Hypothalamus-pituitary-adrenal axis involves in anti-viral ability through regulation of immune response in piglets infected by highly pathogenic porcine reproductive and respiratory syndrome virus

Background The highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) has been responsible for several viral attacks in the Asian porcine industry, since the first outbreak in China in 2006. During the early stages of the HP-PRRSV infection, high levels of proinflammatory cytokines are noted in the host peripheral blood, which are accompanied by severe lesions in the lungs and immune system organs; these are considered as the greatest contributors to the overall disease burden. We hypothesized that the anti-PRRSV response in piglets might be mediated by the hypothalamus-pituitary-adrenal (HPA) axis, which led to a decrease in the psycho-neuroendocrinological manifestation of HP-PRRSV etiology via immune response regulation. Results We investigated the regulation of the HPA axis in HP-PRRSV-infected piglets that were treated with 1 mg/kg body weight (b. w.)/day mifepristone (RU486) or 2 mg/kg b.w./day dexamethasone (DEX). Both RU486 and DEX enhanced the disease status of the piglets infected by the HP-PRRSV HuN4 strain, resulting in high mortality and more severe pathological changes in the lungs. Conclusions HP-PRRSV infection activates the HPA axis, and artificial regulation of the immune-endocrine system enhances disease severity in HP-PRRSV-infected piglets. Thus, DEX and RU486 should be avoided in the clinical treatment of HP-PRRS.