Translational sciences approach to RSV vaccine development

Prevalence, variation, and transmission patterns of human respiratory syncytial virus from pediatric patients in Hubei, China during 2020-2021

Human respiratory syncytial virus (RSV) is a severe threat to children and a main cause of acute lower respiratory tract infections. Nevertheless, the intra-host evolution and inter-regional diffusion of RSV are little known. In this study, we performed a systematic surveillance in hospitalized children in Hubei during 2020-2021, in which 106 RSV-positive samples were detected both clinically and by metagenomic next generation sequencing (mNGS). RSV-A and RSV-B groups co-circulated during surveillance with RSV-B being predominant. About 46 high-quality genomes were used for further analyses. A total of 163 intra-host nucleotide variation (iSNV) sites distributed in 34 samples were detected, and glycoprotein (G) gene was the most enriched gene for iSNVs, with non-synonymous substitutions more than synonymous substitutions. Evolutionary dynamic analysis showed that the evolutionary rates of G and NS2 genes were higher, and the population size of RSV groups changed over time. We also found evidences of inter-regional diffusion from Europe and Oceania to Hubei for RSV-A and RSV-B, respectively. This study highlighted the intra-host and inter-host evolution of RSV, and provided some evidences for understanding the evolution of RSV.

Antibody Responses to Respiratory Syncytial Virus: A Cross-Sectional Serosurveillance Study in the Dutch Population Focusing on Infants Younger Than 2 Years

Background

Respiratory syncytial virus (RSV) generally causes mild disease but can cause severe infections in (premature) infants and elderly adults. Here, we studied RSV-specific antibody concentrations throughout life with emphasis on infants and chronic obstructive pulmonary disease (COPD) patients.

Methods

Sera (N = 2655) from 2 nationwide cross-sectional studies in the Netherlands including individuals aged 0–90 years were analyzed for IgG and IgA antibodies to RSV prefusion F, postfusion F, N, Ga, and Gb proteins and for antibody avidity in 42 COPD patients.

Results

Maternal IgG concentrations declined to age 10–12 months. After the first year of life, approximately 40% of children lacked infection-induced IgA antibodies and may therefore be uninfected. All Dutch children showed serological evidence of RSV infection by age 3 years. Antibody concentrations reached a plateau by age 5–9 years and remains constant throughout life. COPD patients had similar levels and avidity of RSV-specific IgG antibodies compared with age-matched healthy controls.

Conclusions

RSV-IgG antibody patterns throughout life can be used to estimate the degree of immunity acquisition to RSV and to identify groups at increased risk of infection. Seroprevalence of IgA could be a proxy to determine RSV infection in children younger than 1 year.

Modified mRNA/lipid nanoparticle-based vaccines expressing respiratory syncytial virus F protein variants are immunogenic and protective in rodent models of RSV infection

The RSV Fusion (F) protein is a target for neutralizing antibody responses and is a focus for vaccine discovery; however, the process of RSV entry requires F to adopt a metastable prefusion form and transition to a more stable postfusion form, which displays less potent neutralizing epitopes. mRNA vaccines encode antigens that are translated by host cells following vaccination, which may allow conformational transitions similar to those observed during natural infection to occur. Here we evaluate a panel of chemically modified mRNA vaccines expressing different forms of the RSV F protein, including secreted, membrane associated, prefusion-stabilized, and non-stabilized structures, for conformation, immunogenicity, protection, and safety in rodent models. Vaccination with mRNA encoding native RSV F elicited antibody responses to both prefusion- and postfusion-specific epitopes, suggesting that this antigen may adopt both conformations in vivo. Incorporating prefusion stabilizing mutations further shifts the immune response toward prefusion-specific epitopes, but does not impact neutralizing antibody titer. mRNA vaccine candidates expressing either prefusion stabilized or native forms of RSV F protein elicit robust neutralizing antibody responses in both mice and cotton rats, similar to levels observed with a comparable dose of adjuvanted prefusion stabilized RSV F protein. In contrast to the protein subunit vaccine, mRNA-based vaccines elicited robust CD4+ and CD8+ T-cell responses in mice, highlighting a potential advantage of the technology for vaccines requiring a cellular immune response for efficacy.

Adenovectors encoding RSV-F protein induce durable and mucosal immunity in macaques after two intramuscular administrations

Respiratory Syncytial Virus (RSV) can cause severe respiratory disease, yet a licensed vaccine is not available. We determined the immunogenicity of two homologous and one heterologous intramuscular prime-boost vaccination regimens using replication-incompetent adenoviral vectors of human serotype 26 and 35 (Ad26 and Ad35), expressing a prototype antigen based on the wild-type fusion (F) protein of RSV strain A2 in adult, RSV-naive cynomolgus macaques. All regimens induced substantial, boostable antibody responses that recognized the F protein in pre- and postfusion conformation, neutralized multiple strains of RSV, and persisted for at least 80 weeks. Vaccination induced durable systemic RSV-F-specific T-cell responses characterized mainly by CD4+ T cells expressing Th1-type cytokines, as well as RSV-F-specific CD4+ and CD8+ T cells, IgG, and IgA in the respiratory tract. Intramuscular immunization with Ad26 and 35 vectors thus is a promising approach for the development of an optimized RSV vaccine expected to induce long-lasting humoral and cellular immune responses that distribute systemically and to mucosal sites.

Development and Standardization of a High-Throughput Multiplex Immunoassay for the Simultaneous Quantification of Specific Antibodies to Five Respiratory Syncytial Virus Proteins

In view of vaccine and monoclonal development to reduce hospitalization and death due to lower respiratory tract infection caused by RSV, assessment of antibody levels against RSV is essential. This newly developed multiplex immunoassay is able to measure antibody levels against five RSV proteins simultaneously. This can provide valuable insight into the dynamics of (maternal) antibody levels and RSV infection in infants and toddlers during the first few years of life, when primary RSV infection occurs.

Human respiratory syncytial virus (RSV) is a major cause of severe respiratory disease in (premature) newborns and causes respiratory illness in the elderly. Different monoclonal antibody (MAb) and vaccine candidates are in development worldwide and will hopefully become available within the near future. To implement such RSV vaccines, adequate decisions about immunization schedules and the different target group(s) need to be made, for which the assessment of antibody levels against RSV is essential. To survey RSV antigen-specific antibody levels, we developed a serological multiplex immunoassay (MIA) that determines and distinguishes antibodies against the five RSV glycoproteins postfusion F, prefusion F, Ga, Gb, and N simultaneously. The standardized RSV pentaplex MIA is sensitive, highly reproducible, and specific for the five RSV proteins. The preservation of the conformational structure of the immunodominant site Ø of prefusion F after conjugation to the beads has been confirmed. Importantly, good correlation is obtained between the microneutralization test and the MIA for all five proteins, resulting in an arbitrarily chosen cutoff value of prefusion F antibody levels for seropositivity in the microneutralization assay. The wide dynamic range requiring only two serum sample dilutions makes the RSV-MIA a high-throughput assay very suitable for (large-scale) serosurveillance and vaccine clinical studies.

IMPORTANCE In view of vaccine and monoclonal development to reduce hospitalization and death due to lower respiratory tract infection caused by RSV, assessment of antibody levels against RSV is essential. This newly developed multiplex immunoassay is able to measure antibody levels against five RSV proteins simultaneously. This can provide valuable insight into the dynamics of (maternal) antibody levels and RSV infection in infants and toddlers during the first few years of life, when primary RSV infection occurs.

Baseline immune profile by CyTOF can predict response to an investigational adjuvanted vaccine in elderly adults

Background

Mass cytometry, or CyTOF (Cytometry by Time-of-Flight), permits the simultaneous detection of over 40 phenotypic and functional immune markers in individual cells without the issues of spectral overlap seen in traditional flow cytometry.

Methods

In this study, we applied CyTOF to comprehensively characterize the circulating immune cell populations in elderly individuals both before and after administration of an investigational adjuvanted protein vaccine against respiratory syncytial virus (RSV) in a Phase 1a trial. Antigen-specific T cell responses to RSV by IFNγ ELISPOT had been observed in most but not all recipients in the highest dose cohort in this trial. Here, CyTOF was used to characterize the cellular response profile of ELISPOT responders and non-responders in this vaccine dose cohort.

Results

Both CD4⁺ and CD8⁺ T cell antigen-specific IFNγ responses were observed. Principal components analysis revealed baseline differences between responders and non-responders, including differences in activated (HLA-DR⁺) CD4⁺ and CD8⁺ T cells, which were higher in non-responders versus responders. Using viSNE to analyze RSV-responsive CD4⁺ and CD8⁺ T cells, we also found increased expression of HLA-DR, CCR7, CD127 and CD69 in non-responders versus responders.

Conclusions

High parameter CyTOF can help profile immune components associated with differential vaccine responsiveness.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1528-1) contains supplementary material, which is available to authorized users.

Inferior immunogenicity and efficacy of respiratory syncytial virus fusion protein-based subunit vaccine candidates in aged versus young mice

Respiratory syncytial virus (RSV) is recognized as an important cause of lower and upper respiratory tract infections in older adults, and a successful vaccine would substantially lower morbidity and mortality in this age group. Recently, two vaccine candidates based on soluble purified glycoprotein F (RSV F), either alone or adjuvanted with glucopyranosyl lipid A formulated in a stable emulsion (GLA-SE), failed to reach their primary endpoints in clinical efficacy studies, despite demonstrating the desired immunogenicity profile and efficacy in young rodent models. Here, one of the RSV F vaccine candidates (post-fusion conformation, RSV post-F), and a stabilized pre-fusion form of RSV F (RSV pre-F, DS-Cav1) were evaluated in aged BALB/c mice. Humoral and cellular immunogenicity elicited after immunization of naïve, aged mice was generally lower compared to young animals. In aged mice, RSV post-F vaccination without adjuvant poorly protected the respiratory tract from virus replication, and addition of GLA-SE only improved protection in the lungs, but not in nasal turbinates. RSV pre-F induced higher neutralizing antibody titers compared to RSV post-F (as previously reported) but interestingly, RSV F-specific CD8 T cell responses were lower compared to RSV post-F responses regardless of age. The vaccines were also tested in RSV seropositive aged mice, in which both antigen forms similarly boosted neutralizing antibody titers, although GLA-SE addition boosted neutralizing activity only in RSV pre-F immunized animals. Cell-mediated immune responses in the aged mice were only slightly boosted and well below levels induced in seronegative young mice. Taken together, the findings suggest that the vaccine candidates were not able to induce a strong anti-RSV immune response in recipient mice with an aged immune system, in agreement with recent human clinical trial results. Therefore, the aged mouse model could be a useful tool to evaluate improved vaccine candidates, targeted to prevent RSV disease in older adults.

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.

Estimating the hospitalization burden associated with influenza and respiratory syncytial virus in New York City, 2003-2011

Background

Hospitalization burden associated with influenza and respiratory syncytial virus (RSV) is uncertain due to ambiguity in the inference methodologies employed for its estimation.

Objectives

Utilization of a new method to quantitate the above burden.

Methods

Weekly hospitalization rates for several principal diagnoses from 2003 to 2011 in New York City by age group were regressed linearly against incidence proxies for the major influenza subtypes and RSV adjusting for temporal trends and seasonal baselines.

Results

Average annual rates of influenza-associated respiratory hospitalizations per 100 000 were estimated to be 129 [95% CI (79, 179)] for age <1, 36·3 (21·6, 51·4) for ages 1–4, 10·6 (7·5, 13·7) for ages 5–17, 25·6 (21·3, 29·8) for ages 18–49, 65·5 (54·0, 76·9) for ages 50–64, 125 (105, 147) for ages 65–74, and 288 (244, 331) for ages ≥75. Additionally, influenza had a significant contribution to hospitalization rates with a principal diagnosis of septicemia for ages 5–17 [0·76 (0·1, 1·4)], 18–49 [1·02 (0·3, 1·7)], 50–64 [4·0 (1·7, 6·3)], 65–74 [8·8 (2·2, 15·6)], and ≥75 [38·7 (25·7, 52·9)]. RSV had a significant contribution to the rates of respiratory hospitalizations for age <1 [1900 (1740, 2060)], ages 1–4 [117 (70, 167)], and ≥75 [175 (44, 312)] [including chronic lower respiratory disease, 90 (43, 140)] as well as pneumonia & influenza hospitalizations for ages 18–49 [6·2 (1·1, 11·3)] and circulatory hospitalizations for ages ≥75 [199 (13, 375)].

Conclusions

The high burden of RSV hospitalizations among young children and seniors age ≥75 suggests the need for additional control measures such as vaccination to mitigate the impact of annual RSV epidemics. Our estimates for influenza-associated hospitalizations provide further evidence of the burden of morbidity associated with influenza, supporting current guidelines regarding influenza vaccination and antiviral treatment.

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

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

Prevention and prophylaxis of respiratory syncytial virus in pediatric cardiology: a UK perspective

ABSTRACT: 

Respiratory syncytial virus (RSV) is a common infection, causing bronchiolitis in over 70% of infants each year and almost all children by the age of 2. It is the leading cause of acute lower respiratory tract infections and admissions to hospital worldwide. Previously healthy infants may have a prolonged cough or wheezing following RSV infection but up to 20% of those with congenital cardiac disease will be hospitalized and have significant morbidity and mortality. For this reason, it is generally recommended that many such infants should receive prophylaxis against RSV infection with palivizumab. This paper reviews the current state of knowledge about RSV affecting children with congenital heart disease from the perspective of those living in the UK and the current protection offered to such children. We also discuss the plans for the future of protection against RSV.

Enzyme-linked immunospot assay for detection of human respiratory syncytial virus f protein-specific gamma interferon-producing T cells

Respiratory syncytial virus (RSV) causes significant disease in elderly adults, and we have previously reported that individuals 65 years of age and older have reduced RSV F protein-specific gamma interferon (IFN-γ)-producing T cells compared to healthy younger adults. To measure RSV F-specific memory T cell responses in the elderly following infection or vaccination, we optimized and qualified an IFN-γ enzyme-linked immunospot (ELISPOT) assay. Since peripheral blood mononuclear cells (PBMC) from the elderly could be more fragile, we established optimal cryopreservation techniques and minimal viability acceptance criteria. The number of cells per well, types and concentrations of stimulation antigens, and incubation times were evaluated to maximize assay sensitivity and precision. The optimized assay uses 300,000 cells/well, 2 μg/ml of an RSV F peptide pool (RSV Fpp), and incubation for 22 ± 2 h in serum-free CTL-Test medium. The assay was qualified by 3 analysts using 3 RSV F-responding donor PBMC samples (high, medium, and low responders) tested on 5 different assay days. The assay sensitivity or limit of detection (LOD) was determined to be 21 spot-forming cells (SFC) per 10(6) PBMC, and the lower limit of quantitation (LLOQ) was estimated to be 63 SFC/10(6) PBMC. The intra- and interassay percent coefficients of variation (CV) were <10.5% and <31%, respectively. The results of the qualification study demonstrate that a robust, precise, and sensitive IFN-γ ELISPOT assay has been developed that is fit for measuring RSV F-specific IFN-γ T cell responses in subjects enrolled in a vaccine clinical trial or in epidemiology studies.