Gbp1 increases zebrafish susceptibility to mycobacterial infection by promoting macrophage pyroptotic cell death

Abstract Guanylate-binding proteins (GBP) are a family of interferon-inducible GTPases that operate via cell-autonomous immunity against intracellular pathogens and regulate cell death responses of infected host cells. GBPs have emerged as robust markers of human mycobacterial diseases, including tuberculosis and leprosy. However, their function in mycobacterial infections remains poorly understood. Here, using a zebrafish infection model with Mycobacterium marinum , a pathogen frequently used to model tuberculosis, we report that members of the GBP family differentially regulate both the host defense ability and the extent of cell death induced by mycobacterial infection. By genetically inhibiting each of the four zebrafish GBPs, we show that three of the family members (Gbp2, Gbp3 and Gbp4) contribute to host resistance. Strikingly, zebrafish larvae showed an improved ability to restrict mycobacterial growth when gbp1 was inhibited, indicating that Gbp1 plays a detrimental role in the response to mycobacterial infection. This effect of Gbp1 was dependent on M. marinum exerting its ESX-1-driven virulence. While none of the Gbp deficiencies affected leukocyte numbers or pathogen acidification, we found that macrophage cell death profiles were altered. Mechanistically, Gbp1 promotes pyroptotic cell death by activating Caspase a in macrophages, thereby attracting neutrophils and increasing mycobacterial dissemination. Additionally, the effect of Gbp1 on pyroptosis correlates with altered tnfa expression in macrophages polarization, as genetic inhibition induced increased expression of this proinflammatory marker. Taken together, our results suggest that the adverse effect of Gbp1 on host resistance to mycobacteria is driven by altered macrophage inflammatory and pyroptotic cell death responses, exacerbating infection. Furthermore, these findings suggest that GBP modulation might be explored as a therapeutic strategy for mycobacterial infections.