Although it is known that rubella-immune individuals have T cells that proliferate in vitro in response to rubella virus (RV), the determinants that evoke this response have not been identified. This study utilized recombinant proteins that express overlapping sequences of the RV structural open reading frame to identify domains of the structural proteins that contain cell-mediated immunodominant sequences. Lysates enriched with RV fusion proteins (RecA-RV-LacZ) were prepared from Escherichia coli transformed with plasmids which contained specific RV cDNA inserts. Approximately 62% of RV-immune individuals gave RV-specific responses to one or more of the RV fusion proteins. Over 10% of immune individuals recognized the capsid sequence C1-C29. Lymphoproliferation data from studies using six overlapping synthetic peptides representing this sequence suggested that as much as 70% of the immune population may recognize this domain. An E1 sequence, E1202-E1283 was recognized by 15% of the RV-immune individuals with the fusion proteins. Five synthetic peptides representing this sequence had an overall response rate of 50%. The sequence C64-C97 failed to evoke any RV-specific responses with the fusion proteins and synthetic peptides representing this sequence were used to verify that the RV fusion proteins and the criteria used to identify RV-specific responses were adequate. These peptides gave a response rate of only 6%. In general, significant responses to specific fusion proteins correlated with high responses (stimulation index ≥ 4.0) to representative synthetic peptides. This study suggests that the recombinant proteins were beneficial in identifying cell-mediated immunodominant domains of the RV structural proteins which could be further characterized with synthetic peptides.
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