Anti-lymphoma immunity: relative efficacy of peptide and recombinant DNA vaccine

The efficacy of vaccines consisting of (1) Ig idiopeptides of a murine B-lymphoblastoma, 2C3, and (2) a corresponding scFV-expressing DNA construct was determined on the basis of their ability to induce anti-tumor immune response and protection against tumor growth. Peptide-KLH complexes and a plasmid expressing single-chain variable fragment (scFv) corresponding to 2C3 Ig VH and VL chains were used separately as vaccines. Immunized BALB/c mice were bled and then challenged with live 2C3 tumor. Survival of various challenged groups was also determined. The results indicate that CDR3-H (VH3) peptides, and the plasmid DNA when given with GM-CSF, only moderately retarded tumor growth, whereas killed 2C3 tumor vaccine induced lasting protection, as shown earlier. Both peptides and scFv-plasmid induced circulating anti-Id antibodies, but no specific cytotoxic T-cell (CTL) activity was detected. However, in spite of their inability to induce CTL activity, both idiopeptides and the scFv-expressing plasmid DNA displayed epitopes recognized by an Id-specific long-term splenic CTL line (A102) obtained from mice vaccinated with killed 2C3 tumor.