Extracellular virion proteins of two Chinese CyHV-3/KHV isolates, and identification of two novel envelope proteins

•Extracellular virion proteins of two Chinese CyHV-3/KHV isolates were determined.•A total of 43 viral proteins were detected in purified CyHV-3/KHV virions.•A total of 27 cellular proteins were detected associated with purified CyHV-3/KHV.•pORF83 and VISP were identified as two novel envelope proteins in CyHV-3/KHV virions.

Proteins in extracellular virions of two Chinese cyprinid herpesvirus-3/koi herpesvirus (CyHV-3/KHV) isolates were identified through one-dimensional gel-based matrix-assisted laser desorption/ionization tandem time of flight mass spectrometry in combination with liquid chromatography tandem mass spectrometry (LC ESI-MS/MS). A total of 43 viral proteins were identified, seven of which (pORF62, 68, 43, 51, 92, 84, and 72) were characterized as marked characteristic viral proteins in CyHV-3/KHV virions and six of which (pORF11, 27, 83, 91, 106 and 116) were not detected previously. Of the newly identified proteins, pORF83 was identified as a novel viral minor envelope protein by Western blot analysis and indirect immunofluorescence assay. Another 27 cellular proteins were validated by LC ESI-MS/MS to be involved in purified extracellular CyHV-3/KHV virions, among which a highly abundant, virus-inducible stress protein was shown and characterized as a cell-derived envelope protein in CyHV-3/KHV virions. Our study extends the number of known CyHV-3/KHV virion-associated viral proteins from 40 to 46 and identifies a novel viral envelope protein as well as a cellular envelope protein. The present findings provide some new insights for better understanding CyHV-3/KHV.