Expression of immunogenic substances

#The invention relates to methods of altering the sensitivity of a leukocyte to a target antigen.

#Unlike antibody molecules, T cells can migrate actively and efficiently through microvascular walls (a process known as extravasation), allowing them to penetrate the core of a solid tumor before they exert their cytolytic function. Ex vivo expansion and re-infusion of autologous tumor-reactive T cells is being explored as an experimental approach to cancer therapy. However, circulating T cells from peripheral blood lack specificity for tumor antigens (1) and it is often impractical or impossible to obtain sufficient numbers of tumor infiltrating lymphocytes (2). To overcome these problems new approaches have been developed whereby antibody specificity can be combined with the efficient trafficking properties and effector functions of T cells. Several reports have demonstrated the feasibility of transfecting cultured T cells with genes encoding chimeric receptors in which single-chain antibody domains (scFv) are linked to different signalling portions of the TCR/CD3/ζ complex as a means to target T cells towards native antigens (3-6). However it is apparent that the long-term clinical success of this “T-body” approach could depend on the development of solutions to a number of problems.

#Perhaps the most significant concern is that since few “Cancer antigens” are truly tumor-specific (7), successful therapy with tumor-reactive T-bodies could be associated with significant collateral damage to normal tissues expressing low levels of the targeted antigen. It will therefore be desirable to develop strategies by which T cells can be rendered temporarily or permanently anergic to their target antigen, or differentially sensitive to different surface densities of the antigen on target cell membranes.

#FIGS. 1A and 1B are schematic representations of nucleic acid constructs referred to in the example below;

#FIGS. 2A, 2B and 3 show representative FACS data;

#FIG. 4 is a graph showing expression of a chimeric polypeptide (as a percentage of expression in control cells) against time; and

#The invention provides for methods of altering the sensitivity of a leukocyte to a target antigen by regulating the expression of immunogenic polypeptides in eukaryotic cells.

#As used herein, “immunogenic polypeptide” refers to a protein that elicits a response from the immune system that has a therapeutic or anti-tumor effect.

#As used herein, “drug-regulatable promoter” refers to portions of nucleic acid which regulate the expression of coding regions of nucleic acid, in response to the presence of a substance (the “regulatory drug”) exogenous to the cell.