Cattle TB Vaccine Development in GBCattle TB Vaccine Development in GB

Martin VordermeierMartin Vordermeier

Animal Health &Veterinary Laboratories Agency - Weybridge, U.K.Animal Health &Veterinary Laboratories Agency - Weybridge, U.K.

17 August 2012

• Background on cattle TB vaccine development programme in GB

• BCG laboratory and field study results: Which strain, vaccination age, skin test effects, duration of immunity

• BCG plus: Vaccines better than BCG (principles)

• DIVA development (principles)

• Summary

Presentation outline

Control strategy: Tuberculin skin test and cull

Developing TB cattle vaccines

• Developing an effective cattle TB vaccine is a high priority for Defra. We have invested ca. $ 500 million in cattle vaccine and associated diagnostics R&D since 1998/99, and over the next 5 years have budgeted to spend a further $19 million

• To date the most promising approaches in cattle are BCG based - either with BCG on its own or to use a heterologous BCG prime-boost strategy where combinations of BCG-DNA, BCG-protein and BCG-virus-vectored vaccines have induced better protection than BCG vaccine alone

Current state of play with a cattle BCG

• Experimental vaccination-challenge studies now completed to:

– Demonstrate efficacy of BCG in neonates and older cattle– Demonstrate safety of BCG in neonates and cattle in each trimester

(allows for vaccination in all age groups)– Determine duration of immunity (demonstrated out to one year)

• Licensing portfolio for Marketing Authorisation submitted and is being assessed by the Veterinary Medicines Directorate (VMD) for approval

• If satisfied with the dossier, VMD would be able to provide ‘agreement in principle’ to license (but would not be able to grant an MA due to EU prohibition on anti-tuberculosis cattle vaccines)

EU prohibition on cattle TB vaccination

• TB vaccination of cattle specifically prohibited under EU national eradication plans (Directive 78/52/EEC) – This includes field trials!

• OTF (Officially TB Free) testing requirements (tuberculin skin test) for trade in live cattle (Directive 64/432/EEC)

• Trade in cattle products tightly controlled by Reg (EC) 853/2004 and BCG vaccinated cattle would give false positives

• Need these lifted before vaccination could be used in the UK

• Opportunity created by new Animal Health Law which is under consideration but we must not underestimate the difficulties involved in lifting prohibition on vaccines and allowing DIVA use

DIVA test requirement

• BCG vaccination of cattle can result in reactivity to tuberculin diagnostic tests (both to the Single Intradermal Comparative Cervical Tuberculin test (SICCT skin test) and the interferon gamma blood test)

• As many as 80% of BCG vaccinated but uninfected animals can be skin test positive 6 months post vaccination but thereafter proportion drops quickly with about 10% testing positive 9 months post vaccination

• In parallel with our cattle vaccine research we are developing a DIVA test to differentiate infected from vaccinated animals

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M. bovis bacille Calmette-Guérin:BCG/BCG based strategies(e.g. ‘Heterologous prime-boosting’)

• Live, attenuated M. bovis• Attenuated in cattle since 1912• Used in humans since 1927• Safe in a wide range of species• Cheap• Recommended by WHO for humans• Variable efficacy in humans and

cattle (average ca. 50%), and compromises tuberculin based diagnosis

Albert Calmette

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BCG strains:

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Experimental approaches to test TB vaccines in cattle

Model Advantages Disadvantages

Experimental challenge: Low dose intratracheal model

‘Few’ animals required

(n <10-12/group)Still relatively high dose: Immune system may be overwhelmed  

  Short duration (3-4 months)  

‘Field experiment’:In contact transmission

Natural route and infective dose

Many more animals required (60/group)

    Long in-contact period (12 months)

Field trial Real-life situation 

Very large numbers required (n = 100-1000s)

    Long and expensive (years) and illegal in EU

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In our earlier studies we used BCG Pasteur (as this was recommended by WHO for humans).

But the only BCG strain commercially available and licensed for human in Europe: BCG SSI (Staten Serum Institut, Copenhagen, Denmark)

THEREFORE: We changed to BCG SSI

First challenge: Demonstrate protective equivalence of BCG Pasteur and BCG SSI

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BCG Pasteur and BCG SSI give equivalent protection:

Conclusion:

Conclusion:

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BCG vaccination of neonatal or very young calves works at least as good as vaccinating older animals:

Conclusion:

Conclusion:

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10

20

30

40

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Pat

holo

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BCG Danish vaccination experiments in cattle after intra-tracheal infection conducted at AHVLA/IAH over the last 6

years: BCG works!

Duration of immunity?

1-year

DOI

2-years

DOI

N N N N

BCG M. bovis

BCG M. bovis

1 year

2 years

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Waning of tuberculin skin test responses following BCG vaccination

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Maintenance of skin test responses are not required for protection

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Field BCG (BCG SSI) vaccination experiment conducted in Ethiopia (Wellcome Trust funded study)

TBTB

TBTB

TBTB TBTB

TBTBTBTB

TBTB

TBTB

Unvaccinated sentinelUnvaccinated sentinel

Vaccinated sentinelVaccinated sentinel

Reactor (TB)Reactor (TB)

TBTB

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BCG vaccination experiment in Ethiopia (2007-09)

Study site: High-intensity farm, central highlands west of Addis Ababa (Oromiya Province)

Vaccine, dose and route: BCG SSI (freeze-dried), 106 CFU, subcutaneous

Breed of donors and vaccinates: Pure-bred Holsteins

Neonatal vaccination (<3 weeks of age)

Type of challenge: In-contact with reactor animals, standard farming/husbandry conditions

Exposure to reactors: about 3 months post-vaccination

In-contact period: 10 – 22 months

Read-out: Gross pathology/M. bovis culture

Lead scientist: Dr Gobena Ameni (AHRI/IPB Addis Ababa)

Collaborators: Glyn Hewinson/Martin Vordermeier (VLA)

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BCG vaccination induced good level of protection: Pathology and microbiology

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BCG-12 mo BCG-24 mo

Pat

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Duration of immunity: Comparison of field study results with experimental infections

Longer in real-life exposure situation?

Experimental intra-tracheal infection studies

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Field transmission study: DOI under natural transmission conditions

BCGControls

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Better than BCG: Strategies P

rote

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e im

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Time

BCG

Boost Amplify/Boost

Immunity level sufficient for protection

Boost

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Our approaches to (hopefully) better tests:

•Antigen mining to generate defined reagents for DIVA and not affected by infections with NTM (blood test format, Interferon-gamma

release assay)

•Use of these antigens as skin test reagents

•Search for host biomarkers adding additional sensitivity

DIVA Development

Differential Immune-Diagnosis

Vaccine or cross-reactive pathogen

TB

Blood test detectsresponse to componentsonly recognised in TB

Summary

• Protection: BCG Danish/BCG SSI = BCG Pasteur

• Neonatal BCG vaccination at least as good as vaccinating older animals

• BCG protects reproducibly in experimental challenge studies AND equally if not better in field exposure study

• Duration of immunity: at least 1 year, field study suggests longer

• Boosting with virally vectored vaccines can improve on BCG (not shown)

• DIVA based on blood test (IGRA) or skin test (not shown)

What does the science tell us?

• BCG is the most suitable candidate in the short term

• Could be a useful tool, but not perfect - will still need other TB control measures

• Vaccination affects the skin test – but we can now reliably differentiate between vaccinated and infected animals

• Likely to need annual re-vaccination

• New development pathway: Effective vaccine that does not sensitise tuberculin skin reactions (non-sensitising vaccines)

AHVLA Weybridge

Adam Whelan

Bernardo Villarreal-Ramos

Phil Hogarth

Sabine Steinbach

Elihu Cortes

Gilly Dean

Gareth Jones

Rory Cooney

Glyn Hewinson

AgResearch, NZ

Bryce Buddle

Neil Wedlock

McMaster, Toronto, Canada

Zhou Xing

AHRI, Addis Ababa, Ethiopia

Gobena Ameni

Jenner Institute, Oxford

Adrian Hill

Helen McShane

Sarah Gilbert

Jenny Piercy

IAH, Compton

Martin McAulay

Jayne Hope

Lionex Ltd/Helmholtz Centre, Braunschweig

Mahavir Singh

Sabin Bhuju

NADC, USDA, Ames, USA

Ray Waters

Tyler Thacker

Funded by Defra (UK), EU, Wellcome Trust