Searching for genomic control of pig viral vaccine and disease responses

Porcine reproductive and respiratory syndrome (PRRS) is the most economically important disease of pigs, resulting in annual losses of $664M/yr in the US. Vaccines are partially protective against this highly variable RNA virus infection. The PRRS Host Genetics Consortium (PHGC) was organized as a national effort to assess the role of genetics in determining pig resistance/susceptibility to PRRS virus infection, pathology and growth effects. The PHGC’s experimental plan involved a nursery pig PRRS virus infection model that included deep sampling for phenotypic analyses, extensive genotyping (60K SNPchip) and a shared database http://www.animalgenome.org/lunney/. This public-private partnership combined efforts of US and Canadian researchers and breeders; 15 trials were completed (10 with a 1997 PRRSV isolate, 5 with a 2006 isolate). A genomic region on swine chromosome 4 (SSC4) was confirmed as having a significant impact on variation in viral load and growth response following challenge. Most recently our PHGC research has expanded to challenges with both PRRSV and porcine circovirus (PCV2b) after PRRS vaccination. In addition field trials are being conducted with pigs predicted to be genetically resistant to PRRS. These trials will involve genotyping with the new 80K SNPchip and imputation from genotyping with smaller chips. These studies will help to validate effects of the SSC4 alleles on broader responses as well as to explore other chromosomal regions involved in immune, disease and vaccine response traits. This work is supported by USDA ARS and NIFA funds, National Pork Board, Genome Canada and Alberta grants and 6 pig breeding companies.