Researchers at La Trobe University have discovered a biological process that sheds light on how viruses move through the body and persist during infection. The finding, published in Nature Communications, reveals that dying cells leave behind a trail of microscopic particles that can inadvertently help pathogens spread while concealing them from immune detection.
When cells die, they undergo a carefully orchestrated breakdown sequence. Scientists observed that dying cells change shape, detach from surrounding structures, and leave behind residue containing previously unknown particles called F-ApoEVs, or "footprints of death."
These F-ApoEVs are a newly identified type of extracellular vesicle, which are microscopic particles that cells release to communicate with one another. The new discovery reveals that these vesicles remain at the site of cell death and serve as signals for the immune system to locate and remove cellular debris before it can trigger damaging inflammation.
The research team, led by PhD candidate Stephanie Rutter under the direction of Professor Ivan Poon at La Trobe Institute for Molecular Science, found the process far more complex than previously understood. Scientists had long assumed cell breakdown during death was essentially random and straightforward.
The Viral Loophole
The troubling discovery emerged when researchers examined what happens in cells infected with influenza. Viral particles were able to exploit the body's natural cleanup mechanism by hiding inside F-ApoEVs. This allows infection to spread from cell to cell while remaining masked within the normal cellular disposal process.
"We didn't expect was how viruses can also take advantage of this process and cause infection by hiding in F-ApoEVs," Rutter said.
The immune system normally clears away dead cell fragments to prevent them from triggering inflammation and autoimmune conditions like Systemic Lupus Erythematosis. But when viruses commandeer these vesicles, they exploit a fundamental protective mechanism against their own advantage.
Professor Poon said understanding this basic biological process opens pathways for developing new treatments. Billions of cells die each day as part of normal tissue turnover and disease progression. The discovery that each step of the cell death process plays a critical role could lead to therapies that help the immune system fight disease more effectively.
"Understanding this basic biological process could open new avenues of research to develop new treatments that harness these steps and help the immune system better fight disease," Poon said.
The research team believes the work has implications beyond viral infections. The discovery could improve understanding of autoimmune disorders where the body fails to properly clear dead cells, as well as infectious diseases where viruses exploit cellular communication. Co-leader Dr. Georgia Atkin-Smith of WEHI noted that dying cells can "continue to communicate from the grave and may impact immune function."
The study involved collaboration between researchers at La Trobe University's Research Centre for Extracellular Vesicles, the Institute for Molecular Science, and the School of Agriculture, Biomedicine and Environment, along with scientists from WEHI and Toronto Metropolitan University in Canada.
Author Jessica Williams: "This discovery reframes how we think about cell death, turning what looked like a simple cleanup process into something viruses have learned to exploit, which could force us to rethink how we develop antivirals."
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