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Medical Journal Review

April 2021

WAO Reviews – Editors’ Choice

Articles are selected for their importance to clinicians who care for patients with asthma and allergic/immunologic diseases by Juan Carlos Ivancevich, MD, and John J. Oppenheimer, MD - FACAAI - FAAAAI, WAO Reviews Editor.

Predicting the severity of the grass pollen season and the effect of climate change in Northwest Europe
Kurgansky A, Creer S, De Vere N et al
Science Advances 2021;7(13):eabd7658 (16 March)

The authors of this study note that managing allergic rhinitis symptoms is challenging and requires timely intervention. They further note two major questions often posed by those with allergic rhinitis. How should I prepare for the forthcoming season? How will the season’s severity develop over the years? To answer these questions, they propose two previously unexplored approaches for forecasting the severity of the grass pollen season based on statistical and mechanistic models. The results suggest annual severity is largely governed by pre-seasonal meteorological conditions. The mechanistic model suggests climate change will increase the season severity by up to 60%, in line with experimental chamber studies. These models can be used as forecasting tools for advising individuals with hay fever and health care professionals how to prepare for the grass pollen season.

Anaphylaxis in middle-aged patients
Francuzik W, Kraft M, Scherer Hofmeier K et al
Allergologie Select 2021;5(1):133-139 (23 March)

Prior studies have shown that age is an important factor that influences the course of anaphylaxis; moreover, the specific elicitors of anaphylaxis are age-associated. In this study,  Francuzik and colleagues analyzed 8,465 anaphylactic episodes in adult patients in three age groups with a focus on patients in the middle-age group (35 – 65 years old), finding that insect venom was the most frequent trigger in this age group (51.2%), followed by drugs (22.8%) and food (17.3%). Severe reactions were observed in 40.1% of middle-aged patients and occurred more frequently in this age group than in patients below 35 years (27.6%), but less frequently than in patients over 65 years (55.6%). The symptoms and comorbidity profile also changed with age, notably with increased rates of concomitant cardiologic diseases and (severe) cardiovascular symptoms.

Does airborne pollen influence COVID-19 outbreak?
Khaiwal R, Goyal A, Mor S
Sustainable Cities and Society 2021;70:102887 (27 March)

The rapid spread of SARS-CoV-2 presents a worldwide challenge to public health, the economy, and educational system affecting human society’s welfare, with high transmission rates and increasing evidence of COVID-19 spread via bioaerosols. This review by Khaiwal and colleagues examines airborne pollen’s impact on COVID-19 transmission and explores the major gaps for post-pandemic research. They found a paucity of studies focusing on the impact of airborne pollen on SARS-CoV-2, reinforcing the need for future research. They did find that allergic rhinitis and asthma patients were found to have pre-modified immune activation, which could help to provide protection against COVID-19. The authors note that whether airborne pollen acts as a potent carrier for SARS-CoV-2 transport, dispersal, and its proliferation still requires further research.

The Hygiene Hypothesis and new perspectives – Current challenges meeting an old postulate
Garn H, Potaczek DP, Pfefferle PI
Frontiers in Immunology 2021;12:637087 (18 March)

Since its first description over 30 years ago, the Hygiene Hypothesis has evolved as new scientific developments have been occurred. In this review, Garn and colleagues explore selected new developments in relation to their impact on further fine-tuning and expansion of the Hygiene Hypothesis. This includes the role of recently discovered classes of innate and adaptive immune cells that challenges the old Th1/Th2 paradigm and the applicability of the Hygiene Hypothesis to newly identified allergy/asthma phenotypes with diverse underlying patho-mechanistic endotypes. It also includes recent knowledge derived from epigenetic studies that have led to better understanding of mechanisms involved in the translation of environmental impacts on biological systems.

An antibiotic-impacted microbiota compromises the development of colonic regulatory T cells and predisposes to dysregulated immune responses
Zhang X, Borbet TC, Fallegger A et al
mBIO 2021;12(1):e03335-20

Prior research has shown that exposure early in life as well as other practices that impact the vertical transmission and ordered assembly of a diverse and balanced gut microbiota are associated with a higher risk of immunological and metabolic disorders, including: asthma and allergy, autoimmunity, obesity, and susceptibility to opportunistic infections. In this study, Zhang and colleagues utilized a mouse model of perinatal exposure to the broad-spectrum antibiotic ampicillin to examine how the acquisition of a dysbiotic microbiota affects neonatal immune system development. They found that the resultant dysbiosis imprints in a manner that is irreversible after weaning, leading to specific and selective alteration of the colonic CD41 T-cell compartment. In contrast, colonic granulocyte and myeloid lineages and other mucosal T-cell compartments are unaffected. Among colonic CD41 T cells, they observed the most pronounced effects on neuropilin-negative, RORgt- and Foxp3-positive regulatory T cells, which are largely absent in antibiotic exposed mice even as they reach adulthood. Immunomagnetically isolated dendritic cells from antibiotic-exposed mice fail to support the generation of Foxp31 regulatory T cells (Tregs) from naive T cells ex vivo. The perinatally acquired dysbiotic microbiota predisposes to dysregulated effector T-cell responses to Citrobacter rodentium or ovalbumin challenge. The transfer of the antibiotic-impacted, but not healthy, fecal microbiota into germfree recipients recapitulates the selective loss of colonic neuropilin-negative, RORgt- and Foxp3-positive Tregs. Overall, this study indicates that the early-life acquisition of a dysbiotic microbiota has detrimental effects on the diversity and microbial community composition of offspring that persist into adulthood and predisposes to inappropriate T-cell responses that are linked to compromised immune tolerance

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