Immunohistochemical detection of intralesional antigens of Ovine gammaherpesvirus-2 in cattle with sheep-associated malignant catarrhal fever

Authors: HEADLEY, SELWYN - University Of Londrina; OLIVERIA, T.E.S. - University Of Londrina; LI, HONG - Retired ARS Employee; LISBÔA, J.A.N. - University Of Londrina; QUEIROZ, GUSTAVO - University Of Londrina; FRITZEN, J.T.T. - University Of Londrina; FLORES, EDUARDO - University Of Londrina; ALFIERI, AMAURI - Universidade Federal De Santa Maria; Cunha, Cristina

Submitted to: Journal of Comparative Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2019
Publication Date: 12/16/2019
Citation: Headley, S.A., Oliveria, T.E.S., Li, H., Lisbôa, J.A.N., Queiroz, G.R., Fritzen, J.T.T., Flores, E.F., Alfieri, A.A., Cunha, C.W. 2019. Immunohistochemical detection of intralesional antigens of Ovine gammaherpesvirus-2 in cattle with sheep-associated malignant catarrhal fever. Journal of Comparative Pathology. 174:86-98. https://doi.org/10.1016/j.jcpa.2019.11.002.
DOI: https://doi.org/10.1016/j.jcpa.2019.11.002

Interpretive Summary: Sheep-associated malignant catarrhal fever (SA-MCF) is a severe, frequently fatal, viral disease of cattle and other susceptible ungulates. The disease is caused by a herpesvirus known as ovine herpesvirus 2 (OvHV-2), which is transmitted by sheep worldwide. The disease is diagnosed based on the clinical and pathological manifestations and confirmed by the detection of viral DNA in tissues of affected animals. Although this approach is sufficient for diagnosis of MCF, it fails to demonstrate association between virus and lesions, which is critical to understand how the virus causes disease. In this study, we describe an immunological assay that can identify viral proteins and visualize lesions at the time in tissues of OvHV-2 affected animals. This developed assay is an important addition to the tools available to study SA-MCF. Therefore, it is expected to be largely used for MCF pathogenesis studies in the future and consequently helping advance knowledge in the field.

Technical Abstract: Sheep-associated malignant catarrhal fever (SA-MCF) is a severe lymphoproliferative disease of ruminants caused by ovine gammaherpesvirus-2 (OvHV-2). Since the initial identification of the SA-MCF there has been extensive research related to the pathogenesis of OvHV-2 based primarily on serological and molecular assays associated with typical histopathologic findings. The monoclonal antibody (MAb-15A) binds to a common epitope in MCF viruses and is frequently used in serological investigations. However, the utilization of this antibody to detect antigens of OvHV-2 in tissues was never demonstrated. Accordingly, this study standardized an immunohistochemical (IHC) assay using the MAb-15A to identify antigens of OvHV-2 in tissues of cattle (n=5) with SA-MCF. All animals developed acute neurological signs, without ocular and nasal manifestations, and contained nucleic acids of OvHV-2 in brain tissue by polymerase chain reaction. The principal histopathologic findings were lymphocytic nephritis (n=5), widespread arterial proliferation and vasculitis (n=5), lymphocytic portal hepatitis (n=3), nonsuppurative meningoencephalitis (n=2), and atrophic enteritis with cryptal necrosis and dilation (n=2). Intralesional intracytoplasmic antigens of OvHV-2 were identified within multiple epithelial cells of the kidneys of all animals, the intestines of animals with and without atrophic enteritis, and within epithelial cells of bile ducts in animals with lymphocytic hepatitis. Additionally, there was positive intracytoplasmic immunoreactivity within histocytes and histiocytes in several tissues. These findings suggest that the MAb-15A detects antigens of OvHV-2 within epithelial cells and leukocytes in several organs. Moreover, this IHC assay would contribute significantly towards the understanding of the pathogenesis of SA-MCF and may be an excellent tool for retrospective studies. Additionally, angiopathy in SA-MCF may be a progressive lesion, that may terminate in luminal occlusion and probably occurs irrespectively of the eye and head form of MCF.