Location of bovine respiratory syncytial virus antigens in the lung of experimentally-infected lambs: comparative study using indirect fluorescent antibody test, avidin-biotin-peroxidase complex and transmission electron microscopy.

The experiments were designed to analyse the efficiency of the Indirect Fluorescent Antibody Test (IFAT), the Avidin-Biotin-Peroxidase Complex (ABPC) and Transmission Electron Microscopy (TEM) in detecting Bovine Respiratory Syncytial Virus (BRSV) antigen in ovine lung. 25 gnotobiotic Merino lambs each received an intratracheal injection of 20 ml of BRSV infected cell culture suspension (strain NMK-7) diluted at the concentration of 1.26 x 10(6) TCID50/ml. Results showed that the immunological techniques were more efficient than transmission electron microscopy in detecting BRSV antigen. IFAT and ABPC yielded identical results. However, difficulties in interpreting aspecific fluorescence, coupled with the ease of identification of pneumonic areas from paraffin-embedded tissues, suggest that ABPC is the most suitable technique for identifying BRSV antigen in the lungs of experimentally-infected sheep.