Lauvau, G. | Search bioRxiv

bioRxiv2018

Single-step Enzymatic Glycoengineering for the Construction of Antibody-cell Conjugates

Employing live cells as therapeutics is a direction of future drug discovery. An easy and robust method to modify the surfaces of cells directly to incorporate novel functionalities is highly desirable. However, many current methods for cell-surface engineering interfere with cells endogenous properties. Here we report an enzymatic approach that enables the transfer of biomacromolecules, such as a full length IgG antibody, to the glycocalyx on the surfaces of live cells when the antibody is conjugated to the enzymes natural donor substrate GDP-fucose. This method is fast and biocompatible with little interference to cells endogenous functions. We applied this method to construct two antibody-cell conjugates (ACCs) using different immune cells, and the modified cells exhibited specific tumor targeting and resistance to inhibitory signals produced by tumor cells, respectively. Remarkably, Herceptin-NK-92MI conjugates exhibits enhanced activities to induce the lysis of HER2+ cancer cells both ex vivo and in a murine tumor model, indicating its potential for further development as a clinical candidate.

bioengineering↗

bioRxiv2017

Listeria monocytogenes virulence factors are secreted in biologically active Extracellular Vesicles

Outer membrane vesicles produced by Gram-negative bacteria have been studied for half a century but the possibility that Gram-positive bacteria secreted extracellular vesicles (EVs) was not pursued due to the assumption that the thick peptidoglycan cell wall would prevent their release to the environment. However, following discovery in fungi, which also have cell walls, EVs have now been described for a variety of Gram-positive bacteria. EVs purified from Gram-positive bacteriaare implicated in virulence, toxin release and transference to host cells, eliciting immune responses, and spread of antibiotic resistance. Listeria monocytogenes is a Gram-positive bacterium that is the etiological agent of listeriosis. Here we report that L. monocytogenes produces EVs with diameter ranging from 20-200 nm, containing the pore-forming toxin listeriolysin O(LLO) and phosphatidylinositol-specific phospholipase C (PI-PLC). Using simultaneous metabolite, protein, and lipid extraction (MPLEx) multi-omics we characterized protein, lipid and metabolite composition of bacterial cells and secreted EVs and found that EVs carry the majority of listerial virulence proteins. Cell-free EV preparations were toxic to the murine macrophage cell line J774.16, in a LLO-dependent manner, evidencing EV biological activity. The deletion of plcA increased EV toxicity, suggesting PI-PLC can restrain LLO activity. Using immunogold electron microscopy we detect LLO localization at several organelles within infected human epithelial cells and with high-resolution fluorescence imaging we show that dynamic lipid structures are released from L. monocytogenes that colocalize with LLO during infection. Our findings demonstrate that L. monocytogenes utilize EVs for toxin release and implicate these structures in mammalian cytotoxicity.

microbiology↗