The adaptor molecule CARD9 is essential for tuberculosis control

The cross talk between host and pathogen starts with recognition of bacterial signatures through pattern recognition receptors (PRRs), which mobilize downstream signaling cascades. We investigated the role of the cytosolic adaptor caspase recruitment domain family, member 9 (CARD9) in tuberculosis. This adaptor was critical for full activation of innate immunity by converging signals downstream of multiple PRRs. Card9−/− mice succumbed early after aerosol infection, with higher mycobacterial burden, pyogranulomatous pneumonia, accelerated granulocyte recruitment, and higher abundance of proinflammatory cytokines and granulocyte colony-stimulating factor (G-CSF) in serum and lung. Neutralization of G-CSF and neutrophil depletion significantly prolonged survival, indicating that an exacerbated systemic inflammatory disease triggered lethality of Card9−/− mice. CARD9 deficiency had no apparent effect on T cell responses, but a marked impact on the hematopoietic compartment. Card9−/− granulocytes failed to produce IL-10 after Mycobaterium tuberculosis infection, suggesting that an absent antiinflammatory feedback loop accounted for granulocyte-dominated pathology, uncontrolled bacterial replication, and, ultimately, death of infected Card9−/− mice. Our data provide evidence that deregulated innate responses trigger excessive lung inflammation and demonstrate a pivotal role of CARD9 signaling in autonomous innate host defense against tuberculosis

Pulmonary immune responses to Mycobacterium tuberculosis in exposed individuals

BACKGROUND: Blood based Interferon-(IFN)-γ release assays (IGRAs) have a poor predictive value for the development of tuberculosis. This study aimed to investigate the correlation between IGRAs and pulmonary immune responses in tuberculosis contacts in Germany. METHODS: IGRAs were performed on bronchoalveolar lavage (BAL) cells and peripheral blood from close healthy contacts of patients with culturally confirmed tuberculosis. Cellular BAL composition was determined by flow cytometry. BAL cells were co-cultured with three strains of Mycobacterium tuberculosis (Mtb) and Mtb derived antigens including Purified Protein Derivative (PPD), 6 kD Early Secretory Antigenic Target (ESAT-6) and 10 kD Culture Filtrate Protein (CFP-10). Levels of 29 cytokines and chemokines were analyzed in the supernatants by multiplex assay. Associations and effects were examined using linear mixed-effects models. RESULTS:There were wide variations of inter-individual cytokine levels in BAL cell culture supernatants. Mycobacterial infection and stimulation with PPD showed a clear induction of several macrophage and lymphocyte associated cytokines, reflecting activation of these cell types. No robust correlation between cytokine patterns and blood IGRA status of the donor was observed, except for slightly higher Interleukin-2 (IL-2) responses in BAL cells from IGRA-positive donors upon mycobacterial infection compared to cells from IGRA-negative donors. Stronger correlations were observed when cytokine patterns were stratified according to BAL IGRA status. BAL cells from donors with BAL IGRA-positive responses produced significantly more IFN-γ and IL-2 upon PPD stimulation and mycobacterial infection than cells from BAL IGRA-negative individuals. Correlations between BAL composition and basal cytokine release from unstimulated cells were suggestive of pre-activated lymphocytes but impaired macrophage activity in BAL IGRA-positive donors, in contrast to BAL IGRA-negative donors. CONCLUSIONS: In vitro BAL cell cytokine responses to M. tuberculosis antigens or infection do not reflect blood IGRA status but do correlate with stronger cellular responses in BAL IGRA-positive donors. The cytokine patterns observed suggest a pre-activated state of lymphocytes and suppressed macrophage responsiveness in BAL cells from BAL IGRA-positive individuals

Comparison of acetate inhibition on growth of host and recombinant E. coli K12 strains

10.1007/BF01027012Biotechnology Letters14121115-1118BILE