The upper and lower airway responses to nasal challenge with house-dust mite Blomia tropicalis.
BACKGROUND
The house dust mite Blomia tropicalis (B. tropicalis) was found to be the most prevalent domestic mite in Singapore. However, its pathogenicity in allergic airway diseases remains to be investigated.


METHODS
Twenty adults with persistent allergic rhinitis (PAR) were studied. Five had a history of asthma, and all were asymptomatic except one who was under treatment with low-dose inhaled corticosteroid. Nasal challenge was carried out by nasal spray with phosphate-buffered saline (PBS) and with increasing concentrations of crude B. tropicalis extracts (0.6, 6.0 and 60 micro g/ml) at 15 min intervals. Subjective symptom scores and absolute number of sneezes were recorded together with objective measurements of spirometry (forced expiratory volume in 1 s, FEV1) and acoustic rhinomanometry (volume of the nasal cavity). These were performed at baseline, 5 min after each incremental challenge, and 30 min, 1 h, 3 h, 5 h and 7 h after the last challenge. Meanwhile, concentrations of mediators in nasal secretions (tryptase, leukotriene C4 (LTC4) and eosinophil cationic protein (ECP)) were measured in nasal aspirate samples at similar time intervals. An identical (control) challenge procedure with PBS alone was repeated in seven patients after a washout period of at least 2 weeks.


RESULTS
Significant increases in the subjective and objective nasal symptoms, together with a significant increase of tryptase and LTC4 concentrations in nasal secretion, were found 5 min after each challenge with B. tropicalis, but not with PBS. There was no definitive pattern of the late-phase nasal response in either subjective symptoms or objective measurements. Three patients (3/5) with a history of asthma showed a fall in FEV1 readings (33%, 22% and 11% from baseline, respectively) at 7 h post challenge with concomitant mild wheezing in the night.


CONCLUSIONS
Our study demonstrates direct evidence of allergic nasal response to B. tropicalis in sensitized adults. It shows that nasal provocation may also provoke concomitant asthmatic symptoms during the late-phase reaction, especially in people with a history of asthma.
Wang
D Y
DY
Department of Otolaryngology, The National University of Singapore, Singapore.
Goh
D Y T
DY
Ho
A K L
AK
Chew
F T
FT
Yeoh
K H
KH
Lee
B W
BW
D000328:Adult; D000485:Allergens / Q000009:adverse effects* / Q000494:pharmacology*; D000818:Animals; D001798:Blood Proteins / Q000187:drug effects / Q000378:metabolism; D003429:Cross Reactions / Q000187:drug effects / Q000502:physiology; D004391:Dust / Q000276:immunology*; D047091:Eosinophil Granule Proteins; D004804:Eosinophils / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects / Q000502:physiology; D006801:Humans; D017997:Leukotriene C4 / Q000378:metabolism; D008297:Male; D008925:Mites / Q000276:immunology; D009297:Nasal Mucosa / Q000737:chemistry / Q000378:metabolism; D009299:Nasal Provocation Tests; D012221:Rhinitis, Allergic, Perennial / Q000209:etiology; D012260:Ribonucleases; D012697:Serine Endopeptidases / Q000187:drug effects / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors; D053802:Tryptases
D000485:Allergens; D001798:Blood Proteins; D004391:Dust; D047091:Eosinophil Granule Proteins; D017997:Leukotriene C4; D012965:Sodium Chloride; D012260:Ribonucleases; D012697:Serine Endopeptidases; D053802:Tryptases