RSV-neutralizing Antibody Research Articles

Immunogenicity and safety of Ad26.RSV.preF/RSV preF protein vaccine at predicted intermediate- and end-of-shelf-life as an evaluation of potency throughout shelf life

ABSTRACT This study assessed three Ad26.RSV.preF/RSV preF protein combinations, combining different Ad26.RSV.preF doses and naturally aged preF protein, representing the expected critical vaccine quality attributes close to release, around intermediate shelf-life (ISL) and near-presumed end-of-shelf-life (EoSL), as a way to evaluate the vaccine immunogenicity and safety throughout its shelf-life. A single dose of Ad26.RSV.preF/RSV preF protein vaccine was administered to adults 60–75 years of age. Solicited adverse events (AEs), unsolicited AEs, and serious AEs (SAEs) were assessed for 7-day, 28-day, and 6-month periods after vaccination, respectively. RSV preF-binding antibody concentrations and RSV neutralizing titers were measured 14 days post-vaccination as primary and secondary endpoints, respectively; binding antibodies were also measured 6 months post-vaccination. The RSV preF-binding antibody responses induced by Ad26.RSV.preF/RSV preF protein vaccine lots representing the critical quality attributes around ISL and near presumed EoSL were noninferior to the responses induced by the vaccine lot representing the critical quality attributes near release. The RSV preF-binding and RSV neutralizing antibody levels measured 14 days post-vaccination were similar across the 3 groups. RSV preF-binding antibody concentrations were also similar 6 months post-vaccination. Solicited AEs were mostly mild to moderate in intensity, and a decreased reactogenicity was observed from the Release group to the ISL and EoSL group. None of the reported SAEs were considered related to study vaccination. The study provided evidence of sustained immunogenicity and safety over the intended shelf-life of the Ad26.RSV.pref/RSV preF protein vaccine. The three vaccine lots had acceptable safety profiles.

Respiratory syncytial virus immunoprophylaxis: Novel opportunities and a call for equity.

With the approval of the first vaccines against respiratory syncytial virus (RSV) and a novel RSV-neutralizing antibody, 2023 has been perceived as a game-changing year in preventing severe outcomes of RSV infections in infants and the elderly. However, the costs of these pharmaceuticals are high, while RSV disproportionately impacts populations of low-to-middle-income regions, which may continue to suffer from a lack of pharmaceutical measures for RSV prevention under health and socioeconomic disparities. This paper presents an overview of the characteristics, clinical results, and approval status of various RSV vaccines and anti-RSV antibodies. It posits that wealthy nations cannot monopolize RSV immunoprophylaxis and should work jointly to make it available to lower-income countries. An approach toward RSV immunoprophylaxis equity based on five points is offered: (1) integration of RSV vaccines and antibodies into the existing global humanitarian distribution systems, (2) using affordable RSV vaccine pricing models, (3) enforcing equity as a part of national and global public health strategy, (4) implementing equitable allocation frameworks for RSV immunoprophylaxis, and (5) promoting local manufacturing. Such a plan needs to be put into action as soon as possible to avoid delays in serving the populations with the highest needs related to RSV burden.

Clinical, Genomic, and Immunological Characterization of RSV Surge in Sydney, Australia, 2022.

The 2022 seasonal respiratory syncytial virus (RSV) epidemic in Sydney, Australia saw an unprecedented number of RSV detections. We aimed to characterize genomic and immunologic factors associated with the surge in RSV cases. Whole genome sequences of RSV were generated from 264 RSV-infected infants and linked to case-matched clinical data from the 2022 southern hemisphere RSV season. We then performed an immunologic analysis of baseline RSV-specific humoral immunity in women of childbearing age before and throughout the coronavirus disease 2019 pandemic. Clinical analysis revealed a high burden of disease across patients of all health backgrounds. More than one-half of RSV-related health care visits by infants resulted in hospitalization, and one-quarter required high-flow respiratory support or a higher level of care. Viral phylogenetic analyses revealed that 2022 Sydney RSV sequences were closely related to viruses that had been circulating globally since 2017, including those detected in recent US outbreaks. Nonsynonymous mutations within the palivizumab and nirsevimab binding sites were detected at low frequencies. There was no difference in baseline RSV-neutralizing antibody titers between 2020 and 2022. Collectively, these findings suggest that neither the emergence of a novel RSV genotype nor hypothesized immune debt was associated with the surge of RSV cases and hospitalizations in 2022. Continued genomic and immunologic surveillance is required to further understand the factors driving outbreaks of RSV globally, and to inform guidelines for the rollout and ongoing use of recently developed immunotherapeutics and vaccines.

2655. Phase 1 Safety and Immunogenicity Results of Two Investigational mRNA Vaccines, mRNA-1345, a Respiratory Syncytial Virus Vaccine, and mRNA-1653, a Human Metapneumovirus and Parainfluenza Virus Type 3 Combination Vaccine in Seropositive Young Children

Abstract Background Respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and parainfluenza virus type 3 (PIV3) are common respiratory illnesses in children. Two investigational vaccines, mRNA-1345, encoding the RSV prefusion stabilized F (preF) glycoprotein, and mRNA-1653, encoding the hMPV and PIV3 F glycoproteins, are in clinical trials. Methods Two phase 1, randomized, observer-blind, placebo-controlled trials in children aged 12-59 months assessed safety and immunogenicity of mRNA-1345 (NCT04528719) and mRNA-1653 (NCT04144348). In the mRNA-1345 trial, RSV-seropositive children (N=46) were randomized to receive 3 doses of mRNA-1345 (15 µg or 30 µg) or placebo 2 months apart. In the mRNA-1653 trial, hMPV- and PIV3-seropositive children (N=27) were randomized to receive 2 doses of mRNA-1653 (10 µg or 30 µg) or placebo 2 months apart. Interim data through Month (M) 5 for mRNA-1345 and M3 for mRNA-1653 are reported. Results mRNA-1345 and mRNA-1653 were well-tolerated. The most frequently reported solicited local adverse reaction (AR) was tenderness at injection site (mRNA-1345, 35.7%-71.4%; placebo, 26.7%-42.9% and mRNA-1653, 44.4%-60.0%; placebo, 12.5%-30.0%); solicited systemic ARs (mRNA-1345, 12.5%-53.3%; placebo, 33.3%-50.0% and mRNA-1653, 33.3%-55.6%; placebo, 12.5%-60.0%) were mostly grade 1/2. One mRNA-1345 injection boosted RSV neutralizing antibody (nAb) titers (geometric mean fold rise [GMFR] over baseline: RSV-A=18.9-34.9; RSV-B=7.2-14.3) and RSV preF and postF binding antibody (bAb) concentrations (GMFR: preF=13.9-26.5; postF=9.3-16.0); additional injections did not further elevate antibody levels (Fig 1A and 2A). One mRNA-1653 injection boosted hMPV and PIV3 nAb titers (GMFR over baseline: hMPV-A=2.9-6.1; hMPV-B=6.2-13.2; PIV3=2.8-3.0) and preF and postF bAb concentrations (GMFR: hMPV preF=5.3-6.1; postF=4.6-6.5 and PIV3 preF=13.9-14.2; postF=11.0-12.1); a second injection did not further increase antibody levels (Fig 1B,C and 2B,C). In both trials, bAb responses were generally preF biased. Conclusion In seropositive children aged 12-59 months, mRNA-1345 and mRNA-1653 were well-tolerated and boosted RSV and hMPV plus PIV3 antibodies, respectively, supporting their continued development and that of a combination RSV and hMPV vaccine. Disclosures Matthew D. Snape, MBBS, MD, FRCPCH, FPM, FMedSci, Moderna Biotech UK, Inc.,: Employee|Moderna Biotech UK, Inc.,: Stocks/Bonds Sabine Schnyder Ghamloush, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Grace L. Chen, MD, MPH, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Rakesh Dhar, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Runa Mithani, PharmD, Moderna, Inc: Employee|Moderna, Inc: Stocks/Bonds Vinicius Righi, PharmD, MBA, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Louie Morsy, BS, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Archana Kapoor, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Bethany Girard, Ph.D., Moderna, Inc.: salary|Moderna, Inc.: Stocks/Bonds Laila El Asmar, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Christine A. Shaw, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds

Immunogenicity of an AS01-adjuvanted respiratory syncytial virus prefusion F (RSVPreF3) vaccine in animal models

Respiratory syncytial virus (RSV) causes a high disease burden in older adults. An effective vaccine for this RSV-primed population may need to boost/elicit robust RSV-neutralizing antibody responses and recall/induce RSV-specific T cell responses. To inform the selection of the vaccine formulation for older adults, RSVPreF3 (RSV fusion glycoprotein engineered to maintain the prefusion conformation) with/without AS01 adjuvant was evaluated in mice and bovine RSV infection-primed cattle. In mice, RSVPreF3/AS01 elicited robust RSV-A/B-specific neutralization titers and RSV F-specific polyfunctional CD4+ T cell responses exceeding those induced by non-adjuvanted RSVPreF3. In primed bovines, RSVPreF3/AS01 tended to induce higher pre-/post-vaccination fold-increases in RSV-A/B-specific neutralization titers relative to non-adjuvanted and Alum-adjuvanted RSVPreF3 formulations, and elicited higher RSV F-specific CD4+ T cell frequencies relative to the non-adjuvanted vaccine. Though AS01 adjuvanticity varied by animal species and priming status, RSVPreF3/AS01 elicited/boosted RSV-A/B-specific neutralization titers and RSV F-specific CD4+ T cell responses in both animal models, which supported its further clinical evaluation as prophylactic candidate vaccine for older adults.

In-vivo and human evidence for potential efficacy of therapeutic polyclonal RSV neutralizing antibodies for palivizumab-resistant RSV infections

BackgroundMonoclonal antibody (palivizumab), intravenous immune globulin (IGIV), or respiratory syncytial virus (RSV)-polyclonal-hyperimmune-globulin (RSV-IG as Respigam®, RI-001, RI-002) are used with ribavirin in RSV-infected immunocompromised patients, with debated efficacy. Palivizumab-resistance (PR) can arise during treatment of persistent infections in this population. RSV-IG may confer benefit in PR-RSV infection. MethodsRSV-IG [RI-001] was provided for an immunocompromised infant with RSV-pneumonitis refractory to ribavirin and palivizumab. RSV-neutralizing antibody, respiratory RSV load (qPCR), and F-gene-sequence-detection of PR was determined. Prophylactic RSV-IG [RI-002] or palivizumab was administered in a cotton-rat model infected with wild-type and PR-RSV. Lung RSV load and neutralizing antibody were measured. ResultsAs protective RI-001-neutralizing antibody titers waned in the infant, a subpopulation of PR-escape mutants were detected with a fatal RSV-burden in the lungs. In PR-RSV-infected cotton rats, prophylactic RI-002 reduced RSV-load in the lungs (2.45 vs 0.28 log10 PFU/g lung-tissue reduction, respectively, p < 0.05) and provided protective RSV-neutralizing antibody. ConclusionsRSV-IG and ribavirin use in immunocompromised patients requires further study.

Double-Blind, Placebo-Controlled, Dose-Escalating Study Evaluating the Safety and Immunogenicity of an Epitope-Specific Chemically Defined Nanoparticle RSV Vaccine.

V-306 is a virus-like particle-based vaccine candidate displaying respiratory syncytial virus (RSV) F site II protein mimetics (FsIIm) as an antigenic epitope. This was a randomized, placebo-controlled, double-blind, dose-escalating, first-in-human study, conducted in 60 women aged 18-45 years. Twenty subjects per cohort (15 vaccine and five placebo) received two V-306 intramuscular administrations on Days 0 and 56 at 15 µg, 50 µg, or 150 µg. Safety and immunogenicity were assessed after each vaccination and for 1 year in total. V-306 was safe and well tolerated at all dose levels, with no increase in reactogenicity and unsolicited adverse events between the first and second administrations. At 50 µg and 150 µg, V-306 induced an increase in FsIIm-specific immunoglobulin G (IgG) titers, which lasted at least 4 months. This did not translate into an increase in RSV-neutralizing antibody titers, which were already high at baseline. No increase in the anti-F protein-specific IgG titers was observed, which were also high in most subjects at baseline due to past natural infections. V-306 was safe and well-tolerated. Future modifications of the vaccine and assay conditions will likely improve the results of vaccination.

Bioluminescence Goes Dark: Boosting the Performance of Bioluminescent Sensor Proteins Using Complementation Inhibitors.

Bioluminescent sensor proteins have recently gained popularity in both basic research and point-of-care diagnostics. Sensor proteins based on intramolecular complementation of split NanoLuc are particularly attractive because their intrinsic modular design enables for systematic tuning of sensor properties. Here we show how the sensitivity of these sensors can be enhanced by the introduction of catalytically inactive variants of the small SmBiT subunit (DarkBiTs) as intramolecular inhibitors. Starting from previously developed bioluminescent antibody sensor proteins (LUMABS), we developed single component, biomolecular switches with a strongly reduced background signal for the detection of three clinically relevant antibodies, anti-HIV1-p17, cetuximab (CTX), and an RSV neutralizing antibody (101F). These new dark-LUMABS sensors showed 5-13-fold increases in sensitivity which translated into lower limits of detection. The use of DarkBiTs as competitive intramolecular inhibitor domains is not limited to the LUMABS sensor family and might be used to boost the performance of other bioluminescent sensor proteins based on split luciferase complementation.

Live-Attenuated Vaccines Prevent Respiratory Syncytial Virus-Associated Illness in Young Children

To determine the preliminary efficacy and durability of live-attenuated respiratory syncytial virus RSV vaccine candidates from phase 1 clinical trials.Healthy RSV-naïve children aged 6 to 24 months (n = 241) were randomly assigned 2:1 to receive either a live-attenuated RSV vaccine or placebo.Separate trials of 7 different RSV vaccine candidates were similarly conducted, and data were pooled for analysis. The surveillance period was from ∼5.5 to 13 months after day 56 postvaccination. The RSV neutralizing antibody (NeutAb) response, also considered indicative of vaccine efficacy, was defined as more than a fourfold increase in complement-enhanced plaque reduction-neutralizing antibody titers after vaccination. Data were further grouped by “more promising” vaccines (NeutAb response in ≥80% of vaccine recipients; n = 5) and “less promising” (NeutAb response in ≤59% of vaccines; n = 2).There was 66% efficacy against respiratory syncytial virus–associated medically attended acute respiratory illness (RSV-MAARI) infections (P = .007) and 100% efficacy against respiratory syncytial virus–associated medically attended acute lower respiratory illness (RSV-MAALRI) (P = .009) among all NeutAb responders. A NeutAb response overall was significantly associated with protection against RSV-MAARI and RSV-MAALRI (odds ratio: 0.26; 95% confidence interval: 0.09 to 0.75; P = .014). Vaccine virus titers shed by vaccine recipients did not correlate with protection against RSV-MAARI or RSV-MAALRI. Although there was no significant difference in the primary NeutAb responses between the vaccinated and placebo groups (P = .21), the magnitude of anamnestic NeutAb response was ∼10-fold higher in vaccine recipients than in those with the placebo after infection with wild-type RSV during surveillance (P = .0001). In the vaccinated group not infected with wild-type RSV (n = 89), the postsurveillance anamnestic NeutAb titers (79 [6.3 log2]) were less than postimmunization (111 [6.8 log2]; P < .001); however, the absolute difference was small. On the basis of the disease rate model, the authors determined that future study sample sizes between 540 and 1300 would be needed to demonstrate efficacy.Live-attenuated RSV vaccines provide protection against acute respiratory and lower respiratory illnesses and can produce durable response.Currently, palivizumab, a monoclonal antibody, is still the only Food and Drug Administration–approved medication for RSV, providing short-term prophylaxis against severe RSV disease in high-risk infants and children with preexisting conditions, such as prematurity with or without bronchopulmonary dysplasia. The preliminary data from these small clinical trials identifying these “more promising” vaccines suggest that we may be 1 step closer toward actually developing an RSV vaccine that can protect against infection and address the burden of RSV disease. Obvious considerations for future and later stage clinical trials include appropriately powered sample sizes (including RSV-exposed subjects), study duration, geographic locations, timing of the RSV season, and vaccine delivery routes and dosing.

2775. Safety and Immunogenicity of a Seasonal Influenza Vaccine and Ad26.RSV.preF Vaccine With and Without Co-Administration: A Randomized, Double-Blind, Placebo-Controlled Phase 2a Study in Adults Aged ≥ 60 Years

BackgroundInfluenza and RSV can cause respiratory tract infections leading to severe illness, hospitalization and mortality in at-risk populations, particularly the elderly. The seasonality of influenza and RSV present the potential to co-administer vaccines. This study aimed to demonstrate the non-inferiority of co-administration of the experimental RSV vaccine Ad26.RSV.preF with an influenza vaccine (Fluarix) vs. Fluarix alone in terms of immunogenicity against influenza.MethodsThis was a single-center, randomized, double-blind, placebo-controlled Phase 2a study (NCT03339713) in healthy adults ≥60 years old. Volunteers were randomized 1:1 to receive Fluarix + 1 × 1011 vp Ad26.RSV.preF on Day 1 and placebo on Day 29 (Group 1), or Fluarix + placebo on Day 1 and 1 × 1011 vp Ad26.RSV.preF on Day 29 (Group 2). Blood samples were taken prior to each vaccination and at Day 57. The primary endpoints were geometric mean titers (GMTs) of hemagglutination inhibition (HI) antibody titers against Fluarix strains (A/Michigan, A/Hong Kong, B/Brisbane and B/Phuket) and the safety and tolerability of Ad26.RSV.preF administered with or without Fluarix. A key secondary endpoint was neutralizing antibody titers to RSV A2.ResultsVolunteers (N = 180) were included in Group 1 (n = 90) or Group 2 (n = 90). Most volunteers were white (89%) and female (63%), with a median age of 65 years. Both groups exhibited an increase from baseline in HI antibody response on Day 29. The 95% one-sided upper confidence limit of all GMT ratios were below the non-inferiority margin of 2. The frequency of solicited adverse events (AE) after Ad26.RSV.preF vaccination was similar with and without influenza co-administration. Solicited AEs were mainly of Grade 1 and 2 and of transient duration. Most unsolicited AEs were considered unrelated to the study vaccination and were Grade 1 or 2. There were no serious AEs related to the study vaccine and there were no discontinuations due to AEs. RSV neutralizing antibody titers 29 days post- Ad26.RSV.preF immunization were similar in both groups (1404, Group 1; 1690, Group 2).ConclusionCo-administration of Ad26.RSV.preF with Fluarix was non-inferior to Fluarix alone in terms of immunogenicity against influenza and had an acceptable tolerability profile.Disclosures All authors: No reported disclosures.

Adjuvants and the vaccine response to the DS-Cav1-stabilized fusion glycoprotein of respiratory syncytial virus.

Appropriate adjuvant selection may be essential to optimize the potency and to tailor the immune response of subunit vaccines. To induce protective responses against respiratory syncytial virus (RSV)—a highly prevalent childhood pathogen without a licensed vaccine—we previously engineered a pre-fusion-stabilized trimeric RSV F (pre-F) “DS-Cav1” immunogen, which induced high titer RSV-neutralizing antibodies, in mice and non-human primates, when formulated with adjuvants Poly (I:C) and Poly (IC:LC), respectively. To assess the impact of different adjuvants, here we formulated RSV F DS-Cav1 with multiple adjuvants and assessed immune responses. Very high RSV-neutralizing antibody responses (19,006 EC50) were observed in naïve mice immunized with 2 doses of DS-Cav1 adjuvanted with Sigma adjuvant system (SAS), an oil-in-water adjuvant, plus Carbopol; high responses (3658–7108) were observed with DS-Cav1 adjuvanted with Alum, SAS alone, Adjuplex, Poly (I:C) and Poly (IC:LC); and moderate responses (1251–2129) were observed with DS-Cav1 adjuvanted with the TLR4 agonist MPLA, Alum plus MPLA or AddaVax. In contrast, DS-Cav1 without adjuvant induced low-level responses (6). A balanced IgG1 and IgG2a (Th2/Th1) immune response was elicited in most of the high to very high response groups (all but Alum and Adjuplex). We also tested the immune response induced by DS-Cav1 in elderly mice with pre-existing DS-Cav1 immunity; we observed that DS-Cav1 adjuvanted with SAS plus Carbopol boosted the response 2-3-fold, whereas DS-Cav1 adjuvanted with alum boosted the response 5-fold. Finally, we tested whether a mixture of ISA 71 VG and Carbopol would enhanced the antibody response in DS-Cav1 immunized calves. While pre-F-stabilized bovine RSV F induced very high titers in mice when adjuvanted with SAS plus Carbopol, the addition of Carbopol to ISA 71 VG did not enhance immune responses in calves. The vaccine response to pre-F-stabilized RSV F is augmented by adjuvant, but the degree of adjuvant-induced enhancement appears to be both context-dependent and species-specific.

A Single Dose Monoclonal Antibody (mAb) Immunoprophylaxis Strategy to Prevent RSV Disease in All Infants: Results of the First in Infant Study with MEDI8897

BackgroundRSV is the most common cause of lower respiratory tract infection (LRTI) among infants making prevention of RSV disease a public health priority. A significant unmet need exists for RSV prevention in healthy infants. Our goal is to develop a mAb with an extended half-life (t½) capable of protecting infants for an entire RSV season by using a single intramuscular (IM) dose. This study was conducted to evaluate the safety profile, pharmacokinetics (PK), RSV neutralizing antibody titers, and anti-drug antibody (ADA) responses for MEDI8897 in healthy preterm infants born between 32 and 35 weeks gestational age.MethodsInfants were randomized 4:1 to receive a single IM injection of MEDI8897 10mg (n = 8), 25mg (n = 31), 50mg (n = 32) or placebo (n = 18) and followed for 360 days. Enrollment occurred during the 2,015 RSV seasons in the US, South Africa, and Chile. Blood was collected at multiple timepoints. Infants who met criteria for a medically-attended (MA) LRTI had nasal swabs obtained for RSV testing by RT-PCR.ResultsA total of 85/89 (95.5%) infants completed the study. Adverse events (AEs) were reported in 17/18 (94.4%) placebo and 66/71 (93.0%) MEDI8897 recipients. Five serious AEs (three LRTIs, two febrile seizures) were reported in three MEDI8897 recipients. No events were consistent with hypersensitivity reactions. The estimated MEDI8897 serum t½ ranged from 62.5 to 72.9 days. On day 151, 87% of the infants who received the 50mg dose of MEDI8897 had serum concentrations above the target EC90 level of 6.8 µg/ml, and 93.3% showed a ≥3-fold rise from baseline in serum anti-RSV neutralizing antibody titers. ADA was detected in 28.2% of MEDI8897 recipients, but when present was not associated with any safety findings. ADA was detected at day 361 only in 26.5% of subjects. MA-LRTI was reported in 5 (7%) MEDI8897 recipients through 150 days after dosing. The one subject with an MA-LRTI caused by RSV had received a 10mg dose of MEDI8897.ConclusionIn healthy preterm infants, the safety profile of MEDI8897 was favorable. The extended t½ of MEDI8897 with the corresponding increase in RSV neutralizing antibody levels was confirmed and supports protection from RSV disease during a typical 5-month season with a single 50mg IM dose.This study was sponsored by MedImmune.Disclosures J. B. Domachowske, Medimmune: Investigator, Research grant; Regeneron: Investigator, Research grant; Pfizer: Investigator, Research grant; Glaxo Smith Kline: Investigator, Research grant; Novavax: Investigator, Research grant; Janssen: Investigator, Research grant; A. Khan, MedImmune: Employee and Shareholder, Salary and stock; M. T. Esser, MedImmune: Employee and Shareholder, Salary and stock; K. M. Jensen, MedImmune: Employee and Shareholder, Salary and stock; T. Takas, MedImmune: Employee and Shareholder, Salary and stock; T. Villafana, MedImmune: Employee and Shareholder, Salary and stock; F. Dubovsky, MedImmune: Employee and Shareholder, Salary and stock; M. P. Griffin, MedImmune: Employee and Shareholder, Salary and stock

Packaging and Prefusion Stabilization Separately and Additively Increase the Quantity and Quality of Respiratory Syncytial Virus (RSV)-Neutralizing Antibodies Induced by an RSV Fusion Protein Expressed by a Parainfluenza Virus Vector.

Human respiratory syncytial virus (RSV) and human parainfluenza virus type 3 (HPIV3) are major viral agents of acute pediatric bronchiolitis and pneumonia worldwide that lack vaccines. A bivalent intranasal RSV/HPIV3 vaccine candidate consisting of a chimeric bovine/human PIV3 (rB/HPIV3) strain expressing the RSV fusion (F) protein was previously shown to be well tolerated by seronegative children but was insufficiently immunogenic for RSV F. In the present study, the RSV F protein was engineered to be packaged efficiently into vaccine virus particles. This resulted in a significantly enhanced quantity and quality of RSV-neutralizing antibodies in hamsters and nonhuman primates. In nonhuman primates, this effect was strongly additive to the previously described stabilization of the prefusion conformation of the F protein. The improved immunogenicity of RSV F by packaging appeared to involve prefusion stabilization. These findings provide a potently more immunogenic version of this well-tolerated vaccine candidate and should be applicable to other vectored vaccines.

A phase 1a, first-in-human, randomized study of a respiratory syncytial virus F protein vaccine with and without a toll-like receptor-4 agonist and stable emulsion adjuvant

BackgroundRespiratory syncytial virus (RSV) causes significant illness in older adults resulting in substantial health and economic impact. A successful vaccine would reduce morbidity in this growing segment of the population. MethodsIn this double-blind phase 1 study, subjects 60 years of age and older were enrolled by cohort and randomized to receive vaccines containing escalating doses (20, 50, or 80μg) of soluble RSV fusion protein (sF) alone or adjuvanted with 2.5μg of glucopyranosyl lipid A, a toll-like receptor-4 agonist, in 2% stable emulsion (GLA-SE). Each cohort included 20 vaccine and 4 placebo recipients. Immune responses were evaluated using assays for RSV microneutralizing, anti-F IgG, and palivizumab competitive antibodies and for F-specific interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) responses. ResultsThe inclusion of adjuvant increased local reactogenicity, with the majority of subjects who received sF and adjuvant reporting low-grade injection site pain or tenderness. At all doses, the safety profile was acceptable for further development. Immune responses were antigen dose-dependent, and the inclusion of adjuvant increased both humoral and cellular immune responses, with responses statistically higher than for placebo recipients in all 4 assays. At the highest dosage level with adjuvant, half of the subjects had a ≥3-fold rise from day 0 in RSV neutralizing antibody titers, and all had a ≥3-fold rise in antibody levels by anti-F IgG and palivizumab competitive antibody assays on day 29. For the day 8 IFNγ ELISPOT assay, 74% of subjects in the highest dosing cohort had a ≥3-fold rise from baseline. ConclusionsThe safety and immunogenicity results from this study support inclusion of the GLA-SE adjuvant in this RSV vaccine for older adults and also support assessment of the efficacy of the vaccine in a larger clinical trial. Clinicaltrials.gov NCT02115815.

An Epitope‐Specific Respiratory Syncytial Virus Vaccine Based on an Antibody Scaffold

AbstractRespiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in children. We have generated an epitope‐specific RSV vaccine by grafting a neutralizing epitope (F‐epitope) in its native conformation into an immunoglobulin scaffold. The resulting antibody fusion exhibited strong binding affinity to Motavizumab, an RSV neutralizing antibody, and effectively induced potent neutralizing antibodies in mice. This work illustrates the potential of the immunoglobulin molecule as a scaffold to present conformationally constrained B‐cell epitopes.

Maternal transfer of RSV immunity in cotton rats vaccinated during pregnancy

Respiratory Syncytial Virus (RSV) is the leading cause of pneumonia and bronchiolitis in infants, resulting in significant morbidity and mortality worldwide. There is currently no RSV vaccine. Although maternal serum antibodies against RSV are efficiently transferred through placenta protecting human infants from RSV-induced disease, this protection is short-lived and the methods for extending and augmenting protection are not known. The objective of this study was to develop an animal model of maternal RSV vaccination using the Sigmodon hispidus cotton rat. Naïve or RSV-primed female cotton rats were inoculated with live RSV and set in breeding pairs. Antibody transfer to the litters was quantified and the offspring were challenged with RSV at different ages for analysis of protection against viral replication and lung inflammation. There was a strong correlation between RSV-neutralizing antibody (NA) titers in cotton rat mothers and their pups, which also correlated with protection of litters against virus challenge. Passive protection was short-lived and strongly reduced in animals at 4 weeks after birth. Protection of litters was significantly enhanced by inoculating mothers parenterally with live RSV and inversely correlated with the expression of lung cytokines and pathology. Importantly, vaccination and boosting of naïve mothers with the live RSV produced the highest levels of NAs. We conclude that maternal vaccination against RSV in the cotton rat can be used to define vaccine preparations that could improve preexistent immunity and induce subsequent transfer of efficient immunity to infants.

Enhanced Neutralizing Antibody Response Induced by Respiratory Syncytial Virus Prefusion F Protein Expressed by a Vaccine Candidate.

Respiratory syncytial virus (RSV) and human parainfluenza virus type 3 (HPIV3) are the first and second leading viral agents of severe respiratory tract disease in infants and young children worldwide. Vaccines are not available, and an RSV vaccine is particularly needed. A live attenuated chimeric recombinant bovine/human PIV3 (rB/HPIV3) vector expressing the RSV fusion (F) glycoprotein from an added gene has been under development as a bivalent vaccine against RSV and HPIV3. Previous clinical evaluation of this vaccine candidate suggested that increased genetic stability and immunogenicity of the RSV F insert were needed. This was investigated in the present study. RSV F expression was enhanced 5-fold by codon optimization and by modifying the amino acid sequence to be identical to that of an early passage of the original clinical isolate. This conferred a hypofusogenic phenotype that presumably reflects the original isolate. We then compared vectors expressing stabilized prefusion and postfusion versions of RSV F. In a hamster model, prefusion F induced increased quantity and quality of RSV-neutralizing serum antibodies and increased protection against wild-type (wt) RSV challenge. In contrast, a vector expressing the postfusion F was less immunogenic and protective. The genetic stability of the RSV F insert was high and was not affected by enhanced expression or the prefusion or postfusion conformation of RSV F. These studies provide an improved version of the previously well-tolerated rB/HPIV3-RSV F vaccine candidate that induces a superior RSV-neutralizing serum antibody response. Respiratory syncytial virus (RSV) and human parainfluenza virus type 3 (HPIV3) are two major causes of pediatric pneumonia and bronchiolitis. The rB/HPIV3 vector expressing RSV F protein is a candidate bivalent live vaccine against HPIV3 and RSV. Previous clinical evaluation indicated the need to increase the immunogenicity and genetic stability of the RSV F insert. Here, we increased RSV F expression by codon optimization and by modifying the RSV F amino acid sequence to conform to that of an early passage of the original isolate. This resulted in a hypofusogenic phenotype, which likely represents the original phenotype before adaptation to cell culture. We also included stabilized versions of prefusion and postfusion RSV F protein. Prefusion RSV F induced a larger quantity and higher quality of RSV-neutralizing serum antibodies and was highly protective. This provides an improved candidate for further clinical evaluation.

Adults 65 Years Old and Older Have Reduced Numbers of Functional Memory T Cells to Respiratory Syncytial Virus Fusion Protein

Respiratory syncytial virus (RSV) infects elderly (≥65 years) adults, causing medically attended illness and hospitalizations. While RSV neutralizing antibody levels correlate inversely with RSV-associated hospitalization in the elderly, the role of RSV-specific T cells in preventing disease in the elderly remains unclear. We examined RSV-specific humoral, mucosal, and cellular immune profiles in healthy elderly (65 to 85 years) and young (20 to 30 years) adults. RSV neutralization antibody titers in the elderly (10.5 ± 2.2 log(2)) and young (10.5 ± 2.1 log(2)) were similar. In contrast, levels of RSV F protein-specific gamma interferon (IFN-γ)-producing T cells were lower in elderly (180 ± 80 spot-forming cells [SFC]/10(6) peripheral blood mononuclear cells [PBMC]) than in young adults (1,250 ± 420 SFC/10(6) PBMC). Higher levels of interleukin-13 (IL-13; 3,000 ± 1,000 pg/ml) in cultured PBMC supernatants and lower frequency of RSV F-specific CD107a(+) CD8(+) T cells (3.0% ± 1.6% versus 5.0% ± 1.6%) were measured in PBMC from elderly than young adults. These results suggest that deficient RSV F-specific T cell responses contribute to susceptibility to severe RSV disease in elderly adults.

Design and Characterization of Epitope-Scaffold Immunogens That Present the Motavizumab Epitope from Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, but an effective vaccine has not yet been developed. An ideal vaccine would elicit protective antibodies while avoiding virus-specific T-cell responses, which have been implicated in vaccine-enhanced disease with previous RSV vaccines. We propose that heterologous proteins designed to present RSV-neutralizing antibody epitopes and to elicit cognate antibodies have the potential to fulfill these vaccine requirements, as they can be fashioned to be free of viral T-cell epitopes. Here we present the design and characterization of three epitope-scaffolds that present the epitope of motavizumab, a potent neutralizing antibody that binds to a helix–loop–helix motif in the RSV fusion glycoprotein. Two of the epitope-scaffolds could be purified, and one epitope-scaffold based on a Staphylococcus aureus protein A domain bound motavizumab with kinetic and thermodynamic properties consistent with the free epitope-scaffold being stabilized in a conformation that closely resembled the motavizumab-bound state. This epitope-scaffold was well folded as assessed by circular dichroism and isothermal titration calorimetry, and its crystal structure (determined in complex with motavizumab to 1.9 Å resolution) was similar to the computationally designed model, with all hydrogen-bond interactions critical for binding to motavizumab preserved. Immunization of mice with this epitope-scaffold failed to elicit neutralizing antibodies but did elicit sera with F binding activity. The elicitation of F binding antibodies suggests that some of the design criteria for eliciting protective antibodies without virus-specific T-cell responses are being met, but additional optimization of these novel immunogens is required.

Respiratory syncytial virus-neutralizing monoclonal antibodies motavizumab and palivizumab inhibit fusion.

Respiratory syncytial virus (RSV) is a major cause of virus-induced respiratory disease and hospitalization in infants. Palivizumab, an RSV-neutralizing monoclonal antibody, is used clinically to prevent serious RSV-related respiratory disease in high-risk infants. Motavizumab, an affinity-optimized version of palivizumab, was developed to improve protection against RSV. These antibodies bind RSV F protein, which plays a role in virus attachment and mediates fusion. Determining how these antibodies neutralize RSV is important to help guide development of new antibody drugs against RSV and, potentially, other viruses. This study aims to uncover the mechanism(s) by which palivizumab and motavizumab neutralize RSV. Assays were developed to test the effects of these antibodies at distinct steps during RSV replication. Pretreatment of virus with palivizumab or motavizumab did not inhibit virus attachment or the ability of F protein to interact with the target cell membrane. However, pretreatment of virus with either of these antibodies resulted in the absence of detectable viral transcription. These results show that palivizumab and motavizumab act at a point after F protein initiates interaction with the cell membrane and before virus transcription. Palivizumab and motavizumab also inhibited F protein-mediated cell-to-cell fusion. Therefore, these results strongly suggest that these antibodies block both cell-to-cell and virus-to-cell fusion, since these processes are likely similar. Finally, palivizumab and motavizumab did not reduce viral budding. Based on models developed from numerous studies of viral fusion proteins, our results indicate that these antibodies may prevent conformational changes in F protein required for the fusion process.