Proteomic analysis and white spot syndrome virus interaction of mud crab (Scylla olivacea) revealed responsive roles of the hemocytes.

White spot disease (WSD) is a highly virulent viral disease in shrimps. Clinical signs and high mortality of WSD is generally observed after a few days of infection by White Spot Syndrome virus (WSSV). Mud crabs are the major carrier and persistent host for the WSSV. However, an elucidation of viral interaction and persistent mode of WSSV infection in mud crab is still limited. We investigated the defensive role of mud crab (Scylla olivacea) hemocytes against WSSV infection by using comparative proteomic analysis coupled with electrospray ionization liquid chromatography tandem mass spectrometry (ESI-LC/MS/MS). The proteomic maps of expressed proteins obtained from WSSV infected hemocytes revealed differential proteins related to various biological functions, including immune response, anti-apoptosis, endocytosis, phosphorylation signaling, stress response, oxygen transport, molting, metabolism, and biosynthesis. Four distinctive cell types of crab hemocytes: hyaline cells (HC), small granular cells (SGC), large granular cells (LGC) and mixed granular cells (MGC) were found susceptible to WSSV. However, immunohistochemistry analysis demonstrated a complete replication of WSSV only in SGC and LGC. WSSV induced apoptosis was also observed in HC, SGC and MGC except for LGC. These results suggested that HC and MGC may undergo apoptosis prior to a complete assembly of virion, while SGC is more susceptible showing higher amplification and releasing of virion. In contrast, WSSV may inhibit apoptosis in infected LGC to stay in latency. This present finding provides an insight for the responsive roles of crustacean hemocyte cells involved in molecular interaction and defense mechanism against WSSV.