The Ex Vivo Infection of the Peripheral Bovine Mononuclear Cells (PBMCs) and the Bovine Spleen Cells with the Bovine Coronavirus (BCoV) Induced a Differential Expression of the Host Cytokine Genes Profiles and Modulates the Virus Replication

The adaptive immune response during BCoV infection of peripheral blood mononuclear cells (PBMCs), the bovine spleen cells, and their isolated T lymphocytes was not studied well. Our study confirmed successful BCoV infection in PBMCs and spleen T cells. This was evidenced by measuring genome copy numbers using real-time PCR, expression levels of BCoV spike and nucleocapsid proteins via western blot and immunofluorescence assays, and virus infectivity titration by plaque assay. In infected PBMCs, CD4 T-cell levels were 1.45-fold higher, and CD8 T-cell levels were 1.6-fold lower compared to sham-infected cells. Conversely, infected splenocytes showed a 0.88-fold decrease in CD4 T-cells and a 1.88-fold increase in CD8 T-cells. The cytokine gene expression analysis revealed that BCoV infection activated type 1 interferon and upregulated IL-6 expression in PBMCs and splenocytes. These findings demonstrate that BCoV successfully infects immune cells from PBMCs and spleen, inducing differential host cytokine gene expression favors virus replication.