Subtropical grass pollen allergens are important for allergic respiratory diseases in subtropical regions

Davies et al. Clinical and Translational Allergy 2012, 2:4 http://www.ctajournal.com/content/2/1/4 RESEARCH Open Access Subtropical grass pollen allergens are important for allergic respiratory diseases in subtropical regions Janet Mary Davies1*, Hongzhuo Li1, Melissa Green1,2, Michelle Towers1,2 and John Warrick Upham1,2 Abstract Background: Grass pollen allergens are a major cause of allergic respiratory disease but traditionally prescribing practice for grass pollen allergen-specific immunotherapy has favoured pollen extracts of temperate grasses. Here we aim to compare allergy to subtropical and temperate grass pollens in patients with allergic rhinitis from a subtropical region of Australia. Methods: Sensitization to pollen extracts of the subtropical Bahia grass (Paspalum notatum), Johnson grass (Sorghum halepense) and Bermuda grass (Cynodon dactylon) as well as the temperate Ryegrass (Lolium perenne) were measured by skin prick in 233 subjects from Brisbane. Grass pollen-specific IgE reactivity was tested by ELISA and cross-inhibition ELISA. Results: Patients with grass pollen allergy from a subtropical region showed higher skin prick diameters with subtropical Bahia grass and Bermuda grass pollens than with Johnson grass and Ryegrass pollens. IgE reactivity was higher with pollen of Bahia grass than Bermuda grass, Johnson grass and Ryegrass. Patients showed asymmetric cross-inhibition of IgE reactivity with subtropical grass pollens that was not blocked by temperate grass pollen allergens indicating the presence of species-specific IgE binding sites of subtropical grass pollen allergens that are not represented in temperate grass pollens. Conclusions: Subtropical grass pollens are more important allergen sources than temperate grass pollens for patients from a subtropical region. Targeting allergen-specific immunotherapy to subtropical grass pollen allergens in patients with allergic rhinitis in subtropical regions could improve treatment efficacy thereby reducing the burden of allergic rhinitis and asthma. Keywords: Grass pollen, Allergic rhinitis, IgE, Bahia grass pollen, Bermuda grass pollen, Ryegrass pollen Background Grass pollens are amongst the most frequently recognised aeroallergens worldwide [1,2]. Allergic rhinitis is an important health problem causing itching, fatigue, decrease in quality of life, reduced productivity and complications such as sleep apnoea and sinusitis [3]. Allergic rhinitis poses a significant ongoing health burden per se but it carries additional adverse consequences such as increasing the risk of developing asthma and * Correspondence: 1 Lung and Allergy Research Centre, School of Medicine, The University of Queensland, Princess Alexandra Hospital Clinical Division, Woolloongabba, QLD 4076, Australia Full list of author information is available at the end of the article being associated with poor asthma control [4]. Recent studies have established an association between hospital admissions for asthma and airborne grass pollen allergen levels [5] as well as a causal relationship between grass pollen challenge and asthma exacerbation [6]. Furthermore, epidemics of thunderstorm-induced asthma due to grass pollen allergy have been well documented in Australia and elsewhere [7-11]. The most recent epidemic that occurred in November 2010 in Melbourne Australia, followed days with extremely high grass pollen counts and affected people without a previous history of asthma [7]. Despite the clinical importance of grass pollen allergy in allergic respiratory diseases, it has not been established © 2012 Davies et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Davies et al. Clinical and Translational Allergy 2012, 2:4 http://www.ctajournal.com/content/2/1/4 which of the grass pollens are most relevant to Australian environments, with the exception of Ryegrass (Lolium perenne) which is the major clinically relevant allergenic grass pollen in temperate regions of Australia [12,13]. The subtropical climate throughout parts of Queensland supports a wider range of grasses than some other regions with predominance of many species of subtropical grasses from several botanical subfamilies of Poaceae grasses (Figure 1). Environmental surveys on grass distribution in Queensland in the 1960s indicated that Bahia grass (Paspalum notatum), Johnson grass (Sorghum halepense) and Bermuda grass (Cynodon dactylon) were among the most abundantly observed grasses [14], although Ryegrass is also observed in south east Queensland[15]. Aerobiological pollen sampling conducted in Brisbane in 1990s showed that grass pollens contribute the major part (65%) of airborne pollen load [16]. The environmental distribution of subtropical grasses is likely to spread with climatic increases in temperature and carbon dioxide levels, escalating the importance of their contribution to allergic respiratory diseases in future [17]. However, there is very little clinical data on allergic sensitization to grass pollens in patients with allergic rhinitis in subtropical regions. Such information is likely to be valuable for optimal use of allergen specific immunotherapy in Australia as well as other warmer regions of the world, including the southern states of America where these types of subtropical grasses are also important allergen sources [18,19]. Chloridoideae Panicoidae Paspalum notatum (Bahia) Panicoideae Zea mays (maize) Andropogonodae Sorghum halepense (Johnson) Poodae Lolium perenne (Ryegrass) Pooideae Here we examine allergic sensitization by skin prick testing and assess IgE reactivity in subjects from Brisbane to a panel of subtropical grass pollens from separate botanical subfamilies; Bahia, Johnson and Bermuda grasses, in comparison with pollen of the temperate Ryegrass. The relative strength of IgE reactivity with the different grass pollen allergens and presence of species-specific IgE reactivity with subtropical grass pollen allergens are examined. Methods Study participants Two hundred and thirty three participants were recruited consecutively from amongst laboratory and healthcare workers or patients who were living in the Brisbane region presenting to an Immunology or Respiratory clinic at the Princess Alexandra Hospital. Written informed consent was obtained from each participant; the study was approved by the Metro South Human Research Ethics Committee. Symptoms of allergies and asthma were recorded and participants were assessed for allergic sensitivity by skin prick testing and ELISA with a panel of common aeroallergens including pollen extracts of Bahia grass, Johnson grass, Bermuda grass or Ryegrass. Subjects were assigned to the grass pollen allergic group based on clinical histor (...truncated)