Bacteria-specific neutrophil dysfunction associated with interferon-stimulated gene expression in the acute respiratory distress syndrome

Distribution of Interferon Lambda 4 Single Nucleotide Polymorphism rs11322783 Genotypes in Patients with COVID-19

Type III interferons (IFN-III), also known as IFN-Lambda, have a pivotal role during SARS-CoV-2 infection. IFN-Lambda response among individuals is heterogeneous and its association with COVID-19 symptoms severity needs to be further clarified. We analyzed the genotype frequencies of IFNL4 single nucleotide polymorphism (SNP) rs11322783 in patients with COVID-19 (n = 128), in comparison with a validated data set of European healthy controls (n = 14152). The IFNL4 SNP was also analyzed according to the haematological and clinical parameters of patients with COVID-19. The distributions of IFNL4 genotypes among SARS-CoV-2 positive patients [TT/TT 41.4% (n = 53), TT/ΔG 47.7% (n = 61) and ΔG/ΔG 10.9% (n = 14)] and healthy controls were comparable. Different levels of white blood cells (p = 0.036) and neutrophils (p = 0.042) were found in the IFNL4 different genotypes in patients with COVID-19; the ΔG/ΔG genotype was more represented in the groups with low white blood cells and neutrophils. There were no differences in major inflammation parameters (C-reactive protein, D-dimer, Albumin, and Lactate-dehydrogenase (LDH)] and survival rate according to the IFNL4 genotypes. In conclusion, although patients with COVID-19 did not exhibit a different distribution of the IFNL4 SNP, the ΔG/ΔG genotype was associated with a lower count of immune cell populations. These findings need to be confirmed in larger groups of patients with COVID-19 and the role of IFNL4 SNP needs to be also investigated in other respiratory viral infections.

Differential type I interferon response and primary airway neutrophil extracellular trap release in children with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a heterogeneous condition characterized by the recruitment of large numbers of neutrophils into the lungs. Neutrophils isolated from the blood of adults with ARDS have elevated expression of interferon (IFN) stimulated genes (ISGs) associated with decreased capacity of neutrophils to kill Staphylococcus aureus and worse clinical outcomes. Neutrophil extracellular traps (NETs) are elevated in adults with ARDS. Whether pediatric ARDS (PARDS) is similarly associated with altered neutrophil expression of ISGs and neutrophil extracellular trap release is not known. Tracheal aspirate fluid and cells were collected within 72 h from seventy-seven intubated children. Primary airway neutrophils were analyzed for differential ISG expression by PCR, STAT1 phosphorylation and markers of degranulation and activation by flow cytometry. Airway fluid was analyzed for the release of NETs by myeloperoxidase-DNA complexes using an ELISA. Higher STAT1 phosphorylation, markers of neutrophil degranulation, activation and NET release were found in children with versus without PARDS. Higher NETs were detected in the airways of children with ventilator-free days less than 20 days. Increased airway cell IFN signaling, neutrophil activation, and NET production is associated with PARDS. Higher levels of airway NETs are associated with fewer ventilator-free days.

TLR4/NF-κB signaling pathway gene single nucleotide polymorphisms alter gene expression levels and affect ARDS occurrence and prognosis outcomes

BACKGROUND

To study the occurrence and prognosis of acute respiratory distress syndrome (ARDS) using single nucleotide polymorphisms (SNPs) of TNF-α rs1800629, IL-6 rs1800796, and MyD88 rs7744 loci in the TLR4/NF-κB pathway.

METHODS

Genotypes were analyzed for TNF-α rs1800629, IL-6 rs1800796, and MyD88 rs7744 loci. Plasma TNF-α and IL-6 levels and MyD88 mRNA expression in peripheral blood mononuclear cells (PBMCs) of 300 ARDS patients and 300 non-ARDS patients (control group) were examined. The patients were followed up for 60 days, and the prognosis outcome was recorded.

RESULTS

The TNF-α rs1800629 locus A allele and the IL-6 rs1800796 locus G allele were found to be risk factors for ARDS (adjusted OR = 1.452, 95% CI: 1.211-1.689, P < .001 and adjusted OR = 1.205, 95% CI: 1.058-1.358, P = .005, respectively). The G allele at MyD88 rs7744 locus was a protective factor against ARDS (adjusted OR = 0.748, 95% CI: 0.631-0.876, P < .001). Compared with the other groups, homozygotes for TNF-α rs1800629, IL-6 rs1800796, and MyD88 rs7744 loci had higher expression levels, of which homozygotes for TNF-α rs1800629 and IL-6 rs1800796 loci had lower 60-day survival rates, while MyD88 rs7744 locus homozygotes had a higher 60-day survival rate.

CONCLUSION

The effect of TNF-α rs1800629, IL-6 rs1800796, and MyD88 rs7744 SNPs on gene expression level is a likely cause of ARDS occurrence and poor prognosis.

Alternative pre-mRNA splicing of Toll-like receptor signaling components in peripheral blood mononuclear cells from patients with ARDS

A key physiological feature of acute respiratory distress syndrome (ARDS) is inflammation. Toll-like receptor (TLR) signaling is required to combat the infection that underlies many ARDS cases but also contributes to pathological inflammation. Several TLR signaling pathway genes encoding positive effectors of inflammation also produce alternatively spliced mRNAs encoding negative regulators of inflammation. An imbalance between these isoforms could contribute to pathological inflammation and disease severity. To determine whether splicing in TLR pathways is altered in patients with ARDS, we monitored alternative splicing of MyD88 and IRAK1, two genes that function in multiple TLR pathways. The MyD88 and IRAK1 genes produce long proinflammatory mRNAs (MyD88_L and IRAK1) and shorter anti-inflammatory mRNAs (MyD88_S and IRAK1c). We quantified mRNA encoding inflammatory cytokines and MyD88 and IRAK1 isoforms in peripheral blood mononuclear cells (PBMCs) from 104 patients with ARDS and 30 healthy control subjects. We found that MyD88 pre-mRNA splicing is altered in patients with ARDS in a proinflammatory direction. We also observed altered MyD88 isoform levels in a second critically ill patient cohort, suggesting that these changes may not be unique to ARDS. Early in ARDS, PBMC IRAK1c levels were associated with patient survival. Despite the similarities in MyD88 and IRAK1 alternative splicing observed in previous in vitro studies, there were differences in how MyD88 and IRAK1 alternative splicing was altered in patients with ARDS. We conclude that pre-mRNA splicing of TLR signaling genes is altered in patients with ARDS, and further investigation of altered splicing may lead to novel prognostic and therapeutic approaches.

Extremes of Interferon-Stimulated Gene Expression Associate with Worse Outcomes in the Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) severity may be influenced by heterogeneity of neutrophil activation. Interferon-stimulated genes (ISG) are a broad gene family induced by Type I interferons, often as a response to viral infections, which evokes extensive immunomodulation. We tested the hypothesis that over- or under-expression of immunomodulatory ISG by neutrophils is associated with worse clinical outcomes in patients with ARDS. Genome-wide transcriptional profiles of circulating neutrophils isolated from patients with sepsis-induced ARDS (n = 31) and healthy controls (n = 19) were used to characterize ISG expression. Hierarchical clustering of expression identified 3 distinct subject groups with Low, Mid and High ISG expression. ISG accounting for the greatest variability in expression were identified (MX1, IFIT1, and ISG15) and used to analyze a prospective cohort at the Colorado ARDS Network site. One hundred twenty ARDS patients from four urban hospitals were enrolled within 72 hours of initiation of mechanical ventilation. Circulating neutrophils were isolated from patients and expression of ISG determined by PCR. Samples were stratified by standard deviation from the mean into High (n = 21), Mid, (n = 82) or Low (n = 17) ISG expression. Clinical outcomes were compared between patients with High or Low ISG expression to those with Mid-range expression. At enrollment, there were no differences in age, gender, co-existing medical conditions, or type of physiologic injury between cohorts. After adjusting for age, race, gender and BMI, patients with either High or Low ISG expression had significantly worse clinical outcomes than those in the Mid for number of 28-day ventilator- and ICU-free days (P = 0.0006 and 0.0004), as well as 90-day mortality and 90-day home with unassisted breathing (P = 0.02 and 0.004). These findings suggest extremes of ISG expression by circulating neutrophils from ARDS patients recovered early in the syndrome are associated with poorer clinical outcomes.

The effectiveness of Corticosteroids on mortality in patients with acute respiratory distress syndrome or acute lung injury: a secondary analysis

The development of acute respiratory distress syndrome (ARDS) is associated with dys-regulated inflammation. Since corticosteroids are potent anti-inflammatory drugs, they are thought to be beneficial for ARDS patients. The study aimed to investigate the effectiveness of corticosteroids on mortality outcome in ARDS patients. The study was a secondary analysis of a prospective randomized controlled trial (NCT00979121). ARDS patients with invasive mechanical ventilation were enrolled. Corticosteroids use was defined as IV or PO administration of corticosteroids totaling more than 20 mg methylprednisolone equivalents during one calendar day. Missing data were handled using multiple imputation technique. Multivariable model was built to adjust for confounding covariates. A total of 745 patients were enrolled, including 540 survivors and 205 non-survivors. Patients in the non-survivor group were more likely to use corticosteroids (38% vs. 29.8%; p = 0.032). After adjustment for other potential confounders, corticosteroids showed no statistically significant effect on mortality outcome (OR: 1.18; 95% CI: 0.81-1.71). Furthermore, we investigated the interaction between corticosteroid use and variables of vasopressor and PaO2. The result showed that there was no significant interaction. In conclusion, the study failed to identify any beneficial effects of corticosteroids on mortality outcome in patients with ARDS.

Molecular pathology of emerging coronavirus infections

Respiratory viruses can cause a wide spectrum of pulmonary diseases, ranging from mild, upper respiratory tract infections to severe and life-threatening lower respiratory tract infections, including the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Viral clearance and subsequent recovery from infection require activation of an effective host immune response; however, many immune effector cells may also cause injury to host tissues. Severe acute respiratory syndrome (SARS) coronavirus and Middle East respiratory syndrome (MERS) coronavirus cause severe infection of the lower respiratory tract, with 10% and 35% overall mortality rates, respectively; however, >50% mortality rates are seen in the aged and immunosuppressed populations. While these viruses are susceptible to interferon treatment in vitro, they both encode numerous genes that allow for successful evasion of the host immune system until after high virus titres have been achieved. In this review, we discuss the importance of the innate immune response and the development of lung pathology following human coronavirus infection.

Mycobacterium abscessus induces a limited pattern of neutrophil activation that promotes pathogen survival

Mycobacterium abscessus is a rapidly growing mycobacterium increasingly detected in the neutrophil-rich environment of inflamed tissues, including the cystic fibrosis airway. Studies of the immune reaction to M. abscessus have focused primarily on macrophages and epithelial cells, but little is known regarding the neutrophil response despite the predominantly neutrophillic inflammation typical of these infections. In the current study, human neutrophils released less superoxide anion in response to M. abscessus than to Staphylococcus aureus, a pathogen that shares common sites of infection. Exposure to M. abscessus induced neutrophil-specific chemokine and proinflammatory cytokine genes. Although secretion of these protein products was confirmed, the quantity of cytokines released, and both the number and level of gene induction, was reduced compared to S. aureus. Neutrophils mediated killing of M. abscessus, but phagocytosis was reduced when compared to S. aureus, and extracellular DNA was detected in response to both bacteria, consistent with extracellular trap formation. In addition, M. abscessus did not alter cell death compared to unstimulated cells, while S. aureus enhanced necrosis and inhibited apoptosis. However, neutrophils augment M. abscessus biofilm formation. The response of neutrophils to M. abscessus suggests that the mycobacterium exploits neutrophil-rich settings to promote its survival and that the overall neutrophil response was reduced compared to S. aureus. These studies add to our understanding of M. abscessus virulence and suggest potential targets of therapy.

A double-inactivated severe acute respiratory syndrome coronavirus vaccine provides incomplete protection in mice and induces increased eosinophilic proinflammatory pulmonary response upon challenge

Severe acute respiratory syndrome coronavirus (SARS-CoV) is an important emerging virus that is highly pathogenic in aged populations and is maintained with great diversity in zoonotic reservoirs. While a variety of vaccine platforms have shown efficacy in young-animal models and against homologous viral strains, vaccine efficacy has not been thoroughly evaluated using highly pathogenic variants that replicate the acute end stage lung disease phenotypes seen during the human epidemic. Using an adjuvanted and an unadjuvanted double-inactivated SARS-CoV (DIV) vaccine, we demonstrate an eosinophilic immunopathology in aged mice comparable to that seen in mice immunized with the SARS nucleocapsid protein, and poor protection against a nonlethal heterologous challenge. In young and 1-year-old animals, we demonstrate that adjuvanted DIV vaccine provides protection against lethal disease in young animals following homologous and heterologous challenge, although enhanced immune pathology and eosinophilia are evident following heterologous challenge. In the absence of alum, DIV vaccine performed poorly in young animals challenged with lethal homologous or heterologous strains. In contrast, DIV vaccines (both adjuvanted and unadjuvanted) performed poorly in aged-animal models. Importantly, aged animals displayed increased eosinophilic immune pathology in the lungs and were not protected against significant virus replication. These data raise significant concerns regarding DIV vaccine safety and highlight the need for additional studies of the molecular mechanisms governing DIV-induced eosinophilia and vaccine failure, especially in the more vulnerable aged-animal models of human disease.