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The Current State of RSV Vaccine Development
2014 AAAAI Annual Meeting 4304: How Close Are We to Preventing Asthma by Vaccination? San Diego, CA Barney S. Graham, MD, PhD March 3, 2014
Vaccine Research Center National Institute of Allergy and For more information: Infectious Diseases 1-866-833-LIFE National Institutes of Health Department of Health and Human vrc.nih.gov Services [email protected]
Outline
• RSV epidemiology and pathogenesis
• History and challenges for RSV vaccine development
• F glycoprotein function, structure, and antigenic sites
• Vaccine antigen design and immunogenicity
• Considerations for vaccine development
Respiratory Syncytial Virus
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Global RSV Disease Burden
28‐364 days of life Malaria (11.8%)
RSV
Lozano, R et al. The Lancet. 2012; 380:2095‐2128.
RSV kills more children <1 year than any other single pathogen except malaria 4
Outline
• RSV epidemiology and pathogenesis
• History and challenges for RSV vaccine development
• F glycoprotein function, structure, and antigenic sites
• Vaccine antigen design and immunogenicity
• Considerations for vaccine development
RSV Disease Burden and Market Potential
Vaccine market 34 million ALRI globally
3.4 million hospitalizations
• Leading cause of hospitalization in children under 5 years of age • Leading cause of medically attended respiratory infection in children • Cause of excess mortality in elderly similar to seasonal influenza
Passive mAb market
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Challenges for a RSV Vaccine
• Young age of serious disease • Multiple mechanisms to interfere with induction and effector function of Type 1 interferons • Failure of natural immunity to protect against reinfection • Difficult to boost responses in adults • Legacy of vaccine-enhanced disease – Properties to Avoid • Antibodies with poor NT activity → Immune complex deposition • CD4+ Th2-biased response → Allergic inflammation
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FI-RSV Vaccine-Enhanced Disease
Vaccine n Infected (%) Hospitalized (%) Deaths
FI- RSV 31 20 (65) 16 (80) 2
FI-PIV-1 40 21 (53) 1 (5) 0
Kim et al. Am J Epidemiol 1969;89:422 8
Overview of RSV Vaccine Clinical Development
No Efficacy – No Efficacy – Low/No Efficacy – Efficacy unknown – Serious Adverse Inappropriate No Immediate Currently in Efficacious Effects Immune Response Safety Concerns Clinical Testing
Formalin-inactivated Subunit vaccine Subunit vaccine Live attenuated RSV None alum-precipitated G protein – F glycoprotein in nasally in children whole virus streptococcal alum in adults rA2cp248/404/1030/∆SH conjugate ∆M2-2 Various live attenuated RSV Post-fusion F Rosettes nasally in children
Live virus vaccine delivered IM in children
BPIV-RSV live chimeric virus nasally
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Options for Vaccine Development
Platforms Antigens Delivery Target Populations
Live‐attenuated F Respiratory tract Neonate (<2 mo) • RSV • chimeric paramyxovirus vectors G Parenteral Infants and children (>6 mo) • Sero‐negative Gene‐based vectors • SH Other mucosal site Sero‐positive • Nucleic acid –DNA or RNA • Replication defective Siblings and parents of • Replication competent Internal neonates Subunit or particle‐based Multiple • Purified protein Young adult women • Virus‐like particle • Pregnant women • Virosome • Women of child‐bearing age • Nanoparticle • Peptides Elderly (>65 yr)
Whole‐inactivated RSV
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RSV Vaccine Pipeline
Product Sponsor Type of Vaccine Target Antigen Target population Phase Sanofi RSV vaccine Sanofi Subunit F, G, M protein Elderly patients Phase II BBG2na Queen’s Univ Belfast Subunit G n/a Phase II MEDI-559 MedImmune Live-attenuated Whole virus Infants and children Phase I-IIa MEDI-534 MedImmune Live chimeric F Protein Infants Phase I-IIa MEDI ∆M2-2 & others NIAID +/- MedImmune Live-attenuated Whole virus Adults, infants and children Phase I Novavax RSV Novavax Nanoparticle F Protein n/a Phase I Sendai-RSV chimera St. Jude’s Live chimeric F n/a Pre-clinical RSV vaccine Merck/Nobilon Single-cycle Whole virus n/a Pre-clinical NanoBio RSV Nanobio/Merck Inactivated Whole virus n/a Pre-clinical MVA-BN RSV Bavarian Nordic Vector Subunit Adult high risk patients Pre-clinical GenVec RSV GenVec Vector F Children and infants Pre-clinical Universal RSV Crucell/J&J Vector Subunit Infants and elderly Pre-clinical RSV vac_Oka Okairos Vector F-N-M2-1 n/a Pre-clinical VEE-F Alphavax Vector F n/a Pre-clinical RNA replicon Novartis Vector-RNA F n/a Pre-clinical Mymetics RSV Mymetics VLP-Virosome Multiple Elderly patients Pre-clinical TechnoVax Technovax VLP Multiple n/a Pre-clinical SynGem Mucosis VLP-lactococcus F n/a Pre-clinical RSV VLP Vac LigoCyte VLP F n/a Pre-clinical F protein Novartis Subunit F n/a Pre-clinical RSV vaccine GSK Subunit F Pediatric Pre-clinical AMV601 / RespiVac AmVac Subunit n/a Pre-clinical PEV4 Pevion Subunit F n/a Pre-clinical Epitope-scaffold U. Wash/ TSRI) Epitope-scaffold F epitope Pediatric and at-risk adults Pre-clinical SHe Ghent/Immunovaccine Subunit SH n/a Pre-clinical T4-214 TI Pharma n/a Pre-clinical TWi RSV vaccine TWi Biotech n/a Pre-clinical Sources: Company Website, Fierce Vaccines, RSV 2012 Symposium, Clinicaltrials.gov 11
Outline
• RSV epidemiology and pathogenesis
• History and challenges for RSV vaccine development
• F glycoprotein function, structure, and antigenic sites
• Vaccine antigen design and immunogenicity
• Considerations for vaccine development
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RSV Genome Organization and Protein Functions
M2-1 M2-2 NS1 NS2 N P M SH G F L le tr 3´
15,222 nt total
024106 8 15 kb plasma envelope spikes membrane G (298) - attachment - neutralization target nonstructural - antibody decoy (secreted G) - fractalkine mimic NS1 (139) - inhibit Type I IFN induction - inhibit Type I IFN signaling - TLR antagonist NS2 (124) - activate PI3K and NF-B F (574) - fusion and entry - inhibit apoptosis - neutralization target - TLR4 agonist 150 nm nucleocapsid-associated SH (64) - putative viroporin regulatory - inhibits apoptosis N (391) - RNA-binding M2-2 (90) P (241) - phosphoprotein - viral transcription inner envelope face - RNA replication L (2165) - polymerase M (256) - assembly M2-1 (194) - transcription processivity factor
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Organization of RSV F Glycoprotein
F2 F1
27* 70 116 126 500
* FP HR1 HR2 TM
Regions of high mobility
1 21 37 69 212313 322 333 343 358 367 382 393 416 422 439 550 574
Antigenic sites II I IV
* Unique to RSV •Type I integral membrane protein Signal peptide Fusion peptide •pH‐independent class I viral fusion protein Heptad repeat •Two furin cleavage sites Transmembrane domain •Two heptad repeat regions that form an anti‐ Cysteine parallel six‐helix bundle in post‐fusion state Disulfide bond N-linked glycosylation •F1 has cysteine‐rich domain and a relatively large C-linked palmitylation interspace between the two heptad repeats Furin cleavage site •Short cytoplasmic tail Neutralizing antibody epitope Infection inhibiting peptide
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Comparison of other Class I Fusion Proteins in Native Prefusion Conformation
RSV
Flu
HIV‐1
Modified from Colman and Lawrence, Nat Rev Mol Cell Biol (2003) 4, 309‐19 15
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Mechanism of F-mediated membrane fusion
Fusion peptide Receptor Pierces target cell Hemifusion Full fusion triggering membrane Target cell
Virion
Prehairpin Postfusion Prefusion intermediate six‐helix bundle
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Mechanism of F-mediated membrane fusion
Target cell
Fusion pore established
Delivery of nucleocapsid and genome
Virion
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Antigenic sites present on post-fusion F are not major targets for in vivo NT activity
Site I 131‐2a, 2F Site IV 101F mAb19
Site II Palivizumab Motavizumab
Magro et al, PNAS (2012) 7, 3089‐94
McLellan et al, J Virol. (2011) 18
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Stabilization of Prefusion RSV F with Human mAbs (D25/AM22) Reveals New Antigenic Site
McLellan et al. Science April 2013 19
Vaccine Antigen Selection: Rationale for Choosing F
Reasons for choosing F: • Target of Synagis • Higher sequence conservation than G • Unlike G, F is absolutely required for virus entry
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RSV F Has One Extremely Mobile Domain and Another that is Relatively Fixed
McLellan et al. Science April 2013 21
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Antigenic Site Ø
McLellan et al. Science April 2013 22
Properties of Antigenic Site Ø mAbs
McLellan et al. Science April 2013 23
Antigenic Sites on RSV F Associated with Neutralization
McLellan et al. Science April 2013 24
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Implications of Using Prefusion or Postfusion F
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Antigenic Sites on RSV F Under Immune Pressure
antigenic site Ø
antigenic site II
antigenic site IV Possible antigenic site III as defined in metapneumovirus
antigenic site I – P389
McLellan et al. Science April 2013 26
Outline
• RSV epidemiology and pathogenesis
• History and challenges for RSV vaccine development
• F glycoprotein function, structure, and antigenic sites
• Vaccine antigen design and immunogenicity
• Considerations for vaccine development
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S155C/S290C mutations (DS) can form disulfide bond only in prefusion state
Val154
Ser290
Ser155
Lys156
Prefusion Postfusion Jason McLellan 28
DS version of stabilized prefusion RSV F can be purified to homogeneity
RSV F Δ141‐150 ΔTM
~1,000 particles
2D averages
Ulrich Baxa 29
DS version of prefusion RSV F induces potent neutralizing activity
Week 7
vs.
Prefusion Postfusion
RSV Line 19 (Subtype A) RSV 18537 (Subtype B)
Man Chen 30
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DS does not stabilize antigenic site Ø
D25‐bound DSRSV F Δ141‐150 ΔTM
McLellan et al. Science November 2013 31
Design Approach for Stabilizing Antigenic Site Ø on Trimeric F
Antigenic site Ø
Peter Kwong, Jason McLellan, Gordon Joyce, Guillaume Stewart‐Jones 32
Alternative Method of Stabilization: Cavity-Filling
>5 Å Movement
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Combining Mutations Alters Physical Stability
DS Cav1 Cav1 DS-Cav1 DS-Cav1 DS-Cav1-TriC Cubic Cubic Tetragonal Cubic Cubic Cubic pH 9.5 pH 9.5 pH 5.5 pH 9.5 pH 5.5 pH 9.5
RSV F trimer
relative to V207L V207L V207L V207L V207L Yield 1.4 2.2 1.9 1.3 post‐fusion Antigenic site Ø S155C S155C S155C S155C S190F S190F S190F S190F S190F D25 binding Kd (nm)-S290C 0.29 0.23-S290C 0.15-S290C -S290C 0.17
Temperature 50C0.3 0.8 0.9 0.9 RSV F trimer from top Antigenic site Ø 3.5(purple) 0.1 0.7 0.8 0.6 pH 10 0.8 0.8 0.9 0.9
10 1.3110.6 Osmolality 3000 0.8 0.7 0.8 0.6 Fractional D25 Binding
Freeze‐thaw X10 0.3 0.6 0.7 0 34
DS-Cav1 is More Physically Stable Than DS
100 nm
Jason McLellan, Ulrich Baxa 35
Immunogenicity Achieved by Stabilization is Additive
p < 0.0001 p = 0.0003
Protective threshold
McLellan et al. Science November 2013 36
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DS-Cav1 induces NT activity in NHP against both subtype A and B RSV
RSV subtype A (GMT) RSV subtype B (GMT) 105 105 post-fusion F 104 DS 104 DS-Cav1 103 103 50 50
EC 102 EC 102
101 101
100 100 W2 W4 W6 W8 W10 W14 W20 W2 W4 W6 W8 W10 W14 W20 weeks weeks
DS‐Cav1 DS‐Cav1 ~ 72‐fold ~ 87‐fold Post Post
Man Chen, Srini Rao 37
Matching Vaccine Platform to Target Population
Target Population Challenges Options
Neonate (<2 mo) Vaccine-enhanced disease Gene-based vector Poor immunogenicity +/- Subunit protein Infants and children (>6 mo) Maternal antibody +/- Nanoparticle boost • Sero-negative ? Protein alone • Sero-positive
Siblings and parents of neonates Repeated infections despite prior infections Subunit protein Difficulty boosting pre-existing antibody Nanoparticle Young adult women Pregnancy-related concerns ? Gene-based vector prime • Pregnant women • Women of child-bearing age
Elderly (>65 yr) Poor immunogenicity Difficult efficacy endpoint
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Outline
• RSV epidemiology and pathogenesis
• History and challenges for RSV vaccine development
• F glycoprotein function, structure, and antigenic sites
• Vaccine antigen design and immunogenicity
• Considerations for vaccine development
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Candidate RSV Vaccine Products Based on Stabilized Prefusion F Trimer
• Stabilized prefusion F trimer – Pregnant women – Elderly
• Gorilla-derived rAd vector – Infants < 6 months – Seronegative children >6 months
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Considerations for Immunizing RSV-Naïve Infants
• Opportunity to prevent or delay first RSV infection – Reduced primary morbidity – Reduced childhood wheezing • Opportunity to establish future immune response patterns (antibody specificity and T cell phenotype) – Improved immunity against reinfection • Target age is critical – Peak age of hospitalization ~2.5 mo – ~50% of hospitalization occur >6 mo – If incidence is ~60% in first year, ~70% are RSV‐naïve at 6 mo
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Selecting Target Age for Initiating Vaccination
<4 mo >6 mo Efficacy Somatic mutation ‐ ++ Dendritic cell and APC maturation ‐ ++ Clearance of maternally‐derived antibody ‐++ No longer breast‐feeding ‐ + Safety Idiosyncratic apnea and other rare adverse events + ‐ Small airway size ++ ‐ Relative Th2 bias ++ ‐
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Convergence of Technologies Has Produced a New Vaccine Development Paradigm
New probes
Vaccine antigens Graham BS. Immunol Rev 2013;255:230‐42. 43
New Technologies Have Made an RSV Vaccine Possible
Viral Vaccines Major Conceptual and Technological Advances
Cell Molecular Potential areas for new Discovery of immunity culture biology technical advances RSV ? 16 HPV Structural Biology Rotavirus 14 Varicella Animal Models Japanese 12 Cell Biology encephalitis Hepatitis A 10 Genetics Hepatitis B Rubella Genomics 8 Mumps Glycobiology Adenovirus Measles 6 Immunology Poliovirus Informatics Influenza 4 Yellow fever Manufacturing Rabies 2 Proteomics Smallpox 0
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NIAID Vaccine Research Center
Viral Pathogenesis Laboratory Structural Biology Section
Sung-Han Kim, Syed Moin, Barney Graham, Kaitlyn Peter Kwong, Jason McLellan, Gordon Joyce, Morabito, Azad Kumar, Kevin Graepel, Kayvon Guillaume Stewart-Jones, et al. Modjarrad, Man Chen, Tracy Ruckwardt, Allison Malloy, Jason McLellan, Jie Liu, Erez Bar-Haim
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