Pathogen recognition and activation of the innate immune response in zebrafish

The zebrafish has proven itself as an excellent model to study vertebrate innate immunity. It presents us with possibilities for in vivo imaging of host-pathogen interactions which are unparalleled in mammalian model systems. In addition, its suitability for genetic approaches is providing new insights on the mechanisms underlying the innate immune response. Here, we review the pattern recognition receptors that identify invading microbes, as well as the innate immune effector mechanisms that they activate in zebrafish embryos. We compare the current knowledge about these processes in mammalian models and zebrafish and discuss recent studies using zebrafish infection models that have advanced our general understanding of the innate immune system. Furthermore, we use transcriptome analysis of zebrafish infected with E. tarda, S. typhimurium, and M. marinum to visualize the gene expression profiles resulting from these infections. Our data illustrate that the two acute disease-causing pathogens, E. tarda and S. typhimurium, elicit a highly similar proinflammatory gene induction profile, while the chronic disease-causing pathogen, M. marinum, induces a weaker and delayed innate immune response.