Soluble Signal Inhibitory Receptor on Leukocytes-1 Is Released from Activated Neutrophils by Proteinase 3 Cleavage

Signal inhibitory receptor on leukocytes-1 (SIRL-1) is an immune inhibitory receptor expressed on human granulocytes and monocytes that dampens antimicrobial functions. We previously showed that sputum neutrophils from infants with severe respiratory syncytial virus (RSV) bronchiolitis have decreased SIRL-1 surface expression compared with blood neutrophils and that SIRL-1 surface expression is rapidly lost from in vitro activated neutrophils. This led us to hypothesize that activated neutrophils lose SIRL-1 by ectodomain shedding. Here, we developed an ELISA and measured the concentration of soluble SIRL-1 (sSIRL-1) in patients with RSV bronchiolitis and hospitalized patients with COVID-19, which are both characterized by neutrophilic inflammation. In line with our hypothesis, sSIRL-1 concentration was increased in sputum compared with plasma of patients with RSV bronchiolitis and in serum of hospitalized patients with COVID-19 compared with control serum. In addition, we show that in vitro activated neutrophils release sSIRL-1 by proteolytic cleavage and that this diminishes the ability to inhibit neutrophilic reactive oxygen species production via SIRL-1. Finally, we found that SIRL-1 shedding is prevented by proteinase 3 inhibition and by extracellular adherence protein from Staphylococcus aureus. Notably, we recently showed that SIRL-1 is activated by PSMα3 from S. aureus, suggesting that S. aureus may counteract SIRL-1 shedding to benefit from preserved inhibitory function of SIRL-1. In conclusion, we report that SIRL-1 is released from activated neutrophils by proteinase 3 cleavage and that endogenous sSIRL-1 protein is present in vivo.

Genome-wide association studies of exacerbations in children using long-acting beta2-agonists

BACKGROUND

Some children with asthma experience exacerbations despite long-acting beta2-agonist (LABA) treatment. While this variability is partly caused by genetic variation, no genome-wide study until now has investigated which genetic factors associated with risk of exacerbations despite LABA use in children with asthma. We aimed to assess whether genetic variation was associated with exacerbations in children treated with LABA from a global consortium.

METHODS

A meta-analysis of genome-wide association studies (meta-GWAS) was performed in 1,425 children and young adults with asthma (age 6-21 years) with reported regular use of LABA from six studies within the PiCA consortium using a random effects model. The primary outcome of each study was defined as any exacerbation within the past 6 or 12 months, including at least one of the following: 1) hospital admissions for asthma, 2) a course of oral corticosteroids or 3) emergency room visits because of asthma.

RESULTS

Genome-wide association results for a total of 82 996 common single nucleotide polymorphisms (SNPs, MAF ≥1%) with high imputation quality were meta-analysed. Eight independent variants were suggestively (P-value threshold ≤5 × 10^-6 ) associated with exacerbations despite LABA use.

CONCLUSION

No strong effects of single nucleotide polymorphisms (SNPs) on exacerbations during LABA use were identified. We identified two loci (TBX3 and EPHA7) that were previously implicated in the response to short-acting beta2-agonists (SABA). These loci merit further investigation in response to LABA and SABA use.

Infection of human Nasal Epithelial Cells with SARS-CoV-2 and a 382-nt deletion isolate lacking ORF8 reveals similar viral kinetics and host transcriptional profiles

The novel coronavirus SARS-CoV-2 is the causative agent of Coronavirus Disease 2019 (COVID-19), a global healthcare and economic catastrophe. Understanding of the host immune response to SARS-CoV-2 is still in its infancy. A 382-nt deletion strain lacking ORF8 (Δ382 herein) was isolated in Singapore in March 2020. Infection with Δ382 was associated with less severe disease in patients, compared to infection with wild-type SARS-CoV-2. Here, we established Nasal Epithelial cells (NECs) differentiated from healthy nasal-tissue derived stem cells as a suitable model for the ex-vivo study of SARS-CoV-2 mediated pathogenesis. Infection of NECs with either SARS-CoV-2 or Δ382 resulted in virus particles released exclusively from the apical side, with similar replication kinetics. Screening of a panel of 49 cytokines for basolateral secretion from infected NECs identified CXCL10 as the only cytokine significantly induced upon infection, at comparable levels in both wild-type and Δ382 infected cells. Transcriptome analysis revealed the temporal up-regulation of distinct gene subsets during infection, with anti-viral signaling pathways only detected at late time-points (72 hours post-infection, hpi). This immune response to SARS-CoV-2 was significantly attenuated when compared to infection with an influenza strain, H3N2, which elicited an inflammatory response within 8 hpi, and a greater magnitude of anti-viral gene up-regulation at late time-points. Remarkably, Δ382 induced a host transcriptional response nearly identical to that of wild-type SARS-CoV-2 at every post-infection time-point examined. In accordance with previous results, Δ382 infected cells showed an absence of transcripts mapping to ORF8, and conserved expression of other SARS-CoV-2 genes. Our findings shed light on the airway epithelial response to SARS-CoV-2 infection, and demonstrate a non-essential role for ORF8 in modulating host gene expression and cytokine production from infected cells.

Rationale and design of the multiethnic Pharmacogenomics in Childhood Asthma consortium

AIM

International collaboration is needed to enable large-scale pharmacogenomics studies in childhood asthma. Here, we describe the design of the Pharmacogenomics in Childhood Asthma (PiCA) consortium.

MATERIALS & METHODS

Investigators of each study participating in PiCA provided data on the study characteristics by answering an online questionnaire.

RESULTS

A total of 21 studies, including 14,227 children/young persons (58% male), from 12 different countries are currently enrolled in the PiCA consortium. Fifty six percent of the patients are Caucasians. In total, 7619 were inhaled corticosteroid users. Among patients from 13 studies with available data on asthma exacerbations, a third reported exacerbations despite inhaled corticosteroid use. In the future pharmacogenomics studies within the consortium, the pharmacogenomics analyses will be performed separately in each center and the results will be meta-analyzed.

CONCLUSION

PiCA is a valuable platform to perform pharmacogenetics studies within a multiethnic pediatric asthma population.

Virus infection drives IL-2 antibody complexes into pro-inflammatory agonists in mice

The use of IL-2/JES6-1 Ab complex (IL-2 Ab Cx) has been considered as a potential therapeutic for inflammatory diseases due to its selective expansion of regulatory T cells (Tregs) in mice. Here, IL-2 Ab Cx was explored as a therapeutic agent to reduce joint inflammation induced by chikungunya virus, an alphavirus causing debilitating joint disease globally. Virus-infected mice treated with IL-2 Ab Cx exhibited exacerbated joint inflammation due to infiltration of highly activated CD4⁺ effector T cells (Teffs). Virus infection led to upregulation of CD25 on the Teffs, rendering them sensitive towards IL2 Ab Cx. Ready responsiveness of Teffs to IL-2 was further demonstrated in healthy human donors, suggesting that the use of IL-2 Ab Cx in humans is not suitable. Changes in IL-2 sensitivity during active virus infection could change the responsive pattern towards the IL-2 Ab Cx, resulting in the expansion of pro-inflammatory rather than anti-inflammatory responses.

Loss of TLR3 aggravates CHIKV replication and pathology due to an altered virus-specific neutralizing antibody response

RNA-sensing toll-like receptors (TLRs) mediate innate immunity and regulate anti-viral response. We show here that TLR3 regulates host immunity and the loss of TLR3 aggravates pathology in Chikungunya virus (CHIKV) infection. Susceptibility to CHIKV infection is markedly increased in human and mouse fibroblasts with defective TLR3 signaling. Up to 100-fold increase in CHIKV load was observed in Tlr3^−/− mice, alongside increased virus dissemination and pro-inflammatory myeloid cells infiltration. Infection in bone marrow chimeric mice showed that TLR3-expressing hematopoietic cells are required for effective CHIKV clearance. CHIKV-specific antibodies from Tlr3^−/− mice exhibited significantly lower in vitro neutralization capacity, due to altered virus-neutralizing epitope specificity. Finally, SNP genotyping analysis of CHIKF patients on TLR3 identified SNP rs6552950 to be associated with disease severity and CHIKV-specific neutralizing antibody response. These results demonstrate a key role for TLR3-mediated antibody response to CHIKV infection, virus replication and pathology, providing a basis for future development of immunotherapeutics in vaccine development.