Demonstration of virus-specific CD8+ memory T cells in measles-seropositive individuals by in vitro peptide stimulation.

CD8+ cytotoxic T lymphocytes (CTL) in measles virus infection have been difficult to investigate due to the strong immunosuppressive effects exhibited by infectious measles virus in vitro. In order to circumvent immunosuppression we used predicted peptide epitopes to induce measles virus-specific CTL. This was done by screening the structural proteins of measles virus for HLA-A2.1 peptide-binding motifs with valine in position 2 and leucine in position 9. Synthetic peptides np210-218, np226-234, and np340-348 from the nucleoprotein, peptide hp29-37 from the haemagglutinin protein, and peptide pp 519-527 from the polymerase protein were synthesized and used to expand measles virus-specific CD8+ CTL in vitro. Induction of CTL with synthetic peptides was restricted to HLA-A2-positive peripheral blood mononuclear cells (PBMC) from measles-seropositive individuals. We conclude that this method is a useful tool to demonstrate memory CD8+ CTL in measles-seropositive adults and to evaluate the role of structural proteins in CTL responses against measles.