliminate mycobacterial infections. Thus, identification of these mechanisms will facilitate the development of immunomodulatory strategies to boost AM-mediated immunity to Mtb. In the current study, we compared Mtb growth in murine AMs, peritoneal (PMs), liver macrophages (Kupffer cells; KCs) and bone marrow-derived monocytes (BDMs). KCs restricted Mtb growth more efficiently than all other macrophages and monocytes despite equivalent infections. Differences in Mtb growth restriction were not due to differences in cytokine production, expression of Toll-like receptors 2 and 4, M1/M2 paradigm or apoptosis. We provide evidence that the enhanced autophagy efficiently restricts Mtb growth in KCs using flow cytometry, western blot, RT-PCR and confocal microscopy. A metabolomic comparison of Mtb-infected macrophages by liquid chromatography mass spectrometry indicated that ornithine (VIP=1.8) and imidazole (VIP=1.6) were two top-scoring metabolites found in Mtb-infected KCs and that acetylcholine was top-scoring in Mtb-infected AMs. Ornithine and imidazole inhibited Mtb growth in AMs by enhancing AMPK mediated autophagy whereas imidazole directly killed Mtb by reducing cytochrome P450 activity. Intranasal delivery of ornithine or imidazole or together restricted Mtb growth in Mtb-infected mouse lungs. Our study demonstrates that the metabolic differences in Mtb-infected AMs and KCs leads to differences in the restriction of Mtb growth.

BCG vaccination reduces the mortality of Mycobacterium tuberculosis-infected type 2 diabetes mellitus (T2DM) mice through the induction of CXCR3+ T-regulatory cells

Diabetes is a significant risk factor for the development of active tuberculosis. In this study, we used mouse model of Streptozotocin/Nicotinamide (STZ/NA) induced non-obese type 2 diabetes mellitus (T2DM) to determine the effect of prior BCG vaccination on survival and immune responses to Mycobacterium tuberculosis (Mtb) infection. We found that at 6–7 months post-Mtb infection, 90% of the Mtb-infected T2DM mice died, whereas only 50% of BCG-vaccinated T2DM-Mtb-infected mice died. Moreover, 40% of the PBS-treated uninfected T2DM mice and 30% of the uninfected BCG-vaccinated T2DM mice died, whereas all uninfected and infected nondiabetic mice survived. BCG vaccination was less effective in reducing the lung bacterial burden of Mtb infected T2DM mice compared to Mtb-infected non-diabetic mice, however it reduced immunopathology of lung tissues. Further, we found increased survival of BCG vaccinated Mtb infected T2DM mice is associated with 2-fold expansion of IL-13 producing CXCR3+ T-regulatory cells as measured by flow cytometry, qRT-PCR and confocal microscopy. We also found that prior BCG vaccination restored the immunosuppressive function of T-regulatory cells of Mtb-infected T2DM mice and reduced inflammation. IL-13 producing T-regulatory cells of BCG vaccinated Mtb-infected T2DM mice converted proinflammatory M1 macrophages (iNOS) to anti-inflammatory M2 macrophage (Arg1) phenotype to suppress the inflammation. In contrast, anti-IL-13R antibody inhibited the conversion of macrophages from M1 to the M2 phenotype and enhanced the inflammatory cytokines (IL-6 and TNF-α) production. Our findings suggest a novel role for BCG in preventing excessive inflammation and mortality in T2DM mice infected with Mtb.

A rho GDP dissociation inhibitor produced by a subset of T-regulatory cells enhances mitophagy in Mycobacterium tuberculosis infected human macrophages

Previously, we found that a Rho GDP dissociation inhibitor (D4GDI), produced by apoptotic T regulatory cells inhibit Mycobacterium tuberculosis (Mtb) growth in human macrophages through reactive oxygen species (ROS) mediated IL-1β production. Mitochondria is an important source of ROS and critical for antibacterial properties. In the current study, we evaluated the effects of D4GDI on mitochondrial homeostasis and anti-microbial scheme during Mtb infection. Recombinant D4GDI (rD4GDI) treatment of Mtb infected human macrophages enhanced the accumulation of LC3B protein on the mitochondria and triggered mitophagy. rD4GDI treatment significantly enhanced the expression of a mitophagy receptor BCL2 and adenovirus E1B 19-kDa-interacting protein 3-like (BNIP3L). BNIP3L siRNA inhibited rD4GDI dependent accumulation of LC3B protein on the mitochondria and enhanced Mtb growth in human macrophages. Further we found that rD4GDI treatment of Mtb infected macrophages induces the expression of antimicrobial peptide phospholipase family protein phospholipase A2 group VII (PLA2G7). Further studies are underway to determine the interactions between BNIP3L, PLA2G7 and mitophagy in rD4GDI treated macrophages to inhibit Mtb growth in human macrophages.

BCG vaccination reduces the mortality of Mycobacterium tuberculosis-infected type 2 diabetes mellitus mice

Diabetes is a significant risk factor for the development of active tuberculosis. In this study, we used a mouse model of type 2 diabetes mellitus (T2DM) to determine the effect of prior Bacillus Calmette-Guérin (BCG) vaccination on immune responses to Mycobacterium tuberculosis (Mtb) infection. We found that, at 6-7 months after Mtb infection, 90% of the Mtb-infected T2DM mice died, whereas only 50% of BCG-vaccinated T2DM-Mtb-infected mice died. Moreover, 40% of the PBS-treated uninfected T2DM mice and 30% of the uninfected BCG-vaccinated T2DM mice died, whereas all uninfected and infected nondiabetic mice survived. BCG vaccination was less effective in reducing the lung bacterial burden of Mtb-infected T2DM mice compared with Mtb-infected nondiabetic mice. BCG vaccination significantly reduced lung inflammation in Mtb-infected T2DM mice compared with that of unvaccinated T2DM mice infected with Mtb. Furthermore, reduced mortality of BCG-vaccinated Mtb-infected T2DM mice is associated with expansion of IL-13-producing CXCR3+ Tregs in the lungs of Mtb-infected T2DM mice. Recombinant IL-13 and Tregs from BCG-vaccinated Mtb-infected T2DM mice converted proinflammatory M1 macrophages to antiinflammatory M2 macrophages. Our findings suggest a potentially novel role for BCG in preventing excess inflammation and mortality in T2DM mice infected with Mtb.

IL-22 produced by type 3 innate lymphoid cells (ILC3s) reduces the mortality of type 2 diabetes mellitus (T2DM) mice infected with Mycobacterium tuberculosis

Previously, we found that pathological immune responses enhance the mortality rate of Mycobacterium tuberculosis (Mtb)-infected mice with type 2 diabetes mellitus (T2DM). In the current study, we evaluated the role of the cytokine IL-22 (known to play a protective role in bacterial infections) and type 3 innate lymphoid cells (ILC3s) in regulating inflammation and mortality in Mtb-infected T2DM mice. IL-22 levels were significantly lower in Mtb-infected T2DM mice than in nondiabetic Mtb-infected mice. Similarly, serum IL-22 levels were significantly lower in tuberculosis (TB) patients with T2DM than in TB patients without T2DM. ILC3s were an important source of IL-22 in mice infected with Mtb, and recombinant IL-22 treatment or adoptive transfer of ILC3s prolonged the survival of Mtb-infected T2DM mice. Recombinant IL-22 treatment reduced serum insulin levels and improved lipid metabolism. Recombinant IL-22 treatment or ILC3 transfer prevented neutrophil accumulation near alveoli, inhibited neutrophil elastase 2 (ELA2) production and prevented epithelial cell damage, identifying a novel mechanism for IL-22 and ILC3-mediated inhibition of inflammation in T2DM mice infected with an intracellular pathogen. Our findings suggest that the IL-22 pathway may be a novel target for therapeutic intervention in T2DM patients with active TB disease.

IL-22 reduces the mortality of type 2 diabetes mellitus (T2DM) mice infected with Mycobacterium tuberculosis

IL-22 play an important role in protective immune responses against bacterial infections including Mtb and maintains homeostasis by regulating excess inflammation. IL-22 can also regulate glucose homeostasis, suggesting IL-22 pathway as a novel target for therapeutic intervention. Previously, we developed a mouse model of type 2 diabetes mellitus (T2DM) and found that pathological immune response enhances mortality of Mycobacterium tuberculosis (Mtb) infected T2DM mice. In the current study, we determined the role of IL-22 during Mtb infection in T2DM mice. We found innate lymphoid 3 cells (ILC3) are the major source for IL-22 and IL- 22 production was significantly reduced in the lungs and serum of T2DM mice infected with Mtb. Recombinant IL- 22 or adoptive transfer of ILC3 cells prolonged the survival of Mtb infected T2DM mice. Recombinant IL-22 prevented neutrophil accumulation near alveoli, reduced the serum insulin level and improved the lipid metabolism. Recombinant IL-22 also prevented neutrophil-mediated epithelial cell damage by inhibiting elastase production by neutrophils. Further, we found serum IL-22 levels were significantly less in tuberculosis (TB) patients with T2DM compared to TB patients without T2DM. Our findings suggest that IL-22 produced by ILC3 cells is essential to inhibit excess inflammation, epithelial cell damage in T2DM mice infected with Mtb.

Prior Bacillus Calmette-Guérin (BCG) vaccination ameliorates the pathogenesis of Type 2 diabetes mellitus mice infected with Mycobacterium tuberculosis

Previously, we found experimentally induced type 2 diabetes mellitus (T2DM) mice are highly susceptible to Mycobacterium tuberculosis (Mtb) infection. In the present study, we determined whether prior BCG vaccination has any effect on the susceptibility of T2DM mice infected with Mtb. C57BL/6 mice were vaccinated with BCG or treated with PBS, three months later some mice were induced with T2DM and after another month fifty percent of all groups of mice were challenged with Mtb. All Mtb infected T2DM mice and 40% of uninfected T2DM mice died within 10 months. In contrast, only 40% of Mtb infected BCG vaccinated T2DM mice and 20% of uninfected BCG vaccinated T2DM mice died. Lung bacterial burden was significantly less in Mtb infected BCG vaccinated T2DM mice compared to PBS treated Mtb infected mice. Pro and anti-inflammatory cytokine levels were significantly high in the lungs of Mtb infected BCG vaccinated T2DM mice compared to all other groups of vaccinated and PBS treated mice infected with Mtb. Our findings suggest that prior BCG vaccination protects Mtb infected mice from T2DM induced pathogenesis. Studies are underway to determine the BCG induced mechanism/s those protect T2DM mice challenged with Mtb.

Liver macrophages controls Mycobacterium tuberculosis growth by enhancing autophagy

Alveolar macrophages are the first cells to come in contact with TB pathogen in lung, but unable to eliminate Mycobacterium tuberculosis (M. tb) completely and serves as niche. In the current study, we compared M. tb growth and cytokine production by murine alveolar and liver macrophages. We found three-fold higher CFU in alveolar macrophages compared to liver macrophages (5 ± 1.7 × 106 vs. 1.776 ± 0.5 ×106 CFU) indicating that liver macrophages are more efficient in inhibiting M. tb growth. In contrast, M. tb H37Rv infected alveolar and liver macrophages produced equal amounts of TNF-α, IL-6, IL-10 & IL-1β. There is no significant difference in the apoptosis and M1/M2 paradigm of M. tb infected alveolar and liver macrophages. Flow cytometry analysis revealed the percentage of LC-3B+ M. tb infected liver macrophages were two-fold higher compared to percentage of LC-3B+ M. tb infected alveolar macrophage. This was confirmed by real time PCR. We also noted distinctly enhanced LC-3B puncta formation in infected liver macrophages as examined by confocal microscopy. We found significantly enhanced M. tb CFU in liver macrophages transfected with LC-3B, ATG-5, ATG-7 and Beclin-1 siRNA compared to liver macrophages transfected with control siRNA (p<0.01; 0.006; 0.01&0.002) respectively. Our results suggest that autophagy is involved in better restriction of M. tb growth by liver macrophages. Studies are underway to compare metabolic changes of control and M. tb H37Rv infected alveolar and liver macrophages and in vivo relevance to our current findings using mouse model of M. tb infection.

Type 2 diabetes mellitus induces TNFR1 mediated necroptotic cell death of mice alveolar macrophages infected with Mycobacterium tuberculosis

Previously, we developed a mouse model of type 2 diabetes mellitus (T2DM) using streptozotocin and nicotinamide and found that T2DM mice are susceptible to Mycobacterium tuberculosis (Mtb) infection. We also found that alveolar macrophages from T2DM mice were more permissive to Mtb growth ex vivo compared to non-diabetic controls. In the current study, we determined the defective mechanisms that make T2DM mice alveolar macrophages more susceptible to Mtb infection. Mtb infected alveolar macrophages from T2DM mice produced more TNF-α (973.8 ± 13.3 pg/ml vs. 614.6 ± 27.2 pg/ml, p<0.003) and less apoptotic (4.7 ± 1.8% vs. 28.6 ± 2.3%, p<0.001) compared to Mtb infected non-diabetic control mice. Mtb infected alveolar macrophages from T2DM mice expressed higher levels of TNFR1 (12.8 ± 0.5 vs. 2.09 ± 0.01, p<0.001) and markers of necroptosis RIPK1 (11.5 ± 0.57 vs. 2.94 ± 0.20, p<0.002), RIPK3 (16.1 ± 0.58 vs. 2.89 ± 0.2, p<0.001) and MLKL (9.2 ± 0.56 vs. 1.58 ± 0.72, p<0.02) compared to Mtb infected alveolar macrophages from non-diabetic control mice as determined by real-time PCR. This finding was again proved by Western blot and confocal microscopy. Anti-TNFR1 antibody treatment of alveolar macrophages from T2DM mice before or after Mtb infection reduced RIPK1, RIPK3 and MLKL expression as determined by RT-PCR. Our findings demonstrate that T2DM induces necroptosis of alveolar macrophages upon Mtb infection. Enhanced TNFR1 signaling in T2DM mice alveolar macrophages is responsible for enhanced necroptosis. We are also determining the subpopulations of T2DM mice alveolar macrophages that express higher levels of TNFR1 upon Mtb infection. Studies are underway to determine the in vivo relevance of our current findings to Mtb growth in T2DM mice.

Kupffer cells restricts Mycobacterium tuberculosis growth better than alveolar macrophages

Kupffer cells protect liver from bacterial infections. In the current study, we compared Mycobacterium tuberculosis (M.tb) growth and cytokine production by mice kupffer cells and alveolar macrophages. M.tb H37Rv infected kupffer cells and alveolar macrophages produced equal amounts of TNF-α, IL-6, IL-10 & IL-1β. In contrast, kupffer cells restricted M.tb growth better than alveolar macrophages (1 ± 0.346×106 CFU vs. 4 ± 0.916×106 CFU, p<0.03). There is no significant difference in the apoptosis of M.tb infected kupffer cells and alveolar macrophages. In contrast, M.tb infected kupffer cells expressed significant higher amounts of autophagy molecules LC-3B, ATG-7, ATG-5 and Beclin-1 (p<0.005, p<0.002, p<0.0032 & p<0.004 respectively) compared to M.tb infected alveolar macrophages as determined by real-time PCR. This was confirmed by Western blot and confocal microscopy. Our results suggest autophagy is involved in better restriction of M.tb growth by kupffer cells. Prime PCR analysis for 35 intracelluar signaling molecules those are involved in autophagy as well as in cytoskeleton indicated that M.tb infected kupffer cells significantly express higher levels of VASP (Vasodilator-stimulated phosphoprotein), RhoA (Ras homolog gene family member A) and Arp3 (Actin–related protein 3) genes (two fold, p<0.01, p<0.02&p<0.02 respectively) compared to M.tb infected alveolar macrophages. Studies are underway 1. To confirm whether autophagy is involved in better restriction of M.tb growth in kupffer cells. 2. Determine the role of cytoskeleton proteins those are involved in enhanced autophagy and M.tb growth inhibition in kupffer cells. 3. Determining in vivo relevance to our current findings using mouse model of M.tb infection.