Genome-wide Analysis of Indicators of Oxidative Stress and Immune Response in Pigs Challenged with Porcine Circovirus 2b

Porcine circovirus 2 (PCV2) represents the main cause of Porcine Circovirus Associated Diseases (PCVAD) and impacts progression of other pathogens by compromising the swine immune system. This study investigated genetic sources of variation in immune response by profiling three indicators of oxidative stress and immune response in pigs experimentally infected with PCV2b. Blood was collected weekly during the 28 day experimental challenge period and serum was analyzed for total antioxidant capacity, TNF-alpha and haptoglobin via ELISA. Initial analysis of the tails of the distribution for viremia and growth during challenge showed that individuals with high viremia and low growth have increased antioxidant capacity (P < 0.06 at d 14 and P < 0.07 at d 21), high concentration of TNF-alpha (P < 0.10 at d 21) and haptoglobin (P < 0.13 at d 21) compared to individuals with low viremia and high growth. These results indicated a molecular response of increased stress following the first two weeks of challenge. The genetic factors associated with the variation of these indicators was evaluated by a genome-wide association study that included 56,433 SNPs. Pleiotropic sources of variation were investigated by comparing the genetic variance explained by 1 Mb windows of the swine genome across the targeted indicators and also across known measures of PCVAD progression such as PCV2 antibodies, viremia and growth.  These findings improve the knowledge of the impact that PCV2 has on the immune system and provide potential genetic and immune markers for profiling immune stress and PCVAD susceptibility.