TB Compare – Discovery of novel protective immune responses against zoonotic bovine and human tuberculosis

• Applicant: Bjoern Corleis, Ph.D.
• Subject Area: Medical Microbiology and Mycology, Hygiene, Molecular Infection Biology ; Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 439662427

Pathogens of the Mycobacterium tuberculosis complex (Mtbc) kill 1-2 million humans, livestock and wildlife every year; however, the mechanisms that govern protective immunity against Mtbc remain incompletely understood. In the mouse model of human tuberculosis, the cytokine IFNγ was identified as a key mediator of protection against Mtbc, executed by inducible nitric oxide synthase (iNOS). Although, iNOS activity protects against experimental tuberculosis, studies in natural hosts of Mtbc such as humans and cattle do not support a critical role for iNOS in controlling infection thus underscoring the existing knowledge gap. Intriguingly, cattle are susceptible to Mycobacterium bovis; however, they can control Mycobacterium tuberculosis (Mtb) by unknown mechanisms. We hypothesize that a systematic analysis of the role of IFNγ in these distinct biological models bridging approaches in comparative- systems-, and single-cell immunology will enable a comprehensive understanding of the different pathways activated by cytokines in macrophages from different hosts, which lead to protection or disease. We developed synchronized protocols universally applied to primary in vitro differentiated macrophages and macrophage cell lines from cattle, human and mouse. This will allow us to investigate anti-mycobacterial mechanisms, the relevance of iNOS and the stress response of Mtb in macrophages from 3 different mammalian species. The feasibility of our project is supported by well-established methods for Mtb infection studies, single-cell RNAseq, access to primary macrophages or cell lines from different mammalian species and in-house engineered Mtb reporter strains. Aim 1 will test the hypothesis that macrophage activation by IFNγ triggers different stress responses depending on the host species. The capacity of Mtb to respond to intracellular stresses induced by IFNγ will be determined by Mtb reporter strains for growth and phagosome stress. In parallel, we will leverage advances in genetic engineering to interrogate the contribution of inducible nitric oxide synthase in primary macrophages. Aim 2 will test the hypothesis that cattle better control Mtb growth compared to human or mouse cells. We will investigate the anti-mycobacterial program of cytokine-activated macrophages using single cell RNAseq and reporter assays for bacterial survival. Based on these data we will then identify pathways which are uniquely associated with control mechanisms against Mtb growth in bovine macrophages. Finally, we will establish siRNA protocols to investigate causative relations of genes in bovine macrophages and control of Mtb.Our systematic comparison of experimental models and natural hosts will improve our understanding of mechanisms of protection in the natural host versus animal models of tuberculosis. This will reduce the risk of developing therapeutic and vaccine interventions which only work in one particular cell type or experimental mammalian host.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partner: Professor Dr. Bryan Bryson