Bacterial lipopolysaccharides induce genes involved in the innate immune response in embryos of the zebrafish (Danio rerio).

The innate immune response in fish represents an early, rapid defence against pathogens. Environmental contaminants could disturb this defence and negatively influence the ability to protect against infection. However, analysis of immune-modulation has not yet been included in testing strategies for environmental risk assessment of chemicals. In order to establish an efficient, small scale test system, the ability to induce the innate immune response by bacterial lipopolysaccharides in zebrafish embryos was investigated. The level of expression of various genes involved in inflammation was used as the endpoint. We could show that immersion of embryos in LPS induced the gene expression of two key pro-inflammatory cytokines, tumor necrosis factor alpha and interleukin 1 beta in 32 h old zebrafish embryos. The gene induction required the removal of the chorion prior to lipopolysaccharide exposure.