Identification of T-cell epitope sequences on an important mite antigen

Summary Background T‐cell epitopes on Der 1 and Der 2 groups, the major mite allergens, have been intensively analysed, while those on the other important allergens remain to be elucidated. We have cloned four cDNAs coding for important mite allergens on the basis of frequency and capacity of IgE binding. Stimulatory action of glutathione S‐transferase‐fused Mag1 on lymphocytes from mite‐allergic patients was relatively high among them. Objective To identify T‐cell epitopes on Mag1, we studied the stimulating activity of truncated Mag1 proteins and synthetic peptides on proliferative response of lymphocytes from mite antigen‐immunized mice and mite‐sensitive patients. Methods Truncated Mag1 proteins were expressed as a fusion protein with β‐galactosidase in Escherichia coli pop2136 carrying a variety of deleted Mag1 inserts. Murine T‐cell epitope regions were estimated by the truncated antigen‐induced lymphocyte proliferation assay. Overlapping peptides covering the whole sequence of the presumed T‐cell epitope regions were synthesized to identify the epitope core. sequences using murine and human Mag1‐specific T‐cell lines. Results Amino acid range 56–70 on Mag1 molecule showed remarkable stimulatory action on murine T cells, while amino acid ranges 51–65 and 86–100 had potent stimulatory activity on human T cells. Conclusion These results suggest that Mag1 is a valuable antigen suitable for studies on T‐cell responses and T‐cell epitopes in mice and humans.