Protease inhibitor:protease sensitive expression system, composition and methods for improving the therapeutic activity and specificity of proteins delivered by bacteria

Abstract

Bacteria which co-express protease inhibitors and protease sensitive therapeutic agents, which are surface displayed, secreted and/or released and result in their localized production and maintenance within a target tissue and inactivation outside of the target tissue, thereby increasing therapeutic activity and reducing the systemic toxicity. The bacteria may be attenuated, non-pathogenic, low pathogenic or a probiotic. Protease sensitivity may be further accomplished by engineering protease degradation sites within the therapeutic agents, further enhancing the inactivation outside of the target tissue while retaining activity within the target tissue through co-expression of a protease inhibitor. Novel chimeric proteins secreted by bacteria, including chimeric toxins targeted to neoplastic cells, tumor matrix cells and cells of the immune system, and combination therapies of these protease inhibitor:chimeric toxin-expressing bacteria together with small-molecule and biologic agents are also described. Non-conjugative bacteria limiting exchange of genetic material, and antibody resistant bacteria are also provided.