Antibody- and Peptide-based Immunotherapies : Proof-of-concept and safety considerations

The aim of cancer immunotherapy is to eradicate tumours by inducing a tumour-specific immune response. This thesis focuses on how antibodies and peptides can improve antigen presentation and the subsequent tumour-specific T cell response. Tumour recognition by the immune system can be promoted through delivery of antigen in the form of a vaccine. One example is the development of a therapeutic peptide vaccine containing both CD4+ and CD8+ T cell epitopes. So far, peptide vaccinations have shown limited success in clinical trials and further improvements are needed, such as choice of adjuvant and T cell epitopes, as well as targeted delivery of peptides and adjuvants to the same DC. In paper I, we describe the development of a peptide-peptide conjugate (with a tumour T cell epitope) that, via immune complex formation and FcγR binding, enhance antigen uptake and activation of DCs. The conjugate consists of three tetanus toxin-derived linear B cell epitopes (MTTE) that were identified based on specific IgG antibodies in human serum. Three MTTE peptide sequences were conjugated to a synthetic long peptide (SLP) that consists of a T cell epitope derived from the desired target tumour. In paper II, the conjugate was evaluated in a modified Chandler loop model containing human blood, mimicking blood in circulation. The conjugate was internalised by human monocytes in an antibody-dependent manner. A conjugate containing the model CMV-derived T cell epitope pp65NLV generated recall T cell responses dependent on MTTE-specific antibodies and the covalent conjugation of the three MTTE with the SLP. In paper III, a CD40-specific antibody was characterised for local treatment of solid tumours. The antibody eradicated bladder tumours in mice and induced T cell-mediated immunological memory against the tumour. In paper IV, we characterised the Chandler loop model (used in paper II) for its potential use in predicting cytokine release syndrome (CRS) in response to monoclonal antibodies (mAbs). Superagonistic antibodies (e.g., OKT3) induced rapid cytokine release whereas no cytokine release was induced by antibodies (e.g., cetuximab) associated with low incidence of CRS in the clinic. In conclusion, this thesis work demonstrates proof-of-concept of improved strategies for antibody- and peptides-based cancer immunotherapies and their potential use in multiple cancer indications