Characterization and Antibody Preparation of the Gene Products of Grouper Iridovirus <i>ORF5L</i>

ABSTRACT Grouper iridovirus (GIV) is a large DNA virus belonging to the family Iridoviridae and genus Ranavirus . It consists of 139,793 base pairs (bp) and 120 open reading frames (ORFs). GIV is a key pathogen of farmed fish worldwide. The functional roles of viral genes must be determined for the early diagnosis, treatment and prevention of viral infections. This study explored the characteristics of GIV‐5L during viral infection. Sequence analysis of GIV‐5L was performed using the National Center for Biotechnology Information (NCBI) database, leading to preliminary speculation that GIV‐5L is a viral protein unique to Ranavirus . GIV‐5L recombinant protein was used to immunize mice to obtain polyclonal antibodies against GIV‐5L. The expression characteristics of the GIV‐5L gene were then analysed. Gene expression time was analysed using cycloheximide (CHX) and cytosine arabinoside (AraC) during the infection of grouper kidney (GK) cells with GIV. GIV‐5L expression was inhibited by CHX and AraC, confirming their role as late genes. Immunofluorescence staining confirmed GIV‐5L expression in the cytoplasm at 12‐hours post‐infection (hpi) and in the nucleus at 24 hpi. This study demonstrated the functional characteristics of the GIV‐5L gene, which could provide insights into GIV assembly and facilitate GIV diagnosis.