The Hansen laboratory has been working on the development of alternative models for studying host-pathogen interactions using two teleost fish, rainbow trout and zebrafish, as model vertebrates. We are primarily interested in the induction of innate immunity and the transition of innate to adaptive immunity as they pertain to intracellular pathogens. Our current research focuses on the transcriptional regulation of host genes (functional genomics) and the cellular immune response(s) (CD4/CD8 responses) to infection and vaccination (attenuated/inactivated/DNA). Pathogens currently under investigation include IHNV (fish rhabdovirus), Streptococcus iniae (zoonotic agent) and Francisella victoria (restricted to fish). A general theme for the lab is basic comparative immunology, including the overall evolution of immunity. Therefore, by using these comparative model systems, we can learn more about common factors that mediate both virulence and immunity in all vertebrates.