Differential Biological Activities of Swine Interferon-α Subtypes.

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-α family. In pigs, there are 17 IFN-α 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-α 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-α2, -α5, -α9, and -α10 showed the highest level of activity in a pseudorabies virus yield reduction assay. On the contrary, little, if any, activity was shown by IFN-α3, -α7, -α13, -α4, and -α15. Anti-inflammatory activity: With the exception of IFNs-α2, -α7, -α9, and -α11, all IFN-α subtypes had significant anti-inflammatory control activity in an interleukin-8 (IL-8) yield reduction assay. Gene expression analyses showed that some IFN-α subtypes can significantly downregulate the expression of IL-8, tumor necrosis factor α (TNF-α), IL-6, Toll-like receptor 4 (TLR4), ßD1, and nuclear factor-κB (NF-kB) genes, while maintaining or upregulating the expression of ßD4. 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-α11, -α15, and -α16, which instead significantly downregulated class I MHC. Our results indicate that gene duplications in the porcine IFN-α family underlie diverse effector and regulatory activities, being therefore instrumental in host survival and environmental adaptation. This role of IFN-α could be founded on fine-tuning and regulation of pro- and anti-inflammatory control actions after exposure to both infectious and noninfectious environmental stressors.

Differential detection of classical swine fever virus challenge strains in C-strain vaccinated pigs.

BACKGROUND: Control of classical swine fever (CSF) by vaccination ideally requires that field strain infection can be detected irrespective of the vaccination status of the herd. To inform on the usefulness of molecular tests compatible with genetic Differentiation of Infected from Vaccinated Animals (DIVA) principles when using live-attenuated vaccines, tonsil homogenates from a vaccination-challenge experiment were analyzed using a differential real-time qRT-PCR for the C-strain vaccine or real-time qRT-PCR assays developed to specifically detect the challenge strains used. RESULTS: In animals with high or moderate levels of blood viraemia, which were not, or not fully, protected by vaccination, challenge virus RNA was readily detected in tonsil homogenates. In three out of the seven vaccinated animals that had high or moderate viraemia, the vaccine strain RNA also could be detected but at lower levels. Lower but varying levels of challenge and/or vaccine virus RNA were detected in tonsil homogenate samples from animals with no or low-level viraemia, and in groups solely consisting of such animals, no transmission of infection to naïve in-contact animals occurred. In one group of animals that were vaccinated 3 days prior to challenge, viraemia levels varied from high to absent and transmission of challenge virus to naïve in-contact animals occurred. The DIVA assay revealed challenge virus in all tonsil homogenates from this group, even in those animals that did not have viraemia and were protected from clinical disease by vaccination. Such animals, particularly in a low biosecurity/informal farm setting, could constitute a risk for disease control in the field. CONCLUSIONS: Genetic DIVA testing is useful for detecting the presence of field virus infection especially in non-viraemic animals without overt clinical signs but which are incompletely protected by vaccination. Such tests could particularly be useful to inform decisions prior to and during cessation of a control strategy that employs vaccination.