CFTR Depletion Confers Hypersusceptibility to Mycobacterium fortuitum in a Zebrafish Model

Abstract

The Mycobacterium fortuitum complex comprises several closely related species, causing pulmonary and extra-pulmonary infections. However, there is very limited knowledge about the disease pathogenesis involved in M. fortuitum infections, particularly due to the lack of suitable animal models. Using the zebrafish model, we show that embryos are susceptible to M. fortuitum infection in a dose-dependent manner. Furthermore, zebrafish embryos form granulomas from as early as 2 days post-infection, recapitulating critical aspects of mycobacterial pathogenesis observed in other pathogenic species. The formation of extracellular cords in infected embryos highlights a previously unknown pathogenic feature of M. fortuitum. The formation of large corded structures occurs also during in vitro growth, suggesting that this is not a host-adapted stress mechanism deployed during infection. Moreover, transient macrophage depletion led to rapid embryo death with increased extracellular cords, indicating that macrophages are essential determinants of M. fortuitum infection control. Importantly, morpholino depletion of the cystic fibrosis transmembrane conductance regulator (cftr) significantly increased embryo death, bacterial burden, bacterial cords and abscesses. There was a noticeable decrease in the number of cftr-deficient infected embryos with granulomas as compared to infected controls, suggesting that loss of CFTR leads to impaired host immune responses and confers hypersusceptiblity to M. fortuitum infection. Overall, these findings highlight the application of the zebrafish embryo to study M. fortuitum and emphasizes previously unexplored aspects of disease pathogenesis of this significant mycobacterial species.

The Role of Macrophages During Zebrafish Injury and Tissue Regeneration Under Infectious and Non-Infectious Conditions

“…This necrotic event takes place through the increased production of Reactive Oxygen Species (ROS) and calcium (Ca 2+ ) in the mitochondria, activating a mitochondrial matrix protein cyclophilin D, which promotes the opening of the mitochondrial permeability transition pores (mPTP), disturbing the membrane potential and resulting in necrosis (43)(44)(45)(46)(47)(48). (49)(50)(51), indicating that MФ are crucial to restrict the bacterial expansion and the formation of granulomas that constrain mycobacterial dissemination (52). The origin of the MФ recruited during M. marinum infection, located in the larval brain, has also been investigated.…”

A fresh look at mycobacterial pathogenicity with the zebrafish host model

“…Not only can hallmarks of human TB be recapitulated by Mmar infection of zebrafish, also the nerve damage characteristic for leprosy could be modeled in zebrafish larvae, using a Mmar strain with modified surface lipids to resemble Mycobacterium leprae (Madigan et al., 2017 ). Furthermore, the zebrafish host is permissive to non‐tuberculous human mycobacterial pathogens, like Mycobacterium abscessus, Mycobacterium kansassi and Mycobacterium fortuitum , all inducing granuloma formation in immunocompetent larvae and showing extensive extracellular cord formation in immunocompromised larvae (Bernut et al., 2016 ; Johansen & Kremer, 2020a , 2020b ).…”

Localized Infections with P. aeruginosa Strains Defective in Zinc Uptake Reveal That Zebrafish Embryos Recapitulate Nutritional Immunity Responses of Higher Eukaryotes

“…Among these, zebrafish are regarded with much interest. Zebrafish have an excellent potential as a vertebrate model for studying host–pathogen interactions, particularly for investigating different aspects of bacterial infections during CF [ 25 , 26 , 27 ]. So far, no studies have investigated whether zebrafish possess nutritional immunity mechanisms comparable to those of higher organisms.…”