A Tie-2 DNA vaccine targeting tumor endothelium

Proc Amer Assoc Cancer Res, Volume 45, 2004 4844 Tie-2 stabilises pericyte/endothelial interactions during angiogenesis and is over expressed on tumor endothelium. A vaccine that targets endothelium over-expressing Tie-2 may result in vessel damage and stimulate an inflammatory cascade resulting in disease regression. To validate the use of Tie-2 as a target, human Tie-2 was used as a xenogenic vaccine in mice. Preliminary studies suggest that immunisation of balb/c mice by gene gun with DNA from the extracellular region of Tie-2 resulted in cessation of tumor growth. To determine if we could design a syngeneic vaccine that would work in both mice and humans a conserved region of Tie- 2 was cloned. HLA-A*0201 transgenic mice were immunised with this construct to determine if a repertoire of HLA-A*0201 T cells exist that recognise Tie-2. Within the Tie-2 region an HLA-A*0201 epitope was identified that is identical between mice and humans. Anchor modification of this epitope, increased binding to MHC. Immunisation of HLA-A*0201 mice with this enhanced peptide stimulated CTL responses that recognise T2 cells pulsed with either enhanced or wild type peptide. We then generated a human DNA vaccine incorporating the identified region of Tie-2 and used site directed mutagenesis to enhance the CD8 epitope. Using a gene gun HLA-A2 transgenic mice were immunized with the Tie-2 DNA construct. High avidity CTL were obtained from all mice immunized with this construct. Tetramer studies indicated a frequency of up to 1 in 1x103 CD8 cells being specific for this epitope. Moreover these CTL recognise endothelial cells over-expressing Tie-2. This Tie-2 construct is currently being screened for toxicity and efficacy in tumor models. These studies provide a novel approach to cancer vaccination.