Enhanced Airway Epithelial Response to SARS-CoV-2 Infection in Children is Critically Tuned by the Cross-Talk Between Immune and Epithelial Cells (preprint)

To cope with novel virus infections to which no prior adaptive immunity exists, the body strongly relies on the innate immune system. In such cases, including infections with SARS-CoV-2, children tend to fair better than adults. In the context of COVID-19, it became evident that a rapid interferon response at the site of primary infection is key for successful control of the virus and prevention of severe disease. The airway epithelium of children was shown to exhibit a primed state already at homeostasis and to respond particularly well to SARS-CoV-2 infection. However, the underlying mechanism for this priming remained elusive. Here we show that interactions between airway mucosal immune cells and epithelial cells are stronger in children, and via cytokine-mediated signaling lead to IRF-1-dependent upregulation of the viral sensors RIG-I and MDA5. Based on a cellular in vitro model we show that stimulated human peripheral blood mononuclear cells (PBMC) can induce a robust interferon-beta response towards SARS-CoV-2 in a lung epithelial cell line otherwise unresponsive to this virus. This is mediated by type I interferon, interferon-gamma and TNF, and requires induction of both, RIG-I and MDA5. In single cell-analysis of nasal swab samples the same cytokines are found to be elevated in mucosal immune cells of children, correlating with elevated epithelial expression of viral sensors. In vitro analysis of PBMC derived from healthy adolescents and adults confirm that immune cells of younger individuals show increased cytokine production and potential to prime epithelial cells. In co-culture with SARS-CoV-2-infected A549 cells, PBMC from adolescents significantly enhance the antiviral response. Taken together, our study suggests that higher numbers and a more vigorous activity of innate immune cells in the airway mucosa of children tune the set-point of the epithelial antiviral system. This likely is a major contributor to the robust immune response to SARS-CoV-2 in children. Our findings shed light on the molecular underpinnings of the stunning resilience of children towards severe COVID-19, and may propose a novel concept for immunoprophylactic treatments.

Health-Related Quality of Life and Impact of Socioeconomic Status among Primary and Secondary School Students after the third COVID-19 Wave in Berlin, Germany (preprint)

In the earlier phases of the COVID-19 pandemic, studies in Germany and elsewhere found an overall reduction in health-related quality of life (HRQoL) among students. However, there is little evidence on later pandemic stages as well as socioeconomic influencing factors. We aimed to 1) describe HRQoL in a Berlin student cohort at two time points in mid-2021, and to 2) analyze the effects of household income and education. We assessed HRQoL of students from 24 randomly selected primary and secondary schools in Berlin, Germany with the KIDSCREEN-10 index in June and September 2021. To adjust for non-response bias, inverse probability weighting was applied. The potential effects of both household income and education (lower vs. higher) were estimated in generalized linear mixed models, based on prior assumptions presented in directed acyclic graphs. Our cohort comprised 660 students aged 7-19 years. In June 2021, 11.3% reported low HRQoL, whereas in September 2021, this increased to 13.7%, with adolescent girls more frequently reporting low HRQoL than boys and younger children at both time points (20% and 29%). While there was no statistically significant total effect of lower household income on HRQoL, a negative effect of lower household education was statistically significant (β = -2.15, SE = 0.95, 95% CI = -4.01 to -0.29, p = 0.024). In summary, students’ HRQoL in mid-2021 was better than that documented in other studies conducted at pandemic onset. Female adolescents reported low HRQoL more often, and lower household education significantly reduced children's HRQoL. Support strategies for psychosocial wellbeing should consider socioeconomically disadvantaged children as important target groups.

Cross-reactive CD4+ T cells enhance SARS-CoV-2 immune responses upon infection and vaccination (preprint)

While evidence for pre-existing SARS-CoV-2-cross-reactive CD4+ T cells in unexposed individuals is increasing, their functional significance remains unclear. Here, we comprehensively determined SARS-CoV-2-cross-reactivity and human coronavirus-reactivity in unexposed individuals. SARS-CoV-2-cross-reactive CD4+ T cells were ubiquitous, but their presence decreased with age. Within the spike glycoprotein fusion domain, we identified a universal immunodominant coronavirus-specific peptide epitope (iCope). Pre-existing spike- and iCope-reactive memory T cells were efficiently recruited into mild SARS-CoV-2 infections and their abundance correlated with higher IgG titers. Importantly, the cells were also reactivated after primary BNT162b2 COVID-19 mRNA vaccination in which their kinetics resembled that of secondary immune responses. Our results highlight the functional importance of pre-existing spike-cross-reactive T cells in SARS-CoV-2 infection and vaccination. Abundant spike-specific cross-immunity may be responsible for the unexpectedly high efficacy of current vaccines even with single doses and the high rate of asymptomatic/mild infection courses.

SARS-CoV-2 infection and transmission in school settings during the second wave in Berlin, Germany: a cross-sectional study (preprint)

Background: School attendance during the SARS-CoV-2 pandemic is intensely debated. Modelling studies suggest that school closures contribute to community transmission reduction. However, data among school-attending students and staff are scarce. In November 2020, we examined SARS-CoV-2 infections and seroreactivity in 24 randomly selected school classes and connected households in Berlin, Germany. Methods: Students and school staff were examined, oro-nasopharyngeal swabs and blood samples collected, and SARS-CoV-2 infection and IgG antibodies detected by RT-PCR and ELISA. Household members performed self-swabs. Individual and institutional infection prevention and control measures were assessed. Classes with SARS-CoV-2 infection and connected household members were re-tested after one week. Findings: 1119 participants were examined, including 177 primary and 175 secondary school students, 142 staff, and 625 household members. Participants reported mainly cold symptoms (19.4%). SARS-CoV-2 infection occurred in eight of 24 classes affecting each 1-2 individuals. Infection prevalence was 2.7% (95%CI, 1.2-5.0%; 9/338), 1.4% (0.2-5.1%; 2/140), and 2.3% (1.3-3.8%; 14/611) among students, staff and household members, respectively, including quarantined persons. Six of nine infected students were asymptomatic. Prevalence increased with inconsistent facemask use in school, way to school on foot, and case-contacts outside school. IgG antibodies were detected in 2.0% (0.8-4.1%; 7/347), 1.4% (0.2-5.0%; 2/141) and 1.4% (0.6-2.7%; 8/576), respectively. For three of nine households with infection(s) detected at cross-sectional assessment, origin in school seemed possible. After one week, no school-related, secondary infections appeared in affected classes; the attack rate in connected households was 1.1%. Interpretation: These data suggest that school attendance under preventive measures is feasible, provided their rigorous implementation. In balancing threats and benefits of open versus closed schools during the pandemic, parents and society need to consider possible spill-overs into their households. Deeper insight is needed into the infection risks due to being a schoolchild as compared to attending school. Funding: Senate of Berlin.

SARS-CoV-2 infection, risk perception, behaviour, and preventive measures at schools in Berlin, Germany, during the early post-lockdown phase: A cross-sectional study (preprint)

BackgroundBriefly before the first peak of the COVID-19 pandemic in Berlin, Germany, schools closed in mid-March 2020 for six weeks. Following re-opening, schools gradually resumed operation at a reduced level for nine weeks preceding the summer holidays. AimDuring this phase, we conducted a situational assessment in schools among students and teachers as to infection status, symptoms, affective, behavioural, educational issues, and preventive measures. MethodsAt twenty-four randomly selected primary and secondary schools, one class each was examined. Oro-nasopharyngeal swabs and capillary blood samples were collected to assess SARS-CoV-2 infection (PCR) and specific IgG (ELISA), respectively. Medical history, household and schooling characteristics, leisure time activities, fear of infection, risk perception, hand hygiene, physical distancing, and facemask wearing were assessed. ResultsAmong 535 participants (385 students, 150 staff), one teenager was SARS-CoV-2 infected (0.2%), and seven individuals exhibited specific IgG (1.3%); 16% reported symptoms upon examination, and 48% in the preceding 14 days. Compared to before the pandemic, the proportion of leisure time spent as screen-time increased, and the majority of primary school students reported reduced physical activity. Fear of infection and risk perception were relatively low, but acceptance of adapted health behaviours was high. Governmental preventive measures were adequately implemented, with primary schools performing better than secondary schools. ConclusionIn this phase of rare infection and low seroreactivity, individual and school-level infection prevention and control measures were largely adhered to. Nevertheless, vigilance, continued and proactive preventive measures, and well-rehearsed reaction options are essential to cope with increasing pandemic activity.

SARS-CoV-2 infections in kindergartens and associated households at the start of the second wave in Berlin, Germany - a cross sectional study (preprint)

ObjectivesThe comparatively large proportion of asymptomatic SARS-CoV-2 infections in the youngest children opens up the possibility that kindergartens represent reservoirs of infection. However, actual surveys in kindergartens beyond individual outbreaks are rare. At the beginning of the second pandemic wave in Berlin, Germany, i.e., end of September 2020, we screened SARS-CoV-2 infections among kindergarten children, staff and connected household members. MethodsTwelve kindergartens were randomly selected in the Berlin metropolitan area, and a total of 720 participants were recruited (155 pre-school children, 78 staff, 487 household members). Participants were briefly examined and interviewed, and SARS-CoV-2 infections and anti-SARS-Cov-2 IgG antibodies were assessed. ResultsSigns and symptoms, largely resembling common cold, were present in 24.2% of children and 28.9% of staff. However, no SARS-CoV-2 infection was detected among 701 PCR-tested individuals, and only one childcare worker showed IgG seroreactivity (0.15%; 1/672). ConclusionsAgainst a backdrop of increased pandemic activity in the community, this cross-sectional study does not suggest that kindergartens are silent transmission reservoirs. Nevertheless, at increasing pandemic activity, reinforced precautionary measures and repeated routine testing appears advisable.

Studying the pathophysiology of coronavirus disease 2019 - a protocol for the Berlin prospective COVID-19 patient cohort (Pa- COVID-19) (preprint)

Purpose Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide causing a global health emergency. Pa-COVID-19 aims to provide comprehensive data on clinical course, pathophysiology, immunology and outcome of COVID-19, in order to identify prognostic biomarkers, clinical scores, and therapeutic targets for improved clinical management and preventive interventions. Methods Pa-COVID-19 is a prospective observational cohort study of patients with confirmed SARS-CoV-2 infection treated at Charite - Universitaetsmedizin Berlin. We collect data on epidemiology, demography, medical history, symptoms, clinical course, pathogen testing and treatment. Systematic, serial blood sampling will allow deep molecular and immunological phenotyping, transcriptomic profiling, and comprehensive biobanking. Longitudinal data and sample collection during hospitalization will be supplemented by long-term follow-up. Results Outcome measures include the WHO clinical ordinal scale on day 15 and clinical, functional and health-related quality of life assessments at discharge and during follow-up. We developed a scalable dataset to (i) suit national standards of care (ii) facilitate comprehensive data collection in medical care facilities with varying resources and (iii) allow for rapid implementation of interventional trials based on the standardized study design and data collection. We propose this scalable protocol as blueprint for harmonized data collection and deep phenotyping in COVID-19 in Germany. Conclusion We established a basic platform for harmonized, scalable data collection, pathophysiological analysis, and deep phenotyping of COVID-19, which enables rapid generation of evidence for improved medical care and identification of candidate therapeutic and preventive strategies. The electronic database accredited for interventional trials allows fast trial implementation for candidate therapeutic agents.