P6007 Cell-type dependent immune response post porcine reproductive and respiratory syndrome virus infection

Abstract

The porcine reproductive and respiratory syndrome (PRRS) is one of the most important diseases of the global swine industry. The understanding of the responses to porcine reproductive and respiratory syndrome virus (PRRSV) as well as of the genetic elements and functions involved in the immune response to PRRSV was lacking. Therefore the aims of this study were to investigate the expression profiles and protein profiles of candidate genes which have a high impact on the host’s disease response to PRRSV in different respiratory cell types of two pig breeds (Pietrain and Duroc). To improve the understanding of genetic components and functions in the responses to PRRSV as well as to characterize changes in the immune gene expression a RNA-sequencing analysis of PRRSV infected Pietrain and Duroc lung DCs was performed and differently expressed candidate genes were obtained. The gene expression analyses of these candidate genes were done by qRT-PCR at six time points (0 h, 3, 6, 9, 12, 24 hpi) in three respiratory cell types: dendritic cells (DCs), pulmonary alveolar macrophages (PAMs) and trachea epithelial cells. Additionally, the cytokine concentrations of four (IFN-γ, IL-8, IL-1β and TNF-α) cytokines in cell culture supernatants were measured and were set in relation to the cytokine gene expression profiles. The gene expression trends with regard to 24 hpi proceeded for all respiratory cells contrarily. Investigations of the differently expressed genes showed a common reduced expression trend of the cytokines and chemokines for lung DCs. Other trends could be detected for PAMs as well as for trachea epithelial cells. There were more up-orientated gene expression trends for PAMs in comparison to the common down-orientated gene expression trends for lung DCs. Furthermore, the cytokine concentrations varied between Pietrain and Duroc and between DCs, PAMs and trachea epithelial cells. In conclusion, these various cell-type responses to PRRSV showed that there were different cell-type susceptibilities to PRRSV. With regard to time point 24 hpi the expression profiles of lung DCs led to the suggestion that these cells did not have enough power to stimulate other immune reactions. In contrast, PRRSV infected PAMs seemed to have enough capacity to give necessary signals to the immune system. These observed cell-type dependent differences should be taken into account for following investigations about immunity traits in pig breeding and about more effective vaccines.