This study used in vivo assays to detect DC among SCEs. Cat extracts are currently standardized based on Fel d 1 (F). Nine SCEs were tested with Fs of 6.2 to 17.8 U/ml and with F to protein ratios (F/P) of 1.31 to 21.5. SCEs with low F/P were suspected to contain significant non-Fel d 1 (NF) allergen. Two cat sensitive populations were identified by skin testing: F+/NF- subjects; puncture reactive to SCE, but not to cat serum (no detectable F), and F+/NF+ subjects; reactive to both SCE and cat serum. Relative potencies (RP) of the various SCEs were determined by parallel-line skin test (PLST) against a SCE reference which contained significant NF allergen (F=11.8, F/P=1.93). There was a significant correlation (r=0.95, P<0.001) between RP based on PLST and RP based on F in F+/NF- subjects, but not in F+/NF+ subjects (r=0.32, P=0.4). The RP of two SCEs with F content similar to the reference, but with higher F/P ratios (10.6 and 21.5) were only 13-16% of the reference in F+NF- subjects (p=NS). These two SCEs were CD from the reference as were three other SCEs with higher F/Ps than the reference. Three SCEs with F/Ps equal or less than the reference were equipotent to the reference in F+/NF+ and F+/NF- subjects demonstrating they were compositionally similar (CS) to the reference. Because there is a subgroup (about 20%) of cat allergic patients who are sensitive to NF allergens, an assay to detect non-F allergens in addition to F is needed for standardization of cat extracts. This will insure lot to lot consistency in F and NF allergen composition, thus permitting labeling to accurately differentiate CD from CS cat extracts.

Agency
National Institute of Health (NIH)
Institute
Food and Drug Administration (FDA)
Type
Intramural Research (Z01)
Project #
1Z01BA001017-02
Application #
3792293
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
2
Fiscal Year
1992
Total Cost
Indirect Cost