Latest news with #KatherineRalston
Yahoo
18-05-2025
- Health
- Yahoo
Common Parasite Rips The Face From Your Cells to Wear as a Disguise
New research has shown how the parasitic amoeba Entamoeba histolytica takes bites from your cells to use as a disguise, hiding them from the immune system. Entering the body via contaminated food or water, most infections from the parasite cause diarrhea, if any symptoms at all. In particularly bad cases, the amoeba can spread via the bloodstream to other vital organs, where it can cause serious problems. If the infection reaches the liver, for instance, the amoebic abscesses it creates can be fatal, causing complications that claim the lives of almost 70,000 people each year. Exactly how this tiny monster wreaks such havoc in its host was largely unknown, until microbiologist Katherine Ralston – currently at the University of California Davis, but back then posted at the University of Virginia – investigated the amoeba more closely in 2011. The going theory was that E. histolytica injected a poison into its victim cells. But Ralston saw something very different going on through her microscope. E. histolytica was taking what looked like actual bites out of human cells. "To devise new therapies or vaccines, you really need to know how E. histolytica damages tissue," Ralston says. "You could see little parts of the human cell being broken off." Stranger still, the amoeba seemed satisfied with just a few chomps from each cell's membrane before moving on to its next victim, leaving in its wake a slew of half-chewed cells with cytoplasms oozing from their puncture wounds. "It can kill anything you throw at it, any kind of human cell," Ralston says. It can even take a chomp out of the white blood cells that are meant to swallow such intruders. Now, Ralston and her colleagues Maura Ruyechan and Wesley Huang have discovered this seemingly wasteful habit actually allows E. histolytica to gather outer membrane proteins from the human cells, which it proceeds to arrange on the surface of its own body for protection against defences in the blood. Surprisingly, this disguise doesn't just protect it from human immune 'guards': it works on immune responses present in the blood of other species, too. "It has become clear that amoebae kill human cells by performing cell nibbling, known as trogocytosis," the authors write. "After performing trogocytosis, amoebae display human proteins on their own surface and are resistant to lysis [rupture] by human serum [a component of blood]." This molecular disguise prevents our immune system from launching an attack on the amoeba by presenting chemical tags that identify it as safe, a bit like stealing the ID off a security guard. When E. histolytica dons the human proteins CD46 and CD55, it can safely scoot past the 'complement proteins' tasked with tracking down and destroying foreign cells. This allows it to continue chomping away, forming abscesses full of liquified cells in the organs it inhabits. Intriguingly, the team conducted an experiment in which they allowed the amoeba to collect material from human cells before exposing the 'disguised' parasites to mouse blood serum. "Although mice are not a natural host of E. histolytica, experimental infection of mice with amoebae mimics many aspects of the human infection, ranging from immune responses to the host genetic determinants of susceptibility to infection," the authors write. Its camouflage was effective despite originating from an entirely different species, reflecting similarities between human and mouse complement protein security systems. This knowledge will allow the researchers to further investigate treatments and vaccines for the amoeba using mouse models, before proceeding to human trials. "Science is a process of building," Ralston says. "You have to build one tool upon another, until you're finally ready to discover new treatments." This research has not yet been peer-reviewed, but it is available as a pre-print in bioRxiv. Scientists '3D Print' Material Deep Inside The Body Using Ultrasound The Secret to Happiness Seems to Depend Upon You, Study Finds Drinking Alcohol Before Hitting The Sauna Could Be a Deadly Combo
Newsweek
13-05-2025
- Health
- Newsweek
Parasite Kills Human Cells and Wears Their Remains As Disguise
Based on facts, either observed and verified firsthand by the reporter, or reported and verified from knowledgeable sources. Newsweek AI is in beta. Translations may contain inaccuracies—please refer to the original content. For decades scientists have been puzzled by a tiny parasite that affects millions worldwide, with the power to liquefy human organs and evade the immune system in ways that science hasn't been able to explain. Now University of California, Davis microbiologist professor Katherine Ralston and her team, have uncovered its terrifying secret. Entamoeba histolytica has the unusual ability to kill human cells and then wear them as a disguise to escape the immune defenses. The research, the teams said, could pave the way for new treatments to stop the parasite once and for all. Image shared on the UCDAVIS website shows E. histolytica (green) attacking human T-cells (white blood cells). Image shared on the UCDAVIS website shows E. histolytica (green) attacking human T-cells (white blood cells). Katherine Ralston What Is Entamoeba histolytica? Entamoeba histolytica is a single-celled parasite infects around 50 million people each year and claims some 70,000 lives annually. Mostly encountered in developing countries with poor water sanitation, the shape-shifting amoeba typically enters a person's colon after ingesting contaminated food or water. While, in most cases, such an infection causes nothing worse than diarrhea, they can sometimes become deadly. Once inside the body, it chews in ulcers inside the colon, liquefying parts of the liver and invading the brain and lungs. In developed countries like America, Entamoeba histolytica infections are rare, although they still account for at least five deaths per year. The parasite is usually brought into the U.S. by individuals who have picked up an infection abroad. How Entamoeba histolytica Operates Scientists used to believe that the parasite injected poison into human cells to kill them, but Ralston's research revealed a very different process. Back in 2011, during her postdoctoral fellowship at the University of Virginia, Ralston observed the parasite under a microscope and found that it was actually taking bites out of human cells. In a series of later studies, she discovered that this amoeba kills cells through a process called "trogocytosis"; after it's done chewing on human cells, it wears the remains as a disguise to trick the immune system into not fighting it. What the Study Showed While researchers have struggled to study this parasite effectively because of its massive genome, Ralston and her team have drafted an "RNAi library" that allows them to study each one of the parasite's 8,734 known genes to understand how it operates. Using a gene-editing tool known as CRISPR, Ralston and her team aim to label proteins within the parasite with fluorescent markers. This should allow them to observe the interactions of said protiens under a microscope. Gene editing may also allow to team to delete small parts of Entamoeba histolytica's genes and proteins to find which are crucial and how they could be targeted with drugs. "We now see a light at the end of the tunnel, and we think this could be achievable," said study author and UC Davis biochemist Wesley Huang. Do you have a tip on a health story that Newsweek should be covering? Do you have a question about parasites? Let us know via science@ References Bettadapur, A., Hunter, S. S., Suleiman, R. L., Ruyechan, M. C., Huang, W., Barbieri, C. G., Miller, H. W., Tam, T. S. Y., Settles, M. L., & Ralston, K. S. (2021). Establishment of quantitative RNAi-based forward genetics in Entamoeba histolytica and identification of genes required for growth. PLOS Pathogens, 17(11). Huang, W., Ruyechan, M. C., & Ralston, K. S. (2025). Work with me here: Variations in genome content and emerging genetic tools in Entamoeba histolytica. Trends in Parasitology, 41(5), 401–415. Miller, H. W., Tam, T. S. Y., & Ralston, K. S. (2022). Entamoeba histolytica Develops Resistance to Complement Deposition and Lysis after Acquisition of Human Complement-Regulatory Proteins through Trogocytosis. mBio, 13(2). Ralston, K. S., Solga, M. D., Mackey-Lawrence, N. M., Somlata, Bhattacharya, A., & Petri, W. A. (2014). Trogocytosis by Entamoeba histolytica contributes to cell killing and tissue invasion. Nature, 508(7497), 526–530. Ruyechan, M. C., Huang, W., & Ralston, K. S. (2024). Cross-species protection suggests Entamoeba histolytica trogocytosis enables complement resistance through the transfer of negative regulators of complement activation (p. 2024.10.04.616735). bioRxiv.
Yahoo
12-05-2025
- Health
- Yahoo
This parasite rips apart human cells and wears them as disguises
Entamoeba histolytica is a particularly tenacious parasite. The single-celled amoeba generally arrives in the colon after contaminated water and food is ingested—most often in places with poor sanitation infrastructure. Although the majority of the 50 million people who contract it each year suffer from little more than diarrhea, around 50,000–100,000 of them don't survive the encounter. In those cases, E. histolytica chews ulcers into the colon walls before moving on to melt away parts of the liver. From there, the amoeba spreads into the lungs and brain, where its destruction ultimately proves fatal. For decades, E. histolytica has stumped researchers struggling to explain how the parasite so successfully evades the immune system. But after about two decades of research, a team of microbiologists have finally determined E. histolytica's gnarly strategy: The parasite has a tendency to cloak itself in remnants of dead human cells as a disguise against the body's immune system. Now, microbiologists think they have a plan to fight back. Their amoeba battle strategy is detailed in a study published in the May issue of Trends in Parasitology. 'All parasites are understudied, but E. histolytica is especially enigmatic,' University of California, Davis microbiologist Katherine Ralston explained in a university profile on May 12. 'It can kill anything you throw at it, any kind of human cell.' Ralston is the new paper's first author, but she first began studying E. histolytica during her postdoctoral fellowship in 2011. 'You could see little parts of the human cell being broken off,' Ralston said of her very first encounter with the parasite. In 2014, she published her initial findings in Nature on the process, known as trogocytosis. 'This was important [to discover],' she said. 'To devise new therapies or vaccines, you really need to know how E. histolytica damages tissue.' It didn't take long for Ralston to see firsthand how the amoeba can become an absolutely voracious and impatient menace. E. histolytica doesn't consume cells as much as it takes bites out of them as it travels through organs. These wounded cells are left to leak out its contents as E. histolytica moves on to its next targets—hence its name. Histolytica translates to 'tissue-dissolving.' In 2022, Ralston discovered a major reason behind the parasite's tenacity: the amoeba develops an ability to evade a crucial part of the human immune system known as complement proteins. These proteins are vital to identifying and eradicating foreign cells. To escape them, E. histolytica ingests specific proteins from human cell outer membranes, then places those proteins on its own outer surface. Two of those molecules block those important compliment proteins from attaching themselves and fighting back. Essentially, E. histolytica wears chunks of human cells as a disguise against its host's immune system. However, yet another complication to taming E. histolytica remained—its complexity. The pathogen's genomic sequence is five times larger than salmonella's and 2,500 times larger than HIV's. While scientists sequenced E. histolytica's genomic sequence in 2005, it took eight years for researchers to analyze the bioinformation thoroughly enough to identify a potential breakthrough in controlling the parasite. In 2013, a separate study indicated E. histolytic displayed a cellular process known as RNA inhibition (RNAi) to control its gene expression. Fast forward another eight years, when Ralston's team created an RNAi library that finally allowed experts to selectively inhibit each of the parasite's 8,734 genes. Ralston's latest study presents one of the most promising steps yet in combatting E. histolytic: a battle plan. The team proposes combining their RNAi library with CRISPR gene-editing technology in order to label certain amoeba proteins with fluorescent markers. Researchers can then watch how E. histolytica interacts with the proteins before altering or deleting various proteins and genes. From there, they may be able to identify which portions are crucial to the amoeba's proliferation and disguise. By eventually targeting these with tailored drugs, researchers could soon halt E. histolytica's rampage. 'We now see a light at the end of the tunnel, and we think this could be achievable,' said Wesley Huang, one of the new study's co-authors along with Maura Ruyechan. With nearly all the pieces in place, scientists are another step closer to developing vaccines and drug regimens to take on E. histolytica. Despite their size, dealing with microscopic problems like this one often takes years to accomplish. 'Science is a process of building,' said Ralston. 'You have to build one tool upon another, until you're finally ready to discover new treatments.'
