Modulation of the somatotropic axis, adiponectin and cytokine secretion during highly pathogenic porcine reproductive and respiratory syndrome virus type 1 (HP-PRRSV-1) infection

Porcine reproductive and respiratory syndrome virus (PRRSV) is known to be clinically responsible for reproductive failure in sows and post-weaning respiratory disease in growing piglets. During the last years, highly pathogenic PRRSV isolates have been discovered. In Italy, a PRRSV-1 subtype 1 strain (namely PR40/2014) characterized by high pathogenicity was isolated and experimental infection was characterized in terms of virological/clinical features and immune modulation (Canelli et al., 2017; Ferrari et al., 2018). The present study was performed in 4-week-old pigs experimentally infected with the highly pathogenic PRRSV1_PR40/2014 (HP-PR40) or with the conventional PRRSV1_PR11/2014 (PR11). The aim was to evaluate the interrelation between plasmatic hormones and cytokines in infected pigs compared to uninfected controls in order to address potential effects on the course of an experimental infection. The time-related changes of growth hormone (GH), insulin-like growth factor-1 (IGF-1), adiponectin, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels appear to be modulated by the infection depending on the PRRSV isolate (HP-PR40 vs. PR11). In particular, in HP-PR40 infected animals, the association between high GH levels and viremia may testify the need to block the anabolic action of GH in order to shift available energy towards the immune response. This need appeared to be delayed in PR11 animals, given the lower pathogenicity of the isolate. Adiponectin, IL-6 and TNF-α course supports the hypothesis of GH resistance mechanisms to guarantee homeostasis in HP-PR40 animals and underlines the key role of energy availability in events leading to an effective response to the virus.