Title Page:Article Type: Letter to the EditorTitle: Anaphylaxis to a blood feeding leechAuthors: Carmen H. Li MSc1,2*, Maggie Jiang MD3*, Gabriele Gadermaier PhD4, Sebastian Kvist PhD5,6,7 Julia E. M. Upton MD8,9, Xiaojun Yin PhD1, Jennifer A. Hoang MSc MDS1,10, Mikhail Monteiro BSc1, Lisa Hung PhD1,10, Akash Kothari MSc1,2, Theo J. Moraes MD PhD1,9, Peter Vadas MD PhD3,10**, Thomas Eiwegger MD1,10,11,12***Co-first author**Co-senior author(1) Translational Medicine Program, Research Institute, Hospital for Sick Children, Toronto, ON, Canada(2) Institute of Medical Science, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada(3) Division of Clinical Immunology and Allergy, St. Michael’s Hospital(4) Department of Biosciences and Medical Biology, Paris Lodron University Salzburg, Salzburg, Austria(5) Department of Ecology and Evolutionary Biology, University of Toronto, ON, Canada(6) Department of Invertebrate Zoology, Royal Ontario Museum, Toronto, ON, Canada(7) Swedish Museum of Natural History, Stockholm, Sweden(8) Division of Immunology and Allergy, Food Allergy and Anaphylaxis Program, The Hospital for Sick Children(9) Department of Pediatrics, University of Toronto, Toronto, ON, Canada(10) Department of Immunology, Temerty Faculty of Medicine, University of Toronto, Ontario, Toronto, Canada(11) Karl Landsteiner University of Health Sciences, Krems, Austria(12) Department of Pediatric and Adolescent Medicine, University Hospital St. Pölten, St. Pölten, AustriaCorrespondence:  Thomas Eiwegger, MDChair, Department of Pediatric and Adolescent MedicineUniversity Hospital St. PöltenDunant-Platz 1, 3100 St. Pölten, AustriaEmail: [email protected].: +43 2742-9004-11740

Objectives This study aimed to assess the association between postpartum hospital length-of-stay and the composition of gut microbiota at 3 and 12 months of age in different birth modes. Design Prospective cohort of Canadian infants from the Canadian Healthy Infant Longitudinal Development (CHILD) Study born between 2008 and 2012. Setting General community. Sample 1313 infants from three study sites (Edmonton, Vancouver, and Winnipeg) of the CHILD cohort Methods Duration of hospital stay was documented in hospital records. Infants’ gut microbiota was characterized by Illumina 16S rRNA sequencing of fecal samples at 3 and 12 months. Main outcome measures Infant gut microbiota profiles. Results: In the absence of maternal intrapartum antibiotic (IAP) exposure, vaginally delivered infants (VD) with a longer hospital length-of-stay (LOS) had a higher abundance of bacteria in their gut known to cause hospital-acquired Infections (HAI), including Enterococcus at 3 months and 12 months and Citrobacter at 3 months of age. Moreover, HAI-causing bacteria Enterobacteriaceae were more abundant in later infancy in postnatal prolonged hospital stayed IAP-exposed caesarean section (CS) infants. Enterococcus or Citrobacter abundance at 3 months significantly mediated the association of LOS with low relative abundance of Bacteroidaceae and a high relative abundance of Enterococcaeae/Bacteriodaceae or Enterobacteriaceae/Bacteroidaceae ratio at 12 months of age in VD infants without IAP exposure. Conclusions LOS after birth is associated with infant gut dysbiosis. Further research is needed to explore the health outcomes of these associations.

Background: The ‘old friends’ hypothesis posits that reduced exposure to previously ubiquitous microorganisms is one factor involved in the increased rates of allergic diseases. Cytomegalovirus (CMV) may be one of the “old friends” hypothesized to help prevent allergic diseases. We sought to elucidate whether early-life CMV infection is associated with childhood atopy via perturbations of the gut microbiota. Methods: Participants were recruited from a population-based birth cohort (CHILD study) and followed prospectively until age five years in four Canadian cities. A total of 928 participants provided stool microbiome data, urine for CMV testing, skin-prick tests, and questionnaires-based detailed environmental exposures. CMV infection was assessed in the first year of life while the main outcome was defined by persistent sensitization to any allergen at ages 1, 3, and 5 years. Results: Early CMV infection was associated with increased beta and decreased alpha diversity of the gut microbiota. Both changes in diversity measures and early CMV infection were associated with persistent allergic sensitization at age 5 years (aOR= 2.08; 95%CI: 1, 4.33). Mediation analysis demonstrated that perturbation of gut microbial composition explains 30% of the association. Conclusions: Early-life CMV infection is associated with an alteration in the intestinal microbiota, which mediates the effect of the infection on childhood atopy. This work indicates that preventing CMV infection would not put children at increased risk of developing atopy. Rather, a CMV vaccine, in addition to preventing CMV-associated morbidity and mortality, might reduce the risk of childhood allergic diseases.

Introduction: Children with a history of bronchopulmonary dysplasia (BPD) may have lower physical activity levels, but evidence to date is based on self-report. This study compared physical activity levels between children born extremely preterm with and without history of BPD, and examined their associations with pulmonary magnetic resonance imaging (MRI) and pulmonary function test (PFT) indices. Methods: This multi-centre cross-sectional study included children aged 7-9 years born extremely preterm, with and without BPD. Children wore a pedometer for one week, then completed the Physical Activity Questionnaire (PAQ), pulmonary MRI, and PFT. Spearman correlations and multivariable linear regression modelling were performed. Results: Of 45 children, 28 had a history of moderate-severe BPD. There were no differences in any physical activity outcomes by BPD status. Higher average daily step count and higher average daily moderate-vigorous physical activity (MVPA) were each correlated with greater forced vital capacity (r=0.41 and 0.58), greater MRI lung proton density at full expiration (r=0.42 and 0.49), and lower lung clearance index (r=-0.50 and -0.41). After adjusting for MRI total proton density and BPD status, a 5% increase in forced expiratory volume at one second was associated with 738 (95%CI: 208, 1268) more steps per day and 0.1 (0.0, 0.2) more hours of MVPA, respectively. Conclusion: School-aged children born extremely preterm have similar physical activity levels to their peers, regardless of history of BPD. MRI and PFT measures suggestive of gas trapping and/or airflow obstruction are associated with lower physical activity levels.

Background: The ‘old friends’ hypothesis posits that reduced exposure to previously ubiquitous microorganisms is one factor involved in the increased rates of allergic diseases. Cytomegalovirus (CMV) may be one of the “old friends” hypothesized to help prevent allergic diseases. We sought to elucidate whether early-life CMV infection is associated with childhood atopy via perturbations of the gut microbiota. Methods: Participants were recruited from a population-based birth cohort (CHILD study) and followed prospectively until age five years in four Canadian cities. A total of 928 participants provided stool microbiome data, urine for CMV testing, skin-prick tests, and questionnaires-based detailed environmental exposures. CMV infection was assessed in the first year of life while the main outcome was defined by persistent sensitization to any allergen at ages 1, 3, and 5 years. Results: Early CMV infection was associated with increased beta and decreased alpha diversity of the gut microbiota. Both changes in diversity measures and early CMV infection were associated with persistent allergic sensitization at age 5 years (aOR= 2.08; 95%CI: 1, 4.33). Mediation analysis demonstrated that perturbation of gut microbial composition explains 30% of the association. Conclusions: Early-life CMV infection is associated with an alteration in the intestinal microbiota, which mediates the effect of the infection on childhood atopy. This work indicates that preventing CMV infection would not put children at increased risk of developing atopy. Rather, a CMV vaccine, in addition to preventing CMV-associated morbidity and mortality, might reduce the risk of childhood allergic diseases.

Advances in molecular biology alongside the accelerated development of gene and cell engineering have contributed to the development of several endotype-targeted biological therapies against chronic immune-mediated allergic diseases. Conventional therapies for asthma, chronic rhinosinusitis with polyposis (CRSwNP), chronic spontaneous urticaria and atopic dermatitis (AD) are not without limitations, and as such the advent of biological therapies have provided a promising alternative treatment option. Biologicals have proven efficacious in the treatment of refractory chronic spontaneous urticaria, asthma, AD, CRSwNP and there is increasing evidence for their utility in treating food allergy. Biologicals are applied and investigated for the most urgent need: acute treatment, symptom control and reduction of steroid usage. Currently there are five approved biologicals for allergic disease management, targeted against IgE (omalizumab), type 2 (T2) cytokines and cytokine receptors (IL-4Ra; dupilumab, IL-5; mepolizumab/reslizumab, IL-5Ra; benralizumab).

Objective: The potential benefit of a combined adenotonsillectomy and bronchoscopy with bronchoalveolar lavage (TA-B-BAL) in preschool children with asthma has been debated in the literature. We aimed to describe the clinical course of preschool children with severe asthma undergoing this combined procedure. Study Design: This is a retrospective case-control study. Patient Selection: Preschool patients diagnosed with severe asthma who underwent TA-B-BAL treatment between 2012 and 2019 were included as cases. Controls were age and sex matched patients receiving standard asthma care. Methodology: A retrospective patient chart review was conducted. Data on demographics, clinical characteristics, medication use, virology and microbiology from bronchoalveolar lavage, and asthma control questionnaires were collected. Cases and controls were compared with t-tests and regression analysis. Results: Eighteen preschool subjects (mean age 3.19±1.13 years) in the case group were matched to eighteen control subjects receiving standard care. A Poisson mixed effects regression analysis revealed reduced risk of oral corticosteroid use (RR 0.39, 95%CI 0.18, 0.83, p=0.014), reduced emergency department visits (RR 0.36, 95%CI 0.17, 0.75, p=0.01) and reduced risk of asthma exacerbations (RR 0.58, 95%CI 0.28, 1.20, p=0.14) in cases compared to controls. Ten patients experienced clinically meaningful improvements in TRACK scores after the procedure (p<0.001). Conclusion: This pilot study provides early evidence that preschool children with severe asthma may benefit from combined adenotonsillectomy and bronchoscopy with bronchoalveolar lavage procedure. The procedure is a useful adjunct for reduction of medication use and hospital visits for preschool age patients with severe asthma.

Background: Asthma is a multifactorial disease with numerous associated genetic and environmental risk factors, however, gene-environment interactions are poorly understood in modulating disease risk. This study determines the polygenic effects of multiple genetic loci and interactions with environmental exposures during early infancy on risk of recurrent wheeze and asthma in pre-school aged children. Methods: We conducted genome-wide association studies (GWAS) and applied a thresholding method to calculate genetic risk scores (GRS) of recurrent wheeze and asthma in 2835 children of the CHILD Cohort Study. Recurrent wheeze was defined as two or more episodes in one year between ages 2-5 years and asthma was diagnosed at age 5 years. In addition, we tested for interaction effects between the GRS and environmental exposures on these respiratory outcomes. Results: GWAS identified associations with known asthma loci on chromosome 17q12 - 17q21 (p < 5e-8). GRS analysis determined that the weighted addition of alleles at four childhood-asthma loci correlated with more than 2-fold higher prevalence of recurrent wheeze (p =1.5e-08) and asthma (p = 9.4e-08) between high vs. low GRS groups. In addition, the GRS interacts with breastfeeding (p = 0.02) and traffic air pollution (NO2; p < 0.01) during the first year of life to modulate risk of recurrent wheeze and childhood-onset asthma. Conclusions: This study reports polygenic effects of multiple genetic loci, which interact with early-life exposures, to determine risk of respiratory outcomes during early childhood. Thus, asthma risk may be determined early in infancy when exposures may modulate genetic risk.