Cat allergies are among the most common hypersensitivity reactions in people and a major cause of asthma. Allergies to cats predispose children to severe asthma. Treatment is primarily symptomatic. Allergen-specific immunotherapy is efficacious but it is also complicated by hypersensitivity reactions and can be cumbersome. The overall goal of this study was to determine the major T-cell epitopes of Fel d1 for immunotherapy, synthesize a Fel d1 peptide vaccine for a clinical study, and then test it for safety and tolerability. The present study was a randomized, double-blind, placebo-controlled clinical trial. Subjects had a history of rhino-conjunctivitis with or without asthma and had been exposed to cats for at least 1 year. Subjects received the vaccine or placebo either by intradermal injection (n = 40) or subcutaneously (SC) (n = 48). All participants received a single dose of each of 4 increasing amounts. There were no serious adverse events and none of the subjects withdrew because of adverse events. The most common complaints from participants in the intradermal vaccine group were nasopharyngitis, cough, and headache. In the SC-vaccine group, the most common complaints were nasal congestion and respiratory symptoms. Overall, the peptide vaccine was found to be safe and well tolerated at doses up to 12 nmol given intradermally and up to 20 nmol given SC. Concurrent immunologic studies suggest that a short course of fixed-dose peptide immunotherapy may have a comparable therapeutic effect to longer courses of treatment with conventional allergen. Now that the safety and tolerability have been established in this preliminary study, further work can be done to test the peptide vaccine in the clinical setting. Supported by Circassia Limited

Commentary: Probably everyone reading this commentary knows someone who suffers from cat allergies. Depending on the symptoms, management can range from antihistamine therapy to complete avoidance. For people with severe allergies and/or those who cannot avoid Fel d1 allergen, immunotherapy with protein vaccines has been the major alternative therapy. Current allergy therapy is time-consuming because the vaccines require administration in the doctor’s office. The peptide vaccine in this study must be very promising, as a Google search revealed that both European and U.S. patents have been filed and the vaccine even has a name, ToleroMune Cat. The mechanism is novel and studies have shown it is well tolerated in vivo and does not trigger histamine response by basophils in vitro.—Karen A. Moriello, DVM, Diplomate ACVD

Development and preliminary clinical evaluation of a peptide immunotherapy vaccine for cat allergy. Worm M, Lee H, Kleine-Tebbe J, et al. J ALLERGY CLIN IMMUNOL 127:89-97, 2011.