Recently, researchers from the Mayo Clinic and other research institutions in the United States conducted a detailed mapping of the brain of a patient who died of a rare subacute sclerosing Penephalitis (SSPE) with measles virus mutations and transmission. The findings were published this week in the journal Plos Pathogens, titled "Brain Tropism Acquisition: The Spatial Dynamics and Evolution of a Measles Virus Collective Infectious Unit That Drove Lethal Subacute Sclerosing." panencephalitis" (Viral affinity acquisition in the brain: spatial dynamics and evolution of the collective infectious unit of measles virus that causes fatal subacute sclerosing Penephalitis).
The number of measles cases has decreased dramatically due to vaccination, among other reasons. However, infection rates have started to rise due to factors such as vaccine hesitancy and unvaccination. The U.S. Centers for Disease Control and Prevention (CDC) estimates that millions of children were not vaccinated against measles during the COVID-19 pandemic, resulting in an increase in infection rates of about 18.
About 1 in 10,000 cases of measles will develop SSPE. From initial infection until the measles virus mutates and spreads throughout the brain, it can take five to ten years. When this happens, patients experience symptoms such as memory loss, epilepsy, and movement disorders. As the number of unvaccinated people increases and measles infections increase, cases of SSPE may also increase.
Mayo scientists, in collaboration with CDC and others, studied the autopsied brain of a 24-year-old man who contracted measles as a child and later developed SSPE as an adult. They collected and deeply sequenced the viral RNA of 15 specimens from different areas of the patient's brain to figure out how the measles virus mutated and spread.
Their analysis revealed that the virus replicated in the brain, producing multiple genomes that were slightly different from each other. The replication of each individual's genome results in a diverse population of viral genomes in the brain. In this group, the researchers identified two specific genomes that accumulate mutations suitable for specific features that prompt the spread of the virus from the frontal lobe, where migration began, to other parts of the brain. "Most infected cells carry both genomes, suggesting the possibility of genetic complementarity," they wrote.
Although the study focused on measles, scientists look forward to the broader implications of their work. "Our study provides robust data showing how viral RNA mutates and spreads in human organs – in this case, the brain," said Dr. Roberto Catan'o, a virologist at the Mayo Clinic and co-author of the study. "Our findings will help to study and understand how other viruses persist and adapt to the human brain, triggering disease. He added that the findings could also "facilitate the production of effective antiviral drugs."
For the next step, the scientists plan to study how the identified specific genomic mutations allow the virus to spread in the brain. They will conduct these studies using cultured brain cells as well as brain organ-like structures.
Reference: "Brain Tropism Acquisition: The Spatial Dynamics and Evolution of a Measles Virus Collective Infectious Unit that Drove Lethal Subacute Sclerosing Panencephalitis."”
Editor: Wang Hong.
Typesetting: Li Li.