It has been suggested that CD163 is the receptor for entry of PRRSV into cells. Researchers hypothesized that pigs with defective CD163 would be immune to PRRSV. The results of this study demonstrate that these animals are resistant to the PRRSV isolate NVSL 97-7895, a well-characterized, relatively virulent viral isolate commonly used in experimental PRRSV infection trials. After infection, they showed no clinical signs (fever or respiratory signs), lung pathology, viremia or antibody response and remained healthy for the 35 days after infection measured in this study.
Kristin M Whitworth, Raymond R R Rowland, Catherine L Ewen, Benjamin R Trible, Maureen A Kerrigan, Ada G Cino-Ozuna, Melissa S Samuel, Jonathan E Lightner, David G McLaren, Alan J Mileham, Kevin D Wells, Randall S Prather; Gene-edited pigs are protected from porcine reproductive and respiratory syndrome virus; Nature Biotechnology (2015); doi:10.1038/nbt.3434; Published online 07 December 2015
http://www.nature.com/nbt/journal/vaop/ncurrent/full/nbt.3434.html