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Research Paper
Tuberculin Purified Protein Derivative (PPD) Immunoassay as an In Vitro Alternative Assay for Identity and Confirmation of Potency
Mei M. Ho, Satnam K. Kairo and Michael J. Corbel
volume 2 | issue 1
january/february 2006Pages: 29 - 33
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Tuberculin purified protein derivative (PPD) currently can only be standardised by delayed hypersensitivity skin reactions in sensitised guinea pigs. An in vitro dot blot immunoassay was developed for both identity and possibly potency estimation of PPD. Polyclonal antibodies (mainly IgG) were generated and reacted with human, bovine and, to lesser extent, avian PPD preparations in immunoblotting assays. Various PPD preparations were analysed using SDS-PAGE coupled with Western blot and size exclusion chromatography (FPLC-SEC). The results showed that PPD preparations were mixtures of very heterogeneous tuberculoproteins ranging in size from very large aggregates to very small degraded molecules. All individual fractions of PPD separated by size were immunoreactive, although those of the largest molecular sizes appeared the most immunoreactive in this in vitro dot blot immunoassay. This method is very sensitive and specific to tuberculoproteins and can be an in vitro alternative for the in vivo intradermal skin assay which uses guinea pigs for identity of PPD preparations. Although the capacity of PPD to elicit cell-mediated immune responses on intradermal testing has to be confirmed by in vivo assay, the dot blot immunoassay offers a rapid, sensitive and animal-free alternative to in vivo testing for confirming the identity and approximate quantification of PPD preparations. The procedure would be particularly useful for national control laboratories for confirming the data of manufacturers and thus reducing the use of animals.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.