Cat allergen content of commercial house dust extracts: Comparison with dust extracts from cat-containing environment

Abstract

Eighteen lots of house dust extract from nine commercial sources (obtained as weight per volume or protein nitrogen unit per cubic centimeter) were analyzed for cat allergen content by direct quantitative immunoelectrophoresis after concentration. Cat allergen 1 was measurable (>0.3 units) in 11 extracts with a mean (range) of 5.8 (1.3 to 31.0) U/gm of source material. Cat albumin was measurable (>2.4 units) in 12 extracts with a mean (range) of 53.4 (11.5 to 319.7) U/gm. In order to evaluate whether the cat allergen 1 content is a significant contribution to the allergenic activity of the extract, 17 cat-allergic subjects were tested by prick test with a purified preparation of cat allergen 1. The mean (range) concentration that produced a 3 mm wheal was 0.01 (0.0013 to 1.33) U/ml. Therefore, the commerical house dust extracts studied, when these extracts were diluted to a concentration commonly used for prick testing, would frequently contain enough cat allergen 1 to produce strong prick test reactions in cat-allergic subjects. It is difficult to justify the use of such commerical dust extracts as diagnostic reagents. For comparison purposes, nine dust samples from an apartment housing two cats were similarly analyzed. Cat allergen 1 was measurable in seven samples with a mean (range) of 23.8 (1.8 to 64.3) U/gm. Cat albumin could be measured in all nine samples with a mean (range) of 32.3 (0.16 to 70.8) U/gm. The average amount of cat allergen 1 that could be washed off the surface of the cats was 270 units. Large reservoirs of cat allergen 1 were present. The spread on which the cats commonly slept contained 20,000 units of cat allergen 1. Contamination of a pool of house dust samples with dust from a cat-containing environment would likely be significant.