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DNA vaccination offers a strategy to induce immune attack on cancer cells, but tumor Ags are often weak. Inclusion of a "foreign" protein increases immunogenicity, and we found previously that fusion of the fragment C (FrC) of tetanus toxin to the tumor Ag sequence promotes Ab and CD4(+) responses against B cell tumors. For CTL responses, use of the full two-domain FrC may be less helpful, because known immunogenic MHC class I-binding peptides in the second domain could compete with attached tumor-derived epitopes. Therefore, we removed the second domain, retaining the N-terminal domain, which contains a "universal" helper epitope. We investigated the ability to induce CTL responses of candidate peptides placed at the C terminus of this domain. As test peptides, we repositioned the two known CTL motifs from the second domain to this site. Strong CTL responses to each peptide were induced by the engineered construct, as compared with the native FrC construct. Induced CTLs were able to specifically kill tumor cells transfected with FrC as a surrogate tumor Ag both in vitro and in vivo. Further reduction of the domain to a short helper epitope generated only weak CTL responses against fused peptides, and synthetic peptides mixed with the plasmid containing the first domain were ineffective. The single FrC domain-peptide vaccine design also was able to induce high levels of CTLs against a known epitope from carcinoembryonic Ag. Response to peptide was suppressed if two FrC domains were present, consistent with immunodominance. These principles and designs may have relevance for cancer vaccines delivered via DNA.

Original publication

DOI

10.4049/jimmunol.167.3.1558

Type

Journal article

Journal

Journal of immunology (Baltimore, Md. : 1950)

Publication Date

08/2001

Volume

167

Pages

1558 - 1565

Addresses

Tenovus Laboratory, Molecular Immunology Group, Southampton University Hospitals Trust, Southampton SO16 6YD, United Kingdom.

Keywords

T-Lymphocytes, Cytotoxic, Tumor Cells, Cultured, Animals, Mice, Inbred C57BL, Humans, Mice, Thymoma, Peptide Fragments, Carcinoembryonic Antigen, Recombinant Fusion Proteins, Vaccines, DNA, Cancer Vaccines, Adjuvants, Immunologic, H-2 Antigens, Epitopes, T-Lymphocyte, Injections, Intramuscular, Reproducibility of Results, Lymphocyte Activation, Cytotoxicity, Immunologic, Binding, Competitive, Amino Acid Motifs, Protein Structure, Tertiary, Protein Binding, Plasmids