Full length articleA novel viral responsive protein (MjVRP) from Marsupenaeus japonicus haemocytes is involved in white spot syndrome virus infection

•A viral responsive protein of M. japonicus was cloned and characterized.•MjVRP is mainly expressed in haemocytes and located close to the nucleus of semi-granular and granular cells.•MjVRP mRNA expression level is increased after WSSV challenge.•The number of positive haemocytes was increased after WSSV challenge.

A viral responsive protein (MjVRP) was characterized from Marsupenaeus japonicus haemocytes. In amino acid homology and phylogenetic tree analyses, MjVRP clustered in the same group with the viral responsive protein of Penaeus monodon (PmVRP15), showing 34% identity. MjVRP transcripts were mainly expressed in haemocytes and the lymphoid organ. Western blotting likewise showed that MjVRP was strongly expressed in haemocytes and the lymphoid organ. Immunostaining detected MjVRP within the cytosol next to the perinuclear region in some haemocytes. Experimental challenge with white spot syndrome virus (WSSV) significantly up-regulated the mRNA level of MjVRP in the M. japonicus haemocytes at 6 and 48 h. Flow cytometry and indirect immunofluorescence assays revealed that the ratio of MjVRP+ haemocytes significantly increased 24 and 48 h post-WSSV infection. These results suggest that MjVRP+ haemocytes have a supporting role in the pathogenesis of WSSV.