[Recombinant allergens: diagnostic use and therapeutic perspectives]

Techniques of genetic engineering applied to allergens have enabled the production of recombinant allergens. The validation of recombinant allergens implies that their immunological activity and their identity with natural allergens might be confirmed by in vitro and in vivo techniques carried out on a sufficiently large number of allergic subjects. Currently available results for the principal pneumoallergens are reported. Thus the work of validating recombinant allergen BeTv1 has been confirmed by in vitro tests and also by skin tests and nasal and bronchial provocation tests. The association of four recombinant allergens of phleole has enabled the detection in vitro of sensitisation to germinated pollens in 94.5% of patients. For mites the validity of group 2 recombinant allergens has been confirmed. A system enabling the expression of glycosylation of recombinant proteins was necessary to validate recombinant proteins in group 1 allergens. The recombinant allergen Blot5 is recognised as being effective in the detection of sensitization to Blomia tropicalis, a domestic allergen in sub tropical countries. The recombinant allergens Bla g 4 and Bla g 5 have been tested in vitro and in vivo and reactions were positive in nearly 50% of subjects sensitive to cockroaches. The recombinant Asp f 1 has been tested in subjects suffering from allergic bronchopulmonary aspergillosis and is positive in 60-85% of cases. Some studies are available for recombinant allergens of certain animal antigens (Equ c 1, Bos d 2). The consequences of clarifying recombinant allergens are then analysed: obtaining better standardised allergens for diagnostic tests, studying the spectrum of specificities of IgE induced by an allergen, the quantification of specific IgE, a better approach to mixed allergies with the help of recombinant allergens of the principal mixed allergens. Some recent progress has led to the production of modified recombinant allergens: the synthesis of recombinant polypeptides corresponding to T epitopes, the production of isoform recombinant allergens with reduced allergenic activity, the production of recombinant allergens of modified allergenic molecules by directed mutations and the production of recombinant fragments of allergenic molecules. The use of modified recombinant allergens is a way of permitting research which would, in the future, lead to new modalities of specific immunotherapy.