Preferential expansion of Teff cells over Tregs during acute BCG infection.

<p>WT mice were infected i.v. with 2×10⁶ CFU <i>M. bovis</i> BCG (black squares), or not (black dots), and the (A) frequency and (B) total cell number of FoxP3⁺ Tregs within the live CD4⁺ T cell gate was determined in spleen (left) and lungs (right) at day 20 p.i.. Data are pooled from three independent experiments and represent the mean ± SD of 11–12 mice per group. Each symbol represents an individual mouse. N = 3. Statistical analysis: Mann-Whitney-U-Test. <i>*p<0.05; **p<0.01; and ***p<0.001</i>.</p

Removal of Tregs after <i>Mtb</i> aerosol infection in DEREG mice does not influence pathogen control.

<p>DEREG mice were infected with approx. 100<i>Mtb</i> via the aerosol route. Tregs were depleted by DT administration on days 11/12, 18/19 and 25/26 (black dots/bars) or not (white dots/bars). (A) Experimental scheme. (B) Mycobacterial colony enumeration assays were performed in lungs (left), spleen (middle) and liver (right) on day 20, 28 and 42 p.i.. Data represent mean ± SD of 5 mice per group. (C) The frequency of ESAT6_1–20-specific IFN-γ- and IL-17A-producing CD4⁺ cells per 10⁵ total lung cells was determined by ELISPOT assay at different time points after infection. Bar graphs represent the mean ± SD of 5 mice per group. N = 3 (day 20), N = 1(day 28 and 42).</p

Limited impact of Treg depletion on inflammatory cytokine production after <i>M. bovis</i> BCG infection.

<p>Intracellular cytokine production by FoxP3⁻CD4⁺ T cells was analysed in the spleen of day 7/8 and 14/15 double-depleted (black bars) or untreated DEREG mice (white bars) on day 20 after i.v. infection with 2×10⁶ CFU <i>M. bovis</i> BCG. Percentages of (A) IFN-γ, (B) IL-17A and (C) IL-10 production within live FoxP3⁻CD4⁺ T cells after PMA/ionomycin restimulation are shown. Bar graphs represent mean ± SD of 3–5 mice per group. N = 3. Statistical analysis: Mann-Whitney-U-Test. <i>*p<0.05; **p<0.01; and ***p<0.001</i>.</p

eGFP⁻ diTregs rapidly replenish the pool of Tregs in <i>M. bovis</i> BCG infected DEREG mice.

<p>DEREG mice were infected i.v. with 2×10⁶ CFU <i>M. bovis</i> BCG and treated, or not, with DT on days 7/8 and 14/15 p.i. and (A) the percentage of eGFP⁺ (grey)- and eGFP⁻ (white) Foxp3⁺CD4⁺ Tregs cells in the spleen (left) and lungs (right) or (B) the expression of the thymic Treg markers Helios (left) and Nrp-1 (right) in the eGFP⁺ (grey) and eGFP⁻ (white) Treg population were analysed in the spleen at day 20 p.i. in DT-treated mice. Bar graphs represent mean ± SD of 3–5 mice per group. N = 3. Statistical analysis: Mann-Whitney-U-Test. <i>*p<0.05; **p<0.01; and ***p<0.001</i>.</p

Presentation_1.PDF

<p>Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, is able to efficiently manipulate the host immune system establishing chronic infection, yet the underlying mechanisms of immune evasion are not fully understood. Evidence suggests that this pathogen interferes with host cell lipid metabolism to ensure its persistence. Fatty acid metabolism is regulated by acetyl-CoA carboxylase (ACC) 1 and 2; both isoforms catalyze the conversion of acetyl-CoA into malonyl-CoA, but have distinct roles. ACC1 is located in the cytosol, where it regulates de novo fatty acid synthesis (FAS), while ACC2 is associated with the outer mitochondrial membrane, regulating fatty acid oxidation (FAO). In macrophages, mycobacteria induce metabolic changes that lead to the cytosolic accumulation of lipids. This reprogramming impairs macrophage activation and contributes to chronic infection. In dendritic cells (DCs), FAS has been suggested to underlie optimal cytokine production and antigen presentation, but little is known about the metabolic changes occurring in DCs upon mycobacterial infection and how they affect the outcome of the immune response. We therefore determined the role of fatty acid metabolism in myeloid cells and T cells during Mycobacterium bovis BCG or Mtb infection, using novel genetic mouse models that allow cell-specific deletion of ACC1 and ACC2 in DCs, macrophages, or T cells. Our results demonstrate that de novo FAS is induced in DCs and macrophages upon M. bovis BCG infection. However, ACC1 expression in DCs and macrophages is not required to control mycobacteria. Similarly, absence of ACC2 did not influence the ability of DCs and macrophages to cope with infection. Furthermore, deletion of ACC1 in DCs or macrophages had no effect on systemic pro-inflammatory cytokine production or T cell priming, suggesting that FAS is dispensable for an intact innate response against mycobacteria. In contrast, mice with a deletion of ACC1 specifically in T cells fail to generate efficient T helper 1 responses and succumb early to Mtb infection. In summary, our results reveal ACC1-dependent FAS as a crucial mechanism in T cells, but not DCs or macrophages, to fight against mycobacterial infection.</p