Pittsburgh scientists have cooked up an experimental "living eye drop" that recruits a normally harmless bacterium already living on the eyeball to deliver an anti-inflammatory protein right where the eye is injured. In mouse tests, the tweaked Corynebacterium mastitidis sped up corneal wound closure compared with saline and with unmodified bacteria, hinting that a single treatment could last much longer than standard drops. The team is quick to point out that this is very early-stage work and has not yet been tried in humans.
Proof-of-concept in Cell Reports
The proof-of-concept study, detailed in Cell Reports, describes engineered C. mastitidis that continuously secrete the anti-inflammatory cytokine interleukin-10 (IL-10). In a mouse corneal injury model, this constant IL-10 output sped up repair of the corneal epithelium. When researchers blocked the IL-10 receptor on the eye, the healing advantage disappeared, confirming that the benefit depended on IL-10 signaling. The work stays firmly in the realm of lab and animal data and does not make any clinical efficacy claims.
What the Pitt team says
"This is the first demonstration that a microbe that lives on the ocular surface could be engineered to deliver a therapeutic," senior author Anthony St. Leger said, according to the University of Pittsburgh School of Medicine. The group also created a version of the bacterium that secretes human IL-10, which boosted wound closure in lab-grown human corneal cells and tamped down inflammatory signaling in human immune cells. They describe the setup as a modular platform, meaning different genes could be swapped in to go after a range of ocular surface problems.
Why a living drop could matter
Tears routinely flush away eye medications, which is why people with corneal abrasions or chronic dry-eye issues often find themselves reaching for drops multiple times a day. According to the National Eye Institute, the modified microbes in this study might instead provide sustained therapy on the eye’s surface rather than forcing hourly re-dosing. Traumatic injuries to the ocular surface hit more than a million Americans every year, and a living biotherapeutic could ease some of that burden, as noted by the Charlotte Observer.
Next steps: safety, off-switches and trials
The researchers say several more iterations are likely before they even think about testing the approach in people, and that a key challenge will be building a dependable way to shut down the therapeutic protein or clear the bacteria once treatment is done, the University of Pittsburgh reports. Backed by NIH support, the team plans to hardwire in biological "off-switches" and other safety controls before moving toward any clinical translation. The strategy leverages earlier work showing that C. mastitidis can tune protective immune responses on the eye’s surface, as reported in a 2017 Immunity paper, but turning a lab-built microbe into an approved human therapy will require a long run of additional lab, preclinical, and regulatory testing.
