Abstract
Lolium multiflorum (Lm) grass pollen is the major cause of pollinosis in Southern Brazil. The objectives of this study were to investigate immunodominant components of Lm pollen allergens and the cross-reactivity of IgE with commercial grass pollen allergen extracts. Thirty-eight serum samples from patients with seasonal allergic rhinitis (SAR), 35 serum samples from patients with perennial allergic rhinitis (PAR) and 30 serum samples from non-atopic subjects were analyzed. Allergen sensitization was evaluated using skin prick test and serum IgE levels against Lm pollen extract were determined by ELISA. Inhibition ELISA and immunoblot were used to evaluate the cross-reactivity of IgE between allergens from Lm and commercial grass pollen extracts, including L. perenne (Lp), grass mix I (GI) and II (GII) extracts. IgE antibodies against Lm were detected in 100% of SAR patients and 8.6% of PAR patients. Inhibition ELISA demonstrated IgE cross-reactivity between homologous (Lm) and heterologous (Lp or GII) grass pollen extracts, but not for the GI extract. Fifteen IgE-binding Lm components were detected and immunoblot bands of 26, 28-30, and 32-35 kDa showed >90% recognition. Lm, Lp and GII extracts significantly inhibited IgE binding to the most immunodominant Lm components, particularly the 55 kDa band. The 26 kDa and 90-114 kDa bands presented the lowest amount of heterologous inhibition. We demonstrated that Lm extract contains both Lm-specific and cross-reactive IgE-binding components and therefore it is suitable for measuring quantitative IgE levels for diagnostic and therapeutic purposes in patients with pollinosis sensitized to Lm grass pollen rather than other phylogenetically related grass pollen extracts.
Highlights
Grass pollen allergy is a common cause of morbidity in genetically predisposed subjects
We demonstrated in that study that Lolium multiflorum (Lm)-specific IgE antibodies are highly cross-reactive with pollen allergens from other grass species, but Lm-specific or cross-reactive IgE-binding components have not been identified
We confirmed our previous results concerning the use of the Lm extract in skin prick test (SPT) and ELISA for the detection of IgE responses in an independent group of patients with pollinosis
Summary
Grass pollen allergy is a common cause of morbidity in genetically predisposed subjects. An increasing number of grass pollen species have been recognized as important allergen sources [1,2,3]. Among the different types of allergenic grass pollen species, Poaceae family plants such as Lolium perenne, Poa pratensis and Phleum pratense are the major sources of grass pollen allergens due to their broad distribution in certain geographic areas and high capacity of pollen production [4,5]. Lolium multiflorum (Italian ryegrass) is the most important Poaceae grass related to pollinosis in the South region of Brazil [6], other grasses of the same family, such as Paspalum notatum (Bahia grass), Anthoxanthum odoratum (sweet vernal grass), Cynodon dactylon (Bermuda grass), and Holcus lanatus (velvet grass), grow naturally as weeds in Southern Brazil, but they are not clinically relevant [7,8].
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