Respiratory syncytial virus: current progress in vaccine development

Virus reduction neutralization test and LI-COR microneutralization assay bridging and WHO international standard calibration studies for respiratory syncytial virus

Background: Respiratory syncytial virus (RSV) vaccine is an unmet medical need. The virus reduction neutralization test (VRNT) was developed to replace the LI-COR microneutralization assay to measure RSV neutralization titers. Methods: A bridging study using selected V171 phase I samples and calibration studies using the WHO international standard antiserum to RSV were performed to compare VRNT and LI-COR. Results: From the bridging study, we showed good concordance between VRNT and LI-COR titers, and similar post-/pre-vaccination titer ratios. From the calibration studies, we can convert VRNT and LI-COR titers into similar IU/ml. Conclusion: The VRNT and LI-COR microneutralization assay correlate well and the titers can be standardized as similar IU/ml, enabling direct comparison of titers from different assays.

Development and comparison of three cell-based potency assays for anti-respiratory syncytial virus monoclonal antibody

There is an increasing demand for monoclonal antibody (mAb) therapies to confer passive immunity against viral diseases. Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis, lower respiratory tract infections, and hospitalization in infants. Currently, there is no RSV vaccine but a humanized mAb available for high risk infants. MK-1654 is a fully human mAb with YTE mutation in the fragment crystallizable (Fc) region to extend the half-life in circulation. It binds to a highly conserved epitope of RSV Fusion protein with high affinity and neutralizes RSV infection. A functional cell-based assay is a regulatory requirement for clinical development, commercial release, and stability testing of MK-1654. In this study, we have evaluated three RSV neutralization assays to test the potency of MK-1654, including an imaging-based virus reduction neutralization test (VRNT) and two reporter virus-based assays (RSV-GFP and RSV-NLucP). All three methods showed good dose response curves of MK-1654 with similar EC50 values. RSV-NLucP method was chosen for further development because it is simple and can be easily adapted to quality control testing laboratories. After optimization, the RSV-NLucP assay was pre-qualified with good linearity, relative accuracy, intermediate precision, and specificity, therefore suitable for a cell-based potency assay.

Development and qualification of a fast, high-throughput and robust imaging-based neutralization assay for respiratory syncytial virus

Respiratory syncytial virus (RSV) is a common pathogen causing severe respiratory illness in infants and elder adults. The development of an effective RSV vaccine is an important unmet medical need and an area of active research. The traditional method for testing neutralizing antibodies against RSV in clinical trials is the plaque reduction neutralization test (PRNT), which uses 24-well plates and needs several days post infection to develop viral plaques. In this study, we have developed a virus reduction neutralization test (VRNT), which allows the number of RSV infected cells to be automatically counted by an imaging cytometer at one day post infection in 96-well plates. VRNT was found robust to cell seeding density, detection antibody concentration, virus input and infection time. By testing twenty human sera, we have shown good correlation between VRNT50 and PRNT50 titers for multiple RSV strains: A2, Long and 18537 (serotype B). To understand the VRNT performance, eight human serum samples with high, medium and low neutralization titers were selected for VRNT qualification. We have demonstrated that VRNT had good specificity, precision, linearity and relative accuracy. In conclusion, VRNT is a better alternative to PRNT in serum neutralization test for RSV vaccine candidates.

Vaccine Design Informed by Virus-Induced Immunity

When an individual is exposed to a viral pathogen for the first time, the adaptive immune system is naive and cannot prevent virus replication. The consequence may be severe disease. At the same time, the host may rapidly generate a pathogen-specific immune response that will prevent disease if the virus is encountered again. Parvovirus B19 provides one such example. Children with sickle cell disease can experience life-threatening transient aplastic crisis when first exposed to parvovirus B19, but an effective immune response confers lifelong protection. We briefly examine the induction and benefits of virus-induced immunity. We focus on three human viruses for which there are no licensed vaccines (respiratory syncytial virus, human immunodeficiency virus type 1, and parvovirus B19) and consider how virus-induced immunity may inform successful vaccine design.

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Application of metabolomics in viral pneumonia treatment with traditional Chinese medicine

Nowadays, traditional Chinese medicines (TCMs) have been reported to provide reliable therapies for viral pneumonia, but the therapeutic mechanism remains unknown. As a systemic approach, metabolomics provides an opportunity to clarify the action mechanism of TCMs, TCM syndromes or after TCM treatment. This review aims to provide the metabolomics evidence available on TCM-based therapeutic measures against viral pneumonia. Metabolomics has been gradually applied to the efficacy evaluation of TCMs in treatment of viral pneumonia and the metabolomics analysis exhibits a systemic metabolic shift in lipid, amino acids, and energy metabolism. Currently, most studies of TCM in treatment of viral pneumonia are untargeted metabolomics and further validations on targeted metabolomics should be carried out together with molecular biology technologies.

Potent anti-viral vaccine adjuvant based on pH-degradable nanogels with covalently linked small molecule imidazoquinoline TLR7/8 agonist

Improving the immunogenicity of subunit vaccines, in particular skewing of the immune response towards Th1 type immunity, is crucial for the development of effective vaccines against intracellular infections and for the development of anti-cancer vaccines. Small molecule TLR7/8 agonist hold high potential for this purpose, but suffer from an undesirable pharmacokinetic profile, resulting in systemic inflammatory responses. An effective solution to this problem is covalent ligation to a larger carrier. Here, a degradable nanogel carrier containing a covalently linked imidazoquinoline (IMDQ) TLR7/8 agonist is explored as adjuvant for vaccination against the respiratory syncytial virus (RSV). In vitro and in vivo experiments in mice provide a solid rational base for preferring nanogels over soluble polymers as IMDQ carrier in terms of cellular uptake and lymph node accumulation.

Novel recombinant DNA vaccine candidates for human respiratory syncytial virus: Preclinical evaluation of immunogenicity and protection efficiency

The development of safe and potent vaccines for human respiratory syncytial virus (HRSV) is still a challenge for researchers worldwide. DNA-based immunization is currently a promising approach that has been used to generate human vaccines for different age groups. In this study, novel HRSV DNA vaccine candidates were generated and preclinically tested in BALB/c mice. Three different versions of the codon-optimized HRSV fusion (F) gene were individually cloned into the pPOE vector. The new recombinant vectors either express full-length (pPOE-F), secretory (pPOE-TF), or M2_82-90 linked (pPOE-FM2) forms of the F protein. Distinctive expression of the F protein was identified in HEp-2 cells transfected with the different recombinant vectors using ELISA and immunofluorescence. Mice immunization verified the potential for recombinant vectors to elicit significant levels of neutralizing antibodies and CD8⁺ T-cell lymphocytes. pPOE-TF showed higher levels of gene expression in cell culture and better induction of the humoral and cellular immune responses. Following virus challenge, mice that had been immunized with the recombinant vectors were able to control virus replication and displayed lower inflammation compared with mice immunized with empty pPOE vector or formalin-inactivated HRSV vaccine. Moreover, pulmonary cytokine profiles of mice immunized with the 3 recombinant vectors were similar to those of the mock infected group. In conclusion, recombinant pPOE vectors are promising HRSV vaccine candidates in terms of their safety, immunogenicity and protective efficiency. These data encourage further evaluation in phase I clinical trials.

CD4+ T cells support establishment of RSV-specific IgG and IgA antibody secreting cells in the upper and lower murine respiratory tract following RSV infection

The RSV vaccine field suffered a major set-back when children were vaccinated with a formalin-inactivated RSV vaccine (FI-RSV). Unexpectedly, the vaccinated children fared worse than unvaccinated children when they were naturally infected with RSV. Mouse models were then developed that implicated the CD4⁺ T helper cell population as a contributor to adverse events. Today, the T cell is viewed with much caution in the RSV field, and its induction by vaccination is sometimes discouraged. Here we re-emphasize the beneficial role of the CD4⁺ T cell. Experiments were performed with RSV-infected nude mice that received CD4⁺ T cells by adoptive transfer. Data demonstrated that CD4⁺ T cells were necessary for the induction of mucosal and systemic RSV-specific antibodies, for the establishment of RSV-specific IgG and IgA antibody secreting cells in the upper and lower respiratory tract, and for RSV clearance.

Application of Traditional Chinese Medical Herbs in Prevention and Treatment of Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is a common viral pathogen of the lower respiratory tract, which, in the absence of effective management, causes millions of cases of severe illness per year. Many of these infections develop into fatal pneumonia. In a review of English and Chinese medical literature, recent traditional Chinese medical herb- (TCMH-) based progress in the area of prevention and treatment was identified, and the potential anti-RSV compounds, herbs, and formulas were explored. Traditional Chinese medical herbs have a positive effect on inhibiting viral attachment, inhibiting viral internalization, syncytial formation, alleviation of airway inflammation, and stimulation of interferon secretion and immune system; however, the anti-RSV mechanisms of TCMHs are complicated, which should be further investigated.

Human Respiratory Syncytial Virus: Infection and Pathology

The human respiratory syncytial virus (hRSV) is by far the major cause of acute lower respiratory tract infections (ALRTIs) worldwide in infants and children younger than 2 years. The overwhelming number of hospitalizations due to hRSV-induced ALRTI each year is due, at least in part, to the lack of licensed vaccines against this virus. Thus, hRSV infection is considered a major public health problem and economic burden in most countries. The lung pathology developed in hRSV-infected individuals is characterized by an exacerbated proinflammatory and unbalanced Th2-type immune response. In addition to the adverse effects in airway tissues, hRSV infection can also cause neurologic manifestations in the host, such as seizures and encephalopathy. Although the origins of these extrapulmonary symptoms remain unclear, studies with patients suffering from neurological alterations suggest an involvement of the inflammatory response against hRSV. Furthermore, hRSV has evolved numerous mechanisms to modulate and evade the immune response in the host. Several studies have focused on elucidating the interactions between hRSV virulence factors and the host immune system, to rationally design new vaccines and therapies against this virus. Here, we discuss about the infection, pathology, and immune response triggered by hRSV in the host.

Development of Electrochemiluminescent Serology Assays to Measure the Humoral Response to Antigens of Respiratory Syncytial Virus

Sensitive and precise serology assays are needed to measure the humoral response to antigens of respiratory syncytial virus (RSV) following natural infection or vaccination. We developed and evaluated a collection of electrochemiluminescent (ECL) serology assays using four RSV antigens (F, N, Ga and Gb). To assess the merits of ECL technology, the four ECL serology assays were evaluated using a well-characterized "gold standard" panel of acute and convalescent serum samples from fifty-nine RSV-positive and thirty RSV-negative elderly subjects (≥65 years old). The combined results from the four ECL assays demonstrated good concordance to the "gold standard" diagnosis, reaching 95% diagnostic sensitivity and 100% diagnostic specificity. Additionally, a combination of ECL assays provided higher diagnostic sensitivity than a commercially available diagnostic ELISA or cell-based microneutralization assay. In summary, these data demonstrate the advantages of using ECL-based serology assays and highlight their use as a sensitive diagnostic approach to detect recent RSV infection in an elderly population.

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.

Cross-immunity between strains explains the dynamical pattern of paramyxoviruses

Viral respiratory tract diseases pose serious public health problems. Our ability to predict and thus, be able to prepare for outbreaks is strained by the complex factors driving the prevalence and severity of these diseases. The abundance of diseases and transmission dynamics of strains are not only affected by external factors, such as weather, but also driven by interactions among viruses mediated by human behavior and immunity. To untangle the complex out-of-phase annual and biennial pattern of three common paramyxoviruses, Respiratory Syncytial Virus (RSV), Human Parainfluenza Virus (HPIV), and Human Metapneumovirus (hMPV), we adopt a theoretical approach that integrates ecological and immunological mechanisms of disease interactions. By estimating parameters from multiyear time series of laboratory-confirmed cases from the intermountain west region of the United States and using statistical inference, we show that models of immune-mediated interactions better explain the data than those based on ecological competition by convalescence. The strength of cross-protective immunity among viruses is correlated with their genetic distance in the phylogenetic tree of the paramyxovirus family.

The preventive effect of vaccine prophylaxis on severe respiratory syncytial virus infection: A meta-analysis

Respiratory syncytial virus (RSV) is the key underlying cause of acute lower respiratory tract infection in infants; however, no licensed vaccine against RSV infection is currently available. This study was undertaken to assess the preventive effect of vaccine on RSV infection. In this metaanalysis, 1,792 published randomized clinical trials of RSV vaccines from Jan 1973 to Sep 2015 were examined. Among thirteen studies that met the inclusion criteria, eleven studies estimated the impact of RSV vaccines and four studies estimated the effect of adjuvants. The odds ratios (ORs) were 0.31 (95% CI, 0.15-0.67) and 0.62 (95% CI, 0.29-1.34), respectively. We found that RSV subunit vaccines can significantly reduce the incidence of RSV infection and that whether vaccination with adjuvant therapy was an effective strategy still remained to be studied. This analysis of the preventive effect of vaccines on RSV infection has direct applications for the prevention of RSV infections.

Innate and adaptive cellular phenotypes contributing to pulmonary disease in mice after respiratory syncytial virus immunization and infection

Respiratory syncytial virus (RSV) is the major leading cause of infantile viral bronchiolitis. However, cellular phenotypes contributing to the RSV protection and vaccine-enhanced disease remain largely unknown. Upon RSV challenge, we analyzed phenotypes and cellularity in the lung of mice that were naïve, immunized with formalin inactivated RSV (FI-RSV), or re-infected with RSV. In comparison with naïve and live RSV re-infected mice, the high levels of eosinophils, neutrophils, plasmacytoid and CD11b(+) dendritic cells, and IL-4(+) CD4(+) T cells were found to be contributing to pulmonary inflammation in FI-RSV immune mice despite lung viral clearance. Alveolar macrophages appeared to play differential roles in protection and inflammation upon RSV infection of different RSV immune mice. These results suggest that multiple innate and adaptive immune components differentially contribute to RSV disease and inflammation.

Neutralizing epitopes on the respiratory syncytial virus fusion glycoprotein

Respiratory syncytial virus (RSV) is a leading cause of pneumonia and bronchiolitis, but despite decades of research a safe and effective vaccine has remained elusive. The viral fusion glycoprotein (RSV F) plays an obligatory role in the entry process and is the major target of neutralizing antibodies, making it an attractive target for vaccine development. This review will summarize the recently determined structures of RSV F in the prefusion and postfusion conformations and describe the location and properties of neutralizing epitopes on RSV F, including the newly identified prefusion-specific epitopes. The influence of these findings on vaccine development will also be discussed, with a focus on the rational design and optimization of vaccine antigens.

Short Peptide Vaccine Design and Development: Promises and Challenges

Vaccine development for viral diseases is a challenge where subunit vaccines are often ineffective. Therefore, the need for alternative solutions is crucial. Thus, short peptide vaccine candidates promise effective answers under such circumstances. Short peptide vaccine candidates are linear T-cell epitopes (antigenic determinants that are recognized by the immune system) that specifically function by binding human leukocyte antigen (HLA) alleles of different ethnicities (including Black, Caucasian, Oriental, Hispanic, Pacific Islander, American Indian, Australian aboriginal, and mixed ethnicities). The population-specific allele-level HLA sequence data in the public IMGT/HLA database contains approximately 12542 nomenclature defined class I (9437) and class II (3105) HLA alleles as of March 2015 present in several ethnic populations.

The bottleneck in short peptide vaccine design and development is HLA polymorphism on the one hand and viral diversity on the other hand. Hence, a crucial step in its design and development is HLA allele-specific binding of short antigen peptides. This is usually combinatorial and computationally labor intensive. Mathematical models utilizing structure-defined pockets are currently available for class I and class II HLA-peptide-binding peptides. Frameworks have been developed to design protocols to identify the most feasible short peptide cocktails as vaccine candidates with superantigen properties among known HLA supertypes. This approach is a promising solution to develop new viral vaccines given the current advancement in T-cell immuno-informatics, yet challenging in terms of prediction efficiency and protocol development.

Sendai virus recombinant vaccine expressing a secreted, unconstrained respiratory syncytial virus fusion protein protects against RSV in cotton rats

The respiratory syncytial virus (RSV) is responsible for as many as 199000 annual deaths worldwide. Currently, there is no standard treatment for RSV disease and no vaccine. Sendai virus (SeV) is an attractive pediatric vaccine candidate because it elicits robust and long-lasting virus-specific B cell and T cell activities in systemic and mucosal tissues. The virus serves as a gene delivery system as well as a Jennerian vaccine against its close cousin, human parainfluenza virus type 1. Here we describe the testing of a recombinant SeV (SeVRSV-Fs) that expresses an unconstrained, secreted RSV-F protein as a vaccine against RSV in cotton rats. After a single intranasal immunization of cotton rats with SeVRSV-Fs, RSV-specific binding and neutralizing antibodies were generated. These antibodies exhibited cross-reactivity with both RSV A and B isolates. RSV-F-specific IFN-γ-producing T cells were also activated. The SeVRSV-Fs vaccine conferred protection against RSV challenge without enhanced immunopathology. In total, results showed that an SeV recombinant that expresses RSV F in an unconstrained, soluble form can induce humoral and cellular immunity that protects against infection with RSV.

Safety and Effectiveness of Palivizumab in Children at High Risk of Serious Disease Due to Respiratory Syncytial Virus Infection: A Systematic Review

INTRODUCTION

Lower respiratory tract infection (LRTI) is the leading cause of infant mortality globally in post-neonatal infants (i.e., 28-364 days of age). Respiratory syncytial virus (RSV) is the most commonly identified pathogen for infant LRTI and is the second most important cause of death in post-neonatal infants. Despite 50 years of RSV vaccine research, there is still no approved vaccine. Therefore, passive immunity with the monoclonal antibody palivizumab is the sole regulatory-approved option for the prevention of serious LRTI caused by RSV in pediatric patients at high risk of RSV disease.

METHODS

We conducted a comprehensive systematic literature review of randomized controlled trials (RCTs), open-label non-comparative clinical trials, and prospective observational studies/registries, and summarized the evidence related to the safety, efficacy, and effectiveness of palivizumab.

RESULTS

The efficacy of palivizumab, as measured by the relative reduction in RSV-related hospitalization rate compared with placebo ranged from 39% to 78% (P < 0.05) in the 2 pivotal RCTs. A meta-analysis of the RSV-related hospitalization rate from 5 randomized placebo-controlled trials yielded an overall odds ratio of 0.41 (95% CI, 0.31-0.55) in favor of palivizumab prophylaxis over placebo (P < 0.00001). Low rates of RSV-related hospitalizations were observed in palivizumab recipients consistently over time in more than 42,000 pediatric subjects across 7 RCTs, 4 open-label non-comparative trials, and 8 observational studies/registries conducted in 34 countries. In addition, among palivizumab-prophylaxed subjects with breakthrough RSV LRTI, rates of intensive care unit admission and mechanical ventilation from RSV hospitalization also were low and consistent across studies. With respect to safety, no differences were observed between palivizumab and placebo in the blinded RCTs.

CONCLUSION

Rates of RSV hospitalizations and RSV hospitalization-related endpoints in pediatric subjects who received prophylaxis with palivizumab were low and constant over time and across RCTs, open-label non-comparative trials, and observational studies/registries.

Central nervous system alterations caused by infection with the human respiratory syncytial virus

Worldwide, the human respiratory syncytial virus (hRSV) is the leading cause of infant hospitalization because of acute respiratory tract infections, including severe bronchiolitis and pneumonia. Despite intense research, to date there is neither vaccine nor treatment available to control hRSV disease burden globally. After infection, an incubation period of 3-5 days is usually followed by symptoms, such as cough and low-grade fever. However, hRSV infection can also produce a larger variety of symptoms, some of which relate to the individual's age at infection. Indeed, infants can display severe symptoms, such as dyspnea and chest wall retractions. Upon examination, crackles and wheezes are also common features that suggest infection by hRSV. Additionally, infection in infants younger than 1 year is associated with several non-specific symptoms, such as failure to thrive, periodic breathing or apnea, and feeding difficulties that usually require hospitalization. Recently, neurological symptoms have also been associated with hRSV respiratory infection and include seizures, central apnea, lethargy, feeding or swallowing difficulties, abnormalities in muscle tone, strabismus, abnormalities in the CSF, and encephalopathy. Here, we discuss recent findings linking the neurological, extrapulmonary effects of hRSV with infection and functional impairment of the CNS.

Respiratory syncytial virus genotypes circulating in urban Ghana: February to November 2006

Introduction

Respiratory syncytial virus (RSV) is the major cause of acute lower respiratory tract infection (ALRI) in young children. RSV strains have been divided into 2 major antigenic groups (A and B), which are further divided into several genotypes, but very little is known about its circulating genotypes in Ghana. This study characterized RSV genotypes detected in children with ALRI in Accra between February and November 2006.

Methods

Nasopharyngeal aspirates (NPA) were obtained from children diagnosed with ALRI between February and November 2006. The NPA were screened for RSV using a nested multiplex reverse transcriptase polymerase chain reaction (RT-PCR) method for genotyping RSV. Viral RNA was extracted from the NPA using guanidinium isothiocyanate method and purified with an RNAID commercial kit. Care-givers gave their consent prior to specimen collection. Administered questionnaires captured information on patient demographic and clinical history.

Results

A total of 53 children were enrolled in the study with a male to female ratio of 3:1. Of the 53 NPA analyzed, 60.4% (32/53) were positive for RSV. Subsequent genotypic analysis showed that 72% (23/32) of the 60.4% RSV infections were RSV B only and 28% (9/32) were co-infections of both RSV A and B. Children between the ages of 2 - 12 months were the most affected age group per an RSV infection rate of 37.5% (12/32). No significant difference was detected in the recovery rate of ALRI (98.1%) and RSV (96.9%) positive patients from the infection. One patient died resulting in a mortality rate of 3.1%. Bronchopneumonia (20 out of 32 cases) was the major diagnosis on admission. RSV infection was seasonal dependent, described by 2 peaks in October and April-May.

Conclusion

Both RSV A and RSV B genotypes co-circulated during the study period with RSV B predominating. RSV may possibly be the main pathogen of lower respiratory tract illness during epidemics in the wet seasons. Genotyping by the multiplex RT-PCR is one of the first attempts at molecular diagnosis of RSV infection in Ghana.

Sustained inflammation and differential expression of interferons type I and III in PVM-infected interferon-gamma (IFNγ) gene-deleted mice

Interferon gamma (IFNγ) has complex immunomodulatory and antiviral properties. While IFNγ is detected in the airways in response to infection with the pneumovirus pathogen, pneumonia virus of mice (PVM; Family Paramyxoviridae), its role in promoting disease has not been fully explored. Here, we evaluate PVM infection in IFNγ(-/-) mice. Although the IFNγ gene-deletion has no impact on weight loss, survival or virus kinetics, expression of IFNβ, IFNλ2/3 and IFN-stimulated 2-5' oligoadenylate synthetases was significantly diminished compared to wild-type counterparts. Furthermore, PVM infection in IFNγ(-/-) mice promoted prominent inflammation, including eosinophil and neutrophil infiltration into the airways and lung parenchyma, observed several days after peak virus titer. Potential mechanisms include over-production of chemoattractant and eosinophil-active cytokines (CXCL1, CCL11, CCL3 and IL5) in PVM-infected IFNγ(-/-) mice; likewise, IFNγ actively antagonized IL5-dependent eosinophil survival ex vivo. Our results may have clinical implications for pneumovirus infection in individuals with IFNγ signaling defects.

Vaccine-induced anti-HA2 antibodies promote virus fusion and enhance influenza virus respiratory disease

Vaccine-induced disease enhancement has been described in connection with several viral vaccines in animal models and in humans. We investigated a swine model to evaluate mismatched influenza vaccine-associated enhanced respiratory disease (VAERD) after pH1N1 infection. Vaccinating pigs with whole inactivated H1N2 (human-like) virus vaccine (WIV-H1N2) resulted in enhanced pneumonia and disease after pH1N1 infection. WIV-H1N2 immune sera contained high titers of cross-reactive anti-pH1N1 hemagglutinin (HA) antibodies that bound exclusively to the HA2 domain but not to the HA1 globular head. No hemagglutination inhibition titers against pH1N1 (challenge virus) were measured. Epitope mapping using phage display library identified the immunodominant epitope recognized by WIV-H1N2 immune sera as amino acids 32 to 77 of pH1N1-HA2 domain, close to the fusion peptide. These cross-reactive anti-HA2 antibodies enhanced pH1N1 infection of Madin-Darby canine kidney cells by promoting virus membrane fusion activity. The enhanced fusion activity correlated with lung pathology in pigs. This study suggests a role for fusion-enhancing anti-HA2 antibodies in VAERD, in the absence of receptor-blocking virus-neutralizing antibodies. These findings should be considered during the evaluation of universal influenza vaccines designed to elicit HA2 stem-targeting antibodies.

Vaccine safety and efficacy evaluation of a recombinant bovine respiratory syncytial virus (BRSV) with deletion of the SH gene and subunit vaccines based on recombinant human RSV proteins: N-nanorings, P and M2-1, in calves with maternal antibodies

The development of safe and effective vaccines against both bovine and human respiratory syncytial viruses (BRSV, HRSV) to be used in the presence of RSV-specific maternally-derived antibodies (MDA) remains a high priority in human and veterinary medicine. Herein, we present safety and efficacy results from a virulent BRSV challenge of calves with MDA, which were immunized with one of three vaccine candidates that allow serological differentiation of infected from vaccinated animals (DIVA): an SH gene-deleted recombinant BRSV (ΔSHrBRSV), and two subunit (SU) formulations based on HRSV-P, -M2-1, and -N recombinant proteins displaying BRSV-F and -G epitopes, adjuvanted by either oil emulsion (Montanide ISA71^VG, SUMont) or immunostimulating complex matrices (AbISCO-300, SUAbis). Whereas all control animals developed severe respiratory disease and shed high levels of virus following BRSV challenge, ΔSHrBRSV-immunized calves demonstrated almost complete clinical and virological protection five weeks after a single intranasal vaccination. Although mucosal vaccination with ΔSHrBRSV failed to induce a detectable immunological response, there was a rapid and strong anamnestic mucosal BRSV-specific IgA, virus neutralizing antibody and local T cell response following challenge with virulent BRSV. Calves immunized twice intramuscularly, three weeks apart with SUMont were also well protected two weeks after boost. The protection was not as pronounced as that in ΔSHrBRSV-immunized animals, but superior to those immunized twice subcutaneously three weeks apart with SUAbis. Antibody responses induced by the subunit vaccines were non-neutralizing and not directed against BRSV F or G proteins. When formulated as SUMont but not as SUAbis, the HRSV N, P and M2-1 proteins induced strong systemic cross-protective cell-mediated immune responses detectable already after priming. ΔSHrBRSV and SUMont are two promising DIVA-compatible vaccines, apparently inducing protection by different immune responses that were influenced by vaccine-composition, immunization route and regimen.

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.

Mucosal vaccines against respiratory syncytial virus

Respiratory syncytial virus (RSV) is a leading cause of severe respiratory disease in infants, young children, immune-compromised and elderly populations worldwide. Natural RSV infection in young children does not elicit long-lasting immunity and individuals remain susceptible to repeated RSV infections throughout life. Because RSV infection is restricted to the respiratory tract, an RSV vaccine should elicit mucosal immunity at upper and lower respiratory tracts in order to most effectively prevent RSV reinfection. Although there is no safe and effective RSV vaccine available, significant progress has been recently made in basic RSV research and vaccine development. This review will discuss recent advances in the identification of a new neutralizing antigenic site within the RSV fusion (F) protein, understanding the importance of mucosal immune responses against RSV infection, and the development of novel mucosal vaccination strategies.

Population-based incidence of severe acute respiratory virus infections among children aged <5 years in rural Bangladesh, June-October 2010

Background

Better understanding the etiology-specific incidence of severe acute respiratory infections (SARIs) in resource-poor, rural settings will help further develop and prioritize prevention strategies. To address this gap in knowledge, we conducted a longitudinal study to estimate the incidence of SARIs among children in rural Bangladesh.

Methods

During June through October 2010, we followed children aged <5 years in 67 villages to identify those with cough, difficulty breathing, age-specific tachypnea and/or danger signs in the community or admitted to the local hospital. A study physician collected clinical information and obtained nasopharyngeal swabs from all SARI cases and blood for bacterial culture from those hospitalized. We tested swabs for respiratory syncytial virus (RSV), influenza viruses, human metapneumoviruses, adenoviruses and human parainfluenza viruses 1–3 (HPIV) by real-time reverse transcription polymerase chain reaction. We calculated virus-specific SARI incidence by dividing the number of new illnesses by the person-time each child contributed to the study.

Results

We followed 12,850 children for 279,029 person-weeks (pw) and identified 141 SARI cases; 76 (54%) at their homes and 65 (46%) at the hospital. RSV was associated with 7.9 SARI hospitalizations per 100,000 pw, HPIV3 2.2 hospitalizations/100,000 pw, and influenza 1.1 hospitalizations/100,000 pw. Among non-hospitalized SARI cases, RSV was associated with 10.8 illnesses/100,000 pw, HPIV3 1.8/100,000 pw, influenza 1.4/100,000 pw, and adenoviruses 0.4/100,000 pw.

Conclusion

Respiratory viruses, particularly RSV, were commonly associated with SARI among children. It may be useful to explore the value of investing in prevention strategies, such as handwashing and respiratory hygiene, to reduce respiratory infections among young children in such settings.

Epidemiology of respiratory syncytial virus in children in Cyprus during three consecutive winter seasons (2010-2013): age distribution, seasonality and association between prevalent genotypes and disease severity

This study reports the epidemiology of respiratory syncytial virus (RSV) in hospitalized children in Cyprus over three successive seasons (2010-2013) and the association between prevalent genotypes and disease severity. RSV infections had a circulation pattern from December to March. Most RSV-positive children (83%) were aged <2 years. Genotyping of RSV isolates showed that during the first winter season of the study (2010-2011), the only RSV genotype circulating was GA2 (RSV-A), followed by genotype BA (RSV-B) in the next winter season with only few sporadic cases of GA2. During the last winter season of the study (2012-2013) the newly emerged RSV genotype ON1 (RSV-A) was virtually the only circulating genotype. Children infected with genotype ON1 suffered a significantly milder illness compared to infections with genotypes GA2 and BA with a higher percentage of BA-infected children requiring oxygen. Our findings are in contrast to the majority of published reports that suggest RSV-A causes more severe illness than RSV-B. Therefore, further investigation of the association between RSV genotypes and disease severity is required, as it might affect treatment strategies in the future.

Current concepts and progress in RSV vaccine development

Respiratory syncytial virus (RSV) disease is an important cause of morbidity and mortality in children and debilitated adults and remains one of the major global unmet challenges for vaccine development. Several immunological issues have delayed the development of vaccines, especially the poorly protective response to natural infection and the enhancement of disease following administration of formalin inactivated vaccines during trials conducted in the 1960s. Advances in knowledge of the immune system, of the virus and its antigenic properties combined with new vaccine technologies are now injecting new hope into the field and have given rise to many promising vaccine approaches. Some of these may be optimal for use in children, while others may be more appropriate for pregnant women or vulnerable older adults. With a multi-pronged approach to prevention, we propose that it may be possible to destabilise community circulation of RSV and thus to significantly lessen the impact of RSV disease.

Gold nanoparticle-based enhanced ELISA for respiratory syncytial virus

A highly sensitive colorimetric immunoassay for the detection of RSV by adopting AuNPs as multienzyme carriers was developed.

Lamb model of respiratory syncytial virus-associated lung disease: insights to pathogenesis and novel treatments

Preterm birth is a risk factor for respiratory syncytial virus (RSV) bronchiolitis and hospitalization. The pathogenesis underlying this is not fully understood, and in vivo studies are needed to better clarify essential cellular features and molecular mechanisms. Such studies include analysis of lung tissue from affected human infants and various animal models. The preterm and newborn lamb lung has developmental, structural, cellular, physiologic, and immunologic features similar to that of human infants. Also, the lamb lung is susceptible to various strains of RSV that infect infants and cause similar bronchiolar lesions. Studies in lambs suggest that viral replication in airways (especially bronchioles) is extensive by 4 days after infection, along with bronchiolitis characterized by degeneration and necrosis of epithelial cells, syncytial cell formation, neutrophil infiltration, epithelial cell hypertrophy and hyperplasia, and innate and adaptive immune responses. RSV bronchiolitis greatly affects airflow and gaseous exchange. RSV disease severity is increased in preterm lambs compared with full-term lambs; similar to human infants. The lamb is conducive to experimental assessment of novel, mechanistic therapeutic interventions such as delivery of vascular endothelial growth factor and enhancement of airway epithelial oxidative responses, Club (Clara) cell protein 10, and synthesized compounds such as nanobodies. In contrast, exposure of the fetal ovine lung in vivo to ethanol, a risk factor for preterm birth, reduces pulmonary alveolar development and surfactant protein A expression. Because the formalin-inactivated RSV vaccination enhances some inflammatory responses to RSV infection in lambs, this model has the potential to assess mechanisms of formalin-inactivated RSV enhanced disease as well as newly developed vaccines.

The impact of influenza-like illness in young children on their parents: a quality of life survey

Background

Influenza-like illness can cause excess paediatric morbidity and burden on parents.

Objectives

We determined the quality of life (QoL) impact of children’s influenza-like illness (ILI) on their parents.

Methods

We conducted a prospective cohort study in childcare centres and a general practice in Sydney, Australia. Using PAR-ENT-QoL, we measured QoL of parents of children aged 6 months–3 years before the 2010 influenza season, then again for parents of children with ILI (ILI group) using SF-12v2 Acute Form and PAR-ENT-QoL, and contemporaneously for parents of aged-matched children without ILI (non-ILI group).

Results

Of 381 children enrolled from 90 childcare centres, 105 developed ILI. PAR-ENT-QoL scores of the ILI group were significantly lower in the post-ILI follow-up interviews than at baseline (60.99 vs. 79.77, p < 0.001), and those of non-ILI group at follow-up interviews (60.99 vs. 84.05, p < 0.001). SF-12v2 scores of the ILI group were also significantly lower than those of non-ILI group: physical component summary (50.66 vs. 53.16, p = 0.011) and mental component summary (45.67 vs. 53.66, p < 0.001). Two factors were significantly associated with parental QoL: total time spent caring child during ILI and whether the child had severe ILI or not. Correlations between PAR-ENT-QoL and SF-12v2 scores were satisfactory.

Conclusions

Parents had significantly lower QoL while their child had ILI, compared with before ILI and with parents of children without ILI. The public health impact of ILI in children on the QoL in families is far from negligible. QoL measurement can complement economic evaluation of ILI disease burden and provide a more complete picture of impact.

Respiratory syncytial virus infection as a cause of hospitalization in population under 1 year in Colombia

OBJECTIVE

to determine the frequency, complications and seasonality at which respiratory syncytial virus (RSV) infection of the lower respiratory tract causes hospitalization in infants of age 1 year or less in 6 cities of Colombia.

METHODS

one-year prospective multicentric observational study that included 717 patients presenting to the emergency department with respiratory symptoms in 6 cities of Colombia. Hospitalized children were tested for RSV with an immunofluorescence rapid test in nasopharyngeal secretions. Descriptive and statistical analyses of the population were conducted.

RESULTS

the study population included 717 patients with a mean age of 3.6 months (SD 3.25), 4:3 male: female ratio and a positive RSV LRTI prevalence of 30.0% (216 infants/City, range 26.0 - 49.0%). Risk factors for RSV LRTI were found in 8.2% of the population, of which 28.8% were RSV positive. RSV positive and negative groups were compared using a two-tailed t test with 95.0%CI, p < 0.05. No statistically significant differences were found. All cities presented specific year trimesters in the occurrence of RSV LRTI.

CONCLUSIONS

the RSV caused 1 in 3 LRTI hospitalizations in the population, with an incidence of 30.0%. This confirms a continuous circulation of RSV in Colombia varying by geographic location.

Development of a simple, rapid, sensitive, high-throughput luciferase reporter based microneutralization test for measurement of virus neutralizing antibodies following Respiratory Syncytial Virus vaccination and infection

We have established a new reporter gene-based RSV neutralization test using Renilla luciferase. The RSV-Luciferase Neutralization Test (RSV-Luc-NeuT) is a simple, rapid, high throughput, and less labor intensive functional serological assay than the traditional RSV-PRNT, capable of measuring a broad range of anti-RSV neutralizing antibodies targeting both RSV-F and RSV-G proteins. Specificity and sensitivity of the RSV-Luc-NeuT are comparable to the RSV-PRNT. Panels of pre-vaccination and post-vaccination animal sera, monoclonal antibodies and animal polyclonal anti-RSV sera confirmed assay specificity. A panel of 60 human sera demonstrated high assay sensitivity for measurement of RSV neutralizing antibodies that strongly correlated with the RSV-PRNT titers (R(2)=0.864). Neutralization in the presence of guinea pig complement (GPC) increased PRNT titers more than the RSV-Luc-NeuT neutralizing antibody titers for these human sera. This newly developed simple, high throughput, RSV-Luc-NeuT could be easily automated and applied in measurement of RSV neutralization titers in large vaccine trials.