The Efficacy Of Recombinant Vaccines Against White Spot Syndrome Virus In Crayfish (Procambarus Clarkii)

The efficacy of oral, injection, and immersion recombinant vaccines were studied against white spot syndrome virus(WSSV) in crayfish(Procambarus clarkii). The most exposed WSSV envelope proteins VP19 and VP28 were expressed in prokaryotic(Escherichia coli BL₂₁) and eukaryotic(Pichia pastoris GS115) expression systems and used as recombinant vaccine agents.The White Spot Syndrome Virus genome was purified; the genes(VP19 and VP28) were amplified, cloned, expressed and sequenced. The obtained sequences of VP19 and VP28 were deposited in the Gene Bank as accession numbers DQ007314 and DQ007315 respectively. The BLAST analyses of the sequences showed 98% and 100% homology in VP19 and VP28 respectively with already published sequences. The proteins of VP19 and VP28 were purified and expressed and showed bands with sizes of 21 kDa(VP19) and 28 kDa(VP28) in SDS-PAGE and Western Immunoblotting in prokaryotic expression system. In eukaryotic expression system, proteins VP19 and VP28 expressed successfully and showed bands with sizes of 22 kDa(VP19) and 35kDa(VP28) in SDS-PAGE and Western Immunoblotting respectively.The purified proteins were used as vaccine components. The purified proteins were mixed with food pellets and fed to experimental crayfish for 25 days as oral vaccines. The purified proteins were mixed with 330mM NaCl and injected intramuscularly followed by booster shot as injection vaccine and crayfish immersed in the solution and followed by booster shot as immersion vaccine. The mode of challenge was oral and the mortality was observed for 25 days. The relative percent survival(RPS) value of injection vaccine(91%) was found to be the best and followed by oral(86%) and immersion(63%) vaccine. Among vaccine groups, the RPS values of VP28(91%) and VP19 and VP28 in combination(84%) were found significantly differed(>60%) from VP19(45%) and control groups. The RPS values of vaccines expressed in eukaryotic system(Injection 91%, oral 86%, and immersion 63%) were significantly differed(>60%) over those expressed in prokaryotic system (Injection 55%, oral 52% and immersion 49%). It has been found that vaccination in crayfish against white spot syndrome viral disease is feasible. The present investigation also showed the necessity of in depth research on virus-host interaction to formulate an efficient vaccination programme and selection of appropriate expression system.