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Atmospheric modelling of grass pollen rupturing mechanisms for thunderstorm asthma prediction.

ABSTRACT: The world's most severe thunderstorm asthma event occurred in Melbourne, Australia on 21 November 2016, coinciding with the peak of the grass pollen season. The aetiological role of thunderstorms in these events is thought to cause pollen to rupture in high humidity conditions, releasing large numbers of sub-pollen particles (SPPs) with sizes very easily inhaled deep into the lungs. The humidity hypothesis was implemented into a three-dimensional atmospheric model and driven by inputs from three meteorological models. However, the mechanism could not explain how the Melbourne event occurred as relative humidity was very low throughout the atmosphere, and most available grass pollen remained within 40 m of the surface. Our tests showed humidity induced rupturing occurred frequently at other times and would likely lead to recurrent false alarms if used in a predictive capacity. We used the model to investigate a range of other possible pollen rupturing mechanisms which could have produced high concentrations of SPPs in the atmosphere during the storm. The mechanisms studied involve mechanical friction from wind gusts, electrical build up and discharge incurred during conditions of low relative humidity, and lightning strikes. Our results suggest that these mechanisms likely operated in tandem with one another, but the lightning method was the only mechanism to generate a pattern in SPPs following the path of the storm. If humidity induced rupturing cannot explain the 2016 Melbourne event, then new targeted laboratory studies of alternative pollen rupture mechanisms would be of considerable value to help constrain the parameterisation of the pollen rupturing process.

SUBMITTER: Emmerson KM

PROVIDER: S-EPMC8046208 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe world's most catastrophic epidemic thunderstorm asthma event (ETSA) affected Melbourne in 2016. Little is known about the natural history of individuals affected by such extreme events.ObjectiveIn this single center prospective 3-year longitudinal study, symptomatology and behaviors of individuals affected by ETSA were assessed.MethodsStandardized telephone questionnaire was used to evaluate frequency of asthma symptoms, inhaled corticosteroid preventer use, asthma action plan ownership, and healthcare utilization. Questionnaires were administered at 12, 24, and 36 months after 2016 ETSA. Subgroup analyses of the 'current', 'past', 'possible,' and 'no asthma' subgroups were also conducted.ResultsTwo hundred and eight, 164, and 112 completed questionnaires were analyzed in 2017, 2018, and 2019, respectively. Seventy to eighty five percent of respondents reported ongoing asthma symptoms in any given year, of which 20%-28% experienced weekly symptoms. Nearly 50% of respondents were prescribed preventers, with approximately 45% adherent at least 5 days a week. Less than 40% had an asthma action plan and 15%-20% sought urgent medical attention for asthma over the follow-up period. Among 106 individuals with 3 consecutive years of completed questionnaires, those with no prior doctor diagnosis of asthma were significantly more likely to be asymptomatic on follow-up than those with a prior doctor diagnosis of asthma (p = 0.02). Subgroup analyses suggest that large proportions of respondents with 'past' and 'no asthma' continue to remain symptomatic throughout the 36-month period.ConclusionIn individuals affected by ETSA, we found evidence of ongoing loss of asthma control in those with previously well controlled asthma, and the persistence of symptoms suggestive of asthma in those with no history or symptoms suggestive of prior asthma, even after 36 months from initial ETSA. Low rates of inhaler adherence and asthma action plan ownership may contribute to increased morbidity and mortality from future ETSA events. Further research is required to confirm these findings.

Project description:Grass pollen is one of the leading causes of pollinosis, affecting 10-30% of the world's population. The allergenicity of pollen from different Poaceae species is not the same and is estimated from moderate to high. Aerobiological monitoring is a standard method that allows one to track and predict the dynamics of allergen concentration in the air. Poaceae is a stenopalynous family, and thus grass pollen can usually be identified only at the family level with optical microscopy. Molecular methods, in particular the DNA barcoding technique, can be used to conduct a more accurate analysis of aerobiological samples containing the DNA of various plant species. This study aimed to test the possibility of using the ITS1 and ITS2 nuclear loci for determining the presence of grass pollen from air samples via metabarcoding and to compare the analysis results with the results of phenological observations. Based on the high-throughput sequencing data, we analyzed the changes in the composition of aerobiological samples taken in the Moscow and Ryazan regions for three years during the period of active flowering of grasses. Ten genera of the Poaceae family were detected in airborne pollen samples. The representation for most of them for ITS1 and ITS2 barcodes was similar. At the same time, in some samples, the presence of specific genera was characterized by only one sequence: either ITS1 or ITS2. Based on the analysis of the abundance of both barcode reads in the samples, the following order could describe the change with time in the dominant species in the air: Poa, Alopecurus, and Arrhenatherum in early mid-June, Lolium, Bromus, Dactylis, and Briza in mid-late June, Phleum, Elymus in late June to early July, and Calamagrostis in early mid-July. In most samples, the number of taxa found via metabarcoding analysis was higher compared to that in the phenological observations. The semi-quantitative analysis of high-throughput sequencing data well reflects the abundance of only major grass species at the flowering stage.

Project description:BackgroundWe have developed a recombinant B cell epitope-based vaccine (BM32) for allergen-specific immunotherapy (AIT) of grass pollen allergy. The vaccine contains recombinant fusion proteins consisting of allergen-derived peptides and the hepatitis B surface protein domain preS as immunological carrier.MethodsWe conducted a randomized, double-blind, placebo-controlled AIT study to determine safety, clinical efficacy and immunological mechanism of three subcutaneous injections of three BM32 doses adsorbed to aluminum hydroxide versus aluminum hydroxide (placebo) applied monthly to grass pollen allergic patients (n=70). Primary efficacy endpoint was the difference in total nasal symptom score (TNSS) through grass pollen chamber exposure before treatment and 4weeks after the last injection. Secondary clinical endpoints were total ocular symptom score (TOSS) and allergen-specific skin response evaluated by titrated skin prick testing (SPT) at the same time points. Treatment-related side effects were evaluated as safety endpoints. Changes in allergen-specific antibody, cellular and cytokine responses were measured in patients before and after treatment.ResultsSixty-eight patients completed the trial. TNSS significantly decreased with mean changes of -1.41 (BM32/20μg) (P=0.03) and -1.34 (BM32/40μg) (P=0.003) whereas mean changes in the BM32/10μg and placebo group were not significant. TOSS and SPT reactions showed a dose-dependent decrease. No systemic immediate type side effects were observed. Only few grade 1 systemic late phase reactions occurred in BM32 treated patients. The number of local injection site reactions was similar in actively and placebo-treated patients. BM32 induced highly significant allergen-specific IgG responses (P<0.0001) but no allergen-specific IgE. Allergen-induced basophil activation was reduced in BM32 treated patients and addition of therapy-induced IgG significantly suppressed T cell activation (P=0.0063).ConclusionThe B cell epitope-based recombinant grass pollen allergy vaccine BM32 is well tolerated and few doses are sufficient to suppress immediate allergic reactions as well as allergen-specific T cell responses via a selective induction of allergen-specific IgG antibodies. (ClinicalTrials.gov number, NCT01445002.).

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Atmospheric modelling of grass pollen rupturing mechanisms for thunderstorm asthma prediction.

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