1. No heterologous protection with SAT2 SAU
Against SAT2 BOT challenge
A. Dekker, L. Mouton, M. Blanchet, M. Bleijenberg,
J. Coco-Martin, P. Hudelet, S. Goutebroze

2. Background Type A reasonable to good heterologous protection
Even when r-values are low
Even with reasonable genetic distance
Very limited information on SAT2 vaccine
Can high quality SAT2 vaccine also provide cross- protection against heterologous challenge

3. Type A good protection even with low r-value or high genetic distance (VP1 in red)
>32 PD50
3 PD50
6 PD50
4 PD50
14 PD50
0.21
r1 = 0.1
r1 = 0.12
2 PD50
8 PD50
>32 PD50
11 PD50 A
A24 Cruzei
A/IRN/
A/IRN/
0.18
0.26
r1 = 0.1
r1 = 0.23
14 PD50
19 PD50
>32 PD50
0.52
0.60
0.54
11 PD50

4. Kimura genetic distance VP1
Type A: genetic distance 0.18 to 0.54
Reasonable to good protection
Type SAT2: genetic distance SAT2 SAU and BOT 0.40
No information yet
No r1-values available yet

5. Materials and methods Vaccines SAT2 SAU emergency vaccine
Challenge virus
SAT2 SAU cattle challenge virus (3 times)
SAT2 BOT cattle challenge virus (1 time)
European Pharmacopoeia potency test
3 – 4 groups of vaccinated cattle (5 cattle/group)
Full, 1/4 , 1/16, (1/64) dose
2 controls

6. Challenge results (SAT2 SAU vaccine)
3 homologous potency test (94 PD50/dose)
1 heterologous potency test (0.8 PD50/dose)
Full
5/5
1/4
1/16
3/5
1/64 NA
Full
1/5
1/4
3/5
1/16
0/5
1/64

7. Statistical analysis Linear regression
Strong relation between Ab response and vaccine dose
10 times more vaccine  4 times higher antibody titre
Generalised linear regression
Binomial with logistic link function
Challenge strain best predictor of protection
Antibody response very strong predictor of protection

8. Relation Ab response and protection

9. Conclusion SAT2 SAU vaccine is a very good vaccine bank strain
94 PD50/dose against homologous challenge
Antibody response very strong predictor of protection
For heterologous SAT2 BOT challenge 1 log higher Ab titre needed
r-values of SAT2 SAU and SAT2 BOT should be determined
Vaccine banks should include more than 1 SAT2 strain
More data on circulating strains is necessary

10. Thank you for your attention
Good vaccines can induce heterologous protection, but it can fail (FMD vaccine banks should test their vaccines!)