Establishment Of Guinea Pigs Potency Model For Inactivated Bovine Foot-and-Mouth Disease Vaccine Serotype Asia-1

The 50% protective doses (PD₅₀) testing in host animal has been the standard process for evaluating the potency of inactivated foot and mouth disease (FMD) vaccine. This traditional methodology requires a great number of na?ve host animals, and it is very difficult to find enough resources for the na?ve animals. In addition, the test is very expensive and needs a lot of labour works. As laboratory animals, guinea pigs have been used in the research of FMD virus for decades. Neutralization antibody elicited in the vaccinated guinea pigs and protection of the guinea pigs against morbidity of FMD caused by challenge with virulent FMD virus could serve as criteria in the evaluation of potency for inactivated FMD vaccine. In this study, guinea pigs were studied as animal model to replace the host animals in testing the potency of FMD vaccine.PD₅₀ test was conducted to evaluate the potencies of six batches of inactivated bovine serotype Asia-1 FMD vaccines in both guinea pigs and cattle. Of the six batches of vaccines, two batches were repeatedly tested. Vaccinated guinea pigs and cattle were challenged with the vaccine homologous FMD virus strains at days 28 and 21 post-vaccination, respectively. The challenged animals were clinically observed for FMD morbidity for 10 days, and the PD₅₀ values were calculated using the Reed-muench method. Statistical correlation of PD₅₀ values between tests in guinea pigs and in cattle was analyzed. Guinea pigs were bled at days 7, 14, 21 and 28 post-vaccination and serum samples were used to monitor the neutralizing antibody titers against serotype Asia-1 FMDV. Finally, the neutralizing antibody titers at day 28 post-vaccination and the protection of the vaccination against the challenge were analyzed for the correlation between the antibody titers and the disease protection in vaccinated guinea pigs.Results demonstrated that the six batches of inactivated bovine serotype Asia-1 FMD vaccine, namely N004, N005, N007, N010, N011, and N012 had the PD₅₀ values of 1.69, 6.47, 5.89, 5.25, 5.37, and 5.25 in cattle, and 2.33, 4.57, 4.20, 2.87, 4.27, and 3.00 in guinea pigs, respectively. The repeated test results of PD₅₀ values for 2 batches N007 and N010 were 6.63 and 4.53 in cattle, and 4.0 and 3.1 in guinea pigs. SPSS statistical analysis demonstrated a very significant correlation of PD₅₀ values between tests in guinea pigs and in cattle (R=0.846, P<0.01). Based on the results, a linear regression model y=1.625x - 0.704, where x is PD₅₀ in guinea pigs and y is PD₅₀ in cattle, was established for the prediction of potency of inactivated bovine serotype Aaia-1 FMD vaccines using PD₅₀ value obtained in guinea pigs. Furthermore, the model was strongly supported and approved by F-test (F=15.058, P=0.008<0.01) and T-test (t=3.880, P=0.008<0.01).The specific neutralizing antibody response against FMD virus was detected at day 7 post-vaccination in vaccinated guinea pigs, and antibody titers were various along with the time and reached to the peak at day 28 post-vaccination. The neutralizing antibody titers detected in the guinea pigs were vaccine dose-dependent, i.e. the neutralizing antibody titers increased as the increasing of vaccine dose. There was a positive correlation tendency between antibody titers at day 28 post-vaccination and the protection from FMD caused by challenge in the vaccinated guinea pigs. In conclusion, guinea pig is a good animal model for evaluating the potency of inactivated bovine serotype Asia-1 FMD vaccine, and there is a very significant correlation of PD₅₀ values between tests in guinea pigs and in cattle. This initial research revealed that use of guinea pigs to replace cattle as the testing animals to evaluate efficiency of inactivated bovine serotype Asia-1FMD vaccines is feasible.