Enhanced in vitro potency and in vivo immunogenicity of a CTL epitope from hepatitis C virus core protein following amino acid replacement at secondary HLA-A2.1 binding positions.

Abstract

Since the natural immune response to hepatitis C virus (HCV) is often unable to clear the infection, to enhance immunogenicity we studied substituted peptides from an HCV cytotoxic T lymphocyte (CTL) epitope (C7A2) from a conserved region of the HCV core protein (DLMGYIPLV) recognized by CTL lines from HLA-A2.1 ϩ HCV-infected patients and HLA-A2.1 transgenic mice. HLA-A2.1 binding, human and murine CTL recognition, and in vivo immunogenicity (using mice transgenic for human HLA-A2 in lieu of immunizing humans) were analyzed to define peptides with enhanced immunogenicity. Peptides substituted at position 1 showed enhanced HLA-A2 binding affinity, but paradoxically poorer immunogenicity. A peptide with Ala substituted at position 8 (8A) showed higher HLA-A2 binding affinity and CTL recognition and was a more potent in vivo immunogen in HLA-A2-transgenic mice, inducing higher CTL responses with higher avidity against native C7A2 than induced by C7A2 itself. These results suggest that peptide 8A is a more potent in vitro antigen and in vivo immunogen than C7A2 and may be useful as a vaccine component. They provide proof of principle that the strategy of epitope enhancement can enhance immunogenicity of a CTL epitope recognized by human CTL. ( J. Clin. Invest.

Immunotherapy: past, present and future

“…Therefore, immunotherapies have been enhanced by the modification of the antigenic peptide by epitope engineering. This involves altering the antigen to increase its affinity for MHC molecules by taking advantage of known sequence motifs for peptide binding to the anchor residues that are involved in MHC binding 2,4,32,33 . In one strategy, a combinatorial library is used to screen sequences for improved MHC binding 34 .…”

Availability of a Diversely Avid CD8+ T Cell Repertoire Specific for the Subdominant HLA-A2-Restricted HIV-1 Gag p2419–27 Epitope

“…Cells were then stained with anti-HLA-A2 BB7.2 mAb, followed by a secondary FITClabeled goat anti-mouse IgG Ab for analysis by flow cytometry (55,56). The binding activity of each peptide was calculated as a fluorescence ratio (mean fluorescence intensity (MFI) of T2 incubated with peptide/MFI without peptide).…”

Tumor Eradication by Hepatitis B Virus X Antigen-Specific CD8+ T Cells in Xenografted Nude Mice

“…Peptide binding to HLA-A2 molecules was measured using the T2 mutant cell line according to a protocol described previously (21). T2 cells (5 ϫ 10 5 /well) were incubated overnight with different concentrations of peptide in 96-well plates with culture medium (RPMI 1640 containing 10% FBS, 4 mM glutamine, 100 U/ml penicillin, and 100 g/ml streptomycin).…”