You may be aware of the idea that there is an accumulation of microbes – fungi, bacteria, and viruses – in your gut and on your skin that are critical to your health. But did you know that your eyes also house a unique microbial mangerie?
Together they are called the eye microbiome. When these microbes are out of balance – too many or too few specific types – eye diseases can occur.
A recent study has shown that bacteria live on the surface of the eye and stimulate protective immunity, and scientists are beginning to discover the microbes as factors that can be exploited to provide innovative therapies for a range of eye conditions to develop dry eye disease, Sjögren syndrome and corneal scars.
One day, bacteria could be developed to treat human eye diseases.
I & # 39; I am an immunologist who investigates how the eye prevents infection. I was interested in this area because people have only two eyes and understanding how bacteria affect immunity may be the key to avoid up to 1
] Eye Microbiome
When discussing the microbiome, most scientists usually think of the intestine, and rightly so. Researchers believe that a large intestine can harbor more than 10 trillion bacteria. Against this background, attention is increasingly being paid to the effects of micro-organisms in other areas such as the skin and in areas with very few bacteria such as the lungs, the vagina and the eyes.
Over the last decade, the role of the microbiome in eye health has been controversial. Scientists believed that healthy eyes lacked an organized microbiome. Studies have shown that bacteria from the air, the hands or the eyelid margins can be present on the eye. However, many believed that these microbes were simply killed or washed away by the constant flow of tears.
More recently, scientists have discovered that the eye actually has a "core" microbiome that appears to be dependent on age, geographic region, ethnicity, contact lens wear, and disease state.
The "nucleus" is limited to four bacterial genera staphylococci diphtheroids propionibacteria and streptococci . In addition to these bacteria, the Torque Teno virus, which is involved in some intraocular diseases, is also a nuclear microbiome as it is present in 65% of healthy individuals on the ocular surface.
This encourages the doctor to do so. When prescribing antibiotics, think about the risks and benefits to the microbiome. The antibiotics can kill bacteria that are beneficial to the eye.
In a recent study that spanned more than a decade and involved more than 340,000 patients in the US, the authors found that antibiotics were used to treat 60 percent of acute illness cases of conjunctivitis (pink eye).
However, viral infections are the most likely causes of pink eye and are not treatable with antibiotics. More conspicuous, even bacterial, cases often resolve within 7 to 10 days without intervention. It is well known that excessive or inappropriate use of antibiotics can disrupt the microbiome and lead to infections, autoimmunity and even cancer.
Discovery of an ocular colonizing microbe
Studies investigating the microbiome and the disease of the eye have seen a boom in the last decade. They have generated an immense amount of data that, however, is largely correlated.
This means that certain bacteria have been implicated in certain diseases such as Sjögren's syndrome or bacterial keratitis. Whether these bacteria cause these diseases, however, is not yet known.
During my time at the National Eye Institute, I used mice to see if bacteria on the surface of the eye could trigger an immune response to protect the eye from dying pathogens like the bacterium Pseudomonas aeuruginosa .
In 2016, the eye immunologist Rachel Caspi of the National Eye Institute and I hypothesized that protective bacteria live near or at the eye. In fact, we found a resident bacterium, Corynebacterium mastitidis ( C. Mast ), which stimulates immune cells to produce and release antimicrobial factors that kill harmful microbes in the tears.
In a series of experiments, a causal connection between C was detected for the first time in the Caspi laboratory. Mast and a protective immune response. Whenever C. Mast was present on the ocular surface, mice were more resistant to two types of bacteria known to cause blindness: Candida albicans and Pseudomonas aeuruginosa .
Laboratory we would like to take advantage of this relationship between C. Mast and Eye Immunity to develop novel therapies to prevent infections and potentially target more common diseases such as Dry Eye Disease.
Development of Microbes to Improve Eye Health
The first step in developing such therapies is to find out how bacteria colonize the eye. To do this, my lab works with the Campbell Laboratory at the University of Pittsburgh, which houses one of the largest collections of human eye bacteria in the country.
We Can Do It Thanks to Our Unique Mice Experiment and Advanced Genetic Analysis Use this microbial library to identify specific factors required to colonize the ocular surface.
Then we start with ophthalmologists and opticians in the UPMC Eye Center to analyze the immune signatures in the eyes of healthy people and sick patients.
We hope to use this technology as a new diagnostic tool to fight disease-causing microbes rather than immediately treating infections with broad-spectrum antibiotics that also kill good microbes.
Our ultimate goal is genetically engineering ocular colonizing bacteria to act as a vehicle for long-term delivery to the surface of the eye. Genetically modified bacteria in the gut have been proven to relieve diseases such as colitis.
We hope that this new "prob-eye-otic" therapy will secrete immunoregulatory factors that limit symptoms in diseases such as dry eye disease, which affects around 4 million people every year in the US.
There is still much to learn in this developing field before physicians can begin to manipulate the microbiome of the eye to fight disease. But maybe one day, instead of just injecting eye drops into your dry eyes, you inject a solution with some bacteria that colonize your eye and secrete the lubricants and other factors that your body lacks. Stay tuned.
Tony St. Leger, Assistant Professor of Ophthalmology and Immunology, University of Pittsburgh.
This article was re-published by The Conversation under a Creative Commons license. Read the original article.