Investigation of zebrafish gills as a model to study respiratory immunology

Respiratory viral infections are routinely studied with animal models or in vitro culture which mimic but do not fully recapitulate elements of human immune responses or pathology. Studying events at the respiratory mucosa where infection is established is crucial to further our understanding of immune responses to these infections. In this thesis I evaluated the zebrafish gills as a novel in vivo model to study respiratory immunity. Using transgenic zebrafish, flow cytometry and several microscopy techniques I characterized immune cell composition and function in this tissue. In addition, I assessed the stimulatory effects of pathogen mimetics and derivatives on immune response pathways using RNA analysis. The stimulatory and pathological effects of live viral challenges were also assessed. These experiments highlighted the abundance and diversity of innate and adaptive immune cells in the gills from early to adult developmental stages. Some of these immune cells were capable of antigen-uptake and formed dynamic cell-cell interactions. Aggregates of T and B cells were identified as interbranchial lymphoid tissue which had some similarities but also some architectural differences to mammalian mucosal-associated lymphoid tissue. Different responses were stimulated by resiquimod and lipopolysaccharide highlighting these pathogen-related compounds as tools to interrogate immune pathways in the gills. On the other hand, zebrafish had limited responses to human respiratory or fish-endemic viruses and were resistant to pathological infection. These results highlight zebrafish gills as a useful model to investigate several aspects of immune cell function and inflammation in a respiratory mucosal in vivo setting. Further investigation with pathogens is needed to expand the use of this model for infection studies.Open Acces

Induction of innate cytokine responses by respiratory mucosal challenge with R848 in zebrafish, mice, and humans.

We compared live zebrafish, mouse and human nasal challenge responses to the TLR7/8 agonist resiquimod (R848). We found remarkably similar induction of mediators in the three species, offering novel mucosal models of innate anti-viral immunity