Lung cell tropism and inflammatory cytokine-profile of porcine respiratory coronavirus infection

Knowledge about porcine respiratory coronavirus (PRCV) tropism was limited to morphological identification of target cells and controversial reports on replication in macrophages. This study aimed to clarify the lung cell tropism of a Belgian PRCV strain and to examine the lung profile of inflammatory cytokines for 15 days after intratracheal PRCV inoculation of gnotobiotic piglets. Until 5 days after inoculation, more than 50% of the PRCV-positive cells were type 2 pneumocytes, 30% bronchiolar epithelial cells, and 10% macrophages, as demonstrated by immunofluorescence stainings with specific cell markers. In vitro, PRCV productively infected primary porcine lung epithelial cells, but not porcine alveolar macrophages. Bronchoalveolar lavage fluids of PRCV-inoculated pigs contained high levels of interferons (IFN-α, IFN-γ) and interleukin-6, moderate interleukin-12 and low tumour necrosis factor-α levels. Our results indicate that PRCV infects primarily type 2 pneumocytes and induces lower lung cytokine levels, compared to swine influenza virus or lipopolysaccharide-complicated PRCV infections