Non-Hodgkin's Lymphoma (NHL) is characterized by an indolent clinical course with a median survival of 6- 10 years. The incidence of NHL in the US increases by about 2.5% per year. Clearly, there is a national need for improved therapies for this malignancy. Idiotype-based clinical trials for minimal residual disease of follicular NHL have shown increased disease free survival as well as molecular remission. Currently, the best idiotype-based vaccine, which is in randomized phase III clinical trials, uses KLH as a protein carrier coupled to the B cell receptor (BCR) idiotype (Id) and GM-CSF as an adjuvant. Importantly, those patients who responded to the Id-KLH vaccine with an anti-idiotype response (50-70%) had a better disease free survival. The choice of KLH as the carrier protein to provide T cell help for the anti-Id response is largely historical and there may be better protein carriers that could improve clinical efficacy. One could be the bacterial protein listeriolysin 0 (LLO). We have shown enhanced immunogenicity to tumor associated antigens when they are delivered to the immune system as fusion proteins with a truncated non-hemolytic form of LLO (LLOdetox). Our objective in this project is to explore the utility of LLOdetox to develop more effective anti-lymphoma immunotherapeutics. We will test whether fusing the BCR idiotype to LLOdetox will enhance anti-idiotypic immunity in the treatment of a mouse model of B cell lymphoma, the 38C13 B cell tumor from the C3H/HeN mouse. This model has been used extensively by investigators to test vaccine strategies using the 38C13 idiotype as an immunogen. In preliminary studies we have produced a recombinant single chain fragment of the variable regions (scFV) from the B cell idiotype of 38C13 and devised a FACS technique for monitoring 38C13 tumor growth and residual disease in syngeneic mice. In Specific Aim 1, we will prepare recombinant LLOdetox using an E. coli expression system and chemically conjugate 38Cl3scFv to either rLLOdetox or to KLH. In Specific Aim 2 we will determine whether conjugating 38C13scFv to rLLOdetox provides better anti- tumor efficacy and immunity than the conventional vaccine conjugate 38C13scFv-KLH. At the completion of Phase I, we hope to have demonstrated that 38Cl3scFv-LLOdetox is a superior anti-tumor immunotherapeutic than 38C13scFv-KLH. We will also have tested three possible adjuvants to enhance its delivery. This will set the stage for a Phase II proposal focused on preparations for entering clinical trials.
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