Helper components of two potyviruses are serologically distinct.

The specificity of antisera to helper component (HC) from tobacco vein mottling virus (TVMV)- or potato virus Y (PVY)-infected tobacco plants was tested in immunoprecipitation and immunoabsorption chromatography experiments. Treatment with the homologous antiserum abolished or drastically reduced the activity of either TVMV-HC or PVY-HC, as measured by their ability to effect aphid transmission of purified tobacco etch virus, while the heterologous antiserum had little or no effect on HC activity. Loss of TVMV-HC and PVY-HC activity in the immunoabsorption chromatography experiments was associated with the removal of a 53- and a 58-kDa polypeptide, respectively. The results indicate that serologically distinct HC proteins are produced in response to specific potyvirus infection and suggest that HC is virus coded.