Development of Recombinant Coat Protein Antibody Based IC-RT-PCR and Comparison of its Sensitivity with Other Immunoassays for the Detection of Papaya Ringspot Virus Isolates from India

Abstract

Papaya ringspot virus (PRSV) causes the most widespread and devastating disease in papaya. Isolates of PRSV originating from different geographical regions in south India were collected and maintained on natural host papaya. The entire coat protein (CP) gene of Papaya ringspot virus-P biotype (PRSV-P) was amplified by RTPCR. The amplicon was inserted into pGEM-T vector, sequenced and sub cloned into a bacterial expression vector pRSET-A using a directional cloning strategy. The PRSV coat protein was over-expressed as a fusion protein in Escherichia coli. SDS-PAGE gel revealed that CP expressed as a ~40 kDa protein. The recombinant coat protein (rCP) fused with 6x His-tag was purified from E.coli using Ni-NTA resin. The antigenicity of the fusion protein was determined by western blot analysis using antibodies raised against purified PRSV. The purified rCP was used as an antigen to produce high titer PRSV specific polyclonal antiserum. The resulting antiserum was used to develop an immunocapture reverse transcription-polymerase chain reaction (IC-RT-PCR) assay and compared its sensitivity levels with ELISA based assays for detection of PRSV isolates. IC-RT-PCR was shown to be the most sensitive test followed by dot-blot immunobinding assay (DBIA) and plate trapped ELISA.