Short Communication:Interferon-α Response to Swine Arterivirus (PoAV), the Porcine Reproductive and Respiratory Syndrome Virus

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Abstract
We studied the interferon-a (IFN-α) system in relation to the porcine arterivirus (PoAV), porcine reproductive and respiratory syndrome virus (PRRSV). Recombinant porcine IFN-α inhibited the growth of this virus in alveolar macrophage cultures. When pigs were challenged intranasally with PoAV, their serum contained IFN-α in relatively low concentrations on the second day after challenge and up to 5 days at the latest. Most animals had no IFN-α in their lung secretions, even though PoAV replicates in the respiratory tract. In vitro, PoAV replicates in alveolar macrophages, but neither these nor peripheral blood mononuclear cells (PBMC) produced IFN-α in response to infection. This may be because PoAV suppresses IFN-α production. When macrophages treated with PoAV were superinfected with swine transmissible gastroenteritis virus (TGEV), a known good inducer of IFN, no IFN-α was detected. This suppressive effect was lost when the virus was inactivated by UV light. Our results suggest that downregulation of IFN-α production may play an important part in enabling PoAV to replicate in cell cultures and in pigs.