Cross-reactivity in Grasses: Biochemical Attributes Define Exemplar Relevance

Abstract

IntroductionBroad-spectrum grass pollen immunotherapies contain large numbers of allergenic proteins from multiple species. The principle of homologous grouping is used as a tool to assist in the standardization of allergen immunotherapy. This study reviews the principle of homologous grouping, questions what an exemplar grass should be, and queries whether a 1-way system of inferring homology is appropriate.MethodsGrass pollens were extracted and analyzed using a variety of techniques, including enzyme-linked immunosorbent assay, Bradford protein assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and quantitative analysis of Western blots.ResultsVariation in protein content, IgG, IgE, and Phl p 5 reactivity is evident among all grasses analyzed. There is significant evidence of similarity but also disparity consistent with variation resulting from evolutionary change. Proprietary software called Gel Electrophoresis Protein Profile Analysis has been developed, which highlights that each grass exhibits a greater than 55% similarity measure; this is considered high similarity.DiscussionNone of the grass species examined display an identical biological profile. However, data indicate that there is a high degree of homology, and Crested Dogstail is similar to each of the other 12 species analyzed; these levels of similarity can only be possible because of molecular profile and extensive sharing of epitopes. These data are considered to be sufficient to include Crested Dogstail within the sweet grasses group of the Pooideae family; however, the subtle differences in grasses also justify the inclusion of multiple species to create a broad-spectrum immunotherapy.

The grass pollen season 2014 in Vienna: A pilot study combining phenology, aerobiology and symptom data

“…Since a long time scientists and pharmaceutical companies argue whether it is beneficial for patients to use a single "exemplar" grass or a multiple "broad-spectrum" grass mix for successful immunotherapy (Kleine-Tebbe, 2008). According to the literature, both approaches show conformable results (Moingeon et al, 2008;Martínez-Cócera et al, 2010;Bullimore et al, 2012;Aleksic et al, 2014). However, bearing in mind the variety of grass species that contribute to the grass pollen season, including minor allergens and the differing amounts of major allergens, a multiple "broad-spectrum" grass approach will undoubtedly mimic and reflect a more natural exposure condition and therefore be more beneficial for grass pollen allergy sufferers.…”

“…There are also differences in allergen content of the ambient air (Phl p 5), grass pollen concentrations and symptom loads on a European scale (Bastl et al, 2016;Buters et al, 2015). Moreover, recent studies highlight the unique biochemical profiles for each different grass species (Bullimore et al, 2012) and varying amounts of major allergen content (Moingeon et al, 2008). Thus, in addition to the importance in cross-reactivity of major allergen groups, minor allergens and the contribution of unique IgE epitopes from different grass species themselves has the propensity to impact individual symptom severity in grass pollen allergy sufferers.…”

“…A major problem is the gap in knowledge that exists on the contribution of single grass species to allergic reactions and sensitization profiles of people concerned. Extensive cross-reactions among allergens of different grasses are known (Johansen et al, 2009) as well as the different allergenicity of single grass species (Bullimore et al, 2012). However, it remains unclear if and how those species are responsible for the allergenic burden under natural conditions.…”

Multiple independent IgE epitopes on the highly allergenic grass pollen allergen Phl p 5

“…Allergic subjects are not only likely to encounter different group 5 allergens from timothy but also to encounter such allergens from other grasses. Indeed, IgE antibodies from allergic patients are known to cross-react to allergens found in several different grasses 32 but the cross-reacting behaviour of human monoclonal IgE antibodies targeting the different epitopes of these allergens is not well established. Past studies of the Fab of clone 5 indicated that it reacted strongly not only to components of timothy grass ( Phleum pratense ) pollen but also to pollen extracts of other grasses 25 , 33 .…”

“…Pollen contains multiple isoallergens and isoforms of major allergens such as the group 5 allergens 28 and several grasses produce similar cross-reacting allergens 32 . Our results identify that monoclonal IgE with reactivity towards the Phl p 5.0101 isoallergen display broad cross-reactivity to group 5 allergens of a large variety of grass species.…”