Clinical, Immunologic, and Molecular Evaluation of Poxvirus Vaccines Expressing Co-stimulatory Molecules

Howard L. Kaufman, M.D.

Columbia University

Funded in September, 2003: $300000 for 3 years


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Determining How "Therapeutic" Vaccines Fight Malignant Tumors

The Columbia researchers will investigate how two experimental vaccine therapies induce both local and broad immune responses in patients who have intractable malignant tumors, within a clinical trial that is funded by other sources.

Recent evidence suggests that cancers suppress the body's immune responses at the site of tumor growth. This explains why tumors grow and metastasize undetected by the body's immune system. Substantial research now is focused on developing therapeutic vaccines that could induce the patients' immune systems to identify and attack the tumors. Most of these experimental vaccines contain specific antigens (pathogens) that are delivered to the tumor site, where they get inside the tumor cells. Then immune T cells learn to recognize this antigen and attack it, killing its host, the tumor cell. Another approach, however, is based on evidence that immune T cells may lay dormant in the presence of a tumor because the tumor does not transmit "co-stimulatory" signals that are needed to activate T cells. The Columbia researchers hypothesize that delivering a "co-stimulatory" molecule, rather than an antigen, into the tumor cells might provide a general, more effective way to galvanize T cells to attack the tumor cells.

The investigators have developed two experimental therapeutic vaccines to deliver co-stimulatory molecules to tumor cells and are testing the vaccines' safety in clinical studies supported by the National Cancer Institute (NCI). Both vaccines consist of fowlpox virus, which is not harmful to humans but can insert itself into tumor cells and deliver the co-stimulatory molecule into the tumor cells. (One vaccine contains a single co-stimulatory molecule, the other contains three.) Once inside the tumor cells, the co-stimulatory molecule(s) transmit their signals to patients' immune T cells, which then attack the tumor cells. The NCI-supported study is determining the two vaccines' safety in 36 patients with intractable tumors that have not responded to any available therapy. The patients are randomized to receive one vaccine or the other.

With Dana support, the researchers will measure participating patients' T cell levels before and after vaccine administration, to determine the extent to which the vaccines stimulate T cell function at the tumor site and whether this leads to generalized (systemic) anti-tumor immunity throughout the patients' bodies. The researchers also will try to identify predictors of patients' immunologic response. The clinical trial to which this study will be attached has been approved by Columbia's Institutional Review Board, the National Institutes of Health, and by the Food and Drug Administration which authorizes human testing of experimental drugs and biologicals.


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Clinical, Immunologic, and Molecular Evaluation of Poxvirus Vaccines Expressing Co-stimulatory Molecules

There is currently a great deal of excitement about the use of tumor vaccines for the treatment or prevention of cancer. Murine models have suggested the importance of T-cells in tumor rejection, although the mechanism of tumor regression in human patients following vaccination has not been fully elucidated. Nonetheless, the development of tumor vaccines has focused on the priming and expansion of tumor-specific T-cells. Since T-cell activation depends on both T-cell receptor (TCR)/ peptide-MHC interaction and signals received through the binding of co-stimulatory molecules, we developed poxvirus vectors expressing CD80 (B7.1) and human carcinoembryonic antigen (CEA) for vaccination of patients with advanced cancers.

Although we observed CEA-specific T-cells in peripheral blood following vaccination, we are now interested in evaluating the effector functions and impact of the local tumor microenvironment on T-cell responses. Furthermore, the lack of co-stimulatory molecule expression by established tumors has been suggested as a major mechanism of T-cell ignorance. Thus, we hypothesize that the local delivery of co-stimulatory molecules by poxvirus vectors to established tumors will enhance effector T-cell function at the tumor site and lead to systemic anti-tumor immunity.


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Howard L. Kaufman, M.D.

Howard L. Kaufman, M.D., is a recognized leader in the application of recombinant poxviruses as tumor vaccines, with more than 15 years experience in basic and clinical vaccine research. He is the Director of the Tumor Immunology Program at Columbia University and directly supervises the basic immunology laboratory and clinical trials research He also serves as Vice Chairman of Surgical Oncology at Columbia University and is the Director of the Interleukin-2 Unit co-director of the newly established, inter-disciplinary Melanoma Center at The New York Presbyterian Hospital. Dr. Kaufman also serves as the Associate Director for Clinical Research of the Herbert Irving Comprehensive Cancer Center. He holds appointments in the Departments of Surgery and Pathology at the College of Physicians and Surgeons of Columbia University and regularly trains Ph.D. students in his lab. Dr. Kaufman was named the first Doris Duke Clinical Scientist Scholar for cancer in 1998 and has conducted over thirty clinical trials of vaccines and biologic agents in cancer. He is the chair of the Immunomolecular Therapeutics Committee of the Southwest Oncology Group (SWOG) and is a member of the Clinical Oncology study section of the NCI as an expert in human tumor immunology. He is a member of numerous scientific societies and advisory boards. He serves on the editorial board of Cancer Investigation and the Journal of Translational Medicine, and serves as a reviewer for many other scientific journals. Heidi Hoerig, Ph.D., born in Freiburg, Germany, was educated at the University of Giessen, and the University of Basel and Vienna, where she received her Ph.D. in Natural Sciences in 1993. Pursuing her interest in T cell immunology, she continued her postdoctoral training at the Albert Einstein College of Medicine, New York, where she studied antigen binding to MHC class I molecules, and received a fellowship from the Cancer Research Institute. She then joined the immunology laboratory of Dr. Howard Kaufman at AECOM, and introduced immune monitoring assays for cancer vaccine trials. She also contributed a model for intestinal cancer, using transgenic Apc1638N/CEA mice expressing a relevant human tumor antigen to study recombinant vaccinia virus/CEA vaccines. She recently joined Columbia University, as Assistant Professor of Surgical Science, and is collaborating with Dr. Kaufman, as part of the Tumor Vaccine Program in Surgical Oncology. She established an Immune Monitoring Program for the evaluation of vaccine efficacy in cancer patients. Dr. Hoerig is dedicated to studying the host/tumor interactions within the tumor microenvironment, and on how immunotherapy might tip the balance in order to induce and sustain an anti-tumor immune response. Basic and translational research programs are initiated to investigate on the critical events leading to tumor regression by modern technologies, such as gene array, in collaboration with the NIH. Dr. Hoerig is member of several scientific societies, such as AACR, AAI and SBT.


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Lay Results:
The development of vaccines for cancer holds immense promise, but has been hindered by a lack of clinical benefit to date. One reason for this is that growing tumors produce factors that block the immune system from attacking the cancer. To improve the effectiveness of vaccines we developed a poxvirus vaccine encoding one or three genes designed to stimulate T cells—immune cells that can fight cancers—within a growing cancer. This was accomplished in a clinical trial of patients with advanced cancer and we found that two patients did experience a decrease in the growth of their tumors. This was associated with the appearance of cancer fighting T cells in the blood and increased amounts of cytokines in the cancer, which are thought to help fight cancer as well. Our studies also resulted in the discovery of a new molecular pathway— ILT3—that may block the immune system from working. This pathway was evaluated in a mouse model and shown to be involved in the growth of cancers that would otherwise be destroyed by the immune system. This information is being used to develop new treatments designed to block ILT3 while using poxvirus vaccines in patients with advanced cancers.

Scientific Results:
A major obstacle to successful immunotherapy is the presence of inhibitory factors within the local tumor microenvironment. We have previously shown that direct injection of live vaccinia viruses expressing T cell costimulatory molecules, B7.1, ICAM-1 and LFA-3 induces regression in 50% of injected lesions and regression of metastatic disease in selected patients. Thus, we sought to evaluate the effects of a non-replicating fowlpox virus vector expressing B7.1 alone (rF-B7.1) or B7.1, ICAM-1 and LFA-3 (rF-TRICOM). A Phase I clinical trial was conducted in patients with metastatic tumors accessible for local injection. Overall 12 patients were treated and no serious adverse events were noted. Only two patients had objective responses in injected lesions and no patients had evidence of regression in distant lesions. All patients developed fowlpox-specific antibody responses after two vaccinations. We identified a novel HLA-A*0201-restricted fowlpox virus epitope within a viral DNA polymerase and all HLA-A2 patients developed T cell responses to this epitope as measured in an interferon-g ELISPOT assay. We performed a microarray analysis on tumor samples taken from fine needle aspirates before and after vaccination. We found that numerous interferon-g-related genes were up-regulated at the tumor site and over 900 genes were down-regulated, including ILT3. Further studies suggested that ILT3 could block rejection of human xenograft tumors in a humanized SCID mouse model. We further found that inhibition of T cell proliferation by patient sera could be reversed by pre-treatment with an ILT3 blocking monoclonal antibody. The ILT3 appears to arise from tumor-associated macrophages. Our results suggest that local vaccination with a live replicating poxvirus, such as vaccinia virus, is superior to non-replicating vectors. Simultaneous vaccination and inhibition of ILT3 is a new treatment strategy that merits further investigation.