Antigens of bovine respiratory syncytial virus in peripheral blood lymphocytes of experimentally infected lambs.

Eight lambs were experimentally infected with bovine respiratory syncytial virus (RSV) and the distribution of viral antigen in lymphocyte subpopulations studied by flow cytometry. Experimental infection with bovine RSV was characterised by significant changes in lymphocyte subpopulations. Infection was followed by a significant (P <0.001) reduction in the number of cells expressing the OvCD5 epitope (T cells), due to a fall in the number of cells expressing the OvCD4 epitope (helper) and those expressing the OvWC1 epitope (gamma/delta) 3-7 days post-inoculation. There was a significant increase in the number of OvCD5+ cells expressing the OvCD8 epitope (cytotoxic/suppressor) later. Flow cytometric analysis with bovine RSV-specific monoclonal antibodies revealed that viral antigens were present in all lymphocyte subpopulations but the main targets were T cells in general and OvCD4+ cells in particular. Challenge of primed lambs with bovine RSV had similar effects over a shorter period, followed by significant rises in the number of OvCD45+ (B) cells and OvCD5+ (T cells). Viral antigens were also present in lymphocytes subsets following challenge.