A vaccine to break tolerance to cervical carcinoma oncoprotein

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Evidence that cervical cancer is caused by Human Papillomavirus is compelling. Once the virus enters the cells of the cervix, it produces a protein named E7 which functions to make the cells cancerous. Cervical cancer is the fifth commonest cause of death in women in Australia, and the major killer of women world-wide. The E7 protein is the ideal target for a vaccine since it occurs only in the tumour cells. Cervical tumour cells are killed by specialised immune system cells termed CTLs which recognised fragments of the E7 molecule on their surface, bound to 'self' MHC molecules. Our laboratory has developed several mouse models of human cervical cancer, and has worked out which parts of the E7 protein are important in developing an appropriate immune response to control tumour growth. However a major finding is that the E7 molecules render the CTL cell population incapable of making an appropriate response to kill the tumour cells. We believe that this process, termed 'tolerance induction' can be overcome by using a novel approach as follows. Specialised antigen presenting cells , termed 'dendritic cells' (DCs) will be isolated and made to produce E7 protein by infecting them with a geneticlly modified virus (Adenovirus) which expresses E7 and specialised DC activators molecules, but is incapable of itself replicating. The dendritic cells will be re-introduced into the host as a vaccine, and will present the E7 to the immune system in such a way that tolerance will be broken. In other words the vaccine recipient will again be able to make a CTL immune response to the E7 protein in their tumours, and so be able to kill the tumour cells.