Improvement of the efficacy of the attenuated bacterium Listeria monocytogenes as anticancer vaccine through cell wall functionalization using bio-orthogonal click chemistry

The attenuated Listeria monocytogenes (Lmat) has been identified as a promising candidate for the development of anticancer vaccines and drug delivery systems. Its ability to selectively target tumors, elicit immune responses, and spread between infected cells makes it an ideal candidate for such applications. The first part of this study focuses on optimizing a two-step labelling process, which involves the metabolic incorporation of a chemical handle followed by copper-catalysed azido-alkyne cycloaddition (CuAAC) to conjugate small molecules, such as the chemotherapeutic drug doxorubicin. The in vitro and in vivo testing of doxorubicin-loaded Lmat (dox-Lmat) demonstrated enhanced cytotoxicity compared to the control. Given these encouraging results, we proceeded to test the feasibility of associating Lmat with existing therapeutic agents for melanoma, including BRAF inhibitors (BRAFi), MEK inhibitors (MEKi), and pigmentation inhibitors (PIGMi). This approach would enable the direct delivery of chemotherapeutic agents to the tumor microenvironment (TME), combining their therapeutic effects with the antitumor immunostimulant activity of Lmat, thereby minimizing secondary adverse effects. Additionally, the potential of Lmat as a delivery system for oligonucleotides has been explored, addressing significant challenges in oligonucleotide delivery. While the preliminary outcomes are promising, additional experiments are necessary to validate the method and ascertain the integrity of the oligonucleotide and the viability of Lmat.