Nonclassical antagonism between human lysozyme and AMPs against Pseudomonas aeruginosa.

Combinations of human lysozyme (hLYS) and antimicrobial peptides (AMPs) are known to exhibit either additive or synergistic activity, and as a result, they have therapeutic potential for persistent and antibiotic-resistant infections. We examined hLYS activity against Pseudomonas aeruginosa when combined with six different AMPs. In contrast to prior reports, we discovered that some therapeutically relevant AMPs manifest striking antagonistic interactions with hLYS across particular concentration ranges. We further found that the synthetic AMP Tet009 can inhibit hLYS-mediated bacterial lysis. To the best of our knowledge, these results represent the first observations of antagonism between hLYS and AMPs, and they advise that future development of lytic enzyme and AMP combination therapies considers the potential for antagonistic interactions.

An Adaptable Platform for Directed Evolution in Human Cells.

The discovery and optimization of biomolecules that reliably function in metazoan cells is imperative for both the study of basic biology and the treatment of disease. We describe the development, characterization, and proof-of-concept application of a platform for directed evolution of diverse biomolecules of interest (BOIs) directly in human cells. The platform relies on a custom-designed adenovirus variant lacking multiple genes, including the essential DNA polymerase and protease genes, features that allow us to evolve BOIs encoded by genes as large as 7 kb while attaining the mutation rates and enforcing the selection pressure required for successful directed evolution. High mutagenesis rates are continuously attained by trans-complementation of a newly engineered, highly error-prone form of the adenoviral polymerase. Selection pressure that couples desired BOI functions to adenoviral propagation is achieved by linking the functionality of the encoded BOI to the production of adenoviral protease activity by the human cell. The dynamic range for directed evolution can be enhanced to several orders of magnitude via application of a small-molecule adenoviral protease inhibitor to modulate selection pressure during directed evolution experiments. This platform makes it possible, in principle, to evolve any biomolecule activity that can be coupled to adenoviral protease expression or activation by simply serially passaging adenoviral populations carrying the BOI. As proof-of-concept, we use the platform to evolve, directly in the human cell environment, several transcription factor variants that maintain high levels of function while gaining resistance to a small-molecule inhibitor. We anticipate that this platform will substantially expand the repertoire of biomolecules that can be reliably and robustly engineered for both research and therapeutic applications in metazoan systems.