RSV N-nanorings fused to palivizumab-targeted neutralizing epitope as a nanoparticle RSV vaccine

Protein-Based Nanocarriers and Nanotherapeutics for Infection and Inflammation

Infectious and inflammatory diseases are one of the leading causes of death globally. The status quo has become more prominent with the onset of the coronavirus disease 2019 (COVID-19) pandemic. To combat these potential crises, proteins have been proven as highly efficacious drugs, drug targets, and biomarkers. On the other hand, advancements in nanotechnology have aided efficient and sustained drug delivery due to their nano-dimension-acquired advantages. Combining both strategies together, the protein nanoplatforms are equipped with the advantageous intrinsic properties of proteins as well as nanoformulations, eloquently changing the field of nanomedicine. Proteins can act as carriers, therapeutics, diagnostics, and theranostics in their nanoform as fusion proteins or as composites with other organic/inorganic materials. Protein-based nanoplatforms have been extensively explored to target the major infectious and inflammatory diseases of clinical concern. The current review comprehensively deliberated proteins as nanocarriers for drugs and nanotherapeutics for inflammatory and infectious agents, with special emphasis on cancer and viral diseases. A plethora of proteins from diverse organisms have aided in the synthesis of protein-based nanoformulations. The current study specifically presented the proteins of human and pathogenic origin to dwell upon the field of protein nanotechnology, emphasizing their pharmacological advantages. Further, the successful clinical translation and current bottlenecks of the protein-based nanoformulations associated with the infection-inflammation paradigm have also been discussed comprehensively. SIGNIFICANCE STATEMENT: This review discusses the plethora of promising protein-based nanocarriers and nanotherapeutics explored for infectious and inflammatory ailments, with particular emphasis on protein nanoparticles of human and pathogenic origin with reference to the advantages, ADME (absorption, distribution, metabolism, and excretion parameters), and current bottlenecks in development of protein-based nanotherapeutic interventions.

Use of Nanomaterials for Diagnosis and Treatment: The Advancement of Next-Generation Antiviral Therapy

Globally, viral illness propagation is the leading cause of morbidity and death, causing wreaking havoc on socioeconomic development and health care systems. The rise of infected individuals has outpaced the existing critical care facilities. Early and sophisticated methods are desperately required in this respect to halt the spread of the infection. Therefore, early detection of infectious agents and an early treatment approach may help minimize viral outbreaks. Conventional point-of-care diagnostic techniques such as computed tomography scan, quantitative real time polymerase chain reaction (qRT-PCR), X-ray, and immunoassay are still deemed valuable. However, the labor demanding, low sensitivity, and complex infrastructure needed for these methods preclude their use in distant areas. Nanotechnology has emerged as a potentially transformative technology due to its promise as an effective theranostic platform for diagnosing and treating viral infection, circumventing the limits of traditional techniques. Their unique physical and chemical characteristics make nanoparticles (NPs) advantageous for drug delivery platforms due to their size, encapsulation efficiency, improved bioavailability, effectiveness, immunogenicity, and antiviral response. This study discusses the recent research on nanotechnology-based treatments designed to combat new viruses.

Self-Assembly of Flagellin into Immunostimulatory Ring-like Nanostructures as an Antigen Delivery System

Proteinaceous nanoparticles represent attractive antigen carriers for vaccination as their size and repetitive antigen displays that mimic most viral particles enable efficient immune processing. However, these nanocarriers are often unable to stimulate efficiently the innate immune system, requiring coadministration with adjuvants to promote long-lasting protective immunity. The protein flagellin, which constitutes the primary constituent of the bacterial flagellum, has been widely evaluated as an antigen carrier due to its intrinsic adjuvant properties involving activation of the innate immune receptor Toll-like receptor 5 (TLR5). Although flagellin is known for its ability to self-assemble into micron-scale length nanotubes, few studies have evaluated the potential usage of flagellin-based nanostructures as immunostimulatory antigen carriers. In this study, we reported for the first time a strategy to guide the self-assembly of a flagellin protein from Bacillus subtilis, Hag, into lower aspect ratio nanoparticles by hindering non-covalent interactions responsible for its elongation into nanotubes. We observed that addition of an antigenic sequence derived from the influenza A virus (3M2e) at the C-terminus of this flagellin, as opposed to positioning the epitope into mid-sequence, precluded filament elongation and resulted in low aspect ratio ring-like nanostructures upon salting-out-induced self-assembly. These nanostructures displayed the antigen at their surface and shared morphological and structural characteristics with flagellin nanotubes, with a diameter of approximately 12 nm, and an α-helix-rich secondary structure. Flagellin ring-like nanostructures were efficiently internalized by antigen-presenting cells, and avidly activated the TLR5 in vitro as well as the innate and adaptive immune responses. Intranasal immunization of mice with these nanostructures resulted in the potentiation of the antigen-specific antibody response and protection against a lethal infection with the influenza A virus, illustrating the potential of these intrinsically immunostimulatory nanostructures as antigen carriers.

Nanotechnology-based bio-tools and techniques for COVID-19 management

COVID-19, a most serious issue and the threat for the human life, has affected millions of people worldwide. It was observed as unknown cases of pneumonia in Wuhan, China and claimed unknown till January 10, 2020 and led to the corona virus disease 2019 (COVID-19) therefore worldwide pandemic. The Director-General-WHO declared the outbreak of COVID-19 and constituted a Public Health Emergency of International Concern (PHEIC) on January 30, 2020 with the recommendations of the Emergency Committee. This outbreak originated from Wuhan, China in 2019 named as COVID-19 approached 115 countries, with 119,239 cases of infection spread and 4287 deaths by March 11, 2020.

Potential Neurocognitive Symptoms Due to Respiratory Syncytial Virus Infection

Respiratory infections are among the major public health burdens, especially during winter. Along these lines, the human respiratory syncytial virus (hRSV) is the principal viral agent causing acute lower respiratory tract infections leading to hospitalization. The pulmonary manifestations due to hRSV infection are bronchiolitis and pneumonia, where the population most affected are infants and the elderly. However, recent evidence suggests that hRSV infection can impact the mother and fetus during pregnancy. Studies have indicated that hRSV can infect different cell types from the placenta and even cross the placenta barrier and infect the fetus. In addition, it is known that infections during the gestational period can lead to severe consequences for the development of the fetus due not only to a direct viral infection but also because of maternal immune activation (MIA). Furthermore, it has been described that the development of the central nervous system (CNS) of the fetus can be affected by the inflammatory environment of the uterus caused by viral infections. Increasing evidence supports the notion that hRSV could invade the CNS and infect nervous cells, such as microglia, neurons, and astrocytes, promoting neuroinflammation. Moreover, it has been described that the hRSV infection can provoke neurological manifestations, including cognitive impairment and behavioral alterations. Here, we will review the potential effect of hRSV in brain development and the potential long-term neurological sequelae.

Contribution of Nanotechnologies to Vaccine Development and Drug Delivery against Respiratory Viruses

According to the Center for Disease Control and Prevention (CDC), the coronavirus disease 2019, a respiratory viral illness linked to significant morbidity, mortality, production loss, and severe economic depression, was the third-largest cause of death in 2020. Respiratory viruses such as influenza, respiratory syncytial virus, SARS-CoV-2, and adenovirus, are among the most common causes of respiratory illness in humans, spreading as pandemics or epidemics throughout all continents. Nanotechnologies are particles in the nanometer range made from various compositions. They can be lipid-based, polymer-based, protein-based, or inorganic in nature, but they are all bioinspired and virus-like. In this review, we aimed to present a short review of the different nanoparticles currently studied, in particular those which led to publications in the field of respiratory viruses. We evaluated those which could be beneficial for respiratory disease-based viruses; those which already have contributed, such as lipid nanoparticles in the context of COVID-19; and those which will contribute in the future either as vaccines or antiviral drug delivery systems. We present a short assessment based on a critical selection of evidence indicating nanotechnology's promise in the prevention and treatment of respiratory infections.

Recent Progress in Nanotechnology for COVID-19 Prevention, Diagnostics and Treatment

The COVID-19 pandemic is currently an unprecedented public health threat. The rapid spread of infections has led to calls for alternative approaches to combat the virus. Nanotechnology is taking root against SARS-CoV-2 through prevention, diagnostics and treatment of infections. In light of the escalating demand for managing the pandemic, a comprehensive review that highlights the role of nanomaterials in the response to the pandemic is highly desirable. This review article comprehensively discusses the use of nanotechnology for COVID-19 based on three main categories: prevention, diagnostics and treatment. We first highlight the use of various nanomaterials including metal nanoparticles, carbon-based nanoparticles and magnetic nanoparticles for COVID-19. We critically review the benefits of nanomaterials along with their applications in personal protective equipment, vaccine development, diagnostic device fabrication and therapeutic approaches. The remaining key challenges and future directions of nanomaterials for COVID-19 are briefly discussed. This review is very informative and helpful in providing guidance for developing nanomaterial-based products to fight against COVID-19.

Emerging Advances of Nanotechnology in Drug and Vaccine Delivery against Viral Associated Respiratory Infectious Diseases (VARID)

Viral-associated respiratory infectious diseases are one of the most prominent subsets of respiratory failures, known as viral respiratory infections (VRI). VRIs are proceeded by an infection caused by viruses infecting the respiratory system. For the past 100 years, viral associated respiratory epidemics have been the most common cause of infectious disease worldwide. Due to several drawbacks of the current anti-viral treatments, such as drug resistance generation and non-targeting of viral proteins, the development of novel nanotherapeutic or nano-vaccine strategies can be considered essential. Due to their specific physical and biological properties, nanoparticles hold promising opportunities for both anti-viral treatments and vaccines against viral infections. Besides the specific physiological properties of the respiratory system, there is a significant demand for utilizing nano-designs in the production of vaccines or antiviral agents for airway-localized administration. SARS-CoV-2, as an immediate example of respiratory viruses, is an enveloped, positive-sense, single-stranded RNA virus belonging to the coronaviridae family. COVID-19 can lead to acute respiratory distress syndrome, similarly to other members of the coronaviridae. Hence, reviewing the current and past emerging nanotechnology-based medications on similar respiratory viral diseases can identify pathways towards generating novel SARS-CoV-2 nanotherapeutics and/or nano-vaccines.

Epicutaneous immunization using synthetic virus-like particles efficiently boosts protective immunity to respiratory syncytial virus

Despite the substantial health and economic burden caused by RSV-associated illness, no vaccine is available. The sole licensed treatment (palivizumab), composed of a monoclonal neutralizing antibody, blocks the fusion of the virus to the host cell but does not prevent infection. The development of a safe and efficacious RSV vaccine is therefore a priority, but also a considerable challenge, and new innovative strategies are warranted. Most of the adult population encounter regular RSV infections and can elicit a robust neutralizing antibody response, but unfortunately it wanes over time and reinfections during subsequent seasons are common. One approach to protect the mother and young infant from RSV infection is to administer a vaccine capable of boosting preexisting RSV immunity during pregnancy, which would provide protection to the fetus through passive transfer of maternal antibodies, thus preventing primary RSV infection in newborns during their first months of life. Here, we describe the preclinical evaluation of an epicutaneous RSV vaccine booster that combines epicutaneous patches as a delivery platform and a Synthetic Virus-Like Particles (SVLP)-based vaccine displaying multiple RSV F-protein site II (FsII, palivizumab epitope) mimetic as antigen (V-306). We demonstrated in mice that epicutaneous immunization with V-306 efficiently boosts preexisting immunity induced by the homologous V-306 administered subcutaneously. This boosting was characterized by a significant increase in F- and FsII-specific antibodies capable of competing with palivizumab for its target antigen and neutralize RSV. More importantly, epicutaneous booster immunization with V-306 significantly decreased lung viral replication in experimental mice after intranasal RSV challenge, without inducing enhanced RSV disease. In conclusion, an epicutaneous booster vaccine based on V-306 is safe and efficacious in enhancing RSV preexisting immunity in mice. This needle-free vaccine candidate would be potentially suited as a booster vaccine for vulnerable populations such as young infants via pregnant women, and the elderly.

Nanotechnology-based antiviral therapeutics

The host immune system is highly compromised in case of viral infections and relapses are very common. The capacity of the virus to destroy the host cell by liberating its own DNA or RNA and replicating inside the host cell poses challenges in the development of antiviral therapeutics. In recent years, many new technologies have been explored for diagnosis, prevention, and treatment of viral infections. Nanotechnology has emerged as one of the most promising technologies on account of its ability to deal with viral diseases in an effective manner, addressing the limitations of traditional antiviral medicines. It has not only helped us to overcome problems related to solubility and toxicity of drugs, but also imparted unique properties to drugs, which in turn has increased their potency and selectivity toward viral cells against the host cells. The initial part of the paper focuses on some important proteins of influenza, Ebola, HIV, herpes, Zika, dengue, and corona virus and those of the host cells important for their entry and replication into the host cells. This is followed by different types of nanomaterials which have served as delivery vehicles for the antiviral drugs. It includes various lipid-based, polymer-based, lipid-polymer hybrid-based, carbon-based, inorganic metal-based, surface-modified, and stimuli-sensitive nanomaterials and their application in antiviral therapeutics. The authors also highlight newer promising treatment approaches like nanotraps, nanorobots, nanobubbles, nanofibers, nanodiamonds, nanovaccines, and mathematical modeling for the future. The paper has been updated with the recent developments in nanotechnology-based approaches in view of the ongoing pandemic of COVID-19.Graphical abstract.

Single-Shot Vaccines against Bovine Respiratory Syncytial Virus (BRSV): Comparative Evaluation of Long-Term Protection after Immunization in the Presence of BRSV-Specific Maternal Antibodies

The induction of long-lasting clinical and virological protection is needed for a successful vaccination program against the bovine respiratory syncytial virus (BRSV). In this study, calves with BRSV-specific maternally derived antibodies were vaccinated once, either with (i) a BRSV pre-fusion protein (PreF) and Montanide^TM ISA61 VG (ISA61, n = 6), (ii) BRSV lacking the SH gene (ΔSHrBRSV, n = 6), (iii) a commercial vaccine (CV, n = 6), or were injected with ISA61 alone (n = 6). All calves were challenged with BRSV 92 days later and were euthanized 13 days post-infection. Based on clinical, pathological, and proteomic data, all vaccines appeared safe. Compared to the controls, PreF induced the most significant clinical and virological protection post-challenge, followed by ΔSHrBRSV and CV, whereas the protection of PreF-vaccinated calves was correlated with BRSV-specific serum immunoglobulin (Ig)G antibody responses 84 days post-vaccination, and the IgG antibody titers of ΔSHrBRSV- and CV-vaccinated calves did not differ from the controls on this day. Nevertheless, strong anamnestic BRSV- and PreF-specific IgG responses occurred in calves vaccinated with either of the vaccines, following a BRSV challenge. In conclusion, PreF and ΔSHrBRSV are two efficient one-shot candidate vaccines. By inducing a protection for at least three months, they could potentially improve the control of BRSV in calves.

Nanotechnology against the novel coronavirus (severe acute respiratory syndrome coronavirus 2): diagnosis, treatment, therapy and future perspectives

COVID-19, as an emerging infectious disease, has caused significant mortality and morbidity along with socioeconomic impact. No effective treatment or vaccine has been approved yet for this pandemic disease. Cutting-edge tools, especially nanotechnology, should be strongly considered to tackle this virus. This review aims to propose several strategies to design and fabricate effective diagnostic and therapeutic agents against COVID-19 by the aid of nanotechnology. Polymeric, inorganic self-assembling materials and peptide-based nanoparticles are promising tools for battling COVID-19 as well as its rapid diagnosis. This review summarizes all of the exciting advances nanomaterials are making toward COVID-19 prevention, diagnosis and therapy.

Smart and Sustainable Nanotechnological Solutions in a Battle against COVID-19 and Beyond: A Critical Review

The variety of available biocidal features make nanomaterials promising for fighting infections. To effectively battle COVID-19, categorized as a pandemic by the World Health Organization (WHO), materials scientists and biotechnologists need to combine their knowledge to develop efficient antiviral nanomaterials. By design, nanostructured materials (spherical, two-dimensional, hybrid) can express a diverse bioactivity and unique combination of specific, nonspecific, and mixed mechanisms of antiviral action. It can be related to the material's specific features and their multiple functionalization strategies. This is a complex guiding approach in which an interaction target is constantly moving and quickly changing. On the other hand, in such a rush, sustainability may be put aside. Therefore, to elucidate the most promising nanotechnological solutions, we critically review available data within the frame of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other types of viruses. We highlight solutions that are, or could be, more sustainable and less toxic. In this regard, reduction of the number of synthetic routes, organic solvents, byproducts, and residues is highly recommended. Such efficient, green solutions may be further used for the prevention of virion-host interactions, treatment of the already developed infection, reducing inflammation, and finally, protecting healthcare professionals with masks, fabrics, equipment, and in other associated areas. Further translation into the market needs putting on the fast track with respect to principles of green chemistry, feasibility, safety, and the environment.

Taking Advantage of the Morpheein Behavior of Peroxiredoxin in Bionanotechnology

Morpheeins are proteins that reversibly assemble into different oligomers, whose architectures are governed by conformational changes of the subunits. This property could be utilized in bionanotechnology where the building of nanometric and new high-ordered structures is required. By capitalizing on the adaptability of morpheeins to create patterned structures and exploiting their inborn affinity toward inorganic and living matter, “bottom-up” creation of nanostructures could be achieved using a single protein building block, which may be useful as such or as scaffolds for more complex materials. Peroxiredoxins represent the paradigm of a morpheein that can be applied to bionanotechnology. This review describes the structural and functional transitions that peroxiredoxins undergo to form high-order oligomers, e.g., rings, tubes, particles, and catenanes, and reports on the chemical and genetic engineering approaches to employ them in the generation of responsive nanostructures and nanodevices. The usefulness of the morpheeins’ behavior is emphasized, supporting their use in future applications.

Applications of Nanovaccines for Disease Prevention in Cattle

Vaccines are one of the most important tools available to prevent and reduce the incidence of infectious diseases in cattle. Despite their availability and widespread use to combat many important pathogens impacting cattle, several of these products demonstrate variable efficacy and safety in the field, require multiple doses, or are unstable under field conditions. Recently, nanoparticle-based vaccine platforms (nanovaccines) have emerged as promising alternatives to more traditional vaccine platforms. In particular, polymer-based nanovaccines provide sustained release of antigen payloads, stabilize such payloads, and induce enhanced antibod- and cell-mediated immune responses, both systemically and locally. To improve vaccine administrative strategies and efficacy, they can be formulated to contain multiple antigenic payloads and have the ability to protect fragile proteins from degradation. Nanovaccines are also stable at room temperature, minimizing the need for cold chain storage. Nanoparticle platforms can be synthesized for targeted delivery through intranasal, aerosol, or oral administration to induce desired mucosal immunity. In recent years, several nanovaccine platforms have emerged, based on biodegradable and biocompatible polymers, liposomes, and virus-like particles. While most nanovaccine candidates have not yet advanced beyond testing in rodent models, a growing number have shown promise for use against cattle infectious diseases. This review will highlight recent advancements in polymeric nanovaccine development and the mechanisms by which nanovaccines may interact with the bovine immune system. We will also discuss the positive implications of nanovaccines use for combating several important viral and bacterial disease syndromes and consider important future directions for nanovaccine development in beef and dairy cattle.

Nanomedicine strategies to target coronavirus

With the severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002, the middle east respiratory syndrome CoV (MERS-CoV) in 2012 and the recently discovered SARS-CoV-2 in December 2019, the 21st first century has so far faced the outbreak of three major coronaviruses (CoVs). In particular, SARS-CoV-2 spread rapidly over the globe affecting nearly 25.000.000 people up to date. Recent evidences pointing towards mutations within the viral spike proteins of SARS-CoV-2 that are considered the cause for this rapid spread and currently around 300 clinical trials are running to find a treatment for SARS-CoV-2 infections. Nanomedicine, the application of nanocarriers to deliver drugs specifically to a target sites, has been applied for different diseases, such as cancer but also in viral infections. Nanocarriers can be designed to encapsulate vaccines and deliver them towards antigen presenting cells or function as antigen-presenting carriers themselves. Furthermore, drugs can be encapsulated into such carriers to directly target them to infected cells. In particular, virus-mimicking nanoparticles (NPs) such as self-assembled viral proteins, virus-like particles or liposomes, are able to replicate the infection mechanism and can not only be used as delivery system but also to study viral infections and related mechanisms. This review will provide a detailed description of the composition and replication strategy of CoVs, an overview of the therapeutics currently evaluated in clinical trials against SARS-CoV-2 and will discuss the potential of NP-based vaccines, targeted delivery of therapeutics using nanocarriers as well as using NPs to further investigate underlying biological processes in greater detail.

A Single Shot Pre-fusion-Stabilized Bovine RSV F Vaccine is Safe and Effective in Newborn Calves with Maternally Derived Antibodies

Achieving safe and protective vaccination against respiratory syncytial virus (RSV) in infants and in calves has proven a challenging task. The design of recombinant antigens with a conformation close to their native form in virus particles is a major breakthrough. We compared two subunit vaccines, the bovine RSV (BRSV) pre-fusion F (preF) alone or with nanorings formed by the RSV nucleoprotein (preF+N). PreF and N proteins are potent antigenic targets for neutralizing antibodies and T cell responses, respectively. To tackle the challenges of neonatal immunization, three groups of six one-month-old calves with maternally derived serum antibodies (MDA) to BRSV received a single intramuscular injection of PreF, preF+N with Montanide^TM ISA61 VG (ISA61) as adjuvant or only ISA61 (control). One month later, all calves were challenged with BRSV and monitored for virus replication in the upper respiratory tract and for clinical signs of disease over one week, and then post-mortem examinations of their lungs were performed. Both preF and preF+N vaccines afforded safe, clinical, and virological protection against BRSV, with little difference between the two subunit vaccines. Analysis of immune parameters pointed to neutralizing antibodies and antibodies to preF as being significant correlates of protection. Thus, a single shot vaccination with preF appears sufficient to reduce the burden of BRSV disease in calves with MDA.

On Facing the SARS-CoV-2 (COVID-19) with Combination of Nanomaterials and Medicine: Possible Strategies and First Challenges

Global health is facing the most dangerous situation regarding the novel severe acute respiratory syndrome called coronavirus 2 (SARS-CoV-2), which is widely known as the abbreviated COVID-19 pandemic. This is due to the highly infectious nature of the disease and its possibility to cause pneumonia induced death in approximately 6.89% of infected individuals (data until 27 April 2020). The pathogen causing COVID-19 is called severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which is believed to be originated from the Wuhan Province in China. Unfortunately, an effective and approved vaccine for SARS-CoV-2 virus is still not available, making the situation more dangerous and currently available medical care futile. This unmet medical need thus requires significant and very urgent research attention to develop an effective vaccine to address the SARS-CoV-2 virus. In this review, the state-of-the-art drug design strategies against the virus are critically summarized including exploitations of novel drugs and potentials of repurposed drugs. The applications of nanochemistry and general nanotechnology was also discussed to give the status of nanodiagnostic systems for COVID-19.

Structure-Based Vaccine Antigen Design

Enabled by new approaches for rapid identification and selection of human monoclonal antibodies, atomic-level structural information for viral surface proteins, and capacity for precision engineering of protein immunogens and self-assembling nanoparticles, a new era of antigen design and display options has evolved. While HIV-1 vaccine development has been a driving force behind these technologies and concepts, clinical proof-of-concept for structure-based vaccine design may first be achieved for respiratory syncytial virus (RSV), where conformation-dependent access to neutralization-sensitive epitopes on the fusion glycoprotein determines the capacity to induce potent neutralizing activity. Success with RSV has motivated structure-based stabilization of other class I viral fusion proteins for use as immunogens and demonstrated the importance of structural information for developing vaccines against other viral pathogens, particularly difficult targets that have resisted prior vaccine development efforts. Solving viral surface protein structures also supports rapid vaccine antigen design and application of platform manufacturing approaches for emerging pathogens.

A conformational switch balances viral RNA accessibility and protection in a nucleocapsid ring model

Virus from the Mononegavirales order share common features ranging from virion structure arrangement to mechanisms of replication and transcription. One of them is the way the nucleoprotein (N) wraps and protects the RNA genome from degradation by forming a highly ordered helical nucleocapsid. However, crystal structures from numerous Mononegavirales reveal that binding to the nucleoprotein results in occluded nucleotides that hinder base pairing necessary for transcription and replication. This hints at the existence of alternative conformations of the N protein that would impact on the protein-RNA interface, allowing for transient exposure of the nucleotides without complete RNA release. Moreover, the regulation between the alternative conformations should be finely tuned. Recombinant expression of N from the respiratory syncytial virus form regular N/RNA common among all Mononegavirales, and these constitute an ideal minimal unit for investigating the mechanisms through which these structures protect RNA so efficiently while allowing for partial accessibility during transcription and replication. Neither pH nor high ionic strength could dissociate the RNA but led to irreversible aggregation of the nucleoprotein. Low concentrations of guanidine chloride dissociated the RNA moiety but leading to irreversible aggregation of the protein moiety. On the other hand, high concentrations of urea and long incubation periods were required to remove bound RNA. Both denaturants eventually led to unfolding but converged in the formation of an RNA-free β-enriched intermediate species that remained decameric even at high denaturant concentrations. Although the N-RNA rings interact with the phosphoprotein P, the scaffold of the RNA polymerase complex, this interaction did not lead to RNA dissociation from the rings in vitro. Thus, we have uncovered complex equilibria involving changes in secondary structure of N and RNA loosening, processes that must take place in the context of RNA transcription and replication, whose detailed mechanisms and cellular and viral participants need to be established.

Boosting subdominant neutralizing antibody responses with a computationally designed epitope-focused immunogen

Throughout the last several decades, vaccination has been key to prevent and eradicate infectious diseases. However, many pathogens (e.g., respiratory syncytial virus [RSV], influenza, dengue, and others) have resisted vaccine development efforts, largely because of the failure to induce potent antibody responses targeting conserved epitopes. Deep profiling of human B cells often reveals potent neutralizing antibodies that emerge from natural infection, but these specificities are generally subdominant (i.e., are present in low titers). A major challenge for next-generation vaccines is to overcome established immunodominance hierarchies and focus antibody responses on crucial neutralization epitopes. Here, we show that a computationally designed epitope-focused immunogen presenting a single RSV neutralization epitope elicits superior epitope-specific responses compared to the viral fusion protein. In addition, the epitope-focused immunogen efficiently boosts antibodies targeting the palivizumab epitope, resulting in enhanced neutralization. Overall, we show that epitope-focused immunogens can boost subdominant neutralizing antibody responses in vivo and reshape established antibody hierarchies.

A computationally designed epitope-focused immunogen presenting a single neutralization epitope from Respiratory Syncytial Virus elicits superior epitope-specific responses compared to the viral fusion protein. Furthermore, epitope-focused immunogens can reshape established antibody hierarchies.

Vaccines are one of the most valuable instruments to prevent and control infectious diseases. Their primary correlate of protection is the level of induction of neutralizing antibodies that target critical antigenic sites and thereby block infection. Natural infections with pathogens such as the respiratory syncytial virus (RSV) or influenza induce a broad repertoire of antibodies that target multiple epitopes. Among those, functional antibodies with key specificities are often subdominant (present in low titers). Thus, a central goal for vaccine development is to focus antibody responses on such neutralization epitopes. Here, we show that a computationally designed, epitope-focused immunogen mimicking an important RSV neutralization epitope (site II) can focus antibodies onto this well-defined epitope. In a scenario of preexisting immunity, in which site II–specific antibodies were subdominant, the epitope-focused immunogen selectively boosted site II–specific antibodies, resulting in an increased viral neutralization through this epitope. We propose that rationally designed immunogens spotlighting defined epitopes have a unique potential to focus antibody responses on functionally conserved sites in cases of preexisting immunity. Our results have broad implications for vaccine design as a strategy to steer preexisting antibody responses away from immunodominant, variable epitopes and toward subdominant epitopes that confer broad and potent neutralization.

Nanoparticle-Based Vaccines Against Respiratory Viruses

The respiratory mucosa is the primary portal of entry for numerous viruses such as the respiratory syncytial virus, the influenza virus and the parainfluenza virus. These pathogens initially infect the upper respiratory tract and then reach the lower respiratory tract, leading to diseases. Vaccination is an affordable way to control the pathogenicity of viruses and constitutes the strategy of choice to fight against infections, including those leading to pulmonary diseases. Conventional vaccines based on live-attenuated pathogens present a risk of reversion to pathogenic virulence while inactivated pathogen vaccines often lead to a weak immune response. Subunit vaccines were developed to overcome these issues. However, these vaccines may suffer from a limited immunogenicity and, in most cases, the protection induced is only partial. A new generation of vaccines based on nanoparticles has shown great potential to address most of the limitations of conventional and subunit vaccines. This is due to recent advances in chemical and biological engineering, which allow the design of nanoparticles with a precise control over the size, shape, functionality and surface properties, leading to enhanced antigen presentation and strong immunogenicity. This short review provides an overview of the advantages associated with the use of nanoparticles as vaccine delivery platforms to immunize against respiratory viruses and highlights relevant examples demonstrating their potential as safe, effective and affordable vaccines.

Utility of the Neonatal Calf Model for Testing Vaccines and Intervention Strategies for Use against Human RSV Infection

Respiratory syncytial virus (RSV) is a significant cause of pediatric respiratory tract infections. It is estimated that two-thirds of infants are infected with RSV during the first year of life and it is one of the leading causes of death in this age group worldwide. Similarly, bovine RSV is a primary viral pathogen in cases of pneumonia in young calves and plays a significant role in bovine respiratory disease complex. Importantly, naturally occurring infection of calves with bovine RSV shares many features in common with human RSV infection. Herein, we update our current understanding of RSV infection in cattle, with particular focus on similarities between the calf and human infection, and the recent reports in which the neonatal calf has been employed for the development and testing of vaccines and therapeutics which may be applied to hRSV infection in humans.

First demonstration of the circulation of a pneumovirus in French pigs by detection of anti-swine orthopneumovirus nucleoprotein antibodies

The presence of pneumoviruses in pigs is poorly documented. In this study, we used the published sequence of the nucleoprotein (N) of the recently identified Swine Orthopneumovirus (SOV) to express and purify SOV N as a recombinant protein in Escherichia coli. This protein was purified as nanorings and used to set up an enzyme-linked immunosorbent assay, which was used to analyse the presence of anti-pneumovirus N antibodies in swine sera. Sera collected from different pig farms in the West of France and from specific pathogen free piglets before colostrum uptake showed indirectly that a pneumovirus is circulating in pig populations with some variations between animals. Piglets before colostrum uptake were sero-negative for anti-pneumovirus antibodies while most of the other pigs showed positivity. Interestingly, in two farms presenting respiratory clinical signs and negative or under control for some common respiratory pathogens, pigs were detected positive for anti-pneumovirus antibodies. Globally, anti-pneumovirus N antibody concentrations were variable between and within farms. Further studies will aim to isolate the circulating virus and determine its potential pathogenicity. SOV could potentially become a new member of the porcine respiratory complex, important on its own or in association with other viral and bacterial micro-organisms.

Immunological Features of Respiratory Syncytial Virus-Caused Pneumonia-Implications for Vaccine Design

The human respiratory syncytial virus (hRSV) is the causative agent for high rates of hospitalizations due to viral bronchiolitis and pneumonia worldwide. Such a disease is characterized by an infection of epithelial cells of the distal airways that leads to inflammation and subsequently to respiratory failure. Upon infection, different pattern recognition receptors recognize the virus and trigger the innate immune response against the hRSV. Further, T cell immunity plays an important role for virus clearance. Based on animal studies, it is thought that the host immune response to hRSV is based on a biased T helper (Th)-2 and Th17 T cell responses with the recruitment of T cells, neutrophils and eosinophils to the lung, causing inflammation and tissue damage. In contrast, human immunity against RSV has been shown to be more complex with no definitive T cell polarization profile. Nowadays, only a humanized monoclonal antibody, known as palivizumab, is available to protect against hRSV infection in high-risk infants. However, such treatment involves several injections at a significantly high cost. For these reasons, intense research has been focused on finding novel vaccines or therapies to prevent hRSV infection in the population. Here, we comprehensively review the recent literature relative to the immunological features during hRSV infection, as well as the new insights into preventing the disease caused by this virus.

Nanotechnology: Advancing the translational respiratory research

Considering the various limitations associated with the conventional dosage forms, nanotechnology is gaining increased attention in drug delivery particularly in respiratory medicine and research because of its advantages like targeting effects, improved pharmacotherapy, and patient compliance. This paper provides a quick snapshot about the recent trends and applications of nanotechnology to various translational and formulation scientists working on various respiratory diseases, which can help paving a new path in developing effective drug delivery system.