Identification of candidate protein markers of Bovine Parainfluenza Virus Type 3 infection using an in vitro model.

Bovine Parainfluenza Virus Type 3 (BPI3V) infections are often asymptomatic, causing respiratory tissue damage and immunosuppression, predisposing animals to severe bacterial pneumonia, the leading cause of Bovine Respiratory Disease (BRD) mortality. As with many pathogens, routine BPI3V serology does not indicate the presence of damaged respiratory tissue or active infection. In vitro proteomic marker screening using disease relevant cell models could help identify markers of infection and tissue damage that are also detectable during in vivo infections. This study utilised a proteomic approach to investigate in vitro cellular responses during BPI3V infection to enhance the current understanding of intracellular host-virus interactions and identify putative markers of in vivo infection. Through 2D gel electrophoresis proteomic analysis, BPI3V Phosphoprotein P and host T-complex Protein 1 subunit theta were found to be accumulated at the latter stages of infection within bovine fibroblasts. These proteins were subsequently detected using targeted multiple reaction monitoring (MRM) mass spectrometry in the plasma of animals challenged with BPI3V, with differential protein level profiles observed dependant on animal vaccination status. Potential mechanisms by which BPI3V overcomes host cellular immune response mechanisms allowing for replication and production of viral proteins were also revealed. Assessment of circulating protein marker levels identified through an in vitro approach as described may enable more effective diagnosis of active viral infection and diseased or damaged respiratory tissue in animals and allow for more effective utilisation of preventative therapeutic interventions prior to bacterial disease onset and significantly aid the management and control of BRD.