Analysis of antigenic peptides obtained from Japanese birch pollen

Allergic rhinitis caused by birch pollen is common in parts of Northern Europe, North America and the northern Japanese island of Hokkaido. The major antigenic fragment of European birch (Betula verrucosa) pollen allergen with a M. W. of 17k dalton was isolated and termed Bet vI. The amino acid sequence of Bet vI has already been identified. We have attempted to identify an antigenic peptide of Japanese birch (Betula platyphylla var. Japonica) pollen allergen. Seventeen Kd fragments separated from pollen allergen by SDS-PAGE were shown to bind with IgE in the pooled sera of pollinosis patients. The fragment was digested with trypsin and fractionated by reverse phase HPLC. Five fractions were identified to have in vitro activities, such as the lymphocyte proliferative response, in pollinosis patients. Amino acid sequences of peptides in the fractions were determined. The sequence of a 12-mer peptide was shown to correspond to that of No 22-33 of Bet vI, except for the amino acid at the 31st position, phenylalanine, which was instead isoleucine. Synthetic peptides based on this sequencing were shown to cause proliferation of lymphocytes, derived from pollinosis patients, which was blocked by monoclonal antibodies to HLA-DR molecules.