The path to an RSV vaccine

Exacerbated lung inflammation in offspring with high maternal antibody levels following secondary RSV exposure

Respiratory syncytial virus (RSV) is the primary cause of bronchiolitis-related hospitalizations among children under 5 years of age, with reinfection being common throughout life. Maternal vaccination has emerged as a promising strategy, delivering elevated antibody levels to newborns for immediate protection. However, limited research has explored the protective efficacy of maternal antibodies (matAbs) against secondary RSV infections in offspring. To address this gap, we employed a mouse model of maternal RSV vaccination and secondary infection of offspring to evaluate lung pathology following RSV reinfection in mice with varying levels of maternal antibody (matAb). Additionally, we aimed to investigate the potential causes of exacerbated lung inflammation in offspring with high matAb levels following secondary RSV exposure. Our findings revealed that offspring with elevated levels of maternal pre-F antibody demonstrated effective protection against lung pathology following the initial RSV infection. However, this protection was compromised upon reinfection, manifesting as heightened weight loss, exacerbated lung pathology, increased expression of RSV-A N genes, eosinophilia, enhanced IL-5, IL-13, MUC5AC, and eosinophils Major Basic Protein (MBP) production in lung tissue compared to offspring lacking matAbs. Importantly, these unexpected outcomes were not attributed to antibody-dependent enhancement (ADE) resulting from declining matAb levels over time. Notably, our findings showed a decline in secretory IgA (sIgA), mucosal IgA, and mucosal IgG levels in offspring with high matAb levels post-primary RSV challenge. We propose that this decline may be a critical factor contributing to the ineffective protection observed during secondary RSV exposure. Overall, these findings offer valuable insights into maternal vaccination against RSV, contributing to a comprehensive understanding and mitigation of potential risks associated with maternal RSV vaccination.

Nanomedicine at the Pulmonary Frontier: Immune-Centric Approaches for Respiratory Disease Treatment

Respiratory diseases (RD) are a group of common ailments with a rapidly increasing global prevalence, posing a significant threat to humanity, especially the elderly population, and imposing a substantial burden on society and the economy. RD represents an unmet medical need that requires the development of viable pharmacotherapies. While various promising strategies have been devised to advance potential treatments for RD, their implementation has been hindered by difficulties in drug delivery, particularly in critically ill patients. Nanotechnology offers innovative solutions for delivering medications to the inflamed organ sites, such as the lungs. Although this approach is enticing, delivering nanomedicine to the lungs presents complex challenges that require sophisticated techniques. In this context, we review the potential of novel nanomedicine-based immunomodulatory strategies that could offer therapeutic benefits in managing this pressing health condition.

Nanovaccines for Advancing Long-Lasting Immunity against Infectious Diseases

Infectious diseases, particularly life-threatening pathogens such as small pox and influenza, have substantial implications on public health and global economies. Vaccination is a key approach to combat existing and emerging pathogens. Immunological memory is an essential characteristic used to evaluate vaccine efficacy and durability and the basis for the long-term effects of vaccines in protecting against future infections; however, optimizing the potency, improving the quality, and enhancing the durability of immune responses remains challenging and a focus for research involving investigation of nanovaccine technologies. In this review, we describe how nanovaccines can address the challenges for conventional vaccines in stimulating adaptive immune memory responses to protect against reinfection. We discuss protein and nonprotein nanoparticles as useful antigen platforms, including those with highly ordered and repetitive antigen array presentation to enhance immunogenicity through cross-linking with multiple B cell receptors, and with a focus on antigen properties. In addition, we describe how nanoadjuvants can improve immune responses by providing enhanced access to lymph nodes, lymphnode targeting, germinal center retention, and long-lasting immune response generation. Nanotechnology has the advantage to facilitate vaccine induction of long-lasting immunity against infectious diseases, now and in the future.

Vaccine-associated enhanced disease in humans and animal models: Lessons and challenges for vaccine development

The fight against infectious diseases calls for the development of safe and effective vaccines that generate long-lasting protective immunity. In a few situations, vaccine-mediated immune responses may have led to exacerbated pathology upon subsequent infection with the pathogen targeted by the vaccine. Such vaccine-associated enhanced disease (VAED) has been reported, or at least suspected, in animal models, and in a few instances in humans, for vaccine candidates against the respiratory syncytial virus (RSV), measles virus (MV), dengue virus (DENV), HIV-1, simian immunodeficiency virus (SIV), feline immunodeficiency virus (FIV), severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1), and the Middle East respiratory syndrome coronavirus (MERS-CoV). Although alleviated by clinical and epidemiological evidence, a number of concerns were also initially raised concerning the short- and long-term safety of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is causing the ongoing COVID-19 pandemic. Although the mechanisms leading to this phenomenon are not yet completely understood, the individual and/or collective role of antibody-dependent enhancement (ADE), complement-dependent enhancement, and cell-dependent enhancement have been highlighted. Here, we review mechanisms that may be associated with the risk of VAED, which are important to take into consideration, both in the assessment of vaccine safety and in finding ways to define models and immunization strategies that can alleviate such concerns.

Epidemiological features, risk factors and disease burden of respiratory viruses among hospitalized children with acute respiratory tract infections in Xiamen, China

Well-established surveillance and monitoring system for respiratory viruses need be improved and epidemiological data about respiratory viruses is scarce in China. This study aimed to investigate epidemiological characteristics of respiratory viruses among hospitalized children ≤ 2 years old with acute respiratory tract infections (ARTIs) in Xiamen, China from October 2014 to September 2017. The clinical records of 7248 children hospitalized for ARTIs were analyzed retrospectively. Respiratory syncytial virus (RSV) (22.3%) was the most common virus among hospitalized children ≤ 2 years old, followed by parainfluenza (5.0%), adenovirus (3.5%) and influenza (1.7%). RSV-infected children possessed a higher disease burden including higher ICU admission rate (12.7%) and hospital charges ($635.36). Especially, infants < 6 months of age had the highest risk of RSV infection (OR= 2.4, 95% CI: 1.9-2.9) and higher ICU admission rate (12.1% vs. 4.5%, 4.6%) and hospital costs ($923.3 vs. $785.5, $811.7) than other age groups. Therefore, infants aged 0-6 months, especially premature infants and children with congenital diseases, should receive more concern. There is an urgent need to develop effective immunization strategies to protect these infants through the first 6 months of life or RSV season.

Molecular Evolution of Attachment Glycoprotein (G) and Fusion Protein (F) Genes of Respiratory Syncytial Virus ON1 and BA9 Strains in Xiamen, China

Monitoring viral transmission and analyzing the genetic diversity of a virus are imperative to better understand its evolutionary history and the mechanism driving its evolution and spread. Especially, effective monitoring of key antigenic mutations and immune escape variants caused by these mutations has great scientific importance. Thus, to further understand the molecular evolutionary dynamics of respiratory syncytial virus (RSV) circulating in China, we analyzed nasopharyngeal swab specimens derived from hospitalized children ≤5 years old with acute respiratory tract infections (ARIs) in Xiamen during 2016 to 2019. We found that infants under 6 months of age (52.0%) were the main population with RSV infection. The prevalent pattern "BBAA" of RSV was observed during the epidemic seasons. RSV ON1 and BA9 genotypes were the dominant circulating strains in Xiamen. Interestingly, we observed four Xiamen-specific amino acid substitution combinations in the G protein and several amino acid mutations primarily occurring at antigenic sites Ø and V in the F protein. Our analyses suggest that introduction of new viruses and local evolution are shaping the diversification of RSV strains in Xiamen. This study provides new insights on the evolution and spread of the ON1 and BA9 genotypes at local and global scales. IMPORTANCE Monitoring the amino acid diversity of the RSV G and F genes helps us to find the novel genotypes, key antigenic mutations affecting antigenicity, or neutralizing antibody-resistant variants produced by natural evolution. In this study, we analyzed the molecular evolution of G and F genes from RSV strains circulating in Xiamen, China. These data provide new insights on local and global transmission and could inform the development of control measures for RSV infections.

The burden of respiratory syncytial virus in children under 5 years of age in Norway

OBJECTIVES

To estimate age-specific incidence of medically attended respiratory syncytial virus (RSV) infections in hospitalised Norwegian children and describe disease epidemiology.

METHODS

Active prospective hospital surveillance for RSV in children <59 months of age was conducted during 2015-2018. All febrile children 12-59 months of age were enrolled, whereas children <12 months were enrolled based on respiratory symptoms regardless of fever. Surveillance data were linked to national registry data to estimate the clinical burden of RSV.

RESULTS

Of the children enrolled, 1096 (40%) were infected with RSV. The highest incidence rates were found in children 1 month of age, with a peak incidence of 43 per 1000 during the 2016-2017 season. In comparison, children 24-59 months of age had an infection rate of 1.4 per 1000 during the same winter season. The peak season was during the 2016-2017 winter, with an incidence rate of 6.0 per 1000 children 0-59 months of age. In the study population a total of 168 (15%) of the infected children had pre-existing medical conditions predisposing for more severe disease. High infection rates were found in this population.

CONCLUSIONS

Children with comorbidities showed high hospital contact rates, but the majority of children in need of medical attention associated with RSV infection were previously healthy.

Epidemiology of Respiratory Pathogens Among Children Hospitalized for Pneumonia in Xiamen: A Retrospective Study

OBJECTIVES

To investigate the etiology of common respiratory pathogens in children < 2 years of age hospitalized with pneumonia in Xiamen from 2014 to 2017.

METHODS

The medical records of 5581 children with pneumonia were retrospectively reviewed. Direct immunofluorescent test was used for respiratory virus testing. Bacteria were detected by conventional culture method. The results of pathogen detection at admission were analyzed as well as the clinical outcomes of children.

RESULTS

The burden of hospitalized children with pneumonia was highest among infants < 6 months old (58.2%). Respiratory syncytial virus (RSV) was the most common respiratory virus (26.0%) followed by parainfluenza (4.8%) and adenovirus (3.2%). Haemophilus influenzae was the most common bacteria detected (16.6%) followed by Moraxella catarrhalis (13.4%), Staphylococcus aureus (13.0%), Streptococcus pneumoniae (12.3%), Escherichia coli (5.1%) and Klebsiella pneumoniae (4.8%). Notably, RSV and K. pneumoniae were detected more frequently in severe pneumonia (35.0% and 10.9%) versus mild pneumonia (25.6% and 4.6%), with higher rates of ICU admissions, longer hospital stays and higher hospital costs compared to those infected with other respiratory pathogens.

CONCLUSIONS

Among children < 2 years of age hospitalized with pneumonia in Xiamen, RSV was the most common respiratory virus, while H. influenzae and S. pneumoniae remained the predominant bacterial pathogens detected. Considering the low implementation rate of vaccines against pneumococcal and Hib pneumonia in China, there is an urgent need to increase both vaccination rates to reduce pneumococcal and Hib disease burden.

Respiratory Syncytial Virus-Associated Hospital Admissions in Children Younger Than 5 Years in 7 European Countries Using Routinely Collected Datasets

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of respiratory tract infection (RTI) in young children. Registries provide opportunities to explore RSV epidemiology and burden.

METHODS

We explored routinely collected hospital data on RSV in children aged < 5 years in 7 European countries. We compare RSV-associated admission rates, age, seasonality, and time trends between countries.

RESULTS

We found similar age distributions of RSV-associated hospital admissions in each country, with the highest burden in children < 1 years old and peak at age 1 month. Average annual rates of RTI admission were 41.3-112.0 per 1000 children aged < 1 year and 8.6-22.3 per 1000 children aged < 1 year. In children aged < 5 years, 57%-72% of RTI admissions with specified causal pathogen were coded as RSV, with 62%-87% of pathogen-coded admissions in children < 1 year coded as RSV.

CONCLUSIONS

Our results demonstrate the benefits and limitations of using linked routinely collected data to explore epidemiology and burden of RSV. Our future work will use these data to generate estimates of RSV burden using time-series modelling methodology, to inform policymaking and regulatory decisions regarding RSV immunization strategy and monitor the impact of future vaccines.

Chimeric Measles Virus (MV/RSV), Having Ectodomains of Respiratory Syncytial Virus (RSV) F and G Proteins Instead of Measles Envelope Proteins, Induced Protective Antibodies against RSV

In our previous study, fusion (F) or glyco (G) protein coding sequence of respiratory syncytial virus (RSV) was inserted at the P/M junction of the measles AIK-C vector (MVAIK), and the recombinant measles virus induced protective immune responses. In the present study, the ectodomains of measles fusion (F) and hemagglutinin (HA) proteins were replaced with those of RSV F and G proteins, and a chimeric MV/RSV vaccine was developed. It expressed F and G proteins of RSV and induced cytopathic effect (CPE) in epithelial cell lines (Vero, A549, and HEp-2 cells), but not in lymphoid cell lines (B95a, Jurkat, and U937 cells). A chimeric MV/RSV grew similarly to AIK-C with no virus growth at 39 °C. It induced NT antibodies against RSV in cotton rats three weeks after immunization through intramuscular route and enhanced response was observed after the second dose at eight weeks. After the RSV challenge with 10⁶ PFU, significantly lower virus (10^1.4±0.1 PFU of RSV) was recovered from lung tissue in the chimeric MV/RSV vaccine group than in the MVAIK control group with 10^4.6±0.2 PFU (p < 0.001) and no obvious inflammatory pathological finding was noted. The strategy of ectodomain replacement in the measles virus vector is expected to lead to the development of safe and effective vaccines for other enveloped viruses.

Convergent structural features of respiratory syncytial virus neutralizing antibodies and plasticity of the site V epitope on prefusion F

Respiratory syncytial virus (RSV) is a global public health burden for which no licensed vaccine exists. To aid vaccine development via increased understanding of the protective antibody response to RSV prefusion glycoprotein F (PreF), we performed structural and functional studies using the human neutralizing antibody (nAb) RSB1. The crystal structure of PreF complexed with RSB1 reveals a conformational, pre-fusion specific site V epitope with a unique cross-protomer binding mechanism. We identify shared structural features between nAbs RSB1 and CR9501, elucidating for the first time how diverse germlines obtained from different subjects can develop convergent molecular mechanisms for recognition of the same PreF site of vulnerability. Importantly, RSB1-like nAbs were induced upon immunization with PreF in naturally-primed cattle. Together, this work reveals new details underlying the immunogenicity of site V and further supports PreF-based vaccine development efforts.

Respiratory syncytial virus (RSV) is a persistent, contagious seasonal pathogen and a serious public health threat. While infants are the most at-risk population, with infections potentially leading to bronchiolitis, adults, especially the elderly, are also burdened by RSV-induced respiratory infections. The only treatment currently available for RSV is passive immunization for high-risk infants. Thus, there is a critical need to develop a vaccine for the vast majority of the vulnerable population for which there is no preventative treatment. The RSV fusion protein in its prefusion form (PreF) is the target of the majority of naturally-induced neutralizing antibodies, and several clinical trials are currently evaluating PreF as a promising vaccine candidate. In this study, we solved the X-ray structure of PreF bound to the Fab fragment of a human neutralizing antibody. The structure reveals plasticity of the epitope, as well as a unique molecular signature for antibodies elicited towards this region of PreF. We also find that similar antibodies are induced upon immunization of naturally-primed cattle with a PreF vaccine antigen, suggesting that this epitope is highly immunogenic. These results will help us better understand the human immune response to RSV infection and vaccination, and guide future vaccine-design efforts.

Respiratory Syncytial Virus F Subunit Vaccine With AS02 Adjuvant Elicits Balanced, Robust Humoral and Cellular Immunity in BALB/c Mice

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory illness, particularly in infants, the elderly, and immunocompromised adults. There is no licensed commercial vaccine against RSV. Importantly, formalin-inactivated RSV vaccines mediate enhanced respiratory disease. RSV fusion (F) protein with pre-fusion conformation is a promising candidate subunit vaccine. However, some problems remain to be solved, such as low immunogenicity and humoral immunity bias. Adjuvants can effectively enhance and adjust vaccine immune responses. In this study, we formulated pre-fusion RSV-F protein with the adjuvants, Alhydrogel, MF59, AS03, AS02, and glycol chitosan (GCS). We then conducted head-to-head comparisons of vaccine-induced immune responses in BALB/c mice. All adjuvanted vaccines enhanced antigen-specific and neutralizing antibody titers and viral clearance and gave an order of adjuvant activity: AS02 > AS03, MF59 > GCS, and Alhydrogel. Among them, AS02 elicited the highest antibody expression, which persisted until week 18. Moreover, AS02 significantly enhanced Th1 type immune response in immunized mice. Mice in the AS02 group also showed faster recovery from viral attacks in challenge tests. Further transcriptome analysis revealed that AS02 regulates immune balance by activating TLR-4 and promotes Th1-type immune responses. These results suggest that AS02 may be an excellent candidate adjuvant for RSV-F subunit vaccines. This study also provides valuable information regarding the effect of other adjuvants on immune responses of RSV-F subunit vaccines.

A gammaherpesvirus licenses CD8 T cells to protect the host from pneumovirus-induced immunopathologies

Human respiratory syncytial virus (RSV) is a pneumovirus that causes severe infections in infants worldwide. Despite intensive research, safe and effective vaccines against RSV have remained elusive. The main reason is that RSV infection of children previously immunized with formalin-inactivated-RSV vaccines has been associated with exacerbated pathology, a phenomenon called RSV vaccine-enhanced respiratory disease. In parallel, despite the high RSV prevalence, only a minor proportion of children develop severe diseases. Interestingly, variation in the immune responses against RSV or following RSV vaccination could be linked with differences of exposure to microbes during childhood. Gammaherpesviruses (γHVs), such as the Epstein-Barr virus, are persistent viruses that deeply influence the immune system of their host and could therefore affect the development of pneumovirus-induced immunopathologies for the long term. Here, we showed that a previous ɣHV infection protects against both pneumovirus vaccine-enhanced disease and pneumovirus primary infection and that CD8 T cells are essential for this protection. These observations shed a new light on the understanding of pneumovirus-induced diseases and open new perspectives for the development of vaccine strategies.

CD4+ T Cells Drive Lung Disease Enhancement Induced by Immunization with Suboptimal Doses of Respiratory Syncytial Virus Fusion Protein in the Mouse Model

Respiratory syncytial virus (RSV) infection of seronegative children previously immunized with formalin-inactivated (FI) RSV has been associated with serious enhanced respiratory disease (ERD). The phenomenon was reproduced in the cotton rat and the mouse, and both preclinical models have been routinely used to evaluate the safety of new RSV vaccine candidates. More recently, we demonstrated that immunizations with suboptimal doses of the RSV fusion (F) antigen, in its post- or prefusion conformation, and in the presence of a Th1-biasing adjuvant, unexpectedly led to ERD in the cotton rat model. To assess if those observations are specific to the cotton rat and to elucidate the mechanism by which vaccination with low antigen doses can drive ERD post-RSV challenge, we evaluated RSV post-F antigen dose de-escalation in BALB/c mice in the presence of a Th1-biasing adjuvant. While decreasing antigen doses, we observed an increase in lung inflammation associated with an upregulation of proinflammatory cytokines. The amplitude of the lung histopathology was comparable to that of FI-RSV-induced ERD, confirming the observations made in the cotton rat. Importantly, depletion of CD4+ T cells prior to viral challenge completely abrogated ERD, preventing proinflammatory cytokine upregulation and the infiltration of T cells, neutrophils, eosinophils, and macrophages into the lung. Overall, low-antigen-dose-induced ERD resembles FI-RSV-induced ERD, except that the former appears in the absence of detectable levels of viral replication and in the context of a Th1-biased immune response. Taken together, our observations reinforce the recent concept that vaccines developed for RSV-naïve individuals should be systematically tested under suboptimal dosing conditions.IMPORTANCE RSV poses a significant health care burden and is the leading cause of serious lower-respiratory-tract infections in young children. A formalin-inactivated RSV vaccine developed in the 1960s not only showed a complete lack of efficacy against RSV infection but also induced severe lung disease enhancement in vaccinated children. Since then, establishing safety in preclinical models has been one of the major challenges to RSV vaccine development. We recently observed in the cotton rat model that suboptimal immunizations with RSV fusion protein could induce lung disease enhancement. In the present study, we extended suboptimal dosing evaluation to the mouse model. We confirmed the induction of lung disease enhancement by vaccinations with low antigen doses and dissected the associated immune mechanisms. Our results stress the need to evaluate suboptimal dosing for any new RSV vaccine candidate developed for seronegative infants.

Immunization with Low Doses of Recombinant Postfusion or Prefusion Respiratory Syncytial Virus F Primes for Vaccine-Enhanced Disease in the Cotton Rat Model Independently of the Presence of a Th1-Biasing (GLA-SE) or Th2-Biasing (Alum) Adjuvant

Respiratory syncytial virus (RSV) infection of children previously immunized with a nonlive, formalin-inactivated (FI)-RSV vaccine has been associated with serious enhanced respiratory disease (ERD). Consequently, detailed studies of potential ERD are a critical step in the development of nonlive RSV vaccines targeting RSV-naive children and infants. The fusion glycoprotein (F) of RSV in either its postfusion (post-F) or prefusion (pre-F) conformation is a target for neutralizing antibodies and therefore an attractive antigen candidate for a pediatric RSV subunit vaccine. Here, we report the evaluation of RSV post-F and pre-F in combination with glucopyranosyl lipid A (GLA) integrated into stable emulsion (SE) (GLA-SE) and alum adjuvants in the cotton rat model. Immunization with optimal doses of RSV F antigens in the presence of GLA-SE induced high titers of virus-neutralizing antibodies and conferred complete lung protection from virus challenge, with no ERD signs in the form of alveolitis. To mimic a waning immune response, and to assess priming for ERD under suboptimal conditions, an antigen dose de-escalation study was performed in the presence of either GLA-SE or alum. At low RSV F doses, alveolitis-associated histopathology was unexpectedly observed with either adjuvant at levels comparable to FI-RSV-immunized controls. This occurred despite neutralizing-antibody titers above the minimum levels required for protection and with no/low virus replication in the lungs. These results emphasize the need to investigate a pediatric RSV vaccine candidate carefully for priming of ERD over a wide dose range, even in the presence of strong neutralizing activity, Th1 bias-inducing adjuvant, and protection from virus replication in the lower respiratory tract.IMPORTANCE RSV disease is of great importance worldwide, with the highest burden of serious disease occurring upon primary infection in infants and children. FI-RSV-induced enhanced disease, observed in the 1960s, presented a major and ongoing obstacle for the development of nonlive RSV vaccine candidates. The findings presented here underscore the need to evaluate a nonlive RSV vaccine candidate during preclinical development over a wide dose range in the cotton rat RSV enhanced-disease model, as suboptimal dosing of several RSV F subunit vaccine candidates led to the priming for ERD. These observations are relevant to the validity of the cotton rat model itself and to safe development of nonlive RSV vaccines for seronegative infants and children.

Intranasal treatment with a novel immunomodulator mediates innate immune protection against lethal pneumonia virus of mice

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in infants and young children. There are no licensed RSV vaccines available, and the few treatment options for high-risk individuals are either extremely costly or cause severe side effects and toxicity. Immunomodulation mediated by a novel formulation consisting of the toll-like receptor 3 agonist poly(I:C), an innate defense regulator peptide and a polyphosphazene (P-I-P) was evaluated in the context of lethal infection with pneumonia virus of mice (PVM). Intranasal delivery of a single dose of P-I-P protected adult mice against PVM when given 24 h prior to challenge. These animals experienced minimal weight loss, no clinical disease, 100% survival, and reduced lung pathology. Similar clinical outcomes were observed in mice treated up to 3 days prior to infection. P-I-P pre-treatment induced early mRNA and protein expression of key chemokine and cytokine genes, reduced the recruitment of neutrophils and eosinophils, decreased virus titers in the lungs, and modulated the delayed exacerbated nature of PVM disease without any short-term side effects. On day 14 post-infection, P-I-P-treated mice were confirmed to be PVM-free. These results demonstrate the capacity of this formulation to prevent PVM and possibly other viral respiratory infections.

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P-I-P pre-treatment, consisting of poly(I:C), IDR peptide and PCEP, was tested in the context of PVM infection in mice.

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P-I-P confers complete protection against lethal PVM infection by reducing clinical signs and immunopathology.

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P-I-P minimizes viral titers in the lungs reduces the influx of neutrophils and eosinophils into the tissue.

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P-I-P induces early upregulation of genes involved in host defense without any observable adverse effects.

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Survivor mice were PVM negative, suggesting that P-I-P mediates the successfully clearance of the virus in vivo.

Aging of the immune system: Focus on inflammation and vaccination

Major advances in preventing, delaying, or curing individual pathologies are responsible for an increasingly long life span in the developed parts of our planet, and indeed reaching eight to nine decades of life is nowadays extremely frequent. However, medical and sanitary advances have not prevented or delayed the underlying cause of the disparate pathologies occurring in the elderly: aging itself. The identification of the basis of the aging processes that drives the multiple pathologies and loss of function typical of older individuals is a major challenge in current aging research. Among the possible causes, an impairment of the immune system plays a major role, and indeed numerous studies have described immunological changes which occur with age. Far from the intention of being exhaustive, this review will focus on recent advances and views on the role that modifications of cell signalling and remodelling of the immune response play during human aging and longevity, paying particular attention to phenomena which are linked to the so called inflammaging process, such as dysregulation of innate immunity, altered T-cell or B-cell maturation and differentiation, as well as to the implications of immune aging for vaccination strategies in the elderly.

Antibody response to respiratory syncytial virus infection in children <18 months old

The development of a safe and effective respiratory syncytial virus (RSV) vaccine might be facilitated by knowledge of the natural immune response to this virus. The aims of this study were to evaluate the neutralizing antibody response of a cohort of healthy children <18 months old to RSV infection. During the RSV season, 89 healthy children <18 months old were enrolled and followed up weekly for 12 weeks. At each visit, a nasopharyngeal swab was obtained for RSV detection by real-time polymerase chain reaction (PCR). During the study period, 2 blood samples were drawn and they were used to determine RSV geometric mean neutralizing antibody titres (GMT) against RSV. A total of 35 (39.3%) children had RSV detected during the study period. Among RSV-positive patients, children ≥7 months showed a significantly higher increase in antibody response (p<0.001). A significantly higher number of patients with a ≥4 -fold increase in GMT were ≥7 months old (p = 0.02) and presented lower respiratory tract infections (LRTIs) during the study period (p = 0.01). Viral shedding was longer among children aged ≥7 months (p = 0.06), those with viral load ≥10(6) copies/mL (p = 0.03), and those with LRTIs during the study period (p = 0.03), but it was not associated with the immune response (p = 0.41). In conclusion, natural RSV infection seems to evoke a low immune response in younger children. To be effective in this infant population, which is at highest risk of developing severe LRTIs, vaccines must be able to induce in the first months of life a stronger immune response than that produced by the natural infection.

Respiratory nanoparticle-based vaccines and challenges associated with animal models and translation

Vaccine development has had a huge impact on human health. However, there is a significant need to develop efficacious vaccines for several existing as well as emerging respiratory infectious diseases. Several challenges need to be overcome to develop efficacious vaccines with translational potential. This review focuses on two aspects to overcome some barriers - 1) the development of nanoparticle-based vaccines, and 2) the choice of suitable animal models for respiratory infectious diseases that will allow for translation. Nanoparticle-based vaccines, including subunit vaccines involving synthetic and/or natural polymeric adjuvants and carriers, as well as those based on virus-like particles offer several key advantages to help overcome the barriers to effective vaccine development. These include the ability to deliver combinations of antigens, target the vaccine formulation to specific immune cells, enable cross-protection against divergent strains, act as adjuvants or immunomodulators, allow for sustained release of antigen, enable single dose delivery, and potentially obviate the cold chain. While mouse models have provided several important insights into the mechanisms of infectious diseases, they are often a limiting step in translation of new vaccines to the clinic. An overview of different animal models involved in vaccine research for respiratory infections, with advantages and disadvantages of each model, is discussed. Taken together, advances in nanotechnology, combined with the right animal models for evaluating vaccine efficacy, has the potential to revolutionize vaccine development for respiratory infections.

Sendai virus as a backbone for vaccines against RSV and other human paramyxoviruses

Human paramyxoviruses are the etiological agents for life-threatening respiratory virus infections of infants and young children. These viruses, including respiratory syncytial virus (RSV), the human parainfluenza viruses (hPIV1-4) and human metapneumovirus (hMPV), are responsible for millions of serious lower respiratory tract infections each year worldwide. There are currently no standard treatments and no licensed vaccines for any of these pathogens. Here we review research with which Sendai virus, a mouse parainfluenza virus type 1, is being advanced as a Jennerian vaccine for hPIV1 and as a backbone for RSV, hMPV and other hPIV vaccines for children.

WHO consultation on Respiratory Syncytial Virus Vaccine Development Report from a World Health Organization Meeting held on 23-24 March 2015

Respiratory syncytial virus (RSV) is a globally prevalent cause of lower respiratory infection in neonates and infants. Despite its disease burden, a safe and effective RSV vaccine has remained elusive. In recent years, improved understanding of RSV biology and innovations in immunogen design has resulted in the advancement of multiple vaccine candidates into the clinical development pipeline. Given the growing number of vaccines in clinical trials, the rapid pace at which they are being tested, and the likelihood that an RSV vaccine will reach the commercial market in the next 5–10 years, consensus and guidance on clinical development pathways and licensure routes are needed now, before large-scale efficacy trials commence. In pursuit of this aim, the World Health Organization convened the first RSV vaccine consultation in 15 years on the 23rd and 24th of March, 2015 in Geneva, Switzerland. The meeting’s primary objective was to provide guidance on clinical endpoints and development pathways for vaccine trials with a focus on considerations of low- and middle-income countries. Meeting participants reached consensus on candidate case definitions for RSV disease, considerations for clinical efficacy endpoints, and the clinical development pathway for active and passive immunization trials in maternal and pediatric populations. The strategic focus of this meeting was on the development of high quality, safe and efficacious RSV preventive interventions for global use and included: (1) maternal/passive immunization to prevent RSV disease in infants less than 6 months; (2) pediatric immunization to prevent RSV disease in infants and young children once protection afforded by maternal immunization wanes.

Analysis of Human RSV Immunity at the Molecular Level: Learning from the Past and Present

Human RSV is one of the most prevalent viral pathogens of early childhood for which no vaccine is available. Herein we provide an analysis of RSV epitope data to examine its application to vaccine design and development. Our objective was to provide an overview of antigenic coverage, identify critical antibody and T cell determinants, and then analyze the cumulative RSV epitope data from the standpoint of functional responses using a combinational approach to characterize antigenic structure and epitope location. A review of the cumulative data revealed, not surprisingly, that the vast majority of epitopes have been defined for the two major surface antigens, F and G. Antibody and T cell determinants have been reported from multiple hosts, including those from human subjects following natural infection, however human data represent a minority of the data. A structural analysis of the major surface antigen, F, showed that the majority of epitopes defined for functional antibodies (neutralizing and/or protective) were either shown to bind pre-F or to be accessible in both pre- and post-F forms. This finding may have has implications for on-going vaccine design and development. These interpretations are in agreement with previous work and can be applied in the larger context of functional epitopes on the F protein. It is our hope that this work will provide the basis for further RSV-specific epitope discovery and investigation into the nature of antigen conformation in immunogenicity.

New challenges in modern vaccinology

Vaccination has been a major advance for health care, allowing eradication or reduction of incidence and mortality of various infectious diseases. However, there are major pathogens, such as Human Immunodeficiency Virus (HIV) or the causative agent of malaria, for which classical vaccination approaches have failed, therefore requiring new vaccination strategies. The development of new vaccine strategies relies on the ability to identify the challenges posed by these pathogens. Understanding the pathogenesis and correlates of protection for these diseases, our ability to accurately direct immune responses and to vaccinate specific populations are such examples of these roadblocks. In this respect, the use of a robust, cost-effective and predictive animal model that recapitulates features of both human infection and vaccination is currently a much-needed tool. We discuss here the major limitations faced by modern vaccinology and notably, the development of humanized mice for assessing the immune system, along with their potential as vaccine models.

Vaccines for the elderly

The aging of the human population is posing serious challenges to research and to public health authorities in order to prevent diseases that more frequently affect the elderly, a portion of the population that will increase more and more in the coming years. While some vaccines exist and are used in the elderly to effectively fight against some infections (e.g. influenza, pneumococci, varicella-zoster virus, diphtheria, and tetanus), still a lot of work remains to be done to better adapt these vaccines and to develop new ones for this age group. The prevention of infectious diseases affecting the elderly can be successful only through a holistic approach. This approach will aim at the following: (1) a deeper understanding of the mechanisms leading to the senescence of the immune system, (2) a better and broader use of vaccines recommended for the elderly, (3) the use of vaccines currently considered only for other age groups and (4) actively priming the population when they are immunological competent, before the physiological waning of immune responsiveness may affect the beneficial effects of vaccination.

Immunity to RSV in Early-Life

Respiratory Syncytial Virus (RSV) is the commonest cause of severe respiratory infection in infants, leading to over 3 million hospitalizations and around 66,000 deaths worldwide each year. RSV bronchiolitis predominantly strikes apparently healthy infants, with age as the principal risk factor for severe disease. The differences in the immune response to RSV in the very young are likely to be key to determining the clinical outcome of this common infection. Remarkable age-related differences in innate cytokine responses follow recognition of RSV by numerous pattern recognition receptors, and the importance of this early response is supported by polymorphisms in many early innate genes, which associate with bronchiolitis. In the absence of strong, Th1 polarizing signals, infants develop T cell responses that can be biased away from protective Th1 and cytotoxic T cell immunity toward dysregulated, Th2 and Th17 polarization. This may contribute not only to the initial inflammation in bronchiolitis, but also to the long-term increased risk of developing wheeze and asthma later in life. An early-life vaccine for RSV will need to overcome the difficulties of generating a protective response in infants, and the proven risks associated with generating an inappropriate response. Infantile T follicular helper and B cell responses are immature, but maternal antibodies can afford some protection. Thus, maternal vaccination is a promising alternative approach. However, even in adults adaptive immunity following natural infection is poorly protective, allowing re-infection even with the same strain of RSV. This gives us few clues as to how effective vaccination could be achieved. Challenges remain in understanding how respiratory immunity matures with age, and the external factors influencing its development. Determining why some infants develop bronchiolitis should lead to new therapies to lessen the clinical impact of RSV and aid the rational design of protective vaccines.

Maternal immunization with chimpanzee adenovirus expressing RSV fusion protein protects against neonatal RSV pulmonary infection

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease with high morbidity and mortality in young infants and children. Despite numerous efforts, a licensed vaccine against RSV remains elusive. Since young infants form the primary target group of RSV disease, maternal immunization to boost the protection in neonates is an attractive strategy. In this study we tested the efficacy of maternal immunization with a chimpanzee adenovirus expressing codon-optimized RSV fusion protein (AdC7-Fsyn) to protect infants against RSV infection. Single intranasal immunization of mice by AdC7-Fsyn induced robust anti-RSV systemic and mucosal immunity that protected against RSV without causing vaccine-enhanced RSV disease. RSV humoral immunity was transferred to pups born to immunized mothers that provided protection against RSV. Immunization with AdC7-Fsyn was effective even in the presence of Ad5 preimmunity. The maternally derived immunity was durable with the half-life of 14.63 days that reduced the viral replication up to 15 weeks of age. Notably, the passively immunized mice could be actively re-immunized with AdC7-Fsyn to boost and extend the protection. This substantiates maternal immunization with an AdC7-based vaccine expressing RSV F as feasible approach to protect against RSV early in life.

Rapid replacement of human respiratory syncytial virus A with the ON1 genotype having 72 nucleotide duplication in G gene

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We investigated the prevalence of HRSV during 2008–2013.

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Novel HRSV-A ON1 genotype was emerged in August 2011.

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After 1 year of emergence in 2012–2013, 94.6% was replaced with novel ON1 genotype.

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Evolutionary dynamics also drastically increased in 2011.

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The result of epitope prediction shows the possibilities of antigenic variation.

Human respiratory syncytial virus (HRSV) is the main cause of severe respiratory illness in young children and elderly people. We investigated the genetic characteristics of the circulating HRSV subgroup A (HRSV-A) to determine the distribution of genotype ON1, which has a 72-nucleotide duplication in attachment G gene. We obtained 456 HRSV-A positive samples between October 2008 and February 2013, which were subjected to sequence analysis. The first ON1 genotype was discovered in August 2011 and 273 samples were identified as ON1 up to February 2013. The prevalence of the ON1 genotype increased rapidly from 17.4% in 2011–2012 to 94.6% in 2012–2013. The mean evolutionary rate of G protein was calculated as 3.275 × 10⁻³ nucleotide substitution/site/year and several positively selected sites for amino acid substitutions were located in the predicted epitope region. This basic and important information may facilitate a better understanding of HRSV epidemiology and evolution.

Sendai virus-based RSV vaccine protects against RSV challenge in an in vivo maternal antibody model

Respiratory syncytial virus (RSV) is the cause of significant morbidity and mortality among infants, and despite decades of research there remains no licensed vaccine. SeVRSV is a Sendai virus (SeV)-based live intranasal vaccine that expresses the full length RSV fusion (F) gene. SeV is the murine counterpart of human parainfluenza virus type 1. Given that the target population of SeVRSV is young infants, we questioned whether maternal antibodies typical of this age group would inhibit SeVRSV vaccine efficacy. After measuring SeV- and RSV-specific serum neutralizing antibody titers in human infants, we matched these defined titers in cotton rats by the passive transfer of polyclonal or monoclonal antibody products. Animals were then vaccinated with SeVRSV followed by a 3 month rest period to allow passively transferred antibodies to wane. Animals were finally challenged with RSV to measure the de novo vaccine-induced immune responses. Despite the presence of passively-transferred serum neutralizing antibodies at the time of vaccination, SeVRSV induced immune responses that were protective against RSV challenge. The data encourage advancement of SeVRSV as a candidate vaccine for the protection of children from morbidity and mortality caused by RSV.

Unmet needs in respiratory diseases : "You can't know where you are going until you know where you have been"--Anonymous

The care of patients with respiratory diseases has improved vastly in the past 50 years. In spite of that, there are still massive challenges that have not been resolved. Although the incidence of tuberculosis has decreased in the developed world, it is still a significant public health problem in the rest of the world. There are still over 2 million deaths annually from tuberculosis, with most of these occurring in the developing world. Even with the development of new pharmaceuticals to treat tuberculosis, there is no indication that the disease will be eradicated. Respiratory syncytial virus, severe acute respiratory syndrome, and pertussis are other respiratory infectious diseases with special problems of their own, from vaccine development to vaccine coverage. Asthma, one of the most common chronic diseases in children, still accounts for significant mortality and morbidity, as well as high health care costs worldwide. Even in developed countries such as the USA, there are over 4,000 deaths per year. Severe asthma presents a special problem, but the question is whether there can be one treatment pathway for all patients with severe asthma. Severe asthma is a heterogeneous disease with many phenotypes and endotypes. The gene for cystic fibrosis was discovered over 24 years ago. The promise of gene therapy as a cure for the disease has fizzled out, and while new antimicrobials and other pharmaceuticals promise improved longevity and better quality of life, the average life span of a patient with cystic fibrosis is still at about 35 years. What are the prospects for gene therapy in the twenty-first century? Autoimmune diseases of the lung pose a different set of challenges, including the development of biomarkers to diagnose and monitor the disease and biological modulators to treat the disease.

Epidemiology and etiology of childhood pneumonia in 2010: estimates of incidence, severe morbidity, mortality, underlying risk factors and causative pathogens for 192 countries

Background

The recent series of reviews conducted within the Global Action Plan for Pneumonia and Diarrhoea (GAPPD) addressed epidemiology of the two deadly diseases at the global and regional level; it also estimated the effectiveness of interventions, barriers to achieving high coverage and the main implications for health policy. The aim of this paper is to provide the estimates of childhood pneumonia at the country level. This should allow national policy–makers and stakeholders to implement proposed policies in the World Health Organization (WHO) and UNICEF member countries.

Methods

We conducted a series of systematic reviews to update previous estimates of the global, regional and national burden of childhood pneumonia incidence, severe morbidity, mortality, risk factors and specific contributions of the most common pathogens: Streptococcus pneumoniae (SP), Haemophilus influenzae type B (Hib), respiratory syncytial virus (RSV) and influenza virus (flu). We distributed the global and regional–level estimates of the number of cases, severe cases and deaths from childhood pneumonia in 2010–2011 by specific countries using an epidemiological model. The model was based on the prevalence of the five main risk factors for childhood pneumonia within countries (malnutrition, low birth weight, non–exclusive breastfeeding in the first four months, solid fuel use and crowding) and risk effect sizes estimated using meta–analysis.

Findings

The incidence of community–acquired childhood pneumonia in low– and middle–income countries (LMIC) in the year 2010, using World Health Organization's definition, was about 0.22 (interquartile range (IQR) 0.11–0.51) episodes per child–year (e/cy), with 11.5% (IQR 8.0–33.0%) of cases progressing to severe episodes. This is a reduction of nearly 25% over the past decade, which is consistent with observed reductions in the prevalence of risk factors for pneumonia throughout LMIC. At the level of pneumonia incidence, RSV is the most common pathogen, present in about 29% of all episodes, followed by influenza (17%). The contribution of different pathogens varies by pneumonia severity strata, with viral etiologies becoming relatively less important and most deaths in 2010 caused by the main bacterial agents – SP (33%) and Hib (16%), accounting for vaccine use against these two pathogens.

Conclusions

In comparison to 2000, the primary epidemiological evidence contributing to the models of childhood pneumonia burden has improved only slightly; all estimates have wide uncertainty bounds. Still, there is evidence of a decreasing trend for all measures of the burden over the period 2000–2010. The estimates of pneumonia incidence, severe morbidity, mortality and etiology, although each derived from different and independent data, are internally consistent – lending credibility to the new set of estimates. Pneumonia continues to be the leading cause of both morbidity and mortality for young children beyond the neonatal period and requires ongoing strategies and progress to reduce the burden further.