Optimisation of T cell receptor antigen recognition for targeting disease

This thesis is a collection of some of the studies I have undertaken over the last 3.5 years while working as a Research Assistant in the T cell modulation group at the Cardiff University School of Medicine. The work contained within is linked by the common theme of optimising interactions between peptide-Major Histocompatibility (pMHC) molecules, the T cell receptor (TCR), and/or coreceptor that engages these ligands. The work of the T cell modulation group is heavily focused on translational medicine. This aspect of biomedicine is also strongly encouraged by my funding body, the Wellcome Trust. My focus on translational aspects of interactions with pMHC ligands took my work in several different directions. Initially, I examined ways of improving interactions with pMHC that could be used to ameliorate the detection of antigen-specific T cells by flow cytometry. My studies have improved this technology to a point where I can now reliably claim to be able to stain the majority of relevant T cells with their cognate multimeric antigen. The approaches I helped pioneer are now in use all over the world. This work is reported in Chapters 3 and 5, and has resulted in two published primary data papers. A third paper that examines pMHC multimer valency (described in Chapter 4) is in preparation. In addition to the above-mentioned work aimed at improving T cell-related diagnostics using pMHC multimers, I also explored potential ways of improving TCR/pMHC interactions for therapeutic approaches. Specifically, I was interested in exploring whether TCRs displaying enhanced affinities for antigen would be useful in the clinic. These studies necessitated that we establish optimal TCR gene transfer protocols in Cardiff. I took the lead on these optimisation studies (Chapter 6). With the TCR gene transfer technology optimised, I was able to investigate whether increasing functional avidity of TCR-redirected T cells could be achieved by removing defined N-glycosylation sites within the TCR constant domain. This work was based on my observation that the desialylation of T cells improved the surface engagement of pMHC multimers and the recognition of cognate antigen when displayed naturally on a target cell surface. These studies were taken forward in Chapter 7. As part of my work with affinity enhanced TCRs, I was fortunate to test a novel set of TCR-based soluble therapeutic reagents comprising affinity-enhanced TCRs (Chapter 8). The enhanced TCRs were generated by phage display and directed evolution using techniques that were pioneered by my T cell modulation group colleague Jonathan Boulter while working at Avidex Ltd

The TLR9 ligand CpG ODN 2006 is a poor adjuvant for the induction of de novo CD8+ T-cell responses in vitro

Toll-like receptor 9 (TLR9) agonists have gained traction in recent years as potential adjuvants for the induction of adaptive immune responses. It has nonetheless remained unclear to what extent such ligands can facilitate the priming events that generate antigen-specific effector and/or memory CD8+ T-cell populations. We used an established in vitro model to prime naive precursors from human peripheral blood mononuclear cells in the presence of various adjuvants, including CpG ODN 2006, a synthetic oligonucleotide TLR9 ligand (TLR9L). Unexpectedly, we found that TLR9L induced a suboptimal inflammatory milieu and promoted the antigen-driven expansion and functional maturation of naive CD8+ T cells ineffectively compared with either ssRNA40 or 2′3′-cGAMP, which activate other pattern recognition receptors (PRRs). TLR9L also inhibited the priming efficacy of 2′3′-cGAMP. Collectively, these results suggest that TLR9L is unlikely to be a good candidate for the optimal induction of de novo CD8+ T-cell responses, in contrast to adjuvants that operate via discrete PRRs

Reduced naïve CD8+T-cell priming efficacy in elderly adults

International audienceAging is associated with impaired vaccine efficacy and increased susceptibility to infectious and malignant diseases. CD8 + T-cells are key players in the immune response against pathogens and tumors. In aged mice, the dwindling na€ ıve CD8 + T-cell compartment is thought to compromise the induction of de novo immune responses, but no experimental evidence is yet available in humans. Here, we used an original in vitro assay based on an accelerated dendritic cell coculture system in unfractioned peripheral blood mononuclear cells to examine CD8 + T-cell priming efficacy in human volunteers. Using this approach, we report that old individuals consistently mount quantitatively and qualitatively impaired de novo CD8 + T-cell responses specific for a model antigen. Reduced CD8 + T-cell priming capacity in vitro was further associated with poor primary immune responsiveness in vivo. This immune deficit likely arises as a consequence of intrinsic cellular defects and a reduction in the size of the na€ ıve CD8 + T-cell pool. Collectively, these findings provide new insights into the cellular immune insufficiencies that accompany human aging

Divergent roles for antigenic drive in the aetiology of primary versus dasatinib-associated CD8(+) TCR-Vβ(+) expansions

CD8(+) T-cell expansions are the primary manifestation of T-cell large granular lymphocytic leukemia (T-LGLL), which is frequently accompanied by neutropenia and rheumatoid arthritis, and also occur as a secondary phenomenon in leukemia patients treated with dasatinib, notably in association with various drug-induced side-effects. However, the mechanisms that underlie the genesis and maintenance of expanded CD8(+) T-cell receptor (TCR)-V beta(+) populations in these patient groups have yet to be fully defined. In this study, we performed a comprehensive phenotypic and clonotypic assessment of expanded (TCR-V beta(+)) and residual (TCR-V beta(-)) CD8(+) T-cell populations in T-LGLL and dasatinib-treated chronic myelogenous leukemia (CML) patients. The dominant CD8(+) TCR-V beta(+) expansions in T-LGLL patients were largely monoclonal and highly differentiated, whereas the dominant CD8(+) TCR-V beta(+) expansions in dasatinib-treated CML patients were oligoclonal or polyclonal, and displayed a broad range of memory phenotypes. These contrasting features suggest divergent roles for antigenic drive in the immunopathogenesis of primary versus dasatinib-associated CD8(+) TCR-V beta(+) expansions.Peer reviewe

Priming of Qualitatively Superior Human Effector CD8+ T Cells Using TLR8 Ligand Combined with FLT3 Ligand

International audienceThe quality of Ag-specific CD8+ T cell responses is central to immune efficacy in infectious and malignant settings. Inducing effector CD8+ T cells with potent functional properties is therefore a priority in the field of immunotherapy. However, the optimal assessment of new treatment strategies in humans is limited by currently available testing platforms. In this study, we introduce an original model of in vitro CD8+ T cell priming, based on an accelerated dendritic cell coculture system, which uses unfractionated human PBMCs as the starting material. This approach enables the rapid evaluation of adjuvant effects on the functional properties of human CD8+ T cells primed from Ag-specific naive precursors. We demonstrate that a selective TLR8 agonist, in combination with FLT3L, primes high-quality CD8+ T cell responses. TLR8L/FLT3L-primed CD8+ T cells displayed enhanced cytotoxic activity, polyfunctionality, and Ag sensitivity. The acquisition of this superior functional profile was associated with increased T-bet expression induced via an IL-12–dependent mechanism. Collectively, these data validate an expedited route to vaccine delivery or optimal T cell expansion for adoptive cell transfer

The link between CD8⁺ T-cell antigen-sensitivity and HIV-suppressive capacity depends on HLA restriction, target epitope and viral isolate

International audienceBACKGROUND: Although it is established that CD8 T-cell immunity is critical for the control of HIV replication in vivo, the key factors that determine antiviral efficacy are yet to be fully elucidated. Antigen-sensitivity and T-cell receptor (TCR) avidity have been identified as potential determinants of CD8⁺ T-cell efficacy. However, there is no general consensus in this regard because the relationship between these parameters and the control of HIV infection has been established primarily in the context of immunodominant CD8⁺ T-cell responses against the Gag₂₆₃₋₂₇₂ KK10 epitope restricted by human leukocyte antigen (HLA)-B27. METHODS: To investigate the relationship between antigen-sensitivity, TCR avidity and HIV-suppressive capacity in vitro across epitope specificities and HLA class I restriction elements, we used a variety of techniques to study CD8⁺ T-cell clones specific for Nef₇₃₋₈₂ QK10 and Gag₂₀₋₂₉ RY10, both restricted by HLA-A3, alongside CD8⁺ T-cell clones specific for Gag₂₆₃₋₂₇₂ KK10. RESULTS: For each targeted epitope, the linked parameters of antigen-sensitivity and TCR avidity correlated directly with antiviral efficacy. However, marked differences in HIV-suppressive capacity were observed between epitope specificities, HLA class I restriction elements and viral isolates. CONCLUSIONS: Collectively, these data emphasize the central role of the TCR as a determinant of CD8⁺ T-cell efficacy and demonstrate that the complexities of antigen recognition across epitope and HLA class I boundaries can confound simple relationships between TCR engagement and HIV suppression