Differences In Immune Response Induced By Foot-and-Mouth Isease Virus With Different Nonstructural Proteins

The commercial foot-and-mouth (FMD) vaccines comprise chemically inactivated virus particlesincorporated in adjuvant.and play an important role in prevention, control and eradication of FMD inendemic regions of the world. It is known that the vaccine-induced protection is generally correlatedwith high levels of neutralizing antibodies. However, knowledge of cell-mediated immune responsesand immune efficacy of NSP in protective immunity to FMDV is limited. CD4+T cell responses aresuggested to play an important role in protection against FMDV, but link between the duration ofabsolute immunity and amount of antivirus specific CD4+T cell remins unclear. Recent studiesdemonstrate the presence of FMDV-specific CD4+and CD8+T cell response in both infected andvaccinated animals. Furthermore, FMD virus (FMDV) NSP2B was found to be able to improve theefficacy of adenovirus-vectored FMDV capsid subunit vaccine against FMDV serotype O and inducesignificant increase in the percentage of specific-CD8+and CD4+. Idenification of CD4+and CD8+T cellepitopes in FMDV NSP indicates that NSP may play an immprotant role in cell mediated immunityaginst FMDV. In present study, recombinant FMDV Re-Mya98/BY/2010and wild-type strainMya98/BY/2010with the identical structure protein but different NSP were used to immunized guineapigs and pigs, and immune response in these animals were then evaluated.(1) Differences of immune response and protection rate in immunized guinea pigsThe recombinant virus Re-Mya98/BY/2010was constructed by replacing the structuralprotein-coding gene of the O vaccine strain, with that of the wild type strain Mya98/BY/2010. Both therecombinant and wild-type viruses was inactivated with BEI and formulated with four differentadjuvants (EMULSIGEN-BCL, EMULSIGEN-D, ISA206, POLYGEN). The guinea pigs werevaccinated muscularly and challenged with Mya98/BY/2010at28day post vaccination (28dpv).Cellular and humoral immune responses at different days post vaccination were analyzed. Bothrecombinant virus Re-Mya98/BY/2010and wild-type viruse Mya98/BY/2010were able to inducestrong anti-FMDV antibody response, but there was no difference in level of antibody in both groups ofvaccinated guinea pigs (P>0.05) regardless of adjuvants. Interestingly, a significant antigen specificCD4+and CD8+T cell response was detected at21dpv with the stronger CD8+T cell response in thegroup of guinea pigs vaccinated with the recombinant virus. Of four groups of guinea pigs vaccinatedwith Re-Mya98/BY/2010, three groups had a statistically significant higher antigen specific-CD8+T cellresponse at21dpv when compared to those in guinea pigs vaccinated the wild-type strainMya98/BY/2010(P<0.05). However, there was no significant difference in the CD4+Tcell response(P>0.05). The protection rate in guinea pigs vaccinated with the recombinant virus Re-Mya98/BY/2010with four difference adjuvants (EMULSIGEN-BCL, EMULSIGEN-D, ISA206, POLYGEN) was100%,100%,83.33%and50%, respectively while the guinea pigs vaccinated with FMDVMya98/BY/2010was20%,0%,17%and25%, respectively, and the difference of protection rateinduced by the two strains was statistically significant (P<0.01). These results indicate that inclusion ofthe complete NSP may be able to improve the efficacy of vaccine-induced specific-CD8+T cell responses which enhance vaccine-induced protection.(2) Differences of immune response and protection rate in immunized pigsTwo chemically inactivated whole-virus preparations which were emulsified with ISA206wereselected and used to vaccine pigs (n=5/group) based on the results in immunized guinea pigs. Cellularand humoral immune responses at different days post vaccination were investigated in immunized pigs.There was no difference of the protection rate observed between pigs vaccinated with recombinant virusRe-Mya98/BY/2010and pigs with wild-type viruse Mya98/BY/2010(P>0.05), and the two vaccinesoffered clinical protection. Both recombinant virus Re-Mya98/BY/2010and wild-type viruseMya98/BY/2010induced strong anti-FMDV antibody response, but there was no difference in level ofantibody response (P>0.05). However, a significant antigen specific-CD3+T cell response was detectedin the group of pigs vaccineated with Re-Mya98/BY/2010. Furthermore, in this group, a statisticallysignificant stronger antigen specific-CD4+and CD8+T cell response was detedted at as early as7dpv.These results indicate that the complete NSP has a positive effect on induction of specific-CD4+T andCD8+T cell responses of pigs in the early stages of the adaptive immune response.(3) Proliferative response of PBMC isolated from FMDV infected pigs and bovines to stimulationwith different NSP peptidesTo address the different immunogenicity of NSP from Re-Mya98/BY/2010and Mya98/BY/2010,14overlapping NSP peptides based on the sequence of FMDV strain Re-Mya98/BY/2010andMya98/BY/2010were synthesed and tested in proliferation assays using lymphocytes from pigs andbovine experimentally infected with different strains of FMDV. Peptides located on NSP3D and L wererecognized by PBMC from infected pigs while, peptides located on NSP3A(1493-1510) and L(2-11)induced a significant proliferative response in PBMCs isolated from FMDV-infected bovines,. The Tlymphocyte proliferative response stimulated by3A(1493-1510),3D(2001-2014) and L(2-11) wasdifferent with those stimulated by other peptides analyzed by statistical analusis (P<0.05). Thesignificant diffrernce was also observed on the amount of T lymphocytes stimulated by peptides whichare located in the same position of Re-Mya98/BY/2010and Mya98/BY/2010(P<0.05). To investigatethe immunogenicity of peptides located in Leader Proteinase, L(2-11) was immunized in infected pigswith FMDV, and the higher CD8+T cell response was observed compared to negative control (P<0.05).In conclusion, the results demonstrate that the recombinant FMDV Re-Mya98/BY/2010was ableto induce both strong humoral and cellular immune responses, supporting the concept that a role ofFMDV NSP in induction of the immune response. Furthermore, the results demonstrate thatrecombinant vaccines containing the capsid of field isolates can be successfully produced and is able toinduce protective immune responses.