The PRRS virus ( betaarterivirus suid , formerly also Porcine reproductive and respiratory syndrome virus ) is an RNA virus from the Arteriviridae family , subfamily Variarterivirinae , with a genome of approx. 15 kilobases with 8 ORFs (open reading frames). It is the causative agent of Porcine Reproductive and Respiratory Syndrome (PRRS), also known as epidemic late abortion in pigs (SSS), swine infertility and respiratory syndrome (SIRS), porcine epidemic abortion and respiratory syndrome (PEARS) .
There are two types of PRRS viruses in the Betaarterivirus genus , PRRSV-1 (subgenus Eurpobartevirus ) and PRRSV-2 (subgenus Ampobartevirus ), the genome of which differs by 40%. PRRSV-2 is common in Asia and the Americas. A highly pathogenic PRRSV-2 subtype, HP-PRRSV, arose in Asia. There are three subtypes of PRRSV-1 with different distribution in Europe and Asia.
As RNA viruses, PRRSV show a high mutation rate. As a result, assays have to be constantly adjusted and vaccinations have not been successful. What all subtypes have in common, however, is that they only attack certain macrophages in the lungs, namely those that carry the membrane receptor CD163. This consists of several globular domains lined up like a string of pearls , the fifth of which represents the docking point for the virus particles . Therefore, a line of pigs lacking the part of the gene ( intron 7) for the CD163 domain 5 was generated using the CRISPR / Cas method . In cell cultures from macrophages from these pigs, PRRSV of any subtype could not multiply. The animals, now in the third generation, are completely normal in growth and behavior - apparently the CD163 domain 5 is not vital for the organism - and could not be infected with a virulent strain of PRRSV-1 subtype 2 (no fever, no antibodies, viruses not detectable). Since the genetic modification in the CD163 gene can not be distinguished from a natural mutation , it is currently controversial whether these pigs should be classified as genetically modified organisms .
↑ KM Whitworth et al .: Gene-edited pigs are protected from porcine reproductive and respiratory syndrome virus. Nat Biotechnol 34, 2016, doi: 10.1038 / nbt.3434 .
↑ Christine Burkard et al .: Pigs lacking the scavenger receptor cysteine-rich domain 5 of CD163 are resistant to PRRSV-1 infection. Journal of Virology 92, 2018, doi: 10.1128 / JVI.00415-18 (free full text).