Lysocins: Bioengineered Antimicrobials That Deliver Lysins across the Outer Membrane of Gram Negative Bacteria
The prevalence of multidrug resistant Pseudomonas aeruginosa has stimulated development of alternative therapeutics. Bacteriophage peptidoglycan hydrolases, termed lysins, represent an emerging antimicrobial option for targeting Gram positive bacteria. ABSTRACT The prevalence of multidrug resistant Pseudomonas aeruginosa has stimulated development of alternative therapeutics. Bacteriophage peptidoglycan hydrolases, termed lysins, represent an emerging antimicrobial option for targeting Gram positive bacteria. However, lysins against Gram negatives are generally deterred by the outer membrane and their inability to work in serum. One solution involves exploiting evolved delivery systems used by colicin like bacteriocins (e.g. S type pyocins of P. aeruginosa) to translocate through the outer membrane. Following surface receptor binding, colicin like bacteriocins form Tol or TonB dependent translocons to actively import bactericidal domains through outer membrane protein channels. With this understanding, we developed lysocins, which are bioengineered lysin bacteriocin fusion molecules capable of periplasmic import. In our proof of concept studies, components from the P. aeruginosa bacteriocin pyocin S2 (PyS2) responsible for surface receptor binding and outer membrane translocation were fused to the GN4 lysin to generate the PyS2 GN4 lysocin. PyS2 GN4 delivered the GN4 lysin to the periplasm to induce peptidoglycan cleavage and log fold killing of P. aeruginosa with minimal endotoxin release. While displaying narrow spectrum antipseudomonal activity in human serum, PyS2 GN4 also efficiently disrupted biofilms, outperformed standard of care antibiotics, exhibited no cytotoxicity toward eukaryotic cells, and protected mice from P. aeruginosa challenge in a bacteremia model. In addition to targeting P. aeruginosa, lysocins can be constructed to target other prominent Gram negative bacterial pathogens.
Antimicrobial Agents and Chemotherapy