Identification of Tumour Associated Antigens as Potential Targets for the Immunotherapy of B-cell Chronic Lymphocytic Leukaemia (B-CLL)

B-CLL, the most common adult B-cell malignancy in USA and the western world, is characterized by the accumulation of CD5+ mature B-cells in blood, bone marrow and lymphoid tissues. Many cases require no treatment because of an indolent course, while other patients become symptomatic or develop signs of rapid progression. Treatment is usually non-curative and is directed at reducing the symptoms. However, new therapies are currently under investigation aiming to achieve a curative therapy for B-CLL. The increasing understanding of how peptide antigens are processed, transported and presented by HLA, the identification of tumour antigens recognised by cytotoxic T lymphocytes and the identification of T-cell epitopes on human tumor cells, have opened the routes for the development of more efficient strategies for tumour immunotherapy. Several antigens have been characterized as tumour associated antigens (TAA) in B-CLL, with the potential to elicit specific anti-tumour responses. This thesis addresses the role of survivin, a member of the family of inhibitor of apoptosis proteins, as a potential target for the immunotherapy of B-CLL. Data on survivin expression showed no/ little expression of survivin in resting B-CLL, which was upregulated by in vitro activation with CD40 ligation, CpG-oligodeoxynucleotides (ODN), and with both stimulators together. CD40 ligation resulted in greater B-CLL cell activation, survivin expression, upregulation of activation markers (CD54, CD80 and CD86), and in enhanced activity of B-CLL cells to stimulate allogeneic T cell proliferation, compared to the other two ways of stimulation. Studying the induction of autologous tumour specific T cell responses in vitro, CD40L activated B-CLL cells enhanced CTL responses compared to unactivated cells. No significant difference in response of B-CLL patients T cells to survivin peptide pulsed T2 cells was found between HLA-A2+ and HLA-A2- patients, and no clear peptide specific responses were seen in either group. After investigating survivin peptides for their potential to induce cytotoxic T cell responses, generating survivin specific CTL line from a healthy donor was attempted using peptide pulsed autologous monocyte derived dendritic cells, but was unsuccessful suggesting that no T cells in the culture were able to recognise survivin peptides, or that the culture conditions used were inappropriate for the generation and maintenance of such responses. Finally, in investigation of other TAA expression in B-CLL cells, no expression of MAGE-A1, MAGE-A3, Proteinase-3, WT-1 was detected pre- and post CD40 activation. Positive PRAME expression was detected in 8 out of 20 CD40L activated CLL cells whilst NY-ESO-1 showed an upregulation in one sample. Overall results indicate that much work is still needed to study the potential of immunotherapy in the treatment of B-CLL.