Immuno-reactivity pattern of secretory proteins of <em>Mycobacterium avium</em> subspecies<em> paratuberculosis</em> vaccine strain &lsquo;S 5&rsquo; with potential for diagnosis of Johne's disease in early infection

Abstract

Diagnosis of Johne's disease (JD) is hampered by the lack of specific immune-reactive antigens. Therefore, studies should be focused on the search of new candidate antigenic epitopes as 'novel biomarkers' for early diagnosis of JD. Secretory proteins profile of novel biotype (&lsquo;S 5&rsquo;) of 'Indian Bison Type' and their immuno-reactivity was studied in early growth period (4 &amp; 6 wk). Analysis of harvested CF (culture filterate) proteins was done by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Immunoblotting showed strong reactivity of 4 CF proteins (19, 36-38 and 65 kDa). Additional 48 kDa protein was recognized at 6 wk using MAP infected caprine serum. Diagnostic potential of early phase secretory proteins was evaluated using Indirect ELISA test. Results showed slightly lower sensitivity and 100.0% specificity with respect to whole cell sonicated semi-purified protoplasmic antigen (sPPA). Our earlier studies clearly exhibited that there cannot be universally effective diagnostic kits in case of chronic insidious diseases like Johne's disease. Therefore efforts should be to use antigen candidates from locally prevalent strains. By using commercially available universal kits we are unknowingly grossly under reporting the disease prevalence/incidence.