Peer-reviewed veterinary case report
New skin test for detection of bovine tuberculosis on the basis of antigen-displaying polyester inclusions produced by recombinant Escherichia coli.
- Journal:
- Applied and environmental microbiology
- Year:
- 2014
- Authors:
- Chen, Shuxiong et al.
- Affiliation:
- Institute of Fundamental Sciences
Plain-English summary
Researchers have developed a new skin test to detect tuberculosis (TB) in cattle that may be more accurate than current methods. The traditional test can sometimes give false positives because it reacts to harmless bacteria found in the environment. This new test uses three specific TB proteins that are only found in harmful bacteria, which helps to avoid confusion with non-pathogenic types. When tested on cattle, this new method successfully identified all animals infected with the TB bacteria without mistakenly identifying any healthy ones. Overall, the new test appears to work well for accurately diagnosing TB in cattle.
Abstract
The tuberculin skin test for diagnosing tuberculosis (TB) in cattle lacks specificity if animals are sensitized to environmental mycobacteria, as some antigens in purified protein derivative (PPD) prepared from Mycobacterium bovis are present in nonpathogenic mycobacteria. Three immunodominant TB antigens, ESAT6, CFP10, and Rv3615c, are present in members of the pathogenic Mycobacterium tuberculosis complex but absent from the majority of environmental mycobacteria. These TB antigens have the potential to enhance skin test specificity. To increase their immunogenicity, these antigens were displayed on polyester beads by translationally fusing them to a polyhydroxyalkanoate (PHA) synthase which mediated formation of antigen-displaying inclusions in recombinant Escherichia coli. The most common form of these inclusions is poly(3-hydroxybutyric acid) (PHB). The respective fusion proteins displayed on these PHB inclusions (beads) were identified using tryptic peptide fingerprinting analysis in combination with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The surface exposure and accessibility of antigens were assessed by enzyme-linked immunosorbent assay (ELISA). Polyester beads displaying all three TB antigens showed greater reactivity with TB antigen-specific antibody than did beads displaying only one TB antigen. This was neither due to cross-reactivity of antibodies with the other two antigens nor due to differences in protein expression levels between beads displaying single or three TB antigens. The triple-antigen-displaying polyester beads were used for skin testing of cattle and detected all cattle experimentally infected with M. bovis with no false-positive reactions observed in those sensitized to environmental mycobacteria. The results suggested applicability of TB antigen-displaying polyester inclusions as diagnostic reagents for distinguishing TB-infected from noninfected animals.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/24532066/