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What if we were able to create a needle so small it could inject a protein directly into a single cell? That would be a huge leap forward for vaccine technology, because one way our immune cells learn to recognize enemies is by their proteins. And getting proteins inside cells is really tricky.
Believe it or not, the microneedle in question may soon be possible. But it isn’t made by a medical device company. It’s made by a kind of organism we often think of as making us sick: bacteria.
Using a microscopic harpoon-like structure, some species of bacteria can inject their enemies with toxic proteins as part of their natural defense systems. Scientists have been studying how we might use these weapons in our favor to modify the bacteria to inject useful proteins inside human immune cells.
This could provide us with self-manufacturing vaccines, as the bacteria multiply rapidly and make fresh proteins for delivery, eliminating the need to isolate and purify antigens. Antigens are protected from degradation due to their stability when inside bacteria, allowing them to be syringed into immune cells. This process, called attenuation, involves modifying the bacteria to remove any natural toxins and to make sure they can’t reproduce. Scientists also add DNA to the bacteria, instructing them to make new, useful proteins and to secrete them. This research has been used to deliver a variety of antigens into immune cells, and even to create a new COVID-19 vaccine. Additionally, good bacteria can deliver the antigens of bad bacteria to our immune cells, and there are several vaccines in development targeting Listeria monocytogenes. A bacteria-based vaccine to prepare immune cells to attack multiple myeloma begins Phase One clinical trials later this year. In 2013, attenuated E. coli was used to secrete nanobodies into breast cancer cells in mice, reducing tumor metastasis. Salmonella bacteria are also attracted to tumors, and research has been conducted on their secretion systems for potential use in fighting cancer cells. Bacteria’s ability to deliver proteins inside cells could be a huge benefit to us, and someday soon, medicine could be delivered right to the source of the problem by a bacterium with a tiny needle.
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