In the cancer immunology and immunotherapy arena, we have solved a major paradox in the role of NKT cells in tumor immunosurveillance, as NKT cells have been reported by others to protect, and by us to suppress tumor immunosurveillance. We found that type I NKT cells (carrying the invariant V?14J?18 T cell receptor) contribute to tumor immunity, whereas the type II NKT cells (with non-invariant receptor) are sufficient to suppress tumor immunosurveillance. We also showed that the type II NKT cell is the main cell suppressing immunosurveillance in 4 tumor models in which the classic CD4+CD25+ T regulatory cell does not play a role. We also found that blockade of the downstream mediator of this pathway, TGF-beta, can synergize with an anti-cancer vaccine in mice, increasing the T cell response and more completely inhibiting growth of an established tumor (cervical cancer model) than the vaccine alone. The protection is CD8 T cell-dependent. We have just opened a phase I clinical trial of a human anti-TGF-beta monoclonal antibody in melanoma and renal cell cancer patients in the NIH Clinical Center as part of a CRADA with Genzyme Corporation. If successful, the intent is to use this agent in conjunction with a cancer vaccine. We also found that a recombinant adenovirus expressing Her-2 can prevent appearance of spontaneous autochthonous breast cancers in BALB-neuT Her-2 transgenic mice. The mechanism is antibody mediated and requires CD4 T cells only for help, and does not require CD8 cells. However, the protection is not FcR dependent, unlike that of Herceptin, so the antibody induced by the vaccine appears to block signal transduction by the oncoprotein, rather than induce killing by ADCC. This cancer vaccine may be more effective for breast cancer than the monoclonal Herceptin, because the patient would make her own antibodies and these would not be dependent on FcR-mediated mechanisms. We are working with a collaborator to develop an adenovirus expressing human Her-2 in preparation for a clinical trial in human breast cancer, and have had pre-pre-IND discussions with the FDA. We have mapped a new epitope presented by HLA-B7 from the PAX-FKHR fusion protein unique to and expressed by 85% of alveolar rhabdomyosarcoma patients. In addition, we have mapped HLA-A2-restricted epitopes from 4 new cancer antigens studied in collaboration with Ira Pastan's lab, all expressed in prostate cancer but several also expressed in breast cancer and some other tumors. We have modified their sequences by epitope enhancement to make them more immunogenic, and have shown killing of human tumor cells by T cells specific for the first two of these. The first of these to be developed, TARP, is the subject of our planned clinical trial in prostate cancer patients that has been approved by the PRMC but has been delayed in obtaining an IND because of personnel turnover in the NIH Clinical Center Department of Transfusion Medicine that will prepare the dendritic cells for immunization, and because of changes at CTEP in decisions about IND filing. We hope that this trial will be opened within a few months.In the HIV and viral vaccine arena, first in studies also applicable to cancer vaccines, we have found that IL-15 expression by a vaccine will lead to induction of higher avidity cytotoxic T lymphocytes (CTL) that more effectively clear virus infections (or kill tumor cells). We also found that IL-15 will overcome the lack of CD4 T cell help in CD4 deficient animals, allowing induction of long-lived memory CTL that otherwise would not be induced without CD4 help. This may be a critical finding for therapeutic vaccines for HIV, for which it will be necessary to immunize HIV-infected or cancer patients with a deficiency of CD4 T cell help. We have also carried out epitope enhancement of HIV helper and CTL epitopes presented by human class II and class I HLA molecules, to make improved HIV vaccine constructs.
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