Respiratory syncytial virus: current and emerging treatment options

Respiratory Syncytial Virus Infection in Older Adults: An Update

Respiratory syncytial virus (RSV) infection represents one of the most common infections during childhood, with significant morbidity and mortality in newborns and in the early years of life. RSV is a common infection throughout all age groups, largely undetected and underestimated in adults, with a disproportionately high impact in older individuals. RSV infection has a wide range of clinical presentations, from asymptomatic conditions to acute pneumonia and severe life-threatening respiratory distress, including exacerbations of underlying chronic conditions. Overall, the incidence of RSV infections requiring medical attention increases with age, and it is highest among persons ≥ 70 years of age. As a consequence of a combination of an aging population, immunosenescence, and the related increased burden of comorbidities, high-income countries are at risk of developing RSV epidemics. The standard of care for RSV-infected patients remains supportive, including fluids, antipyretics, and oxygen support when needed. There is an urgent need for antivirals and preventive strategies in this population, particularly in individuals at higher risk of severe outcomes following RSV infection. In this review, we describe prevention and treatment strategies for RSV illnesses, with a deep focus on the novel data on vaccination that has become available (Arexvy, GSK, and Abrysvo, Pfizer) for older adults.

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.

Drugs targeting structural and nonstructural proteins of the chikungunya virus: A review

Chikungunya virus (CHIKV) is a single positive-stranded RNA virus of the Togaviridae family and Alphavirus genus, with a typical lipid bilayer envelope structure, and is the causative agent of human chikungunya fever (CHIKF). The U.S. Food and Drug Administration has recently approved the first chikungunya vaccine, Ixchiq; however, vaccination rates are low, and CHIKF is prevalent owing to its periodic outbreaks. Thus, developing effective anti-CHIKV drugs in clinical settings is imperative. Viral proteins encoded by the CHIKV genome play vital roles in all stages of infection, and developing therapeutic agents that target these CHIKV proteins is an effective strategy to improve CHIKF treatment efficacy and reduce mortality rates. Therefore, in the present review article, we aimed to investigate the basic structure, function, and replication cycle of CHIKV and comprehensively outline the current status and future advancements in anti-CHIKV drug development, specifically targeting nonstructural (ns) proteins, including nsP1, nsP2, nsP3, and nsP4 and structural proteins such as capsid (C), E3, E2, 6K, and E1.

Arexvy: A Comprehensive Review of the Respiratory Syncytial Virus Vaccine for Revolutionary Protection

The respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract infection in children and poses a significant risk to older adults. Developing a vaccine against RSV has been a priority, and the recently approved Arexvy vaccine has shown promise in preventing lower respiratory tract disease (LRTD) caused by RSV in individuals aged 60 years and older. This comprehensive review discusses the history of RSV, challenges in vaccine development, and the mechanism of action of Arexvy. The efficacy and safety of the vaccine are explored based on phase 3 clinical trial, demonstrating its effectiveness in preventing RSV-associated LRTD. The most common adverse reactions reported include injection site pain, fatigue, myalgia, headache, and arthralgia. Ongoing research focuses on the long-term effectiveness of Arexvy, including the need for booster doses and its impact on reducing RSV-associated hospitalizations. The potential of Arexvy to lessen the burden of RSV-related illnesses, particularly in vulnerable populations, is highlighted, emphasizing the importance of widespread immunization efforts and accessibility to this groundbreaking vaccine.

Respiratory syncytial virus infection and novel interventions

The large global burden of respiratory syncytial virus (RSV) respiratory tract infections in young children and older adults has gained increased recognition in recent years. Recent discoveries regarding the neutralization-specific viral epitopes of the pre-fusion RSV glycoprotein have led to a shift from empirical to structure-based design of RSV therapeutics, and controlled human infection model studies have provided early-stage proof of concept for novel RSV monoclonal antibodies, vaccines and antiviral drugs. The world's first vaccines and first monoclonal antibody to prevent RSV among older adults and all infants, respectively, have recently been approved. Large-scale introduction of RSV prophylactics emphasizes the need for active surveillance to understand the global impact of these interventions over time and to timely identify viral mutants that are able to escape novel prophylactics. In this Review, we provide an overview of RSV interventions in clinical development, highlighting global disease burden, seasonality, pathogenesis, and host and viral factors related to RSV immunity.

Immunoglobulin treatment for hospitalised infants and young children with respiratory syncytial virus infection

BACKGROUND

Millions of children are hospitalised due to respiratory syncytial virus (RSV) infection every year. Treatment is supportive, and current therapies (e.g. inhaled bronchodilators, epinephrine, nebulised hypertonic saline, and corticosteroids) are ineffective or have limited effect. Respiratory syncytial virus immunoglobulin may be used prophylactically to prevent hospital admission from RSV-related illness. It may be considered for the treatment of established severe RSV infection or for treatment in an immunocompromised host, although it is not licensed for this purpose. It is unclear whether immunoglobulins improve outcomes when used as a treatment for established RSV infection in infants and young children admitted to hospital. This is an update of a review first published in 2019.

OBJECTIVES

To assess the effects of immunoglobulins for the treatment of RSV-proven lower respiratory tract infections (LRTIs) in children aged up to three years, admitted to hospital.

SEARCH METHODS

For this 2022 update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Acute Respiratory Infections Specialised Register, Ovid MEDLINE, Embase, CINAHL, and Web of Science (from inception to 2 December 2022) with no restrictions. We searched two trial registries for ongoing trials (to 2 December 2022) and checked the reference lists of reviews and included articles for additional studies.

SELECTION CRITERIA

Randomised controlled trials comparing immunoglobulins with placebo in hospitalised infants and children aged up to three years with laboratory-diagnosed RSV lower respiratory tract infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed risk of bias, and extracted data. We assessed evidence certainty using GRADE.

MAIN RESULTS

In total, we included eight trials involving 906 infants and children aged up to three years. We included one new trial in this update. The immunoglobulin preparations used in these trials included anti-RSV immunoglobulin and the monoclonal antibody preparations palivizumab and motavizumab. Five trials were conducted at single or multiple sites within a single high-income country (four in the USA, one in Qatar). Three trials included study sites in different countries. All three of these trials included study sites in one or more high-income countries (USA, Chile, New Zealand, Australia, Qatar), with two trials also including a study site in a middle-income country (Panama). Five of the eight trials were "supported" or "sponsored" by the trial drug manufacturers. The evidence is very uncertain about the effect of immunoglobulins on mortality (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.14 to 5.27; 4 studies, 309 participants). There were four deaths - two amongst 98 children receiving immunoglobulins, and two amongst 98 children receiving placebo. One additional death occurred in a fourth trial, however the study group of the child was not known and the data were not included in the analysis (very low-certainty evidence). The use of immunoglobulins in infants and children admitted to hospital with RSV proven LRTI probably results in little to no difference in the length of hospitalisation (mean difference (MD) -0.13 days, 95% CI -0.37 to 0.12; 6 studies, 737 participants; moderate-certainty evidence). Immunoglobulins may result in little to no difference in the number of children who experience one or more adverse events of any severity or seriousness compared to placebo (RR 1.18, 95% CI 0.78 to 1.78; 5 studies, 340 participants; low-certainty evidence) or the number of children who experience one or more adverse events judged by study investigators to be serious in nature, compared to placebo (RR 1.08, 95% CI 0.65 to 1.79; 4 studies, 238 participants; low-certainty evidence). Certainty of evidence for secondary outcomes was low. This evidence suggests that use of immunoglobulins results in little to no difference in the need for, or duration of, mechanical ventilation and the need for, or duration of, supplemental oxygen. The use of immunoglobulins does not reduce the need for admission to the intensive care unit (ICU) and when children are admitted to the ICU results in little to no difference in the duration of ICU stay.

AUTHORS' CONCLUSIONS

We are very uncertain about the effect of immunoglobulins on mortality. We are moderately certain that use of immunoglobulins in hospitalised infants and children may result in little to no difference in the length of hospitalisation. Immunoglobulins may result in little to no difference in adverse events, the need for or duration of mechanical ventilation, supplemental oxygen, or admission to the intensive care unit, though we are less certain about this evidence and the true effect of immunoglobulins on these outcomes may differ markedly from the estimated effect observed in this review. All trials were conducted in high-income countries, and data from populations in which the rate of death from RSV infection is higher are lacking.

Two synthetic steroid analogs reduce human respiratory syncytial virus replication and the immune response to infection both in vitro and in vivo

HRSV is responsible for many acute lower airway infections and hospitalizations in infants, the elderly and those with weakened immune systems around the world. The strong inflammatory response that mediates viral clearance contributes to pathogenesis, and is positively correlated with disease severity. There is no specific effective therapy on hand. Antiviral synthetic stigmastanes (22S, 23S)-22,23-dihydroxystigmast-4-en-3-one (Compound 1) and 22,23-dihydroxystigmasta-1,4-dien-3-one (Compound 2) have shown to be active inhibiting unrelated virus like Herpes Simplex type 1 virus (HSV-1) and Adenovirus, without cytotoxicity. We have also shown that Compound 1 modulates the activation of cell signaling pathways and cytokine secretion in infected epithelial cells as well as in inflammatory cells activated by nonviral stimuli. In the present work, we investigated the inhibitory effect of both compounds on HRSV replication and their modulatory effect on infected epithelial and inflammatory cells. We show that compounds 1 and 2 inhibit in vitro HRSV replication and propagation and reduce cytokine secretion triggered by HRSV infection in epithelial and inflammatory cells. The compounds reduce viral loads and inflammatory infiltration in the lungs of mice infected with HRSV.

Hylin-a1: A Pan-Inhibitor against Emerging and Re-Emerging Respiratory Viruses

Pandemic and epidemic outbreaks of respiratory viruses are a challenge for public health and social care system worldwide, leading to high mortality and morbidity among the human populations. In light of the limited efficacy of current vaccines and antiviral drugs against respiratory viral infections and the emergence and re-emergence of new viruses, novel broad-spectrum antiviral drugs are needed for the prevention and treatment of these infections. Antimicrobial peptides with an antiviral effect, also known as AVPs, have already been reported as potent inhibitors of viral infections by affecting different stages of the virus lifecycle. In the present study, we analyzed the activity of the AVP Hylin-a1, secreted by the frog Hypsiboas albopunctatus, against a wide range of respiratory viruses, including the coronaviruses HCoV-229E and SARS-CoV-2, measles virus, human parainfluenza virus type 3, and influenza virus H1N1. We report a significant inhibitory effect on infectivity in all the enveloped viruses, whereas there was a lack of activity against the naked coxsackievirus B3. Considering the enormous therapeutic potential of Hylin-a1, further experiments are required to elucidate its mechanism of action and to increase its stability by modifying the native sequence.

In Silico Identification and In Vitro Validation of Repurposed Compounds Targeting the RSV Polymerase

Respiratory Syncytial Virus (RSV) is the top cause of infant hospitalization globally, with no effective treatments available. Researchers have sought small molecules to target the RNA-dependent RNA Polymerase (RdRP) of RSV, which is essential for replication and transcription. Based on the cryo-EM structure of the RSV polymerase, in silico computational analysis including molecular docking and the protein-ligand simulation of a database, including 6554 molecules, is currently undergoing phases 1-4 of clinical trials and has resulted in the top ten repurposed compound candidates against the RSV polymerase, including Micafungin, Totrombopag, and Verubecestat. We performed the same procedure to evaluate 18 small molecules from previous studies and chose the top four compounds for comparison. Among the top identified repurposed compounds, Micafungin, an antifungal medication, showed significant inhibition and binding affinity improvements over current inhibitors such as ALS-8112 and Ribavirin. We also validated Micafungin's inhibition of the RSV RdRP using an in vitro transcription assay. These findings contribute to RSV drug development and hold promise for broad-spectrum antivirals targeting the non-segmented negative-sense (NNS) RNA viral polymerases, including those of rabies (RABV) and Ebola (EBOV).

A Systematic Review of Clinical Pharmacokinetics of Inhaled Antiviral

Background and Objectives: The study of clinical pharmacokinetics of inhaled antivirals is particularly important as it helps one to understand the therapeutic efficacy of these drugs and how best to use them in the treatment of respiratory viral infections such as influenza and the current COVID-19 pandemic. The article presents a systematic review of the available pharmacokinetic data of inhaled antivirals in humans, which could be beneficial for clinicians in adjusting doses for diseased populations. Materials and Methods: This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. A comprehensive literature search was conducted using multiple databases, and studies were screened by two independent reviewers to assess their eligibility. Data were extracted from the eligible studies and assessed for quality using appropriate tools. Results: This systematic review evaluated the pharmacokinetic parameters of inhaled antiviral drugs. The review analyzed 17 studies, which included Zanamivir, Laninamivir, and Ribavirin with 901 participants, and found that the non-compartmental approach was used in most studies for the pharmacokinetic analysis. The outcomes of most studies were to assess clinical pharmacokinetic parameters such as the Cmax, AUC, and t1/2 of inhaled antivirals. Conclusions: Overall, the studies found that the inhaled antiviral drugs were well tolerated and exhibited favorable pharmacokinetic profiles. The review provides valuable information on the use of these drugs for the treatment of influenza and other viral respiratory infections.

Respiratory Syncytial Virus: A Comprehensive Review of Transmission, Pathophysiology, and Manifestation

With an increasing global incidence in children younger than the age of five, respiratory syncytial virus (RSV) is one of the most common viral respiratory infections worldwide. Despite the increasing number of cases among infants and young children, RSV can infect any age group; however, some individuals are more high risk than others. Premature infants, young children, elderly, and immunocompromised individuals are the most likely to suffer a more severe presentation of RSV in comparison to healthy adults. RSV is transmitted through respiratory droplets via direct contact with an infected individual or with contaminated surfaces. The viral genome of RSV consists of 11 proteins. Out of these 11, two proteins allow for the attachment of the virus to the respiratory epithelial cells and fusion with host cells. Upon fusion, the viral material transfers to the host cell, where viral replication occurs. It is important to acknowledge that an individual is considered infectious and can transmit the virus even before the symptomatic presentation of RSV begins. As long as the individual is shedding the virus, he or she is considered infectious. The length of viral shedding also differs depending on the severity of the infection, who is infected, and the underlying immune status of an individual. Currently, there is no definitive treatment for RSV; however, supportive therapy is considered the mainstay treatment. Some pharmaceutical treatments such as ribavirin have been FDA-approved; however, the administration is typically limited to children and infants. Palivizumab is also administered as an immune prophylaxis; however, both therapies are constantly at the end of a cost-effective debate due to their extensively expensive nature and questionable adverse effect profiles. Supportive therapy includes hydration, supplemental oxygen, and mechanical ventilation in hospitalized cases; however, most RSV cases can be treated as outpatient cases. Prevention techniques such as hand washing and maintaining social distancing are imperative to minimize the transmission of the virus as much as remotely possible.

Respiratory Syncytial Virus Infection: Treatments and Clinical Management

Respiratory syncytial virus (RSV) is a major healthcare concern, especially for immune-compromised individuals and infants below 5 years of age. Worldwide, it is known to be associated with incidences of morbidity and mortality in infants. Despite the seriousness of the issue and continuous rigorous scientific efforts, no approved vaccine or available drug is fully effective against RSV. The purpose of this review article is to provide insights into the past and ongoing efforts for securing effective vaccines and therapeutics against RSV. The readers will be able to confer the mechanism of existing therapies and the loopholes that need to be overcome for future therapeutic development against RSV. A methodological approach was applied to collect the latest data and updated results regarding therapeutics and vaccine development against RSV. We outline the latest throughput vaccination technologies and prophylactic development efforts linked with RSV. A range of vaccination approaches with the already available vaccine (with limited use) and those undergoing trials are included. Moreover, important drug regimens used alone or in conjugation with adjuvants or vaccines are also briefly discussed. After reading this article, the audience will be able to understand the current standing of clinical management in the form of the vaccine, prophylactic, and therapeutic candidates against RSV. An understanding of the biological behavior acting as a reason behind the lack of effective therapeutics against RSV will also be developed. The literature indicates a need to overcome the limitations attached to RSV clinical management, drugs, and vaccine development that could be explained by dealing with the challenges of current study designs with continuous improvement and further work and approval on novel therapeutic applications.

Alternative Routes of Administration for Therapeutic Antibodies—State of the Art

Background: For the past two decades, there has been a huge expansion in the development of therapeutic antibodies, with 6 to 10 novel entities approved each year. Around 70% of these Abs are delivered through IV injection, a mode of administration allowing rapid and systemic delivery of the drug. However, according to the evidence presented in the literature, beyond the reduction of invasiveness, a better efficacy can be achieved with local delivery. Consequently, efforts have been made toward the development of innovative methods of administration, and in the formulation and engineering of novel Abs to improve their therapeutic index. Objective: This review presents an overview of the routes of administration used to deliver Abs, different from the IV route, whether approved or in the clinical evaluation stage. We provide a description of the physical and biological fundamentals for each route of administration, highlighting their relevance with examples of clinically-relevant Abs, and discussing their strengths and limitations. Methods: We reviewed and analyzed the current literature, published as of the 1 April 2022 using MEDLINE and EMBASE databases, as well as the FDA and EMA websites. Ongoing trials were identified using clinicaltrials.gov. Publications and data were identified using a list of general keywords. Conclusions: Apart from the most commonly used IV route, topical delivery of Abs has shown clinical successes, improving drug bioavailability and efficacy while reducing side-effects. However, additional research is necessary to understand the consequences of biological barriers associated with local delivery for Ab partitioning, in order to optimize delivery methods and devices, and to adapt Ab formulation to local delivery. Novel modes of administration for Abs might in fine allow a better support to patients, especially in the context of chronic diseases, as well as a reduction of the treatment cost.

Retinoic Acid-Inducible Gene I Activation Inhibits Human Respiratory Syncytial Virus Replication in Mammalian Cells and in Mouse and Ferret Models of Infection

Infections caused by human respiratory syncytial virus (RSV) are associated with substantial rates of morbidity and mortality. Treatment options are limited, and there is urgent need for the development of efficient antivirals. Pattern recognition receptors such as the cytoplasmic helicase retinoic acid-inducible gene (RIG) I can be activated by viral nucleic acids, leading to activation of interferon-stimulated genes and generation of an "antiviral state." In the current study, we activated RIG-I with synthetic RNA agonists (3pRNA) to induce resistance to RSV infection in vitro and in vivo. In vitro, pretreatment of human, mouse, and ferret airway cell lines with RIG-I agonist before RSV exposure inhibited virus infection and replication. Moreover, a single intravenous injection of 3pRNA 1 day before RSV infection resulted in potent inhibition of virus replication in the lungs of mice and ferrets, but not in nasal tissues. These studies provide evidence that RIG-I agonists represent a promising antiviral drug for RSV prophylaxis.

A Virus Is a Community: Diversity within Negative-Sense RNA Virus Populations

Negative-sense RNA virus populations are composed of diverse viral components that interact to form a community and shape the outcome of virus infections. At the genomic level, RNA virus populations consist not only of a homogeneous population of standard viral genomes but also of an extremely large number of genome variants, termed viral quasispecies, and nonstandard viral genomes, which include copy-back viral genomes, deletion viral genomes, mini viral RNAs, and hypermutated RNAs. At the particle level, RNA virus populations are composed of pleomorphic particles, particles missing or having additional genomes, and single particles or particle aggregates. As we continue discovering more about the components of negative-sense RNA virus populations and their crucial functions during virus infection, it will become more important to study RNA virus populations as a whole rather than their individual parts. In this review, we will discuss what is known about the components of negative-sense RNA virus communities, speculate how the components of the virus community interact, and summarize what vaccines and antiviral therapies are being currently developed to target or harness these components.

Probenecid Inhibits Respiratory Syncytial Virus (RSV) Replication

RNA viruses like SARS-CoV-2, influenza virus, and respiratory syncytial virus (RSV) are dependent on host genes for replication. We investigated if probenecid, an FDA-approved and safe urate-lowering drug that inhibits organic anion transporters (OATs) has prophylactic or therapeutic efficacy to inhibit RSV replication in three epithelial cell lines used in RSV studies, i.e., Vero E6 cells, HEp-2 cells, and in primary normal human bronchoepithelial (NHBE) cells, and in BALB/c mice. The studies showed that nanomolar concentrations of all probenecid regimens prevent RSV strain A and B replication in vitro and RSV strain A in vivo, representing a potential prophylactic and chemotherapeutic for RSV.

Anti-inflammatory effects of curcumin-loaded niosomes on respiratory syncytial virus infection in a mice model

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in paediatrics. While antivirals are apparent candidates to treat RSV-induced diseases, they have not yet met expectations and have remained in infancy. There is growing evidence to suggest that modulating the exacerbated inflammation during RSV infection can improve disease outcome. Curcumin-loaded niosomes have anti-inflammatory effects against RSV-induced respiratory disease by reducing immune cells' infiltration and inflammatory cytokines' production. This study evaluated the effects of curcumin-loaded niosomes on RSV-induced immunopathology in a mice model. Curcumin-loaded niosomes were prepared using the thin-film hydration method and characterized in vitro. Female Balb/c mice were infected by RSV-A2 and treated daily with curcumin-loaded niosomes. The potential anti-inflammatory effects of curcumin-loaded niosomes were evaluated on day 5 after infection. Using curcumin-loaded niosomes decreased immune cell influx and the inflammatory mediators (MIP-1α, TNF-α and IFN-γ) production in the lung, resulting in alleviated lung pathology following RSV infection. These findings indicate that curcumin-loaded niosomes have anti-inflammatory potential and could be a promising candidate to alleviate RSV-associated immunopathology.

Metabolic Modifications by Common Respiratory Viruses and Their Potential as New Antiviral Targets

Respiratory viruses are known to be the most frequent causative mediators of lung infections in humans, bearing significant impact on the host cell signaling machinery due to their host-dependency for efficient replication. Certain cellular functions are actively induced by respiratory viruses for their own benefit. This includes metabolic pathways such as glycolysis, fatty acid synthesis (FAS) and the tricarboxylic acid (TCA) cycle, among others, which are modified during viral infections. Here, we summarize the current knowledge of metabolic pathway modifications mediated by the acute respiratory viruses respiratory syncytial virus (RSV), rhinovirus (RV), influenza virus (IV), parainfluenza virus (PIV), coronavirus (CoV) and adenovirus (AdV), and highlight potential targets and compounds for therapeutic approaches.

Antivirals against the Chikungunya Virus

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has re-emerged in recent decades, causing large-scale epidemics in many parts of the world. CHIKV infection leads to a febrile disease known as chikungunya fever (CHIKF), which is characterised by severe joint pain and myalgia. As many patients develop a painful chronic stage and neither antiviral drugs nor vaccines are available, the development of a potent CHIKV inhibiting drug is crucial for CHIKF treatment. A comprehensive summary of current antiviral research and development of small-molecule inhibitor against CHIKV is presented in this review. We highlight different approaches used for the identification of such compounds and further discuss the identification and application of promising viral and host targets.

Respiratory syntycial virus: Current treatment strategies and vaccine approaches

Respiratory Syncytial Virus is a yearly respiratory virus that causes significant frequencies of morbidities, particularly in the young and elderly populations. However, preventive vaccines and/or treatment therapies are generally lacking, although much attention is now being placed on this virus. Moreover, there are now multiple strategies currently being explored in a race to the first licensed vaccine. While vaccines are being developed, multiple treatment strategies are being explored to attenuate the severity of infection and thus reduce hospitalization rates in vulnerable populations. This review outlines current strategies to prevent or treat this virus in the hopes of reducing significant human morbidity and mortality that occurs yearly with this seasonal virus.

Designing of Potential Polyvalent Vaccine Model for Respiratory Syncytial Virus by System Level Immunoinformatics Approaches

BACKGROUND

Respiratory syncytial virus (RSV) infection is a public health epidemic, leading to around 3 million hospitalization and about 66,000 deaths each year. It is a life-threatening condition exclusive to children with no effective treatment.

METHODS

In this study, we used system-level and vaccinomics approaches to design a polyvalent vaccine for RSV, which could stimulate the immune components of the host to manage this infection. Our framework involves data accession, antigenicity and subcellular localization analysis, T cell epitope prediction, proteasomal and conservancy evaluation, host-pathogen-protein interactions, pathway studies, and in silico binding affinity analysis.

RESULTS

We found glycoprotein (G), fusion protein (F), and small hydrophobic protein (SH) of RSV as potential vaccine candidates. Of these proteins (G, F, and SH), we found 9 epitopes for multiple alleles of MHC classes I and II bear significant binding affinity. These potential epitopes were linked to form a polyvalent construct using AAY, GPGPG linkers, and cholera toxin B adjuvant at N-terminal with a 23.9 kDa molecular weight of 224 amino acid residues. The final construct was a stable, immunogenic, and nonallergenic protein containing cleavage sites, TAP transport efficiency, posttranslation shifts, and CTL epitopes. The molecular docking indicated the optimum binding affinity of RSV polyvalent construct with MHC molecules (-12.49 and -10.48 kcal/mol for MHC classes I and II, respectively). This interaction showed that a polyvalent construct could manage and control this disease.

CONCLUSION

Our vaccinomics and system-level investigation could be appropriate to trigger the host immune system to prevent RSV infection.

Humoral and Mucosal Antibody Response to RSV Structural Proteins in RSV-Infected Adult Hematopoietic Cell Transplant (HCT) Recipients

Respiratory syncytial virus (RSV) is an important cause of lower respiratory tract infection in infants, the elderly, and immunocompromised patients. RSV antibodies play a role in preventing reinfection and in clearance of RSV, but data regarding the levels of viral protein-specific antibodies elicited and their contribution to patient recovery from RSV-induced disease are limited. We prospectively enrolled a cohort of RSV-infected adult hematopoietic cell transplant (HCT) recipients (n = 40). Serum and nasal-wash samples were obtained at enrollment (acute samples) and convalescence (convalescent samples). We measured (1) humoral IgG and mucosal IgA binding antibody levels to multiple RSV proteins (F, G, N, P, and M2-1) by Western blot (WB); (2) neutralizing antibody (Nt Ab) titers by microneutralization assay; and (3) palivizumab-like antibody (PLA) concentrations by an ELISA-based competitive binding assay developed in the lab. Finally, we tested for correlations between protein-specific antibody levels and duration of viral shedding (normal: cleared in <14 days and delayed: cleared ≥14 days), as well as RSV/A and RSV/B subtypes. Convalescent sera from HCT recipients had significantly higher levels of anti-RSV antibodies to all 5 RSV structural proteins assayed (G, F, N, P, M2-1), higher Nt Abs to both RSV subtypes, and higher serum PLAs than at enrollment. Significantly higher levels of mucosal antibodies to 3 RSV structural proteins (G, N, and M2-1) were observed in the convalescent nasal wash versus acute nasal wash. Normal viral clearance group had significantly higher levels of serum IgG antibodies to F, N, and P viral proteins, higher Nt Ab to both RSV subtypes, and higher PLA, as well as higher levels of mucosal IgA antibodies to G and M2-1 viral proteins, and higher Nt Ab to both RSV subtypes compared to delayed viral clearance group. Normal RSV clearance was associated with higher IgG serum antibody levels to F and P viral proteins, and PLAs in convalescent serum (p < 0.05). Finally, overall antibody levels in RSV/A- and/B-infected HCT recipients were not significantly different. In summary, specific humoral and mucosal RSV antibodies are associated with viral clearance in HCT recipients naturally infected with RSV. In contrast to the humoral response, the F surface glycoprotein was not a major target of mucosal immunity. Our findings have implications for antigen selection in the development of RSV vaccines.

Development of a respiratory syncytial virus vaccine using human hepatitis B core-based virus-like particles to induce mucosal immunity

BACKGROUND

Respiratory syncytial virus (RSV) is an important viral pathogen responsible for severe infection of the lower respiratory tract in children under the age of 5 years. No vaccines against RSV are currently in clinical use. Vaccine-associated enhanced respiratory disease (ERD) caused by excess Th2 type responses was observed in a clinical trial of formalin-inactivated RSV (FI-RSV) in antigen-naïve infants. Thus, inducing a balanced immune response is a crucial issue in the development of an RSV vaccine.

METHODS

In this study, we constructed, expressed, and purified a recombinant RSV vaccine candidate (i.e., HRØ24) containing the two heptad repeat regions and the antigenic sites Ø, II, and IV of the RSV F protein. The RSV vaccine candidate was intranasally administrated to BALB/c and C57BL/6 mice in combination with virus-like particles (VLPs) derived from the core protein of the hepatitis B virus (HBc). Mucosal immunity to HRØ24 was then assessed.

RESULTS

Intranasal administration of HBc VLPs in combination with HRØ24 induced serum IgGs against HRØ24 as well as lung HRØ24-specific sIgAs in both C57BL/6 and BALB/c mouse models. The secretion of IFN-γ from splenocyte re-stimulation and an elevated ratio of serum IgG2a to IgG1 indicated that the immune response induced by the HBc VLPs/HRØ24 mixture was Th1-biased. Weight loss of <5% and no to low eosinophil infiltration was observed in histological analysis of the lung following a challenge with the RSV A2 strain. These results suggest that the HBc VLPs/HRØ24 combination conferred substantial partial protection against RSV-induced illness in mice.

CONCLUSIONS

Long-term immunity to RSV-induced illness was achieved via intranasal vaccination using a mixture of HBc VLPs and HRØ24 in mouse models.

Thapsigargin Is a Broad-Spectrum Inhibitor of Major Human Respiratory Viruses: Coronavirus, Respiratory Syncytial Virus and Influenza A Virus

The long-term control strategy of SARS-CoV-2 and other major respiratory viruses needs to include antivirals to treat acute infections, in addition to the judicious use of effective vaccines. Whilst COVID-19 vaccines are being rolled out for mass vaccination, the modest number of antivirals in use or development for any disease bears testament to the challenges of antiviral development. We recently showed that non-cytotoxic levels of thapsigargin (TG), an inhibitor of the sarcoplasmic/endoplasmic reticulum (ER) Ca2+ ATPase pump, induces a potent host innate immune antiviral response that blocks influenza A virus replication. Here we show that TG is also highly effective in blocking the replication of respiratory syncytial virus (RSV), common cold coronavirus OC43, SARS-CoV-2 and influenza A virus in immortalized or primary human cells. TG's antiviral performance was significantly better than remdesivir and ribavirin in their respective inhibition of OC43 and RSV. Notably, TG was just as inhibitory to coronaviruses (OC43 and SARS-CoV-2) and influenza viruses (USSR H1N1 and pdm 2009 H1N1) in separate infections as in co-infections. Post-infection oral gavage of acid-stable TG protected mice against a lethal influenza virus challenge. Together with its ability to inhibit the different viruses before or during active infection, and with an antiviral duration of at least 48 h post-TG exposure, we propose that TG (or its derivatives) is a promising broad-spectrum inhibitor against SARS-CoV-2, OC43, RSV and influenza virus.

Inhibition of viral RNA-dependent RNA polymerases with clinically relevant nucleotide analogs

The treatment of viral infections remains challenging, in particular in the face of emerging pathogens. Broad-spectrum antiviral drugs could potentially be used as a first line of defense. The RNA-dependent RNA polymerase (RdRp) of RNA viruses serves as a logical target for drug discovery and development efforts. Herein we discuss compounds that target RdRp of poliovirus, hepatitis C virus, influenza viruses, respiratory syncytial virus, and the growing data on coronaviruses. We focus on nucleotide analogs and mechanisms of action and resistance.

Recent updates on COVID-19: A holistic review

Coronaviruses are large positive-sense RNA viruses with spike-like peplomers on their surface. The Coronaviridae family's strains infect different animals and are popularly associated with several outbreaks, namely SARS and MERS epidemic. COVID-19 is one such recent outbreak caused by SARS-CoV-2 identified first in Wuhan, China. COVID-19 was declared a pandemic by WHO on 11th March 2020. Our review provides information covering various facets of the disease starting from its origin, transmission, mutations in the virus to pathophysiological changes in the host upon infection followed by diagnostics and possible therapeutics available to tackle the situation. We have highlighted the zoonotic origin of SARS-CoV-2, known to share 96.2% nucleotide similarity with bat coronavirus. Notably, several mutations in SARS-CoV-2 spike protein, nucleocapsid protein, PLpro, and ORF3a are reported across the globe. These mutations could alter the usual receptor binding function, fusion process with the host cell, virus replication, and the virus's assembly. Therefore, studying these mutations could help understand the virus's virulence properties and design suitable therapeutics. Moreover, the aggravated immune response to COVID-19 can be fatal. Hypertension, diabetes, and cardiovascular diseases are comorbidities substantially associated with SARS-CoV-2 infection. The review article discusses these aspects, stating the importance of various comorbidities in disease outcomes. Furthermore, medications' unavailability compels the clinicians to opt for atypical drugs like remdesivir, chloroquine, etc. The current diagnostics of COVID-19 include qRT-PCR, CT scan, serological tests, etc. We have described these aspects to expose the information to the scientific community and to accelerate the research.

Serum 25-Hydroxy Vitamin D Levels in Japanese Infants with Respiratory Syncytial Virus Infection Younger than 3 Months of Age

Low blood levels of vitamin D have been reported in children who have frequent respiratory tract infections. We measured serum concentrations of 25-hydroxy (OH) vitamin D in Japanese infants under 3 months of age who had respiratory syncytial virus (RSV) infection. Serum levels of 25-OH vitamin D in the 10 infants, excluding those with underlying diseases, were between < 4 and 29.8 ng/mL. In 8 out of 10 subjects (80.0%), serum 25-OH vitamin D levels were lower than 20 ng/mL. There was no statistically significant association between the levels of 25-OH vitamin D and age, duration of admission, respiratory severity score, white blood cell count, blood gas levels, and N-terminal pro-natriuretic peptide levels. Levels of serum 25-OH vitamin D in children who required hospitalization owing to RSV infection were low, indicating deficiency. These results suggest that vitamin D deficiency affects the susceptibility to RSV infection, but not the severity of the infection.

Pharmacological management of human respiratory syncytial virus infection

INTRODUCTION

Human respiratory syncytial virus (hRSV) is the primary viral cause of respiratory diseases, leading to bronchiolitis and pneumonia in vulnerable populations. The only current treatment against this virus is palliative, and no efficient and specific vaccine against this pathogen is available.

AREAS COVERED

The authors describe the disease symptoms caused by hRSV, the economic and social impact of this infection worldwide, and how this infection can be modulated using pharmacological treatments, preventing and limiting its dissemination. The authors discuss the use of antibodies as prophylactic tools -such as palivizumab- and the use of nonspecific drugs to decrease the symptoms associated with the infection -such as bronchodilators, corticoids, and antivirals. They also discuss current vaccine candidates, new prophylactic treatments, and new antivirals options, which are currently being tested.

EXPERT OPINION

Today, many researchers are focused on developing different strategies to modulate the symptoms induced by hRSV. However, to achieve this, understanding how current treatments are working and their shortcomings needs to be further elucidated.

A Cell-Based Reporter Assay for Screening Inhibitors of MERS Coronavirus RNA-Dependent RNA Polymerase Activity

Severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and coronavirus disease 2019 (COVID-19) are emerging zoonotic diseases caused by coronavirus (CoV) infections. The viral RNA-dependent RNA polymerase (RdRp) has been suggested as a valuable target for antiviral therapeutics because the sequence homology of CoV RdRp is highly conserved. We established a cell-based reporter assay for MERS-CoV RdRp activity to test viral polymerase inhibitors. The cell-based reporter system was composed of the bicistronic reporter construct and the MERS-CoV nsp12 plasmid construct. Among the tested nine viral polymerase inhibitors, ribavirin, sofosbuvir, favipiravir, lamivudine, zidovudine, valacyclovir, vidarabine, dasabuvir, and remdesivir, only remdesivir exhibited a dose-dependent inhibition. Meanwhile, the Z-factor and Z'-factor of this assay for screening inhibitors of MERS-CoV RdRp activity were 0.778 and 0.782, respectively. Ribavirin and favipiravir did not inhibit the MERS-CoV RdRp activity, and non-nucleoside HCV RdRp inhibitor, dasabuvir, partially inhibited MERS-CoV RdRp activity. Taken together, the cell-based reporter assay for MERS-CoV RdRp activity confirmed remdesivir as a direct inhibitor of MERS-CoV RdRp in cells. A cell-based MERS-CoV RdRp activity reporter assay is reliable and accurate for screening MERS-CoV RdRp-specific inhibitors. It may provide a valuable platform for developing antiviral drugs for emerging CoV infections.

Accelerated Discovery of Potent Fusion Inhibitors for Respiratory Syncytial Virus

A series of five benzimidazole-based compounds were identified using a machine learning algorithm as potential inhibitors of the respiratory syncytial virus (RSV) fusion protein. These compounds were synthesized, and compound 2 in particular exhibited excellent in vitro potency with an EC₅₀ value of 5 nM. This new scaffold was then further refined leading to the identification of compound 44, which exhibited a 10-fold improvement in activity with an EC₅₀ value of 0.5 nM.

Innate Type 2 Responses to Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is a common and contagious virus that results in acute respiratory tract infections in infants. In many cases, the symptoms of RSV remain mild, however, a subset of individuals develop severe RSV-associated bronchiolitis. As such, RSV is the chief cause of infant hospitalization within the United States. Typically, the immune response to RSV is a type 1 response that involves both the innate and adaptive immune systems. However, type 2 cytokines may also be produced as a result of infection of RSV and there is increasing evidence that children who develop severe RSV-associated bronchiolitis are at a greater risk of developing asthma later in life. This review summarizes the contribution of a newly described cell type, group 2 innate lymphoid cells (ILC2), and epithelial-derived alarmin proteins that activate ILC2, including IL-33, IL-25, thymic stromal lymphopoietin (TSLP), and high mobility group box 1 (HMGB1). ILC2 activation leads to the production of type 2 cytokines and the induction of a type 2 response during RSV infection. Intervening in this innate type 2 inflammatory pathway may have therapeutic implications for severe RSV-induced disease.

Imiquimod suppresses respiratory syncytial virus (RSV) replication via PKA pathway and reduces RSV induced-inflammation and viral load in mice lungs

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease and bronchiolitis in children, as well as an important cause of morbidity and mortality in elderly and immunocompromised individuals. However, there is no safe and efficacious RSV vaccine or antiviral treatment. Toll Like Receptors (TLR) are important molecular mediators linking innate and adaptive immunity, and their stimulation by cognate agonists has been explored as antiviral agents. Imiquimod is known as a TLR7 agonist, but additionally acts as an antagonist for adenosine receptors. In this study, we demonstrate that imiquimod, but not resiquimod, has direct anti-RSV activity via PKA pathway in HEp-2 and A549 cells, independently of an innate response. Imiquimod restricts RSV infection after viral entry into the host cell, interfering with viral RNA and protein synthesis. Probably as a consequence of these anti-RSV properties, imiquimod displays cytokine modulating activity in RSV infected epithelial cells. Moreover, in a murine model of RSV infection, imiquimod treatment improves the course of acute disease, evidenced by decreased weight loss, reduced RSV lung titers, and attenuated airway inflammation. Consequently, imiquimod represents a promising therapeutic alternative against RSV infection and may inform the development of novel therapeutic targets to control RSV pathogenesis.

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Imiquimod has direct anti-RSV activity via PKA pathway, independently of an innate response.

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Imiquimod restricts RSV infection after viral entry into the host cell, interfering with viral RNA and protein synthesis.

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Imiquimod reduces cytokine production in RSV infected epithelial cells, probably as a result of its anti-RSV properties.

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Imiquimod reduces RSV lung titers and decreases weight loss and airway inflammation in a murine model of RSV infection.

Up-to-date role of biologics in the management of respiratory syncytial virus

INTRODUCTION

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease in young children and a substantial contributor to respiratory tract disease throughout life. Despite RSV being a high priority for vaccine development, there is currently no safe and effective vaccine available. There are many challenges to developing an RSV vaccine and there are limited antiviral drugs or biologics available for the management of infection. In this article, we review the antiviral treatments, vaccination strategies along with alternative therapies for RSV.

AREAS COVERED

This review is a summary of the current antiviral and RSV vaccination approaches noting strategies and alternative therapies that may prevent or decrease the disease severity in RSV susceptible populations.

EXPERT OPINION

This review discusses anti-RSV strategies given that no safe and efficacious vaccines are available, and therapeutic treatments are limited. Various biologicals that target for RSV are considered for disease intervention, as it is likely that it may be necessary to develop separate vaccines or therapeutics for each at-risk population.

Structural Insight into Paramyxovirus and Pneumovirus Entry Inhibition

Paramyxoviruses and pneumoviruses infect cells through fusion (F) protein-mediated merger of the viral envelope with target membranes. Members of these families include a range of major human and animal pathogens, such as respiratory syncytial virus (RSV), measles virus (MeV), human parainfluenza viruses (HPIVs), and highly pathogenic Nipah virus (NiV). High-resolution F protein structures in both the metastable pre- and the postfusion conformation have been solved for several members of the families and a number of F-targeting entry inhibitors have progressed to advanced development or clinical testing. However, small-molecule RSV entry inhibitors have overall disappointed in clinical trials and viral resistance developed rapidly in experimental settings and patients, raising the question of whether the available structural information may provide a path to counteract viral escape through proactive inhibitor engineering. This article will summarize current mechanistic insight into F-mediated membrane fusion and examine the contribution of structural information to the development of small-molecule F inhibitors. Implications are outlined for future drug target selection and rational drug engineering strategies.

Sex differences in blood pro-oxidant status and platelet activation in children admitted with respiratory syncytial virus bronchiolitis: a pilot study

Background

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in the pediatric population worldwide and an important cause of death in developing countries. It has been demonstrated that the balance between oxidant and antioxidant systems is disrupted in children with bronchiolitis and that oxidative stress contributes to the pathogenesis of this disease. Platelets play an important role in antimicrobial host defenses and contribute to pulmonary vascular repair being either targets or source of reactive oxidizing species. The main purpose of this study was to assessing sex differences in clinical characteristics and platelets activation during RSV bronchiolitis in infancy.

Methods

In this retrospective study a total of 203 patients (112 boys and 91 girls) with bronchiolitis, aged 12 months or less, admitted to the Bambino Gesù Pediatric Hospital of Rome (Italy) in the period from January to December 2017, were enrolled. Moreover, in a select group of patients (15 boys and 12 girls) with diagnosis of moderate bronchiolitis from RSV, a pilot study on oxidative stress and platelet characteristics was carried out by electron paramagnetic resonance and flow cytometry respectively. Age-matched healthy control subjects (10 boys and 10 girls) were chosen as controls. Data were analyzed using Student’ T test, Chi Squared test and one-way ANOVA test.

Results

This study highlights the influence of sex in the clinical course of bronchiolitis. In particular we found: i) a higher incidence of bronchiolitis in boys than in girls (55% vs 45%); ii) higher C reactive protein values in girls than boys (1.11 mg/dL vs 0.92 mg/dL respectively; p < 0.05); iii) a different degree of thrombocytosis during hospitalization (mild in the girls and severe in the boys). Moreover, in selected patients we found that compared to girls with bronchiolitis, boys showed: i) higher percentage of activated platelets (8% vs 2% respectively; p < 0.05) and iii) higher number of platelets forming homotypic aggregates (2.36% vs 0.84% respectively, p < 0.05).

Conclusion

The present study affirm that the bronchiolitis is an infection in which sex seems to act as a modulating factor only in the clinical course, influencing also the choice of the therapy should be made.

Sirtuin 1 regulates mitochondrial function and immune homeostasis in respiratory syncytial virus infected dendritic cells

Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infection in children worldwide. Sirtuin 1 (SIRT1), a NAD+ dependent deacetylase, has been associated with induction of autophagy, reprogramming cellular metabolism, and regulating immune mediators. In this study, we investigated the role of SIRT1 in bone marrow dendritic cell (BMDC) function during RSV infection. SIRT1 deficient (SIRT1 -/-) BMDC showed a defect in mitochondrial membrane potential (Δ⍦m) that worsens during RSV infection. This defect in Δ⍦m caused the generation of elevated levels of reactive oxygen species (ROS). Furthermore, the oxygen consumption rate (OCR) was reduced as assessed in Seahorse assays, coupled with lower levels of ATP in SIRT1-/- DC. These altered responses corresponded to altered innate cytokine responses in the SIRT1-/- DC in response to RSV infection. Reverse Phase Protein Array (RPPA) functional proteomics analyses of SIRT1-/- and WT BMDC during RSV infection identified a range of differentially regulated proteins involved in pathways that play a critical role in mitochondrial metabolism, autophagy, oxidative and ER stress, and DNA damage. We identified an essential enzyme, acetyl CoA carboxylase (ACC1), which plays a central role in fatty acid synthesis and had significantly increased expression in SIRT1-/- DC. Blockade of ACC1 resulted in metabolic reprogramming of BMDC that ameliorated mitochondrial dysfunction and reduced pathologic innate immune cytokines in DC. The altered DC responses attenuated Th2 and Th17 immunity allowing the appropriate generation of anti-viral Th1 responses both in vitro and in vivo during RSV infection thus reducing the enhanced pathogenic responses. Together, these studies identify pathways critical for appropriate DC function and innate immunity that depend on SIRT1-mediated regulation of metabolic processes.

Melittin: a venom-derived peptide with promising anti-viral properties

Despite tremendous advances in the development of anti-viral therapeutics, viral infections remain a chief culprit accounting for ongoing morbidity and mortality worldwide. Natural products, in particular animal venoms, embody a veritable cornucopia of exotic constituents, suggesting an immensurable source of anti-infective drugs. In this context, melittin, the principal constituent in the venom of the European honeybee Apis mellifera, has been demonstrated to exert anti-cancer, anti-inflammatory, anti-diabetic, anti-infective, and adjuvant properties. To our knowledge, there is no review appertaining to effects of melittin against viruses, prompting us to synopsize experimental investigations on its anti-viral activity throughout the past decades. Accumulating evidence indicates that melittin curbs infectivity of a diverse array of viruses including coxsackievirus, enterovirus, influenza A viruses, human immunodeficiency virus (HIV), herpes simplex virus (HSV), Junín virus (JV), respiratory syncytial virus (RSV), vesicular stomatitis virus (VSV), and tobacco mosaic virus (TMV). However, medication safety, different routes of administrations, and molecular mechanisms behind the anti-viral activity of melittin should be scrutinized in future studies.

Subversion of Host Cell Mitochondria by RSV to Favor Virus Production is Dependent on Inhibition of Mitochondrial Complex I and ROS Generation

Respiratory syncytial virus (RSV) is a key cause of severe respiratory infection in infants, immunosuppressed adults, and the elderly worldwide, but there is no licensed vaccine or effective, widely-available antiviral therapeutic. We recently reported staged redistribution of host cell mitochondria in RSV infected cells, which results in compromised respiratory activities and increased reactive oxygen species (ROS) generation. Here, bioenergetic measurements, mitochondrial redox-sensitive dye, and high-resolution quantitative imaging were performed, revealing for the first time that mitochondrial complex I is key to this effect on the host cell, whereby mitochondrial complex I subunit knock-out (KO) cells, with markedly decreased mitochondrial respiration, show elevated levels of RSV infectious virus production compared to wild-type cells or KO cells with re-expressed complex I subunits. This effect correlates strongly with elevated ROS generation in the KO cells compared to wild-type cells or retrovirus-rescued KO cells re-expressing complex I subunits. Strikingly, blocking mitochondrial ROS levels using the mitochondrial ROS scavenger, mitoquinone mesylate (MitoQ), inhibits RSV virus production, even in the KO cells. The results highlight RSV's unique ability to usurp host cell mitochondrial ROS to facilitate viral infection and reinforce the idea of MitoQ as a potential therapeutic for RSV.

Differential antiviral activities of respiratory syncytial virus (RSV) inhibitors in human airway epithelium

Objectives

We report the use of reconstituted 3D human airway epithelium cells (HuAECs) of bronchial origin in an air–liquid interface to study respiratory syncytial virus (RSV) infection and to assess the efficacy of RSV inhibitors in (pre-)clinical development.

Methods

HuAECs were infected with RSV-A Long strain (0.01 CCID₅₀/cell, where CCID₅₀ represents 50% cell culture infectious dose in HEp2 cells) on the apical compartment of the culture. At the time of infection or at 1 or 3 days post-infection, selected inhibitors were added and refreshed daily on the basal compartment of the culture. Viral shedding was followed up by apical washes collected daily and quantifying viral RNA by RT-qPCR.

Results

RSV-A replicates efficiently in HuAECs and viral RNA is shed for weeks after infection. RSV infection reduces the ciliary beat frequency of the ciliated cells as of 4 days post-infection, with complete ciliary dyskinesia observed by day 10. Treatment with RSV fusion inhibitors resulted in an antiviral effect only when added at the time of infection. In contrast, the use of replication inhibitors (both nucleoside and non-nucleoside) elicited a marked antiviral effect even when the start of treatment was delayed until 1 day or even 3 days after infection. Levels of the inflammation marker RANTES (mRNA) increased ∼200-fold in infected, untreated cultures (at 3 weeks post-infection), but levels were comparable to those of uninfected cultures in the presence of PC786, an RSV replication inhibitor, suggesting that an efficient antiviral treatment might inhibit virus-induced inflammation in this model.

Conclusions

Overall, HuAECs offer a robust and physiologically relevant model to study RSV replication and to assess the efficacy of antiviral compounds.

Immunoglobulin treatment for hospitalised infants and young children with respiratory syncytial virus infection

BACKGROUND

Millions of children are hospitalised due to respiratory syncytial virus (RSV) infection every year. Treatment is supportive, and current therapies (e.g. inhaled bronchodilators, epinephrine, nebulised hypertonic saline, and corticosteroids) are ineffective or have limited effect. Respiratory syncytial virus immunoglobulin is sometimes used prophylactically to prevent hospital admission from RSV-related illness. It may be considered for the treatment of established severe RSV infection or for treatment in an immunocompromised host, although it is not licenced for this purpose. It is unclear whether immunoglobulins improve outcomes when used as a treatment for established RSV infection in infants and young children admitted to hospital.  OBJECTIVES: To assess the effects of immunoglobulins for the treatment of RSV-proven lower respiratory tract infections in children aged up to three years, admitted to hospital.  SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, Ovid MEDLINE, Embase, CINAHL, and Web of Science (from inception to 6 November 2018) with no restrictions. We searched two trial registries for ongoing trials (to 30 March 2018) and checked the reference lists of reviews and included articles for additional studies.

SELECTION CRITERIA

Randomised controlled trials comparing immunoglobulins with placebo in hospitalised infants and children aged up to three years with laboratory-diagnosed RSV lower respiratory tract infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed risk of bias, and extracted data. We assessed evidence quality using GRADE.

MAIN RESULTS

We included seven trials involving 486 infants and children aged up to three years. The immunoglobulin preparations used in these trials included anti-RSV immunoglobulin and the monoclonal antibody preparations palivizumab and motavizumab. We assessed the primary outcomes of mortality, length of hospital stay, and adverse events as providing low- or very low-certainty evidence due to risk of bias and imprecision. All trials were conducted at sites in high-income countries (USA, Chile, New Zealand, Australia), with two studies including a site in a middle-income country (Panama). Five of the seven studies were "supported" or "sponsored" by the trial drug manufacturers. We found no evidence of a difference between immunoglobulins and placebo for mortality (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.14 to 5.27; 3 trials; 196 children; 4 deaths; 2 deaths amongst 98 children receiving immunoglobulins, and 2 deaths amongst 98 children receiving placebo. One additional death occurred in a fourth trial, however, the study group of the child was not known and the data were not included in the analysis; very low-certainty evidence), and length of hospitalisation (mean difference -0.70, 95% CI -1.83 to 0.42; 5 trials; 324 children; low-certainty evidence). There was no evidence of a difference between immunoglobulins and placebo in adverse events of any severity or seriousness (reported in five trials) or serious adverse events (four trials) (RR for any severity 1.18, 95% CI 0.78 to 1.78; 340 children; low-certainty evidence, and for serious adverse events 1.08, 95% CI 0.65 to 1.79; 238 children; low-certainty evidence).We found no evidence of a significant difference between immunoglobulins and placebo for any of our secondary outcomes. We identified one ongoing trial.

AUTHORS' CONCLUSIONS

We found insufficient evidence of a difference between immunoglobulins and placebo for any review outcomes. We assessed the evidence for the effects of immunoglobulins when used as a treatment for RSV lower respiratory tract infection in hospitalised infants and young children as of low or very low certainty due to risk of bias and imprecision. We are uncertain of the effects of immunoglobulins on these outcomes, and the true effect may be substantially different from the effects reported in this review. All trials were conducted in high-income countries, and data from populations in which the rate of death from RSV infection is higher are lacking.

Respiratory syncytial virus prefusogenic fusion (F) protein nanoparticle vaccine: Structure, antigenic profile, immunogenicity, and protection

Respiratory syncytial virus (RSV) is a major cause of severe respiratory disease in the very young, elderly, and immunocompromised for which there is no vaccine. The surface exposed RSV fusion (F) glycoprotein is required for membrane fusion and infection and is a desirable vaccine candidate. RSV F glycoprotein structure is dynamic and undergoes significant rearrangements during virus assembly, fusion, and infection. We have previously described an RSV fusion-inactive prefusogenic F with a mutation of one of two furin cleavage sites resulting in the p27 region on the N-terminus of F1 with a truncated fusion peptide covalently linked to F2. A processing intermediate RSV prefusogenic F has been reported in infected cells, purified F, budded virus, and elicited a strong immune response against p27 in RSV infected young children. In this report, we demonstrate that prefusogenic F, when expressed on the cell surface of Sf9 insect and human 293T cells, binds monoclonal antibodies (mAbs) that target prefusion-specific antigenic sites Ø and VIII, and mAbs targeting epitopes common to pre- and postfusion F sites II and IV. Purified prefusogenic F bound prefusion F specific mAbs to antigenic sites Ø and VIII and mAbs targeting pre- and postfusion sites II, IV, and p27. Mice immunized with prefusogenic F antigen produced significantly higher levels of anti-F IgG and RSV neutralizing antibodies than prefusion or postfusion F antigens and induced antibodies competitive with mAbs to sites Ø, VIII, II, and IV. RSV prefusogenic F neutralization antibody responses were enhanced with aluminum phosphate adjuvant and significantly higher than prefusion F. Prefusogenic F vaccine protected cotton rats against upper and lower respiratory tract infection by RSV/A. For the first time, we present the structure, antigenic profile, immunogenicity, and protective efficacy of RSV prefusogenic F nanoparticle vaccine.

Antibiotic Minocycline Prevents Respiratory Syncytial Virus Infection

Treatment drugs, besides their specific activity, often have multiple effects on the body. The undesired effect of the drug may be repurposed as therapeutics, saving significant investigative time and effort. Minocycline has anti-cancer, anti-oxidant, anti-inflammatory, and anti-apoptotic properties. Presently, minocycline is also known to show anti-viral activity against Influenza virus, Japanese encephalitis virus, Simian immunodeficiency virus, Human immunodeficiency virus and West Nile virus. Here, we investigate the effect of minocycline on Respiratory syncytial virus (RSV), a common respiratory virus that causes severe mortality and morbidity in infants, children, and older adult populations. Currently, there is no effective vaccine or treatment for RSV infection; hence, there is a critical need for alternative and effective drug choices. Our study shows that minocycline reduces the RSV-mediated cytopathic effect and prevents RSV infection. This is the first study demonstrating the anti-viral activity of minocycline against RSV.

Palivizumab and prevention of childhood respiratory syncytial viral infection: protocol for a systematic review and meta-analysis of breakthrough infections

INTRODUCTION

Childhood respiratory syncytial virus (RSV) infection is a global phenomenon that can lead to fatal respiratory illness. Palivizumab is a drug that is routinely used in affluent countries as a prophylaxis against RSV infection; nevertheless, breakthrough infections are often reported. In light of new findings on potential RSV resistance to palivizumab, an up-to-date synthesis of evidence on effectiveness is needed. Furthering existing reviews, a broadened scope to better reflect effectiveness in a 'real world' clinical context is also important. This systematic review and meta-analysis will enhance our understanding of the effectiveness of palivizumab in varying populations of children. Findings from this review will inform recommendations for best practices regarding palivizumab use for childhood RSV infection as well as research priorities in RSV vaccine development.

METHODS AND ANALYSIS

We will conduct a systematic review of primary population-based studies that examine the incidence of palivizumab breakthrough infections in children, published between 1997 to present. In collaboration with a research librarian, four electronic databases (MEDLINE, Embase, Cochrane Library, Web of Science) and additional sources will be searched. Study screening and quality assessment will be performed in duplicate. Data will be extracted by one reviewer, with partial and random verification by a second reviewer. The primary outcomes to assess breakthrough RSV infection will be hospitalisation, length of stay and the need for intensive care unit admission and mechanical ventilation in children receiving palivizumab. The secondary outcome will be RSV-associated mortality. We will conduct a meta-analysis using pooled effectiveness data, and include subgroup analyses by patient comorbidities and drug compliance. Sensitivity analyses for risk of bias and study design will also be performed.

ETHICS AND DISSEMINATION

This systematic review will only include data from previously published literature and is therefore exempt from ethics approval. Final results will be disseminated through peer-reviewed publication and presented at academic conferences and scientific meetings engaging paediatric researchers and healthcare providers. Should findings from this review necessitate updates to current clinical practice guidelines, we intend to establish a working group to engage relevant health administrators and decision makers.

PROSPERO REGISTRATION NUMBER

CRD42019122120.

Alternative conformations of a major antigenic site on RSV F

The respiratory syncytial virus (RSV) fusion (F) glycoprotein is a major target of neutralizing antibodies arising from natural infection, and antibodies that specifically bind to the prefusion conformation of RSV F generally demonstrate the greatest neutralization potency. Prefusion-stabilized RSV F variants have been engineered as vaccine antigens, but crystal structures of these variants have revealed conformational differences in a key antigenic site located at the apex of the trimer, referred to as antigenic site Ø. Currently, it is unclear if flexibility in this region is an inherent property of prefusion RSV F or if it is related to inadequate stabilization of site Ø in the engineered variants. Therefore, we set out to investigate the conformational flexibility of antigenic site Ø, as well as the ability of the human immune system to recognize alternative conformations of this site, by determining crystal structures of prefusion RSV F bound to neutralizing human-derived antibodies AM22 and RSD5. Both antibodies bound with high affinity and were specific for the prefusion conformation of RSV F. Crystal structures of the complexes revealed that the antibodies recognized distinct conformations of antigenic site Ø, each diverging at a conserved proline residue located in the middle of an α-helix. These data suggest that antigenic site Ø exists as an ensemble of conformations, with individual antibodies recognizing discrete states. Collectively, these results have implications for the refolding of pneumovirus and paramyxovirus fusion proteins and should inform development of prefusion-stabilized RSV F vaccine candidates.

The Impact of RSV-Associated Respiratory Disease on Children in Asia

Acute respiratory tract infections (ARTIs) are leading contributors to the global infectious disease burden, which is estimated to be 112,900,000 disability adjusted life years. Viruses contribute to the etiology of ARTIs in a big way compared with other microorganisms. Since the discovery of respiratory syncytial virus (RSV) 61 years ago, the virus has been recognized as a major cause of ARTI and hospitalization in children. The morbidity and mortality attributable to RSV infection appear to be higher in infants < 3 months and in those with known risk factors such as prematurity, chronic lung, and congenital heart diseases. Crowded living conditions, exposure to tobacco smoke, and industrial or other types of air pollution also increase the risk of RSV-associated ARTI. Many epidemiological studies have been conducted in developed countries to understand the seasonal patterns and risk factors associated with RSV infections. Dearth of information on RSV-associated morbidity and mortality in Asian and developing countries indicates the need for regional reviews to evaluate RSV-associated disease burden in these countries. Epidemiological studies including surveillance is the key to track the disease burden including risk factors, seasonality, morbidity, and mortality associated with RSV infection in these countries. These data will contribute to improve the clinical diagnosis and plan preventive strategies in resource-limited developing countries.

Prevalence and characteristics of acute respiratory virus infections in pediatric cancer patients

Background

Patients with pediatric cancer have a higher risk of morbidity and mortality because of respiratory viral infections than other patient populations.

Objectives

To investigate the causative viruses of respiratory infections and their burden among patients with pediatric cancer in Lebanon.

Study design

Nasopharyngeal swabs along with clinical and demographic data were collected from patients with pediatric cancer presenting febrile episodes with upper respiratory tract symptoms. Total nucleic acid was extracted from specimens followed by the real‐time PCR analysis targeting 14 respiratory viruses to estimate the frequency of infections.

Results

We obtained 89 nasopharyngeal swabs from patients with pediatric cancer (mean age, 5.8 ± 4.2 years). Real‐time PCR confirmed viral infection in 77 swabs (86.5%). Among these, 151 respiratory viruses were detected. Several viruses cocirculated within the same period; respiratory syncytial virus (RSV) being the most common (45.45%), followed by parainfluenza virus (PIV; 26%), influenza type B (26%), human metapneumovirus (24.6%), and human coronavirus (HCoV; 24.6%). Coinfections were detected in 55% of the subjects, and most of them involved RSV with one or more other viruses. A strong correlation was found between PIV, Flu (influenza of any type), RSV, and HCoV with the incidence of coinfections. RSV was associated with lower respiratory tract infections, nasal congestion, bronchitis, and bacteremia. HCoV was associated with bronchiolitis; rhinovirus was associated with hospital admission.

Conclusion

Patients with pediatric cancer have a high burden of respiratory viral infections and a high incidence of coinfections. Molecular diagnostics can improve management of febrile episodes and reduce antibiotic use.

Respiratory viruses are leading cause of ARTI in pediatric cancer patients.

Coinfections are common among febrile pediatric cancer patients.

RSV was the most common in mono‐ and coinfections among pediatric cancer patients.

RSV, PIV, Flu, HCoV are associated with coinfections.

Molecular diagnostics permit rapid and sensitive diagnostics and limit antibiotic abuse.

Evaluation of the Antiviral Activity of Sephin1 Treatment and Its Consequences on eIF2α Phosphorylation in Response to Viral Infections

The guanabenz derivative Sephin1 has recently been proposed to increase the levels of translation initiation factor 2 (eIF2α) phosphorylation by inhibiting dephosphorylation by the protein phosphatase 1-GADD34 (PPP1R15A) complex. As phosphorylation of eIF2α by protein kinase R (PKR) is a prominent cellular antiviral pathway, we evaluated the consequences of Sephin1 treatment on virus replication. Our results provide evidence that Sephin1 downregulates replication of human respiratory syncytial virus, measles virus, human adenovirus 5 virus, human enterovirus D68, human cytomegalovirus, and rabbit myxoma virus. However, Sephin1 proved to be inactive against influenza virus, as well as against Japanese encephalitis virus. Sephin1 increased the levels of phosphorylated eIF2α in cells exposed to a PKR agonist. By contrast, in virus-infected cells, the levels of phosphorylated eIF2α did not always correlate with the inhibition of virus replication by Sephin1. This work identifies Sephin1 as an antiviral molecule in cell culture against RNA, as well as DNA viruses belonging to phylogenetically distant families.