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Clinical and Diagnostic Laboratory Immunology, Jul 1996, 438-443, Vol 3, No. 4
M Lin, EA Sugden, ME Jolley and K Stilwell
The principle of fluorescence polarization described by Perrin (F. Perrin,
J. Phys. Radium 7:390-401, 1926) was applied to the development of a novel
assay that used fluorescein-labeled Mycobacterium bovis secretory protein
MPB70 for rapid detection of anti-MPB70 antibodies in selected sera from
three M. bovis-infected species (elk, Ilama, and bison). Labeling of
purified MPB70 with fluorescein isothiocyanate resulted in the
incorporation of 0.96 +/- 0.08 (mean +/- standard deviation; n = 3)
fluorescein group per MPB70 molecule. The labeled protein fluoresced
strongly with an emission maximum at 518 nm when excited with light of a
wavelength near 493 nm, and its immunoreactivity with anti-MPB70 monoclonal
antibody 4C3/17 was not altered by modification with fluorescein. The
fluorescence polarization assay protocol was optimized for analysis of
serum samples by incorporating into the assay buffer 0.05% lithium dodecyl
sulfate, which prevents the occurrence of some nonspecific interactions.
Sera from M. bovis-infected animals, selected on the basis of exhibiting
the presence of anti-MPB70 antibodies, as detected by enzyme-linked
immunosorbent assay (ELISA), reacted with fluorescein-labeled MPB70,
resulting in an increase in polarization of up to 330 milli- polarization
units, in contrast to the values for noninfected sera (167 to 178 mP),
which were close to that obtained in the absence of specific antibodies
(164.7 +/- 3.3 mP; n = 6). These results demonstrated the feasibility of
using fluorescein-labeled MPB70 to detect anti-MPB70 antibodies by
fluorescence polarization and suggested that the assay described here can
be an alternative to ELISA or other antibody assay systems. The advantages
of this original methodology and its general applicability to the diagnosis
of infectious diseases are discussed.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Modification of the Mycobacterium bovis extracellular protein MPB70 with fluorescein for rapid detection of specific serum antibodies by fluorescence polarization
Immunology Section, Animal Diseases Research Institute, Nepean, Ontario, Canada.
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