A multifaceted approach to RSV vaccination

Respiratory Syncytial Virus Vaccines: A Review of the Candidates and the Approved Vaccines

Respiratory syncytial virus (RSV) is responsible for a significant proportion of global morbidity and mortality affecting young children and older adults. In the aftermath of formalin-inactivated RSV vaccine development, the effort to develop an immunizing agent was carefully guided by epidemiologic and pathophysiological evidence of the virus, including various vaccine technologies. The pipeline of RSV vaccine development includes messenger ribonucleic acid (mRNA), live-attenuated (LAV), subunit, and recombinant vector-based vaccine candidates targeting different virus proteins. The availability of vaccine candidates of various technologies enables adjustment to the individualized needs of each vulnerable age group. Arexvy® (GSK), followed by Abrysvo® (Pfizer), is the first vaccine available for market use as an immunizing agent to prevent lower respiratory tract disease in older adults. Abrysvo is additionally indicated for the passive immunization of infants by maternal administration during pregnancy. This review presents the RSV vaccine pipeline, analyzing the results of clinical trials. The key features of each vaccine technology are also mentioned. Currently, 24 vaccines are in the clinical stage of development, including the 2 licensed vaccines. Research in the field of RSV vaccination, including the pharmacovigilance methods of already approved vaccines, promotes the achievement of successful prevention.

Responding to Higher-Than-Expected Infant Mortality Rates from Respiratory Syncytial Virus (RSV): Improving Treatment and Reporting Strategies

Respiratory syncytial virus (RSV) has a major role in respiratory infections in young infants around the world. However, substantial progress has been made in recent years in the field of RSV. A wide variety of observational studies and clinical trials published in the past decade provide a thorough idea of the health and economic burden of RSV disease in the developing world. In this review, we discuss the impact of RSV burden of disease, major gaps in disease estimations, and challenges in generating new therapeutic options and an immune response against the virus, and briefly describe next generation technologies that are being evaluated.

Low circulation of respiratory syncytial and influenza viruses during autumn-winter 2021 in the industrial workplace and long-term healthcare facilities in Athens, Greece

The emergence of SARS-CoV-2 has pinpointed the importance of non-pharmaceutical interventions (NPIs), which have been traditionally used for the prevention of the spread of respiratory viruses among individuals. The aim of our study was to capture the level of circulation of respiratory syncytial and influenza viruses during a period of medium severity NPIs due to SARS-CoV-2 pandemics in Greece. A total of 2,225 nasopharyngeal samples were received during the year 2021 as a part of the routine diagnostic service and were divided into two study groups: (a) January to September 2021 and (b) October to the end of December 2021. The latter is the time of the year when there is a peak of infections from most respiratory viruses, and thus, most of the samples were tested in that period. The samples were taken from three different sites, i.e., (a) industrial workers in a factory, (b) elderly homecare facilities, and c) people who actively asked to be tested for SARS-CoV-2. All the samples were tested simultaneously for SARS-CoV2, RSV, and influenza virus. A total of 2,110 samples were negative for either of the three viruses, 106 were SARS-CoV-2-positive, and 9 were RSV-positive from which 7 were found in the workers' group. None of the samples was found to be positive for the influenza virus, and no sample had co-infection. Our study shows the low-level circulation of RSV and influenza viruses during autumn-winter 2021 and will provide a reference for future studies of RSV and influenza in Greece.

Early Changes in Interferon Gene Expression and Antibody Responses Following Influenza Vaccination in Pregnant Women

BACKGROUND

Influenza immunization during pregnancy provides protection to the mother and the infant. Studies in adults and children with inactivated influenza vaccine have identified changes in immune gene expression that were correlated with antibody responses. The current study was performed to define baseline blood transcriptional profiles and changes induced by inactivated influenza vaccine in pregnant women and to identify correlates with antibody responses.

METHODS

Pregnant women were immunized with inactivated influenza vaccine during the 2013-2014 and 2014-2015 seasons. Blood samples were collected on day 0 (before vaccination) and on days 1 and 7 after vaccination for transcriptional profile analyses, and on days 0 and 30, along with delivery and cord blood samples, to measure antibody titers.

RESULTS

Transcriptional analysis demonstrated overexpression of interferon-stimulated genes (ISGs) on day 1 and of plasma cell genes on day 7. Prevaccination ISG expression and ISGs overexpressed on day 1 were significantly correlated with increased H3N2, B Yamagata, and B Victoria antibody titers. Plasma cell gene expression on day 7 was correlated with increased B Yamagata and B Victoria antibody titers. Compared with women who were vaccinated during the previous influenza season, those who were not showed more frequent significant correlations between ISGs and antibody titers.

CONCLUSIONS

Influenza vaccination in pregnant women resulted in enhanced expression of ISGs and plasma cell genes correlated with antibody responses. Brief summary: This study identified gene expression profiles of interferon-stimulated genes and plasma cells before vaccination and early after vaccination that were correlated with antibody responses in pregnant women vaccinated for influenza.

Risk of Transmission and Viral Shedding From the Time of Infection for Respiratory Syncytial Virus in Households

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection worldwide, but reports of temporal changes in the risk of transmission among close contacts has been scarce. This study aimed to examine an association between the viral load trajectory and transmission risk to develop a better control strategy for the disease spread. We conducted a household-based prospective cohort study in Biliran Province, the Philippines, and enrolled 451 participants to observe the development of acute respiratory infection. Including the cases found at the health-care facility, we analyzed the data of viral loads with symptom records obtained from 172 followed participants who had household member positive for RSV with a rapid test during an RSV outbreak in 2018-2019. We developed a model estimating a temporal change in the viral shedding from the infection and evaluated transmission dynamics. We found that most transmission events occurred within approximately 7 days of the household exposure, including potential presymptomatic transmissions. The inferred risk of infection among those younger than 5 years was 3.5 times higher than that of those older than 5 years. This finding suggested that the initial week after the household exposure is particularly important for preventing RSV spread.

Transplacental Antibody Transfer of Respiratory Syncytial Virus Specific IgG in Non-Human Primate Mother-Infant Pairs

One approach to protect new-borns against respiratory syncytial virus (RSV) is to vaccinate pregnant women in the last trimester of pregnancy. The boosting of circulating antibodies which can be transferred to the foetus would offer immune protection against the virus and ultimately the disease. Since non-human primates (NHPs) have similar reproductive anatomy, physiology, and antibody architecture and kinetics to humans, we utilized this preclinical species to evaluate maternal immunization (MI) using an RSV F subunit vaccine. Three species of NHPs known for their ability to be infected with human RSV in experimental challenge studies were tested for RSV-specific antibodies. African green monkeys had the highest overall antibody levels of the old-world monkeys evaluated and they gave birth to offspring with anti-RSV titers that were proportional to their mother. These higher overall antibody levels are associated with greater durability found in their offspring. Immunization of RSV seropositive AGMs during late pregnancy boosts RSV titers, which consequentially results in significantly higher titers in the vaccinated new-borns compared to the new-borns of unvaccinated mothers. These findings, accomplished in small treatment group sizes, demonstrate a model that provides an efficient, resource sparing and translatable preclinical in vivo system for evaluating vaccine candidates for maternal immunization.

A Recombinant BCG Vaccine Is Safe and Immunogenic in Neonatal Calves and Reduces the Clinical Disease Caused by the Respiratory Syncytial Virus

The human respiratory syncytial virus (hRSV) constitutes a major health burden, causing millions of hospitalizations in children under five years old worldwide due to acute lower respiratory tract infections. Despite decades of research, licensed vaccines to prevent hRSV are not available. Development of vaccines against hRSV targeting young infants requires ruling out potential vaccine-enhanced disease presentations. To achieve this goal, vaccine testing in proper animal models is essential. A recombinant BCG vaccine that expresses the Nucleoprotein of hRSV (rBCG-N-hRSV) protects mice against hRSV infection, eliciting humoral and cellular immune protection. Further, this vaccine was shown to be safe and immunogenic in human adult volunteers. Here, we evaluated the safety, immunogenicity, and protective efficacy of the rBCG-N-hRSV vaccine in a neonatal bovine RSV calf infection model. Newborn, colostrum-replete Holstein calves were either vaccinated with rBCG-N-hRSV, WT-BCG, or left unvaccinated, and then inoculated via aerosol challenge with bRSV strain 375. Vaccination with rBCG-N-hRSV was safe and well-tolerated, with no systemic adverse effects. There was no evidence of vaccine-enhanced disease following bRSV challenge of rBCG-N-hRSV vaccinated animals, suggesting that the vaccine is safe for use in neonates. Vaccination increased virus-specific IgA and virus-neutralization activity in nasal fluid and increased the proliferation of virus- and BCG-specific CD4+ and CD8+ T cells in PBMCs and lymph nodes at 7dpi. Furthermore, rBCG-N-hRSV vaccinated calves developed reduced clinical disease as compared to unvaccinated control calves, although neither pathology nor viral burden were significantly reduced in the lungs. These results suggest that the rBCG-N-hRSV vaccine is safe in neonatal calves and induces protective humoral and cellular immunity against this respiratory virus. These data from a newborn animal model provide further support to the notion that this vaccine approach could be considered as a candidate for infant immunization against RSV.

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

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

The Future of Respiratory Syncytial Virus Disease Prevention and Treatment

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, young children, and older or immunocompromised adults. Although aerosolized ribavirin was licensed for RSV treatment on the basis of data demonstrating a reduced need for supplemental oxygen, ribavirin use is limited because of issues with efficacy, safety, and cost. Currently, the treatment of RSV is primarily supportive. New antiviral treatments for RSV are in the early stages of development, but it will be years until any of these may be licensed by the US Food and Drug Administration (FDA). Palivizumab, an RSV monoclonal antibody [immunoprophylaxis (IP)], has demonstrated effectiveness in disease prevention and is the only licensed IP for RSV disease in specific high-risk pediatric populations. Although its efficacy is well established, some challenges that may interfere with its clinical use include cost, need for monthly injections, and changing policy for use by the American Academy of Pediatrics (AAP). Preventing RSV disease would be possible through RSV vaccine development (e.g., live-attenuated, vector-based subunit, or particle-based). Alternatively, new long-acting monoclonal antibodies have demonstrated promising results in early clinical trials. Despite scientific advances, until new agents become available, palivizumab should continue to be used to reduce RSV disease burden in high-risk patients for whom it is indicated.

Mucosal Delivery of Recombinant Vesicular Stomatitis Virus Vectors Expressing Envelope Proteins of Respiratory Syncytial Virus Induces Protective Immunity in Cotton Rats

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract (LRT) infections, with increased severity in high-risk human populations, such as infants, the immunocompromised, and the elderly. Although the virus was identified more than 60 years ago, there is still no licensed vaccine available. Over the years, several vaccine delivery strategies have been evaluated. In this study, we developed two recombinant vesicular stomatitis virus (rVSV) vector-based vaccine candidates expressing the RSV-G (attachment) protein (rVSV-G) or F (fusion) protein (rVSV-F). All vectors were evaluated in the cotton rat animal model for their in vivo immunogenicity and protective efficacy against an RSV-A2 virus challenge. Intranasal (i.n.) delivery of rVSV-G and rVSV-F together completely protected the lower respiratory tract (lungs) at doses as low as 10³ PFU. In contrast, doses greater than 10⁶ PFU were required to protect the upper respiratory tract (URT) completely. Reimmunization of RSV-immune cotton rats was most effective with rVSV-F. In immunized animals, overall antibody responses were sufficient for protection, whereas CD4 and CD8 T cells were not necessary. A prime-boost immunization regimen increased both protection and neutralizing antibody titers. Overall, mucosally delivered rVSV-vector-based RSV vaccine candidates induce protective immunity and therefore represent a promising immunization regimen against RSV infection.IMPORTANCE Even after decades of intensive research efforts, a safe and efficacious RSV vaccine remains elusive. Expression of heterologous antigens from rVSV vectors has demonstrated several practical and safety advantages over other virus vector systems and live attenuated vaccines. In this study, we developed safe and efficacious vaccine candidates by expressing the two major immunogenic RSV surface proteins in rVSV vectors and delivering them mucosally in a prime-boost regimen. The main immune parameter responsible for protection was the antibody response. These vaccine candidates induced complete protection of both the upper and lower respiratory tracts.

The Protective Role of Maternal Immunization in Early Life

With birth, the newborn is transferred from a quasi-sterile environment to the outside world. At this time, the neonatal immune system is inexperienced and continuously subject to a process of development as it encounters different antigenic stimuli after birth. It is initially characterized by a bias toward T helper 2 phenotype, reduced T helper 1, and cytotoxic responses to microbial stimuli, low levels of memory, and effector T and B cells and a high production of suppressive T regulatory cells. The aim of this setting, during fetal life, is to maintain an anti-inflammatory state and immune-tolerance. Maternal antibodies are transferred during pregnancy through the placenta and, in the first weeks of life of the newborn, they represent a powerful tool for protection. Thus, optimization of vaccination in pregnancy represents an important strategy to reduce the burden of neonatal infections and sepsis. Beneficial effects of maternal immunization are universally recognized, although the optimal timing of vaccination in pregnancy remains to be defined. Interestingly, the dynamic exchange that takes place at the fetal-maternal interface allows the transfer not only of antibodies, but also of maternal antigen presenting cells, probably in order to stimulate the developing fetal immune system in a harmless way. There are still controversial effects related to maternal immunization including the so called "immunology blunting," i.e., a dampened antibody production following infant's vaccination in those infants who received placentally transferred maternal immunity. However, clinical relevance of this phenomenon is still not clear. This review will provide an overview of the evolution of the immune system in early life and discuss the benefits of maternal vaccination. Current maternal vaccination policies and their rationale will be summarized on the road to promising approaches to enhance immunity in the neonate.

The Importance of AGO 1 and 4 in Post-Transcriptional Gene Regulatory Function of tRF5-GluCTC, an Respiratory Syncytial Virus-Induced tRNA-Derived RNA Fragment

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants, the elderly, and immune-compromised patients. It is also a significant contributor to upper respiratory tract infection in the pediatric population. However, its disease mechanisms are still largely unknown. We have recently shown that a tRNA-derived RNA fragment (tRF) from the 5′-end of mature tRNA encoding GluCTC (tRF5-GluCTC), a recently discovered non-coding RNA, is functionally important for RSV replication and host gene regulation at the post-transcriptional level. However, how tRF5-GluCTC carries out the gene regulation is not fully known. In this study, we found that tRF5-GluCTC has impaired gene trans-silencing function in cells deficient of AGO1 or 4, while AGO2 and 3 seem not involved in tRF5-GluCTC-mediated gene regulation. By pulling down individual AGO protein, we discovered that tRF5-GluCTC is detectable only in the AGO4 complex, confirming the essential role of AGO4 in gene regulation and also suggesting that AGO1 contributes to the gene trans-silencing activity of tRF5-GluCTC in an atypical way. We also found that the P protein of RSV is associated with both AGO1 and 4 and AGO4 deficiency leads to reduced infectious viral particles. In summary, this study demonstrates the importance of AGO1 and 4 in mediating the gene trans-silencing function of tRF5-GluCTC.

Viral Etiology, Clinical Features and Antibiotic Use in Children <5 Years of Age in the Gambia Presenting With Influenza-like Illness

BACKGROUND

Knowledge regarding the prevalence, clinical features and etiology of pediatric influenza-like illness (ILI) remains limited in African settings. Furthermore, it is likely that many children presenting with ILI receive antibiotics unnecessarily. More data are required to develop antimicrobial stewardship practice and guide effective vaccine strategies. We undertook a 1-year prospective study of ILI in the Gambia.

METHODS

Children <5 years of age presenting with ILI from March 2018 to March 2019 were recruited. Clinical and antibiotic prescribing data were collected. Nasopharyngeal swabs were collected and analyzed for 12 respiratory viruses using a multiplex polymerase chain reaction.

RESULTS

From a total of 735 ILI episodes, 530 (72.1%) nasopharyngeal swabs were positive for ≥1 virus. Of these, 36.7% were positive for rhinovirus, 14.7% for respiratory syncytial virus, 8.4% for influenza and 7.2% for human metapneumovirus. Compared with children <6 months of age, influenza was more common in 6- to 23-month-old children [odd ratio (OR): 5.68; 95% confidence interval (CI): 1.72-18.76; P = 0.004]. Respiratory syncytial virus and human metapneumovirus were associated with low peripheral oxygen saturations (OR: 2.13; 95% CI: 1.23-3.69; P = 0.007; and OR: 2.44; 95% CI: 1.13-5.27; P = 0.023, respectively). Antibiotics were prescribed in 78.3% of all ILI cases.

CONCLUSIONS

A broad range of viruses are responsible for pediatric ILI in the Gambia. Refined treatment guidelines, improved diagnostic capacity and vaccines to prevent respiratory viruses will all play a role in reducing antimicrobial use for these cases.

Antigenic Fingerprinting of Respiratory Syncytial Virus (RSV)-A-Infected Hematopoietic Cell Transplant Recipients Reveals Importance of Mucosal Anti-RSV G Antibodies in Control of RSV Infection in Humans

BACKGROUND

Respiratory syncytial virus (RSV) infection causes significant morbidity in hematopoietic cell transplant (HCT) recipients. However, antibody responses that correlate with recovery from RSV disease are not fully understood.

METHODS

In this study, antibody repertoire in paired serum and nasal wash samples from acutely RSV-A-infected HCT recipients who recovered early (<14 days of RSV shedding) were compared with late-recovered patients (≥14 days of shedding) using gene fragment phage display libraries and surface plasmon resonance.

RESULTS

Anti-F serum responses were similar between these 2 groups for antibody repertoires, neutralization titers, anti-F binding antibodies (prefusion and postfusion proteins), antibody avidity, and binding to specific antigenic sites. In contrast, nasal washes from early-recovered individuals demonstrated higher binding to F peptide containing p27. While the serum RSV G antibody repertoires in the 2 groups were similar, the strongest difference between early-recovered and late-recovered patients was observed in the titers of nasal wash antibodies, especially binding to the central conserved domain. Most importantly, a significantly higher antibody affinity to RSV G was observed in nasal washes from early-recovered individuals compared with late-recovered HCT recipients.

CONCLUSIONS

These findings highlight the importance of mucosal antibodies in resolution of RSV-A infection in the upper respiratory tract.

β2-integrin LFA1 mediates airway damage following neutrophil transepithelial migration during respiratory syncytial virus infection

Respiratory syncytial virus (RSV) bronchiolitis is the most common cause of infant hospital admissions, but there is limited understanding of the mechanisms of disease, and no specific antiviral treatment. Using a novel in vitro primary transepithelial neutrophil migration model and innovative imaging methods, we show that RSV infection of nasal airway epithelium increased neutrophil transepithelial migration and adhesion to infected epithelial cells, which is associated with epithelial cell damage and reduced ciliary beat frequency, but also with a reduction in infectious viral load.Following migration, RSV infection results in greater neutrophil activation, degranulation and release of neutrophil elastase into the airway surface media compared to neutrophils that migrated across mock-infected nasal epithelial cells. Blocking of the interaction between the ligand on neutrophils (the β₂-integrin LFA-1) for intracellular adhesion molecule (ICAM)-1 on epithelial cells reduced neutrophil adherence to RSV-infected cells and epithelial cell damage to pre-infection levels, but did not reduce the numbers of neutrophils that migrated or prevent the reduction in infectious viral load.These findings have provided important insights into the contribution of neutrophils to airway damage and viral clearance, which are relevant to the pathophysiology of RSV bronchiolitis. This model is a convenient, quantitative preclinical model that will further elucidate mechanisms that drive disease severity and has utility in antiviral drug discovery.

Update on current views and advances on RSV infection (Review)

Respiratory syncytial virus (RSV) infection represents an excellent paradigm of precision medicine in modern paediatrics and several clinical trials are currently performed in the prevention and management of RSV infection. A new taxonomic terminology for RSV was recently adopted, while the diagnostic and omics techniques have revealed new modalities in the early identification of RSV infections and for better understanding of the disease pathogenesis. Coordinated clinical and research efforts constitute an important step in limiting RSV global predominance, improving epidemiological surveillance, and advancing neonatal and paediatric care. This review article presents the key messages of the plenary lectures, oral presentations and posters of the '5th workshop on paediatric virology' (Sparta, Greece, 12th October 2019) organized by the Paediatric Virology Study Group, focusing on recent advances in the epidemiology, pathogenesis, diagnosis, prognosis, clinical management and prevention of RSV infection in childhood.

White L, Poovorawan K, Soonthornworasiri N, Sukontamarn P, Chanthavilay P, F. Medley G, Pan-ngum W. Modeling household dynamics on Respiratory Syncytial Virus (RSV)

Respiratory Syncytial Virus (RSV) is the most common cause of respiratory tract infection in infants and children and shows increasing trend among elderly people worldwide. In many developing country settings, population and household structures have gone through some significant changes in the past decades, namely fewer births, more elderly population, and smaller household size but more RSV high-risk individuals. These dynamics have been captured in a mathematical model with RSV transmission dynamics to predict the disease burden on the detailed population for future targeted interventions. The population and disease dynamics model was constructed and tested against the hospitalization data for Acute Lower Respiratory Tract Infection due to RSV in rural Thai settings between 2005 and 2011. The proportion of extended families is predicted to increase by about 10% from 2005 to 2020, especially for those with elderly population, while the classic nuclear family type (with adults and children) will decline by about 10%. For RSV, infections from extended family type (approximately 60% of all household types) have majorly contributed to the force of infection (FOI). While the model predicted the increase of FOI from the extended family by 15% from 2005 to 2020, the FOI contributed by other household types would be either stable or decrease in the same time period. RSV incidence rate is predominantly high among babies (92.2%) and has been predicted to decrease slightly over time (from 940 to 864 cases per 100,000 population by 2020), while the incidence rates among children and elderly people may remain steadily low over the same period. However, the estimated incidence rates among elderly people were twice than those in children. The model predicts that approximately 60% of FOI for RSV will come from members of the extended family type. The incidence rate of RSV among children and elderly in extended families was about 20 times lower than that in infants and the trend is steady. Targeted intervention strategies, such as health education in some specific groups and targeted vaccination, may be considered, with the focus on extended family type. Target interventions on babies can lessen the transmission to children and elderly especially when transmission within households of extended family type is high.

Role of Type I Interferon (IFN) in the Respiratory Syncytial Virus (RSV) Immune Response and Disease Severity

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract disease in children <2 years of age. Increased morbidity and mortality have been reported in high-risk patients, such as premature infants, patients with cardiac disease, and severely immune compromised patients. Severe disease is associated with the virulence of the virus as well as host factors specifically including the innate immune response. The role of type I interferons (IFNs) in the response to RSV infection is important in regulating the rate of virus clearance and in directing the character of the immune response, which is normally associated with protection and less severe disease. Two RSV non-structural proteins, NS1 and NS2, as well as the envelope G glycoprotein are known to suppress type I IFN production and a robust type I IFN response to RSV does not occur in human infants or neonatal mouse models of RSV infection. Additionally, presence of type I IFNs are associated with mild symptoms in infants and administration of IFN-α prior to infection of neonatal mice with RSV reduces immunopathology. This evidence has driven RSV prophylaxis and therapeutic efforts to consider strategies for enhancing type I IFN production.

Detection of ON1 and novel genotypes of human respiratory syncytial virus and emergence of palivizumab resistance in Lebanon

Respiratory syncytial virus (RSV) is a common cause of respiratory tract infections in children and immunocompromised individuals. A multi-center surveillance of the epidemiologic and molecular characteristics of RSV circulating in Lebanon was performed. The attachment (G) and fusion (F) glycoproteins were analyzed and compared to those reported regionally and globally. 16% (83/519) of the nasopharyngeal swabs collected during the 2016/17 season tested positive for RSV; 50% (27/54) were RSV-A and 50% (27/54) were RSV-B. Phylogenetic analysis of the G glycoprotein revealed predominance of the RSVA ON1 genotype, in addition to two novel Lebanese genotype variants, hereby named LBA1 and LBA2, which descended from the ON1 and NA2 RSV-A genotypes, respectively. RSV-B strains belonged to BA9 genotype except for one BA10. Deduced amino acid sequences depicted several unique substitutions, alteration of glycosylation patterns and the emergence of palivizumab resistance among the Lebanese viruses. The emergence of ON1 and other novel genotypes that are resistant to palivizumab highlights the importance of monitoring RSV globally.

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.

Exchange Proteins Directly Activated by cAMP and Their Roles in Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of respiratory infection in young children and high-risk adults. However, a specific treatment for this viral infection is not currently available. In this study, we discovered that an exchange protein directly activated by cyclic AMP (EPAC) can serve as a potential therapeutic target for RSV. In both lower and upper epithelial cells, treatment with EPAC inhibitor (ESI-09), but not protein kinase A inhibitor (H89), significantly inhibits RSV replication and proinflammatory cytokine/chemokine induction. In addition, RSV-activated transcriptional factors belonging to the NF-κB and IRF families are also suppressed by ESI-09. Through isoform-specific gene knockdown, we found that EPAC2, but not EPAC1, plays a dominant role in controlling RSV replication and virus-induced host responses. Experiments using both EPAC2 knockout and EPAC2-specific inhibitor support such roles of EPAC2. Therefore, EPAC2 is a promising therapeutic target to regulate RSV replication and associated inflammation.IMPORTANCE RSV is a serious public health problem, as it is associated with bronchiolitis, pneumonia, and asthma exacerbations. Currently no effective treatment or vaccine is available, and many molecular mechanisms regarding RSV-induced lung disease are still significantly unknown. This project aims to elucidate an important and novel function of a protein, called EPAC2, in RSV replication and innate inflammatory responses. Our results should provide an important insight into the development of new pharmacologic strategies against RSV infection, thereby reducing RSV-associated morbidity and mortality.