Establishment of CTL clones against HTV nucleus proyein and modulation of cytotoxic activity byamino acids substitution of an epitope peptide

Abstract

Cellular immune responses involve the activation of T cells by specific antigens. Thus, a central issue in understanding adoptive immunity is the means by which T cells recognize antigens. While antigen recognition by antibodies has been examined in molecular detail by X-ray crystallography, antigen recognition by T cells is still largely studied through the analysis of biological responses of T cells. The nature of T cell``s response to complexes formed by epitope peptides with MHC proteins can be greatly affected by alterations in the peptide``s amino acid sequence. Some peptides elicit agonistic responses; others elicit partial responses; and the principal effects of still others is to inhibit the activity of agonists, epitope peptides. These altered peptide ligands (APL) are of considerable interest because they provide the tools for exploring previously unappreciated complexities in the responses of T cells to antigens. To identify and characterize antagonistic peptides for the CD8+ cytotoxic T cell, CTL clones whose T cell receptor(TCR) recognize an epitope in the nucleus protein of Hantaan Virus(HTV) were used as a model system. Although neutralizing antibodies against Hantaan virus can protect host from viral infection, T cell responses to HTV are also regarded important in host defense against HTV. But much less is known about the cytotoxic T lymphocyte(CTL) responses to HTV. In order to identify CTL epitopes in the HTV nucleocapsid protein(NP), we selected seven H-$2K^b$-motif-fitting peptides. Out of these peptides, 3 peptides(NP3,NP4,and NP7) were recognized by CTL responses derived from HTV-immunized mouse splenocytes. NP3 and NP4 peptide were also recognized by HTV-immunized splenocytes after secondary in vitro stimulation with the relevant peptide, but NP7 could not be recognized after in vitro stimulation. These results agree well with peptide-immunization studies showing that peptide-specific CTL responses could be induced with NP3 and NP4 but...