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Scientists Use the Tweaked Genes of a Virus to Halt Vision Loss

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What if you could tweak the genes of a virus to turn its ability to invade cells into a delivery system for eyesight therapy? That’s what researchers at Johns Hopkins School of Medicine say they’ve done by modifying an adenovirus, a type of virus that can infect tissue linings. The cutting edge gene therapy was developed to help those who suffer vision loss from a particular eye disorder—wet age-related macular degeneration (AMD).

Approximately 1.6 million Americans have AMD, the number one cause of vision loss. The disease is characterized by the growth of abnormal blood vessels that leak retinal fluid into the eye and destroy the macula, an area near the retina important for high acuity vision. This gene therapy both reduces fluid buildup and improves vision loss in humans, according to study results published in The Lancet.

The best current treatment for the disease requires injections of antibodies into the retina to suppress vascular endothelial growth factor (VEGF), a protein that is responsible for the growth of blood vessels—which in turn cause leaking fluid. But the problem is that patients must obtain these injections at four- to six-week intervals, or else the disease symptoms return and worsen over time. Peter Campochiaro, a professor of ophthalmology and neuroscience at Johns Hopkins Medicine's Wilmer Eye Institute and one of the authors of the study, explains that during this treatment, if a patient takes too long to get their next injection, the abnormal blood vessel net grows larger and recruits other cells. “That scarring causes permanent decrease in vision,” he tells Mental Floss. So over time, it’s common even for patients in treatment to “end up with less vision.”

His team has been working to make a form of injections that last longer, so patients don’t have to come in as frequently. For phase one of this trial, Campochiaro’s team recruited 19 participants to participate in a 52-week study. He was looking for people “who don’t have great visual potential, but have evidence of the disease process that you can measure in effect,” he says.

Since viruses are naturally good at getting into cells and depositing their genetic material, the researchers decided to modify a virus to deposit a gene that codes for a protein called sFLT01. sFLT01 blocks the factor that causes the abnormal vessels and fluid production. When the modified virus is injected into the eye, “the viral vector enters cells and deposits the gene, and the gene begins to produce the [sFLT01] protein,” he says. The protein binds to VEGF, preventing it from causing vessel growth and subsequent fluid leakage.

The 19 participants were divided into five different groups and given increasing doses of the viral vector. After determining there was no toxicity at the dose-limit of the first three groups, they proceeded to increase the dosage to its highest level.

Of the 11 participants with symptoms judged to be reversible, six showed “a substantial reduction in the fluid,” and four of those six saw “a pretty dramatic effect.” Those patients had big pockets of fluid in their retinas decrease, Campochiaro says. Better yet, the treatment lasted throughout the yearlong study, though the protein numbers peaked at 26 weeks, and then declined slightly (although not enough to reactivate disease symptoms).

In assessing why five patients saw no reduction in fluid, the scientists discovered those patients had pre-existing antibodies to the virus. They theorize that in these patients, the immune system may have killed the viral vector before it could deposit the genes, though they will have to do more research to prove this. This could be a problem in using this particular virus—a carrier virus called AAV2—since some 60 percent of patients tend to have these antibodies.

A possible solution might be to give resistant patients a surgical injection instead. During this procedure, scientists could take out the vitreous—a gel-like substance that gives your eye its round shape—and inject the vector surgically under the retina instead. While patients might prefer not to have surgery, “our data suggests that it doesn’t matter if there’s pre-existing antibodies [with this method],” he says.

Alternately, other viral vectors have proven to be more effective than AAV2, including a variation on the virus, AAV8, which provides better infections of the virus into the cell. Even more promising, the researchers recently finished a four-year study on a lentiviral vector (a totally different group of viruses) “that take [the genes] into the nucleus of the cell and inserts the gene right into the chromosomes,” Campochiaro explains.

His next steps will be to retest the treatment with a longer study period to identify just how long-lasting the effects are, as well as to test higher doses of the viral vector.

But right now, he is just excited that the gene therapy works. “We injected this gene, the gene is producing a protein, and you can measure that protein in the eye over time,” he says.

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Geological Map Shows the Massive Reservoir Bubbling Beneath Old Faithful
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Yellowstone National Park is home to rivers, waterfalls, and hot springs, but Old Faithful is easily its most iconic landmark. Every 45 to 125 minutes, visitors gather around the geyser to watch it shoot streams of water reaching up to 100 feet in the air. The punctual show is one of nature’s greatest spectacles, but new research from scientists at the University of Utah suggests that what’s going on at the geyser’s surface is just the tip of the iceberg.

The study, published in the journal Geophysical Research Letters, features a map of the geological plumbing system beneath Old Faithful. Geologists have long known that the eruptions are caused by water heated by volcanic rocks beneath the ground reaching the boiling point and bubbling upwards through cracks in the earth. But the place where this water simmers between appearances has remained mysterious to scientists until now.

Using 133 seismometers scattered around Old Faithful and the surrounding area, the researchers were able to record the tiny tremors caused by pressure build-up in the hydrothermal reservoir. Two weeks of gathering data helped them determine just how large the well is. The team found that the web of cracks and fissures beneath Old Faithful is roughly 650 feet in diameter and capable of holding more than 79 million gallons of water. When the geyser erupts, it releases just 8000 gallons. You can get an idea of how the reservoir fits into the surrounding geology from the diagram below.

Geological map of geyser.
Sin-Mei Wu, University of Utah

After making the surprising discovery, the study authors plan to return to the area when park roads close for the winter to conduct further research. Next time, they hope to get even more detailed images of the volatile geology beneath this popular part of Yellowstone.

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Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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