Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

BACKGROUND

We previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15-20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in ~ 80% of cases.

METHODS

We report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded.

RESULTS

No gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5-528.7, P = 1.1 × 10-4) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR = 3.70[95%CI 1.3-8.2], P = 2.1 × 10-4). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR = 19.65[95%CI 2.1-2635.4], P = 3.4 × 10-3), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR = 4.40[9%CI 2.3-8.4], P = 7.7 × 10-8). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD] = 43.3 [20.3] years) than the other patients (56.0 [17.3] years; P = 1.68 × 10-5).

CONCLUSIONS

Rare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old.

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

Background

We previously reported inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity in 1-5% of unvaccinated patients with life-threatening COVID-19, and auto-antibodies against type I IFN in another 15-20% of cases.

Methods

We report here a genome-wide rare variant burden association analysis in 3,269 unvaccinated patients with life-threatening COVID-19 (1,301 previously reported and 1,968 new patients), and 1,373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. A quarter of the patients tested had antibodies against type I IFN (234 of 928) and were excluded from the analysis.

Results

No gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7 , with an OR of 27.68 (95%CI:1.5-528.7, P= 1.1×10 -4 ), in analyses restricted to biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70 [95%CI:1.3-8.2], P= 2.1×10 -4 ). Adding the recently reported TYK2 COVID-19 locus strengthened this enrichment, particularly under a recessive model (OR=19.65 [95%CI:2.1-2635.4]; P= 3.4×10 -3 ). When these 14 loci and TLR7 were considered, all individuals hemizygous ( n =20) or homozygous ( n =5) for pLOF or bLOF variants were patients (OR=39.19 [95%CI:5.2-5037.0], P =4.7×10 -7 ), who also showed an enrichment in heterozygous variants (OR=2.36 [95%CI:1.0-5.9], P =0.02). Finally, the patients with pLOF or bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P= 1.68×10 -5 ).

Conclusions

Rare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old.

A randomised trial of high-flow nasal cannula in infants with moderate bronchiolitis

BACKGROUND

The objective was to determine whether high-flow nasal cannula (HFNC), a promising respiratory support in infant bronchiolitis, could reduce the proportion of treatment failure requiring escalation of care.

METHODS

In this randomised controlled trial, we assigned infants aged <6 months who had moderate bronchiolitis to receive either HFNC at 3 L·kg^-1·min^-1 or standard oxygen therapy. Crossover was not allowed. The primary outcome was the proportion of patients in treatment failure requiring escalation of care (mostly noninvasive ventilation) within 7 days following randomisation. Secondary outcomes included rates of transfer to the paediatric intensive care unit (PICU), oxygen, number of artificial nutritional support-free days and adverse events.

RESULTS

The analyses included 268 patients among the 2621 infants assessed for inclusion during two consecutive seasons in 17 French paediatric emergency departments. The percentage of infants in treatment failure was 14% (19 out of 133) in the study group, compared to 20% (27 out of 135) in the control group (OR 0.66, 95% CI 0.35-1.26; p=0.21). HFNC did not reduce the risk of admission to PICU (21 (15%) out of 133 in the study group versus 26 (19%) out of 135 in the control group) (OR 0.78, 95% CI 0.41-1.41; p=0.45). The main reason for treatment failure was the worsening of modified Wood clinical asthma score (m-WCAS). Short-term assessment of respiratory status showed a significant difference for m-WCAS and respiratory rate in favour of HFNC. Three pneumothoraces were reported in the study group.

CONCLUSIONS

In patients with moderate bronchiolitis, there was no evidence of lower rate of escalating respiratory support among those receiving HFNC therapy.

Increased prevalence of overweight and obesity in children with X-linked hypophosphatemia

BACKGROUND/AIM

X-linked hypophosphatemia (XLH) is a rare disease characterized by low phosphate levels. Scientific evidence points to a link between hypophosphatemia and obesity in general population. The aim of our longitudinal observational study was to investigate the prevalence of obesity and associated factors in a large cohort of children with XLH.

PATIENTS/METHODS

We studied 172 XLH-children 5-20 years of age (113 girls/59 boys). Anthropometric parameters (weight, height, and BMI) were collected at birth and during follow-up at mean ages of 5.3, 8.2, 11.3, and 15.9 years (groups 1, 2, 3, and 4, respectively). In each group, subjects were classified based on International Obesity Taskforce (IOTF) cut off values of BMI for age and sex as overweight or obese (IOTF 25-30 or ≥30 kg/m2, respectively).

RESULTS

In each age-group, almost 1/3 of XLH-patients were classified as overweight or obese (29.4, 28.7, 27.5, and 36.7% in groups 1, 2, 3, and 4, respectively). Children without a XLH-family history had higher BMI-IOTF at every point of follow-up, compared to those with positive XLH-family history. Similarly, higher BMI-IOTF was significantly associated with treatment duration (23.3 ± 4.4 vs 23.8 ± 3.8 vs 25.2 ± 4.5 kg/m2, for subjects with treatment duration of <5, 5-10 and >10 years, respectively, P for trend = 0.025). Multiple regression analysis confirmed an association of treatment duration and lack of XLH-family history with higher BMI-IOTF.

CONCLUSION

One out of three of XLH-children have phenotypically unfavourable metabolic profile expressed as increased prevalence of overweight or obesity in comparison to general population. Both the lack of XLH family history and the duration of treatment increase the risk of higher BMI-IOTF. BMI should be carefully monitored in children, and later in adults, with XLH.

SAT-259 Natural History of Anthropometric Parametres of Obesity in Children Affected by X-Linked Hypophosphatemia: Longitudinal Obserbational Study

Growing body of scientific evidence points to link between fibroblast growth factor-23 (FGF-23) and unfavourable metabolic profile (obesity, insulin resistance, hyperglycemia) and all-cause mortality in general population with normal kidney function. On the other hand, there is little information about metabolic profile in situations characterized by pathophysiologically high FGF-23 such as chronic kidney disease and X-linked hypophosphatemia (XLH). The aim of the present longitudinal observational study was to investigate anthropometric parameters of obesity and metabolic profile on large cohort of children with XLH. Methods: Among 263 XLH-patients registered in our centre we selected 168 children of 5-20 years (108 girls/60 boys). Total period of FU was divided in five sub-periods according age (group 0: birth, N=168; group 1: 5-7 years, N=122; group 2: 7-10 years, N=86; group 3: 10-15 years, N=89; group 4: 15-20 years, N=49). Anthropometric parameters (weight, height, BMI) were collected from birth (group 0) and for every point of FU (group 1-4). In each group, subjects were classified based on International Obesity Taskforce (IOTF) cut off values of BMI for age and sex as overweight or obese (IOTF 25-30 or ≥30 kg/m2, respectively). Metabolic parameters (total cholesterol, triglycerides, HDL, LDL, fasting glycemia and insulinemia, HOMA-IR) were measured at one point of FU in some patients (N=40). Results: In each group of FU (1,2,3,4) almost 1/3 of patients were classified as overweight or obese (29.5% vs 29.4% vs 28.1% vs 36.7%, respectively). Even without reaching statistical significance (p=0.75), there was a tendency of higher number of overweight or obese patients in group 4 (15-20 years) (36.7%) compared to group 1,2,3, which was explained by gender differences (higher number of overweight or obese girls compared to boys (42.4% vs 25%, respectively, p=0.35). There were no differences in BMI z-score (SDS) and BMI-IOTF between groups 1,2,3,4 during FU (BMI-SDS: 0.9±1.1 vs 0.7±1.0 vs 0.6±1.1 vs 0.6±0.9, respectively, p=0.45; BMI-IOTF: 23.5±4.4 vs 23.5±4.1 vs 23.7±4.2 vs 24.3±3.6, respectively, p=0.72). As regard other metabolic parameters, only 1 patient was diagnosed with diabetes mellitus at age 10. No other alterations were found. In each group of FU, no correlation was found between FGF-23 and BMI, total cholesterol, triglycerides, HDL, LDL, fasting glycemia, insulinemia, HOMA-IR. In conclusion, 1/3 of XLH children have phenotypically unfavourable metabolic profile expressed as overweight or obesity which is higher compared to general paediatric population. This phenomenon has increasing tendency after puberty, especially in girls, and requires strict follow-up of BMI in XLH patients. In order to understand the further development of metabolic parameters, the studies on adult XLH population are needed.