GENE SIGNATURES ASSOCIATED WITH FOOT-AND-MOUTH DISEASE VIRUS INFECTION AND PERSISTENCE PART I: PERSISTENT FMDV INFECTION IN AN AIR-LIQUID INTERFACE MODEL OF BOVINE SOFT PALATE
Résumé
Persistent foot-and-mouth disease virus (FMDV) delays the process to recover a free status without stamping out of infected animals. In carrier cattle, which harbour FMDV >28 days post infection (DPI), replicating virus has been detected in epithelial cells in the nasopharynx and soft palate (SP). It has been suggested that, to trigger this persistence, FMDV suppresses the host defence or mutates to escape immunity. The aim of this study was to develop a model to be able to characterise gene signatures within FMDV and its target cells. The overall goal was to identify factors that can be used to prevent or diagnose persistent infection.
An air-liquid interface multilayer model of SP cells from cattle was developed and was characterised by immunostaining and electron microscopy. After five weeks of culture without passage, the cells were infected at an MOI of 0.01 or 1 with FMDV O/FRA/1/2001 and the infection was monitored by isolation in cell culture, RT-qPCR, immunofluorescence and immunohistochemistry, until 28 DPI.
At the time of infection, approximately 20% of cells had still a polygonal morphology and displayed tight junctions, such as observed in stratified squamous epithelia. Cells with similar morphology expressed cytokeratin. A limited cytopathic effect was induced, restricted to the upper cell layers. FMDV antigen, FMDV RNA and live FMDV were detected through day 1 to 28, with peaks at day 1 and 2. At day 28, FMDV antigen could still be detected in sparse cells.
The air-liquid interface model allowed culture of SP cells in multilayers, without disruption during passage. Epithelial cell characteristics such as cytokeratin expression and tight junctions were preserved in a subset of cells during 9 weeks of culture. The detection of FMDV until 28 DPI opens unique possibilities to investigate FMDV persistence in a controlled manner. Transcriptomic data will be presented in a joint publication.