Structure and immunogenic behaviour of methylated tobacco mosaic virus

Tobacco mosaic virus was methylated, using various concentrations of dimethylsulfate. The methylated virus sample with still intact particles was subjected to sequential analysis. The sites and the degree of methylation were determined in the tryptic peptides. Tyrosine 139 and cysteine 27 are more accessible to methylation than tyrosine 72, lysine 68 and tyrosine 2. A limited number of carboxyl groups was also methylated. The ability of methylated and original tobacco mosaic virus to initiate the formation of humoral antibodies and the capacity to induce a delayed-type hypersensitivity reaction were investigated in STU mice. Original tobacco mosaic virus could not induce a delayed-type hypersensitivity reaction but methylated tobacco mosaic virus induced a delayed-type reaction, not depending on whether the virus particles were intact or disintegrated. This phenomenon was strictly linked with the presence of methylester groups.