Alpha-2-Macroglobulin as a New Promising Biomarker Improving the Diagnostic Sensitivity of Bovine Paratuberculosis.

Hyun-Eui Park,Jeong-Gyu Choi,Seung-Chul Baik,Donghyuk Kim,Jin-Sik Park,Min-Kyoung Shin,Myunghwan Jung,Woo-Kon Lee,Han Sang Yoo,Hong-Tae Park,Jeong-Ih Shin,Hyung-Lyun Kang

doi:10.3389/fvets.2021.637716

Abstract

Johne's disease (JD) is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP), which induces persistent diarrhea and cachexia. JD causes huge economic losses to the dairy industry due to reduced milk production and premature culling. Infected animals excrete MAP via feces during the prolonged subclinical stage without exhibiting any clinical signs. Therefore, accurate detection of subclinical stage animals is crucial for successful eradication of JD in the herd. In the current study, we analyzed serum samples of MAP-infected and non-infected cattle to identify potential biomarker candidates. First, we identified 12 differentially expressed serum proteins in subclinical and clinical shedder groups compared to the healthy control group. Second, we conducted ELISA for three selected biomarkers (alpha-2-macroglobulin (A2M), alpha-1-beta glycoprotein, and transthyretin) and compared their diagnostic performance with that of two commercial ELISA diagnostic kits. Serum A2M levels were significantly higher in the MAP-exposed, subclinical shedder, subclinical non-shedder, and clinical shedder groups than in the healthy control group, suggesting its possible use as a diagnostic biomarker for MAP infection. Furthermore, A2M demonstrated a sensitivity of 90.4%, and a specificity of 100% while the two commercial ELISA kits demonstrated a sensitivity of 67.83 and 73.04% and a specificity of 100%, respectively. In conclusion, our results suggest that measuring A2M by ELISA can be used as a diagnostic tool to detect MAP infection, considerably improving the detection rate of subclinical shedders and MAP-exposed animals that are undetectable using current diagnostic tools.

Highlights

Johne’s disease (JD) is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP) that causes significant economic damage to dairy industries worldwide [1]
For proteomic analysis for the serum proteins, 28 cattle were selected and classified into three groups according to the results of fecal qPCR analysis and the level of serum MAP antibodies detected by Enzymelinked immunosorbent assay (ELISA) as follows: [1] Healthy control group (n = 10): selected from a JD-free farm, negative for fecal PCR and serum ELISA. [2] Subclinical shedder group (n = 8): fecal PCR positive and ELISA negative
Eradication of JD in the herd can be achieved by detecting subclinical MAP infection, but the current diagnostic tools require improvement

Summary

Introduction

Johne’s disease (JD) is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP) that causes significant economic damage to dairy industries worldwide [1]. Johne’s disease (JD) is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. Paratuberculosis (MAP) that causes significant economic damage to dairy industries worldwide [1]. The primary hosts of MAP are farmed and free-range ruminants, including cattle, lamb, goat, and deer [1]. Several researchers have isolated MAP from various non-ruminant wildlife and captive animals such as rabbit, mice, rat, fox, raccoon, opossum, skunk, coyote, Cuban hutia, parrot, wallaby, and baboon which suggests the possibility of inter-species transmission [2,3,4]. During disease progression, infected cattle shed MAP with their feces, and bacterial shedding subsequently contaminates water, feed, milk, and the surrounding environment [1, 8]. Ingestion of MAP-contaminated materials is the primary route of infection. Rapid detection and culling of subclinical fecal shedder from herd are needed for the control of the JD [1, 8]

Methods

Results

Conclusion