Clinical evaluation of a peptide-ELISA based upon N-terminal B-cell epitope of the VapA protein for diagnosis of Rhodococcus equi pneumonia in foals
Date
2006
Authors
Phumoonna, T.
Muscatello, G.
Chicken, C.
Gilkerson, J.
Browning, G.
Barton, M.
Heuzenroeder, M.
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Advisors
Journal Title
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Type:
Journal article
Citation
Zoonoses and Public Health, 2006; 53(3):126-132
Statement of Responsibility
T. Phumoonna, G. Muscatello, C. Chicken, J. R. Gilkerson, G. F. Browning, M. D. Barton and M. W. Heuzenroeder
Conference Name
Abstract
<jats:title>Summary</jats:title><jats:p>A total of 227 field samples from naturally exposed foals aged between 3 weeks and 6 months were used in an evaluation of a peptide‐based enzyme‐linked immunosorbent assay (ELISA) for diagnosis of<jats:italic>Rhodococcus equi</jats:italic>infection. A biotinylated peptide derived from the virulence‐associated protein A (VapA) of<jats:italic>R. equi</jats:italic>, a horse pathogen, was synthesized and designated as PN11‐14. The peptide corresponds to the N‐terminal B‐cell epitope TSLNLQKDEPNGRASDTAGQ of the VapA protein. Based upon a serum immunoglobulin (Ig)G titre of 512 as a positive cut‐off value for the<jats:italic>R. equi</jats:italic>infection, the ELISA provided the overall sensitivity of 47.62%, specificity of 69.67% and an accuracy of 59.47% with a positive predictive value of 57.47% for true<jats:italic>R. equi</jats:italic>pneumonia. The assay was improved by detecting VapA‐specific IgGb antibodies against N‐terminal B‐cell epitope of the VapA protein rather than IgG antibodies. The VapA‐IgGb ELISA showed the overall sensitivity of 70.47%, specificity of 72.13% and accuracy of 71.36% with a positive predictive value of 68.52%. Diagnosis of<jats:italic>R. equi</jats:italic>disease in 6‐week‐old foals showed that the VapA‐IgGb ELISA provided an increasing trend (<jats:italic>P</jats:italic> = 0.0572) in sensitivity of 82.4% in comparison with the VapA‐IgG ELISA which showed the sensitivity of 58.8%. However, differences in specificity of both tests were statistically insignificant (<jats:italic>P</jats:italic> = 0.357) as analysed by the McNemar test. These results indicated that detection of VapA‐specific IgGb antibodies may be a better predictor of<jats:italic>R. equi</jats:italic>disease in foals.</jats:p>
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Published Online: 30 Mar 2006
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Copyright © 2006 The Authors Journal compilation 2006 Blackwell Verlag, Berlin
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