ABSTRACT: Interferons (IFNs) play a crucial role in the host's immune response and other homeostatic control actions. Three IFN types and several IFN families within the types allow for a plethora of regulatory actions. The number of distinct IFN molecules is highest among type I IFNs and, in particular, within the IFN-? family. In pigs, there are 17 IFN-? subtypes with different antiviral activities and different expression profiles; however, no data are available about biological properties other than the antiviral effector activities. Therefore, 16 porcine IFN-? genes were cloned, expressed in mammalian Chinese hamster ovary cells, and characterized for antiviral, anti-inflammatory, and MHC-modulating activities at a pre-established level of 10?IU/mL. Antiviral activity: IFN-?2, -?5, -?9, and -?10 showed the highest level of activity in a pseudorabies virus yield reduction assay. On the contrary, little, if any, activity was shown by IFN-?3, -?7, -?13, -?4, and -?15. Anti-inflammatory activity: With the exception of IFNs-?2, -?7, -?9, and -?11, all IFN-? subtypes had significant anti-inflammatory control activity in an interleukin-8 (IL-8) yield reduction assay. Gene expression analyses showed that some IFN-? subtypes can significantly downregulate the expression of IL-8, tumor necrosis factor ? (TNF-?), IL-6, Toll-like receptor 4 (TLR4), ?D1, and nuclear factor-?B (NF-kB) genes, while maintaining or upregulating the expression of ?D4. Immunomodulation: A significant upregulation of class I and/or class II MHC was induced by all the IFNs under study, with the exception of IFNs-?11, -?15, and -?16, which instead significantly downregulated class I MHC. Our results indicate that gene duplications in the porcine IFN-? family underlie diverse effector and regulatory activities, being therefore instrumental in host survival and environmental adaptation. This role of IFN-? could be founded on fine-tuning and regulation of pro- and anti-inflammatory control actions after exposure to both infectious and noninfectious environmental stressors.
