In vitro and in vivo allergenicity of recombinant Bet v 1 compared to the reactivity of natural birch pollen extract.

Abstract

Diagnostic procedures using natural extracts show only limited quantitative correlation between in vivo and in vitro results. Highly pure recombinant allergens might show more predictive findings. The aim of this study was to compare natural birch pollen extract (BPE) and recombinant Betula verrucosa (rBet v 1) for their diagnostic value comparing skin prick tests (SPTS) and nasal provocation tests (NPTS) with specific IgE in the serum. Thirty-four patients allergic to birch pollen and five healthy controls were investigated. SPT and NPT were performed with BPE and rBet v 1 at different concentrations. Specific serum IgE was measured by the Pharmacia CAP system. Commercial BPE and rBet v 1 (10 micro g/mL) were able to elicit similar allergenic reactions in vivo and IgE binding in vitro. SPT reflects immediate-type allergy as determined by NPT to a higher degree than specific IgE, for both reagents. To cause allergic reactions in NPT, higher amounts of rBet v 1 were needed than for skin tests and the sensitivity was lower than with BPE. rBet v 1 alone is sufficient for a reliable diagnosis of birch pollen allergy in most patients and induces comparable skin test reactivity as BPE, but less allergic reactions in nasal provocations.