Innate immunomodulation with recombinant interferon-a enhances resistance of rainbow trout (Oncorhynchus mykiss) to infectious hematopoietic necrosis virus

We examined the in vivo immunostimulatory effects of a recombinant Atlantic salmon (Salmo salar) interferon-a2 (rSasaIFN-a2). The mature rSasaIFN-a2, expressed and purified from Escherichia coli, was administered to rainbow trout (Oncorhynchus mykiss) via the oral, immersion, or intraperitoneal (IP) injection route. Injection of rSasaIFN- a2 at 0.1 kg/g fish gave significantly greater protection than a phosphate buffered saline (PBS) injection against a lethal challenge of infectious hematopoietic necrosis virus (IHNV), with a relative percent survival of 39%. Relative percent survival (RPS) increased significantly to 92% when the fish were injected with rSasaIFN-a2 at 1 kg/g fish. Antiviral protection was evident for up to 7 days post-injection of rSasaIFN- a2. Administration of rSasaIFN-a2 by the oral or immersion route was not protective, and the fish succumbed to virus infection. The level of systemic IFN-induced expression of the Mx1 gene was significantly greater (p