The Role Of HPA Axis In The Piglets During Highly Pathogenic Porcine Reproductive And Respiratory Syndrome Virus Infection

Porcine reproductive and respiratory syndrome(PRRS) is caused by PRRS virus(PRRSV). From2006, HP-PRRS attacked the swine industry, resulting in serious economic loss to the pig industry inour country. PRRSV induces severe immune organs lesions in piglets, and cause severe host immuneresponse disorders.Hypothalamus-Pituitary-Adrenal axis(HPA) plays an important role in neuroendocrine-immunesystem in mammals. It can be activated by high levels of pro-inflammatory cytokines which are releasedby immuno-cells during animals are infected by different kinds of pathogens. Subsequently, the functionof immune system is regulated by the glucocorticoids(GCs) secreted by HPA system.Our previous studies showed that HP-PRRSV infection induced high level of pro-inflammatorycytokines in the peripheral blood, and these infected piglets showed high body temperatures,accompanying with severe thymus atrophy, lymphocytes apoptosis and higher mortality than thatinduced by classical PRRSV infection. In this study, to investigate the influence of HPA to HP-PRRSVinfected piglets, piglet were infected with HP-PRRSV HuN4 strain, the concentrations of relatedhormones was detected. Then, the special antagonist of glucocorticoids receptor(GR)-RU486 and DEXwere used to these piglets during HP-PRRSV HuN4 strain infection. The results showed that from 7 to10 days post infection, the adrenocorticotropic hormone(ACTH), corticotropin-releasing hormone(CRH) and glucocorticoids concentrations in peripheral blood of the infected piglets were significantlyhigher than that of control piglets, histopathology changes of the hypothalamus showed inflammatorycells infiltration around the blood vessels, and microglial-nodes happened apoptosis. These piglets usedRU486 or DEX during HuN4 infection up to 100% mortality, and the rectal temperatures of thesepiglets were 40-42 o C, which is more severe than that of HuN4 group. Besides, the piglets used RU486 presented suppurative pneumonia after 10 days post infection. The piglets used DEX(0.5 and2mg/kg-weights) showed mild proinflammatory cytokines IL-1β, IL-6, TNF-α response and lymphocytesubsets in peripheral blood changes compared to the HuN4 group. These results both RU486 and DEXcan affect host anti-inflammatory during HP-PRRSV infection, which make more bad effects on piglets.This study provided the new experimental basis of comprehensively prevention of HP-PRRSV.