Dr Stuart Dowall Project Team Leader Virology and Pathogenesis group Development of a vaccine...
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Transcript of Dr Stuart Dowall Project Team Leader Virology and Pathogenesis group Development of a vaccine...
Dr Stuart Dowall
Project Team Leader
Virology and Pathogenesis group
Development of a vaccine candidate against Crimean-Congo Haemorrhagic Fever (CCHF)
virus
Background
Preclinical development of the PHE CCHF vaccine PHE pipeline fund PLF 1516/108/MR
Crimean-Congo Haemorrhagic Fever (CCHF) virus:
• Severe human infection.
• Fatality rate 30% (9-50%).
• No FDA or European approved vaccine or treatment.
• Transmission by tick bite or contact with
infected blood/body fluids.
• ACDP hazard group 4 pathogen.
2 Development of a vaccine against CCHF virus
3
1. Spread of vector across Europe. 2. Increased incidence in tourism areas.
Why is it important to PHE?
Development of a vaccine against CCHF virus
4
3. Threat is national and international
Why is it important to PHE?
5. Threat to armed forces.
4. Increases PHE international profile
Development of a vaccine against CCHF virus
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6. Potential bioweapon
Why is it important to PHE?
7. Maintain emergency response capability so expertise available.
• Negative sense RNA genome giving high rate of mutations.• Segmented genome allows genetic reassortment of viruses.• Existence of an animal reservoir.• Highly pathogenic (requiring Containment Level 4 facilities).• Large risk of nosocomial spread within hospitals.
Development of a vaccine against CCHF virus
Lack of treatments against CCHFNo vaccines or antiviral drugs are approved for CCHF by FDA or EMA.
Bulgarian vaccine candidate has major disadvantages:
• Requires live CCHF virus
• Crude preparation (non-standardised homogenisation of mouse brain)
• No efficacy studies, no interest to generate data package since 70s
• Is not acceptable to FDA/MHRA/EMA approval
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Alternative approach badly needed for a modern CCHF vaccine that can meet regulatory approval and is proven to be effective.
Development of a vaccine against CCHF virus
Development of the vaccine candidate
Our approach: We have used Modified Vaccinia Ankara (MVA) as a viral vector to induce immune responses against an inserted CCHF protein antigen.
Properties of MVA that make it attractive:• Human safety history: >100,000 doses in 1970s with no adverse effects.• Human cells non-permissive.• Induction of humoral and cellular immunity.• Industrial GMP established.• Thermostable.• Production of recombinant proteins.• Clear commercial opportunities
• Vaxgene, Baxter, Bavarian Nordic, Emergent all in clinical trials with MVA-based vaccines.• Approximately extra 100,000 people vaccinated with no adverse signs.
• Inexpensive, low cost approach
7 Development of a vaccine against CCHF virus
Development of the vaccine candidate
8
Antigen sequence
N-terminal tPA for secretion& Nab induction
GFP for selection of recombinant viruses
Glycoprotein
L RTransferplasmid
L R
L RMVA genome
L R
MVA permissive cell
MVA
GFP+ plaquepurification
C-terminal V5 for in vitro antibody recognition
Development of a vaccine against CCHF virus
9
Confirmation of antigen expression
MVA-G
P
posit
ive co
ntro
l
Anti-V5 antibody(expected size of GP-V5 fusion protein = 76.6kDa,
positive control protein = 62kDa)
MVA-1
974
CCHF+ SW
13
SW13
cells
MVA-G
P
Anti-CCHF rabbit polyclonal sera(similar post-translational cleavages in
MVA-GP to native protein)
Development of a vaccine against CCHF virus
10
Similar responses in 129Sv/Ev and A129 mice were detected.Immunogenicity was not evenly distributed across the antigen. Responses were specific to the glycoprotein, and similar between mouse strains.
Media
GP peptides
The vaccine induces cellular immunity…IFN- ELISPOT assay
Solid bars = 129Sv/Ev mice; hatched bars = A129 mice
Summed antigen responses Individual peptide pools
Development of a vaccine against CCHF virus
11
…and humoral immunity.ELISA studies
The MVA-GP vaccine induced significant CCHF glycoprotein-specific antibodies.
Uninfe
cted
SW13
cells
CCHFv-inf
ecte
d SW
13 ce
lls
Western blot
Development of a vaccine against CCHF virus
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Day 0 7 14 21 28 35 42
Prime BoostCCHF
Challenge Analysis
Efficacy studies
100% protection from lethal challenge First demonstration of CCHF
vaccine efficacy
Development of a vaccine against CCHF virus
13
RT-PCR for CCHFv gene expression (normalised to mouse HPRT gene expression).
Day 32 = 4 days post-challengeDay 42 = 14 days post-challenge (end of study)
Viral load was significantly lower in MVA-GP vaccinated mice than in control groups.
Viral loads
Blood LiverSpleen
Development of a vaccine against CCHF virus
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HistologyLiverSpleen
MVA-1974
MVA-GP
Marked lymphocyte loss with prominent apoptotic bodies, and infiltration by macrophages.
Marked, multifocally extensive hepatocyte necrosis (arrows).
A single infiltration of macrophages in the white pulp (asterisk) (scored minimal).
Scattered, multifocal areas of hepatocellular necrosis with a mixed inflammatory cell infiltrate (arrows) (scored moderate).
H&E staining
Immunised A129 mice, 4 days post-challenge
Development of a vaccine against CCHF virus
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HistologyLiverSpleen
MVA-1974
MVA-GP
Immunostaining
Immunised A129 mice, 4 days post-challenge
A few, scattered cells with cytoplasmic staining within the parenchyma.
Frequent, diffuse, positively stained hepatocytes.
Normal parenchyma. A few, positively stained cells within an inflammatory cell focus.
Development of a vaccine against CCHF virus
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Immunise mice with MVA-GP Isolate splenocytes (T-cells) and sera (antibody)from immunised mice
Adoptively transfer splenocytes into naïve mice
Passively transfer sera into naïve mice
Challenge with CCHF virus
Determine survival effects
Next steps
Development of a vaccine against CCHF virus
Market Segment $M/Annum
Adult 6.0
Travel 7.6
Military (Range) 19.5 - 43.5
Total 33.1 – 57.1
• CCHF represents a niche market • Main opportunity in military based on a range of between $33.1 – $57.1
million• Market only likely to be capable of supporting a single manufacturer and
heavily reliant on military
Market sizing
17 Development of a vaccine against CCHF virus
Summary
• CCHF is a real and growing threat – most widespread VHF across Europe/Asia Africa.
• PHE’s vaccine candidate is promising with efficacy proof of concept in mouse model.
• Next step is to confirm mechanism of action (passive/adoptive transfer studies).
18 Development of a vaccine against CCHF virus