A NONAMER PEPTIDE DERIVED FROM LISTERIA-MONOCYTOGENES METALLOPROTEASEIS PRESENTED TO CYTOLYTIC T-LYMPHOCYTES

Listeria monocytogenes is an intracellular bacterium that secretes pro teins into the cytosol of infected macrophages. Major histocompatibili ty complex (MHC) class I molecules bind peptides that are generated by the degradation of bacterial proteins and present them to cytolytic T lymphocytes (CTL). In this study we have investigated CTL responses i n L. monocytogenes-immunized mice to peptides that (i) derive from the L. monocytogenes proteins phosphatidylinositol-specific phospholipase C, lecithinase (most active on phosphatidylcholine), metalloprotease (Mpl), PrfA, and the ORF-A product and (ii) conform to the binding mot if of the H2-K-d MHC class I molecule. We identified a nonamer peptide , Mpl 84-92, that is presented to L. monocytogenes-specific CTL by H2- K-d MHC class I molecules. Unlike other motif-conforming peptides deri ved from the secreted Mpl oft. monocytogenes, Mpl 84-92 is bound with high affinity by H2-K-d. Mpl 84-92 is the fourth L. monocytogenes-deri ved peptide found to be presented to CTL by the H2-K-d molecule during infection and demonstrates the importance of high-affinity interactio ns between antigenic peptides and MHC class I molecules for CTL primin g.