Article

Mycobacterium marinum Infection of Adult Zebrafish Causes Caseating Granulomatous Tuberculosis and Is Moderated by Adaptive Immunity

Department of Microbiology, Box 357242, University of Washington, Seattle, WA 98195, USA.
Infection and Immunity (Impact Factor: 4.16). 12/2006; 74(11):6108-17. DOI: 10.1128/IAI.00887-06
Source: PubMed

ABSTRACT The zebrafish, a genetically tractable model vertebrate, is naturally susceptible to tuberculosis caused by Mycobacterium marinum, a close genetic relative of the causative agent of human tuberculosis, Mycobacterium tuberculosis. We previously developed a zebrafish embryo-M. marinum infection model to study host-pathogen interactions in the context of innate immunity. Here, we have constructed a flowthrough fish facility for the large-scale longitudinal study of M. marinum-induced tuberculosis in adult zebrafish where both innate and adaptive immunity are operant. We find that zebrafish are exquisitely susceptible to M. marinum strain M. Intraperitoneal injection of five organisms produces persistent granulomatous tuberculosis, while the injection of approximately 9,000 organisms leads to acute, fulminant disease. Bacterial burden, extent of disease, pathology, and host mortality progress in a time- and dose-dependent fashion. Zebrafish tuberculous granulomas undergo caseous necrosis, similar to human tuberculous granulomas. In contrast to mammalian tuberculous granulomas, zebrafish lesions contain few lymphocytes, calling into question the role of adaptive immunity in fish tuberculosis. However, like rag1 mutant mice infected with M. tuberculosis, we find that rag1 mutant zebrafish are hypersusceptible to M. marinum infection, demonstrating that the control of fish tuberculosis is dependent on adaptive immunity. We confirm the previous finding that M. marinum DeltaRD1 mutants are attenuated in adult zebrafish and extend this finding to show that DeltaRD1 predominantly produces nonnecrotizing, loose macrophage aggregates. This observation suggests that the macrophage aggregation defect associated with DeltaRD1 attenuation in zebrafish embryos is ongoing during adult infection.

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Available from: Lynn Connolly, Aug 04, 2014
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    • "The utility of goldfish for studying mycobacterial infection was demonstrated as early as 1926 by Joseph D. Aronson, who first identified M. marinum as a pathogen of fish in the Philadelphia aquarium (Aronson, 1926). Since then, several fish species, including zebrafish, goldfish, and medaka have been used as an in vivo model system to elucidate the pathology caused by mycobacteria (Broussard and Ennis, 2007; Hodgkinson et al., 2012; Swaim et al., 2006; Talaat et al., 1999, 1998), as well as in vitro, using primary kidney macrophages to assess their anti-mycobacterial responses (Grayfer et al., 2011; Hodgkinson et al., 2012). Recently, our group isolated and characterized goldfish primary kidney neutrophils that remained viable in culture for several days and were also functionally similar to mammalian neutrophils in that they were highly motile, exhibited degranulation and produced a robust respiratory burst response, (Katzenback and Belosevic, 2009). "
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    ABSTRACT: The lack of a reliable mammalian neutrophil in vitro culture system has restricted our ability to examine their precise roles in mycobacterial infections. Previously, we developed the procedures for the isolation and culture of primary kidney-derived neutrophil-like cells from goldfish that are functionally and morphologically similar to mammalian neutrophils. The cultured primary goldfish neutrophils exhibited prolonged viability and functional effector responses. In this study, we demonstrate that when exposed to live or heat-killed Mycobacterium marinum, goldfish neutrophils increased their mRNA levels for several pro-inflammatory cytokines (il-1β1, il-1β2, tnfα-1, tnfα-2) and the cytokine receptors (ifngr1-1, tnfr1, tnfr2). These neutrophils also exhibited chemotaxis toward live mycobacteria, internalized the bacilli, and produced reactive oxygen intermediates (ROI) in response to pathogen exposure. The survival of intracellular mycobacteria was significantly reduced in activated neutrophils, indicating a robust killing response by these teleost granulocytes. We suggest that this goldfish primary neutrophil in vitro model system will provide important information regarding neutrophil-mediated host defense mechanisms against mycobacteria in teleosts as well as in higher vertebrates. Copyright © 2015. Published by Elsevier Ltd.
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    • "This study is, from our point of view, the most important evidence of how the zebrafish model can be used to validate and to re-postulate host–pathogen interactions during mycobacterial infection. On the other hand, Swaim et al. (2006) reported that lymphocytes play the same critical role in controlling mycobacterial infection in fishes and mammals by the use of a defective zebrafish mutant in the rag1 gene. They also demonstrated that bacteria defective in RD1 region are also attenuated in zebrafish. "
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    • "During the last decade, the zebrafish (Danio rerio) has been positioned as a powerful model for immunity research not only for other fish species, but also for mammals [15] [16] [17] [18] [19]. "
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