Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/6/1998
Publication Date: N/A
Technical Abstract: The purposes of this study were to: 1) compare purified protein derivatives (PPD) prepared in the United States (USA) and PPD's prepared in Australia by CSL Veterinary (CSL) for stimulation of blood samples for a commercial gamma interferon (g-IFN) assay; and 2) determine the effect of skin testing on results of the g-IFN assay. Twenty cattle that were sensitized by subcutaneous injection of heat-killed Mycobacterium bovis were used. Cattle were randomly divided into three groups. Group A was skin tested on day 0 and day 7; group B was skin tested on day 0 and day 63; and group C was not skin tested. Blood samples for the g-IFN assay were collected at various times throughout the study period. Optical density (OD) values for the EIA were not significantly different when blood samples were stimulated with USA avian PPD and CSL avian PPD. The OD values were significantly higher when USA bovine PPD was used compared with CSL bovine PPD. However, ,the final interpretation of the g-IFN assay was the same when using either USA or CSL PPD's for all samples. In addition, OD results were significantly higher for blood samples collected after cattle were skin tested compared with samples collected from the same cattle before skin testing or from cattle not skin tested. These results indicate that skin testing cattle prior to collection of blood for the g-IFN assay may boost immuno-responsiveness and improve detection of cattle infected with or exposed to M. bovis.