Immunodiagnosis of bunchy top viruses in abaca with polyclonal antibodies against their recombinant coat proteins.

Polyclonal antibodies against abaca bunchy top virus (ABTV) and banana bunchy top virus (BBTV) proteins are necessary for immuno-based detection of these two viruses in abaca (Musa textilis Nee). In this study, recombinant bunchy top viral coat proteins fused with a 6xHis tag at the N-terminus were expressed in E. coli BL21StarTM(DE3)pLysS strain and purified under denaturing conditions. Purified recombinant ABTV and BBTV coat proteins were used as antigens for the production of rabbit polyclonal antibodies. IgG was purified and evaluated by Direct Antigen Coating (DAC)-ELISA and further optimized by testing primary to secondary antibody dilution combinations. Analysis of ABTV and BBTV-infected abaca samples using the optimized DAC-ELISA assay showed that the anti-ABTV CP IgG can react to BBTV and that anti-BBTV CP IgG can react to ABTV, hence, a cross-reaction. The study demonstrates the advantage of using recombinant DNA technology for mass production of antigens for antibody production. Although specificity of the polyclonal antibodies may have been compromised when renatured recombinant proteins were used as immunogens, the ability of the purified IgGs to detect positive abaca samples reveals that the DAC-ELISA can be routinely used for screening disease-free abaca planting materials. [ABSTRACT FROM AUTHOR]