Prospects and progress of Listeria-based cancer vaccines.

The development of an effective therapeutic vaccine to induce cancer-specific immunity remains problematic. Recently, a species of intracellular pathogen known as Listeria monocytogenes (Lm) has been used to transfer DNA, RNA and proteins into tumour cells as well as elicit an immune response against tumour-specific antigens. Areas covered: Herein, the authors provide the mechanisms of different Listeria monocytogenes strains, which are potential therapeutic cancer vaccine vectors, in addition to their preclinical and clinical development. They also speculate on the future of Lm-based tumour immunotherapies. The article is based on literature published on PubMed and data reported in clinical trials. Expert opinion: Attenuated strains of Listeria monocytogenes have safely been applied as therapeutic bacterial vectors for the delivery of cancer vaccines. These vectors stimulate MHCI and MHCII pathways as well as the proliferation of antigen-specific T lymphocytes. Several preclinical studies have demonstrated the potency of Lm in intracellular gene and protein delivery in vitro and in vivo. They have also indicated safety and efficiacy in clinical trials. Readers should be aware that the ability of attenuated Lm strains to induce potent immune responses depends on the type of deleted or inactivated Lm virulent gene or genes.