Differential immunohistochemical expression of JSRV capsid antigen and tumour biomarkers in classical and atypical OPA: a comparative study

Abstract

ABSTRACT Ovine pulmonary adenocarcinoma (OPA) is a retroviral disease of sheep and occurs usually in two forms viz. classical and atypical, which differ in their histological lesions, cellular infiltrates, behaviour and prognosis. Present investigation was focussed to evaluate the differential expression of various tumour biomarkers in both OPA forms. Among 23 lung tissue samples suspected for OPA, histopathological examination diagnosed 12 as classical OPA, 6 as atypical OPA and 5 as bronchiolar hyperplasia. Polymerase chain reaction with LTR (long terminal repeat)-specific primers revealed that all classical and atypical OPA cases and three bronchiolar hyperplasia cases were positive for Jaagsiekte sheep retrovirus (JSRV) genome. Immunohistochemical (IHC) staining showed that JSRV capsid antigen was localized in the proliferating alveolar pneumocytes, bronchiolar epithelium and MNCs (mononuclear cells). Expression of PCNA was comparatively higher in classical OPA than atypical OPA and bronchiolar hyperplasia. Atypical OPA had higher MHC II expression than classical form indicated the higher proliferation of fibroblasts. FOXO3a expression is comparatively higher in OPA cases with mild inflammatory reaction while MMP2 expression was higher in OPA cases with severe inflammatory reaction. In conclusion, classical OPA is more proliferative and expansive in nature as compared to the atypical form. Further controlled study is required to prove the prognostic and metastatic potential of these markers in OPA.