G.N. Hansen

Assay for the major dog allergen, Can f I: Investigation of house dust samples and commercial dog extracts

Monospecific rabbit antibodies were used to develop a sensitive two-site enzyme immunoassay to measure a major dog hair and dander allergen, Can f I. This Can f I assay demonstrated no reaction with 17 heterologous allergen sources, including dog albumin, cat, guinea pig, and horse. Analysis of serial dilutions of purified Can f I and the international standard for dog was parallel. The assay was considered specific for Can f I with a lower limit of detection at 0.03 micrograms/ml. Total imprecision was from 2% to 6%. Commercial dog extracts for specific immunotherapy contained from 0.7 to 290 micrograms of Can f I per milliliter. The assay was used to measure Can f I in 136 house dust samples collected from 103 homes across the United States. Concentration of the dog allergen was expressed as micrograms of Can f I per gram of dust. Prevalence of Can f I in the dust samples ranged from less than 0.3 to 10,000 micrograms/gm. Serial dilutions of samples containing Can f I were parallel to the standard. The median Can f I value for homes with a dog in residence was 120 micrograms/gm, and for homes with no dog, 3 micrograms/gm. With few exceptions, homes with no dog in residence had less than 10 micrograms/gm. This Can f I assay will provide useful information for assessing commercial extracts as well as monitoring dog-allergen exposure and allergen-control methods.

Cow Hair Allergen (Bos d 2) Content in House Dust: Correlation with Sensitization in Farmers with Cow Hair Asthma

Farmers (N = 45) suffering from occupational cow hair asthma were visited at home to evaluate the concentration of cow hair major allergen Bos d 2 in the house dust and to correlate these results with measures of avoidance, degree of sensitization, clinical symptoms, and lung function. Bos d 2 was determined by rocket immunoelectrophoresis. In dust of tiles and linoleum Bos d 2 was difficult to detect, whereas dust samples of carpets often contained high concentrations of the allergen (50-520 micrograms/g fine dust). Bos d 2 levels were significantly higher when barn and living quarters were in the same building. Concentrations of cow hair-specific IgE were correlated with concentrations of Bos d 2 in house dust samples. A concentration of 20-29 micrograms Bos d 2 per gram of house dust could be established as threshold value for relevant IgE sensitization. Avoiding the barn is not a sufficient avoidance measure for cow hair asthmatics if the partner continues cattle farming. Cessation of cattle farming and avoiding the former barn results in a marked reduction in Bos d 2 concentration in living quarters, a decreased degree of sensitization, and a reduced symptom score. Farmers with cow hair asthma should avoid cattle and thoroughly clean all carpets in the living quarters to avoid continuous cow allergen exposure.

Immunoelectrophoresis for the Characterization of Allergen Extracts

Immunoelectrophoresis can be used for analysis of individual proteins in complex mixtures. The conditions involved in immunoelectrophoresis are mild, avoiding the risk of denaturation, and it is possible to perform relative quantification of individual components. The principle disadvantage is the dependence on rabbit antisera as reagents. The usefulness of immunoelectrophoresis in allergy research is greatly enhanced by the possibility of identification of allergens to which the individual in question has IgE. The common principle is characterized by two independent electrophoreses having direction of current perpendicular to each other, i.e., crossed immunoelectrophoresis (CIE). This ultimately results in the formation of characteristic bell-shaped precipitates, each precipitate representing one antigen. There is a linear relationship between the amount of antigen and size of precipitate for a given antibody concentration for each precipitate and so relative quantification can be performed. The sensitivity and resolution power of CIE is very high and there are multiple variations of the technique, some of which will be illustrated in this chapter.