How far can we simplify in vitro diagnostics for grass pollen allergy?: A study with 17 whole pollen extracts and purified natural and recombinant major allergens

Background: Current diagnostics for grass pollen allergy are composed of mixtures of pollen of different grass species. Their complex composition hampers accurate standardization. Objective: The aim of the study was to investigate whether mixtures of grass pollen extracts can be replaced by a single pollen species and whether a single pollen species can be replaced by a limited number of purified natural or recombinant major allergens. Methods: Sera ( n = 800) were selected on the basis of a general suspicion for inhalant allergy and tested in a RAST for IgE reactivity with pollen from 17 different grass species. Cross-reactivity of IgE responses was studied by means of RAST inhibition. Sera with positive test results for grass pollen were tested in a RAST for natural Lol p 1 and Lol p 5 and recombinant Phl p 1 and Phl p 5. Results: Specific IgE antibodies against one or more of the 17 pollen species were detected in 209 of 800 sera (26.1%). The highest responses were observed against Poa pratensis followed by Festuca rubra, Phleum pratense, and Dactylis glomerata. IgE responses were clearly lower (approximately by a factor of 5) against only three species ( Phragmites communis, Cynodon dactylon, and Zea mays). With the exception of a few low-responder sera, no sera were found to have negative test results to the high responder species and positive results to any of the other species. Sera with positive test results for grass pollen ( n = 154) were tested with purified Lol p 1 and Lol p 5. IgE anti-Lol p 1 and Lol p 5 accounted for an average of 81% ± 7% of total anti-grass pollen IgE. For 14 sera (all with low anti-grass pollen IgE titers), a RAST with purified allergens resulted in a false-negative diagnosis for grass pollen allergy. With recombinant Phl p 1 and Phl p 5, the mean IgE reactivity was 57% ± 6% of the anti-grass pollen IgE response ( n = 141), with 13 false-negative results. Conclusion: One grass species is sufficient for in vitro diagnosis of grass pollen allergy. With purified natural Lol p 1 and Lol p 5, greater than 90% of grass-positive sera is detected. Around 80% of the IgE response to grass pollen is directed to these major allergens. Recombinant allergens, produced in Escherichia coli, did not equal the IgE-binding capacity of their natural counterparts. (J Allergy Clin Immunol 1998;102:184-190.)