Basic knowledge of PRRSV infections and clues to successful PRRSV control have led to the discovery of type 1 interferon inhibition by several viral strains, which is purported to be instrumental in the dampening of the immune response. This study aimed to detect and dissect the type 1 interferon inhibition by the individual proteins of Type 2 strain MN184. The experimental approaches for identifying PRRSV type I interferon antagonist(s) utilized expressed MN184 proteins and a panel of type I interferon assays composed of a bioassay, an immunoassay and quantitative RT-PCR. The individual MN184 proteins were successfully expressed in MARC-145 cells. However, the assay results suggested that no inhibition of type 1 interferon by PRRSV strain MN184 could be detected using our devised MARC-145 cell assay, although some PRRSV nonstructural proteins, nsp3 and nsp7-11, induced a moderate amount of one class of type 1 interferon.