Asymptomatic surveillance testing for COVID-19 in health care professional students: lessons learned from a low prevalence setting.

The novel coronavirus disease of 2019 (COVID-19) pandemic has severely impacted the training of health care professional students because of concerns of potential asymptomatic transmission to colleagues and vulnerable patients. From May 27th, 2020, to June 23rd 2021; at a time when B.1.1.7 (alpha) and B.1.617.2 (delta) were the dominant circulating variants, PCR testing was conducted on 1,237 nasopharyngeal swabs collected from 454 asymptomatic health care professional students as they returned to their studies from across Canada to Kingston, ON, a low prevalence area during that period for COVID-19. Despite 46.7% of COVID-19 infections occurring in the 18-29 age group in Kingston, severe-acute-respiratory coronavirus-2 was not detected in any of the samples suggesting that negligible asymptomatic infection occurred in this group and that PCR testing in this setting may not be warranted as a screening tool.

Environmental exposure unit simulates natural seasonal birch pollen exposures while maximizing change in allergic symptoms.

BACKGROUND: Birch pollen is a prevalent aeroallergen during the springtime allergy season. In field studies, variable allergen exposure and environmental factors can affect data quality while environmental exposure units (EEUs) deliver controlled, standardized, and reproducible allergen exposures. OBJECTIVE: To inform study design for EEU trials evaluating antiallergic therapies. METHODS: In this prospective study, 76 participants with birch allergy experienced 3 exposures to birch pollen: (1) an out-of-season EEU challenge (two 3-hour sessions on consecutive days); (2) a natural seasonal exposure; and (3) an in-season EEU challenge (3-hour exposure for 2 weeks after birch pollen season initiation). RESULTS: The total nasal symptom score, total ocular symptom score, and total symptom score (TSS = total nasal symptom score plus total ocular symptom score) were assessed every 30 minutes and daily during EEU and natural exposures. A high association between TSSs and day 2 of the out-of-season and in-season EEU challenges was noted, with a good association between the maximum TSS during the natural and in-season EEU challenges, and natural season and day 2 of the out-of-season EEU challenge (P < .001 for all). Participants had higher maximum change from the baseline TSS during day 2 of the out-of-season EEU challenge (12.4) vs the following: (1) first day (9.8); (2) in-season EEU challenge (8.4); and (3) natural seasonal exposure (7.6) (P < .001 for all). CONCLUSION: A strong association was seen between the presence of allergy symptoms and exposure to birch pollen in the EEU (maximum change in symptom scores during day 2) and in the field. A hybrid trial design may be useful to demonstrate the clinical efficacy of novel antiallergic therapies requiring fewer participants and shorter timelines and expediting treatment availability.

Clinical validation of controlled exposure to house dust mite in the environmental exposure unit (EEU).

RATIONALE: The Environmental Exposure Unit (EEU), a controlled allergen exposure model of allergic rhinitis (AR), has traditionally utilized seasonal allergens. We sought to clinically validate the use of house dust mite (HDM), a perennial allergen, in the HDM-EEU, a specially designed facility within the larger EEU. METHODS: Forty-four HDM-allergic and eleven non-allergic participants were screened and deemed eligible for one of two 3-h exposure sessions in the HDM-EEU. Participants were exposed to a modest or higher HDM target, with blood and nasal brushing samples collected before and after allergen exposure. Symptomatic data, including Total Nasal Symptom Score (TNSS), Total Ocular Symptom Score (TOSS), Total Rhinoconjunctivitis Symptom Score (TRSS), and Peak Nasal Inspiratory Flow (PNIF) were collected at baseline, every 30 min until 3 h, on an hourly basis for up to 12 h, and at 24 h following the onset of HDM exposure. RESULTS: The modest and higher HDM target sessions respectively featured cumulative total particle counts of 156,784 and 266,694 particles (2.5-25 µm), Der f 1 concentrations of 2.67 ng/m3 and 3.80 ng/m3, and Der p 1 concentrations of 2.07 ng/m3 and 6.66 ng/m3. Allergic participants experienced an increase in symptoms, with modest target participants plateauing at 1.5 to 2 h and achieving a mean peak TNSS of 5.74 ± 0.65, mean peak TOSS of 2.47 ± 0.56, and mean peak TRSS of 9.16 ± 1.32. High HDM-target allergics reached a mean peak TNSS of 8.17 ± 0.71, mean peak TOSS of 4.46 ± 0.62, and mean peak TRSS of 14.08 ± 1.30 at 3 h. All allergic participants' symptoms decreased but remained higher than baseline after exiting the HDM-EEU. Sixteen participants (37.2%) were classified as Early Phase Responders (EPR), eleven (25.6%) as protracted EPR (pEPR), seven (16.3%) as Dual Phase Responders (DPR), and nine (20.9%) as Poor Responders (PR). Allergic participants experienced significant percent PNIF reductions at hours 2 and 3 compared to healthy controls. Non-allergics were asymptomatic during the study period. CONCLUSIONS: The HDM-EEU is an appropriate model to study HDM-induced AR as it can generate clinically relevant AR symptoms amongst HDM-allergic individuals.

Biologic Responses to House Dust Mite Exposure in the Environmental Exposure Unit.

Introduction: Allergic rhinitis (AR) is an inflammatory disease of the nasal mucosa that can be modeled using Controlled Allergen Exposure Facilities (CACF). Recently, we clinically validated the house dust mite (HDM) Environmental Exposure Unit (EEU) facility. In the current study, we aimed to assess biological responses in the blood following HDM exposure in the HDM-EEU. Methods: Fifty-five participants passed a screening visit, where they provided consent and completed a skin prick test (SPT), then attended a modest or higher HDM exposure session. Baseline and post-exposure blood samples were collected. Complete blood counts with differentials were measured, and isolated serum was used to determine Dermatophagoides farinae- and Dermatophagoides pteronyssinus-specific IgE (sIgE) and cytokine concentrations (IL-4, IL-5, IL-6, IL-10, IL-13, TNF-α). Results: HDM-allergic participants had significantly greater SPT wheal sizes than healthy controls. sIgE concentrations were significantly greater in allergic participants, with a strong correlation between Dermatophagoides farinae and Dermatophagoides pteronyssinus. Serum eosinophil counts were significantly decreased post-exposure for allergic participants. White blood cell, neutrophil, and lymphocyte counts were significantly increased for both allergic and non-allergic participants post-exposure. Serum IL-13 concentrations were significantly reduced post-exposure in allergics while TNF-α was significantly reduced in non-allergics. Conclusion: The HDM-EEU is a useful model for investigating biologic mechanisms of HDM-induced AR. Allergic participants produced measurable biological changes compared to healthy controls following allergen exposure, specifically with serum expression of eosinophils and related markers, namely IL-5, which promotes the proliferation and differentiation of eosinophils, and IL-13, a cytokine released by eosinophils. The exact mechanisms at play require further investigation.

Clinical symptoms and biomarkers of Bermuda grass-induced allergic rhinitis using the nasal allergen challenge model.

BACKGROUND: Bermuda grass is a prevalent allergen that flourishes in tropical climates. Its exposure is traditionally believed to be low in Ontario due to the colder environment. However, high sensitization rates have been observed in Kingston, Ontario. OBJECTIVE: We sought to investigate whether its allergens can provoke allergic rhinitis (AR) symptoms in sensitized participants from south-eastern Ontario and determine if nasal allergen challenge (NAC) model is appropriate to study Bermuda grass-induced AR. METHODS: Twenty-one participants sensitized to Bermuda grass and 12 nonallergic participants completed a titrated NAC with increasing allergen concentrations at a screening visit. Total nasal symptom score (TNSS) and peak nasal inspiratory flow were collected before allergen exposure and 10 minutes after delivery of each concentration. Twelve participants with a Bermuda grass allergy who met the qualifying criteria (TNSS ≥ 8 and peak nasal inspiratory flow fall ≥ 50%) and 11 nonallergic controls returned for single-dose NAC visit. RESULTS: At titrated NAC, 19 of 21 sensitized participants met the criteria of positive allergic response when challenged. During single-dose NAC, participants with allergy had significantly greater TNSS between 15 minutes and 3 hours after NAC than controls. Likewise, allergic participants had a significantly increased number of nasal lavage eosinophils at both 1 and 6 hours after NAC. Bermuda grass-specific immunoglobulin E was significantly increased in Bermuda grass allergic participants at NAC than screening visit. CONCLUSION: Although Bermuda grass is a non-native allergen in Ontario, it can induce AR symptoms in sensitized participants, and the NAC model is appropriate to study Bermuda grass-induced AR.

Repeatability of nasal allergen challenge results: Further validation of the allergic rhinitis clinical investigator collaborative protocols.

BACKGROUND: Nasal allergen challenge (NAC) models have been used to study allergic rhinitis and new therapies. Symptoms and biological samples can be evaluated at time points after allergen exposure. OBJECTIVE: To verify protocol repeatability and adequate interval between allergen exposures. METHODS: Ten ragweed allergic participants were exposed to incrementally increasing dosages of ragweed allergen intranasally until they achieved a total nasal symptom score (TNSS) of 8 of 12 and a peak nasal inspiratory flow (PNIF) of 50% reduction or more from baseline. Three weeks later, participants were challenged with a cumulative dose equal to the sum of all the allergen doses received at screening. TNSS and PNIF were recorded at regular intervals, including a 24-hour assessment. A subsequent visit was conducted after a further 3 weeks. Nasal secretion samples were collected for cytokine and eosinophil quantification. RESULTS: Nine participants completed all visits. TNSS and PNIF responses followed previous patterns, with an initial peak at 30 minutes followed by a gradual decline. Most participants reported similar patterns at both NAC visits, although some did not demonstrate the same phenotype at both visits. Some experienced a secondary symptom increase 24 hours after NAC. Eosinophil and cytokine sections followed a similar pattern at both NAC visits. CONCLUSION: NAC is an adequate method for modeling AR in humans, demonstrating appropriate repeatability of symptoms, nasal mucosal eosinophil, and cytokines. The 24-hour time point, previously not studied in our model, may be beneficial in evaluation of long-acting medications. This three-week interval NAC model will be beneficial for studies in which before and after treatment comparisons are desired.

Investigating Immune Gene Signatures in Peripheral Blood from Subjects with Allergic Rhinitis Undergoing Nasal Allergen Challenge.

Nasal allergen challenge (NAC) is a human model of allergic rhinitis (AR) that delivers standardized allergens locally to the nasal mucosa allowing clinical symptoms and biospecimens such as peripheral blood to be collected. Although many studies have focused on local inflammatory sites, peripheral blood, an important mediator and a component of the systemic immune response, has not been well studied in the setting of AR. We sought to investigate immune gene signatures in peripheral blood collected after NAC under the setting of AR. Clinical symptoms and peripheral blood samples from AR subjects were collected during NAC. Fuzzy c-means clustering method was used to identify immune gene expression patterns in blood over time points (before NAC and 1, 2, and 6 h after NAC). We identified and validated seven clusters of differentially expressed immune genes after NAC onset. Clusters 2, 3, and 4 were associated with neutrophil and lymphocyte frequencies and neutrophil/lymphocyte ratio after the allergen challenge. The patterns of the clusters and immune cell frequencies were associated with the clinical symptoms of the AR subjects and were significantly different from healthy nonallergic subjects who had also undergone NAC. Our approach identified dynamic signatures of immune gene expression in blood as a systemic immune response associated with clinical symptoms after NAC. The immune gene signatures may allow cross-sectional investigation of the pathophysiology of AR and may also be useful as a potential objective measurement for diagnosis and treatment of AR combined with the NAC model.

A novel pathogenic pathway of immune activation detectable before clinical onset in Huntington's disease.

Huntington's disease (HD) is an inherited neurodegenerative disorder characterized by both neurological and systemic abnormalities. We examined the peripheral immune system and found widespread evidence of innate immune activation detectable in plasma throughout the course of HD. Interleukin 6 levels were increased in HD gene carriers with a mean of 16 years before the predicted onset of clinical symptoms. To our knowledge, this is the earliest plasma abnormality identified in HD. Monocytes from HD subjects expressed mutant huntingtin and were pathologically hyperactive in response to stimulation, suggesting that the mutant protein triggers a cell-autonomous immune activation. A similar pattern was seen in macrophages and microglia from HD mouse models, and the cerebrospinal fluid and striatum of HD patients exhibited abnormal immune activation, suggesting that immune dysfunction plays a role in brain pathology. Collectively, our data suggest parallel central nervous system and peripheral pathogenic pathways of immune activation in HD.