Researchers on the McGovern Institute for Brain Research at MIT and the Broad Institute of MIT and Harvard have harnessed a natural bacterial system to develop a latest protein delivery approach that works in human cells and animals. The technology, described today in , will be programmed to deliver a wide range of proteins, including ones for gene editing, to different cell types. The system could potentially be a secure and efficient method to deliver gene therapies and cancer therapies.

Led by MIT Associate Professor Feng Zhang, who’s a McGovern Institute investigator and Broad Institute core member, the team took advantage of a tiny syringe-like injection structure, produced by a bacterium, thatnaturally binds to insect cells and injects a protein payload into them. The researchers used the factitious intelligence tool AlphaFold to engineer these syringe structures to deliver a spread of useful proteins to each human cells and cells in live mice.

“This can be a really beautiful example of how protein engineering can alter the biological activity of a natural system,” says Joseph Kreitz, the study’s first creator, a graduate student in biological engineering at MIT, and a member of Zhang’s lab. “I believe it substantiates protein engineering as a useful gizmo in bioengineering and the event of latest therapeutic systems.”

“Delivery of therapeutic molecules is a significant bottleneck for medicine, and we’ll need a deep bench of options to get these powerful latest therapies into the proper cells within the body,” adds Zhang. “By learning from how nature transports proteins, we were in a position to develop a latest platform that will help address this gap.”

Zhang is senior creator on the study and can also be the James and Patricia Poitras Professor of Neuroscience at MIT and an investigator on the Howard Hughes Medical Institute.

Injection via contraction

Symbiotic bacteria use the roughly 100-nanometer-long syringe-like machines to inject proteins into host cells to assist adjust the biology of their surroundings and enhance their survival. These machines, called extracellular contractile injection systems (eCISs), consist of a rigid tube inside a sheath that contracts, driving a spike on the top of the tube through the cell membrane. This forces protein cargo contained in the tube to enter the cell.

On the surface of 1 end of the eCIS are tail fibers that recognize specific receptors on the cell surface and latch on. Previous research has shown that eCISs can naturally goal insect and mouse cells, but Kreitz thought it is perhaps possible to change them to deliver proteins to human cells by re-engineering the tail fibers to bind to different receptors.

Using AlphaFold, which predicts a protein’s structure from its amino acid sequence, the researchers redesigned tail fibers of an eCIS produced by bacteria to bind to human cells. By re-engineering one other a part of the complex, the scientists tricked the syringe into delivering a protein of their selecting, in some cases with remarkably high efficiency.

The team made eCISs that targeted cancer cells expressing the EGF receptor and showed that they killed almost one hundred pc of the cells, but didn’t affect cells without the receptor. Though efficiency depends partially on the receptor the system is designed to focus on, Kreitz says that the findings show the promise of the system with thoughtful engineering.

The researchers also used an eCIS to deliver proteins to the brain in live mice — where it didn’t provoke a detectable immune response, suggesting that eCISs could at some point be used to soundly deliver gene therapies to humans.

Packaging proteins

Kreitz says the eCIS system is flexible, and the team has already used it to deliver a spread of cargoes including base editor proteins (which may make single-letter changes to DNA), proteins which can be toxic to cancer cells, and Cas9, a big DNA-cutting enzyme utilized in many gene editing systems.

In the longer term, Kreitz says researchers could engineer other components of the eCIS system to tune other properties, or to deliver other cargoes similar to DNA or RNA. He also wants to raised understand the function of those systems in nature.

“We and others have shown that this sort of system is incredibly diverse across the biosphere, but they aren’t thoroughly characterised,” Kreitz said. “And we consider this sort of system plays really necessary roles in biology which can be yet to be explored.”

This work was supported, partially, by the National Institutes of Health, Howard Hughes Medical Institute, Poitras Center for Psychiatric Disorders Research at MIT, Hock E. Tan and K. Lisa Yang Center for Autism Research at MIT, K. Lisa Yang and Hock E. Tan Molecular Therapeutics Center at MIT, K. Lisa Yang Brain-Body Center at MIT, Broad Institute Programmable Therapeutics Gift Donors, The Pershing Square Foundation, William Ackman, Neri Oxman, J. and P. Poitras, Kenneth C. Griffin, BT Charitable Foundation, the Asness Family Foundation, the Phillips family, D. Cheng, and R. Metcalfe.