INTERFERON-ALPHA RESPONSE TO SWINE ARTERIVIRUS (POAV), THE PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS

We studied the interferon-alpha (IFN-alpha) system in relation to the porcine arterivirus (PoAV), porcine reproductive and respiratory syndr ome virus (PRRSV). Recombinant porcine IFN-alpha inhibited the growth of this virus in alveolar macrophage cultures, When pigs were challeng ed intranasally with PoAV, their serum contained IFN-alpha in relative ly low concentrations on the second day after challenge and up to 5 da ys at the latest. Most animals had no IFN-alpha in their lung secretio ns, even though PoAV replicates in the respiratory tract. In vitro, Po AV replicates in alveolar macrophages, but neither these nor periphera l blood mononuclear cells (PBMC) produced IFN-alpha in response to inf ection. This may be because PoAV suppresses IFN-alpha production. When macrophages treated with PoAV were superinfected with swine transmiss ible gastroenteritis virus (TGEV), a known good inducer of IFN, no IFN -alpha was detected. This suppressive effect was lost when the virus w as inactivated by UV light. Our results suggest that downregulation of IFN-alpha production may play an important part in enabling PoAV to r eplicate in cell cultures and in pigs.