Pantropic canine coronavirus induces canine M1 macrophage polarization in vitro

Abstract

Emerging coronavirus infections are a major threat to global public health. In this respect, a novel recombination of canine coronavirus (CCoV) and feline coronavirus (FCoV) was described among human biological samples, giving rise to a potential zoonosis. Despite all efforts, the host‒virus immune response related to CCoV is missing. In this study, pantropic CCoV infection of canine macrophages derived from peripheral blood monocytes was performed. After infection, macrophages were first polarized to the M1 and/or M2 phenotype. Moreover, infection kinetics, cell viability, apoptosis, mitochondrial dysfunction associated with reactive oxygen species and oxide nitric production were measured. Our results demonstrated that virus infection mainly polarized host macrophages to the classically activated (M1) phenotype, as demonstrated by amoeboid morphology with numerous fibrillary cytoplasmic processes followed by classical phenotypes. Viral infection released new particles at 18 h post-infection associated with a decrease in viable cells. Furthermore, upon CCoV infection, M1 cells exhibited reduced phagocytosis properties, as evidenced by a neutral red uptake assay. This in vitro method open an avenue for further studies on host-virus interaction.