One is an American neurologist, the other an Italian epidemiologist, and their work has each, in its own way, revolutionized research into multiple sclerosis, a neurodegenerative disease affecting nearly 3 million people worldwide. Doctors Stephen Hauser and Alberto Ascherio were awarded the Breakthrough Prize on Saturday, April 5, 2025, a sort of "Oscars of science," a recognition for their respective decades of work on this autoimmune disease long considered a total enigma. Both have pushed the boundaries of its understanding, one shedding light on the immune response at its origin and paving the way for treatments, and the other confirming the involvement of a virus. (In 2022, Alberto Ascherio had granted an exclusive interview to Science and Future).
"The most unfair thing I've ever seen in medicine"
The story begins more than 45 years earlier with the meeting of a patient named Andrea, "an extraordinarily talented young woman, who was already a lawyer and worked at the White House", Mr. Hauser recalled to AFP. “Then multiple sclerosis appeared explosively and destroyed his life.”, he says. "I remember seeing her, unable to speak, paralyzed on her right side, unable to swallow, and soon unable to breathe without assistance, and thinking it was the most unfair thing I had ever seen in medicine."A revelation for the then 27-year-old doctor, who decided to devote his life to it.
"At the time, there was no treatment for multiple sclerosis and there was pessimism about the possibility of developing one.", recalls the researcher, now 74 years old and director of the Neuroscience Institute at the University of California (UCSF). We then knew that this disease, which affects the central nervous system and causes disabling motor and cognitive disturbances, was caused by an overactive immune system. But scientists then believed that T lymphocytes, a type of white blood cell, were the only "guilty".
A postulate that Mr. Hauser will challenge. By conducting research with his colleagues on marmosets, he manages to reproduce neurological lesions identical to those observed in humans, thanks to the idea of one of his peers to study the role of B lymphocytes, other types of white blood cells. An implication "biologically implausible", retorts the American agency responsible for medical research, which rejects their request for funding for a clinical trial.
Convinced of their idea, Mr. Hauser and his team managed to realize it thanks to the support of the pharmaceutical laboratory Genentech. And in the summer of 2006, the results came in: the treatments administered to patients and targeting B lymphocytes produced a "dramatic reduction, of more than 90%, in brain inflammation"A revolution that paves the way for the commercialization of treatments that slow the progression of the disease in many patients. But it also raises many other questions, particularly about the mechanism by which white blood cells turn against the body.
Northern Hemisphere Disease
A question at the heart of the reflections of Dr. Alberto Ascherio, now a professor at the prestigious Harvard University, who has investigated the prevalence of cases of multiple sclerosis in the Northern Hemisphere. "The geographical distribution of sclerosis cases is quite striking.", he explains to AFP, the disease being "very uncommon in tropical countries and those close to the equator". In questioning the reasons for such a disparity, Mr. Ascherio considers the possible involvement of a virus. A theory that will prove correct.
After following millions of young people who joined the US military for more than 20 years, the team he leads confirmed in 2022 the link between multiple sclerosis and the very common Epstein-Barr virus, responsible for another well-known disease, infectious mononucleosis. If "Most people infected with the Epstein-Barr virus will never develop multiple sclerosis (…) the disease only occurs in individuals who have been infected with the virus first.", sums up the 72-year-old professor.
Infection is therefore necessary, but does not alone explain the onset of the disease. This discovery revives hopes for the development of new treatments and prevention. To date, multiple sclerosis cannot be cured and treatments that slow its progression are not effective in all patients. This advancement could also benefit other pathologies. "We are now trying to extend our investigation to study the role of viral infection in other neurodegenerative diseases, such as Alzheimer's or Lou Gehrig's disease," explains Mr. Ascherio. A link that is still theoretical, but which has "certain elements" in his favor, assures the epidemiologist.
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