Dose dependence and time course of the immunologic response to administration of standardized cat allergen extract.
BACKGROUND
The immunologic response to allergen immunotherapy with 3 serial 5-fold doses of cat extract has been studied after approximately 5 weeks of immunotherapy. The highest dose containing 15 mug of Fel d 1 produced the most consistent and favorable response. It is unknown whether the comparative response on reaching a maintenance dose is maintained with long-term maintenance therapy.


OBJECTIVE
The purpose of this investigation was to evaluate the immunologic responses with these 3 serial doses of cat hair and dander extract at baseline, after reaching the maintenance dose (approximately 5 weeks), and after 1 year of maintenance immunotherapy.


METHODS
Twenty-eight patients with cat allergy randomized in a double-blind study were assigned to one of 4 treatment groups: placebo or cat hair and dander extract containing 0.6 mug of Fel d 1, 3 mug of Fel d 1, and 15 mug of Fel d 1 at maintenance. Studies included skin prick tests and late cutaneous reactions with cat hair and dander extract, titrated nasal challenges with the extract, serum cat allergen-specific IgG4 and IgE measurement, and flow cytometric and ELISA analysis of whole blood and intranasal cytokines (TGF-beta, IL-10, IFN-gamma, IL-4, and IL-5).


RESULTS
Twenty-six subjects completed the study. After both 5 weeks and 1 year, significant and dose-dependent differences were seen with total symptom scores on nasal challenge ( P < .0001), with titrated skin prick testing with cat dander extract at 5 weeks ( P = .014) and 1 year ( P < .0001), and with cat-specific IgG4 measurement at 5 weeks ( P = .004) and 1 year ( P = .003). At 1 year, neither flow cytometry of whole blood nor ELISA evaluation of nasal cytokines demonstrated any significant differences among the treatment groups.


CONCLUSIONS
The response to titrated nasal allergen challenge, titrated skin prick testing, and allergen-specific IgG4 measurement to cat immunotherapy at 5 weeks is predictive of the response at 1 year.
Nanda
Anil
A
Department of Medicine, National Jewish Medical Center, University of Colorado, Denver, CO 80206, USA.
O'connor
Maeve
M
Anand
Miriam
M
Dreskin
Stephen C
SC
Zhang
Lening
L
Hines
Brittany
B
Lane
Diana
D
Wheat
William
W
Routes
John M
JM
Sawyer
Richard
R
Rosenwasser
Lanny J
LJ
Nelson
Harold S
HS
D000485:Allergens / Q000276:immunology*; D000818:Animals; D002415:Cats / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D004311:Double-Blind Method; D005434:Flow Cytometry; D006023:Glycoproteins / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D015375:Receptors, Interleukin-2 / Q000032:analysis; D012882:Skin Tests; D016212:Transforming Growth Factor beta / Q000097:blood
D000485:Allergens; D006023:Glycoproteins; D007074:Immunoglobulin G; D015375:Receptors, Interleukin-2; D016212:Transforming Growth Factor beta; C059296:Fel d 1 protein, Felis domesticus