Identification and characterization of an envelope protein 168L in Cherax quadricarinatus iridovirus (CQIV)

Cherax quadricarinatus iridovirus (CQIV), a new member of family Iridoviridae, mainly infects the shrimps and crayfish with a high mortality rate. Previous gel-based LC-MS/MS study on CQIV has identified 30 structural proteins. In this study, one of the structural proteins, CQIV-168L, was selected for further analysis. RT-PCR and Western-blotting (WB) detection revealed that the transcript and the protein appeared late during infection of C. quadricarinatus cells and that the transcript was blocked by viral DNA replication inhibitor, indicating that CQIV-168L is a late expression gene. The specific antiserum against CQIV-168L was raised and immunofluorescence analysis showed that CQIV-168L was localized in the cytoplasm and associated with virus factories. Western-blotting (WB) assay suggested that CQIV-168L antiserum bound specifically to a 57-kDa protein in both the intact virions and the envelope fraction. As revealed by immunogold labeling, CQIV-168L was a component of the viral envelope. Findings in this work help to further understand the structure and entry mechanism of CQIV.