Steven Lee - Overview

Recent years have seen considerable advances in the area of T cell therapy for human malignancies and EBV-associated tumours occupy a key position as models in this field. Work within my laboratory is exploring the possibility of targeting CD8+ and CD4+ EBV-specific T cell responses to treat two such EBV-positive malignancies, Hodgkin’s Disease (HD) and Nasopharyngeal Carcinoma (NPC). The work focuses on three main areas of research:

1. Identification, selective reactivation and expansion of CD8+ and CD4+ T cells specific for tumour-associated EBV antigens.

Within the malignant cells of HD and NPC, EBV protein expression is restricted to EBNA1, LMP1 and LMP2. Of these, endogenously expressed EBNA1 is protected from processing via the ubiquiting-proteasome pathway and this cannot be targeted by HLA class I-restricted Cytotoxic T Lymphocytes (CTLs). Nevertheless, LMPs 1 and 2 are processed and can elicit CTL responses and much of my research over the last few years has focused on the basic quenstions that need to be resolved if one is to exploit these responses therapeutically. In particular we have defined several CTL target epitopes in LMP2 restricted through HLA alleles that are common in Caucasians and the Chinese population (who are most at risk of NPC). However, our work on healthy virus carriers and HD and NPC patients has also shown that the LMPs are relatively weak immunogens (which may explain the inability of host immune responses to clear virus-infected malignant cells). Therefore, we are now exploring ways of selectively reactivating responses to these tumour-associated proteins both in vitro, using dendritic cells pulsed with synthetic peptide epitopes of infected with recombinant viral vectors, and in vivo (see below). CD4+ T cells are important in maintaining an effective CTL response and may mediate anti-tumour effects directly. Therefore, we re also investingating CD4+ T cell responses to EBNA1, LMP1 and LMP2. To reactivate such responses in vitro, we are exploring the use of viral vectors encoding EBV proteins engineered to include a lysosome targeting sequence (thereby directing them into the HLA class II processing pathway).

2. T cell targeting to, and recognition of, HD and NPC tumours.

A prerequisite for an effective T cell-based therapy is that T cells must first traffic to the rumour site and then recognise the tumour. Interestingly, both HD and NPC are characterised by a large cellular infiltrate that includes T lymphcytes. Using immunohistochemistry, combined with studies of chemotaxis and tissue binding, we are attempting to determine the molecular basis for this T cell infiltration. We are also using cytotoxicity and cytokine release assays to determine the ability of EBV-specific T cell clonse to recognise antigen presented by HD and NPC tumour cells.

3. Phase I clinical studies in HD and NPC using adoptive T cell transfer and immunisation to boost EBV-specific T cell responses.

We have begun a phase I of adoptive T cell therapy to treat advanced EBV-positive malignancies. Patients will be infused with large numbers of autologous EBV-specific CD8+ and CD4+ T cell clonse generated in vitro using peptide-loaded dendritic cells. In collaboration with Prof. Alan Rickinson’s laboratory, we are also developing a recombinant viral vaccine to boost LMP2 and EBNA1 responses.