Submitted to: Clinical and Diagnostic Laboratory Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2005
Publication Date: 12/6/2005
Citation: Griffin, J.F., Spittle, E., Rodgers, C.R., Liggett, S., Cooper, M., Bakker, D., Bannantine, J.P. 2005. An IgG1 ELISA for Diagnosis of Johne's Disease in Red Deer (Cervus elaphus). Clinical and Diagnostic Laboratory Immunology. p. 1401-1409. Interpretive Summary: This manuscript represents our collective efforts to improve upon an antigen-antibody assay called the ELISA test for the serological diagnosis of Johne’s Disease (JD). In this study, we used Red Deer which are animals susceptible to Johne’s Disease and this is a concern/problem in New Zealand. But the results have applicability to JD in cattle as well. Basically, the study evaluated two different antigens in an IgG1 immunoglobulin type ELISA test. The results of these experiments showed a dramatic improvement in the sensitivity of the ELISA over the current test used in the field.
Technical Abstract: This study was designed to develop a customized ELISA assay for the serodiagnosis of Johne’s disease (JD) in farmed deer. Two antigens were selected on the basis of their superior diagnostic readouts: Purified Protein Derivative (PPDj) and undenatured protoplasmic antigen (PpAg). ELISA development was based on the antigen reactivity of the IgG1 immunoglobulin isotype, which is a highly specific marker for mycobacterial disease seroreactivity in deer. Sensitivity estimates, parameters and cut-points for the IgG1 ELISA were established using sera of 102 animals from more than 10 known infected deer herds with a broad spectrum of JD. A sample of 508 JD(-) animals, from five known disease-free herds, was used to determine specificity values. Using a ROC analysis and cut-off points of 50 ELISA units, the IgG1-based assay gave a specificity of 99.5% and sensitivity of 84.0% with PPDj antigen and 88.0% with PpAg; when the two major antigens were used in a serial test, the composite sensitivity increased to 91.0%. Test sensitivity was shown to be further improved using recombinant protein antigens unique for M. paratuberculosis, which identified infected animals that were unreactive to PPDj or PpAg. While 80% of animals that were seropositive in the IgG1 ELISA had detectable histopathology, the assay could also detect animals with sub-clinical disease. There was a significantly lower level (75%) of test sensitivity among animals that were culture positive for M. paratuberculosis but had no detectable pathology versus those with pathological evidence of JD (>90%). Finally, the IgG1 ELISA was employed to follow infection rates in deer herds over a four-year period. There was evidence from routine herd testing that an IgG1 ELISA could be used to eliminate clinical disease and identify juvenile animals with compromised production levels and increased susceptibility to fatal disease. The potential utility of serodiagnosis for the control of JD in farmed deer is discussed.