Induction of type I interferons by a novel porcine reproductive and respiratory syndrome virus isolate.

Porcine reproductive and respiratory syndrome virus (PRRSV) is known to interfere with the signaling of type I interferons (IFNs). Here we found PRRSV A2MC2 induced type I IFNs in cultured cells. A2MC2 replication in MARC-145 cells resulted in the synthesis of IFN-α2 protein, transcript elevation of the IFN-stimulated genes ISG15 and ISG56, and the proteins of the signal transducer and activator of transcription 2 (STAT2) and ISG56. A2MC2 infection of primary porcine pulmonary alveolar macrophages (PAMs) also led to the elevation of the two proteins, but had little cytopathic effect. Furthermore, A2MC2 infection of MARC-145 or PAM cells had no detectable inhibitory effect on the ability of IFN-α to induce an antiviral response. Sequencing analysis indicated that A2MC2 was closely related to VR-2332 and Ingelvac PRRS MLV with an identity of 99.8% at the nucleotide level. The identification of this IFN-inducing PRRSV isolate may be beneficial for vaccine development against PRRS.