Heterologous Protection Study Against SAT2 BOT Challenge
Explore the findings of a study evaluating heterologous protection with SAT2 SAU against SAT2 BOT challenge. The study discusses genetic distance, vaccine efficacy, and statistical analyses, shedding light on the potential cross-protection of high-quality SAT2 vaccines.
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Presentation Transcript
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
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
Type A good protection even with low r- value or high genetic distance (VP1 in red) r1 = 0.09 6 PD50 r1 = 0.04 4 PD50 >32 PD50 3 PD50 0 14 PD50 0.21 0 r1 = 0.1 r1 = 0.12 11 PD50 2 PD50 8 PD50 r1 = 0.1 14 PD50 >32 PD50 0.18 0.26 0 r1 = 0.23 19 PD50 >32 PD50 0.52 0.60 0.54 0 11 PD50 3
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 4
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 5
Challenge results (SAT2 SAU vaccine) 3 homologous potency test (94 PD50/dose) Full 1/4 1/16 1/64 5/5 5/5 5/5 NA 5/5 5/5 5/5 NA 5/5 5/5 3/5 3/5 1 heterologous potency test (0.8 PD50/dose) Full 1/4 1/16 1/64 1/5 3/5 0/5 0/5 6
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 7
Relation Ab response and protection 1.0 0.8 SAT2 SAU challenge 0.6 protection SAT2 BOT challenge 0.4 0.2 0.0 1.0 1.5 2.0 2.5 3.0 3.5 8 SAT2 SAU titre at challenge (log)
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 9
Thank you for your attention Good vaccines can induce heterologous protection, but it can fail (FMD vaccine banks should test their vaccines!) 10
