Improvement of the resistance against early Mycobacterium tuberculosis-infection in the absence of PI3Kγ enzyme is associated with increase of CD4+IL-17+ cells and neutrophils.

Given the impossibility to study the lung immune response during Mycobacterium tuberculosis-latent infection, and consequently, the mechanisms that control the bacterial load, it is reasonable to determine the activation of local immunity in the early phase of the infection. The phosphatidylinositol-3-kinase gamma enzyme (PI3Kγ) is involved in the leukocyte recruitment, phagocytosis and cellular differentiation, and therefore, it is considered a promising target for the development of immunotherapies for chronic inflammatory diseases. Mice genetically deficient in PI3Kγ (PI3Kγ-/-) or WT (Wild Type) were evaluated 15 days post-infection. The enzyme deficiency improved the resistance against infection, increased the frequency of CD4+IL-17+ cells, the production of IL-17 as well as the gene and protein expression of molecules associated with Th17 cell differentiation and neutrophil recruitment. Our findings show, for the first time, the participation of the PI3Kγ in vivo in the M. tuberculosis-infection, and suggest an association of Th17 cells with protection in the early phase of tuberculosis.

M2 macrophages or IL-33 treatment attenuate ongoing Mycobacterium tuberculosis infection.

The protective effects of mycobacterial infections on lung allergy are well documented. However, the inverse relationship between tuberculosis and type 2 immunity is still elusive. Although type 1 immunity is essential to protection against Mycobacterium tuberculosis it might be also detrimental to the host due to the induction of extensive tissue damage. Here, we determined whether lung type 2 immunity induced by allergen sensitization and challenge could affect the outcome of M. tuberculosis infection. We used two different protocols in which sensitization and allergen challenge were performed before or after M. tuberculosis infection. We found an increased resistance to M. tuberculosis only when allergen exposure was given after, but not before infection. Infected mice exposed to allergen exhibited lower bacterial load and cellular infiltrates in the lungs. Enhanced resistance to infection after allergen challenge was associated with increased gene expression of alternatively activated macrophages (M2 macrophages) and IL-33 levels. Accordingly, either adoptive transfer of M2 macrophages or systemic IL-33 treatment was effective in attenuating M. tuberculosis infection. Notably, the enhanced resistance induced by allergen exposure was dependent on IL-33 receptor ST2. Our work indicates that IL-33 might be an alternative therapeutic treatment for severe tuberculosis.

Attenuation of experimental asthma by mycobacterial protein combined with CpG requires a TLR9-dependent IFN-γ-CCR2 signalling circuit.

BACKGROUND: Allergic asthma is a chronic pulmonary disease characterized by a Th2 inflammatory response. The modulation of a Th2 immune response based on immune deviation to a Th1 pattern or induction and migration of regulatory T cells to the lungs constitutes one of the major therapeutic approaches that is being investigated for the treatment of allergic asthma. The potentials of Mycobacterium leprae 65-kD heat-shock protein or Toll-like receptor 9 ligand (CpG oligodeoxynucleotides) as immune modulators for the treatment of airway allergic disease have been studied individually. OBJECTIVE: Mycobacterial protein combined with CpG was used as immunotherapy for airway allergy. METHODS: Using an ovalbumin-induced asthma model, mice were sensitized and challenged, and then treated with mycobacterial heat-shock protein (Hsp65) combined with CpG. RESULTS: The treatment of mice with established allergy led to the attenuation of eosinophilia, Th2 cytokines and airway hyperresponsiveness. Hsp65 plus CpG treatment also induced an increase in OVA-specific IFN-γ levels and in the frequency of lung inflammatory monocytes. Moreover, we show that the reduction of eosinophilia and the recruitment of inflammatory monocytes to the lungs required early triggering of TLR9, IFN-γ and CCR2 by immunotherapy components. CONCLUSION: In addition to immune deviation to a Th1 response in the modulation of Th2 allergic inflammation, our findings also attribute an important role to the innate response mediated by TLR9, associated with the recruitment of CCR2-dependent monocytes. CLINICAL RELEVANCE: Our findings show that the Hsp65/CpG treatment is a promising strategy for consideration in translational studies.