The Effect of Omalizumab on Responses to Cat Allergen Challenge

Omalizumab is a monoclonal antibody directed against Immunoglobulin E (IgE) and is FDA-approved for use in allergic asthma, though its clinical role is not precisely defined. It binds IgE on the same site of the Fc domain as the high affinity IgE receptor (FcεRI), and therefore, blocks the interaction between IgE and mast cells or basophils. It, therefore, may be used as a mechanistic tool in the study of IgE. As IgE levels are reduced with omalizumab, FcεRI expression on human basophils is reduced. This reduction of basophil receptors and allergen induced activation is pronounced within 7 days of the initial administration and is reversible once omalizumab administration is discontinued. The omalizumab-induced reductions in mast cell FcεRI expression and function is unchanged at day 7 and significantly reduced by day 70. These changes were based upon intravenously administered omalizumab at a dose of 0.03 mg/kg/IU IgE/mL in a total of three subjects. We propose to exploit the kinetics of faster omalizumab effects on circulating basophils relative to tissue mast cells to elucidate the role of the basophil versus mast cell activation in nasal airway allergen challenge, which has not been studied to date.