Study And Immunity Assessment Of Synthetic Peptide Vaccines Against AF72Strain Of Foot-acci-mouth Disease Virus Type A

Foot-and-mouth disease (FMD), an acute, violent, infectious disease of the artiodactyl (pigs, cattle,sheep, camels, etc.), is caused by foot-and-mouth disease virus (FMDV). At present the main FMDvaccine is still inactivated vaccine. However, people have realized many disadvantages of inactivatedvaccine. In order to improve these problems, the scientists are conducting some new research aboutnovel FMD vaccine, such as synthetic peptide vaccine. This study aimed at exploring and developing akind of synthetic peptide vaccine against FMDV AF72strain, so as to provide a new idea for controllingfoot-and-mouth disease.1. AF72strain was passaged respectively in guinea pigs and BHK-21cells until the virulence wasstable. Then, the ID50and TCID50were assayed. Six pairs of primers were designed to sequence thewhole sequences of AF72. Amino acid sequence homology of VP1、VP4and3ABC between differentFMDV strains were analyzed. The TCID-5.9250and ID50were respectively10-6.91and10computed byKarber principle; The whole sequence of AF72was about8206nt long; The amino acid sequencehomology of VP1between AF72and other FMDV strains of type A was79.8%－89.2%, however itwas61.6%－69.9%among different types. The amino acid sequence homology of VP4and3ABCbetween different types were respectively94.1%－98.8%and90.2%－98.2%.2. According to the FMDV epitopes identification report, several epitopes were picked out forbioinformatics analyzes. At last, two synthetic peptides named A and B, which contained VP1[131－159aa], VP4[20－35aa],3A[21－35aa],3B[29－42aa], were designed according to the sequence ofAF72. B was linked by the GG linker in series, while B was linked by the KK linker in parallel. Theresults showed that VP1[131－159aa] and3B[29－42aa] were likely contain B cell epitope; VP1[131－159aa], VP4[20－35aa] and3A[21－35aa] were likely contain many CTL and Th cell epitopes.3. Vaccines were made up of synthetic peptides, PBS and206ISA adjuvant. In order to evaluatethe efficiency of these vaccines in guinea pigs, we studied the humoral immunity and cellular immunity.We assayed the FMDV specific IgG and neutralizing antibody level; isolated the subtype of IgG;measured the IL-4, IL-2，IL-12and IFN-γ level; measured the proliferative capacity of spleniclymphocytes; also we distributed the peripheral blood T lymphocyte CD4-CD8subsets. The resultsshowed that the FMDV specific IgG、neutralizing antibody、cytokines level、CD4/CD8ratio and animalprotection rate was highest in inactivated vaccine immunizised group, followed by synthetic peptidegroup A-2.5. According to the results of humoral immunity and cellular immunity, inactivated vaccinewas the best, and group A-2.5was identified as the best group among the synthetic vaccines.