The examination of house dust mite extracts has indicated that over 30 different proteins can induce IgE antibody in patients allergic to the house dust mite. There are however dominant specificities especially the group 1 and 2 allergens which can account for much of the allergenicity of extracts. Of the 19 denominated allergens, the major IgE binding has been reported for the group 1, 2, 3, 9, 11, 14 and 15 allergens. The high-molecular-weight group 11, 14 and 15 allergens have only recently been described and although high IgE binding has been anticipated from immunoblotting, there is a need for considerable corroboration. Similarly, the study of the group 3 and 9 serine protease allergens has been incomplete. The group 4, 5, 7 and 8 allergens have shown intermediate IgE binding and the group 10 tropomyosins are of interest because of their potential cross-reactivity with allergen from disparate species. Although the progress with the production of recombinant group 1 allergens has been recent, many of the allergens can be produced as high IgE-binding polypeptides. The tertiary structure of the group 2 allergens has been determined from recombinant proteins and they are an excellent model for the investigation of modified allergens. An unexpected property of the group 1, 2 and 3 allergens has been the high degree of polymorphism found by cDNA analysis. It has however been possible to identify sequences to represent the variation in the natural allergens. The group 7 and 14 allergens show secondary modifications which vary in different extracts creating batch variation. While some estimate of the importance of allergens can be obtained from IgE binding, few analyses of T-cell responses have been made and these regulate both the development of, and the protection from sensitization.

Background: There is increasing evidence that the house dust mite Euroglyphus maynei may be a significant source of allergic sensitization. The structural information for the E. maynei allergens is largely restricted to a single partial genomic sequence of Eur m 1. Methods: A cDNA library was constructed from a culture of E. maynei. Clones encoding the major group 1 and 2 allergens were isolated by DNA hybridization and sequenced. Results: The sequence of several full length clones of Eur m 1 and Eur m 2 were obtained. The full pre–proenzyme sequence of the cysteine protease Eur m 1 was determined. The translated amino acid sequence of Eur m 1 and Eur m 2 had 84–86% sequence identity with the corresponding allergens from Dermatophagoides pteronyssinus and Dermatophagoides farinae mites. This is the same as the degree of sequence identity found between D. pteronyssinus and D. farinae despite Euroglyphus being a member of the Pyroglyphinae subfamily rather than the Dermatophagoidinae subfamily. Conclusion: The sequences of the major Eur m 1 and Eur m 2 allergens are described. Their degree of divergence from the Dermatophagoides spp. is similar to that observed between D. pteronyssinus and D. farinae group 1 and group 2 allergens.

Background: The major peanut allergen Ara h 2 consists of two isoforms, namely Ara h 2.0101 and Ara h 2.0201. The recently identified Ara h 2.0201 isoform contains an extra 12 amino acids including an extra copy of the reported immunodominant epitope DPYSPS. This study aimed to evaluate the IgE binding of the two Ara h 2 isoforms. Methods: Ten clones of Ara h 2 were sequenced to assess the relative frequency of the Ara h 2 isoforms and to identify whether there was further variation in the Ara h 2 sequence. IgE binding to Ara h 2.0101 and Ara h 2.0201 was measured for 70 peanut-allergic children using an IgE DELFIA^TM assay to quantitate specific IgE binding. A competition assay was used to measure whether Ara h 2.0201 contained IgE epitopes other than those found for Ara h 2.0101. Results: The original Ara h 2.0101 sequence was found for 6/10 clones and Ara h 2.0201 was found for 2/10 clones. Ara h 2.0201 had the expected insertion of 12 amino acids as well as substitutions at positions 40 (40G) and 142 (142E). Two new isoforms were identified as different polymorphisms of position 142. One Ara h 2.01 clone (Ara h 2.0102) contained 142E and one Ara h 2.02 clone (Ara h 2.0202) contained 142D. A polymorphism that was previously identified by other investigators at position 77 (77Q or 77R) was not found for any of the 10 sequences. Although the level of IgE binding to Ara h 2.0201 of individual patients was frequently higher than the binding to Ara h 2.0101 (p < 0.01), there was a strong correlation in binding to both isoforms (r = 0.987, p < 0.0001) and when analyzed as a group the means were similar. Ara h 2.0101 was not as efficient at blocking reactivity to Ara h 2.0201 indicating there is an additional IgE specificity for the Ara h 2.0201 isoform. Conclusions: Ara h 2.0201 has similar but higher IgE binding than the originally sequenced Ara h 2.0101 isoform and contains other IgE specificities.

Background: Of the ten recognised groups of Dermatophagoides pteronyssinus allergens, the group 4 is the only group that has not been characterised at the molecular level. Methods: Primers were designed to PCR amplify Der p 4 (D. pteronyssinus) and Eur m 4 (Euroglyphus maynei) cDNA. These fragments were used to screen the corresponding cDNA libraries and the cDNA clones obtained were subsequently sequenced. The coding regions of Der p 4 and Eur m 4 were cloned into the pET expression vector and recombinant histidine–tagged proteins expressed in Escherichia coli. Results: cDNA clones which included the mature protein coding sequence for Der p 4 and Eur m 4 were sequenced. The Der p 4 and Eur m 4 genes were found to code for 496 amino acid mature proteins with residues important for the function of α–amylase highly conserved. Der p 4 and Eur m 4 were calculated to be 90% identical and a BLAST search of the GenBank database found these sequences to be approximately 50% identical to insect and mammalian α–amylases. The calculated molecular weights of Der p 4 and Eur m 4 were approximately 57,000, although recombinant Der p 4 and Eur m 4 migrate on SDS–PAGE at about 60,000. Der p 4 recombinant protein was found to bind specific IgE in 3 of the 10 house dust mite allergic patients tested. Conclusions: This paper describes the first cDNA sequence of Der p 4 and Eur m 4 confirming that this allergen is house dust mite α–amylase.