Production of recombinant capsid protein of Macrobrachium rosenbergii nodavirus (r-MCP43) of giant freshwater prawn, M. rosenbergii (de Man) for immunological diagnostic methods.

White tail disease (WTD) caused by Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) is a serious problem in prawn hatcheries. The gene for capsid protein of MrNV (MCP43) was cloned into pRSET B expression vector. The MCP43 protein was expressed as a protein with a 6-histidine tag in Escherichia coli GJ1158 with NaCl induction. This recombinant protein, which was used to raise the antiserum in rabbits, recognized capsid protein in different WTD-infected post-larvae and adult prawn. Various immunological methods such as Western blot, dot blot and ELISA techniques were employed to detect MrNV in infected samples using the antiserum raised against recombinant MCP43 of MrNV. The dot blot assay using anti-rMCP43 was found to be capable of detecting MrNV in WTD-infected post-larvae as early as at 24 h post-infection. The antiserum raised against r-MCP43 could detect the MrNV in the infected samples at the level of 100 pg of total protein. The capsid protein of MrNV estimated by ELISA using anti-rMCP43 and pure r-MCP43 as a standard was found to increase gradually during the course of infection from 24 h p.i. to moribund stage. The results of immunological diagnostic methods employed in this study were compared with that of RT-PCR to test the efficiency of antiserum raised against r-MCP43 for the detection of MrNV. The Western blot, dot blot and ELISA detected all MrNV-positive coded samples as detected by RT-PCR.