High-risk Human Papilloma Virus (HPV) induced malignancies are an interesting target for immunotherapy as they invariably express the viral proteins E6 and E7 that allow specific recognition of... Show moreHigh-risk Human Papilloma Virus (HPV) induced malignancies are an interesting target for immunotherapy as they invariably express the viral proteins E6 and E7 that allow specific recognition of tumor cells without the risk of inducing autoimmunity. This thesis describes the preclinical development of pDNA vaccine candidates for the treatment of HPV16 induced malignancies. For this purpose gene-shuffled (SH) versions of HPV16 E6 and E7 were used to avoid the risk of transformation at the vaccination site. To improve the immunogenicity of E6SH and E7SH several optimizations strategies were evaluated. First it is shown that genetic fusion with Tetanus Toxin Fragment C (TTFC), results in a dramatic increase in immunogenicity. The resulting vaccine candidates TTFC-E6SH and TTFC-E7SH were also demonstrated to have lost their transforming potential. Secondly it is demonstrated that the mere addition of an endoplasmatic reticulum targeting sequence and a set of promiscuous CD4 helper epitopes results in an enormous increase of the immunogenicity of E6SH and E7SH. This design decreases the risk of raising competing carrier specific immune responses. Finally several nanoparticle based formulations of a model pDNA vaccine were evaluated and it is demonstrated that for in vivo applications it is essential to shield the cationic charge of such nanoparticles. Show less
In this thesis, several aspects and cellular players involved in the immune response to (HPV-induced) tumors were investigated. In chapter 2 a detailed analysis of HPV-specific immunity in a large... Show moreIn this thesis, several aspects and cellular players involved in the immune response to (HPV-induced) tumors were investigated. In chapter 2 a detailed analysis of HPV-specific immunity in a large group of patients with HPV-induced cervical cancer (CxCa) in relation to HLA-types and prognostic factors was performed. In 30% of the tested patients, circulating HPV specific T cells were found, most often in patients with deeply infiltrating tumors. In this group, patients with HPV specific proliferative immunity displayed better disease free survival. It was shown earlier by Piersma et al [69] that only in 30% of TIL populations, HPV specific T cells were found. In chapter 3 an in depth analysis of the breadth and type of HPV specific T-cell populations in tumor infiltrating T cell (TIL) cultures or LN cells from HPV 16 or 18 positive CxCa patients was performed. We found that if patients displayed a HPV-specific T cell response, this was surprisingly broad. Despite recognition, a number of cells did not produce type 1 cytokines and therefore we tested what TLR-agonist was able to support cytokine induction by these T cells. In chapter 4 we asked the question whether HPV-specific T cells play a role in HPV-induced HNSCC. We hypothesize that HPV-induced tumors are more immunogenic and stimulate strong T-cell reactivity to the viral oncoproteins in contrast to HPV-negative tumors. We set up a pilot study to investigate whether HPV is present in HNSCC in the Dutch patient population and at which anatomical site. Accordingly, blood and tumor infiltrating T cells were analyzed for the presence of functional HPV specific T cells. The lack of T cell responses in CxCa patients and the __poised__ function of tumor-antigen specific T cells could be a lack of proper priming by DC. Therefore we investigated in chapter 5A the effects of CxCa produced soluble factors on the differentiation of antigen presenting cells (APC). Several tumor cell lines hampered DC differentiation or even skewed monocyte differentiation into tolerogenic tumor promoting M2 macrophages. We identified the factors responsible for this and investigated the outcome of the interaction of HPV specific T-cell clones with these macrophages. Since patients with advanced or recurrent disease are treated with platinum based chemotherapy we investigated the immune-modulating effect of this therapy on tumor cells, tumor-modulated APC and subsequent interaction with T cells. This ongoing work is summarized in chapter 5B. Therapeutic vaccination is being developed for treatment of chronic infections and cancer, and aims to generate protective T-cell immunity. Although some clinical successes have been reported, particularly in the field of cancer vaccination, there is still much to be gained in terms of efficacy [91,92]. Especially the adjuvant used and the route of administration of vaccines are critical factors that determine the type and memory of the resulting T-cell response. Intradermal vaccination is an attractive method for diseases in the skin such as HPV induced tumors and melanomas since the induced T cells get skin-homing instructions. In chapter 5 we showed already that highly pure DC can become activated by the addition of several different TLR agonists in vitro. To assess the effect of these TLR agonists on the APC present in the dermis, a human skin-explant model was used to analyze the phenotype and function of the APC migrating out the skin upon TLR-injection. These results are described in chapter 6. Surprisingly, only few TLR-agonists turned out to induce activation of the migrating cells. The current treatment of patients with advanced colorectal cancer consists of chemotherapy together with the MAb bevacizumab that blocks soluble VEGF. The addition of a second antibody that targets tumor expressed EGFR (cetuximab) to this treatment did not result in the expected disease free survival benefit in a large randomized phase III study (CAIROII). Analysis of gene polymorphisms in the Fc__Receptors revealed that patients with the high affinity FCGR3A polymorphism did significantly worse upon addition of cetuximab to the standard treatment. As colon cancers are generally infiltrated with macrophages we tested the hypothesis that membrane bound antibodies could activate tumor promoting M2 macrophages and that this would happen more efficiently in patients with high affinity FCGRIIIA in chapter 7. In chapter 8 the work of this thesis is discussed in light of recent literature. Show less
