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

Anti-G protein antibodies targeting the RSV G protein CX3C chemokine region improve the interferon response

Background

Respiratory syncytial virus (RSV) is a poor inducer of antiviral interferon (IFN) responses which result in incomplete immunity and RSV disease. Several RSV proteins alter antiviral responses, including the non-structural proteins (NS1, NS2) and the major viral surface proteins, that is, fusion (F) and attachment (G) proteins. The G protein modifies the host immune response to infection linked in part through a CX3 C chemokine motif. Anti-G protein monoclonal antibodies (mAbs), that is, clones 3D3 and 2D10 that target the G protein CX3C chemokine motif can neutralize RSV and inhibit G protein-CX3CR1 mediated chemotaxis.

Objectives

Determine how monoclonal antibodies against the RSV F and G proteins modify the type I and III IFN responses to RSV infection.

Design

As the G protein CX3 C motif is implicated in IFN antagonism, we evaluated two mAbs that block G protein CX3C-CX3CR1 interaction and compared responses to isotype mAb control using a functional cellular assay and mouse model.

Methods

Mouse lung epithelial cells (MLE-15 cells) and BALB/c mice were infected with RSV Line19 F following prophylactic mAb treatment. Cell supernatant or bronchoalveolar lavage fluid (BALF) were assayed for types I and III IFNs. Cells were interrogated for changes in IFN-related gene expression.

Results

Treatment with an anti-G protein mAb (3D3) resulted in improved IFN responses compared with isotype control following infection with RSV, partially independently of neutralization, and this was linked to upregulated SOCS1 expression.

Conclusions

These findings show that anti-G protein antibodies improve the protective early antiviral response, which has important implications for vaccine and therapeutic design.

Plain Language Summary

RSV is a leading cause of respiratory disease in infants and the elderly. The only Food and Drug Administration-approved prophylactic treatment is limited to an anti-F protein monoclonal antibody (mAb), that is, palivizumab which has modest efficacy against RSV disease. Accumulating evidence suggests that targeting the RSV attachment (G) protein may provide improved protection from RSV disease. It is known that the G protein is an IFN antagonist, and IFN has been shown to be protective against RSV disease. In this study, we compared IFN responses in mouse lung epithelial (MLE-15) cells and in mice infected with RSV Line19 F treated with anti-G protein or anti-F protein mAbs. The levels of type I and III IFNs were determined. Anti-G protein mAbs improved the levels of IFNs compared with isotype-treated controls. These findings support the concept that anti-G protein mAbs mediate improved IFN responses against RSV disease, which may enable improved treatment of RSV infections.

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.

Breakthrough therapy designation of nirsevimab for the prevention of lower respiratory tract illness caused by respiratory syncytial virus infections (RSV)

INTRODUCTION

Respiratory syncytial virus (RSV) is a leading cause of serious lower respiratory tract infection (LRTI) in infants and young children. Palivizumab is an RSV-specific prophylactic for use in high-risk infants but treatment requires monthly injections and only modestly reduces hospitalization. Thus, new immunoprophylactic candidates are under development. Nirsevimab (MEDI8897) is a monoclonal antibody with an extended half-life developed to protect infants for an entire RSV season with a single dose.

AREAS COVERED

This review summarizes clinical trial data on nirsevimab. The authors introduce RSV and surface viral proteins involved in infection, then discuss the development and achievements of nirsevimab in clinical trials concluding with expert opinion. Information was compiled from PubMed, clinicaltrials.gov, and press releases from AstraZeneca and Sanofi.

EXPERT OPINION

Nirsevimab (MEDI8897) is an RSV F protein monoclonal antibody and the next-generation RSV medicine having an extended half-life developed for the prevention of LRTI caused by RSV. Nirsevimab will supplant the current standard of care for RSV prevention. Importantly, nirsevimab requires a single dose to last the entire RSV season and may be given to term, preterm, and high-risk infants. However, even with nirsevimab approval there remains a need for an efficacious RSV vaccine and treatments.

Seaweed Sulfated Polysaccharides against Respiratory Viral Infections

Respiratory viral infections have been a leading cause of morbidity and mortality worldwide. Despite massive advancements in the virology field, no specific treatment exists for most respiratory viral infections. Approved therapies against respiratory viruses rely almost exclusively on synthetic drugs that have potential side effects, restricting their use. This review aims to present natural marine sulfated polysaccharides possessing promising antiviral activity against respiratory viruses that could be a safe alternative to synthetic broad-spectrum antiviral drugs. The antiviral properties of marine sulfated polysaccharides are presented according to their mechanism of action on different types and strains of respiratory viruses, and the potential limits of their use are discussed.

Intervention Strategies for Seasonal and Emerging Respiratory Viruses with Drugs and Vaccines Targeting Viral Surface Glycoproteins

Vaccines and therapeutics targeting viral surface glycoproteins are a major component of disease prevention for respiratory viral diseases. Over the years, vaccines have proven to be the most successful intervention for preventing disease. Technological advances in vaccine platforms that focus on viral surface glycoproteins have provided solutions for current and emerging pathogens like SARS-CoV-2, and our understanding of the structural basis for antibody neutralization is guiding the selection of other vaccine targets for respiratory viruses like RSV. This review discusses the role of viral surface glycoproteins in disease intervention approaches.

Respiratory Syncytial Virus (RSV) G Protein Vaccines With Central Conserved Domain Mutations Induce CX3C-CX3CR1 Blocking Antibodies

Respiratory syncytial virus (RSV) infection can cause bronchiolitis, pneumonia, morbidity, and some mortality, primarily in infants and the elderly, for which no vaccine is available. The RSV attachment (G) protein contains a central conserved domain (CCD) with a CX3C motif implicated in the induction of protective antibodies, thus vaccine candidates containing the G protein are of interest. This study determined if mutations in the G protein CCD would mediate immunogenicity while inducing G protein CX3C-CX3CR1 blocking antibodies. BALB/c mice were vaccinated with structurally-guided, rationally designed G proteins with CCD mutations. The results show that these G protein immunogens induce a substantial anti-G protein antibody response, and using serum IgG from the vaccinated mice, these antibodies are capable of blocking the RSV G protein CX3C-CX3CR1 binding while not interfering with CX3CL1, fractalkine.

A multifunctional nanoparticle as a prophylactic and therapeutic approach targeting respiratory syncytial virus

Respiratory Syncytial Virus (RSV) has been a major health concern globally for decades, yet no effective prophylactic or treatment regimen is available. The key viral proteins responsible for RSV pathology include the fusion protein (F), the immunomodulatory non-structural-protein 1 (NS1) and the phosphoprotein (P) involved in viral replication. Herein, we developed a novel shell-core multifunctional nanosystem with dual payload: a plasmid construct encoding for shRNAs against NS1 and P, and an anti-fusion peptide (HR2D). Anti-ICAM1 antibody conjugated on the nanoparticle (NP) surface is used to target RSV infected cells. Our data show the potential of this nanosystem as a prophylactic and/or a therapeutic regimen against RSV infection. Furthermore, therapy of RSV infected mice with this nanosystem, in addition to reducing viral load, modulated expression of Th2 and allergy-associated cytokines such as IL4, IL-13 and IL-17 indicating a direct role of this nanosystem in the mechanisms involved in the immunoregulation of disease pathogenesis.

Challenges in the prevention or treatment of RSV with emerging new agents in children from low- and middle-income countries

INTRODUCTION

Respiratory syncytial virus (RSV) causes approximately 120,000 deaths annually in children <5 years, with 99% of fatalities occurring in low- and middle-income countries (LMICs).

AREAS COVERED

There are numerous RSV interventions in development, including long-acting monoclonal antibodies, vaccines (maternal and child) and treatments which are expected to become available soon. We reviewed the key challenges and issues that need to be addressed to maximize the impact of these interventions in LMICs. The epidemiology of RSV in LMICs was reviewed (PubMed search to 30 June 2020 inclusive) and the need for more and better-quality data, encompassing hospital admissions, community contacts, and longer-term respiratory morbidity, emphasized. The requirement for an agreed clinical definition of RSV lower respiratory tract infection was proposed. The pros and cons of the new RSV interventions are reviewed from the perspective of LMICs.

EXPERT OPINION

We believe that a vaccine (or combination of vaccines, if practicable) is the only viable solution to the burden of RSV in LMICs. A coordinated program, analogous to that with polio, involving governments, non-governmental organizations, the World Health Organization, the manufacturers and the healthcare community is required to realize the full potential of vaccine(s) and end the devastation of RSV in LMICs.

Single-Stranded Oligonucleotide-Mediated Inhibition of Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in young children. Currently, there is no RSV vaccine or universally accessible antiviral treatment available. Addressing the urgent need for new antiviral agents, we have investigated the capacity of a non-coding single-stranded oligonucleotide (ssON) to inhibit RSV infection. By utilizing a GFP-expressing RSV, we demonstrate that the ssON significantly reduced the proportion of RSV infected A549 cells (lung epithelial cells). Furthermore, we show that ssON's antiviral activity was length dependent and that both RNA and DNA of this class of oligonucleotides have antiviral activity. We reveal that ssON inhibited RSV infection by competing with the virus for binding to the cellular receptor nucleolin in vitro. Additionally, using a recombinant RSV that expresses luciferase we show that ssON effectively blocked RSV infection in mice. Treatment with ssON in vivo resulted in the upregulation of RSV-induced interferon stimulated genes (ISGs) such as Stat1, Stat2, Cxcl10, and Ccl2. This study highlights the possibility of using oligonucleotides as therapeutic agents against RSV infection. We demonstrate that the mechanism of action of ssON is the inhibition of viral entry in vitro, likely through the binding of the receptor, nucleolin and that ssON treatment against RSV infection in vivo additionally results in the upregulation of ISGs.

Innate and adaptive immune responses in respiratory virus infection: implications for the clinic

INTRODUCTION

The innate immune response is the first line of defense and consists of physical, chemical and cellular defenses. The adaptive immune response is the second line of defense and is pathogen-specific. Innate immunity occurs immediately while adaptive immunity develops upon pathogen exposure, and is long-lasting, highly specific, and sustained by memory T cells. Respiratory virus infection typically induces effective immunity but over-exuberant responses are associated with pathophysiology. Cytokines expressed in response to viral infection can enhance biological responses, activate, and trigger signaling pathways leading to adaptive immunity Vaccines induce immunity, specifically B and T cell responses. Vaccination is generally efficacious, but for many viruses, our understanding of vaccination strategies and immunity is incomplete or in its infancy. Studies that examine innate and adaptive immune responses to respiratory virus infection will aid vaccine development and may reduce the burden of respiratory viral disease.

AREAS COVERED

A literature search was performed using PubMed. The search covered: innate, adaptive, respiratory virus, vaccine development, B cell, and T cell.

EXPERT OPINION

Immunity rests on two pillars, i.e. the innate and adaptive immune system, which function together on different tasks to maintain homeostasis. a better understanding of immunity is necessary for disease prevention and intervention.