Chua, IC; (2013) CD8 co-receptor modifications to enhance T cell immunotherapy. Doctoral thesis , UCL (University College London).

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Abstract

TCR gene transfer can generate tumour antigen-specific T cells for adoptive immunotherapy. Following TCR gene transfer, transduced T cells usually display the same functional avidity as the parental clone from which the TCR was isolated. However, tumour-antigen specific T cells typically recognize over-expressed self-antigen and are often of low/moderate avidity. It is known that optimal recognition of target cells by CTL requires binding of the cognate peptide MHC class I complex (MHCI) by both TCR and the CD8 co-receptor. Some CD8β chain mutations have been shown to increase CD8 binding affinity with peptide/MHCI and enhance T cell effector function. Murine CD8β chain mutants were generated affecting MHC binding sites (L58R, S53L, S54V and L58R/I25A) or glycosylation sites (T120A, T121A, T124A, and T120A/T121A/T124A). The mutated CD8β molecules were introduced into murine splenocytes using retroviral vectors together with tumour antigen-specific TCRs. The CD8β mutants or control CD8β wild type (WT) chains were first introduced into CD8aa T cells obtained from CD8β knockout mice. All T cells were co-transduced to express the murine F5-TCR which recognizes the model tumour antigen, influenza A nucleoprotein (NP366) presented by H2-Db. The L58R MHC binding CD8 co-receptor mutant (L58R) demonstrated better IFN-γ and IL-2 production in response to relevant peptide while the CD8 glycosylation mutant (T120A/T121A/T124A) mutant demonstrated the opposite effect. The in vitro function of CD4+ T cells transduced with F5-TCR showed that IL-2 and IFN-γ production was enhanced with CD8 co-receptor. In addition, introducing a L58R mutation in the CD8 co-receptor could further increase this effect. The effects of the human CD8 co-receptor with a homologous mutation (I59R) was also investigated in human CD4+ T-cells with a CMV-specific TCR. In vivo studies showed that introducing the F5-TCR alone did not endow CD4+ T cells with significant protection against injected lymphoma cells expressing NP366. However adding CD8 co-receptor to the CD4+ T cells enhanced tumour protection. The genetically modified CD4+ T cells persisted for greater than three months in surviving mice and when re-challenged with antigen the CD4+ T cells with both F5- TCR and CD8 co-receptor had greater proliferative capacity and had more central memory phenotype cells.

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