Plants Provide Diagnostic Reagent for West Nile Virus

A plant expression system has been investigated for protein production due to its low-cost and high-scalability nature and its ability to make appropriate posttranslational modifications.
Scientists at Arizona State University (Tempe, AZ, USA) explored the feasibility of using plant transient expression systems to produce two groups of protein reagents that are required for the detection and diagnosis of WNV infection. One was a recombinant antigen derived from the domain III (DIII) of WNV envelope (E) protein and the second, a monoclonal antibody (mAb E16) that specifically recognizes WNV DIII.

High expression levels of both reagents were observed in two kinds of plants: Nicotiana benthamiana, which is a close relative of tobacco, and lettuce. The two reagents may be readily purified to greater than 95% and retain their native functionality and specificity. The binding specificity of plant-derived E16 at various concentrations of this mAb were incubated with either DIII of WNV or DIII of Dengue virus serotype 2 (DENV-2) that was immobilized on an enzyme linked immunosorbent assay (ELISA) plate. A mammalian cell-culture-derived E16 and a generic human immunoglobulin G (IgG) (Southern Biotech, Birmingham, AL, USA) were used as the positive and negative control, respectively.

The binding to WNV DIII increased with the concentration of lettuce or N. benthamiana-derived E16 in the reaction in a similar manner as the mammalian cell-derived E16 positive control. In contrast, none of the E16s showed specific binding to DIII of DENV-2. The negative control, a generic human IgG, showed no specific binding to either WNV or DENV-2 DIII. These results indicate that the specific avidity for WNV DIII is retained by the plant-derived E16s. This high specificity makes it a valuable reagent in obtaining unambiguous diagnostic results for detecting WNV and WNV infection.

Qiang Chen, PhD, the senior author said, “Our test will improve the accuracy of diagnosis, leading to the proper treatment of patients affected by WNV. The plant-derived monoclonal antibody we examined is not only low-cost, but highly specific for WNV antigen and does not recognize antigens from other flaviviruses.” The study was published in the October 2012 issue of the Journal of Biomedicine and Biotechnology.

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Arizona State University
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