Synthetic Biodegradable Microparticle and Nanoparticle Vaccines against the Respiratory Syncytial Virus

Cholesterol as an inbuilt immunoadjuvant for a lipopeptide vaccine against group A Streptococcus infection

Peptide-based vaccines can trigger highly specific immune responses, although peptides alone are usually unable to confer strong humoral or cellular immunity. Consequently, peptide antigens are administered with immunostimulatory adjuvants, but only a few are safe and effective for human use. To overcome this obstacle, herein a peptide antigen was lipidated to effectively anchor it to liposomes and emulsion. A peptide antigen B cell epitope from Group A Streptococcus M protein was conjugated to a universal T helper epitope, the pan DR-biding epitope (PADRE), alongside a lipidic moiety cholesterol. Compared to a free peptide antigen, the lipidated version (LP1) adopted a helical conformation and self-assembled into small nanoparticles. Surprisingly, LP1 alone induced the same or higher antibody titers than liposomes or emulsion-based formulations. In addition, antibodies produced by mice immunized with LP1 were more opsonic than those induced by administering the antigen with incomplete Freund's adjuvant. No side effects were observed in the immunized mice and no excessive inflammatory immune responses were detected. Overall, this study demonstrated how simple conjugation of cholesterol to a peptide antigen can produce a safe and efficacious vaccine against Group A Streptococcus - the leading cause of superficial infections and the bacteria responsible for deadly post-infection autoimmune disorders.

Intranasal Vaccination with a Respiratory-Syncytial-Virus-Based Virus-like Particle Displaying the G Protein Conserved Region Induces Severe Weight Loss and Pathology upon Challenge with Wildtype Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is a major cause of severe respiratory tract disease worldwide, and a pediatric vaccine is not available. We generated a filamentous RSV-based virus-like particle (VLP) that presents the central conserved region of the attachment protein G. This was achieved by co-expressing the matrix protein, phosphoprotein, nucleoprotein, and a hybrid fusion protein in which the F ectodomain was replaced with the G central region (GCR). The latter is relatively conserved and contains a receptor binding site and hence is a logical vaccine target. The immunogenicity and efficacy of the resulting VLP, termed VLP-GCR, were examined in mice using intranasal application without adjuvant. VLP-GCR induced substantial anti-N antibody levels but very low anti-G antibody levels, even after three vaccinations. In contrast, a VLP presenting prefusion-stabilized fusion (preF) protein instead of GCR induced both high anti-F and anti-nucleoprotein antibody levels, suggesting that our GCR antigen was poorly immunogenic. Challenge of VLP-GCR-vaccinated mice caused increased weight loss and lung pathology, and both VLPs induced mucus in the lungs. Thus, neither VLP is suitable as a vaccine for RSV-naive individuals. However, VLP-preF enhanced the proportion of preF antibodies and could serve as a multi-antigen mucosal booster vaccine in the RSV-experienced population.

The Application of Nanovaccines in Autoimmune Diseases

Autoimmune diseases are diseases caused by the body's chronic immune responses to self-antigens and attacks on the host's own cells, tissues and organs. The dysfunction of innate immunity and adaptive immunity leads to the destruction of autoimmune tolerance, which is the most basic factor leading to pathogenesis. The optimal strategy for autoimmune diseases is to modify the host immune system to restore tolerance. The ideal effect of therapeutic autoimmune diseases is to eliminate the autoantigen-specific spontaneous immune response without interfering with the immune response against other antigens. Therapeutic nanovaccines that produce immune tolerance conform to this principle. Nanomaterials provide a platform for antigen loading and modification due to their unique physical and chemical properties. Nanovaccines based on nanomaterial technology can simultaneously enable antigens and adjuvants to be absorbed by immune cells and induce rapid and durable immunity. Nanovaccines have the advantages of being able to be designed and loaded and of better protecting antigens from premature degradation. Nanovaccines also have the ability to target specific tissues or cells through optimized design. We review the latest research progress of nanovaccines for autoimmune diseases and the design strategies of nanovaccines to promote the development of more effective nanovaccines for autoimmune diseases.

A Therapeutic Nanovaccine that Generates Anti-Amyloid Antibodies and Amyloid-specific Regulatory T Cells for Alzheimer's Disease

Alzheimer's disease (AD), the most common cause of dementia, is a complex condition characterized by multiple pathophysiological mechanisms including amyloid-β (Aβ) plaque accumulation and neuroinflammation in the brain. The current immunotherapy approaches, such as anti-Aβ monoclonal antibody (mAb) therapy, Aβ vaccines, and adoptive regulatory T (Treg) cell transfer, target a single pathophysiological mechanism, which may lead to unsatisfactory therapeutic efficacy. Furthermore, Aβ vaccines often induce T helper 1 (Th1) cell-mediated inflammatory responses. Here, a nanovaccine composed of lipid nanoparticles loaded with Aβ peptides and rapamycin is developed, which targets multiple pathophysiological mechanisms, exhibits the combined effects of anti-Aβ antibody therapy and adoptive Aβ-specific Treg cell transfer, and can overcome the limitations of current immunotherapy approaches for AD. The Nanovaccine effectively delivers rapamycin and Aβ peptides to dendritic cells, produces both anti-Aβ antibodies and Aβ-specific Treg cells, removes Aβ plaques in the brain, alleviates neuroinflammation, prevents Th1 cell-mediated excessive immune responses, and inhibits cognitive impairment in mice. The nanovaccine shows higher efficacy in cognitive recovery than an Aβ vaccine. Unlike anti-Aβ mAb therapy and adoptive Treg cell transfer, both of which require complicated and costly manufacturing processes, the nanovaccine is easy-to-prepare and cost-effective. The nanovaccines can represent a novel treatment option for AD.

Alloferon and Zanamivir Show Effective Antiviral Activity against Influenza A Virus (H1N1) Infection In Vitro and In Vivo

The use of vaccines is the most effective and reliable method for the prevention of viral infections. However, research on evaluation of effective therapeutic agents for use in treatment after infection is necessary. Zanamivir was administered through inhalation for treatment of pandemic influenza A/H1N1 in 2009. However, the emergence of drug-resistant strains can occur rapidly. Alloferon, an immunomodulatory drug developed as an NK cell activator, exerts antiviral effects against various viruses, particularly influenza viruses. Therefore, alloferon and zanamivir were administered in combination in an effort to improve the antiviral effect of zanamivir by reducing H1N1 resistance. First, we confirmed that administration of combined treatment would result in effective inhibition of viral proliferation in MDCK and A549 cells infected with H1N1. Production of IL-6 and MIP-1α in these cells and the activity of p38 MAPK and c-Jun that are increased by H1N1 were inhibited by combined treatment. Mice were then infected intranasally with H1N1, and examination of the antiviral efficacy of the alloferon/zanamivir combination was performed. The results showed that combined treatment after infection with H1N1 prevented weight loss, increased the survival rate, and improved lung fibrosis. Combined treatment also resulted in reduced infiltration of neutrophils and macrophages into the lungs. Combined treatment effectively inhibited the activity of p38 MAPK and c-Jun in lung tissue, which was increased by infection with H1N1. Therefore, the combination of alloferon/zanamivir effectively prevents the development of H1N1-mediated inflammation in the lungs by inhibiting the production of inflammatory mediators and migration of inflammatory cells into lung tissue.

Dendritic cell activation by a micro particulate based system containing the influenza matrix-2 protein virus-like particle (M2e VLP)

M2e VLP was previously described as a vaccine that incorporates the extracellular region of the matrix 2 protein (M2e), which is highly conserved amongst all the strains of influenza. In this study, we analyzed activation status of dendritic cells (DCs) after exposure to M2e VLP, stimulating DCs with M2e VLP and co-culturing the stimulated DCs with T cells to observe innate and adaptive immune responses. The M2e VLP microparticle was prepared by encapsulating into a polymer matrix using the one-step spray drying method. Adjuvants Alhydrogel®, MPL-A® or AddavaxTM were used to enhance the DC stimulatory effects by the M2e VLP microparticle. The M2e VLP microparticle yield was found to be 92% and the encapsulation yield was around 84% with a size of approximately 2.78 μm. There was no short-term cytotoxicity found in DCs and macrophages with concentrations up to 1500 μg/mL of M2e VLP microparticle, however long-term exposure resulted in 25% decrease in viability of cells with concentrations more than or equal to 500 μg/mL. The M2e VLP microparticle vaccine with Alhydrogel® and MPL-A® induced high levels of TNFα in both DCs and macrophages. The high levels of MHC I, II, CD28, B7-1, ICAM-1, LFA-1 expression and IL-12 release in the M2e VLP microparticle group with Alhydrogel® suggests that the M2e VLP vaccine with this adjuvant activated T cells via the Th2 pathway. The increased expression of MHC I, II, CD40, CD154, ICAM-1 and LFA-1 on DCs and the release of IL-12 in the M2e VLP microparticle culture of DCs with MPL-A® demonstrated that the M2e VLP vaccine with this adjuvant activated T cells via the Th1 pathway. The decrease in fluorescence in the Alhydrogel® and MPL-A® group illustrates the proliferation of T cells took place following exposure of DCs to the M2e VLP microparticle with these adjuvants. The M2e VLP microparticle exhibited higher stimulatory responses of DCs than the M2e VLP in suspension. Furthermore, the presence of Alhydrogel® and MPL-A® enhanced the stimulatory effects of DCs by the M2e VLP microparticle (MP) vaccine.

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.

Immunogenicity Assessment of Cell Wall Carbohydrates of Group A Streptococcus via Self-Adjuvanted Glyco-lipopeptides

Identifying the immunogenic moieties and their precise structure of carbohydrates plays an important role for developing effective carbohydrate-based subunit vaccines. This study assessed the structure-immunogenicity relationship of carbohydrate moieties of a single repeating unit of group A carbohydrate (GAC) present on the cell wall of group A Streptococcus (GAS) using a rationally designed self-adjuvanted lipid-core peptide, instead of a carrier protein. Immunological evaluation of fully synthetic glyco-lipopeptides (particle size: 300-500 nm) revealed that construct consisting of higher rhamnose moieties (trirhamnosyl-lipopeptide) was able to induce enhanced immunogenic activity in mice, and GlcNAc moiety was not found to be an essential component of immunogenic GAC mimicked epitope. Trirhamnosyl-lipopeptide also showed 75-97% opsonic activity against four different clinical isolates of GAS and was comparable to a subunit peptide vaccine (J8-lipopeptide) which illustrated 65-96% opsonic activity.

Nano-based approaches in the development of antiviral agents and vaccines

Outbreaks and the rapid transmission of viruses, such as coronaviruses and influenza viruses, are serious threats to human health. A major challenge in combating infectious diseases caused by viruses is the lack of effective methods for prevention and treatment. Nanotechnology has provided a basis for the development of novel antiviral strategies. Owing to their large modifiable surfaces that can be functionalized with multiple molecules to realize sophisticated designs, nanomaterials have been developed as nanodrugs, nanocarriers, and nano-based vaccines to effectively induce sufficient immunologic memory. From this perspective, we introduce various nanomaterials with diverse antiviral mechanisms and summarize how nano-based antiviral agents protect against viral infection at the molecular, cellular, and organismal levels. We summarize the applications of nanomaterials for defense against emerging viruses by trapping and inactivating viruses and inhibiting viral entry and replication. We also discuss recent progress in nano-based vaccines with a focus on the mechanisms by which nanomaterials contribute to immunogenicity. We further describe how nanotechnology may improve vaccine efficacy by delivering large amounts of antigens to target immune cells and enhancing the immune response by mimicking viral structures and activating dendritic cells. Finally, we provide an overview of future prospects for nano-based antiviral agents and vaccines.

Chitosan surface modified PLGA nanoparticles loaded with brigatinib for the treatment of non-small cell lung cancer

In the current study, surface-modified poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) of brigatinib (BRB) were prepared by studying the variables PLGA (polymer), PVA (stabilizer) and chitosan (coater) against experimentally obtained responses. The optimized NPs (F2) were evaluated in vitro for differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size, polydispersity index (PDI) and drug entrapment (EE), in vitro release, hematocompatibility and in vitro anticancer studies. The optimized NPs’ (F2) composition, PLGA (75 mg), PVA (0.55% w/v), chitosan (0.75% w/v) and 30 mg of BRB was found to be optimum with particle size (406.3 ± 5.1 nm), PDI (0.277), ζ potential (30.4 ± 3.3 mV) and %EE (82.32%). The in vitro release profile showed a sustained release pattern of the F2 nanoparticles of BRB. The 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay revealed a significant anticancer activity for F2 NPs against A549 cell lines in comparison to free BRB. The result obtained in this work indicated the immense potential of nanoparticles to effectively deliver the BRB to the cancer site for the treatment of non-small cell lung cancer.

Determining Immune and miRNA Biomarkers Related to Respiratory Syncytial Virus (RSV) Vaccine Types

Respiratory Syncytial Virus (RSV) causes serious respiratory tract illness and substantial morbidity and some mortality in populations at the extremes of age, i.e., infants, young children, and the elderly. To date, RSV vaccine development has been unsuccessful, a feature linked to the lack of biomarkers available to assess the safety and efficacy of RSV vaccine candidates. We examined microRNAs (miR) as potential biomarkers for different types of RSV vaccine candidates. In this study, mice were vaccinated with a live attenuated RSV candidate that lacks the small hydrophobic (SH) and attachment (G) proteins (CP52), an RSV G protein microparticle (GA2-MP) vaccine, a formalin-inactivated RSV (FI-RSV) vaccine or were mock-treated. Several immunological endpoints and miR expression profiles were determined in mouse serum and bronchoalveolar lavage (BAL) following vaccine priming, boost, and RSV challenge. We identified miRs that were linked with immunological parameters of disease and protection. We show that miRs are potential biomarkers providing valuable insights for vaccine development.

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.

Nanoformulations: A Valuable Tool in the Therapy of Viral Diseases Attacking Humans and Animals

Various viruses can be considered as one of the most frequent causes of human diseases, from mild illnesses to really serious sicknesses that end fatally. Numerous viruses are also pathogenic to animals and plants, and many of them, mutating, become pathogenic also to humans. Several cases of affecting humans by originally animal viruses have been confirmed. Viral infections cause significant morbidity and mortality in humans, the increase of which is caused by general immunosuppression of the world population, changes in climate, and overall globalization. In spite of the fact that the pharmaceutical industry pays great attention to human viral infections, many of clinically used antivirals demonstrate also increased toxicity against human cells, limited bioavailability, and thus, not entirely suitable therapeutic profile. In addition, due to resistance, a combination of antivirals is needed for life-threatening infections. Thus, the development of new antiviral agents is of great importance for the control of virus spread. On the other hand, the discovery and development of structurally new antivirals represent risks. Therefore, another strategy is being developed, namely the reformulation of existing antivirals into nanoformulations and investigation of various metal and metalloid nanoparticles with respect to their diagnostic, prophylactic, and therapeutic antiviral applications. This chapter is focused on nanoscale materials/formulations with the potential to be used for the treatment or inhibition of the spread of viral diseases caused by human immunodeficiency virus, influenza A viruses (subtypes H3N2 and H1N1), avian influenza and swine influenza viruses, respiratory syncytial virus, herpes simplex virus, hepatitis B and C viruses, Ebola and Marburg viruses, Newcastle disease virus, dengue and Zika viruses, and pseudorabies virus. Effective antiviral long-lasting and target-selective nanoformulations developed for oral, intravenous, intramuscular, intranasal, intrarectal, intravaginal, and intradermal applications are discussed. Benefits of nanoparticle-based vaccination formulations with the potential to secure cross protection against divergent viruses are outlined as well.

Efficient Delivery of Tyrosinase Related Protein-2 (TRP2) Peptides to Lymph Nodes using Serum-Derived Exosomes

Exosomes (EXO) are considered to be versatile carriers for biomolecules; however, the delivery of therapeutic peptides using EXOs poses several challenges. In this study, the efficiency of serum-derived EXOs in delivering tyrosinase-related protein-2 (TRP2) peptides to lymph nodes is determined. TRP2 peptides are successfully incorporated into EXOs, which show a uniform and narrow size distribution of around 45 nm. The TRP2-incorporated exosomes (EXO-TRP2) are efficiently internalized into macrophages and dendritic cells, and are seen to display a punctate distribution. EXOs loaded with TRP2 together with MPLA, (EXO-MPLA-TRP2) result in a strong release of proinflammatory cytokines (TNF-α and IL-6) from both RAW264.7 and DC2.4 cells. Finally, subcutaneous injection of fluorescently labeled EXO-TRP2 followed by ex vivo imaging using in vivo imaging system (IVIS) show a strong fluorescent signal in the lymph nodes after only 1 h, which is maintained until at least 4 h after injection. Taken together, the findings suggest that serum-derived EXOs can serve as promising carriers to deliver therapeutic peptides to lymph nodes for immunotherapy.

Engineering and evaluation of amyloid assemblies as a nanovaccine against the Chikungunya virus

The design of nanoparticles exposing a high density of antigens constitutes a promising strategy to address safety concerns of conventional life-attenuated vaccines as well as to increase the immunogenicity of subunit vaccines. In this study, we developed a fully synthetic nanovaccine based on an amyloid peptide sequence with high self-assembling properties. The immunogenic epitope E2EP3 from the E2 glycoprotein of the Chikungunya virus was used to evaluate the potential of a 10-mer peptide derived from an endogenous amyloidogenic polypeptide as a novel vaccine platform. Chimeric peptides, comprising the peptide antigen attached to the amyloid core by a short flexible linker, were prepared by solid phase synthesis. As observed using atomic force microscopy, these polypeptides self-assembled into linear and unbranched fibrils with a diameter ranging from 6 to 8 nm. A quaternary conformation rich in cross-β-sheets characterized these assemblies, as demonstrated by circular dichroism spectroscopy and thioflavin T fluorescence. ELISA assays and transmission electronic microscopy of immunogold labeled-fibrils revealed a high density of the Chikungunya virus E2 glycoprotein derived epitope exposed on the fibril surface. These amyloid fibrils were cytocompatible and were efficiently uptaken by macrophages. Mice immunization revealed a robust IgG response against the E2EP3 epitope, which was dependent on self-assembly and did not require co-injection of the Alhydrogel adjuvant. These results indicate that cross-β-sheet amyloid assemblies constitute suitable synthetic self-adjuvanted assemblies to anchor antigenic determinants and to increase the immunogenicity of peptide epitopes.

Respiratory Tract Deposition and Distribution Pattern of Microparticles in Mice Using Different Pulmonary Delivery Techniques

Pulmonary delivery of drugs and vaccines is an established route of administration, with particulate-based carriers becoming an attractive strategy to enhance the benefits of pulmonary therapeutic delivery. Despite the increasing number of publications using the pulmonary route of delivery, the lack of effective and uniform administration techniques in preclinical models generally results in poor translational success. In this study, we used the IVIS Spectrum small-animal in vivo imaging system to compare the respiratory tract deposition and distribution pattern of a microsphere suspension (5 µm) in mice after 1, 4, and 24 h when delivered by oropharyngeal aspiration, the Microsprayer® Aerosolizer, and the BioLite Intubation System, three-widely reported preclinical inhalation techniques. We saw no significant differences in microsphere deposition in whole body images and excised lungs (at 1, 4, and 24 h); however, the three-dimensional (3D) images showed more localized deposition in the lungs with the MicroSprayer® and BioLite delivery techniques. Further, oropharyngeal aspiration (at 1 h) showed microsphere deposition in the oral cavity, in contrast to the MicroSprayer® and BioLite systems. The studies shown here will allow researchers to choose the appropriate pulmonary delivery method in animal models based on their study requirements.

Nanoparticles for Signaling in Biodiagnosis and Treatment of Infectious Diseases

Advances in nanoparticle-based systems constitute a promising research area with important implications for the treatment of bacterial infections, especially against multidrug resistant strains and bacterial biofilms. Nanosystems may be useful for the diagnosis and treatment of viral and fungal infections. Commercial diagnostic tests based on nanosystems are currently available. Different methodologies based on nanoparticles (NPs) have been developed to detect specific agents or to distinguish between Gram-positive and Gram-negative microorganisms. Also, biosensors based on nanoparticles have been applied in viral detection to improve available analytical techniques. Several point-of-care (POC) assays have been proposed that can offer results faster, easier and at lower cost than conventional techniques and can even be used in remote regions for viral diagnosis. Nanoparticles functionalized with specific molecules may modulate pharmacokinetic targeting recognition and increase anti-infective efficacy. Quorum sensing is a stimuli-response chemical communication process correlated with population density that bacteria use to regulate biofilm formation. Disabling it is an emerging approach for combating its pathogenicity. Natural or synthetic inhibitors may act as antibiofilm agents and be useful for treating multi-drug resistant bacteria. Nanostructured materials that interfere with signal molecules involved in biofilm growth have been developed for the control of infections associated with biofilm-associated infections.

Potency of a Scalable Nanoparticulate Subunit Vaccine

Nanoparticulate vaccines can potentiate immune responses by site-specific drainage to lymph nodes (LNs). This approach may benefit from a nanoparticle engineering method with fine control over size and codelivery of antigen and adjuvant. Here, we applied the flash nanocomplexation (FNC) method to prepare nanovaccines via polyelectrolyte complexation of chitosan and heparin to coencapsulate the VP1 protein antigen from enterovirus 71, which causes hand-foot-mouth disease (HFMD), with tumor necrosis factor α (TNF) or CpG as adjuvants. FNC allows for reduction of the nanovaccine size to range from 90 to 130 nm with relatively narrower size distribution and a high payload capacity. These nanovaccines reached both proximal and distal LNs via subcutaneous injection and subsequently exhibited prolonged retention in the LNs. The codelivery induced strong immune activation toward a Th1 response in addition to a potent Th2 response, and conferred effective protection against lethal virus challenge comparable to that of an approved inactivated viral vaccine in mouse models of both passive and active immunization setting. In addition, these nanovaccines also elicited strong IgA titers, which may offer unique advantages for mucosal protection. This study addresses the issues of size control, antigen bioactivity retention, and biomanufacturing to demonstrate the translational potential of a subunit nanovaccine design.

Respiratory Syncytial Virus Vaccine Approaches: a Current Overview

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) is a global human pathogen responsible for lower respiratory tract infections (LRTI). While RSV infection is innocuous in healthy adults, it is the leading cause of infant hospitalization for respiratory tract infection. Nearly everyone shows evidence of an RSV infection by the age of 3. However, there is still not a vaccine commercially available. This review will provide an update on the clinical and preclinical vaccine studies and different approaches to prevent RSV infection.

RECENT FINDINGS

Novel vaccine approaches that induce protection against RSV without enhancement of respiratory tract disease.

SUMMARY

Recent technological approaches have led to generation of different strategies to prevent RSV infection, including live attenuated, chimeric, and subunit vaccines, virus-like particles, and nanoparticles. These vaccine approaches represent promising candidates towards an efficient RSV vaccine that effectively protects infants, children, and adults.

Ongoing developments in RSV prophylaxis: a clinician's analysis

Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children worldwide. Lower respiratory tract infection due to RSV is one of the most common causes of hospitalization for infants, especially those born premature or with chronic lung or heart disease. Furthermore, RSV infection is an important cause of morbidity in adults, particularly in the elderly and immunocompromised individuals. The acute phase of this infection is often followed by episodes of wheezing that recur for months or years and usually lead to a physician diagnosis of asthma. RSV was discovered more than 50 years ago, and despite extensive research to identify pharmacological therapies, the most effective management of this infection remains supportive care. The trial of a formalin-inactivated RSV vaccine in the 1960s resulted in priming the severe illness upon natural infection. Currently, Palivizumab is the only available option for RSV prophylaxis, and because of restricted clinical benefits and high costs, it has been limited to a group of high-risk infants. There are several ongoing trials in preclinical, Phase-I, Phase-II, or Phase-III clinical stages for RSV vaccine development based on various strategies. Here we review the existing available prophylactic options, the current stages of RSV vaccine clinical trials, different strategies, and major hurdles in the development of an effective RSV vaccine.