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Aim: From the different recombinants of FMDV antigen epitope, the highest antigenicity one was selected, and that provided research foundation for making researches on FMD plant-based vaccines which could effectively induce cell immune response and be characterized by high eurytopicity., Methods: The single-chain DNA of 5 T-cell epitope genes and 2 B-cell epitope genes were synthesized. By gene splicing by overlap extension technique, 5 T-cell epitope genes were fused together into T and 2 B-cell epitope genes were fused together into B. With Ava III and Pst I which produced uniform stickiness terminal, T and B were fused into recombinats in which T and B existed in different position, namely 5'-T-B-T-3', 5'-T-T-B-3' and 5'-B-T-T-3'. With potato X virus expression vector (PVX) every antigen gene (T, B, T-B-T, T-T-B, B-T-T and VP1) was expected to be expressed in leaves of tobacco. RT-PCR analysis and conformed whether all of the antigen genes were transcribed. Indirect ELISA Western Dotblot conformed analysed the antigeni-city of these products., Results: Every antigen genes were expressed successfully. The different products had different antigenicity, and 5'-T-B-T -3' was highest, 5'-B-T-T-3' was the second, and 5'-T-T-B-3' was lowest, but 5'-T-T-B-3' was higher than VP1, T or B., Conclusion: It is possible that gene engineering vaccine against FMDV with high eurytopicity and the induction of cell-immune response could be obtained by the different fusion ways with T and B cell epitopes existing in different position of recombinats, and that could have effect on immune activity of vaccines.

Total RNA was extracted from infected papaya (Carica papaya L.) leaves in Hainan Province, and the full-length sequences of papaya ringspot virus were amplified by RT-PCR and RACE, and its complete genomic sequence was assembled, named Hainan-P isolate. The RNA genome sequence of Hainan-P isolate was 10323 nucleotides (nts)in length,excluding the 3'-terminal poly(A) tail. And it was composed of a single open reading frame encoding a polyprotein of 3343 amino acids.. The result of homology analysis with twelve GenBank PRSV isolates showed that the polyprotein identity of Hainan-P ranged from 89. 8% to 93.2%, that was higher than the complete nt homology of 82.3% to 89.1%. The P1 amino acid was the least conserved (sharing homology only between 65.4% and 80.1%), whereas HC-Pro, CI and CP were the most conserved. Phylogenetic tree were constructed by the Neighbor-joining method in MEGA 3.1, which showed that PRSV isolates were obviously relevant to geographical origin, and it was impossible to delineate host-specific (P type and W type)evolution.

Most plant viral genome is relatively small and easy for genetic manipulation and inoculation. Therefore, plant viral vectors are attractive tools for expression foreign genes in plants. This paper reviews two basic types of epitope presentation and polypeptide expression systems, and discusses the development and application prospect of plant virus vector.