Bacterially expressed non-glycosylated recombinant bovine interferon lambda demonstrates antiviral activity against bovine viral diarrhea virus in cell culture

Bovine viral diarrhea virus (BVDV) is a pathogen of economic concern for the cattle industry due to reproductive losses, persistently infected animals, and for contributing to the bovine respiratory disease complex. Bovine interferon lambda 3 (IFN-λ3) is a type III interferon and a glycosylated cytokine with potent antiviral activity. The recombinant glycosylated bovine IFN-λ3 (rbIFN-λ3) has antiviral activity against BVDV in Madin-Darby bovine kidney (MDBK) cells. Bacterial expression systems provide a higher-yield and more cost-effective alternative to eukaryotic expression systems. The antiviral properties of bacterially expressed non-glycosylated rbIFN-λ3 against BVDV in cell culture was determined in this study. The coding sequence for the mature bovine IFN-λ3 was cloned into a bacterial expression vector and non-glycosylated rbIFN-λ3 was expressed and purified. Cells were pre-treated with serial dilutions of rbIFN-λ3 one day prior to infection with BVDV. The rbIFN-λ3 treatment was repeated daily, and viral infection status was assessed three days post-infection using immunohistochemistry with a monoclonal antibody specific to the BVDV E2 glycoprotein. A single band corresponding to non-glycosylated rbIFN-λ3 with the expected molecular mass was observed on SDS-PAGE, and the identity of rbIFN-λ3 was confirmed via western blotting. Our results indicated that bacterially expressed rbIFN-λ3 without glycosylation demonstrated concentration-dependent antiviral activity, effectively reducing BVDV replication. These results indicate that glycosylation is not required for the antiviral function of bovine IFN-λ3, and supports the potential of using bacterially expressed, non-glycosylated bovine IFN-λ3 in antiviral therapies against BVDV infections.