Characterization of the specificity and genetic restriction of human CD4(+) cytotoxic T cell clones reactive to capsid antigen of rubella virus

Using 11 overlapping synthetic peptides covering more than 95% of the amino acid sequence of capsid protein of rubella virus, 7 CD4(+) T cell clones (R10, R11, R18, A2, A10, A1, and A12) isolated from 2 rubella seropositive donors reacted strongly to rubella capsid peptides C6 (residues 119–152), C9 (residues 205–233), or C11 (residues 255–280), respectively, in both proliferation and cytotoxicity assay. Truncated peptides C6E (residues 125–139), C9B (residues 205–216), and C11E (residues 260–272) were shown to be involved directly to the T cell determinants of C6, C9, and C11, respectively. Genetic restriction of these T cell clones was analyzed by using human cell lines with various HLA-DR phenotypes as targets and/or antigen-presenting cells in cytotoxicity assay and/or proliferation assays. The results indicated that the recognition of peptide C6 by T cell clones (R11 and R18) was associated with DRw9 molecule, while the HLA restriction element of the responses of other T cell clones (A2 and A11, A10, and A12) that reacted with peptide C9 or C11 was DR4 molecule. However, there may be a cross-recognition by the T cell clone (A12) between DR1 and DR4 subtypes.