Avian pathogenic Escherichia coli (APEC) strain-dependent immunomodulation of respiratory granulocytes and mononuclear phagocytes in CSF1R-reporter transgenic chickens

Avian pathogenic Escherichia coli (APEC) cause severe respiratory and systemic disease in chickens, commonly termed colibacillosis. CSF1R-reporter transgenic chickens express fluorescent protein under the control of elements of the CSF1R promoter and enhancer, such that cells of the myeloid lineage can be visualised in situ and sorted. Chickens were separately inoculated with APEC strains expressing GFP and culled 6 hours post-infection. Flow cytometric analysis was performed to phenotype and sort the cells that harboured bacteria in the lung, and the response of the sorted cells was defined by transcriptomic analysis. Our data indicate significant differences in the responses induced by APEC strains of prevalent serotypes, with important implications for the design and interpretation of future studies. Moreover, we show that bacterial invasion and survival in phagocyte populations in vitro is not predictive of events in the chicken lung.