Background: Human CD4+ T cell responses to important animal allergens are still insufficiently understood.
Objective: To comprehensively characterize in vitro and ex vivo the peripheral blood memory CD4+ T cell responses of subjects with and without allergy to the major dog allergen Can f 5, the only known animal allergen in the kallikrein family of proteins.
Methods: Can f 5-specific memory CD4+ T cell lines (TCLs) were established from the peripheral blood of 12 subjects with and 12 subjects without allergy to Can f 5 and characterized for their functional and phenotypic properties. The results were evaluated with those obtained ex vivo with a novel CD154 enrichment method. The epitopes recognized by the Can f 5-specific TCLs were determined with 72 overlapping 16-mer peptides covering the sequence of the allergen.
Results: Can f 5-specific TCLs were obtained at about tenfold higher frequency from allergic than from non-allergic subjects. Functionally, the TCLs of allergic subjects displayed a Th2-biased cytokine phenotype and increased T cell receptor avidity, whereas the TCLs of non-allergic subjects displayed a Th1-/Th0-biased cytokine phenotype and lower TCR avidity. The higher frequency and the Th2 phenotype of Can f 5-specific memory CD4+ T cells in allergic subjects were confirmed by the CD154 enrichment method ex vivo. Six distinct T cell epitope regions of Can f 5 were predominantly recognized by the TCLs from allergic subjects.
Conclusions and clinical relevance: Can f 5-specific memory CD4+ T cell responses differ considerably between subjects with and without allergy, as assessed by both in vitro and ex vivo approaches. Peptides containing the dominant T cell epitopes of Can f 5 can be employed for developing peptide-based immunotherapy for dog allergy.
Keywords: Can f 5; Memory T cells; T cell epitope, allergy; Th1/Th2; immunotherapy; peptide.
© 2015 John Wiley & Sons Ltd.