Production of polyclonal antibodies for Capsicum chlorosis virus (CaCV) infecting chilli in India through recombinant nucleocapsid protein expression and its application

Bud necrosis and chlorotic spots causing virus affecting chilli crop in Tamil Nadu (India) was identified as Capsicum chlorosis virus (CaCV). Specific primers were used for amplification and sequencing of the nucleocapsid protein (NP) gene. Polyclonal antibody against the bacterially expressed NP from the CaCV-TN-CBE isolate was produced using recombinant DNA technology. NP gene was subcloned into the pET-28a (+) vector and expressed by transformation in BL21 (DE3) pLysS. The expressed protein was about ∼34 kDa and was confirmed through western blot analysis using Groundnut bud necrosis virus (GBNV) polyclonal antiserum from ICRISAT, India. The purified recombinant protein was used to immunize rabbits to generate CaCV-specific polyclonal antiserum. The sensitivity levels of polyclonal antiserum thus raised was assayed through indirect ELISA or direct antigen coating (DAC)-ELISA using the recombinant protein as antigen. The recombinant antiserum produced in this study successfully detected the natural infection of CaCV on chilli plants collected from the field as well as on cowpea plants artificially inoculated with CaCV by using DAC-ELISA, DIBA and western blotting.