In vitro permissivity of bovine peripheral blood mononuclear cells to bovine viral diarrhoea virus is dependent on the animal specific immune status

The in vitro permissivity to infection with homologous and heterologous bovine viral diarrhoea virus (BVDV) strains of bovine peripheral blood mononuclear cells (PBMCs) from eight naïve and eight BVDV-1b immune animals was studied. Four reference strains (BVDV-1a NADL, BVDV-1b NY-1, BVDV-2 125 and BVDV-2 890) were selected, based on genotype, prevalence and biotype. Virus neutralizing antibody titres were determined at bleeding and the viral loads were measured in PBMCs by end point titration in cell culture and by real-time PCR. PBMCs from both naïve and immune animals became infected by all BVDV strains tested, although virus titres were lower for immune heifers than naïve ones; the differences were significant for NADL (P < 0.05) and 890 (P < 0.001) strains. The in vitro model used in this study showed that PBMCs from immune animals are susceptible to re-infection with both homologous and heterologous BVDV strains, albeit at a lower extent than naïve cattle.