Immune response in cattle inoculated with the recombinant complete polyprotein of foot-and-mouth disease virus from larvae.

The intact open reading frame (ORF) of foot-and-mouth disease virus (FMDV) Asia I/XJ strain was amplified by RT-PCR and inserted into the transfer vector pVL1393 to generate plasmid pVL-ORF. -N cells were transfected with pVL-ORF and linearized -BacPAK6 DNA, and the recombinant silkworm baculovirus -ORF containing the full ORF of FMDV was obtained. The results of indirect immunofluorescence assay (IFA) showed that -ORF could be expressed efficiently in -N cell. After inoculating the early 5th instar larvae of silkworm, the polyprotein of FMDV could be detected by sandwich ELISA and empty capsid-like particles could be observed under the electron microscope. Expression products from silkworm were used as the antigen to immunize the cattle. The specific antibody was induced in all vaccinated animals. The immunized cattle were challenged with the virulent FMDV Asia I/XJ strain, two of the four cattle were completely protected and clinical symptoms were alleviated and delayed in the others. The results suggest that this strategy might be used to develop the new subunit FMDV vaccine.