Tumor gene therapy by MVA-mediated expression of T-cell–stimulating antibodies

Abstract

Immune responses to tumor -associated antigens are often dampened by a tumor -induced state of immune anergy. Previous work has attempted to overcome tumor -induced T -cell anergy by the direct injection of vectors carrying the genes encoding one of a variety of cytokines. We hypothesised that the polyclonal stimulation of T cells, preferably through the TCR complex, would result in a cascade of cytokines associated with T -cell activation and would be best able to overcome T -cell anergy. Here we use the highly attenuated MVA poxvirus to express on tumor cells, in vitro and in vivo, either of three membrane -bound monoclonal antibodies specific for murine TCR complex. Using this system, we have expressed antibodies specific for the CD3" chain ( KT3 ), TCR / complex ( H57 -597 ), and V7 chain ( TR310 ). Tumor cells bristling with these antibodies are capable of inducing murine T -cell proliferation and cytokine production. When injected into growing tumors ( P815, RenCa, and B16F10 ), these constructs induce the activation of immune effector cells and result in the rejection of the tumor. Histological and FACS analysis of tumor -infiltrating leukocytes reveal that the injection of recombinant virus -expressing antibodies specific for the TCR complex attracts and activates ( CD25 + , CD69 + )CD4 and CD8 lymphocytes. This approach represents a novel strategy to overcome T -cell anergy in tumors and allow the stimulation of tumor -specific T cells.

Stable expression of chimeric anti-CD3 receptors on mammalian cells for stimulation of antitumor immunity

“…We and others have previously shown that cells modified to express chimeric anti-CD3 receptors can activate naive T cells. [15][16][17] Expression of anti-CD3 surface receptors should reduce the dependency of T-cell activation on MHC expression, allowing effective therapy by CD80 or CD86 in poorly immunogenic tumors that are normally refractive to modification with costimulatory molecules.…”

Gene Therapy Applications to Cancer Treatment

“…Currently, the most promising approaches are based on replication-competent agents that allow efficient tumour penetration. Exciting results are anticipated with poxviruses [10, 11] and with selectively replicating/targeted adenoviruses [12, 13, 14, 15, 16], although pre-clinical models suggest that significant response rates will only be achieved by combination with standard therapies.…”

“…Vaccinia virus infects all cells, however the host immune response to the vector does not abrogate the tumour immune response even following repeated injections. The availability of attenuated virus ( tk - modified vaccinia ankara ) [10] allows the use of vaccinia in immuno-delicate cancer patients and there is evidence that this vector enhances immunological rejection of the tumour.…”

Cancer gene therapy: an awkward adolescence

“…Expression levels are relatively low and transient, but for some purposes such as targeted introduction of toxin genes or siRNA, this may prove to be a useful vector system because of its ease of use, lack of antigenicity, and apparent safety (no integration, no inflammation). 44 A number of other viruses have been used over the past several years for gene therapy, including Newcastle Disease Virus (see above), vaccinia virus for tumor antigen expression, 45 and other orthopoxviruses, such as canarypox. 46 For nonviral delivery systems, most progress has been made using variations of lipofection.…”