Kinetics of mast cell, basophil, and oral food challenge responses in omalizumab-treated adults with peanut allergy.
BACKGROUND
Monoclonal antibodies directed at IgE demonstrate clinical efficacy in subjects with peanut allergy, but previous studies have not addressed the kinetics of the clinical response or the role of mast cells and basophils in the food-induced allergic response.


OBJECTIVE
We sought to determine the kinetics of the clinical response to omalizumab and whether clinical improvement is associated with either mast cell or basophil suppression.


METHODS
Subjects with peanut allergy were treated with omalizumab for 6 months and assessed for clinical and cellular responses. At baseline, subjects had a double-blind, placebo-controlled oral food challenge (OFC), skin prick test titration (SPTT), and basophil histamine release (BHR) to peanut. BHR was repeated at week 2 and then weekly until it decreased to less than 20% of baseline values. The OFCs and SPTTs were repeated after the BHR reduction (or at week 8 if BHR did not decrease) and again at 6 months.


RESULTS
Fourteen subjects enrolled in the study. At the second food challenge, there was a significant increase in the threshold dose of peanut inducing allergic symptoms (80 to 6500 mg, P < .01). Peanut-induced BHR was either completely suppressed (n = 5) or 10-fold more allergen was required to induce maximal BHR (n = 9), and SPTT responses were not significantly changed from baseline. After 6 months of omalizumab, further changes in the OFC threshold dose or BHR were not observed, but a significant suppression in SPTTs was identified.


CONCLUSIONS
The clinical response to omalizumab occurs early in treatment when the basophil, but not the mast cell, is suppressed, supporting a role for the basophil in acute food reactions.
Division of Allergy and Clinical Immunology, Johns Hopkins University, Baltimore, MD, USA.
Jessica H
JH
Savage
Jean-Paul
JP
Courneya
Patricia M
PM
Sterba
Donald W
DW
Macglashan
Sarbjit S
SS
Saini
Robert A
RA
Wood
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D018926:Anti-Allergic Agents / Q000008:administration & dosage* / Q000009:adverse effects; D000888:Antibodies, Anti-Idiotypic / Q000008:administration & dosage* / Q000009:adverse effects; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage* / Q000009:adverse effects; D001491:Basophils / Q000187:drug effects* / Q000276:immunology; D006632:Histamine / Q000378:metabolism; D006801:Humans; D007114:Immunization; D007165:Immunosuppression Therapy; D008407:Mast Cells / Q000187:drug effects* / Q000276:immunology; D008875:Middle Aged; D000069444:Omalizumab; D021183:Peanut Hypersensitivity / Q000188:drug therapy* / Q000276:immunology; D012882:Skin Tests; D055815:Young Adult
D018926:Anti-Allergic Agents; D000888:Antibodies, Anti-Idiotypic; D061067:Antibodies, Monoclonal, Humanized; D000069444:Omalizumab; D006632:Histamine