A viral-vectored RSV vaccine induces long-lived humoral immunity in cotton rats

Intranasal Inoculation of Cationic Crosslinked Carbon Dots-Adjuvanted Respiratory Syncytial Virus F Subunit Vaccine Elicits Mucosal and Systemic Humoral and Cellular Immunity

Respiratory syncytial virus (RSV) causes severe acute lower respiratory tract infections, especially in infants and the elderly. Developing an RSV vaccine that promotes a robust mucosal immune response is necessary to successfully prevent viral transmission and the development of severe disease. We previously reported that crosslinked carbon dots (CCD) may be an excellent adjuvant candidate for intranasal (IN) protein subunit vaccines. Considering the strong immunogenicity of RSV prefused F protein (preF), we prepared an IN RSV vaccine composed of the CCD adjuvant and the preF protein as antigen (CCD/preF) and evaluated the induced antigen-specific humoral and cellular immunity. We found that IN immunization with the CCD/preF vaccine elicited strong serum IgG responses and mucosal immunity, including secreted IgA antibodies, tissue-resident memory T (TRM) cells, and antigen-specific B cells, which lasted for at least 1 year. In addition, a combination of intramuscular and IN immunization with CCD/preF vaccine induced stronger systemic and mucosal immunity. Together, this study proved the high immunogenicity of the CCD/preF vaccines and supported the university of the mucosal CCD adjuvant, supporting further development of the CCD/preF vaccine in larger animal models and clinical studies.

A bivalent mRNA vaccine against RSV infection in rodent models

Because of the higher conservation of RSV Fusion (F) protein than the glycoprotein (G) across RSV strains and serotypes, the majority of vaccine candidates targets to viral fusion protein (F) rather than glycoprotein to elicit a broader range of protective neutralizing antibodies from infection. In this study, we screened two chemically modified mRNA vaccines expressing RSV prefusion stabilized protein (preF) targeting RSV A2 and B subtypes. After immunization, the antigen-specific binding antibody, neutralizing antibody, and T cell-mediated immune response were evaluated. After challenge with live RSV A2 virus in cotton rats, the protection and safety of vaccine was further evaluated. The results showed that the mRNA vaccine candidates elicited robust antigen-specific binding antibody, neutralizing antibody responses and Th1-biased T-cell responses in both mice and cotton rats. Moreover, cotton rats vaccinated with mRNA vaccine, lung pathology and lung infectious viral loads were significantly reduced, and no vaccine enhanced respiratory disease (VERD) happened. These results collectively demonstrated that mRNA-based vaccine induced strong humoral and cellular immunity, provided outstanding protection against both RSV A2 and RSV B subtypes in rodent animals as well. Our data demonstrated that these mRNA vaccines should be further evaluated in clinical trials.

Cold-adapted influenza vaccine carrying three repeats of a respiratory syncytial virus (RSV) fusion glycoprotein epitope site protects BALB/c mice and cotton rats against RSV infection

Respiratory syncytial virus is the major cause of respiratory viral infections, particularly in infants, immunocompromised populations, and the elderly (over 65 years old), the prevention of RSV infection has become a priority. In this study, we generated a chimeric influenza virus, termed LAIV/RSV/HA-3F, using reverse genetics technology which contained three repeats of the RSV fusion protein neutralizing epitope site II to the N terminal in the background of the hemagglutinin (HA) gene of cold adapted influenza vaccine A/California/7/2009 ca. LAIV/RSV/HA-3F exhibited cold-adapted (ca) and attenuated (att) phenotype. BALB/c mice immunized intranasally with LAIV/RSV/HA-3F showed robust immunogenicity, inducing viral-specific antibody responses against both influenza and RSV, eliciting RSV-specific humoral, cellular and mucosal immune responses. LAIV/RSV/HA-3F also conferred protection as indicated by reduced viral titers and improved lung histopathological alterations against live RSV virus challenge. Mechanismly, single-cell RNA sequencing (scRNA-seq) and single-cell T cell antigen receptor (TCR) sequencing were employed to characterize the immune responses triggered by chimeric RSV vaccine, displaying that LAIV/RSV/HA-3F provided protection mainly via interferon-γ (IFN-γ). Moreover, we found that LAIV/RSV/HA-3F significantly inhibited viral replication in the challenged lung and protected against subsequent RSV challenge in cotton rats without causing lung disease. Taken together, our findings demonstrated that LAIV/RSV/HA-3F has potential as a promising bivalent vaccine with dual purpose candidate for the prevention of influenza and RSV, and preclinical and clinical studies warrant further investigations.

Advantages and challenges of Newcastle disease virus as a vector for respiratory mucosal vaccines

Newcastle disease virus (NDV) is an avian pathogen with an unsegmented negative-strand RNA genome. Properties such as the ease of genome modification, respiratory tract tropism, and self-limiting replication in mammals make NDV an attractive vector for vaccine development. Experimental NDV-based vaccines against multiple human and animal pathogens elicited both systemic and mucosal immune responses and were protective in preclinical animal studies, but their real-life efficacy remains to be demonstrated. Only recently, the first results of clinical trials of NDV-based vaccines against SARS-CoV-2 became available, highlighting the challenges that need to be overcome to fully realize the potential of NDV as a platform for the rapid development of economically affordable and effective mucosal vaccines.

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

An intranasal recombinant NDV-BRSV Fopt vaccine is safe and reduces lesion severity in a colostrum-deprived calf model of RSV infection

Human respiratory syncytial virus (HRSV) is a major cause of severe lower respiratory tract disease in infants and the elderly, yet no safe, effective vaccine is commercially available. Closely related bovine RSV (BRSV) causes respiratory disease in young calves, with many similar features to those seen in HRSV. We previously showed that a Newcastle disease virus (NDV)-vectored vaccine expressing the F glycoprotein of HRSV reduced viral loads in lungs of mice and cotton rats and protected from HRSV. However, clinical signs and pathogenesis of disease in laboratory animals following HRSV infection differs from that observed in human infants. Thus, we examined whether a similar vaccine would protect neonatal calves from BRSV infection. Codon-optimized rNDV vaccine (rNDV-BRSV F_opt) was constructed and administered to colostrum-deprived calves. The rNDV-BRSV F_opt vaccine was well-tolerated and there was no evidence of vaccine-enhanced disease in the upper airways or lungs of these calves compared to the non-vaccinated calves. We found two intranasal doses reduces severity of gross and microscopic lesions and decreases viral load in the lungs. Furthermore, serum neutralizing antibodies were generated in vaccinated calves. Finally, reduced lung CXC chemokine levels were observed in vaccinated calves after BRSV challenge. In summary, we have shown that rNDV-BRSV F_opt vaccine is safe in colostrum-deprived calves, and is effective in reducing lung lesions, and decreasing viral load in upper respiratory tract and lungs after challenge.

Long-Lasting Protection Induced by a Polyanhydride Nanovaccine against Respiratory Syncytial Virus in an Outbred Mouse Model

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in children. In humans, natural infection with RSV affords only partial long-term protection from reinfection, and there is no licensed RSV vaccine currently available. We have developed a new vaccine candidate, termed RSVNanoVax, composed of polyanhydride nanoparticles encapsulating the RSV prefusion F protein and a CpG 1668 oligodeoxynucleotide adjuvant. We recently reported that vaccination of inbred BALB/c mice with RSVNanoVax induced both RSV-specific cellular and humoral immunity, which provided protection from viral replication and RSV-induced disease. To further assess the efficacy of RSVNanoVax, here, we utilized outbred Swiss Webster mice to examine vaccine efficacy in a more genetically diverse population. Following intranasal prime-boost vaccination with RSVNanoVax, Swiss Webster mice exhibited robust titers of systemic RSV F-directed IgG antibodies and RSV F-directed IgA within the lungs and nasal passages that were sustained out to at least 1 year post-vaccination. Serum antibodies maintained robust neutralizing activity against both RSV A and B strains. Following RSV challenge, vaccinated Swiss Webster mice exhibited rapid viral clearance from the lungs. Overall, our results indicate that RSVNanoVax represents a promising RSV vaccine candidate capable of providing long-term protection and immunity in a genetically diverse population. IMPORTANCE Respiratory syncytial virus (RSV) infection causes thousands of infections and deaths in children and elderly adults each year. Research in this field is of great importance as there remains no licensed vaccine to prevent RSV infections. We developed a novel vaccine candidate, RSVNanoVax, utilizing the RSV prefusion F protein encapsulated in polyanhydride nanoparticles. Here, we show that the intranasal delivery of RSVNanoVax protected outbred mice from viral replication within the lungs when challenged with RSV out to 1 year post-vaccination. Additionally, RSV-specific antibody responses were generated in both the serum and lung tissue and sustained long-term. These results demonstrate that our vaccine is an encouraging candidate for driving long-term protection in the lungs in a genetically diverse population.

From animal studies into clinical trials: the relevance of animal models to develop vaccines and therapies to reduce disease severity and prevent hRSV infection

INTRODUCTION

Human respiratory syncytial virus (hRSV) is an important cause of lower respiratory tract infections in the pediatric and the geriatric population worldwide. There is a substantial economic burden resulting from hRSV disease during winter. Although no vaccines have been approved for human use, prophylactic therapies are available for high-risk populations. Choosing the proper animal models to evaluate different vaccine prototypes or pharmacological treatments is essential for developing efficient therapies against hRSV.

AREAS COVERED

This article describes the relevance of using different animal models to evaluate the effect of antiviral drugs, pharmacological molecules, vaccine prototypes, and antibodies in the protection against hRSV. The animal models covered are rodents, mustelids, bovines, and nonhuman primates. Animals included were chosen based on the available literature and their role in the development of the drugs discussed in this manuscript.

EXPERT OPINION

Choosing the correct animal model is critical for exploring and testing treatments that could decrease the impact of hRSV in high-risk populations. Mice will continue to be the most used preclinical model to evaluate this. However, researchers must also explore the use of other models such as nonhuman primates, as they are more similar to humans, prior to escalating into clinical trials.

Mucosal delivery of RNA vaccines by Newcastle disease virus vectors

The rapid evolution of SARS-CoV-2 since its pandemic outbreak has underscored the need for improved SARS-CoV-2 vaccines that efficiently reduce not only hospitalizations and deaths, but also infections and transmission. This might be achieved by a new generation of intranasally administered SARS-CoV-2 vaccines to stimulate protective mucosal immunity. Among all different approaches, preclinical and clinical information using Newcastle Disease Virus (NDV)-vectors expressing S of SARS-CoV2 as a COVID-19 vaccine show the potential of this vaccine platform as an affordable, highly immunogenic, safe strategy to intranasally vaccinate humans against SARS-CoV-2 and other infectious diseases. These vaccine vectors consist on the use of a harmless avian negative strand RNA virus to deliver intranasally a self-replicating RNA expressing the vaccine antigen in the cells of the respiratory mucosa. The vector also incorporates the antigen in the virus particle used for RNA delivery, thus combining the properties of nanoparticle-based and RNA-based vaccines. Other advantages of NDV-based vectors include the worldwide availability of manufacturing facilities for their production and their stability at non-freezing temperatures. While phase 3 clinical studies to evaluate efficacy are still pending, phase 1 and 2 clinical studies have demonstrated the safety and immunogenicity of NDV-S vaccines against SARS-CoV-2.

A Newcastle disease virus expressing a stabilized spike protein of SARS-CoV-2 induces protective immune responses

Rapid development of COVID-19 vaccines has helped mitigating SARS-CoV-2 spread, but more equitable allocation of vaccines is necessary to limit the global impact of the COVID-19 pandemic and the emergence of additional variants of concern. We have developed a COVID-19 vaccine candidate based on Newcastle disease virus (NDV) that can be manufactured at high yields in embryonated eggs. Here, we show that the NDV vector expressing an optimized spike antigen (NDV-HXP-S) is a versatile vaccine inducing protective antibody responses. NDV-HXP-S can be administered intramuscularly as inactivated vaccine or intranasally as live vaccine. We show that NDV-HXP-S GMP-produced in Vietnam, Thailand and Brazil is effective in the hamster model. Furthermore, we show that intramuscular vaccination with NDV-HXP-S reduces replication of tested variants of concerns in mice. The immunity conferred by NDV-HXP-S effectively counteracts SARS-CoV-2 infection in mice and hamsters.

Immunogenicity and inflammatory properties of respiratory syncytial virus attachment G protein in cotton rats

Human respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection in infants and young children worldwide. The attachment (G) protein of RSV is synthesized by infected cells in both a membrane bound (mG) and secreted form (sG) and uses a CX3C motif for binding to its cellular receptor. Cell culture and mouse studies suggest that the G protein mimics the cytokine CX3CL1 by binding to CX3CR1 on immune cells, which is thought to cause increased pulmonary inflammation in vivo. However, because these studies have used RSV lacking its G protein gene or blockade of the G protein with a G protein specific monoclonal antibody, the observed reduction in inflammation may be due to reduced virus replication and spread, and not to a direct role for G protein as a viral chemokine. In order to more directly determine the influence of the soluble and the membrane-bound forms of G protein on the immune system independent of its attachment function for the virion, we expressed the G protein in cotton rat lungs using adeno-associated virus (AAV), a vector system which does not itself induce inflammation. We found no increase in pulmonary inflammation as determined by histology and bronchoalveolar lavage after inoculation of AAVs expressing the membrane bound G protein, the secreted G protein or the complete G protein gene which expresses both forms. The long-term low-level expression of AAV-G did, however, result in the induction of non-neutralizing antibodies, CD8 T cells and partial protection from challenge with RSV. Complete protection was accomplished through co-immunization with AAV-G and an AAV expressing cotton rat interferon α.

The resistance against Trichinella spiralis infection induced by primary infection with respiratory syncytial virus

Human infections with Trichinella spiralis and respiratory syncytial virus (RSV) are common, as T. spiralis infections are re-emerging in various parts of the world and RSV infections remain a threat for infants. Yet, studies investigating the relationship pertaining to the two are severely lacking. In particular, immune response induction via RSV and T. spiralis remain largely elusive. Here, we investigated the resistance against T. spiralis infection induced upon primary infection with RSV. RSV, notorious for causing severe inflammatory reaction in the lungs, were intranasally infected, followed with a T. spiralis infection in mice. Our results revealed that primary RSV infection in mice significantly raised T. spiralis-specific and total IgE, IgG and its subclass antibody responses upon T. spiralis challenge infection (RSV-Ts). Blood eosinophil levels were decreased in RSV-Ts, accompanied with significant increase in both Th1 and Th2 cytokines. Antibodies generated against RSV in RSV-infected mice were found to react with T. spiralis excretory/secretory antigen, showing several bands determined through immunoblotting. RSV-Ts also had a marked reduction of T. spiralis worm burden in diaphragm. These results indicate that immune responses induced by RSV infection contribute to resistance against subsequent T. spiralis infection.