Immunohistological localisation of rinderpest virus in formalin-fixed, paraffin-embedded tissues from experimentally infected cattle

A review of three pathology-based techniques for retrospective diagnosis of rinderpest, with comparison to virus isolation

Base of tongue, eyelid, and retropharyngeal lymph node were collected from three animals experimentally infected with rinderpest and utilised in a study comparing virus isolation with histopathology, immunohistochemistry, and in situ hybridisation to determine the usefulness of the latter three techniques as retrospective diagnostic aids for this disease. Virus isolation was positive for all nine samples. Histopathology was suggestive in all the tissues and definitive in some. Immunohistochemistry and in situ hybridisation highlighted the presence of rinderpest antigen of rinderpest nucleic acid in all of the sections. However, in situ hybridisation was more specific than immunohistochemistry.

Immunohistochemical detection of rinderpest virus: effects of autolysis and period of fixation

Samples of eyelid, tongue, soft palate and palatine tonsil were collected from calves infected experimentally with rinderpest virus. The tissues were fixed in 10 per cent neutral buffered formalin immediately, 24 or 48 hours post mortem. Then, after three days, 10 days, 28 days or three months in formalin, they were processed into paraffin blocks and examined immunohistochemically for rinderpest viral antigen. The tonsil was the best of the four tissues in providing a consistently positive immunohistochemical signal for the presence of virus, despite autolytic changes and/or prolonged fixation.

Distribution of antigen in cattle infected with rinderpest virus

Five Holstein heifers (approximately 8 months of age and weighing 225-275 kg) were inoculated subcutaneously with 1,000 TCID50 of rinderpest virus, virulent Kabete O strain. They become clinically ill 2 to 5 days post-inoculation, with fever (40 C to 41.5 C), conjunctivitis, and diarrhea. All were euthanatized when moribund at 6 days postinoculation. The following tissues were collected in formalin, embedded in paraffin, and subsequently subjected to histopathologic and immunohistochemical examination: tongue, buccal mucosa, soft palate, esophagus, rumen, abomasum, duodenum, jejunum with and without Peyer's patch, ileum, cecum, proximal colonic lymphoid patch, spiral colon, eyelid, gall bladder, spleen, tonsil, trachea, lungs, and numerous lymph nodes. Immunohistochemical examination was accomplished using a primary rabbit anti-rinderpest antibody, and either a peroxidase-diaminobenzidine or alkaline phosphatase-Vector Red detection substrate system. In the lymph nodes, spleen, and tonsil, depletion of lymphocytes from all areas was extensive, with antigen most prominent in persisting reticular cells throughout the tissues. In the intestine, necrotizing and ulcerative changes in the mucosa were extensive and widespread. Damage was most severe in areas overlying lymphoid patches. In both small and large intestine, antigen was distributed predominantly in epithelial cells, histiocytic cells in the lamina propria, and in remaining reticular cells of lymphoid patches. In oral mucosa, there were multiple ulcerations and numerous multinucleate syncytial cells, both containing and without antigen. Lungs and trachea had subtle yet consistent necrosis of epithelial cells, with antigen often distributed in a circumferential manner in epithelium of bronchioles.