Pre-activated antiviral innate immunity in the upper airways controls early SARS-CoV-2 infection in children

Children have reduced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rates and a substantially lower risk for developing severe coronavirus disease 2019 compared with adults. However, the molecular mechanisms underlying protection in younger age groups remain unknown. Here we characterize the single-cell transcriptional landscape in the upper airways of SARS-CoV-2-negative (n = 18) and age-matched SARS-CoV-2-positive (n = 24) children and corresponding samples from adults (n = 44), covering an age range of 4 weeks to 77 years. Children displayed higher basal expression of relevant pattern recognition receptors such as MDA5 (IFIH1) and RIG-I (DDX58) in upper airway epithelial cells, macrophages and dendritic cells, resulting in stronger innate antiviral responses upon SARS-CoV-2 infection than in adults. We further detected distinct immune cell subpopulations including KLRC1 (NKG2A)+ cytotoxic T cells and a CD8+ T cell population with a memory phenotype occurring predominantly in children. Our study provides evidence that the airway immune cells of children are primed for virus sensing, resulting in a stronger early innate antiviral response to SARS-CoV-2 infection than in adults.

Inhibition of endotoxin-induced perinatal asthma protection by pollutants in an experimental mouse model

BACKGROUND

One of the most promising strategies to face the increasing asthma prevalence and to prevent disease development might be an early contact with microbial compounds. However, little is known about an interaction between an early-life contact to microbial compounds leading to asthma protection in the offspring and a co-exposure to allergy-promoting pollutants.

METHODS

Pregnant BALB/c mice were repeatedly exposed to aerosolized endotoxin (lipopolysaccharide, LPS). The offspring was further exposed to aerosolized LPS before allergen sensitization with ovalbumin (OVA). Some of the mice were co-exposed to mycotoxins or diesel exhaust particles (DEP) during pregnancy. The 6-week-old offspring was immunized with OVA and analyzed in a murine asthma model.

RESULTS

While the offspring of naïve mothers developed an asthma-like phenotype, the offspring of mice perinatally exposed to LPS was significantly protected. Co-exposure of mice to mycotoxins or DEP during pregnancy inhibited the LPS-induced protection leading to the development of eosinophilic airway inflammation, airway hyperactivity, and increased antigen-specific IgE levels in the offspring. Furthermore, the asthma-preventive effect of perinatal LPS exposure was IFN-gamma dependent. Additionally, the IFN-gamma promoter of CD4+ T cells in the LPS-exposed offspring revealed a significant protection against loss of histone 4 acetylation, which was abolished after prenatal co-exposure to pollutants. Prenatal treatment of mice with the antioxidant N-acetylcysteine reversed the pollutant-induced increased asthma risk in the offspring.

CONCLUSION

Our results show that exposure to pollutants during pregnancy may cause the development of allergic asthma in the offspring by inhibiting the endotoxin-induced perinatal asthma protection.

Worsening of long-term myocardial function after successful pharmacological pretreatment with cyclosporine

Pretreatment with cyclosporine (CsA) decreases infarct size 24h after myocardial ischemia/reperfusion (I/R). The goal of this study was to determine effects of CsA pretreatment on long-term cardiac function after I/R-injury. Rats were randomly assigned to group-1: vehicle-only, group-2: CsA-5mg/kg/day, and group-3: CsA-12.5mg/kg/day given orally for three days prior to I/R-injury (30 min of left anterior descending coronary artery occlusion). Post-I/R survival and cardiac function were evaluated 14 days after I/R-injury by echocardiography and invasive hemodynamic measurements. Rats with I/R-injury showed increased left ventricular pressure (LVEDP) compared to rats without I/R-injury (p<0.005). Although CsA initially decreased infarct size, no differences of LVEDP were seen 14 days after I/R-injury (vehicle: 21.2+/-8.9 mmHg, CsA-5mg/kg/day: 21.5+/-0.7 mmHg, CsA-12.5mg/kg/day: 20.5+/-9.4 mmHg). Ejection fraction and fractional shortening were decreased compared to baseline, but showed no differences between groups. On day 14, a dose-dependent increase in left ventricular end diastolic diameter was seen (p<0.001). CsA pretreatment was associated with a dose-dependent decrease in post-I/R-survival (vehicle: 56%, CsA-5mg/kg/day: 32%, CsA-12.5mg/kg/day: 16%; p=0.017). CsA pretreatment did not improve long-term cardiac function despite decreased infarct size 24h after I/R-injury, but increased post-I/R mortality significantly. Poor cardiac function after CsA pretreatment might be caused by left ventricular dilation.

1H-NMR metabolic profiling of human neonatal urine

OBJECT

The measurement of different urine components and their changes over time may provide comprehensive and early information about perinatal metabolic processes and physiological changes. We hypothesized that (1) H-NMR-spectroscopy generating a complex spectral profile without pre-selection of urinary metabolites could identify metabolites determining the neonatal physiological status and discriminating between different metabolic states.

MATERIALS AND METHODS

We studied spot urine of three groups of neonates (healthy term-born, term-born with non-specific bacterial infections, and preterm neonates) for the first 6 days of life using (1) H-NMR-spectroscopy. In the group of healthy neonates metabolites changing were identified and their excretion patterns compared between groups.

RESULTS

Six metabolites indicating physiological changes were identified: N-methylnicotinamide (NAD (+)-pathway), formate, hippurate, betaine (kidney development), taurine (neuronal development), and bile acids (hepatic clearance). While the dynamic changes over the first 6 days were the same for all metabolites in both groups of term-born neonates, the excretion of N-methylnicotinamide and taurine was significantly higher in preterm neonates compared to healthy term neonates and neonates with bacterial infections from the third day after birth (P < 0.05).

CONCLUSION

Urine analysis using (1) H-NMR-spectroscopy could identify markers for perinatal metabolic changes. Further studies have to clarify if the proposed physiological interpretation will correlate with long-term physiological development.