Cattle Vaccine and DIVADevelopment

Martin Vordermeier

3rd October 2013, ZSL London

Supporting DEFRA policy on cattle TB vaccination:

• Towards field trials and licensing of BCG, regulatory aspects: Efficacy studies (within group) and GLP safety studies (as sponsors and Defra project managers)

• Development of associated DIVA test(s) that would work alongside BCG vaccination

Looking further ahead approaches:

• Vaccines/vaccination strategies that improve on BCG such as subunit vaccines that supplement/enhance BCG efficacy

• Vaccines that do not sensitise tuberculin skin test reactions so that one could continue with existing test and slaughter strategies alongside vaccination

Cross-cutting objective:

• Protective biomarker studies to accelerate vaccine development

BCG is a proven technology

• Live attenuated Mycobacterium bovis• Attenuated in cattle since 1912• Used in humans since 1927• Safe in a wide range of species• Cheap• Recommended by WHO for humans• Different vaccine strains available: we use BCG

Danish SSI as this is licensed in UK for humans• Variable efficacy in humans and cattle and

compromises tuberculin-based diagnosis

4

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, vaccine effect may be an under-estimate  

  Short duration (3-4 months)  

‘Field experiment’:In contact transmission

Natural route and infective dose

High transmission rates or large group sizes required

    Long in-contact period (12 months)

Field trial Real-life situation 

Very large numbers required

    Long and expensive (years)

0

10

20

30

40

* * * * * *

Pat

holo

gy S

core

BCG Danish vaccination experiments in cattle after intra-tracheal infection conducted at AHVLA/IAH:

Effective vaccine , 1-year duration of immunity

1-year

DOI

2-years

DOI

N N N N

BCG M. bovis

BCG M. bovis

1 year

2 years

Protection offered by BCG SSI Danish vaccination:Equal protection of young (neonatal/< 6 weeks) and

older calves

Experiment 1 2 3 4 5 6 7 8

Age (weeks) < 6 < 6 < 6 ca. 36

20-32 < 7 20-32 20-24

Dose 5 5 5 5 5 5 5 5 0.5

Ethiopian ‘Natural transmission model’

• Evaluation of the efficacy of BCG in bovine neonates under natural transmission in Ethiopia

• Vaccinated and control calves in contact with infected cows (12 - 22 months)

TB

TB

TB TB

TBTB

TB

TB

Unvaccinated sentinel

Vaccinated sentinel

Reactor (TB)

TB

‘Natural Transmission’ study: Main Findings

• 69 % of vaccinated animals were fully protected from infection having no signs of visible lesions and being culture-negative compared to 21 % of cattle in the control group. This equates to a level of protection of 61 % (Ameni et al. 2010).

• When the condemnation rate at meat inspection was used as additional read-out system, 73 % of the control cows would have been condemned compared to 23 % of the vaccinated (= 68 % protection).   

• This study suggested that duration of immunity may be longer in the field than the minimum of one year demonstrated through the experimental vaccination and challenge experiments (> 22 months)

• Effectiveness of cattle vaccination in GB field conditions is currently unknown.

Safety studies in cattle• Two safety studies completed

1. Neonatal cattle– Detected no spread beyond immediate draining of lymph nodes in a

minority of animals– No shedding in faeces or saliva

2. Pregnant cattle– Detected no spread beyond immediate draining of lymph nodes in a

minority of cows– No shedding in faeces, saliva, colostrum or milk

Two more GLP safety studies ( ‘animal phase’ to start October 2013):

- Meat safety: Kinetics of dissemination in calves

- Milk safety: Vaccination of lactating cattle

Summary BCG

• BCG strains tested (Pasteur and Danish) give equivalent protection): Danish chosen because licensed in UK for humans

• Neonatal BCG vaccination as good as vaccinating older animals• BCG protected cattle in experimental challenge studies AND better in

field exposure study • BCG vaccination reduces the progression, severity of TB and could

reduce transmission between animals• Duration of immunity: at least 1 year (annual re-vaccination), but field

experiment suggested may last longer• Skin test sensitisation is reduced from 80% to 8% between 6-9 months

post BCG vaccination so DIVA test required, see second part of talk• Need for field trials to move forward, design and preparatory laboratory

studies are in progress • Could be a useful tool, but not perfect - will still need other TB control

measures

Differential Immune-Diagnosis

Vaccine or cross-reactive pathogen

TBBlood test detectsresponse to componentsonly recognised in TB

An effective DIVA test is now available

BCG primes for tuberculin reactivity, so vaccination

based on BCG would need to be accompanied by

a DIVA test

DIVA antigens• Genes missing from BCG

o ESAT-6o CFP-10

• Genes expressed by BCG but not secretedo Rv3615c

– Sensitivity – Proportion of true-positives (infected individuals correctly identified)

– Specificity – Proportion of true negatives (non-infected individuals correctly identified) OR: probability of test to correctly identify patients who are known NOT to have the disease:

Definitions:

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Interferon gamma DIVA test – Validation (IFN-gamma test)

Cohort Type of infection

Sensitivity Specificity

Vaccinated infected + vaccinated uninfected

Experimental 0.93 (0.82-0.99) 0.96 (0.92-0.98)

Unvaccinated infected + unvaccinated uninfected

Natural 0.90 (0.84-0.95) 0.98 (0.97-0.99)

• DIVA can be used serially or as a stand-alone test

• Limited numbers of vaccinated cattle, data shown are serially testing results

Compared to PPD-B minus A in the field animals cohorts SE in field = 0.93-0.95, SPE = 0.97-0.98

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Test systems available for DIVA:

•Interferon-gamma release assays (IGRA) based on e.g. Bovigam assay

•DIVA based on skin test

• Jenner Institute, Oxford• IAH, Compton• Roslin Institute, Edinburgh• AFBI, Stormont, NI• University of Surrey, Guildford

• AgResearch, Palmerston North, New Zealand• McMaster, Toronto, Canada• NADC, USDA, Ames, USA• Helmholtz Centre, Braunschweig, Germany• Infectious Diseases Research Institute (IDRI), Seattle, USA• INRA, Tours, France• University of Zuerich, Switzerland• Armauer Hansen Research Institute, Ethiopia• UNAM, Mexico City, Mexico• CRESA, Barcelona, Catalonia, Spain• EU-RL, Madrid, Spain• CVL-Lelystad, Lelystad, the Netherlands

• Prionics, Schlieren, Switzerland• Lionex Ltd, Braunschweig• SSI, Copenhagen• ID-Vet, Montpellier, France

Funded by Defra (UK), EU, Wellcome Trust, TRANSVACM Vordermeier is a Jenner Investigator

National and International Network