Respiratory syncytial virus vaccine development

A chimeric influenza virus vaccine expressing fusion protein epitopes induces protection from human metapneumovirus challenge in mice

Human metapneumovirus (HMPV) is a common virus associated with acute respiratory distress syndrome in pediatric patients. There are no HMPV vaccines or therapeutics that have been approved for prevention or treatment. In this study, we constructed a novel recombinant influenza virus carrying partial HMPV fusion protein (HMPV-F), termed rFLU-HMPV/F-NS, utilizing reverse genetics, which contained (HMPV-F) in the background of NS segments of influenza virus A/PuertoRico/8/34(PR8). The morphological characteristics of rFLU-HMPV/F-NS were consistent with the wild-type flu virus. Additionally, immunofluorescence results showed that fusion proteins in the chimeric rFLU-HMPV/F-NS could work well, and the virus could be stably passaged in SPF chicken embryos. Furthermore, intranasal immunization with rFLU-HMPV/F-NS in BALB/c mice induced robust humoral, mucosal and Th1-type dominant cellular immune responses in vivo. More importantly, we discovered that rFLU-HMPV/F-NS afforded significant protective efficacy against the wild-type HMPV and influenza virus challenge, with significantly attenuated pathological changes and reduced viral titers in the lung tissues of immunized mice. Collectively, these findings demonstrated that chimeric recombinant rFLU-HMPV/F-NS as a promising HMPV candidate vaccine has potentials for the development of HMPV vaccine.

Development of Respiratory Syncytial Virus Vaccine Candidates for the Elderly

Respiratory syncytial virus (RSV) is a significant threat to elderly populations and repeated infections that occur throughout life are poorly protective. To assess the role of prior RSV infections as well as elderly immune senescence on vaccine efficacy, we compared immune responses after virus-like particle (VLP) immunization of elderly cotton rats and young cotton rats, both previously RSV infected, in order to mimic the human population. We show that immunization of RSV-experienced young or elderly animals resulted in the same levels of anti-pre-F IgG, anti-G IgG, neutralizing antibody titers, and protection from challenge indicating that the delivery of F and G proteins in a VLP is equally effective in activation of protective responses in both elderly and young populations. Our results suggest that F and G protein-containing VLPs induce anti-RSV memory established in prior RSV infections equally well in both young and elderly animals and thus can be an effective vaccine for the elderly.

Prevention and Treatment Strategies for Respiratory Syncytial Virus (RSV)

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease, especially in young children. Despite its global impact on healthcare, related to its high prevalence and its association with significant morbidity, the current therapy is still mostly supportive. Moreover, while more than 50 years have passed since the first trial of an RSV vaccine (which unfortunately caused enhanced RSV disease), no vaccine has been approved for RSV prevention. In the last two decades, our understanding of the pathogenesis and immunopathology of RSV have continued to evolve, leading to significant advancements in RSV prevention strategies. These include both the development of new potential vaccines and the successful implementation of passive immunization, which, together, will provide coverage from infancy to old age. In this review, we provide an update of the current treatment options for acute disease (RSV-specific and -non-specific) and different therapeutic approaches focusing on RSV prevention.

Recombinant Live Attenuated Influenza Virus Expressing Conserved G-Protein Domain in a Chimeric Hemagglutinin Molecule Induces G-Specific Antibodies and Confers Protection against Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is one of the most important pathogens causing significant morbidity and mortality in infants and the elderly. Live attenuated influenza vaccine (LAIV) is a licensed vaccine platform in humans and it is known to induce broader immune responses. RSV G attachment proteins mediate virus binding to the target cells and they contain a conserved central domain with neutralizing epitopes. Here, we generated recombinant LAIV based on the attenuated A/Puerto Rico/8/1934 virus backbone, expressing an RSV conserved G-domain in a chimeric hemagglutinin (HA) fusion molecule (HA-G). The attenuated phenotypes of chimeric HA-G LAIV were evident by restricted replication in the upper respiratory tract and low temperature growth characteristics. The immunization of mice with chimeric HA-G LAIV induced significant increases in G-protein specific IgG2a (T helper type 1) and IgG antibody-secreting cell responses in lung, bronchioalveolar fluid, bone marrow, and spleens after RSV challenge. Vaccine-enhanced disease that is typically caused by inactivated-RSV vaccination was not observed in chimeric HA-G LAIV as analyzed by lung histopathology. These results in this study suggest a new approach of developing an RSV vaccine candidate while using recombinant LAIV, potentially conferring protection against influenza virus and RSV.

Two RSV Platforms for G, F, or G+F Proteins VLPs

Respiratory syncytial virus (RSV) causes substantial lower respiratory tract disease in children and at-risk adults. Though there are no effective anti-viral drugs for acute disease or licensed vaccines for RSV, palivizumab prophylaxis is available for some high risk infants. To support anti-viral and vaccine development efforts, we developed an RSV virus-like particle (VLP) platform to explore the role RSV F and G protein interactions in disease pathogenesis. Since VLPs are immunogenic and a proven platform for licensed human vaccines, we also considered these VLPs as potential vaccine candidates. We developed two RSV VLP platforms, M+P and M+M2-1 that had F and G, F and a G peptide, or a truncated F and G on their surface. Immunoblots of sucrose gradient purified particles showed co-expression of M, G, and F with both VLP platforms. Electron microscopy imaging and immunogold labeling confirmed VLP-like structures with surface exposed projections consistent with F and G proteins. In mice, the VLPs induced both anti-F and -G protein antibodies and, on challenge, reduced lung viral titer and inflammation. These data show that these RSV VLP platforms provide a tool to study the structure of F and G and their interactions and flexible platforms to develop VLP vaccines in which all components contribute to RSV-specific immune responses.

Single-Dose, Intranasal Immunization with Recombinant Parainfluenza Virus 5 Expressing Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Spike Protein Protects Mice from Fatal MERS-CoV Infection

Middle East respiratory syndrome coronavirus (MERS-CoV) can cause severe and fatal acute respiratory disease in humans and remains endemic in the Middle East since first being identified in 2012. There are currently no approved vaccines or therapies available for MERS-CoV. In this study, we evaluated parainfluenza virus 5 (PIV5)-based vaccine expressing the MERS-CoV envelope spike protein (PIV5/MERS-S) in a human DPP4 knockin C57BL/6 congenic mouse model (hDPP4 KI). Following a single-dose intranasal immunization, PIV5-MERS-S induced neutralizing antibody and robust T cell responses in hDPP4 KI mice. A single intranasal administration of 10⁴ PFU PIV5-MERS-S provided complete protection against a lethal challenge with mouse-adapted MERS-CoV (MERS_MA6.1.2) and improved virus clearance in the lung. In comparison, single-dose intramuscular immunization with 10⁶ PFU UV-inactivated MERS_MA6.1.2 mixed with Imject alum provided protection to only 25% of immunized mice. Intriguingly, an influx of eosinophils was observed only in the lungs of mice immunized with inactivated MERS-CoV, suggestive of a hypersensitivity-type response. Overall, our study indicated that PIV5-MERS-S is a promising effective vaccine candidate against MERS-CoV infection.IMPORTANCE MERS-CoV causes lethal infection in humans, and there is no vaccine. Our work demonstrates that PIV5 is a promising vector for developing a MERS vaccine. Furthermore, success of PIV5-based MERS vaccine can be employed to develop a vaccine for emerging CoVs such as SARS-CoV-2, which causes COVID-19.

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

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

Original Antigenic Sin and Respiratory Syncytial Virus Vaccines

The original antigenic sin (OAS) theory considers the outcome of the first encounter with an antigen. It favors a memory response to the original antigen upon exposure to a similar or related antigen, and includes both positive and negative impacts of past exposure on the memory response to challenge, and, in particular, on vaccine efficacy. This phenomenon is closely linked with imprinting and the hierarchical nature of immune responses to previously encountered antigens. The focus of this commentary centers on the potential role of OAS or immunological imprinting on respiratory syncytial virus memory responses.

Biology of Infection and Disease Pathogenesis to Guide RSV Vaccine Development

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease in young children and a substantial contributor to respiratory tract disease throughout life and as such a high priority for vaccine development. However, after nearly 60 years of research no vaccine is yet available. The challenges to developing an RSV vaccine include the young age, 2-4 months of age, for the peak of disease, the enhanced RSV disease associated with the first RSV vaccine, formalin-inactivated RSV with an alum adjuvant (FI-RSV), and difficulty achieving protection as illustrated by repeat infections with disease that occur throughout life. Understanding the biology of infection and disease pathogenesis has and will continue to guide vaccine development. In this paper, we review the roles that RSV proteins play in the biology of infection and disease pathogenesis and the corresponding contribution to live attenuated and subunit RSV vaccines. Each of RSV's 11 proteins are in the design of one or more vaccines. The G protein's contribution to disease pathogenesis through altering host immune responses as well as its role in the biology of infection suggest it can make a unique contribution to an RSV vaccine, both live attenuated and subunit vaccines. One of G's potential unique contributions to a vaccine is the potential for anti-G immunity to have an anti-inflammatory effect independent of virus replication. Though an anti-viral effect is essential to an effective RSV vaccine, it is important to remember that the goal of a vaccine is to prevent disease. Thus, other effects of the infection, such as G's alteration of the host immune response may provide opportunities to induce responses that block this effect and improve an RSV vaccine. Keeping in mind the goal of a vaccine is to prevent disease and not virus replication may help identify new strategies for other vaccine challenges, such as improving influenza vaccines and developing HIV vaccines.

Burden of Respiratory Syncytial Virus Disease and Mortality Risk Factors in Argentina: 18 Years of Active Surveillance in a Children's Hospital

BACKGROUND

Respiratory syncytial virus is the leading cause of acute lower respiratory infection in children. We aimed to describe the clinical-epidemiologic pattern and risk factors for mortality associated with RSV infection.

METHODS

This is a prospective, cross-sectional study of acute lower respiratory infection in children admitted to the Children's Hospital during 2000 to 2017. Viral diagnosis was made by fluorescent antibody techniques or real-time-polymerase chain reaction. We compared clinical-epidemiologic characteristics of RSV infection in nonfatal versus fatal cases. Multiple logistic regression was used to identify independent predictors of mortality.

RESULTS

Of 15,451 patients with acute lower respiratory infection, 13,033 were tested for respiratory viruses and 5831 (45%) were positive: RSV 81.3% (4738), influenza 7.6% (440), parainfluenza 6.9% (402) and adenovirus 4.3% (251). RSV had a seasonal epidemic pattern coinciding with months of lowest average temperature. RSV cases show a case fatality rate of 1.7% (82/4687). Fatal cases had a higher proportion of prematurity (P < 0.01), perinatal respiratory history (P < 0.01), malnourishment (P < 0.01), congenital heart disease (P < 0.01), chronic neurologic disease (P < 0.01) and pneumonia at clinical presentation (P = 0.014). No significant difference between genders was observed. Most deaths occurred among children who had complications: respiratory distress (80.5%), nosocomial infections (45.7%), sepsis (31.7%) and atelectasis (13.4%). Independent predictors of RSV mortality were moderate-to-severe malnourishment, odds ratio (OR): 3.69 [95% confidence interval (CI): 1.98-6.87; P < 0.0001]; chronic neurologic disease, OR: 4.14 (95% CI: 2.12-8.08; P < 0.0001); congenital heart disease, OR: 4.18 (95% CI: 2.39-7.32; P< 0.0001); and the age less than 6 months, OR: 1.99 (95% CI: 1.24-3.18; P = 0.004).

CONCLUSIONS

RSV showed an epidemic pattern affecting mostly young children. Malnourishment, chronic neurologic disease, congenital heart disease and the age less than 6 months were the independent risk factors for RSV mortality.

Expanding severe acute respiratory infection (SARI) surveillance beyond influenza: The process and data from 1 year of implementation in Vietnam

BACKGROUND

In 2016, as a component of the Global Health Security Agenda, the Vietnam Ministry of Health expanded its existing influenza sentinel surveillance for severe acute respiratory infections (SARI) to include testing for 7 additional viral respiratory pathogens. This article describes the steps taken to implement expanded SARI surveillance in Vietnam and reports data from 1 year of expanded surveillance.

METHODS

The process of expanding the suite of pathogens for routine testing by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) included laboratory trainings, procurement/distribution of reagents, and strengthening and aligning SARI surveillance epidemiology practices at sentinel sites and regional institutes (RI).

RESULTS

Surveillance data showed that of 4003 specimens tested by the RI laboratories, 20.2% (n = 810) were positive for influenza virus. Of the 3193 influenza-negative specimens, 41.8% (n = 1337) were positive for at least 1 non-influenza respiratory virus, of which 16.2% (n = 518), 13.4% (n = 428), and 9.6% (n = 308) tested positive for respiratory syncytial virus, rhinovirus, and adenovirus, respectively.

CONCLUSIONS

The Government of Vietnam has demonstrated that expanding respiratory viral surveillance by strengthening and building upon an influenza platform is feasible, efficient, and practical.

A multifaceted approach to RSV vaccination

Respiratory Syncytial Virus (RSV) is the leading cause of pneumonia and bronchiolitis in infants, resulting in significant morbidity and mortality worldwide. In addition, RSV infections occur throughout different ages, thus, maintaining the virus in circulation, and increasing health risk to more susceptible populations such as infants, the elderly, and the immunocompromised. To date, there is no vaccine approved to prevent RSV infection or minimize symptoms of infection. Current clinical trials for vaccines against RSV are being carried out in four very different populations. There are vaccines that target two different pediatric populations, infants 2 to 6 month of age and seropositive children over 6 months of age, as well as women (non-pregnant or pregnant in their third trimester). There are vaccines that target adult and elderly populations. In this review, we will present and discuss RSV vaccine candidates currently in clinical trials. We will describe the preclinical studies instrumental for their advancement, with the goal of introducing new preclinical models that may more accurately predict the outcome of clinical vaccine studies.

Molecular epidemiology of respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major cause of viral acute respiratory tract infections in young children. The virus is characterised by distinct seasonality that is dependent upon the latitude and its ability to cause reinfection. Respiratory syncytial virus demonstrates a complex molecular epidemiology pattern as multiple strains and/or genotypes cocirculate during a single epidemic. Previous studies have investigated the relationship between RSV genetic diversity, reinfection, and clinical features. Here, we review the evidence behind this relationship together with the impact that the advancement of whole genome sequencing will have upon our understanding and the need for reconsidering the classification of RSV genotypes.

Altered regulatory cytokine profiles in cases of pediatric respiratory syncytial virus infection

Objectives

Regulatory cytokines are associated with viral infection. The objective of this study was to evaluate the relation between serum regulatory cytokines concentrations and respiratory syncytial virus (RSV) disease.

Methods

We enrolled 325 children aged < 24 months who were diagnosed with acute respiratory tract infection. Twenty age-matched healthy children were enrolled as controls. Nasopharyngeal swabs were analyzed to identify virus by reverse transcription polymerase chain reaction, and blood samples were taken to quantify the regulatory cytokine concentrations, including interleukin (IL)-35, IL-10 and transforming growth factor (TGF)-β1 using the Bio-Plex immunoassay or enzyme-linked immunosorbent assay.

Results

RSV disease was associated with a great regulatory cytokine response than healthy children, among 89 RSV-infected patients, serum IL-35 (P = .0001) and IL-10 (P = .006) was significantly elevated in comparison with healthy controls. Young children (0< age ≤6 months) with RSV infection had significantly lower IL-35 and IL-10 expression but needed more oxygen therapy and more severe disease comparing with older children (12< age <24 months). Comparing with mild group, the expression levels of IL-10 were significantly lower in children with moderate and severe disease (P = .012 and P = .005, respectively). And levels of IL-10 was inversely associated with total duration of RSV infection symptoms (r = − 0.311, P = .019).

Conclusion

Children with RSV infected had increased serum regulatory cytokine IL-10 and IL-35 concentrations. Elevated expression of IL-10 and IL-35 were contributed to protect hypoxia and reduce the severity of disease.

Pre-fusion RSV F strongly boosts pre-fusion specific neutralizing responses in cattle pre-exposed to bovine RSV

Human respiratory syncytial virus (hRSV) is responsible for serious lower respiratory tract disease in infants and in older adults, and remains an important vaccine need. RSV fusion (F) glycoprotein is a key target for neutralizing antibodies. RSV F stabilized in its pre-fusion conformation (DS-Cav1 F) induces high neutralizing antibody titers in naïve animals, but it remains unknown to what extent pre-fusion F can boost pre-existing neutralizing responses in RSV seropositive adults. We here assess DS-Cav1 F immunogenicity in seropositive cattle pre-exposed to bovine RSV, a virus closely related to hRSV. A single immunization with non-adjuvanted DS-Cav1 F strongly boosts RSV neutralizing responses, directed towards pre-fusion F-specific epitopes, whereas a post-fusion F is unable to do so. Vaccination with pre-fusion F thus represents a promising strategy for maternal immunization and for other RSV vaccine target populations such as older adults.

Determining the Seasonality of Respiratory Syncytial Virus in the United States: The Impact of Increased Molecular Testing

Background

In the United States, the seasonality of respiratory syncytial virus (RSV) has traditionally been defined on the basis of weeks during which antigen-based tests detect RSV in >10% of specimens (hereafter, the "10% threshold"). Because molecular testing has become more widely used, we explored the extent of polymerase chain reaction (PCR)-based RSV testing and its impact on determining the seasonality of RSV.

Methods

We assessed antigen- and PCR-based RSV reports submitted to the National Respiratory and Enteric Virus Surveillance System during July 2005-June 2015. To characterize RSV seasons by using PCR-based reports, we assessed the traditional 10% threshold; subsequently, we developed 3 methods based on either PCR-based detections or the percentage of positive test results.

Results

The annual number of PCR-based reports increased 200-fold during 2005-2015, while the annual number of antigen-based reports declined. The weekly percentage of specimens positive for RSV by PCR was less than that for antigen-detection tests; accordingly, the 10% threshold excluded detections by PCR and so was imprecise for characterizing RSV seasons. Among our PCR-specific approaches, the most sensitive and consistent method captured 96%-98% of annual detections within a season, compared with 82%-94% captured using the traditional method.

Conclusions

PCR-based reports are increasingly relevant for RSV surveillance and determining the seasonality of RSV. These PCR-specific methods provide a more comprehensive understanding of RSV trends, particularly in settings where testing and reporting are most active. Diagnostic practices will vary by locality and should be understood before choosing which method to apply.

Dose Selection for an Adjuvanted Respiratory Syncytial Virus F Protein Vaccine for Older Adults Based on Humoral and Cellular Immune Responses

This is the second phase 1 study of a respiratory syncytial virus (RSV) vaccine containing RSV fusion protein (sF) adjuvanted with glucopyranosyl lipid A (GLA) in a squalene-based 2% stable emulsion (GLA-SE). In this randomized, double-blind study, 261 subjects aged ≥60 years received inactivated influenza vaccine (IIV), a vaccine containing 120 μg sF with escalating doses of GLA (1, 2.5, or 5 μg) in SE, or a vaccine containing 80 μg sF with 2.5 μg GLA in SE. Subjects receiving 120 μg sF with 2.5 or 5 μg GLA were also randomized to receive IIV or placebo. Immunity to RSV was assessed by detection of microneutralizing, anti-F immunoglobulin G, and palivizumab-competitive antibodies and F-specific gamma interferon enzyme-linked immunosorbent spot assay T-cell responses. Higher adjuvant doses increased injection site discomfort, but at the highest dose, the reactogenicity was similar to that of IIV. Significant humoral and cellular immune responses were observed. The 120 μg sF plus 5.0 μg GLA formulation resulted in the highest responses in all subjects and in older subjects. These results confirm previous observations of vaccine tolerability, safety, and immunogenicity and were used to select the 120 μg sF plus 5.0 μg GLA formulation for phase 2 evaluation. (This study has been registered at ClinicalTrials.gov under registration no. NCT02289820.)

Preclinical assessment of safety of maternal vaccination against respiratory syncytial virus (RSV) in cotton rats

Maternal immunization directed to control RSV infection in newborns and infants is an appealing vaccination strategy currently under development. In this work we have modeled maternal vaccination against RSV in cotton rats (CR) to answer two fundamental questions on maternal vaccine safety. We tested (i), whether a known, unsafe RSV vaccine (i.e., FI-RSV Lot 100 vaccine) induces vaccine enhanced disease in the presence of passively transferred, RSV maternal immunity, and (ii) whether the same FI-RSV vaccine could induce vaccine enhanced disease in CR litters when used to immunize their RSV-primed mothers. Our data show that FI-RSV immunization of pups with subsequent RSV infection results in vaccine-enhanced disease independent of whether the pups were born to RSV-seropositive or RSV-seronegative mothers, and that FI-RSV immunization of RSV-seropositive mothers does not present a health risk to either the mother or the infant. Our study also raises a novel concern regarding infant immunization, namely that "safe" RSV vaccines (e.g., live RSV administered intramuscularly) may induce vaccine-enhanced disease in RSV-infected pups born to seropositive mothers. Finally, we describe for the first time a sharp decrease in RSV neutralizing antibody titers in immunized seropositive CR at the time of delivery. This decline may reflect maternal immune suppression, potentially pinpointing a window of increased vulnerability to RSV infection that could be alleviated by effective immunization of expectant mothers.

Respiratory syncytial virus vaccines: an update on those in the immediate pipeline

Respiratory syncytial virus (RSV) is among the most common causes of lower respiratory tract infection among infants and the elderly worldwide. Despite its long history, no licensed vaccine is available. Recently, advances in the knowledge of RSV biology and pathology as well as the development of new techniques to generate vaccine candidates have increased the number of promising vaccines. The aim of this review is to analyze RSV characteristics, to consider the history of RSV vaccines and to discuss RSV vaccines currently in development. Among the candidates in clinical trials, nanoparticle and subunit vaccines seem to be the most promising for pregnant women and the elderly, whereas live-attenuated or vector-based vaccines appear to be optimal for the pediatric population.

Prefusion F-specific antibodies determine the magnitude of RSV neutralizing activity in human sera

Respiratory syncytial virus (RSV) is estimated to claim more lives among infants <1 year old than any other single pathogen, except malaria, and poses a substantial global health burden. Viral entry is mediated by a type I fusion glycoprotein (F) that transitions from a metastable prefusion (pre-F) to a stable postfusion (post-F) trimer. A highly neutralization-sensitive epitope, antigenic site Ø, is found only on pre-F. We determined what fraction of neutralizing (NT) activity in human sera is dependent on antibodies specific for antigenic site Ø or other antigenic sites on F in healthy subjects from ages 7 to 93 years. Adsorption of individual sera with stabilized pre-F protein removed >90% of NT activity and depleted binding antibodies to both F conformations. In contrast, adsorption with post-F removed ~30% of NT activity, and binding antibodies to pre-F were retained. These findings were consistent across all age groups. Protein competition neutralization assays with pre-F mutants in which sites Ø or II were altered to knock out binding of antibodies to the corresponding sites showed that these sites accounted for ~35 and <10% of NT activity, respectively. Binding competition assays with monoclonal antibodies (mAbs) indicated that the amount of site Ø-specific antibodies correlated with NT activity, whereas the magnitude of binding competed by site II mAbs did not correlate with neutralization. Our results indicate that RSV NT activity in human sera is primarily derived from pre-F-specific antibodies, and therefore, inducing or boosting NT activity by vaccination will be facilitated by using pre-F antigens that preserve site Ø.

Respiratory syncytial virus subtype ON1/NA1/BA9 predominates in hospitalized children with lower respiratory tract infections

Respiratory syncytial virus (RSV) infection is the leading cause of acute respiratory tract disease in children less than 5 years old. The aim of this study was to further elucidate the molecular properties and clinical characteristics of RSV infection. The study sample included 238 patients <5 years old who were hospitalized with clinical symptoms of upper or lower respiratory tract infection (URTI or LRTI) in the Pediatric Department at the First People's Hospital of Chenzhou, South China in 2014. We subjected nasopharyngeal aspirate (NPA) or nasal swab (NS) samples from the patients to indirect fluorescence assay screens. RSV G genes were amplified by reverse transcription‐PCR (RT‐PCR) and sequenced. Of the 238 patients screened, 64 (26.8%) were confirmed to have RSV infections. Of those 64 confirmed RSV infection cases, 39 (60.9%) had subtype BA9, 13 (20.3%) had the recently identified subtype ON1, 11 (17.2%) had subtype NA1, and 1 (1.6%) had subtype GB2. The predominant presentation was LRTI with coughing, sputum production, fever, and wheezing. RSV subtype NA1 and BA9 infections were found mostly in infants, whereas the age distribution of subtype ON1 infections was more uniform across the age bands. Phylogenetic analysis indicated that, compared with the prototype strain A2, all ON1 and most NA1 isolates had lost one potential N‐glycosylation site at amino acid 251 and 249 due to T251K and N249Y substitution, respectively. These findings suggest that NA1, BA9, and ON1 are the dominant RSV subtypes causing respiratory tract infections in young children presenting to the hospital in South China. J. Med. Virol. 89:213–221, 2017. © 2016 Wiley Periodicals, Inc.

Design and Evaluation of a Multi-Epitope Peptide of Human Metapneumovirus

OBJECTIVES

No licensed vaccines or therapeutic agents for human metapneumovirus (hMPV) infection exist to date. We aimed to construct a multi-epitope peptide (MEP) of hMPV to show promising results for epitope-based vaccine development.

METHODS

Six independent algorithms were screened to predict B-cell epitopes of hMPV, and three algorithms were used to predict cytotoxic T lymphocyte and T helper (Th) lymphocyte epitopes. Predicted epitopes were assembled in series with the spacers GPGPG and KK introduced, termed MEP. Recombinant mep genes were inserted into pET32a(+) plasmid and expressed in Escherichia coli strain BL21 (DE3). BALB/c mice were immunized with MEP with different adjuvants. Antibody titer, lymphocyte proliferation, cytotoxic T lymphocyte (CTL) activity and splenocyte cytokines were detected 2 weeks later after the last immunization. Microneutralization assay was used to detect neutralizing antibodies.

RESULTS

Six B-cell epitopes, four CTL epitopes and two Th epitopes were screened to construct the mep gene. Expressed MEP induced >104 antibodies in BALB/c mice, and produced anti-MEP antibody reacting with hMPV strains specifically as detected in indirect fluorescent assay (the titer was 160). The lymphocyte proliferation index, CTL activity and splenocyte cytokines of the MEP immunization groups were higher than in the control group (p < 0.05). Both IgG1 and IgG2a antibodies could be detected in the different groups, and balanced Th1/Th2 cytokines were secreted by splenocytes in these groups. The mean neutralizing titers of the MEP+CpG ODN, MEP+Alum and MEP+Alum+ CpG ODN groups were 87 (95% CI 50-126), 93 (95% CI 67-121) and 96 (95% CI 69-147), respectively.

CONCLUSION

MEP of hMPV elicited both strong humoral immunity and cell-mediated immunity in mice. The anti-MEP serum could neutralize hMPV infection in vitro. Joint use of CpG ODN and aluminum hydroxide adjuvants obtained the best immune effects. This study may contribute to hMPV epitope-based vaccine development.

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.

Epidemiology of laboratory-confirmed respiratory syncytial virus infection in young children in England, 2010–2014: the importance of birth month

The epidemiology of laboratory-confirmed respiratory syncytial virus (RSV) infections in young children has not recently been described in England, and is an essential step in identifying optimal target groups for future licensed RSV vaccines. We used two laboratory surveillance systems to examine the total number and number of positive RSV tests in children aged <5 years in England from 2010 to 2014. We derived odds ratios (ORs) with 95% confidence intervals (CIs) comparing children by birth month, using multivariable logistic regression models adjusted for age, season and sex. Forty-seven percent of RSV tests (29 851/63 827) and 57% (7405/13 034) of positive results in children aged <5 years were in infants aged <6 months. Moreover, 38% (4982/13 034) of positive results were in infants aged <3 months. Infants born in September, October and November had the highest odds of a positive RSV test during their first year of life compared to infants born in January (OR 2·1, 95% CI 1·7–2·7; OR 2·4, 95% CI 2·1–2·8; and OR 2·4, 95% CI 2·1–2·7, respectively). Our results highlight the importance of young age and birth month near the beginning of the RSV season to the risk of laboratory-confirmed RSV infection. Future control measures should consider protection for these groups.

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.

Understanding respiratory syncytial virus (RSV) vaccine development and aspects of disease pathogenesis

Respiratory syncytial virus (RSV) is the most important cause of lower respiratory tract infections causing bronchiolitis and some mortality in young children and the elderly. Despite decades of research there is no licensed RSV vaccine. Although significant advances have been made in understanding the immune factors responsible for inducing vaccine-enhanced disease in animal models, less information is available for humans. In this review, we discuss the different types of RSV vaccines and their target population, the need for establishing immune correlates for vaccine efficacy, and how the use of different animal models can help predict vaccine efficacy and clinical outcomes in humans.

The role of Th17 and Treg responses in the pathogenesis of RSV infection

The respiratory syncytial virus (RSV) represents the leading cause of viral bronchiolitis and pneumonia in children worldwide and is associated with high morbidity, hospitalization rate, and significant mortality rates. The immune response elicited by RSV is one of the main factors contributing to the pathogenesis of the disease. Two subsets of the cellular immune response, the T helper 17 cell (Th17) and the regulatory T-cell (Treg), and more particularly the balance between these two subsets, might play a significant role in the pathogenesis of the RSV infection. The developmental pathways of Th17 and Treg cells are closely and reciprocally interconnected and plasticity has been demonstrated from Treg toward Th17. During an RSV infection, the functions of both subsets are opposed to one another regarding viral clearance and clinical severity. Th17 and Treg cells offer a promising new view on the pathogenesis of an RSV infection and deserve further exploration.

[Development of new vaccines]

Recent and important advances in the fields of immunology, genomics, functional genomics, immunogenetics, immunogenomics, bioinformatics, microbiology, genetic engineering, systems biology, synthetic biochemistry, proteomics, metabolomics and nanotechnology, among others, have led to new approaches in the development of vaccines. The better identification of ideal epitopes, the strengthening of the immune response due to new adjuvants, and the search of new routes of vaccine administration, are good examples of advances that are already a reality and that will favour the development of more vaccines, their use in indicated population groups, or its production at a lower cost. There are currently more than 130 vaccines are under development against the more wished (malaria or HIV), difficult to get (CMV or RSV), severe re-emerging (Dengue or Ebola), increasing importance (Chagas disease or Leishmania), and nosocomial emerging (Clostridium difficile or Staphylococcus aureus) infectious diseases.

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.

Host proteome correlates of vaccine-mediated enhanced disease in a mouse model of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infants. Despite over 50 years of research, to date no safe and efficacious RSV vaccine has been licensed. Many experimental vaccination strategies failed to induce balanced T-helper (Th) responses and were associated with adverse effects such as hypersensitivity and immunopathology upon challenge. In this study, we explored the well-established recombinant vaccinia virus (rVV) RSV-F/RSV-G vaccination-challenge mouse model to study phenotypically distinct vaccine-mediated host immune responses at the proteome level. In this model, rVV-G priming and not rVV-F priming results in the induction of Th2 skewed host responses upon RSV challenge. Mass spectrometry-based spectral count comparisons enabled us to identify seven host proteins for which expression in lung tissue is associated with an aberrant Th2 skewed response characterized by the influx of eosinophils and neutrophils. These proteins are involved in processes related to the direct influx of eosinophils (eosinophil peroxidase [Epx]) and to chemotaxis and extravasation processes (Chil3 [chitinase-like-protein 3]) as well as to eosinophil and neutrophil homing signals to the lung (Itgam). In addition, the increased levels of Arg1 and Chil3 proteins point to a functional and regulatory role for alternatively activated macrophages and type 2 innate lymphoid cells in Th2 cytokine-driven RSV vaccine-mediated enhanced disease.

IMPORTANCE

RSV alone is responsible for 80% of acute bronchiolitis cases in infants worldwide and causes substantial mortality in developing countries. Clinical trials performed with formalin-inactivated RSV vaccine preparations in the 1960s failed to induce protection upon natural RSV infection and even predisposed patients for enhanced disease. Despite the clinical need, to date no safe and efficacious RSV vaccine has been licensed. Since RSV vaccines have a tendency to prime for unbalanced responses associated with an exuberant influx of inflammatory cells and enhanced disease, detailed characterization of primed host responses has become a crucial element in RSV vaccine research. We investigated the lung proteome of mice challenged with RSV upon priming with vaccine preparations known to induce phenotypically distinct host responses. Seven host proteins whose expression levels are associated with vaccine-mediated enhanced disease have been identified. The identified protein biomarkers support the development as well as detailed evaluation of next-generation RSV vaccines.

SABRE: a multicentre randomised control trial of nebulised hypertonic saline in infants hospitalised with acute bronchiolitis

Aim

Acute bronchiolitis is the commonest cause for hospitalisation in infancy. Supportive care remains the cornerstone of current management and no other therapy has been shown to influence the course of the disease. It has been suggested that adding nebulised hypertonic saline to usual care may shorten the duration of hospitalisation. To determine whether hypertonic saline does have beneficial effects we undertook an open, multi-centre parallel-group, pragmatic RCT in ten UK hospitals.

Methods

Infants admitted to hospital with a clinical diagnosis of acute bronchiolitis and requiring oxygen therapy were randomised to receive usual care alone or nebulised 3% hypertonic saline (HS) administered 6-hourly. Randomisation was within 4 h of admission. The primary outcome was time to being assessed as ‘fit’ for discharge with secondary outcomes including time to discharge, incidence of adverse events together with follow up to 28 days assessing patient centred health related outcomes.

Results

A total of 317 infants were recruited to the study. 158 infants were randomised to HS (141 analysed) and 159 to standard care (149 analysed). There was no difference between the two arms in time to being declared fit for discharge (hazard ratio: 0−95, 95% CI: 0.75−1.20) nor to actual discharge (hazard ratio: 0.97, 95% CI: 0.76−1.23). There was no difference in adverse events. One infant in the HS group developed bradycardia with desaturation.

Conclusion

This study does not support the use of nebulised HS in the treatment of acute bronchiolitis over usual care with minimal handlings.

ClinicalTrials.gov registration number

NCT01469845.

Adjuvant effect of the human metapneumovirus (HMPV) matrix protein in HMPV subunit vaccines

The human metapneumovirus (HMPV) fusion (F) protein is the most immunodominant protein, yet subunit vaccines containing only this protein do not confer complete protection. The HMPV matrix (M) protein induces the maturation of antigen-presenting cells in vitro. The inclusion of the M protein into an F protein subunit vaccine might therefore provide an adjuvant effect. We administered the F protein twice intramuscularly, adjuvanted with alum, the M protein or both, to BALB/c mice at 3 week intervals. Three weeks after the boost, mice were infected with HMPV and monitored for 14 days. At day 5 post-challenge, pulmonary viral titres, histopathology and cytokine levels were analysed. Mice immunized with F+alum and F+M+alum generated significantly more neutralizing antibodies than mice immunized with F only [titres of 47 ± 7 (P<0.01) and 147 ± 13 (P<0.001) versus 17 ± 2]. Unlike F only [1.6 ± 0.5 × 10(3) TCID50 (g lung)(-1)], pulmonary viral titres in mice immunized with F+M and F+M+alum were undetectable. Mice immunized with F+M presented the most important reduction in pulmonary inflammation and the lowest T-helper Th2/Th1 cytokine ratio. In conclusion, addition of the HMPV-M protein to an F protein-based vaccine modulated both humoral and cellular immune responses to subsequent infection, thereby increasing the protection conferred by the vaccine.

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.

Structural and biochemical insights into the V/I505T mutation found in the EIAV gp45 vaccine strain

BACKGROUND

The equine infectious anemia virus (EIAV) is a lentivirus of the Retrovirus family, which causes persistent infection in horses often characterized by recurrent episodes of high fever. It has a similar morphology and life cycle to the human immunodeficiency virus (HIV). Its transmembrane glycoprotein, gp45 (analogous to gp41 in HIV), mediates membrane fusion during the infection. However, the post-fusion conformation of EIAV gp45 has not yet been determined. EIAV is the first member of the lentiviruses for which an effective vaccine has been successfully developed. The attenuated vaccine strain, FDDV, has been produced from a pathogenic strain by a series of passages in donkey dermal cells. We have previously reported that a V/I505T mutation in gp45, in combination with other mutations in gp90, may potentially contribute to the success of the vaccine strain. To this end, we now report on our structural and biochemical studies of the gp45 protein from both wide type and vaccine strain, providing a valuable structural model for the advancement of the EIAV vaccine.

RESULTS

We resolved crystal structures of the ecto-domain of gp45 from both the wild-type EIAV and the vaccine strain FDDV. We found that the V/I505T mutation in gp45 was located in a highly conserved d position within the heptad repeat, which protruded into a 3-fold symmetry axis within the six-helix bundle. Our crystal structure analyses revealed a shift of a hydrophobic to hydrophilic interaction due to this specific mutation, and further biochemical and virological studies confirmed that the mutation reduced the overall stability of the six-helix bundle in post-fusion conformation. Moreover, we found that altering the temperatures drastically affected the viral infectivity.

CONCLUSIONS

Our high-resolution crystal structures of gp45 exhibited high conservation between the gp45/gp41 structures of lentiviruses. In addition, a hydrophobic to hydrophilic interaction change in the EIAV vaccine strain was found to modulate the stability and thermal-sensitivity of the overall gp45 structure. Our observations suggest that lowering the stability of the six-helix bundle (post-fusion), which may stabilizes the pre-fusion conformation, might be one of the reasons of acquired dominance for FDDV in viral attenuation.

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.

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.