PRE-TREATMENT WITH POLY(I:C) CONFERS PARTIAL PROTECTION AGAINST FROG VIRUS 3 IN TWO PERMISSIVE XENOPUS LAEVIS SKIN EPITHELIAL CELL LINES
Maxwell Marinos, University of Waterloo
Maxwell P. Bui-Marinos, Marie-Claire D. Wasson, Barbara A. Katzenback
Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
Frog Virus 3 (FV3) is known to cause mass mortalities in amphibian populations on a global scale. While skin acts as the first barrier of defense between a host and its environment, the role that frog skin epithelial cells play in recognition and response to FV3 is largely unknown. To better elucidate skin epithelial cell-FV3 interactions, we used newly established epithelial cell lines from Xenopus laevis dorsal skin (Xela DS2) and ventral skin (Xela VS2) tissues. To determine susceptibility to FV3, Xela DS2 and Xela VS2 were incubated with a multiplicity of infection (MOI) ranging from 0.002 to 20 and cytopathic effects and viral titre monitored. Doseand time-dependent increases in infective virions, coinciding with cytopathic effects and loss of cell adherence, were observed. Assessment of Xela DS2 and Xela VS2 immunocompetence and response to FV3 were performed by detection of pro-inflammatory and anti-viral transcripts via RT-qPCR following treatment with poly(I:C), FV3 or UV-inactivated FV3. While both cell lines exhibited an increase in proinflammatory and antiviral transcripts following poly(I:C) stimulation, no change in transcript levels were observed following challenge with FV3 or UVinactivated FV3. However, poly(I:C) pre-treatment of Xela DS2 and Xela VS2 prior to FV3 challenge reduced cytopathic effects and production of infective virions. These data demonstrate that frog skin epithelial cells are permissive to FV3 and, while FV3 appears to effectively supress key innate immune functions in Xela DS2 and Xela VS2, pre-treatment of these cells with poly(I:C) can effectively limit viral replication.