Immunohistochemical Examination of TNF-α and SAA Expressions in Goats Infected with Mycobacterium avium subspecies paratuberculosis

Abstract

Paratuberculosis (Johne Disease), caused by Mycobacterium avium subspecies paratuberculosis (MAP) and commonly seen in ruminants, is a contagious disease that causes chronic diarrhea and serious economic losses. In this study, the presence of pro-inflammatory cytokine and acute phase protein expressions in lesional tissues of naturally infected goats with MAP was investigated. For this purpose, paratuberculosis suspected goats complaining of chronic diarrhea and excessive weight loss were examined by ELISA method for Mycobacterium avium subspecies paratuberculosis infection. After sacrificing 20 animals found to be infected with MAP, tissue samples taken from the intestines and lymph nodes were stained with Hematoxylin-Eosin (HE) for histopathological examination and Ziehl-Nelsen (ZN) to show acid-fast mycobacterium. Immunohistochemical staining was performed to examine the expressions of TNF-α as a pro-inflammatory cytokine and SAA as an acute phase protein. Macroscopic examination revealed in serous fat atrophy, mesenteric lymphadenitis, and granulomatous enteritis in the intestines. Histopathological examination revealed atrophy in villi, degeneration of enterocytes, inflammatory cell infiltration consisting mostly of mononuclear leukocytes in the mucosa, and epithelioid macrophage aggregation. Lymphoid hyperplasia and epithelioid histocyst aggregates were found in the mesenterial lymph nodes. In staining with ZN revealed the presence of bright red acid-fast agents in the intestine and mesenteric lymph nodes. In immunohistochemical examination, TNF-α and SAA expressions were observed in all samples. With this study, for the first time, the expressions of TNF-α, a proinflammatory cytokine, and SAA, an acute phase protein, were shown in the lesional tissues of MAP-infected animals, contributing to the immunopathogenesis of the disease.