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
2

3.
2 PD50
8 PD50
Type A good protection even with low r-
value or high genetic distance (VP1 in red)
3
r1 = 0.09 r1 = 0.04
r1 = 0.1 r1 = 0.23
r1 = 0.12r1 = 0.1
0
0.21
0.18
0.52
0
0.26
0.60
0
0.54 0
14 PD50
>32 PD50
>32 PD50
>32 PD50
14 PD50
19 PD50
11 PD50
4 PD506 PD503 PD50
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
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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
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6.
Challenge results (SAT2 SAU vaccine)
3 homologous potency test (94 PD50/dose)
1 heterologous potency test (0.8 PD50/dose)
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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
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8.
Relation Ab response and protection
8
1.0 1.5 2.0 2.5 3.0 3.5
0.00.20.40.60.81.0
SAT2 SAU titre at challenge (log)
protection
SAT2 SAU challenge
SAT2 BOT challenge

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