Cancer cells frequently display defects in their antigen-processing pathway and thereby evade CD8 T cell immunity. We described a novel category of cancer antigens, named TEIPP, that emerge on... Show moreCancer cells frequently display defects in their antigen-processing pathway and thereby evade CD8 T cell immunity. We described a novel category of cancer antigens, named TEIPP, that emerge on cancers with functional loss of the peptide pump TAP. TEIPPs are non-mutated neoantigens despite their 'self' origin by virtue of their absence on normal tissues. Here, we describe the development of a synthetic long peptide (SLP) vaccine for the most immunogenic TEIPP antigen identified thus far, derived from the TAP-independent LRPAP1 signal sequence. LRPAP1(21-30)-specific CD8 T cells were present in blood of all tested healthy donors as well as patients with non-small cell lung adenocarcinoma. SLPs with natural flanking, however, failed to be cross-presented by monocyte-derived dendritic cells. Since the C-terminus of LRPAP1(21-30) is an unconventional and weakly binding serine (S), we investigated if replacement of this anchor would result in efficient cross-presentation. Exchange into a valine (V) resulted in higher HLA-A2 binding affinity and enhanced T cell stimulation. Importantly, CD8 T cells isolated using the V-variant were able to bind tetramers with the natural S-variant and respond to TAP-deficient cancer cells. A functional screen with an array of N-terminal and C-terminal extended SLPs pointed at the 24-mer V-SLP, elongated at the N-terminus, as most optimal vaccine candidate. This SLP was efficiently cross-presented and consistently induced a strong polyclonal LRPAP1(21-30)-specific CD8 T cells from the endogenous T cell repertoire. Thus, we designed a TEIPP SLP vaccine from the LRPAP1 signal sequence ready for validation in clinical trials. Show less
From the earliest times of their evolution, multi-cellular organisms have been defending themselves against infectious agents like nucleic acids, viruses, bacteria, fungi and parasites. Continuous... Show moreFrom the earliest times of their evolution, multi-cellular organisms have been defending themselves against infectious agents like nucleic acids, viruses, bacteria, fungi and parasites. Continuous selection pressure resulted in the development of sophisticated immune systems, which in their adaptive forms have exquisite specificity as well as memory for pathogen antigens. On the other hand, infectious agents developed elaborate strategies to escape from, or counteract, host defense mechanisms. Viruses are totally dependent upon host cells for replication and have developed an impressive variety of mechanisms to shield themselves from being detected by the host immune system. The subject of this thesis concerns a particular example of how viruses, specifically some members of genus Varicellovirus, counteract an important step in one of the acquired immunity pathways: the presentation of antigen by Major Histocompatibility Complex (MHC) class I molecules to cytotoxic T-cells. This thesis describes the discovery of a new family of proteins that inhibit the Transporter associated with Antigen Processing (TAP), and sets the first steps towards the explanation of how these inhibitors interfere with antigen transport by the MHC class I loading complex. Show less
