Passive transfer of interferon-γ over-expressing macrophages enhances resistance of SCID mice to Mycobacterium tuberculosis infection

Characterization of cellular immune response in hamsters immunized with recombinant vaccines against leptospirosis based on LipL32:LemA:LigAni chimeric protein

In the last 20 years, various research groups have endeavored to develop recombinant vaccines against leptospirosis to overcome the limitations of commercially available bacterins. Numerous antigens and vaccine formulations have been tested thus far. However, the analysis of cellular response in these vaccine formulations is not commonly conducted, primarily due to the scarcity of supplies and kits for the hamster animal model. Our research group has already tested the Q1 antigen, a chimeric protein combining the immunogenic regions of LipL32, LemA, and LigANI, in recombinant subunit and BCG-vectored vaccines. In both strategies, 100 % of the hamsters were protected against clinical signs of leptospirosis. However, only the recombinant BCG-vectored vaccine provided protection against renal colonization. Thus, the objective of this study is to characterize the cellular immune response in hamsters immunized with different vaccine formulations based on the Q1 antigen through transcriptional analysis of cytokines. The hamsters were allocated into groups and vaccinated as follows: recombinant subunit (rQ1), recombinant BCG (rBCG:Q1), and saline and BCG Pasteur control vaccines. To assess the cellular response induced by the vaccines, we cultured and stimulated splenocytes, followed by RNA extraction from the cells and analysis of cytokines using real-time PCR. The results revealed that the recombinant subunit vaccine elicited a Th2-type response, characterized by the expression of cytokines IL-10, IL-1α, and TNF-α. This pattern closely resembles the cytokines expressed in severe cases of leptospirosis. On the other hand, the rBCG-vectored vaccine induced a Th1-type response with significant up-regulation of IFN-γ. These findings suggest the involvement of the cellular response and the IFN-γ mediated inflammatory response in the sterilizing immunity mediated by rBCG. Therefore, this study may assist future investigations in characterizing the cellular response in hamsters, aiming to elucidate the mechanisms of efficacy and establish potential correlates of protection.

Macrophage innate training induced by IL-4 and IL-13 activation enhances OXPHOS driven anti-mycobacterial responses

Macrophages are a highly adaptive population of innate immune cells. Polarization with IFNγ and LPS into the 'classically activated' M1 macrophage enhances pro-inflammatory and microbicidal responses, important for eradicating bacteria such as Mycobacterium tuberculosis. By contrast, 'alternatively activated' M2 macrophages, polarized with IL-4, oppose bactericidal mechanisms and allow mycobacterial growth. These activation states are accompanied by distinct metabolic profiles, where M1 macrophages favor near exclusive use of glycolysis, whereas M2 macrophages up-regulate oxidative phosphorylation (OXPHOS). Here, we demonstrate that activation with IL-4 and IL-13 counterintuitively induces protective innate memory against mycobacterial challenge. In human and murine models, prior activation with IL-4/13 enhances pro-inflammatory cytokine secretion in response to a secondary stimulation with mycobacterial ligands. In our murine model, enhanced killing capacity is also demonstrated. Despite this switch in phenotype, IL-4/13 trained murine macrophages do not demonstrate M1-typical metabolism, instead retaining heightened use of OXPHOS. Moreover, inhibition of OXPHOS with oligomycin, 2-deoxy glucose or BPTES all impeded heightened pro-inflammatory cytokine responses from IL-4/13 trained macrophages. Lastly, this work identifies that IL-10 attenuates protective IL-4/13 training, impeding pro-inflammatory and bactericidal mechanisms. In summary, this work provides new and unexpected insight into alternative macrophage activation states in the context of mycobacterial infection.

The role of interferon-gamma and interferon-gamma receptor in tuberculosis and nontuberculous mycobacterial infections

Mycobacterium tuberculosis (Mtb) and nontuberculous mycobacteria (NTM) remain the leading causes of lung disease and mortality worldwide. Interferon-gamma (IFN-γ) and its receptor (IFN-γR) play a key role in mediating immunity against Mtb and NTM. This study was conducted as a systematic review; all information was collected from databases such as: PubMed, Scopus, Medline, SID, and medical databases. Finally, all the collected data were reviewed, and all content was categorized briefly. There is growing evidence that IFN-γ plays an important role in host defense against these two intracellular pathogens by activating macrophages. In addition, IFN-γ has been shown to be an integral part of various antibacterial methods such as granuloma formation and phagosome-lysosome fusion, both of which lead to the death of intracellular Mycobacterium. As a result, its absence is associated with overgrowth of intracellular pathogens and disease caused by Mtb or Mycobacterium nontuberculosis. We also look at the role of IFN-γR in Mtb or NTM because IFN-γ acts through IFN-γR. Finally, we introduce new approaches to the treatment of M. tuberculosis complex (MTC) and NTM disease, such as cell and gene-based therapies that work by modulating IFN-γ and IFN-γR.

Mycobacterial para-Hydroxybenzoic Acid-Derivatives (pHBADs) and Related Structures Induce Macrophage Innate Memory

Macrophages are key immune cells for combatting Mycobacterium tuberculosis. However, M. tuberculosis possesses means to evade macrophage bactericidal responses by, for instance, secretion of the immunomodulatory para-hydroxybenzoic acid derivatives (pHBADs). While these molecules have been implicated in inhibiting macrophage responses in an acute context, little is known about their ability to reprogram macrophages via induction of long-term innate memory. Since innate memory has been highlighted as a promising strategy to augment bactericidal immune responses against M. tuberculosis, investigating corresponding immune evasion mechanisms is highly relevant. Our results reveal for the first time that pHBAD I and related molecules (unmethylated pHBAD I and the hexose l-rhamnose) reduce macrophage bactericidal mechanisms in both the short- and the long-term. Moreover, we demonstrate how methyl-p-anisate hinders bactericidal responses soon after exposure yet results in enhanced pro-inflammatory responses in the long-term. This work highlights new roles for these compounds in M. tuberculosis pathogenesis.