Differential interferon gene expression in bronchiolitis caused by respiratory syncytial virus-A genotype ON1

Differences Between RSV A and RSV B Subgroups and Implications for Pharmaceutical Preventive Measures

INTRODUCTION

Understanding the differences between respiratory syncytial virus (RSV) subgroups A and B provides insights for the development of prevention strategies and public health interventions. We aimed to describe the structural differences of RSV subgroups, their epidemiology, and genomic diversity. The associated immune response and differences in clinical severity were also investigated.

METHODS

A literature review from PubMed and Google Scholar (1985-2023) was performed and extended using snowballing from references in captured publications.

RESULTS

RSV has two major antigenic subgroups, A and B, defined by the G glycoprotein. The RSV F fusion glycoprotein in the prefusion conformation is a major target of virus neutralizing antibodies and differs in surface exposed regions between RSV A and RSV B. The subgroups co-circulate annually, but there is considerable debate as to whether clinical severity is impacted by the subgroup of the infecting RSV strain. Large variations between the studies reporting RSV subgroup impact on clinical severity were observed. A tendency for higher disease severity may be attributed to RSV A but no consensus could be reached as to whether infection by one of the subgroup caused more severe outcomes. RSV genotype diversity decreased over the last two decades, and ON and BA have become the sole lineages detected for RSV A and RSV B, since 2014. No studies with data obtained after 2014 reported a difference in disease severity between the two subgroups. RSV F is relatively well conserved and highly similar between RSV A and B, but changes in the amino acid sequence have been observed. Some of these changes led to differences in F antigenic sites compared to reference F sequences (e.g., RSV/A Long strain), which are more pronounced in antigenic sites of the prefusion conformation of RSV B. Initial results from the second season after vaccination suggest specific RSV B efficacy wanes more rapidly than RSV A for RSV PreF-based monovalent vaccines.

CONCLUSIONS

RSV A and RSV B both contribute substantially to the global RSV burden. Both RSV subgroups cause severe disease and none of the available evidence to date suggests any differences in clinical severity between the subgroups. Therefore, it is important to implement measures effective at preventing disease due to both RSV A and RSV B to ensure impactful public health interventions. Monitoring overtime will be needed to assess the impact of waning antibody levels on subgroup-specific efficacy.

NRF2 Antioxidant Response and Interferon-Stimulated Genes Are Differentially Expressed in Respiratory-Syncytial-Virus- and Rhinovirus-Infected Hospitalized Children

Respiratory diseases caused by respiratory syncytial virus (RSV) and human rhinovirus (HRV) are frequent causes of the hospitalization of children; nonetheless, RSV is responsible for the most severe and life-threatening illnesses. Viral infection triggers an inflammatory response, activating interferon (IFN)-mediated responses, including IFN-stimulated genes (ISG) expression with antiviral and immunomodulatory activities. In parallel, the reactive oxygen species (ROS) production activates nuclear factor erythroid 2-related factor 2 (NRF2), whose antioxidant activity can reduce inflammation by interacting with the NF-kB pathway and the IFN response. To clarify how the interplay of IFN and NRF2 may impact on clinical severity, we enrolled children hospitalized for bronchiolitis and pneumonia, and measured gene expression of type-I and III IFNs, of several ISGs, of NRF2 and antioxidant-related genes, i.e., glucose-6-phosphate dehydrogenase (G6PD), heme oxygenase 1 (HO1), and NAD(P)H dehydrogenase [Quinone] 1 (NQO1) in RSV- (RSV-A N = 33 and RSV-B N = 30) and HRV (N = 22)-positive respiratory samples. NRF2 and HO1 expression is significantly elevated in children with HRV infection compared to RSV (p = 0.012 and p = 0.007, respectively), whereas ISG15 and ISG56 expression is higher in RSV-infected children (p = 0.016 and p = 0.049, respectively). Children admitted to a pediatric intensive care unit (PICU) had reduced NRF2 expression (p = 0.002). These data suggest, for the first time, that lower activation of the NRF2 antioxidant response in RSV-infected infants may contribute to bronchiolitis severity.

Expressions of Type I and III Interferons, Endogenous Retroviruses, TRIM28, and SETDB1 in Children with Respiratory Syncytial Virus Bronchiolitis

Interferons (IFNs) and IFN-stimulated genes (ISGs) play essential roles for the control of viral infections. Their expression in infants with respiratory syncytial virus (RSV) bronchiolitis is poorly defined. Human endogenous retroviruses (HERVs) represent 8% of our genome and modulate inflammatory and immune reactions. TRIM28 and SETDB1 participate in the epigenetic regulation of genes involved in the immune response, including IFNs and HERVs. No study has explored the expression of HERVs, TRIM28, and SETDB1 during RSV bronchiolitis. We assessed, through a PCR real-time Taqman amplification assay, the transcription levels of six IFN-I ISGs, four IFNλs, the pol genes of HERV-H, -K, and -W families, the env genes of Syncytin (SYN)1 and SYN2, and of TRIM28/SETDB1 in whole blood from 37 children hospitalized for severe RSV bronchiolitis and in healthy children (HC). The expression of most IFN-I ISGs was significantly higher in RSV+ patients than in age-matched HC, but it was inhibited by steroid therapy. The mRNA concentrations of IFN-λs were comparable between patients and age-matched HC. This lack of RSV-driven IFN-III activation may result in the defective protection of the airway mucosal surface leading to severe bronchiolitis. The expression of IFN-III showed a positive correlation with age in HC, that could account for the high susceptibility of young children to viral respiratory tract infections. The transcription levels of every HERV gene were significantly lower in RSV+ patients than in HC, while the expressions of TRIM28/SETDB1 were overlapping. Given the negative impact of HERVs and the positive effects of TRIM28/SETDB1 on innate and adaptive immune responses, the downregulation of the former and the normal expression of the latter may contribute to preserving immune functions against infection.

Overexpression of IFIT1 protects against LPS-induced acute lung injury via regulating CCL5-p65NF-κB signaling

Acute lung injury (ALI) is featured by intensive inflammatory responses causing significant morbidity and mortality. Interferon-induced protein with tetratricopeptide repeats 1 (IFIT1), induced by interferon (IFN), has been discovered to modulate viral infection and cell apoptosis and inhibit the production of pro-inflammatory cytokines. However, it's role and mechanism in ALI remain unclear and need to be explored furtherly. Here, we discovered that IFIT1 decreased the expression of TNF-α, IL-1β and IL-6 in mouse-derived macrophage cells (MH-S) and alleviated apoptosis of murine lung epithelial cells (MLE-12) induced by MH-S cell supernatant, contributing to anti-inflammatory and antiapoptotic effects in vitro and in vivo. Moreover, RNA sequencing analysis (RNA-seq) showed that inflammatory chemokine CC motif chemokine ligand 5 (CCL5) partially eliminated the protective effects of IFIT1 and promoted the expression of inflammatory cytokines TNF-α, IL-1β and IL-6 by CCL5-p65NF-κB signaling pathway. This study demonstrated that IFIT1 attenuated ALI-associated inflammation and cell apoptosis by regulating the CCL5-p65NF-κB signaling pathway. These findings are of great significance for the treatment of lung injury.

Short-chain fatty acid acetate triggers antiviral response mediated by RIG-I in cells from infants with respiratory syncytial virus bronchiolitis

Background

Gut microbiota-derived short-chain fatty-acid (SFCA) acetate protects mice against RSV A2 strain infection by increasing interferon-β production and expression of interferon-stimulated genes (ISGs). However, the role of SFCA in RSV infection using strains isolated from patients is unknown.

Methods

We first used RSV clinical strains isolated from infants hospitalized with RSV bronchiolitis to investigate the effects of in vitro SCFA-acetate treatment of human pulmonary epithelial cells. We next examined whether SCFA-acetate treatment is beneficial in a mouse model of RSV infection using clinical isolates. We sought to investigate the relationship of gut microbiota and fecal acetate with disease severity among infants hospitalized with RSV bronchiolitis, and whether treating their respiratory epithelial cells with SCFA-acetate ex-vivo impacts viral load and ISG expression. We further treated epithelial cells from SARS-CoV-2 infected patients with SCFA-acetate.

Findings

In vitro pre-treatment of A549 cells with SCFA-acetate reduced RSV infection with clinical isolates and increased the expression of RIG-I and ISG15. Animals treated with SCFA-acetate intranasally recovered significantly faster, with reduction in the RSV clinical isolates viral load, and increased lung expression of IFNB1 and the RIG-I. Experiments in RIG-I knockout A549 cells demonstrated that the protection relies on RIG-I presence. Gut microbial profile was associated with bronchiolitis severity and with acetate in stool. Increased SCFA-acetate levels were associated with increasing oxygen saturation at admission, and shorter duration of fever. Ex-vivo treatment of patients’ respiratory cells with SCFA-acetate reduced RSV load and increased expression of ISGs OAS1 and ISG15, and virus recognition receptors MAVS and RIG-I, but not IFNB1. These SCFA-acetate effects were not found on cells from SARS-CoV-2 infected patients.

Interpretation

SCFA-acetate reduces the severity of RSV infection and RSV viral load through modulation of RIG-I expression.

Funding

FAPERGS (FAPERGS/MS/CNPq/SESRS no. 03/2017 - PPSUS 17/2551-0001380-8 and COVID-19 20/2551-0000258-6); CNPq 312504/2017-9; CAPES) - Finance Code 001.

Clinical and biological consequences of respiratory syncytial virus genetic diversity

Respiratory syncytial virus (RSV) is one of the most common etiological agents of global acute respiratory tract infections with a disproportionate burden among infants, individuals over the age of 65, and immunocompromised populations. The two major subtypes of RSV (A and B) co-circulate with a predominance of either group during different epidemic seasons, with frequently emerging genotypes due to RSV's high genetic variability. Global surveillance systems have improved our understanding of seasonality, disease burden, and genomic evolution of RSV through genotyping by sequencing of attachment (G) glycoprotein. However, the integration of these systems into international infrastructures is in its infancy, resulting in a relatively low number (~2200) of publicly available RSV genomes. These limitations in surveillance hinder our ability to contextualize RSV evolution past current canonical attachment glycoprotein (G)-oriented understanding, thus resulting in gaps in understanding of how genetic diversity can play a role in clinical outcome, therapeutic efficacy, and the host immune response. Furthermore, utilizing emerging RSV genotype information from surveillance and testing the impact of viral evolution using molecular techniques allows us to establish causation between the clinical and biological consequences of arising genotypes, which subsequently aids in informed vaccine design and future vaccination strategy. In this review, we aim to discuss the findings from current molecular surveillance efforts and the gaps in knowledge surrounding the consequence of RSV genetic diversity on disease severity, therapeutic efficacy, and RSV-host interactions.

Proposal for Human Respiratory Syncytial Virus Nomenclature below the Species Level

Human respiratory syncytial virus (HRSV) is the leading viral cause of serious pediatric respiratory disease, and lifelong reinfections are common. Its 2 major subgroups, A and B, exhibit some antigenic variability, enabling HRSV to circulate annually. Globally, research has increased the number of HRSV genomic sequences available. To ensure accurate molecular epidemiology analyses, we propose a uniform nomenclature for HRSV-positive samples and isolates, and HRSV sequences, namely: HRSV/subgroup identifier/geographic identifier/unique sequence identifier/year of sampling. We also propose a template for submitting associated metadata. Universal nomenclature would help researchers retrieve and analyze sequence data to better understand the evolution of this virus.

ACE2 expression is related to the interferon response in airway epithelial cells but is that functional for SARS-CoV-2 entry?

In vitro interferon (IFN)α treatment of primary human upper airway basal cells has been shown to drive ACE2 expression, the receptor of SARS-CoV-2. The protease furin is also involved in mediating SARS‐CoV‐2 and other viral infections, although its association with early IFN response has not been evaluated yet. In order to assess the in vivo relationship between ACE2 and furin expression and the IFN response in nasopharyngeal cells, we first examined ACE2 and furin levels and their correlation with the well-known marker of IFNs’ activation, ISG15, in children (n = 59) and adults (n = 48), during respiratory diseases not caused by SARS-CoV-2. A strong positive correlation was found between ACE2 expression, but not of furin, and ISG15 in all patients analyzed. In addition, type I and III IFN stimulation experiments were performed to examine the IFN-mediated activation of ACE2 isoforms (full-length and truncated) and furin in epithelial cell lines. Following all the IFNs treatments, only the truncated ACE2 levels, were upregulated significantly in the A549 and Calu3 cells, in particular by type I IFNs. If confirmed in vivo following IFNs’ activation, the induction of the truncated ACE2 isoform only would not enhance the risk of SARS‐CoV‐2 infection in the respiratory tract.

Differential induction of type I and III interferon genes in the upper respiratory tract of patients with coronavirus disease 2019 (COVID-19)

The natural course of type I and III interferon (IFN) response in the respiratory tract of COVID-19 patients needs to be better defined. We showed that type I/III IFNs, IFN-regulatory factor 7 (IRF7), and IFN stimulated genes (ISGs), are highly expressed in the oropharyngeal cells of SARS-CoV-2 positive patients compared to healthy controls. Notably, the subgroup of critically-ill patients that required invasive mechanical ventilation had a general decrease in expression of IFN/ISG genes. Heterogeneous patterns of IFN-I/III response in the respiratory tract of COVID-19 patients may be associated to COVID-19 severity.

SARS-CoV-2 Entry Genes Expression in Relation with Interferon Response in Cystic Fibrosis Patients

The expression rate of SARS-CoV-2 entry genes, angiotensin-converting enzyme 2 (ACE2), the main viral receptor and the proteases, furin and transmembrane serine protease 2 (TMPRSS2) in cystic fibrosis (CF) individuals is poorly known. Hence, we examined their levels in upper respiratory samples of CF patients (n = 46) and healthy controls (n = 45). Moreover, we sought to understand the interplay of type I interferon (IFN-I) with ACE2, furin and TMPRSS2 by evaluating their gene expression with respect to ISG15, a well-known marker of IFN activation, in upper respiratory samples and after ex vivo IFNβ exposure. Lower ACE2 levels and trends toward the reduction of furin and TMPRSS2 were found in CF patients compared with the healthy controls; decreased ACE2 amounts were also detected in CF individuals with pancreatic insufficiency and in those receiving inhaled antibiotics. Moreover, there was a strong positive correlation between ISG15 and ACE2 levels. However, after ex vivo IFNβ stimulation of nasopharyngeal cells, the truncated isoform (dACE2), recently demonstrated as the IFN stimulated one with respect to the full-length isoform (flACE2), slightly augmented in cells from CF patients whereas in those from healthy donors, dACE2 levels showed variable levels of upregulation. An altered expression of SARS-COV-2 entry genes and a poor responsiveness of dACE2 to IFN-I stimulation might be crucial in the diffusion of SARS-CoV-2 infection in CF.