Fusion Proteins Cpn10-E^(rns) with Properties of Generating CSFV-Neutralized Antibodies

When pigs are infected with classical swine fever virus （ CSFV）, the antibody primarily targets the structural giycoprotein E^rns of the virus. Previous investigations have demonstrated that ETM has low or no virus neutralizing capacity. In this study, candidate subunit marker vaccine, chaperonin 10 （Cpnl0）-E^rns, which possess the property of generating neutralized antibodies against lethal challenge of virulent CSFV was developed. The gene of ETM was isolated from Hog cholera lapinized virus （HCLV） -infected spleen cells of rabbits via RT-PCR method and fused to the downstream region of the cpn10 gene; the products of recombinant fusion protein （ cpn10-E^rns ） induced expression in Escherichia coli, and the products were purified by affinity chromatography. During the course of vaccination, the candidate vaccines cpn10-E^rns were used for the immunization of guinea pigs, and they induced a strong antibody response against cpn10-E^rns. The antibodies can be immobilized by coating inactivated CSFV particles, indicating that these antibodies can recognize CSFV. Neutralization assay was carried out on rabbits according to National Regulations on Veterinary Drug. The results clearly indicate that the typical fever of rabbits induced by the live attenuated HCLV could be inhibited by preincubation with the antisera （dilution 1： 4） induced by cpn10-E^rns, but not inhibited by preincubation with the antisera induced only by E^rns. Analogous results were observed for the group of the rabbits immunized with cpn10-E^rns, which were protected against the typical fever induced by the challenge with HCLV. The findings of this study formed the basis of a new means for developing subunit marker vaccine against CSFV.

Preliminary Evaluation of a Candidate Multi-Epitope-Vaccine Against the Classical Swine Fever Virus

A multi-epitope-vaccine MEVABc consisting of two linear neutralizing determinants （BCI： aa693-716; A6： aa844-865） located on antigenic unit B/C and unit A of glycoprotein E2 was prepared to evaluate whether a combination strategy is effective in the design of peptide vaccines. After immunization, pig sera collected every one to two weeks were evaluated by enzyme linked immunosorbent assay. C-straininduced anti-sera and hyper-immune sera cannot recognize overlapping peptides that cover the E2 N-terminus, while MEVAgC is able to elicit high levels of peptide-specific antibody response. When compared with previously studied peptide vaccines PV-BC1 and PV-A6, the same dose of either component in the MEMABc increases the BC1- or A6-specific antibodies （to 1/3-1/2 of the levels of the separate vaccines）. However, the synergy between the antibodies may make MEVAgc much more potent. Moreover, anti-C-strain immunity pre-existing in pigs does not disturb the sequent MEVABc vaccination. Thus, MEVABc can be administrated to pigs which already possess anti-classical swine fever virus immunity. MEVAgC is a promising candidate marker vaccine.