Asmanet ENFUMOSA : F. de Blay Clinical relevance of cat bronchial challenge test

Congress

Sponsors

Write

About
màj 23/07/98

ENFUMOSA
(courriel: Chanez (at) montp.inserm.fr )
The European Network For Understanding
Mechanisms of Severe Asthma
BIOMED 2 Program - European Commission

4th quaterly meeting, with the support of INSERM and
Merck Sharp & Dhome Laboratory
February 13-14th 1998 in Montpellier- France
(see programm, abstracts and experts comments )

Titre ?
F. de Blay, M.C.Kopfer-Schmitt, P.Krieger,
F. Spirlet, A.Purohit, N.Frossard , G. Pauli

Vendredi 13 Février 1988		Présentateurs/Speakers		Modérateurs	Experts
11h30-12h30	Pollution domestique et atmosphérique Indoor and atmospheric pollution	F. de Blay (Strasbourg) M. Aubier (Paris) Discussion	15' 15' 30'	D. Charpin (Marseille) G. Pauli (Strasbourg)	J. Anto (Barcelone, E) N. Papageorgiou (Athenes, G)

To assess the clinical relevance of cat bronchial challenge tests (BCT), we have compared airborne Fel d 1 levels inducing respiratory symptoms at home to Fel d 1 levels inducing a positive BCT to cat. Among 18 cat-allergic patients (clinical history, a positive prick-test; specific IgE class II, positive BCT) only 11 were able to specify the exposure time at home needed to develop respiratory symptoms to cat. Airborne Fel d 1 measurements were performed in the 11 dwellings using a portable air sampler at 2 l/minute during 8 hours. During the sampling period, patients were free to move about and the cat(s) stayed indoors. The patients were asked on four occasions by four separate investigators the time necessary to develop respiratory symptoms (i.e. cough, breathlessness, wheezing). The BCT was considered positive when a 20% drop in FEV1 was obtained. Fel d 1 measurements were performed using a two-site monoclonal based assay. The Fel d 1 cumulative doses inducing a positive BCT ranged from 37.5 to 1900 ng (median: 956 ng). The duration necessary to develop respiratory symptoms varied from 20 to 440 minutes (median: 90 min). The median value of Fel d 1 capable of inducing respiratory symptoms at home was 5.4 ng (range 0.7-118.8). These results suggest: Fel d 1 levels inducing a positive BCT were higher than those provoking respiratory symptoms at home (p<0.01).

In another study, we have demonstrated that serum ECP levels are a good marker of allergen exposure.

To assess the early events associated with the increase in bronchial hyperresponsiveness in asthmatics, we have developed a model of repeated inhalation of low doses of cat allergen which did not induce any asthma symptoms in cat allergic asthmatics and studied the change in BHR, as well as levels of ECP both in BAL and serum before and after exposure to cat allergen or saline. Twelve mild asthmatic patients sensitized to cat, who were not exposed to cat allergen at home, have been submitted to a series of inhalations of cat allergen or placebo for 8 week days. Seven patients repeatedly inhaled 1/5 of the allergen dose inducing positive response in the acute challenge. As controls, 5 patients were inhaled saline. A methacholine challenge was performed before and after the allergen and/or saline exposures, as well as a BAL and blood sampling for ECP measurements and eosinophil counts. Patients did not experience any asthma symptom both after allergen or saline inhalations. However, a significant increase in BHR to methacholine was noted after allergen inhalations (PC20= 126 µg methacholine) as compared with before (PC20=263 µg) (p<0.02). Inhalation of saline did not induce any significant change in PC20 (108 and 124 µg methacholine before and after saline, respectively, NS). In parallel, ECP levels in BAL significantly increased after exposure to allergen from 0.8 to 3.1 µg/ml (p<0.05). No change was observed after saline inhalations. In serum, ECP levels also increased significantly after allergen inhalations from 15.9 to 31 µg/ml (p<0.05), whereas no change was observed after saline. The number of eosinophils in BAL and serum did not change, as well as BAL and serum IL-5 and RANTES. In conclusion, our results show that

Ref (1): de BLAY F., KOPFERSCHMITT M.C., GRIES P., FREY F., LINDER J., MAHR L., VEROT A., PAULI G. Comparison between Fel d 1 levels provoking respiratory symptoms at home and during bronchial challenge tests. J.Allergy Clin. Immunol., 1995, 95, 262 abst. (partial abstract from http://www.healthy.net/library/search/medline.htm )

Ref (2): de BLAY F., PUROHIT A., STENGER R., GRIES P., HAMBERGER C.; DAVID B., FROSSARD N., PAULI G. Serum ECP (eosinophil cationic protein) measurements in the management of perennial and periodic asthma a prospective study. Eur. Respir. J., 1998, in press (partial abstract from http://www.healthy.net/library/search/medline.htm )

Ref (3): de BLAY F., KRIEGER P., SPIRLET F., MOREAU L., DUVERNELLE C., KASSEL O., KOPFERSCHMITT M.C., GASSER B., DEMANGEAT C., PAULI G., FROSSARD N. Repeated inhalations of low doses of cat allergen not inducing clinical symptoms provoke an increase in bronchial hyperresponsiveness and in ECP levels. (submitted) Pavillon Laennec, Hôpitaux Universitaires de Strasbourg, INSERM U 425, Strasbourg (partial abstract from http://www.healthy.net/library/search/medline.htm )