Comparative evaluation of Mycobacterium avium subspecies paratuberculosis (MAP) recombinant secretory proteins as DTH
Mukta Jain1, Amit Kumar Singh1, Manju Singh1
1Amity Center for Mycobacterial Disease Research, Amity University Rajasthan, Kant-Kalwar, Delhi-Jaipur Highway, NH11C, Jaipur 303 002, India.
Abstract:
Delayed type hypersensitivity (DTH) based skin test is an important onsite animal herd screening procedure for detecting the early stages of the chronic mycobacterial infections. DTH testing plays a vital role in the diagnosis of paratuberculosis infection. However, there are questions over the specificity of this test due to cross-reactive epitopes present on the purified protein derivative (PPD) prepared from the whole cell secretory proteins. PPD may contain proteins shared with other mycobacteria especially environmental species. Therefore, it is needed to test alternate paratuberculosis specific secretory antigens. Present study explored the potential of recombinant secretory proteins (MAP2168c, MAP1693c, MAP3547c, MAP4308c and MAP2677c) as DTH markers. The published literature shows that these proteins as strong cell mediated markers with specificity to paratuberculosis bacilli. To determine the positive skin thickness cutoff, herds of farm animals with history of endemic paratuberculosis were selected and thickness of >2.0 mm was reported as the positive cutoff. Preliminary findings on pilot scale animals report the usefulness of recombinant secretory proteins as DTH markers over traditional Johnin assay. Traditional Johnin reported more false positives and negatives compared to gold standard fecal PCR and field reference plate ELISA test. Present findings encourage and demand further research.
