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Non-Hodgkin lymphoma (NHL) is a highly prevalent disease with approximately 30,000 cases diagnosed every year in the United States.

Despite advance in the treatment of NHL the majority of patients relapsed after chemotherapy treatment and frequently die of disease progression or treatment related complications. Therefore there is a need for novel and effective treatment strategies for the treatment of patients with NHL.

NHL cells are capable of evading the immune system and this creates a major challenge to achieve durable complete responses. NHL cells are characterized by deficient mechanisms of antigen presentation that impair effective anti-lymphoma immune recognition.

Because breaking tolerance to NHL cells constitutes a potential target for immunotherapy of this disease we have developed strategies to improve immune recognition of lymphoma cells using gene therapy mediated by adenovirus encoding CD40 ligand (CD154).

We have constructed replication defective adenovirus encoding murine CD154 â\#8364;“ Ad-ISF154 and a chimeric human/mouse CD154, Ad-ISF35, this construct also contains an in-frame deletion of the major MMP-cleavage site, allowing for sustained high-level expression on the plasma membrane.

Using the A20 mouse lymphoma model we generated subcutaneous (S.Q.) NHL tumors that were injected with either Ad-ISF154 or Ad-ISF35.

BALB/c mice were injected S.Q. with 3x105 A20 cells. 14 days later the NHL tumors were injected with: Saline (control Group 1), Ad-ISF154 (Group 2), Ad-ISF35 (Group 3) and Ad-GFP (Group 4 - control adenovirus). On day 28, 87% (7/8) of mice treated with Ad-ISF35 intratumoral injection had complete tumor regression. Also, the majority of mice treated with Ad-ISF154 had tumor regression, 75% (6/8). Conversely, only 12.5% (1/8) of mice treated with Ad-GFP had no evidence of tumor progression while all those treated with control saline had rapid disease progression. Interestingly all the mice that achieved tumor regression after treatment with Ad-ISF154 and Ad-ISF35 were protected against tumor re-challenge.

Analysis of humoral and cellular immune responses in the mice treated with Ad-ISF154 and Ad-ISF35 indicated strong immune reactivity against A20 derived proteins by western blot and T cell reactivity measured by IFN-g ELISPOT assays suggesting anti-lymphoma activity.
 >Together our data suggest that intratumoral injection of A20 NHL lymphoma tumors with Adenovirus encoding CD154 is capable of breaking immune tolerance resulting in tumor regression and systemic T and B cell mediated immune responses against tumor cells.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA