Genetic control of swine responses to porcine reproductive and respiratory syndrome (PRRS) virus infection; Progress of the PRRS Host Genetics Consortium

Porcine reproductive and respiratory syndrome virus (PRRSV) is the most important infectious disease threat to pig production worldwide. The PRRS Host Genetics Consortium (PHGC) was established to probe the role of host genetics in resistance to PRRSV infection and related growth effects. Using a nursery pig model to assess pig resistance/susceptibility to primary PRRSV infection, 10 groups of 200 commercial crossbred pigs were infected with PRRSV and followed for 42 days post infection (dpi). Blood serum and Tempus (RNA) samples were collected at 10 timepoints and weekly weights recorded. Genomic DNA from PHGC1-8 pigs was genotyped with the Porcine SNP60 SNPchip for genome wide association studies (GWAS) [reported separately by Boddicker et al.] Infection results have affirmed that all pigs become PRRSV infected with peak viremia from 4-21 dpi. Bivariate statistical analyses of viral load and weight data have identified PHGC pigs in different high/low virus/weight categories. Sera and RNA are now being analyzed for immune and genetic factors involved in viral replication and recovery from infection, including speed and levels of immune cytokine expression using the Pigoligoarray, QPCR and fluorescent multiplex immunoassays. These analyses should identify biomarkers that distinguish PRRS resistant/maximal growth pigs from PRRS susceptible/reduced growth pigs. Overall, the PHGC project will enable researchers to verify important genotypes and phenotypes that predict resistance/susceptibility to PRRSV infection. The PHGC is funded by the US National Pork Board, USDA ARS, USDA NIFA PRRS CAP and functional genomic grants, NRSP8 Swine Genome and Bioinformatics Coordinators, and private companies.