Molecular characterization of woodchuck type I interferons and their expression by woodchuck peripheral blood lymphocytes

Interferon (IFN)-α and -β are important antiviral mediators. IFN-α is widely used for the treatment of chronic hepatitis B. In our previous studies, a subtype of woodchuck IFN-α (wIFN-α) was characterized and has been shown to be active in suppressing the replication of woodchuck hepatitis virus (WHV) in vitro and vivo. Here, we refined the analysis of the IFN-α/β system of the woodchuck and studied the expression of wIFN-α/β in peripheral blood lymphocytes (PBLs) from naïve and WHV-infected woodchucks. A number of wIFN-α genes were sequenced and could be classified into 10 subtypes and 3 pseudotypes. The biological activity of different subtypes of wIFN-α was demonstrated by their ability to protect woodchuck cells against encephalomyocarditis virus infection and to induce MxA expression in woodchuck cells. Additionally, a partial sequence of wIFN-β was characterized. A subtyping method for wIFN-α based on restriction length polymorphism analysis was developed. Further, the expression of wIFN by woodchuck PBLs after stimulation with polyI/C was investigated. The maximal production of wIFN by woodchuck PBLs occurred within the first 48 h after addition poly I/C. The wIFN-α subtypes 1, 4, and 5 were found to be produced by poly I/C-stimulated woodchuck PBLs, indicating a selective expression of wIFN-α subtypes. PBLs from chronically WHV-infected woodchucks showed a reduced ability to produce wIFN when stimulated with poly I/C. The results suggest that woodchucks with chronic WHV infection have impaired immunological responses to poly I/C.