Expression and polymerization of Ostreid herpesvirus 1 structural proteins with eukaryotic expression system

Ostreid herpesvirus 1 (OsHV-1) infection has been linked to mass mortality of cultivated mollusks of different species worldwide. In this study, we established a eukaryotic system for the expression of ORF104 and ORF33 of OsHV-1, and investigated the polymerizing characterization of ORF104 and ORF33. Firstly, the biochemical characteristics, typical domains and 3D structures were analyzed bioinformatically. Secondly, we constructed recombinant plasmids for the two genes, and individually transfected or co-transfected them into Human Embryonic Kidney Cells (HEK293t). Finally, the expression and polymerization of the two target proteins were investigated using Western Blot (WB) and electron microscopy. Bioinformatic analysis demonstrated that hydrophilicity of ORF33 and ORF104 were −0.49 and 0.82, making them stable hydrophilic and hydrophobic proteins respectively. For the construction of recombinant plasmids, genes of ORF33 and ORF104 were amplified with specifically designed primers, which generated PCR products of about 1 000 bp and 3 500 bp for ORF33 and ORF104 respectively. The recombinant plasmids were transmitted into HEK293t cells using Lipo8000^TM for expression. The target bands around 140 ku and 35 ku in length were obtained by WB analysis after SDS-PAGE. However, the interaction between the two viral proteins was still undetermined. The ORF104 protein was identified by electron microscopy, which has a diameter of approximately 20 nm. Due to the small diameter of ORF33, it could not be clearly resolved with the background particles under negative staining electron microscopy in the present study. When the products of the two co-transfected plasmids were investigated, the diameter of the particles was between 10 and 30 nm. In summary, we established a method for the expression of OsHV-1 structural proteins using the eukaryotic expression system for the first time. Polymerization of the two proteins individually and together was investigated and characterized. The method described here provides a new approach for further research on the function, interaction of structural proteins, and infection mechanisms of OsHV-1.