Length-dependent innate antiviral effects of double-stranded RNA in the rainbow trout (Oncorhynchus mykiss) cell line, RTG-2
2015
Poynter, Sarah J. | DeWitte-Orr, Stephanie J.
Effectively all viruses produce long dsRNA during their replicative cycle. In mammals long dsRNA molecules induce a robust response through the production of type 1 interferon, interferon-stimulated genes (ISGs) and an antiviral state. This response is less well understood in fish. We investigated the ability of a rainbow trout cell line, RTG-2, to respond to two different lengths of in vitro transcribed dsRNA (200bp and 1264bp) based on the viral hemorrhagic septicemia virus genomic sequence, and high and low molecular weight poly I:C (synthetic dsRNA). To explore the innate immune response we used qRT-PCR to measure immune gene transcript levels, an ISG-promoter reporter assay, and an antiviral protection assay. We saw a significantly greater immune response in all assays in response to the longer dsRNA molecule compared to their shorter counterpart. We saw significantly more interferon and ISG transcripts, stronger induction of a protective antiviral state, and more robust activation of the ISG-promoter. This response was not found to be due to a better uptake of the longer dsRNA molecules as a cellular uptake assay showed no differences between lengths. These data suggest that dsRNA-mediated innate immune responses are length-dependent and longer molecules induce a more robust response. There were also some differences in the cells response to in vitro transcribed dsRNA compared to poly I:C. This provides important information for potential dsRNA-based antiviral therapies and vaccine adjuvants.
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