Purification and serological detection of maize yellow mosaic virus

Maize yellow mosaic virus (MaYMV) is an emerging polerovirus that was first reported in maize in China in 2013 but has since been reported in Africa and the Americas. Due to its novelty, no antibodies or serological diagnostics for the virus existed prior to the current study. In this study, we developed the first purification method for maize yellow mosaic virus with the goal of generating an antibody and subsequently developing diagnostic tests. Yields of 0.634-1.275 milligrams of virus per kilogram of maize tissue were obtained, which is comparable to the yields obtained for other grass-infecting poleroviruses. Under an electron microscope, purified virus particles appear icosahedral in shape and roughly 30 nm in diameter. A polyclonal antibody was generated against the gradient-purified virus preparation and cross-adsorbed to uninfected maize tissue. The antibody is effective for detection of MaYMV via enzyme-linked immunosorbent assay (ELISA) and western blot. The ELISA could detect virus in quantities as low as 0.395 µg and in 1:32 dilutions of infected plant extract, and the antibody showed little to no cross-reactivity with five closely related viruses. After protein gel electrophoresis and antibody detection, protein bands corresponding in size to two viral structural proteins could be seen: the coat protein of roughly 21 kDa and the readthrough protein, around 72 kDa. Finally, virus particles purified using this protocol were found to be transmissible by the primary aphid vector, Rhopalosiphum maidis, and to cause systemic, symptomatic infection of maize plants, indicating that the vector transmissibility and infectivity of the virus particles were preserved during purification.