Cytopathic and non-cytopathic bovine viral diarrhoea virus biotypes affect fluid phase uptake and mannose receptor-mediated endocytosis in bovine monocytes

We have used non-cytopathic (ncp) and cytopathic (cp) bovine viral diarrhoea viruses (BVDV) to determine how the two biotypes affect mannose receptor (MR)-mediated endocytosis and fluid phase uptake in bovine monocytes. We have demonstrated that endocytosis in uninfected monocytes after 1 h of culture was mediated by the MR and fluid phase uptake, and after 24 h of culture it was mediated via fluid phase uptake only. Both cp and ncp BVDV affected the mechanisms of antigen uptake in monocytes. Endocytosis in BVDV infected monocytes, unlike in uninfected cells, was MR-independent and mediated by fluid phase uptake after 1 h of infection. The 24-h-BVDV infection changed the antigen uptake mechanisms to become MR- and fluid phase uptake-dependent. We conclude that antigen uptake, an important antigen presenting cell (APC) function, is affected in the early stage of BVDV infection during the first 24 h, with both BVDV biotypes, cp and ncp, having similar effects on monocyte antigen uptake in cattle. By influencing the early antigen uptake function of APC, BVDV might disrupt the function of monocytes as professional APC and contribute to the specific immunotolerance to BVDV.