Interleukin 10 mutant zebrafish have an enhanced interferon gamma response and improved survival against a Mycobacterium marinum infection

Abstract Tuberculosis ranks as one of the world’s deadliest infectious diseases causing more than a million casualties annually. IL10 inhibits the function of Th1 type cells, and IL10 deficiency has been associated with an improved resistance against Mycobacterium tuberculosis infection in a mouse model. Here, we utilized M. marinum infection in the zebrafish (Danio rerio) as a model for studying Il10 in the host response against mycobacteria. Unchallenged, nonsense il10e46/e46 mutant zebrafish were fertile and phenotypically normal. Following a chronic mycobacterial infection, il10e46/e46 mutants showed enhanced survival compared to the controls. This was associated with an increased expression of the Th cell marker cd4-1 and a shift towards a Th1 type immune response, which was demonstrated by the upregulated expression of tbx21 and ifng1, as well as the down-regulation of gata3. In addition, at 8 weeks post infection il10e46/e46 mutant zebrafish had reduced expression levels of proinflammatory cytokines tnfb and il1b, presumably indicating slower progress of the infection. Altogether, our data show that Il10 can weaken the immune defense against M. marinum infection in zebrafish by restricting ifng1 response. Importantly, our findings support the relevance of M. marinum infection in zebrafish as a model for tuberculosis

Intelectin 3 is dispensable for resistance against a mycobacterial infection in zebrafish (Danio rerio)

Abstract Tuberculosis is a multifactorial bacterial disease, which can be modeled in the zebrafish (Danio rerio). Abdominal cavity infection with Mycobacterium marinum, a close relative of Mycobacterium tuberculosis, leads to a granulomatous disease in adult zebrafish, which replicates the different phases of human tuberculosis, including primary infection, latency and spontaneous reactivation. Here, we have carried out a transcriptional analysis of zebrafish challenged with low-dose of M. marinum, and identified intelectin 3 (itln3) among the highly up-regulated genes. In order to clarify the in vivo significance of Itln3 in immunity, we created nonsense itln3 mutant zebrafish by CRISPR/Cas9 mutagenesis and analyzed the outcome of M. marinum infection in both zebrafish embryos and adult fish. The lack of functional itln3 did not affect survival or the mycobacterial burden in the zebrafish. Furthermore, embryonic survival was not affected when another mycobacterial challenge responsive intelectin, itln1, was silenced using morpholinos either in the WT or itln3 mutant fish. In addition, M. marinum infection in dexamethasone-treated adult zebrafish, which have lowered lymphocyte counts, resulted in similar bacterial burden in both WT fish and homozygous itln3 mutants. Collectively, although itln3 expression is induced upon M. marinum infection in zebrafish, it is dispensable for protective mycobacterial immune response

Characterization of immune response against Mycobacterium marinum infection in the main hematopoietic organ of adult zebrafish (Danio rerio)

Abstract Tuberculosis remains a major global health challenge. To gain information about genes important for defense against tuberculosis, we used a well-established tuberculosis model; Mycobacterium marinum infection in adult zebrafish. To characterize the immunological response to mycobacterial infection at 14 days post infection, we performed a whole-genome level transcriptome analysis using cells from kidney, the main hematopoietic organ of adult zebrafish. Among the upregulated genes, those associated with immune signaling and regulation formed the largest category, whereas the largest group of downregulated genes had a metabolic role. We also performed a forward genetic screen in adult zebrafish and identified a fish line with severely impaired survival during chronic mycobacterial infection. Based on transcriptome analysis, these fish have decreased expression of several immunological genes. Taken together, these results give new information about the genes involved in the defense against mycobacterial infection in zebrafish