Limits...
TNF-dependent regulation and activation of innate immune cells are essential for host protection against cerebral tuberculosis.

Francisco NM, Hsu NJ, Keeton R, Randall P, Sebesho B, Allie N, Govender D, Quesniaux V, Ryffel B, Kellaway L, Jacobs M - J Neuroinflammation (2015)

Bottom Line: Mycobacterial burden in brains, lungs and spleens were compared, and cerebral pathology and cellular contributions analysed by microscopy and flow cytometry after M. tuberculosis infection.Brain pathology reflected enhanced inflammation dominated by neutrophil influx.Our data show that neuron-derived TNF has a limited role in immune responses, but overall TNF production is necessary for protective immunity against CNS-TB.

View Article: PubMed Central - PubMed

Affiliation: Division of Immunology, Department of Clinical Laboratory Science, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa. franciscongiamb@gmail.com.

ABSTRACT

Background: Tuberculosis (TB) affects one third of the global population, and TB of the central nervous system (CNS-TB) is the most severe form of tuberculosis which often associates with high mortality. The pro-inflammatory cytokine tumour necrosis factor (TNF) plays a critical role in the initial and long-term host immune protection against Mycobacterium tuberculosis (M. tuberculosis) which involves the activation of innate immune cells and structure maintenance of granulomas. However, the contribution of TNF, in particular neuron-derived TNF, in the control of cerebral M. tuberculosis infection and its protective immune responses in the CNS were not clear.

Methods: We generated neuron-specific TNF-deficient (NsTNF(-/-)) mice and compared outcomes of disease against TNF(f/f) control and global TNF(-/-) mice. Mycobacterial burden in brains, lungs and spleens were compared, and cerebral pathology and cellular contributions analysed by microscopy and flow cytometry after M. tuberculosis infection. Activation of innate immune cells was measured by flow cytometry and cell function assessed by cytokine and chemokine quantification using enzyme-linked immunosorbent assay (ELISA).

Results: Intracerebral M. tuberculosis infection of TNF(-/-) mice rendered animals highly susceptible, accompanied by uncontrolled bacilli replication and eventual mortality. In contrast, NsTNF(-/-) mice were resistant to infection and presented with a phenotype similar to that in TNF(f/f) control mice. Impaired immunity in TNF(-/-) mice was associated with altered cytokine and chemokine synthesis in the brain and characterised by a reduced number of activated innate immune cells. Brain pathology reflected enhanced inflammation dominated by neutrophil influx.

Conclusion: Our data show that neuron-derived TNF has a limited role in immune responses, but overall TNF production is necessary for protective immunity against CNS-TB.

No MeSH data available.


Related in: MedlinePlus

Dissemination of M. tuberculosis to the brain in TNF−/− mice. a TNFf/f and TNF−/− mice were infected by aerosol inhalation at a dose of 200–500 CFUs/lung of M. tuberculosis, and mycobacterial burden in brains, lungs and spleens was determined at day 33 post-infection. b Foci of disseminated fluorescent bacilli (green) surrounded by CD11b+ microglia/macrophages (red) were present in the TNF−/− brain parenchyma. c, d The fluorescent image of intracellular M. tuberculosis GFP-expressing bacilli (green) found in the neurons (red) of TNF−/− mouse, labelled with c MAP2 and d β-III-tubulin. The orthogonal projection of confocal Z-stacks confirmed the cytosolic location of the bacilli in the x–y plane. All nuclei were labelled with DAPI (blue in b–d). Scale bars: b 20 μm; c, d 5 μm. The data represents two independent experiments
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4488051&req=5

Fig1: Dissemination of M. tuberculosis to the brain in TNF−/− mice. a TNFf/f and TNF−/− mice were infected by aerosol inhalation at a dose of 200–500 CFUs/lung of M. tuberculosis, and mycobacterial burden in brains, lungs and spleens was determined at day 33 post-infection. b Foci of disseminated fluorescent bacilli (green) surrounded by CD11b+ microglia/macrophages (red) were present in the TNF−/− brain parenchyma. c, d The fluorescent image of intracellular M. tuberculosis GFP-expressing bacilli (green) found in the neurons (red) of TNF−/− mouse, labelled with c MAP2 and d β-III-tubulin. The orthogonal projection of confocal Z-stacks confirmed the cytosolic location of the bacilli in the x–y plane. All nuclei were labelled with DAPI (blue in b–d). Scale bars: b 20 μm; c, d 5 μm. The data represents two independent experiments

Mentions: TNF plays an important role in host immunity against M. tuberculosis dissemination and latent infection [30–32]. A key function of TNF in granuloma formation and maintenance has been described in models of TNF-gene deficiency or neutralisation [16, 33, 34], supported by clinical evidence observed in the rheumatoid arthritis patients who presented with TB reactivation after anti-TNF therapy [5]. Moreover, inhibition of TNF leads to M. tuberculosis dissemination which causes extrapulmonary TB including severe CNS-TB [35, 36]. To investigate whether TNF protects against M. tuberculosis dissemination to the CNS, we challenged wild-type (TNFf/f) and TNF−/− mice by aerosol inhalation with M. tuberculosis H37Rv-GFP. In contrast to TNFf/f mice, TNF−/− mice were unable to control pulmonary TB infection, which resulted in high bacilli burdens in the lungs and spleens (Fig. 1a), similar to previous reports [37, 38]. Further, we confirmed dissemination of M. tuberculosis bacilli from the lungs to the brains in the absence of TNF; however, bacilli in the brains of TNFf/f mice were not detectable by culture (Fig. 1a). The latter observation is supported by previous studies of Hernandez Pando et al. [39], who showed limited, if any, detectable bacilli in the brains of wild-type mice using the same M. tuberculosis H37Rv laboratory strain.Fig. 1


TNF-dependent regulation and activation of innate immune cells are essential for host protection against cerebral tuberculosis.

Francisco NM, Hsu NJ, Keeton R, Randall P, Sebesho B, Allie N, Govender D, Quesniaux V, Ryffel B, Kellaway L, Jacobs M - J Neuroinflammation (2015)

Dissemination of M. tuberculosis to the brain in TNF−/− mice. a TNFf/f and TNF−/− mice were infected by aerosol inhalation at a dose of 200–500 CFUs/lung of M. tuberculosis, and mycobacterial burden in brains, lungs and spleens was determined at day 33 post-infection. b Foci of disseminated fluorescent bacilli (green) surrounded by CD11b+ microglia/macrophages (red) were present in the TNF−/− brain parenchyma. c, d The fluorescent image of intracellular M. tuberculosis GFP-expressing bacilli (green) found in the neurons (red) of TNF−/− mouse, labelled with c MAP2 and d β-III-tubulin. The orthogonal projection of confocal Z-stacks confirmed the cytosolic location of the bacilli in the x–y plane. All nuclei were labelled with DAPI (blue in b–d). Scale bars: b 20 μm; c, d 5 μm. The data represents two independent experiments
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4488051&req=5

Fig1: Dissemination of M. tuberculosis to the brain in TNF−/− mice. a TNFf/f and TNF−/− mice were infected by aerosol inhalation at a dose of 200–500 CFUs/lung of M. tuberculosis, and mycobacterial burden in brains, lungs and spleens was determined at day 33 post-infection. b Foci of disseminated fluorescent bacilli (green) surrounded by CD11b+ microglia/macrophages (red) were present in the TNF−/− brain parenchyma. c, d The fluorescent image of intracellular M. tuberculosis GFP-expressing bacilli (green) found in the neurons (red) of TNF−/− mouse, labelled with c MAP2 and d β-III-tubulin. The orthogonal projection of confocal Z-stacks confirmed the cytosolic location of the bacilli in the x–y plane. All nuclei were labelled with DAPI (blue in b–d). Scale bars: b 20 μm; c, d 5 μm. The data represents two independent experiments
Mentions: TNF plays an important role in host immunity against M. tuberculosis dissemination and latent infection [30–32]. A key function of TNF in granuloma formation and maintenance has been described in models of TNF-gene deficiency or neutralisation [16, 33, 34], supported by clinical evidence observed in the rheumatoid arthritis patients who presented with TB reactivation after anti-TNF therapy [5]. Moreover, inhibition of TNF leads to M. tuberculosis dissemination which causes extrapulmonary TB including severe CNS-TB [35, 36]. To investigate whether TNF protects against M. tuberculosis dissemination to the CNS, we challenged wild-type (TNFf/f) and TNF−/− mice by aerosol inhalation with M. tuberculosis H37Rv-GFP. In contrast to TNFf/f mice, TNF−/− mice were unable to control pulmonary TB infection, which resulted in high bacilli burdens in the lungs and spleens (Fig. 1a), similar to previous reports [37, 38]. Further, we confirmed dissemination of M. tuberculosis bacilli from the lungs to the brains in the absence of TNF; however, bacilli in the brains of TNFf/f mice were not detectable by culture (Fig. 1a). The latter observation is supported by previous studies of Hernandez Pando et al. [39], who showed limited, if any, detectable bacilli in the brains of wild-type mice using the same M. tuberculosis H37Rv laboratory strain.Fig. 1

Bottom Line: Mycobacterial burden in brains, lungs and spleens were compared, and cerebral pathology and cellular contributions analysed by microscopy and flow cytometry after M. tuberculosis infection.Brain pathology reflected enhanced inflammation dominated by neutrophil influx.Our data show that neuron-derived TNF has a limited role in immune responses, but overall TNF production is necessary for protective immunity against CNS-TB.

View Article: PubMed Central - PubMed

Affiliation: Division of Immunology, Department of Clinical Laboratory Science, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa. franciscongiamb@gmail.com.

ABSTRACT

Background: Tuberculosis (TB) affects one third of the global population, and TB of the central nervous system (CNS-TB) is the most severe form of tuberculosis which often associates with high mortality. The pro-inflammatory cytokine tumour necrosis factor (TNF) plays a critical role in the initial and long-term host immune protection against Mycobacterium tuberculosis (M. tuberculosis) which involves the activation of innate immune cells and structure maintenance of granulomas. However, the contribution of TNF, in particular neuron-derived TNF, in the control of cerebral M. tuberculosis infection and its protective immune responses in the CNS were not clear.

Methods: We generated neuron-specific TNF-deficient (NsTNF(-/-)) mice and compared outcomes of disease against TNF(f/f) control and global TNF(-/-) mice. Mycobacterial burden in brains, lungs and spleens were compared, and cerebral pathology and cellular contributions analysed by microscopy and flow cytometry after M. tuberculosis infection. Activation of innate immune cells was measured by flow cytometry and cell function assessed by cytokine and chemokine quantification using enzyme-linked immunosorbent assay (ELISA).

Results: Intracerebral M. tuberculosis infection of TNF(-/-) mice rendered animals highly susceptible, accompanied by uncontrolled bacilli replication and eventual mortality. In contrast, NsTNF(-/-) mice were resistant to infection and presented with a phenotype similar to that in TNF(f/f) control mice. Impaired immunity in TNF(-/-) mice was associated with altered cytokine and chemokine synthesis in the brain and characterised by a reduced number of activated innate immune cells. Brain pathology reflected enhanced inflammation dominated by neutrophil influx.

Conclusion: Our data show that neuron-derived TNF has a limited role in immune responses, but overall TNF production is necessary for protective immunity against CNS-TB.

No MeSH data available.


Related in: MedlinePlus