Fel d 1

Abstract: Background Asthma-associated morbidity is rising, especially in inner city children. Objective We evaluated the allergen sensitivities, allergen exposures, and associated morbidity for participants in the Inner City Asthma Study. We also determined geographic variations of indoor allergen levels. Methods Nine hundred thirty-seven inner city children 5 to 11 years old with moderate to severe asthma underwent allergen skin testing. Bedroom dust samples were evaluated for Der p 1, Der f 1, Bla g 1, Fel d 1, and Can f 1. Results Skin test sensitivities to cockroach (69%), dust mites (62%), and molds (50%) predominated, with marked study site–specific differences. Cockroach sensitivity was highest in the Bronx, New York, and Dallas (81.2%, 78.7%, and 78.5%, respectively), and dust mite sensitivity was highest in Dallas and Seattle (83.7% and 78.0%, respectively). A majority of homes in Chicago, New York, and the Bronx had cockroach allergen levels greater than 2 U/g, and a majority of those in Dallas and Seattle had dust mite allergen levels greater than 2 μg/g. Levels of both of these allergens were influenced by housing type. Cockroach allergen levels were highest in high-rise apartments, whereas dust mite allergen levels were highest in detached homes. Children who were both sensitive and exposed to cockroach allergen had significantly more asthma symptom days, more caretaker interrupted sleep, and more school days missed than children who were not sensitive or exposed. Conclusion Geographic differences in allergen exposure and sensitivity exist among inner city children. Cockroach exposure and sensitivity predominate in the Northeast, whereas dust mite exposure and sensitivity are highest in the South and Northwest. Cockroach allergen appears to have a greater effect on asthma morbidity than dust mite or pet allergen in these children.

Abstract: The recent development of a sensitive two-site monoclonal antibody immunoassay for the major cat allergen (Fel d I) has made it possible to make accurate measurements of airborne cat allergen using low volume samplers that do not disturb the room. Houses with cats had from 2 to 20 ng Fel d I/m3 air compared with less than 0.2 ng/m3 in houses without cats. Using a cascade impactor and a multistage liquid impinger, the particle size distribution of airborne Fel d I in nine houses was 75% on particle greater than or equal to 5 microns in diameter and 25% (range, 10 to 62%) on particles less than or equal to 2.5 microns. In a cat vivarium with 12 cats, the air contained 40 ng Fel d I/m3, but less than 2% was detected on particles less than or equal to 2.5 microns. The air exchange rate in the vivarium (approximately 15 changes/h) appears to be the major difference from domestic houses (less than 0.5 changes/h). Repeated studies in one house confirmed a very high proportion (approximately 60%) of Fel d I on small particles. During domestic cleaning, the levels of small particle allergen in this house approached those produced by a nebulizer for bronchial provocation, i.e., 40 ng/m3. These results show unequivocally that significant airborne Fel d I is associated with small particles, which remain airborne for long periods. These findings are strikingly different from previous results obtained with airborne dust mite allergen. The results provide an explanation for the distinctive rapid onset of asthma or rhinitis in patients allergic to cats and a basis for designing a policy to reduce airborne allergen in houses with cats.

Abstract: Two mAb were used to develop new techniques for the purification and quantitation of the major feline salivary allergen, Felis domesticus allergen I (Fel d I). The allergen was purified from aqueous house dust extract with a high Fel d I content by affinity chromatography over a monoclonal immunosorbent and elution with 4 mM HCl, pH 2.5. This single step procedure gave 40 to 50% recovery of 90% pure allergen which, following final purification by size exclusion HPLC, showed a single line on immunodiffusion and crossed immunoelectrophoresis against monospecific anti-Fel d I and polyclonal anti-cat dander antibodies. The m.w. of native Fel d I was 39,000 on size exclusion HPLC, and 17,000 under nonreducing conditions on gel electrophoresis. The N-terminal amino acid sequence (33 residues) showed no homology with other known protein sequences. The combination of the SDS-PAGE and N-terminal sequence data suggests that Fel d I is a non-covalently linked homodimer. A two-site RIA was developed using mAb directed against different epitopes on Fel d I. This assay was species-specific, highly sensitive (0.0004 U/ml), and showed an excellent correlation with a polyclonal inhibition RIA (n = 27, r = 0.93, p less than 0.001). Cat allergen extracts used for immediate skin tests showed marked differences in Fel d I content (from 0.1 to 30 U/ml). Consistently high Fel d I levels were found at monthly intervals in six dust samples from four houses with cats (10 to 100 U/g of dust). Comparisons of Fel d I and mite and pollen allergen levels showed that house dust can contain greater than 100 micrograms/g of either of these allergens and is a potent source of foreign environmental antigens. Monoclonal affinity chromatography provides a major breakthrough in the purification of Fel d I, from a source material that would otherwise have been considered impossible (house dust). The mAb assay for Fel d I is both more sensitive and more easily standardized than existing techniques. These techniques will allow full structural and antigenic analysis of Fel d I and more detailed studies on the relationship between cat antigen exposure and the development of asthma.

Abstract: Background The National Survey of Lead and Allergens in Housing was the first population-based study to measure indoor allergen levels in US homes. Objective We characterized the overall burden to multiple allergens and examined whether increased allergen levels were associated with occupants' asthma status. Methods This cross-sectional study surveyed a nationally representative sample of 831 housing units in 75 different locations throughout the United States. Information was collected by means of questionnaire and environmental assessment. Allergen concentrations in dust samples were assessed by using immunoassays. The following cutoff points were used to define increased allergen levels: 10 μg/g for Der p 1, Der f 1, and Can f 1; 8 μg/g for Fel d 1; 8 U/g for Bla g 1; 1.6 μg/g for mouse urinary protein; and 7 μg/g for Alternaria alternata antigens. Allergen burden was considered high when 4 or more allergens exceeded increased levels in any of the sampling locations. Results Exposure to multiple allergens was common in US homes. Of the surveyed homes, 51.5% had at least 6 detectable allergens and 45.8% had at least 3 allergens exceeding increased levels. Race, income, housing type, absence of children, and presence of smokers, pets, cockroaches, rodents, and mold/moisture-related problems were independent predictors of high allergen burden. Among atopic subjects, high allergen burden increased the odds of having asthma symptoms (odds ratio, 1.81; 95% CI, 1.04-3.15). Conclusion Increased allergen levels in the home are associated with asthma symptoms in allergic individuals.