| White spot syndrome virus (WSSV), is one of the most virulent pathogens, causing highmortality and dramatic economic losses in cultured shrimp worldwide. Up to date no effectivemeasuer is available to pervent the spreading of WSSV. Therefore, it is urgent to fred aneffective method to control this pathogen.Chicken egg yolk immunoglobulin (IgY) provides an inexpensive and effective source ofantibodies for the passive immunization of animals suffering from different kinds of diseases.It is a promising immunity preparation for the treatment and prevention of aquatic diseases.In this study, WSSV were separated from infected crayfish. The major antigen regiongene VP28, VP19, VP15 of WSSV were amplified by PCR, and then linked together byoverlap extension PCR with the designed linkers as overlap regions. The fusion gene wascloned into the eukaryotic expression plasmid pCI, and then pCI-28-19-15 DNA vaccine wassucessfuly constructed. The HeLa cells were transfected by DNA vaccine and the expressionof fusion gene was detected by indirect immunofluorescence assay (IFA). The results showedthat the fusion gene obtained functional expression in HeLa cells.Subsequently, the DNA vaccine and formalin-killed WSSV were used as antigens toimmunize laying hens for the production of IgY specific to WSSV. And the activity of IgYwas detected by indirect enzyme-linked immunosorbent assay (ELISA). The resultsdemonstrated that the activities of water-soluble fraction (WSF) of IgY specific to inactivatedWSSV (WSSV-IgY) and IgY specific to DNA vaccine with CpG ODNs as adjuvent(DNA-IgY) showed a significant difference compared with the control group. Furthermore,the CpG oligodeoxynucleotides (CpG ODNs) enhanced the immune response of DNA vaccinesignificantly.The protective effects of IgY powder and egg yolk powder against WSSV in thecrayfish (Procambarus clarkii) were evaluated. In viral neutralization experiment byintramuscular injection, crayfish treated with WSSV-IgY and DNA-IgY power exhibitedmortalities of 20% and 80% at day 9 post-challenge with WSSV, respectively. In oraladministration experiment, those fed a diet containing 1％WSSV-IgY power and 10% eggyolk powder showed mortalities of 53.3 % and 67.7%, respectively. The WSSV-IgYimmersion group showed a mortality of 26.7%. These results have significantly differences compared to the positive control group which showed a mortality of 100% (P＜0.05). Theresults suggested that passive immunization of specific IgY antibodies through oraladministration and immersion were effective to protect crayfish against WSSV.In conclusion, the specific IgY preparation in this study can provide a novel approach tothe prevention and treatment of WSSV infection, which will have a industrial prospect.
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