The serology of the bromoviruses. I. Serological interrelationships of the bromoviruses.

The serological relationships between brome mosaic (BMV), cowpea chlorotic mottle (CCMV), and broad bean mottle (BBMV) viruses, and their coat proteins, were studied by gel precipitin, "rocket immunoelectrophoresis" (RIE), and enzyme-linked immunosorbent assay (ELISA) techniques. Gel precipitin and RIE tests indicated that capsid swelling altered the antigenicity of both BMV and CCMV, as although the coat proteins were serologically related at both pH 6.0 and pH 7.0, the viruses appeared to be related only when swollen at pH 7.0. Fixation of the viruses with 2% formaldehyde at pH 6.0 appeared to remove the relationship. BBMV was not related by precipitin tests to either BMV or CCMV but was related to both by direct and indirect ELISA at both pH 6.0 and pH 7.4, though less closely than BMV and CCMV were related to each other. Indirect ELISA showed the three coat proteins to be more closely related than the parent viruses. Formalinized BMV and CCMV appeared less related than the native viruses at pH 6.0. Sandwich ELISA proved too strain specific to show any group relationships. The implications of these results and a serological map proposed for the bromoviruses are discussed.