Comparative studies on tomato aspermy and cucumber mosaic viruses. VII. Serological relationships reinvestigated

Distant antigenic relationships between Australian strains of tomato aspermy virus (TAV) and cucumber mosaic virus (CMV) were investigated by three serological methods: radial double immunodiffusion in agar, enzyme-linked immunosorbent assays (ELISA), and immune-electron microscopy (IEM) using the antibody decoration technique. Based on the work with TAV and CMV presented in this paper, it appears that the ELISA method is especially suitable for studying antigenic relationships among viruses. For distinguishing closely related viruses, heterologous antibodies were used for both coating the ELISA plates and for conjugating with enzyme. On the other hand, for establishing distant antigenic relationships, heterologous and homologous antibodies were used for coating and coupling to enzyme, respectively. Immunodiffusion tests were less efficient than ELISA in distinguishing minor antigenic differences between strains of CMV and also, and distant relationship between TAV and CMV was not as clearly detected. Decoration of the virus particles with antibodies in IEM was the least satisfactory method for investigating antigenic relationships among the viruses.