Monoclonal antibodies (mAbs) and single chain variable fragment (scFv) antibodies targeting envelope protein VP28 of white spot syndrome virus provide protection against viral infection

White spot syndrome virus (WSSV) is extremely pathogenic and causes huge economic losses in the shrimp farming industry. Neutralizing antibodies against WSSV is expected to be an effective means of preventing infection with the virus. In the present study, eight monoclonal antibodies (mAbs) against VP28 were developed by immunizing BALB/c mice with WSSV-VP28 recombinant protein. Among them, three mAbs named 3B7, 2G3 and 5D2 were determined to be able to delay the mortality of WSSV-infected shrimp in vivo neutralization assay, suggesting their neutralizing ability against WSSV infection. Immunoblotting results showed that the three mAbs reacted specifically with native VP28 of WSSV, and could also recognize the virions in the gills of WSSV-infected shrimp by IFA. Furthermore, the single chain variable fragment (scFv) genes specific for WSSV-VP28 were cloned from the three hybridoma cells and expressed in Escherichia coli. After purification and refolding, three biolog-ically active scFv recombinant proteins were all capable of recognizing the native VP28 of WSSV and delayed the mortality of WSSV-infected shrimp, indicating their neutralizing capacity against WSSV. Subsequently, the eukaryotic expression plasmids of three scFv genes were constructed and the transcriptional properties of expression vectors in shrimp were analyzed. Animal experiments also proved that the scFv eukaryotic expression plasmids were able to partially neutralize WSSV infection. Thus, the production of neutralizing mAb and re-combinant scFv antibodies against WSSV has a promising therapeutic potential in prevention and treatment of white spot disease of shrimp.

Automated summary

In this study, eight monoclonal antibodies (mAbs) against VP28 of WSSV were developed, and three of them were determined to have the ability to delay mortality in WSSV-infected shrimp. These mAbs specifically reacted with native VP28 of WSSV and recognized the virions in the gills of infected shrimp. Three biologically active single chain variable fragment (scFv) recombinant proteins were produced and capable of recognizing native VP28 and delaying the mortality of WSSV-infected shrimp. Eukaryotic expression plasmids of scFv genes were constructed and partially neutralized WSSV infection. Therefore, the production of neutralizing mAbs and recombinant scFv antibodies against WSSV shows promising therapeutic potential in preventing and treating white spot disease of shrimp.