Acetate Triggers Antiviral Response Mediated by RIG-I in Cells from Infants with Respiratory Syncytial Virus Bronchiolitis (preprint)

Background: Gut microbiota-derived short-chain fatty-acid (SFCA) acetate protects mice againstRSV A2 strain infection by increasing interferon-β production and expression of interferonstimulated genes (ISGs). However, the role of SFCAs in RSV infection using strains isolated from patients is unknown.Methods: We first used RSV clinical strains isolated from infants hospitalized with RSV bronchiolitis to investigate the effects of in vitro acetate treatment in human pulmonary epithelial cells. We next examined whether acetate treatment is beneficial in a mouse model of RSV infection using clinical isolates. We sought to investigate the relationship of gut microbiota and fecal acetate with disease severity among infants hospitalized with RSV bronchiolitis, and whether treating their respiratory epithelial cells with acetate ex-vivo impacts upon viral load and ISG expression. We further treated epithelial cells from SARS-CoV-2 infected patients with acetate.Findings: In vitro pre-treatment of A549 cells with acetate reduced RSV load after infection with clinical isolates and increased the expression of RIG-I and ISG15. Animals treated with acetate intranasally recovered significantly faster, with reduction in the RSV clinical isolates viral load, and increased lung expression of IFNB1 and the RIG-I receptor. Experiments in RIG-I knockout A549 cells demonstrated that the protection relies on RIG-I presence. Gut microbial profile was associated with bronchiolitis severity and with acetate in stool. Increased acetate levels were associated with increasing oxygen saturation at admission, and shorter duration of fever. Ex-vivo treatment of patients’ respiratory cells with acetate reduced RSV load and increased expression of ISGs OAS1 and ISG15, and virus recognition receptors MAVS and RIG-I, but not IFNB1. These acetate effects were not found on cells from SARS-CoV-2 infected patients.Interpretation: Acetate reduces the severity of RSV infection and RSV viral load through modulation of RIG-I expression.Funding: This study was supported by Rio Grande do Sul Research Foundation FAPERGS (FAPERGS/MS/CNPq/SESRS no. 03/2017 - PPSUS 17/2551-0001380-8 and COVID-19 20/2551-0000258-6), CNPq 312504/2017-9 and by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. P.B., C.V.B. and L.A.B. would like to acknowledge financial support given by CNPq/FAPERGS/CAPES/BNDES to the National Institute of Science and Technology on Tuberculosis (INCT-TB), Brazil [grant numbers: 421703- 2017-2/17-1265-8/14.2.0914.1).Declaration of Interest: The authors declare no competing interests.Ethical Approval: All animal procedures were performed in accordance with protocols approved by CEUA/UNICAMP (protocols 4022-1 and 4599-1).

Childhood asthma outcomes during the COVID-19 pandemic: Findings from the PeARL multi-national cohort. (preprint)

ImportanceImportance: The interplay between COVID-19 pandemic and asthma in children is still unclear. ObjectiveWe evaluated the impact of COVID-19 pandemic on childhood asthma outcomes. DesignThe PeARL multinational cohort included children with asthma and non-asthmatic controls recruited during the COVID-19 pandemic and compared current disease activity with data available from the previous year. SettingPediatric outpatient clinics. ParticipantsThe study included 1,054 children with asthma and 505 non-asthmatic controls, aged between 4-18 years, from 25 pediatric departments, from 15 countries globally. ExposuresCOVID-19 pandemic first wave, starting from the date of the first fatality in the respective country. Main outcomes and measuresWe assessed the pandemics impact on the frequency of respiratory infections, emergency presentations and hospital admissions in asthmatic versus non-asthmatic participants, controlling for confounding factors including the pandemics duration and the frequency of such acute events during 2019. Using paired analyses, we evaluated the impact of the pandemic on the annualized frequency of asthma attacks and the previously mentioned acute events, asthma control, and pulmonary function in children with asthma, compared to their baseline disease activity, during the preceding year. ResultsDuring the pandemic, children with asthma experienced fewer upper respiratory tract infections, episodes of pyrexia, emergency visits, hospital admissions, asthma attacks and hospitalizations due to asthma, in comparison to the preceding year. Sixty-six percent of asthmatic children had improved asthma control while in 33% the improvement exceeded the minimally clinically important difference. Pre-bronchodilatation FEV1 and peak expiratory flow rate were also improved during the pandemic. When compared to non-asthmatic controls, children with asthma were not found to be at increased risk of LRTIs, episodes of pyrexia, emergency visits or hospitalizations during the pandemic. However, an increased risk of URTIs emerged. Conclusions and relevanceChildhood asthma outcomes, including control, were improved during the first wave of the COVID-19 pandemic, probably because of reduced exposure to asthma triggers and increased treatment adherence. The decreased frequency of acute episodes does not support the notion that childhood asthma may be a risk factor for COVID-19. Furthermore, the potential for improving childhood asthma outcomes through environmental control becomes apparent. Key PointsO_ST_ABSQuestionC_ST_ABSWhat was the impact of COVID-19 pandemic on childhood asthma outcomes? FindingsDuring the first wave of the pandemic, children with asthma have experienced improved outcomes, as evidenced by fewer asthma attachks, hospitalizations, improved scores in validated asthma control measures and improved pulmonary function. MeaningThis is the first study to show a positive impact of COVID-19 pandemic on childhood asthma activity. This is probably the result of reduced exposure to asthma triggers and increased treatment adherence. The decreased frequency of acute episodes does not support the hypothesis that childhood asthma may be a risk factor for COVID-19.

Sex differences in innate anti-viral immune responses to respiratory viruses (preprint)

Males have excess morbidity and mortality from respiratory viral infections and especially so in COVID-19. The mechanisms explaining this excess in disease burden in males are unknown. Innate immune responses are likely critical in protection against a novel virus like SARS-CoV-2. We hypothesised that innate immune responses may be deficient in males relative to females. To test this we stimulated peripheral blood mononuclear cells (PBMCs) from participants in a population-based birth cohort with three respiratory viruses (rhinoviruses-RV-A16 and RV-A1, and respiratory syncytial virus-RSV) and two viral mimics (R848 and CpG-A, to mimic responses to SARS-CoV-2). We measured interferon (IFN) and IFN-induced chemokine responses and investigated sex differences in virus-induced responses. IFN-α, IFN-β and IFN-γ responses to RV-A16 were deficient in males compared to females, fold-inductions being 1.92-fold ( P< 0.001), 2.04-fold ( P <0.001) and 1.77-fold ( P =0.003) lower in males than females, respectively. Similar significant deficiencies in innate immune responses were observed in males for eleven other cytokine-stimulus pairs. Responses in males were greater than those in females in only one of 35 cytokine-stimulus pairs investigated. Review of healthcare records revealed that 12.1% of males but only 6.6% of females were admitted to hospital with respiratory infections in the first year of life ( P =0.017). Impaired innate anti-viral immunity in males likely results in high morbidity and mortality from respiratory viruses including COVID-19. Males may preferentially benefit from therapies that boost innate anti-viral immune responses. Significance Statement Clinical outcomes including, mortality, Intensive care unit admissions and hospital admissions, during COVID-19 disease are consistently and substantially worse in males than in females. The mechanisms underlying this increased susceptibility to severe disease in males are not understood. We hypothesised that the differential outcomes between sexes could be a consequence of deficient innate interferon responses in males, and more robust innate interferon responses in females. We have investigated such responses in a large population-based cohort and found that indeed males have deficient innate interferon responses to viral stimuli, including stimuli that mimic SARS-CoV-2 infection, relative to females. Our findings have very important treatment implications as interferons are available for clinical use with immediate effect.

Is death from Covid-19 a multistep process? (preprint)

Covid-19 death has a different relationship with age than is the case for other severe respiratory pathogens. The Covid-19 death rate increases exponentially with age, and the main risk factors are age itself, as well as having underlying conditions such as hypertension, diabetes, cardiovascular disease, severe chronic respiratory disease and cancer. Furthermore, the almost complete lack of deaths in children suggests that infection alone is not sufficient to cause death; rather, one must have gone through a number of changes, either as a result of undefined aspects of aging, or as a result of chronic disease. These characteristics of Covid-19 death are consistent with the multistep model of disease, a model which has primarily been used for cancer, and more recently for amyotrophic lateral sclerosis (ALS). We applied the multi-step model to data on Covid-19 case fatality rates (CFRs) from China, South Korea, Italy, Spain and Japan. In all countries we found that a plot of ln (CFR) against ln (age) was approximately linear with a slope of about 5. As a comparison, we also conducted similar analyses for selected other respiratory diseases. SARS showed a similar log-log age-pattern to that of Covid-19, albeit with a lower slope, whereas seasonal and pandemic influenza showed quite different age-patterns. Thus, death from Covid-19 and SARS appears to follow a distinct age-pattern, consistent with a multistep model of disease that in the case of Covid-19 is probably defined by comorbidities and age producing immune-related susceptibility. Identification of these steps would be potentially important for prevention and therapy for SARS-COV-2 infection.