TUESDAY, JUNE 19, 2018

H1N1-triggered narcolepsy caused by "molecular mimicry"

Researchers at Stanford University School Of Medicine said on Wednesday that narcolepsy can be triggered by H1N1 virus in people who are genetically susceptible.

The study showed "molecular mimicry" between a region of hypocretin protein and a protein in H1N1. The mimicry happens when an immune response to a pathogen, such as H1N1, mistakenly attacks a healthy component of the body.

In 2009, researchers at Stanford found that narcolepsy occurs when the body's immune system destroys brain cells that make hypocretin. The newly released study confirmed narcolepsy is an autoimmune disease.

"The relationship between H1N1 infection, vaccination and narcolepsy gave us some very interesting insight into possible causes of the condition," Emmanuel Mignot, a professor of psychiatry and behavioral sciences, said. "In particular, it strongly suggested to us that T cells of the immune system primed to attack H1N1 can occasionally also cross-react with hypocretin and somehow cause the destruction of hypocretin-producing neurons."

Elizabeth Mellins, an immunology researcher and professor of pediatrics at Stanford, said the study will help shape the next steps of narcolepsy research, and possibly lead to information about other autoimmune diseases.

The study provides new ways to intervene before specialized brain cells are destroyed. The study has also provided the first steps to a blood test that could diagnose narcolepsy, and provides information on the association between H1N1 vaccine and increased cases of narcolepsy in Scandinavia in 2009.

"This intersection of genetically susceptible people with a particular environmental trigger, in the form of the H1N1 virus or the Pandemrix vaccine, gave us a powerful scientific opportunity to begin to understand the molecular basis of narcolepsy," Mellins said.

Researchers are looking into the interaction between T cells and hypocretin affect hypocretin neurons, and whether the process could be blocked to prevent narcolepsy. They are also looking into the possibility of brain disorders such as schizophrenia being linked to autoimmunity.

"People have long thought that the brain is somewhat immune to autoimmune diseases," Mignot said, "But we're learning this is wrong. Fortunately, narcolepsy seems to be a very simple disorder to use as a model. There is one HLA molecule involved, and there may be only one target, hypocretin. It will allow us to learn so much more about human autoimmune disorders."