Expression And Immunogenicity Analysis On Empty Capsid Of Foot-and-mouth Disease Virus Type O Myanmar's 98 Strain

Foot-and-mouth disease(FMD)is a highly contagious disease caused by foot-and-mouth disease virus(FMDV),which mainly infects cloven-hoofed such as pigs,sheep and cattle and causes huge economic damage to livestock sector.FMD was listed as a notifiable disease by the Office International Des Epizooties(OIE)and also listed as the top one of the class I animal diseases in China.At present Vaccinoprophylaxis is the most effective measure to control of the disease.Vaccination with inactivated whole-virus vaccine is the major means of FMD control in most endemic areas worldwide.But the inactivated vaccine has a potential risk of inactivating the virus incompletely,resulting in virus escaping during the manufacturing process.Viral empty capsid is as immunogenic as virions but contains no viral nucleic components,therefore it is safer than the inactivated virus.In this study,P12A-3C genes of FMDV type O Myanmar's 98 strain(O/MYA98/BY/2010)were used for generation of FMDV empty capsid expressed in baculovirus.In order to improve stability of FMDV empty capsid in acid condition,different amino acid substitutions in FMDV P1 were carried out.Two recombinant baculoviruses that contained different mutational P12A-3C genes and one recombinant baculovirus that contained the wild type P12A-3C genes were constructed.The successful expression of FMDV empty capsid protein in the Sf9 insect cells inoculated with the recombinant baculoviruses were confirmed by IFA,Western-Blot and DAS-ELISA.All three expressed recombinant capsid proteins showed to have good antigenicity.Two mutational recombinant capsid proteins also showed to have relevant acid-resistant stability.Three groups of empty capsid vaccine were generated by mixing the recombinant capsid proteins with GEL adjuvant and then used to vaccinated mice.Antibody against FMDV was detected in all vaccinated animals,and the antibody level was equal to or greater than the conventional inactivated vaccine group.The virus challenge experiment was carried out in guinea pig at 21 days after vaccination with FMDV Myanmar's 98 Strain,similar with the inactivated vaccine group,majority of animals vaccinated with the recombinant capsid vaccines were protected from challenge with FMDV.All these results showed that FMDV empty capsid are as immunogenic as the intact virus particles and can be naturally produced in infected cells and,which would provide an excellent subunit FMD vaccine candidate for production of new FMD vaccine.