In situ hybridization: an optimised detection protocol for a biotinylated DNA probe renders it more sensitive than a comparable 35S-labelled probe.

The development of a highly sensitive biotinylated in situ hybridization protocol using egg drop syndrome virus infection of domestic fowl as a model is described. This protocol incorporates the use of a monoclonal antibody to biotin as the initial step in a peroxidase-based detection system. The detection of viral nucleic acid in formalin-fixed, paraffin-embedded sections using biotinylated and 35S-labelled probes is compared to the detection of viral antigen by immunocytochemistry. Biotinylated probes detected more positive cells than 35S-labelled probes and were more specific. Biotinylated probes detected more positive cells than immunocytochemistry.