A collaborative study led by researchers from the Rochester, USA, has observed how the measles virus mutates and spreads in the human brain, causing a rare and terminal neurological condition called subacute sclerosing panencephalitis (SSPE). “The challenge was to reconstruct the evolution of the virus in the brain, which has never before been attempted,” Dr Roberto Cattaneo, co-lead author of the study, told Happiest Health.
In the study published by Mayo Clinic in the journal PLOS Pathogens, the researcher’s detail how viruses persist and adapt to the human brain. The findings could help develop effective antivirals for SSPE, which currently has no cure.
The comeback
Measles is a highly contagious disease caused by the measles virus. This virus initially infects the upper respiratory tract and then spreads throughout the body, including the brain.
Years after recovering from measles, the virus could get reactivated. An abnormal immune reaction to this reactivation causes swelling and irritation of the brain. The central nervous system is mainly affected in SSPE, initially causing mild cognitive decline and memory loss; seizures, difficulties in movement and behavioural changes follow, eventually turning fatal.
Dr Cattaneo has been studying SSPE for years; he saw the number of cases reducing drastically as more people got vaccinated against measles. However, the tide began to turn when measles came back during the COVID-19 pandemic. During that time, people hesitated to get vaccinated or missed it, causing a spike in measles cases and its complications. “Measles virus is the best-studied example of a human RNA virus that can persist in the brain for years,” Dr Cattaneo notes.
Tracing measles trail
Amidst this resurgence, the team led by Dr Cattaneo and Iris Yousaf, co-lead author of the study, collaborated with the Centre for Disease Control (CDC), USA. Together, they examined the brain tissue samples of a person who had contracted measles as a child and later succumbed to SSPE as an adult. “The CDC confirmed the SSPE diagnosis and prepared the specimens for our analyses,” said Dr Cattaneo. To understand how the measles virus mutated and spread throughout the brain, they studied 15 different brain specimens using modern genetic sequencing.
The researchers saw that once the measles virus infiltrated the brain, its genome (genetic material) replicated, creating different versions of itself. This process repeated, leading to a diverse set of genomes.
In this genome population, two specific genomes came with characteristics that helped the virus (from its initial location at the frontal cortex) to colonise the entire brain. “The first surprise was that there was much more viral RNA than expected in the first specimens we analysed. The biggest surprise was that not one, but two genomes were present in every specimen and virtually in every cell analysed,” remarks Dr Cattaneo.
Vaccine shield
The next steps in this research involve understanding how specific mutations favour the spreading of virus in the brain. They plan on using brain cells and organoids for this. However, they emphasise that vaccination can prevent these complications. “Pharmacological intervention in advanced disease stages is challenging. SSPE prevention through measles vaccination remains the best option,” Dr Cattaneo says.
