| Abstract
| - The efficient and sustained immune response of an antigen requires T cell epitopes, capable of inducing a long lasting T cell memory. To detect T cell epitopes of the measles virus fusion protein (MV-F), the proliferation of lymphocytes from late convalescent donors in response to overlapping pentadecapeptides covering the whole protein sequence was studied. Three major immunodomlnant regions (F51-70, F121-135 and F211-225) containing promiscuous peptides Induce proliferation in peripheral blood lymphocytes in ˜50% of the donors. Potential DR1- restricted epitopes were mapped using an MHC competition binding assay. Both the proliferation and the binding data identified a DR1 -restricted T cell epitope (F51-65). Contact sites of the peptide HQSLVIKLMPNITLL with MHC were characterized using substitution analogs. Alanine substitutions at most positions did not interfere with F51-65 binding. These analogs were therefore useful for studying the residues which were recognized by the TCR of MV- and F51-lnduced T cells lines. In addition to amino acid residues of the core of peptide F51-65 both the C-terminal and the N- terminal amino acids were essential for T cell interaction. Since peptides presented by class II molecules vary In length, these findings suggest that residues of the ragged tail are Important for T cell activation. It Is speculated that In late convalescent donors the length of the flanking sequence of MHC II-restricted peptides may play a role In controlling the heterogeneity of MV-specifIc T cell clones recruited as T helper/memory cells.
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