Viral and host factors in human respiratory syncytial virus pathogenesis

Binding and neutralising antibodies to respiratory syncytial virus and influenza A virus in serum and bronchoalveolar lavage fluid of healthy adults in the United States: A cross-sectional study

Using serum and bronchoalveolar lavage (BAL) fluid collected from 20 healthy adults (23-37 years, 55 % female) in the United States, we measured immunoglobulin (Ig) A, IgG, and neutralising activity against respiratory syncytial virus (RSV) and influenza A (H1N1) virus. RSV-binding IgA and IgG measurements in serum were positively correlated with those in BAL. For influenza A (H1N1) virus, serum and BAL IgA antibodies were positively correlated, whereas IgG antibodies did not show a significant correlation. RSV-specific and influenza A (H1N1)-specific neutralising activity did not correlate between serum and BAL samples. These results demonstrate virus-specific correlations between antibodies in the serum and BAL that may not necessarily reflect correlations in functional activity. Further work is needed to confirm our preliminary observations, and define the immune correlates of neutralising activity to these and other respiratory viruses in the lower respiratory tract.

From setbacks to success: lessons from the journey of RSV vaccine development

Respiratory syncytial virus (RSV) causes high worldwide infant mortality, as well as a high disease burden in the elderly. Efforts in vaccine development over the past 60 years have recently delivered three approved vaccines and two monoclonal antibodies (mAbs). Looking back at the eventful history of RSV vaccine development, several factors can be identified that have hampered the developmental pathway, including the occurrence of enhanced RSV disease (ERD) in the first vaccine attempt and the difficulty in characterizing and stabilizing the pre-fusion F protein as a vaccine target. Moreover, the need for large trials to test vaccine efficacy, usually done late in development, and the lack of a correlate of protection (CoP) result in significant uncertainties in RSV vaccine development. The use of controlled human infection models (CHIMs) may provide a solution for some of these problems: through swift, cost-efficient and closely monitored assessment of vaccine safety and efficacy in early clinical phases, vaccines can either 'fail fast' or show results supporting further investments. Moreover, CHIMs facilitate the assessment of disease and could assist in the identification of a CoP supporting late-stage development. Although some factors may affect translatability to real-world vaccine efficacy, CHIMs can support the clinical development pathway in various ways. We advocate for, and demonstrate, a conceptual and rational design of RSV vaccine development. Assessing protective efficacy early on would result in the most cost-efficient pathway and identification of target populations should be done as early as possible. For RSV, elderly individuals and people in low- and middle-income countries are high-impact populations for RSV prevention. While RSV immunization is now available in certain regions, global access is not accomplished yet, and worldwide prevention does not seem within reach. Quick and cost-effective assessments of candidates currently in the pipeline could contribute to future successes in the battle against RSV.

Biology of human respiratory syncytial virus: Current perspectives in immune response and mechanisms against the virus

Human respiratory syncytial virus (hRSV) remains a leading cause of morbidity and mortality in infants, young children, and older adults. hRSV infection's limited treatment and vaccine options significantly increase bronchiolitis' morbidity rates. The severity and outcome of viral infection hinge on the innate immune response. Developing vaccines and identifying therapeutic interventions suitable for young children, older adults, and pregnant women relies on comprehending the molecular mechanisms of viral PAMP recognition, genetic factors of the inflammatory response, and antiviral defense. This review covers fundamental elements of hRSV biology, diagnosis, pathogenesis, and the immune response, highlighting prospective options for vaccine development.

Parental knowledge about respiratory syncytial virus and attitudes toward infant immunization with monoclonal antibodies in France

BACKGROUND AND AIM

Respiratory syncytial virus (RSV) is a leading cause of hospitalization of infants with respiratory infections. A new immunization using monoclonal antibodies (mAbs) may offer protection against RSV infections. A study was conducted across eight countries to gain insight into parental awareness of RSV, their sources of child health information, and attitudes toward infant immunization against RSV using mAbs. This paper presents the findings from France.

METHODS

In 2021, a survey was conducted in eight countries among expecting and current parents with children younger than 24 months of age. Eligible respondents included parents who were open to childhood immunizations, i.e., they had given or planned to give their children "all," "most," or "some" immunizations.

RESULTS

In France, the survey respondents had high adoption rates for childhood immunizations. Key drivers behind these high rates were the desire to protect their children from severe diseases and adherence to mandatory immunizations, whereas concerns about safety were the main barriers. While general practitioners and pediatricians were key sources of advice on child health, many parents also requested information about immunizations from health authorities and nurses. Sources of advice varied with parental age, gender, educational level, and income. The majority of parents had no knowledge about mAbs or passive immunization, and the overall awareness of RSV was low. When informed about RSV and mAbs, most parents held neutral to positive attitudes toward nirsevimab for their infants if recommended by a healthcare professional and/or included in the immunization program. These findings were further confirmed by the 60 %-80 % uptake rates of nirsevimab following the introduction in September 2023.

A complex remodeling of cellular homeostasis distinguishes RSV/SARS-CoV-2 co-infected A549-hACE2 expressing cell lines

Concurrent infections with two or more pathogens with analogous tropism, such as RSV and SARS-CoV-2, may antagonize or facilitate each other, modulating disease outcome. Clinically, discrepancies in the severity of symptoms have been reported in children with RSV/SARS-CoV-2 co-infection. Herein, we propose an in vitro co-infection model to assess how RSV/SARS-CoV-2 co-infection alters cellular homeostasis. To this end, A549-hACE2 expressing cells were either infected with RSV or SARS-CoV-2 alone or co-infected with both viruses. Viral replication was assessed at 72 hours post infection by droplet digital PCR, immunofluorescence, and transmission electron microscopy. Anti-viral/receptor/autophagy gene expression was evaluated by RT-qPCR and confirmed by secretome analyses and intracellular protein production. RSV/SARS-CoV-2 co-infection in A549-hACE2 cells was characterized by: 1) an increase in the replication rate of RSV compared to single infection; 2) an increase in one of the RSV host receptors, ICAM1; 3) an upregulation in the expression/secretion of pro-inflammatory genes; 4) a rise in the number and length of cellular conduits; and 5) augmented autophagosomes formation and/or alteration of the autophagy pathway. These findings suggest that RSV/SARS-CoV-2 co-infection model displays a unique and specific viral and molecular fingerprint and shed light on the viral dynamics during viral infection pathogenesis. This in vitro co-infection model may represent a potential attractive cost-effective approach to mimic both viral dynamics and host cellular responses, providing in future readily measurable targets predictive of co-infection progression.

Exploring pathogen population density as a metric for understanding post-COVID infectious disease surges

After the easing of COVID-19 restrictions, peaks of common infectious diseases surpassed pre-pandemic levels, raising questions about causes and ways to monitor these changes. A proposed measure, the Pathogen Population Density (PPD) score, could help track these shifts. PPD refers to the concentration of infectious agents within a population at a given time and location, serving as a potential indicator of infection levels in susceptible individuals at the population level. It is likely that PPD remains relatively stable within a specific community, as an equilibrium forms between infections and susceptibility. During the pandemic, nonpharmaceutical interventions (NPIs) led to a reduction in infectious diseases, possibly lowering population immunity and decreasing the PPD score. Once NPIs were lifted, the PPD score likely increased sharply due to a larger pool of susceptible individuals, causing more primary infections and stronger recurrent infections, faster transmission, and more severe pathogenic outcomes at the individual level. Monitoring the PPD score over time could help predict when infection peaks will occur. PPD is influenced by factors such as public health strategies, vaccination programs, and the behavior of high-risk individuals. As a quantitative measure, PPD has the potential to serve as a valuable predictive and monitoring tool, helping public health officials anticipate and track changes in infectious disease dynamics. It could be an effective tool for managing future outbreaks or pandemics and serve as a communication tool between scientists and the public to understand the emergence of new disease peaks.

8-Oxoguanine DNA Glycosylase1 conceals oxidized guanine in nucleoprotein-associated RNA of respiratory syncytial virus

Respiratory syncytial virus (RSV), along with other prominent respiratory RNA viruses such as influenza and SARS-CoV-2, significantly contributes to the global incidence of respiratory tract infections. These pathogens induce the production of reactive oxygen species (ROS), which play a crucial role in the onset and progression of respiratory diseases. However, the mechanisms by which viral RNA manages ROS-induced base oxidation remain poorly understood. Here, we reveal that 8-oxo-7,8-dihydroguanine (8-oxoGua) is not merely an incidental byproduct of ROS activity but serves as a strategic adaptation of RSV RNA to maintain genetic fidelity by hijacking the 8-oxoguanine DNA glycosylase 1 (OGG1). Through RNA immunoprecipitation and next-generation sequencing, we discovered that OGG1 binding sites are predominantly found in the RSV antigenome, especially within guanine-rich sequences. Further investigation revealed that viral ribonucleoprotein complexes specifically exploit OGG1. Importantly, inhibiting OGG1's ability to recognize 8-oxoGua significantly decreases RSV progeny production. Our results underscore the viral replication machinery's adaptation to oxidative challenges, suggesting that inhibiting OGG1's reading function could be a novel strategy for antiviral intervention.

Clinical Features of RS Virus Infection before, during, and after COVID-19 Pandemic

The COVID-19 pandemic has impacted the epidemiology of other infectious diseases. In particular, the respiratory syncytial (RS) virus infects almost all children during their first or second year of life. However, during the COVID-19 pandemic, many restrictions were enforced that isolated children from other children. Therefore, we hypothesized that the clinical features of RS virus infection were altered and conducted a study to evaluate these changes. This observational study included children below the age of six years who were admitted to the Tokyo Metropolitan Toshima Hospital. Their clinicodemographic data were extracted from medical records. The 369 children eligible for the study were assigned to three groups: "pre-pandemic" (group 1, n = 253); "during pandemic" (group 2, n = 77), and "post-pandemic" (group 3, n = 39). Logistic regression analysis revealed that compared to group 1, the odds ratio (OR) for oxygen use was significantly higher in groups 2 (OR 1.85. 95% confidence interval [CI] 1.06-3.23; p < 0.05) and 3 (OR 3.36, 95% CI 1.59-7.12; p < 0.01), and the use of mechanical ventilation was significantly higher in group 3 (OR 4.89, 95% CI 1.71-13.94; p < 0.01). This study highlights changes in the clinical features of RS virus infection during and after the COVID-19 pandemic.

Recent Progress toward the Discovery of Small Molecules as Novel Anti-Respiratory Syncytial Virus Agents

Respiratory syncytial virus (RSV) stands as the foremost cause of infant hospitalization globally, ranking second only to malaria in terms of infant mortality. Although three vaccines have recently been approved for the prophylaxis of adults aged 60 and above, and pregnant women, there is currently no effective antiviral drug for treating RSV infections. The only preventive measure for infants at high risk of severe RSV disease is passive immunization through monoclonal antibodies. This Perspective offers an overview of the latest advancements in RSV drug discovery of small molecule antivirals, with particular focus on the promising findings from agents targeting the fusion and polymerase proteins. A comprehensive reflection on the current state of RSV research is also given, drawing inspiration from the lessons gleaned from HCV and HIV, while also considering the impact of the recent approval of the three vaccines.

Structure-Based Discovery of Allosteric Inhibitors Targeting a New Druggable Site in the Respiratory Syncytial Virus Polymerase

Respiratory syncytial virus (RSV) is a major cause of severe lower respiratory infections for which effective treatment options remain limited. Herein, we employed a computational structure-based design strategy aimed at identifying potential targets for a new class of allosteric inhibitors. Our investigation led to the discovery of a previously undisclosed allosteric binding site within the RSV polymerase, the large (L) protein. This discovery was achieved through a combination of virtual screening and molecular dynamics simulations. Subsequently, we identified two inhibitors, 6a and 10b, which both exhibited promising antiviral activity in the low micromolar range. Resistance profiling revealed a distinctive pattern in how RSV evaded treatment with this class of inhibitors. This pattern strongly suggested that this class of small molecules was targeting a new binding site in the RSV L protein, aligning with the computational predictions made in our study. This study paves the way for the development of more potent inhibitors for combating RSV infections by targeting a new druggable pocket within the RdRp which does not overlap with previously known resistance sites.

Computational Insights into the Interaction of the Conserved Cysteine-Noose Domain of the Human Respiratory Syncytial Virus G Protein with the Canonical Fractalkine Binding site of Transmembrane Receptor CX3CR1 Isoforms

The human Respiratory Syncytial Virus (hRSV) stands as one of the most common causes of acute respiratory diseases. The infectivity of this virus is intricately linked to its membrane proteins, notably the attachment glycoprotein (G protein). The latter plays a key role in facilitating the attachment of hRSV to respiratory tract epithelial cells, thereby initiating the infection process. The present study aimed to characterize the interaction of the conserved cysteine-noose domain of hRSV G protein (cndG) with the transmembrane CX3C motif chemokine receptor 1 (CX3CR1) isoforms using computational tools of molecular modeling, docking, molecular dynamics simulations, and binding free energy calculations. From MD simulations of the molecular system embedded in the POPC lipid bilayer, we showed a stable interaction of cndG with the canonical fractalkine binding site in the N-terminal cavity of the CX3CR1 isoforms and identified that residues in the extracellular loop 2 (ECL2) region and Glu279 of this receptor are pivotal for the stabilization of CX3CR1/cndG binding, corroborating what was reported for the interaction of the chemokine fractalkine with CX3CR1 and its structure homolog US28. Therefore, the results presented here contribute by revealing key structural points for the CX3CR1/G interaction, allowing us to better understand the biology of hRSV from its attachment process and to develop new strategies to combat it.

Activated Leukocyte Cell Adhesion Molecule Regulates the Expression of Interleukin-33 in RSV Induced Airway Inflammation by Regulating MAPK Signaling Pathways

PURPOSE

The respiratory syncytial virus (RSV) is a common respiratory virus that causes acute lower respiratory tract infectious diseases, particularly in young children and older individuals. Activated leukocyte cell adhesion molecule (ALCAM) is a membrane glycoprotein expressed in various cell types, including epithelial cells, and is associated with inflammatory responses and various cancers. However, the precise role of ALCAM in RSV-induced airway inflammation remains unclear, and our study aimed to explore this gap in the literature.

METHODS

C57BL/6 wild-type, ALCAM knockout mice and airway epithelial cells were infected with RSV and the expression of ALCAM and inflammatory cytokines were measured. We also conducted further experiments using Anti-ALCAM antibody and recombinant ALCAM in airway epithelial cells.

RESULTS

The expression levels of ALCAM and inflammatory cytokines increased in both RSV-infected mice and airway epithelial cells. Interestingly, IL-33 expression was significantly reduced in ALCAM-knockdown cells compared to control cells following RSV infection. Anti-ALCAM antibody treatment also reduced IL-33 expression following RSV infection. Furthermore, the phosphorylation of ERK1/2, p38, and JNK was diminished in ALCAM-knockdown cells compared to control cells following RSV infection. Notably, in the control cells, inhibition of these pathways significantly decreased the expression of IL-33. In vivo study also confirmed a reduction in inflammation induced by RSV infection in ALCAM deficient mice compared to wild-type mice.

CONCLUSION

These findings demonstrate that ALCAM contributes to RSV-induced airway inflammation at least partly by influencing IL-33 expression through mitogen-activated protein kinase signaling pathways. These results suggest that targeting ALCAM could be a potential therapeutic strategy for alleviating IL-33-associated lung diseases.

Approaches to the Prevention and Treatment of Respiratory Syncytial Virus Infection in Children: Rationale and Progress to Date

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection (LRTI) in children, and is associated with long-term pulmonary sequelae for up to 30 years after infection. The mainstay of RSV management is supportive therapy such as supplemental oxygen. Palivizumab (Synagis™-AstraZeneca), a monoclonal antibody targeting the RSV F protein site II, has been licensed for the prevention of RSV in high-risk groups since 1998. There has been recent promising progress in preventative strategies that include vaccines and long-acting, high-potency monoclonal antibodies. Nirsevimab (Beyfortus™-AstraZeneca/Sanofi), a monoclonal antibody with an extended half-life, has recently been registered in the European Union and granted licensure by the US Food and Drug Administration. Furthermore, a pre-fusion sub-unit protein vaccine has been granted licensure for pregnant women, aimed at protecting their young infants, following established safety and efficacy in clinical trials (Abrysvo™-Pfizer). Also, multiple novel antiviral therapeutic options are in early phase clinical trials. The next few years have the potential to change the landscape of LRTI through improvements in the prevention and management of RSV LRTI. Here, we discuss these new approaches, current research, and clinical trials in novel therapeutics, monoclonal antibodies, and vaccines against RSV infection in infants and children.

Knowledge, attitudes and behaviours of a sample of Italian paediatricians towards RSV and its preventive strategies: a cross-sectional study

BACKGROUND

Respiratory Syncytial Virus (RSV) infection mainly affects newborns, infants and young children aged < 2 years. Since an RSV vaccine is in the European Medicines Agency's waitlist validation, nowadays the prevention only includes passive immunization with monoclonal antibodies (mAb). In the present study we aimed at investigating Italian paediatricians' knowledge, attitudes and behaviours towards RSV and its prevention.

METHODS

From February to May 2023, an anonymous online questionnaire, with answers based on the Likert scale, was administered to a sample of Italian paediatricians' members of the Italian Society of Paediatrics. Descriptive and inferential statistical analyses were performed using STATA 17.

RESULTS

The paediatricians who answered the questionnaire were 507, mostly women (70.6%), aged 30-45 (33.1%), employed in hospitals in 66.6% of cases. The 10.8% of respondents reported that RSV is transmitted only among children younger than 2 years of age and 80.33% of participants that school-age children are not at risk of developing severe forms of RSV disease. The 25% of participants thought that active immunization is currently available to prevent RSV infection and 35.7% that does not exist passive immunization to prevent RSV for infants and newborns aged < 2 years. The 97.5% of physicians managed bronchiolitis cases and 65.6% of participants did not prescribe the administration of mAb. Higher age, seniority and RSV knowledge score were found to be associated with having a higher mAb knowledge score (p < 0.001) and having a higher RSV knowledge was associated with a higher mAb knowledge score (p < 0.001). The logistic regression model found that the odds of a positive attitude towards mAB knowledge score increased by over 3 times (OR 3.23, 95% CI [1.41, 7.40], p = 0.006) for being female and the odds of a positive attitude towards mAB knowledge score increased by almost 10 times (OR 9.73, 95% CI [3.06, 30.89], p < 0.001) for a one-unit increase in RSV knowledge score.

CONCLUSIONS

Paediatricians' limited knowledge or awareness could represent a barrier to the implementation of preventive strategies against RSV infection. Strategies to improve paediatricians' education on RSV prevention are, therefore, crucial.

Hypoxia inducible factors inhibit respiratory syncytial virus infection by modulation of nucleolin expression

Respiratory syncytial virus (RSV) is a global healthcare problem, causing respiratory illness in young children and elderly individuals. Our knowledge of the host pathways that define susceptibility to infection and disease severity are limited. Hypoxia inducible factors (HIFs) define metabolic responses to low oxygen and regulate inflammatory responses in the lower respiratory tract. We demonstrate a role for HIFs to suppress RSV entry and RNA replication. We show that hypoxia and HIF prolyl-hydroxylase inhibitors reduce the expression of the RSV entry receptor nucleolin and inhibit viral cell-cell fusion. We identify a HIF regulated microRNA, miR-494, that regulates nucleolin expression. In RSV-infected mice, treatment with the clinically approved HIF prolyl-hydroxylase inhibitor, Daprodustat, reduced the level of infectious virus and infiltrating monocytes and neutrophils in the lung. This study highlights a role for HIF-signalling to limit multiple aspects of RSV infection and associated inflammation and informs future therapeutic approaches for this respiratory pathogen.

Design, synthesis, and anti-respiratory syncytial virus potential of novel 3-(1,2,3-triazol-1-yl)furoxazine-fused benzimidazole derivatives

Respiratory syncytial virus (RSV) is a major cause of serious lower respiratory tract infections in infants, children, and older persons. Currently, the only approved anti-viral chemotherapeutic drug for RSV treatment is ribavirin aerosol; however, its significant toxicity has led to restricted clinical use. In a previous study, we developed various benzimidazole derivatives against RSV. In this study, we synthesised 3-azide substituted furoxazine-fused benzimidazole derivatives by sulfonylation and azide substitution of the 3-hydroxyl group of the furoxazine-fused benzimidazole derivatives. Subsequently, a series of 3-(1,2,3-triazol-1-yl)-substituted furoxazine-fused benzimidazole derivatives were synthesised using the classical click reaction. Biological evaluations of the target compounds indicated that compound 4a-2 had higher activity against RSV (EC50 = 12.17 μM) and lower cytotoxicity (CC50 = 390.64 μM). Compound 4a-2 exerted anti-viral effects against the RSV Long strain by inhibiting apoptosis and the elevation of reactive oxygen species (ROS) and inflammatory factors caused by viral infection in vitro. Additionally, the clinical symptoms of the virus-infected mice were markedly relieved, and the viral load in the lung tissues was dramatically decreased. The biosafety profile of compound 4a-2 was also favourable, showing no detectable adverse effects on any of the major organs in vivo. These findings underscore the potential of compound 4a-2 as a valuable therapeutic option for combating RSV infections while also laying the foundation for further research and development in the field.

Antiviral Activity of Probenecid and Oseltamivir on Influenza Virus Replication

Influenza can cause respiratory infections, leading to significant morbidity and mortality in humans. While current influenza vaccines offer varying levels of protection, there remains a pressing need for effective antiviral drugs to supplement vaccine efforts. Currently, the FDA-approved antiviral drugs for influenza include oseltamivir, zanamivir, peramivir, and baloxavir marboxil. These antivirals primarily target the virus, making them vulnerable to drug resistance. In this study, we evaluated the efficacy of the neuraminidase inhibitor, oseltamivir, against probenecid, which targets the host cells and is less likely to engender resistance. Our results show that probenecid has superior antiviral efficacy compared to oseltamivir in both in vitro replication assays and in vivo mouse models of influenza infection.

APOBEC3G Is a p53-Dependent Restriction Factor in Respiratory Syncytial Virus Infection of Human Cells Included in the p53/Immune Axis

Identifying and understanding genetic factors that influence the propagation of the human respiratory syncytial virus (RSV) can lead to health benefits and possibly augment recent vaccine approaches. We previously identified a p53/immune axis in which the tumor suppressor p53 directly regulates the expression of immune system genes, including the seven members of the APOBEC3 family of DNA cytidine deaminases (A3), which are innate immune sentinels against viral infections. Here, we examined the potential p53 and A3 influence in RSV infection, as well as the overall p53-dependent cellular and p53/immune axis responses to infection. Using a paired p53 model system of p53+ and p53- human lung tumor cells, we found that RSV infection activates p53, leading to the altered p53-dependent expression of A3D, A3F, and A3G, along with p53 site-specific binding. Focusing on A3G because of its 10-fold-greater p53 responsiveness to RSV, the overexpression of A3G can reduce RSV viral replication and syncytial formation. We also observed that RSV-infected cells undergo p53-dependent apoptosis. The study was expanded to globally address at the transcriptional level the p53/immune axis response to RSV. Nearly 100 genes can be directly targeted by the p53/immune axis during RSV infection based on our p53BAER analysis (Binding And Expression Resource). Overall, we identify A3G as a potential p53-responsive restriction factor in RSV infection. These findings have significant implications for RSV clinical and therapeutic studies and other p53-influenced viral infections, including using p53 adjuvants to boost the response of A3 genes.

Respiratory viral infection and resolution of inflammation: Roles for specialized pro-resolving mediators

Respiratory viral infections with influenza A virus (IAV) or respiratory syncytial virus (RSV) pose a significant threat to public health due to excess morbidity and mortality. Dysregulated and excessive inflammatory responses are major underlying causes of viral pneumonia severity and morbidity, including aberrant host immune responses and increased risk for secondary bacterial infections. Currently available antiviral therapies have not substantially reduced the risk of severe viral pneumonia for these pathogens. Thus, new therapeutic approaches that can promote resolution of the pathogen-initiated inflammation without impairing host defense would represent a significant advance. Recent research has uncovered the potential for specialized pro-resolving mediators (SPMs) to transduce multipronged actions for the resolution of serious respiratory viral infection without increased risk for subsequent host susceptibility to bacterial infection. Here, we review recent advances in our understanding of SPM production and SPM receptor signaling in respiratory virus infections and the intriguing potential of harnessing SPM pathways to control excess morbidity and mortality from IAV and RSV pneumonia.

Host Responses to Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) infections are a constant public health problem, especially in infants and older adults. Virtually all children will have been infected with RSV by the age of two, and reinfections are common throughout life. Since antigenic variation, which is frequently observed among other respiratory viruses such as SARS-CoV-2 or influenza viruses, can only be observed for RSV to a limited extent, reinfections may result from short-term or incomplete immunity. After decades of research, two RSV vaccines were approved to prevent lower respiratory tract infections in older adults. Recently, the FDA approved a vaccine for active vaccination of pregnant women to prevent severe RSV disease in infants during their first RSV season. This review focuses on the host response to RSV infections mediated by epithelial cells as the first physical barrier, followed by responses of the innate and adaptive immune systems. We address possible RSV-mediated immunomodulatory and pathogenic mechanisms during infections and discuss the current vaccine candidates and alternative treatment options.

Reshaping Our Knowledge: Advancements in Understanding the Immune Response to Human Respiratory Syncytial Virus

Human respiratory syncytial virus (hRSV) is a significant cause of respiratory tract infections, particularly in young children and older adults. In this review, we aimed to comprehensively summarize what is known about the immune response to hRSV infection. We described the innate and adaptive immune components involved, including the recognition of RSV, the inflammatory response, the role of natural killer (NK) cells, antigen presentation, T cell response, and antibody production. Understanding the complex immune response to hRSV infection is crucial for developing effective interventions against this significant respiratory pathogen. Further investigations into the immune memory generated by hRSV infection and the development of strategies to enhance immune responses may hold promise for the prevention and management of hRSV-associated diseases.

Immunogenicity and protective efficacy of an RSV G S177Q central conserved domain nanoparticle vaccine

Introduction

Respiratory syncytial virus (RSV) can cause lower respiratory tract disease in infants and elderly populations. Despite decades of research, there remains no safe and approved RSV vaccine. Previously, we showed that an RSV G glycoprotein subunit vaccine candidate with a single point mutation within the central conserved domain (CCD), i.e. S177Q, considerably improved immunogenicity.

Methods

Here, we examine the development of nanoparticle (NP) vaccines having either an RSV G protein CCD with wild-type sequence (NPWT) or an S177Q mutation (NP-S177Q). The NP vaccine immunogens were adjuvanted with monophosphoryl lipid A (MPLA), a TLR4 agonist to improve Th1- type responses. BALB/c mice were primed with 10 μg of NP-WT vaccine, NPS177Q, or vehicle, rested, and then boosted with a high (25 μg) or low (10 μg) dose of the NP-WT or NP-S177Q homologous candidate and subsequently challenged with RSV A2.

Results

The results showed that mice boosted with NP-S177Q developed superior immunogenicity and neutralizing antibodies compared to NP-WT boosting. IgG from either NP-S177Q or NP-WT vaccinated mice did not interfere with fractalkine (CX3CL1) binding to CX3CR1 and effectively blocked G protein CX3C-CX3CR1 binding. Both NP-WT and NP-S177Q vaccination induced similar neutralizing antibodies to RSV in challenged mice compared to vehicle control. NP-S177Q boosting improved correlates of protection including reduced BAL cell infiltration following RSV challenge. However, the NP vaccine platform will require improvement due to the poor solubility and the unexpectedly weaker Th1-type IgG2a response.

Discussion

The results from this study support further NP-S177Q vaccine candidate development.

Epidemiology and risk factors of respiratory syncytial virus associated acute respiratory tract infection in hospitalized children younger than 5 years from Sri Lanka

Background

Respiratory syncytial virus (RSV) is the leading cause of acute respiratory tract infections (ARTI) and a major cause of morbidity and mortality in children worldwide.

Aim

This study aimed to describe the prevalence and seasonal patterns of RSV and to determine the actual and predictive association of RSV-associated ARTI and clinical, socio-demographic, and climatic risk factors in children < 5 years.

Methods

Nasopharyngeal aspirates were collected from 500 children < 5 years admitted to the Kegalle General Hospital, Sri Lanka between May 2016 to July 2018. RSV and RSV subtypes were detected using immunofluorescence assay and real time RT-PCR, respectively. Descriptive and inferential statistics were done for the data analysis using Chi-square, Fisher's exact, Kruskal-Wallis test, and multiple binary logistic regression in the statistical package for social sciences (SPSS), version 16.0.

Results

Prevalence of RSV-associated ARTI was 28% in children < 5 years. Both RSV subtypes were detected throughout the study period. RSV-B was the dominant subtype detected with a prevalence of 72.14%. RSV infection in general caused severe respiratory disease leading to hypoxemia. Compared to RSV-B, RSV-A infection had more symptoms leading to hypoxemia. Factors increasing the risk of contracting RSV infection included number of people living (n > 6), having pets at home and inhaling toxic fumes. The inferential analysis predicts RSV infection in children < 5 years with ARTI, with a 75.4% probability with clinical and socio-demographic characteristics like age < 1 year, fever for > 4 days, cough, conjunctivitis, stuffiness, fatigue, six or more people at home, having pets at home and inhaling toxic fumes. Climatic factors like increases in temperature (°C), wind speed (Km/h), wind gust (Km/h), rainfall (mm) and atmospheric pressure (mb) showed a strong correlation with the RSV infection in children.

Nausea, Vomiting, and Diarrhea Are Common in Community-Acquired Acute Viral Respiratory Illness

BACKGROUND

Gastrointestinal (GI) symptoms are recognized sequelae of acute respiratory illness (ARI), but their prevalence is not well documented. Our study aim was to assess the incidence of GI symptoms in community ARI cases for persons of all ages and their association with clinical outcomes.

METHODS

We collected mid-nasal swabs, clinical, and symptom data from Seattle-area individuals during the 2018-2019 winter season as part of a large-scale prospective community surveillance study. Swabs were tested by polymerase chain reaction (PCR) for 26 respiratory pathogens. Likelihood of GI symptoms given demographic, clinical, and microbiological covariates were analyzed with Fisher's exact, Wilcoxon-rank-sum, and t-tests and multivariable logistic regression.

RESULTS

In 3183 ARI episodes, 29.4% had GI symptoms (n = 937). GI symptoms were significantly associated with pathogen detection, illness interfering with daily life, seeking care for the illness, and greater symptom burden (all p < 0.05). Controlling for age, > 3 symptoms, and month, influenza (p < 0.001), human metapneumovirus (p = 0.004), and enterovirus D68 (p = 0.05) were significantly more likely to be associated with GI symptoms than episodes with no pathogen detected. Seasonal coronaviruses (p = 0.005) and rhinovirus (p = 0.04) were significantly less likely to be associated with GI symptoms.

CONCLUSION

In this community-surveillance study of ARI, GI symptoms were common and associated with illness severity and respiratory pathogen detection. GI symptoms did not track with known GI tropism, suggesting GI symptoms may be nonspecific rather than pathogen-mediated. Patients presenting with GI and respiratory symptoms should have respiratory virus testing, even if the respiratory symptom is not the primary concern.

Respiratory Syncytial Virus-An Update for Prenatal and Primary Health Providers

Respiratory syncytial virus (RSV) infection is a significant cause of morbidity and mortality among infants aged younger than 1 year, adults aged 65 years or older, and immunocompromised persons. Limited data exist on RSV infection in pregnancy and further research is needed. Strides are being made to develop vaccines, including vaccines for maternal immunization, as well as monoclonal antibodies for disease prevention.

m6A reader proteins: the executive factors in modulating viral replication and host immune response

N6-Methyladenosine (m6A) modification is the most abundant covalent modification of RNA. It is a reversible and dynamic process induced by various cellular stresses including viral infection. Many m6A methylations have been discovered, including on the genome of RNA viruses and on RNA transcripts of DNA viruses, and these methylations play a positive or negative role on the viral life cycle depending on the viral species. The m6A machinery, including the writer, eraser, and reader proteins, achieves its gene regulatory role by functioning in an orchestrated manner. Notably, data suggest that the biological effects of m6A on target mRNAs predominantly depend on the recognition and binding of different m6A readers. These readers include, but are not limited to, the YT521-B homology (YTH) domain family, heterogeneous nuclear ribonucleoproteins (HNRNPs), insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs), and many others discovered recently. Indeed, m6A readers have been recognized not only as regulators of RNA metabolism but also as participants in a variety of biological processes, although some of these reported roles are still controversial. Here, we will summarize the recent advances in the discovery, classification, and functional characterization of m6A reader proteins, particularly focusing on their roles and mechanisms of action in RNA metabolism, gene expression, and viral replication. In addition, we also briefly discuss the m6A-associated host immune responses in viral infection.

Review and Update of Active and Passive Immunization Against Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection (LRTI) in children, causing approximately 3.6 million hospitalizations per year, and has been associated with long-term pulmonary sequelae for up to 30 years after infection, yet preventative strategies and active treatment options remain elusive. The associated morbidity and healthcare related costs could be decreased substantially with the development of these much-needed medications. After an initial false start in the development of an RSV vaccine, gradual progress is now being made with the development of multiple vaccine candidates using numerous different mechanisms of action. Furthermore, nirsevimab, a new monoclonal antibody for the prevention of RSV, has recently been registered in the European Union. New novel treatments for RSV infection are also in the pipeline, which would provide the clinician with much needed ammunition in the management of the acute disease. The next few years have the potential to change the landscape of LRTI forever through the prevention and management of RSV LRTI and thereby decrease the mortality and morbidity associated with it. In this review, we discuss these new approaches, current research, and clinical trials in monoclonal antibody and vaccine development against RSV.

Biochemistry of the Respiratory Syncytial Virus L Protein Embedding RNA Polymerase and Capping Activities

The human respiratory syncytial virus (RSV) is a negative-sense, single-stranded RNA virus. It is the major cause of severe acute lower respiratory tract infection in infants, the elderly population, and immunocompromised individuals. There is still no approved vaccine or antiviral treatment against RSV disease, but new monoclonal prophylactic antibodies are yet to be commercialized, and clinical trials are in progress. Hence, urgent efforts are needed to develop efficient therapeutic treatments. RSV RNA synthesis comprises viral transcription and replication that are catalyzed by the large protein (L) in coordination with the phosphoprotein polymerase cofactor (P), the nucleoprotein (N), and the M2-1 transcription factor. The replication/transcription is orchestrated by the L protein, which contains three conserved enzymatic domains: the RNA-dependent RNA polymerase (RdRp), the polyribonucleotidyl transferase (PRNTase or capping), and the methyltransferase (MTase) domain. These activities are essential for the RSV replicative cycle and are thus considered as attractive targets for the development of therapeutic agents. In this review, we summarize recent findings about RSV L domains structure that highlight how the enzymatic activities of RSV L domains are interconnected, discuss the most relevant and recent antivirals developments that target the replication/transcription complex, and conclude with a perspective on identified knowledge gaps that enable new research directions.

LAG-3 Contribution to T Cell Downmodulation during Acute Respiratory Viral Infections

LAG-3 is a type I transmembrane protein expressed on immune cells, such as activated T cells, and binds to MHC class II with high affinity. LAG-3 is an inhibitory receptor, and its multiple biological activities on T cell activation and effector functions play a regulatory role in the immune response. Immunotherapies directed at immune checkpoints, including LAG-3, have become a promising strategy for controlling malignant tumors and chronic viral diseases. Several studies have suggested an association between the expression of LAG-3 with an inadequate immune response during respiratory viral infections and the susceptibility to reinfections, which might be a consequence of the inhibition of T cell effector functions. However, important information relative to therapeutic potential during acute viral lower respiratory tract infections and the mechanism of action of the LAG-3 checkpoint remains to be characterized. In this article, we discuss the contribution of LAG-3 to the impairment of T cells during viral respiratory infections. Understanding the host immune response to respiratory infections is crucial for developing effective vaccines and therapies.

The burden and surveillance of RSV disease in young children in Belgium-expert opinion

Infections with respiratory syncytial virus (RSV) can cause severe disease. In young children, RSV is the most common cause of lower respiratory tract illness and life-threatening infections most commonly occur in the first years of life. In adults, elderly and immunocompromised people are most vulnerable. Recently there has been an acceleration in the development of candidate RSV vaccines, monoclonal antibodies and therapeutics which are expected to become available in Europe within the next 2-10 years. Understanding the true burden of childhood RSV disease will become very important to support public health authorities and policy makers in the assessment of new therapeutic opportunities against RSV disease. A systematic literature search was performed to map local data on the burden of RSV disease and to evaluate available RSV surveillance systems. A group of 9 paediatric infectious diseases specialists participated in an expert panel. The purpose of this meeting was to evaluate and map the burden associated with RSV infection in children, including patient pathways and the epidemiological patterns of virus circulation in Belgium. Sources of information on the burden of RSV disease in Belgium are very limited. For the outpatient setting, it is estimated that 5-10% of young patients seen in primary care are referred to the hospital. Around 3500 children between 0 and 12 months of age are hospitalized for RSV-bronchiolitis every year and represent the majority of all hospitalizations. The current Belgian RSV surveillance system was evaluated and found to be insufficient. Knowledge gaps are highlighted and future perspectives and priorities offered.

CONCLUSION

The Belgian population-based RSV surveillance should be improved, and a hospital-led reporting system should be put in place to enable the evaluation of the true burden of RSV disease in Belgium and to improve disease management in the future.

WHAT IS KNOWN

• RSV bronchiolitis is a very important cause of infant hospitalization. • The burden of disease in the community is poorly studied and underestimated.

WHAT IS NEW

• This expert opinion summarizes knowledge gaps and offers insights that allow improvement of local surveillance systems in order to establish a future-proof RSV surveillance system.

Chemokine/Interleukin Imbalance Aggravates the Pathology of Respiratory Syncytial Virus Infection

(1) Background: Almost 100% of children are initially infected by respiratory syncytial virus (RSV) by the age of 2 years, with 30% to 40% of children developing lower respiratory tract infections, of which 1% to 3% become severe. The severity of RSV-induced disease correlates with the influx of leukocytes, which leads to damage of the airways. We hence performed an immunological study based on the assumption that a chemokine/interleukin imbalance affects respiratory disorders caused by bronchiolitis and severe pneumonia. (2) Methods: The subjects were 19 infants without any underlying diseases, who developed respiratory symptoms owing to RSV infection. The subjects were stratified by their symptom severity, and chemokine and interleukin levels in their serum and tracheal aspirate fluid (TAF) were measured. (3) Results: The data of TAF, which were only obtained from subjects with severe symptoms, indicated that levels of inflammatory interleukins were much lower than the levels of chemokines. Three out of 6 subjects with severe symptoms showed below detectable levels of IL-6. TNF-α and IFN-γ levels were also lower than those of chemokines. The main increased CCL chemokines were CCL21 and CCL25, and the main increased CXCL chemokines were CXCL5, 8, 10, 12, and CX3CL1 in the lower respiratory region. Multiple regression analysis demonstrated that serum CX3CL1 and IL-6 levels were most strongly associated with symptom severity. This is the first report to date demonstrating that serum CX3CL1 level is associated with the severity of RSV infection. (4) Conclusions: Our results demonstrated that specific chemokines and the imbalance of cytokines are suspected to be associated with aggravated symptoms of RSV infection.

Prior respiratory syncytial virus infection reduces vaccine-mediated Th2-skewed immunity, but retains enhanced RSV F-specific CD8 T cell responses elicited by a Th1-skewing vaccine formulation

Respiratory syncytial virus (RSV) remains the most common cause of lower respiratory tract infections in children worldwide. Development of a vaccine has been hindered due the risk of enhanced respiratory disease (ERD) following natural RSV exposure and the young age (<6 months) at which children would require protection. Risk factors linked to the development of ERD include poorly neutralizing antibody, seronegative status (never been exposed to RSV), and a Th2-type immune response. Stabilization of the more antigenic prefusion F protein (PreF) has reinvigorated hope for a protective RSV vaccine that elicits potent neutralizing antibody. While anecdotal evidence suggests that children and adults previously exposed to RSV (seropositive) are not at risk for developing vaccine associated ERD, differences in host immune responses in seropositive and seronegative individuals that may protect against ERD remain unclear. It is also unclear if vaccine formulations that skew towards Th1- versus Th2-type immune responses increase pathology or provide greater protection in seropositive individuals. Therefore, the goal of this work was to compare the host immune response to a stabilized prefusion RSV antigen formulated alone or with Th1 or Th2 skewing adjuvants in seronegative and seropositive BALB/c mice. We have developed a novel BALB/c mouse model whereby mice are first infected with RSV (seropositive) and then vaccinated during pregnancy to recapitulate maternal immunization strategies. Results of these studies show that prior RSV infection mitigates vaccine-mediated skewing by Th1- and Th2-polarizing adjuvants that was observed in seronegative animals. Moreover, vaccination with PreF plus the Th1-skewing adjuvant, Advax, increased RSV F85-93-specific CD8 T cells in both seronegative and seropositive dams. These data demonstrate the importance of utilizing seropositive animals in preclinical vaccine studies to assess both the safety and efficacy of candidate RSV vaccines.

Clinical and Socioeconomic Burden of Respiratory Syncytial Virus in Iceland

INTRODUCTION

Respiratory syncytial virus (RSV), a very common pathogen, causes variable disease severity. In addition to considerable clinical burden on children, their families and healthcare facilities, RSV infections in children also carry significant direct and indirect socioeconomic burden.

METHODS

We analyzed data from 5 consecutive RSV seasons (2015-2020) and used virologically confirmed RSV infections and age <5 years as case definition. Clinical information was retrieved from electronic patient records. Costs were estimated by assuming an annual 30% attack rate and a combination of direct medical costs and calculations of societal costs of lost productivity.

RESULTS

A total of 716 children younger than 5 years of age had confirmed RSV infection of which 254 needed hospitalizations, most of whom were previously healthy. The median length of admission was 3.6 days and 13 patients needed intensive care. The hospital admission incidence rate was 2.5/1000 children/year, but 9.1 for children younger than 1 years of age. The total annual cost of RSV was estimated at €4.3 million, of which 10% was direct healthcare costs.

DISCUSSION

The clinical and socioeconomic disease burden of RSV in Iceland is substantial despite slightly lower hospital admission rates than other high-income countries. The prevention of RSV in young children, either through maternal or infant vaccination, has the potential to decrease both clinical and financial impact of the annual epidemics.

In Utero Ultrafine Particulate Exposure Yields Sex- and Dose-Specific Responses to Neonatal Respiratory Syncytial Virus Infection

Exposure to particulate matter (PM) is associated with lower respiratory tract infections. The role of ultrafine particles (UFPs, ≤0.1 μm) in respiratory disease is not fully elucidated, especially in models of immunologically immature populations. To characterize the effects of maternal UFP exposure on neonatal infection, we exposed time-mated C57Bl/6n mice to filtered air or UFPs at a low dose (LD, ∼55 μg/m3) and high dose (HD, ∼275 μg/m3) throughout gestation. At 5 days of age, offspring were infected with a respiratory syncytial virus (RSV) strain known to mimic infant infection or sham control. Offspring body weights were significantly reduced in response to infection in the LD RSV group, particularly females. Pulmonary gene expression analysis demonstrated significantly increased levels of oxidative stress- and inflammation-related genes in HD-exposed male offspring in sham and RSV-infected groups. In males, the highest grade of inflammation was observed in the HD RSV group, whereas in females, the LD RSV group showed the most marked inflammation. Overall, findings highlight neonatal responses are dependent on offspring sex and maternal UFP dose. Importantly, infant RSV pathology may be enhanced following even low dose UFP exposure signifying the importance of preventing maternal exposure.

The IRE1α-XBP1s Arm of the Unfolded Protein Response Activates N-Glycosylation to Remodel the Subepithelial Basement Membrane in Paramyxovirus Infection

Respiratory syncytial virus (RSV) causes severe lower respiratory tract infections (LRTI) associated with decreased pulmonary function, asthma, and allergy. Recently, we demonstrated that RSV induces the hexosamine biosynthetic pathway via the unfolded protein response (UPR), which is a pathway controlling protein glycosylation and secretion of the extracellular matrix (ECM). Because the presence of matrix metalloproteinases and matricellular growth factors (TGF) is associated with severe LRTI, we studied the effect of RSV on ECM remodeling and found that RSV enhances the deposition of fibronectin-rich ECM by small airway epithelial cells in a manner highly dependent on the inositol requiring kinase (IRE1α)–XBP1 arm of the UPR. To understand this effect comprehensively, we applied pharmacoproteomics to understand the effect of the UPR on N-glycosylation and ECM secretion in RSV infection. We observe that RSV induces N-glycosylation and the secretion of proteins related to ECM organization, secretion, or proteins integral to plasma membranes, such as integrins, laminins, collagens, and ECM-modifying enzymes, in an IRE1α–XBP1 dependent manner. Using a murine paramyxovirus model that activates the UPR in vivo, we validate the IRE1α–XBP1-dependent secretion of ECM to alveolar space. This study extends understanding of the IRE1α–XBP1 pathway in regulating N-glycosylation coupled to structural remodeling of the epithelial basement membrane in RSV infection.

Parental knowledge about respiratory syncytial virus (RSV) and attitudes to infant immunization with monoclonal antibodies

BACKGROUND

Ninety percent of all children are infected with respiratory syncytial virus (RSV) within their first two years of life. RSV is the main cause behind hospitalization of infants with lower respiratory tract infections. A new monoclonal antibody (mAb) immunization may prevent RSV in all infants. This cross-national study aimed to examine parental knowledge about RSV and attitudes to such RSV immunization.

RESEARCH DESIGN AND METHODS

Based on a literature study, a questionnaire was designed and applied in a survey carried out in China, France, Germany, Italy, Japan, Spain, the UK, and the US. Eligible respondents were expecting their first baby or parents of children <24 months old who were open to vaccination.

RESULTS

Parental acceptance of immunizations relies on perceptions of the preventable disease. In 5627 parents, only 35% reported basic or good level of knowledge about RSV. Recommendation from health care professionals and inclusion in immunization programs were crucial to their acceptance of RSV immunization. If recommended and informed about its efficacy and safety, most parents would accept RSV mAb immunization for their infants.

CONCLUSIONS

Infant RSV infections are highly prevalent, yet parental awareness of RSV is poor. Country variations call for targeted communication about RSV and immunization.

Identification of a βCD-Based Hyper-Branched Negatively Charged Polymer as HSV-2 and RSV Inhibitor

Cyclodextrins and cyclodextrin derivatives were demonstrated to improve the antiviral potency of numerous drugs, but also to be endowed with intrinsic antiviral action. They are suitable building blocks for the synthesis of functionalized polymer structures with potential antiviral activity. Accordingly, four water-soluble hyper-branched beta cyclodextrin (βCD)-based anionic polymers were screened against herpes simplex virus (HSV-2), respiratory syncytial virus (RSV), rotavirus (HRoV), and influenza virus (FluVA). They were characterized by FTIR-ATR, TGA, elemental analyses, zeta-potential measurements, and potentiometric titrations, while the antiviral activity was investigated with specific in vitro assays. The polymer with the highest negative charge, pyromellitic dianhydride-linked polymer (P_PMDA), showed significant antiviral action against RSV and HSV-2, by inactivating RSV free particles and by altering HSV-2 binding to the cell. The polymer fraction with the highest molecular weight showed the strongest antiviral activity and both P_PMDA and its active fractions were not toxic for cells. Our results suggest that the polymer virucidal activity against RSV can be exploited to produce new antiviral materials to counteract the virus dissemination through the air or direct contact. Additionally, the strong HSV-2 binding inhibition along with the water solubility of P_PMDA and the acyclovir complexation potential of βCD are attractive features for developing new therapeutic topical options against genital HSV-2 infection.

Rhinoviruses as critical agents in severe bronchiolitis in infants

OBJECTIVES

To detect RSV or other thirteen respiratory viruses as possible causer agent of bronchiolitis in infants.

METHOD

This is an epidemiological analytical study, conducted using a nasopharyngeal aspirate of 173 hospitalized children younger than two years old with severe bronchiolitis in three hospitals in the Campinas Metropolitan Region (CMR) during 2013-14. The data was statically evaluated by Pearson's chi-squared test with statistical significance of 0.05 and 95% confidence level.

RESULTS

As expected, the most prevalent viruses detected were RSV A and B in 47% and 16% of the samples, respectively. However, almost a third of severe bronchiolitis cases there were no detection of RSV, and the viruses more commonly detected were rhinoviruses, which were identified in almost a quarter of all positive samples for at least a viral agent.

CONCLUSIONS

Although nothing could be concluded from the disease severity and clinical-epidemiological data, the present study's results indicate that severe bronchiolitis is not always related to RSV infections in children younger than two years old, and the rhinoviruses were more prevalent in these cases. These findings reinforce the need to carry out a viral diagnosis in the hospital emergency would be very appropriate for all cases of respiratory infections in children, even for diseases in which the primary etiological agent seems to be well known.

Curcumin and Its Analogs as a Therapeutic Strategy in Infections Caused by RNA Genome Viruses

The use of natural resources for the prevention and treatment of diseases considered fatal to humanity has evolved. Several medicinal plants have nutritional and pharmacological potential in the prevention and treatment of viral infections, among them, turmeric, which is recognized for its biological properties associated with curcuminoids, mainly represented by curcumin, and found mostly in rhizomes. The purpose of this review was to compile the pharmacological activities of curcumin and its analogs, aiming at stimulating their use as a therapeutic strategy to treat infections caused by RNA genome viruses. We revisited its historical application as an anti-inflammatory, antioxidant, and antiviral agent that combined with low toxicity, motivated research against viruses affecting the population for decades. Most findings concentrate particularly on arboviruses, HIV, and the recent SARS-CoV-2. As one of the main conclusions, associating curcuminoids with nanomaterials increases solubility, bioavailability, and antiviral effects, characterized by blocking the entry of the virus into the cell or by inhibiting key enzymes in viral replication and transcription.

Axl Mediates Resistance to Respiratory Syncytial Virus Infection Independent of Cell Attachment

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections in infants and young children. Axl, a TAM family receptor tyrosine kinase (RTK), has been demonstrated as a receptor mediating enveloped virus infection. Here we show that Axl functions as a suppressor of antiviral response during RSV infection. Knockdown of Axl expression in human cells resulted in cell resistance to RSV infection although the treatment did not significantly affect RSV binding or cell entry. Mice deficiency of Axl showed resistance to RSV infection including reduction in viral load and in pulmonary injury. Although T lymphocyte and macrophage infiltration was reduced, more IFN-γ producing cells were present in BALF in Axl-/- mice. Less alternatively activated alveolar macrophages were found in the lungs of Axl-/- mice. Axl-/- MEF cells and siRNA-treated human cells had more robust IFN-β and ISG induction of antiviral genes. Furthermore, re-expression of Axl using Ad-mediated Axl delivery repressed ISG induction in Axl-null MEF cells by RSV infection. The results suggest that Axl, independent of being a virus entry receptor of RSV infection, negatively regulates interferon signaling to modulate host antiviral response against RSV infection.

Risk factors associated with severe disease in respiratory syncytial virus infected children under 5 years of age

OBJECTIVE

To evaluate risk factors for severe disease in children under 59 months of age hospitalized with respiratory syncytial virus (RSV) infection.

STUDY DESIGN

We prospectively enrolled 1,096 cases of laboratory confirmed RSV infection during three consecutive RSV seasons in 2015-2018. Potential risk factors for severe disease were retrieved through patient questionnaires and linkage to national health registries. Need for respiratory support (invasive ventilation, bi-level positive airway pressure, or continuous positive airway pressure), and length of stay exceeding 72 h were used as measures of disease severity. Associations were investigated using multivariable logistic regression analyses. Multiple imputation was used to avoid bias and inference induced by missing data.

RESULTS

Risk factors associated with a need for respiratory support included age younger than 3 months of age [aOR: 6.73 (95% CI 2.71-16.7)], having siblings [aOR: 1.65 (95% CI 1.05-2.59)] and comorbidity [aOR: 2.40 (95% CI 1.35-4.24)]. The length of hospital stay >72 h was significantly associated with being younger than 3 months of age [aOR: 3.52 (95% CI 1.65-7.54)], having siblings [aOR: 1.45 (95% CI 1.01-2.08)], and comorbidity [aOR: 2.18 (95% CI 1.31-3.61)]. Sub-group analysis of children younger than 6 months of age confirmed the association between both young age and having siblings and the need for respiratory support.

CONCLUSION

In a large cohort of children <59 months hospitalized with RSV infection, young age, comorbidity, and having siblings were associated with more severe disease.

The burden of respiratory syncytial virus in children under 5 years of age in Norway

OBJECTIVES

To estimate age-specific incidence of medically attended respiratory syncytial virus (RSV) infections in hospitalised Norwegian children and describe disease epidemiology.

METHODS

Active prospective hospital surveillance for RSV in children <59 months of age was conducted during 2015-2018. All febrile children 12-59 months of age were enrolled, whereas children <12 months were enrolled based on respiratory symptoms regardless of fever. Surveillance data were linked to national registry data to estimate the clinical burden of RSV.

RESULTS

Of the children enrolled, 1096 (40%) were infected with RSV. The highest incidence rates were found in children 1 month of age, with a peak incidence of 43 per 1000 during the 2016-2017 season. In comparison, children 24-59 months of age had an infection rate of 1.4 per 1000 during the same winter season. The peak season was during the 2016-2017 winter, with an incidence rate of 6.0 per 1000 children 0-59 months of age. In the study population a total of 168 (15%) of the infected children had pre-existing medical conditions predisposing for more severe disease. High infection rates were found in this population.

CONCLUSIONS

Children with comorbidities showed high hospital contact rates, but the majority of children in need of medical attention associated with RSV infection were previously healthy.

Bromodomain Containing Protein 4 (BRD4) Regulates Expression of its Interacting Coactivators in the Innate Response to Respiratory Syncytial Virus

Bromodomain-containing protein 4 plays a central role in coordinating the complex epigenetic component of the innate immune response. Previous studies implicated BRD4 as a component of a chromatin-modifying complex that is dynamically recruited to a network of protective cytokines by binding activated transcription factors, polymerases, and histones to trigger their rapid expression via transcriptional elongation. Our previous study extended our understanding of the airway epithelial BRD4 interactome by identifying over 100 functionally important coactivators and transcription factors, whose association is induced by respiratory syncytial virus (RSV) infection. RSV is an etiological agent of recurrent respiratory tract infections associated with exacerbations of chronic obstructive pulmonary disease. Using a highly selective small-molecule BRD4 inhibitor (ZL0454) developed by us, we extend these findings to identify the gene regulatory network dependent on BRD4 bromodomain (BD) interactions. Human small airway epithelial cells were infected in the absence or presence of ZL0454, and gene expression profiling was performed. A highly reproducible dataset was obtained which indicated that BRD4 mediates both activation and repression of RSV-inducible gene regulatory networks controlling cytokine expression, interferon (IFN) production, and extracellular matrix remodeling. Index genes of functionally significant clusters were validated independently. We discover that BRD4 regulates the expression of its own gene during the innate immune response. Interestingly, BRD4 activates the expression of NFκB/RelA, a coactivator that binds to BRD4 in a BD-dependent manner. We extend this finding to show that BRD4 also regulates other components of its functional interactome, including the Mediator (Med) coactivator complex and the SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin (SMARC) subunits. To provide further insight into mechanisms for BRD4 in RSV expression, we mapped 7,845 RSV-inducible Tn5 transposase peaks onto the BRD4-dependent gene bodies. These were located in promoters and introns of cytostructural and extracellular matrix (ECM) formation genes. These data indicate that BRD4 mediates the dynamic response of airway epithelial cells to RNA infection by modulating the expression of its coactivators, controlling the expression of host defense mechanisms and remodeling genes through changes in promoter accessibility.

Methods to Measure Antibody Neutralization of Live Human Coronavirus OC43

The human Betacoronavirus OC43 is a common cause of respiratory viral infections in adults and children. Lung infections with OC43 are associated with mortality, especially in hematopoietic stem cell transplant recipients. Neutralizing antibodies play a major role in protection against many respiratory viral infections, but to date a live viral neutralization assay for OC43 has not been described. We isolated a human monoclonal antibody (OC2) that binds to the spike protein of OC43 and neutralizes the live virus derived from the original isolate of OC43. We used this monoclonal antibody to develop and test the performance of two readily accessible in vitro assays for measuring antibody neutralization, one utilizing cytopathic effect and another utilizing an ELISA of infected cells. We used both methods to measure the neutralizing activity of the OC2 monoclonal antibody and of human plasma. These assays could prove useful for studying humoral responses to OC43 and cross-neutralization with other medically important betacoronaviruses.

Vitamin D in respiratory viral infections: a key immune modulator?

Respiratory viral infections are common respiratory diseases. Influenza viruses, RSV and SARS-COV2 have the potential to cause severe respiratory infections. Numerous studies have shown that unregulated immune response to these viruses can cause excessive inflammation and tissue damage. Therefore, regulating the antiviral immune response in the respiratory tract is of importance. In this regard, recent years studies have emphasized the importance of vitamin D in respiratory viral infections. Although, the most well-known role of vitamin D is to regulate the metabolism of phosphorus and calcium, it has been shown that this vitamin has other important functions. One of these functions is immune regulation. Vitamin D can regulate the antiviral immune response in the respiratory tract in order to provide an effective defense against respiratory viral infections and prevention from excessive inflammatory response and tissue damage. In addition, this vitamin has preventive effects against respiratory viral infections. Some studies during the COVID-19 pandemic have shown that vitamin D deficiency may be associated with a higher risk of mortality and sever disease in patients with COVID-19. Since, more attention has recently been focused on vitamin D. In this article, after a brief overview of the antiviral immune response in the respiratory system, we will review the role of vitamin D in regulating the antiviral immune response comprehensively. Then we will discuss the importance of this vitamin in influenza, RSV, and COVID-19.

Incidence of respiratory syncytial virus related health care utilization in the United States

Background

Respiratory Syncytial Virus (RSV) is one of the most frequent causes of acute respiratory infection worldwide. Understanding age-specific health care utilization is necessary to guide effective prevention strategies. This retrospective database analysis assessed the incidence rates of RSV-related health care utilization in the USA over a 7-year period.

Methods

Episodes of RSV were identified in the Truven Health MarketScan^® Commercial Claims and Encounters database between 2008 and 2014 using ICD-9-CM codes for pneumonia, bronchiolitis and RSV (480-486, 487.0, 466.1, 491.2, 079.6). Annual RSV-related health care utilization was calculated for the total population, by age group (<1, 1, 2-4, 5-17, 18-49, 50-64, 65-74, 75-84 and ≥85 years) and the proportion of cases for each setting (hospitalization, outpatient, or emergency department [ED] / urgent care [UC]).

Results

Over the 7-year study period, the mean rate of all RSV-associated health care utilization was 2.4 per 1000 person-years, with mean rates ranging from 2.0 to 2.6). The highest rate was seen in infants aged <1 year (mean 79.0 per 1000 over the 7-year period), which decreased with increasing age in the range 2-49 years before increasing with age in older adults (mean rate 8.1 per 1000 over the 7-year period in those ≥85 years). Of all RSV cases, 82% were reported in an outpatient setting, 11% in the ED/UC and 7% were hospitalized.

Conclusions

The annual RSV-related healthcare utilization rates were substantial, especially in infants and young children. These results underscore the need to accelerate the development of RSV prevention strategies to reduce the healthcare burden of RSV.

Regulatory effect of m6 A modification on different viruses

N⁶ -methyladenosine (m⁶ A) modification is the most common and reversible posttranscriptional modification of RNA in eukaryotes, which is mainly regulated by methyltransferase, demethylase, and specific binding protein. The replication of the virus and host immune response to the virus are affected by m⁶ A modification. In different kinds of viruses, m⁶ A modification has two completely opposite regulatory functions. This paper reviews the regulatory effects of m⁶ A modification on different viruses and provides a reference for studying the regulatory effects of RNA epitranscriptomic modification.

Paramyxovirus replication induces the hexosamine biosynthetic pathway and mesenchymal transition via the IRE1α-XBP1s arm of the unfolded protein response

The paramyxoviridae, respiratory syncytial virus (RSV), and murine respirovirus are enveloped, negative-sense RNA viruses that are the etiological agents of vertebrate lower respiratory tract infections (LRTIs). We observed that RSV infection in human small airway epithelial cells induced accumulation of glycosylated proteins within the endoplasmic reticulum (ER), increased glutamine-fructose-6-phosphate transaminases (GFPT1/2) and accumulation of uridine diphosphate (UDP)-N-acetylglucosamine, indicating activation of the hexosamine biosynthetic pathway (HBP). RSV infection induces rapid formation of spliced X-box binding protein 1 (XBP1s) and processing of activating transcription factor 6 (ATF6). Using pathway selective inhibitors and shRNA silencing, we find that the inositol-requiring enzyme (IRE1α)-XBP1 arm of the unfolded protein response (UPR) is required not only for activation of the HBP, but also for expression of mesenchymal transition (EMT) through the Snail family transcriptional repressor 1 (SNAI1), extracellular matrix (ECM)-remodeling proteins fibronectin (FN1), and matrix metalloproteinase 9 (MMP9). Probing RSV-induced open chromatin domains by ChIP, we find XBP1 binds and recruits RNA polymerase II to the IL6, SNAI1, and MMP9 promoters and the intragenic superenhancer of glutamine-fructose-6-phosphate transaminase 2 (GFPT2). The UPR is sustained through RSV by an autoregulatory loop where XBP1 enhances Pol II binding to its own promoter. Similarly, we investigated the effects of murine respirovirus infection on its natural host (mouse). Murine respirovirus induces mucosal growth factor response, EMT, and the indicators of ECM remodeling in an IRE1α-dependent manner, which persists after viral clearance. These data suggest that IRE1α-XBP1s arm of the UPR pathway is responsible for paramyxovirus-induced metabolic adaptation and mucosal remodeling via EMT and ECM secretion.