SARS-CoV-2 neutralizing antibodies in Chile after a vaccination campaign with five different schemes (preprint)

Using levels of neutralizing antibodies (nAbs), we evaluate the successful Chilean SARS-CoV-2 vaccine campaign, which combines technologies and heterologous boosters. In 120 randomly selected seropositive individuals from a population-based study, we conclude that the booster dose, regardless of vaccine technology or natural infection, and mRNA vaccines significantly improve nAbs response.

Multicenter analysis of neutrophil extracellular trap dysregulation in adult and pediatric COVID-19 (preprint)

Dysregulation in neutrophil extracellular trap (NET) formation and degradation may play a role in the pathogenesis and severity of COVID-19; however, its role in the pediatric manifestations of this disease including MIS-C and chilblain-like lesions (CLL), otherwise known as "COVID toes", remains unclear. Studying multinational cohorts, we found that, in CLL, NETs were significantly increased in serum and skin. There was geographic variability in the prevalence of increased NETs in MIS-C, in association with disease severity. MIS-C and CLL serum samples displayed decreased NET degradation ability, in association with C1q and G-actin or anti-NET antibodies, respectively, but not with genetic variants of DNases. In adult COVID-19, persistent elevations in NETs post-disease diagnosis were detected but did not occur in asymptomatic infection. COVID-19-affected adults displayed significant prevalence of impaired NET degradation, in association with anti-DNase1L3, G-actin, and specific disease manifestations, but not with genetic variants of DNases. NETs were detected in many organs of adult patients who died from COVID-19 complications. Infection with the Omicron variant was associated with decreased levels of NETs when compared to other SARS-CoV-2 strains. These data support a role for NETs in the pathogenesis and severity of COVID-19 in pediatric and adult patients. SummaryNET formation and degradation are dysregulated in pediatric and symptomatic adult patients with various complications of COVID-19, in association with disease severity. NET degradation impairments are multifactorial and associated with natural inhibitors of DNase 1, G-actin and anti-DNase1L3 and anti-NET antibodies. Infection with the Omicron variant is associated with decreased levels of NETs when compared to other SARS-CoV-2 strains.

Autoantibodies Detected in MIS-C Patients due to Administration of Intravenous Immunoglobulin (preprint)

The autoantibody profile associated with known autoimmune diseases in patients with COVID-19 or multisystem inflammatory syndrome in children (MIS-C) remains poorly defined. Here we show that adults with COVID-19 had a moderate prevalence of autoantibodies against the lung antigen KCNRG, and SLE-associated Smith autoantigen. Children with COVID-19 rarely had autoantibodies; one of 59 children had GAD65 autoantibodies associated with acute insulin-dependent diabetes. While autoantibodies associated with SLE/Sjogren syndrome (Ro52, Ro60, and La) and/or autoimmune gastritis (gastric ATPase) were detected in 74% (40/54) of MIS-C patients, further analysis of these patients and of children with Kawasaki disease (KD), showed that the administration of intravenous immunoglobulin (IVIG) was largely responsible for detection of these autoantibodies in both groups of patients. Monitoring in vivo decay of the autoantibodies in MIS-C children showed that the IVIG-derived Ro52, Ro60, and La autoantibodies declined to undetectable levels by 45-60 days, but gastric ATPase autoantibodies declined more slowly requiring >100 days until undetectable. Together these findings demonstrate that administration of high-dose IVIG is responsible for the detection of several autoantibodies in MIS-C and KD. Further studies are needed to investigate autoantibody production in MIS-C patients, independently from IVIG administration.

Multi-omics approach identifies novel age-, time- and treatment-related immunopathological signatures in MIS-C and pediatric COVID-19 (preprint)

Pediatric COVID-19 (pCOVID-19) is rarely severe, however a minority of SARS-CoV-2-infected children may develop MIS-C, a multisystem inflammatory syndrome with significant morbidity. In this longitudinal multi-institutional study, we used multi-omics to identify novel time- and treatment-related immunopathological signatures in children with COVID-19 (n=105) and MIS-C (n=76). pCOVID-19 was characterized by enhanced type I IFN responses, and MIS-C by type II IFN- and NF-{kappa}B dependent responses, matrisome activation, and increased levels of Spike protein. Reduced levels of IL-33 in pCOVID-19, and of CCL22 in MIS-C suggested suppression of Th2 responses. Expansion of TRBV11-2 T-cell clonotypes in MIS-C was associated with inflammation and signatures of T-cell activation, and was reversed by glucocorticoids. The association of MIS-C with the combination of HLA A*02, B*35, C*04 alleles suggests genetic susceptibility. MIS-C B cells showed higher mutation load. Use of IVIG was identified as a confounding factor in the interpretation of autoantibody levels.

An international, inter-laboratory ring trial confirms the feasibility of an open source, extraction-less "direct" RT-qPCR method for reliable detection of SARS-CoV-2 RNA in clinical samples (preprint)

RT-qPCR is used world-wide to test and trace the spread of SARS-CoV-2. Extraction-less or direct RT-PCR is an open-access qualitative method for SARS-CoV-2 detection from nasopharyngeal (NP) or oral pharyngeal (OP) samples with the potential to generate actionable data more quickly, at a lower cost, and with fewer experimental resources than full RT-qPCR. This study engaged ten global testing sites, including laboratories currently experiencing testing limitations due to reagent or equipment shortages, in an international inter-laboratory ring trial. Participating labs were provided a common protocol, common reagents, aliquots of identical pooled clinical samples and purified nucleic acids, and used their existing in-house equipment. We observed 100% concordance across labs in the correct identification of all positive and negative samples, with highly similar Ct values observed. The test also performed well when applied to locally collected patient NP samples, provided the viral transport media did not contain charcoal or guanidine, both of which appeared to potently inhibit the RT-PCR reaction. Our results suggest that open access, direct RT-PCR assays are a feasible option for more efficient COVID-19 testing as demanded by the continuing pandemic.