Akin to the way chainmail's tight weave repels an attacking sword blade, the blood-brain barrier keeps guard of our brain by involving the capillaries in a kind of biological weave that's too restrictive to allow most pathogens to pass through.
The system is ingeniously designed to prevent large molecules like pathogens, drugs, and immune cells from reaching the brain but allows critical substances like amino acids and glucose to nourish the brain. Occasionally, however, a virus or bacteria can sneak through and wreak havoc on one of our most treasured organs.
Researchers at St. Louis' Washington University School of Medicine have recently discovered an antiviral compound produced naturally in the body that, when applied in large enough doses, serve to tighten the blood-brain barrier enough to prevent a particularly small pathogen-the West Nile virus-from slipping through the system to the brain.
The researchers observed that mice lacking the interferon-lambda receptor had significantly higher occurrence of West Nile in the brain. The blood-brain barrier in these mice was much more permeable to the virus, suggesting that the lack of interferon-lambda receptor function was impacting the barrier's ability to repel the virus.
When given the virus and a dose of interferon-lambda, mice survived at twice the rate-from 20 percent to 40 percent.
Michael Diamond, one of the study's authors, said of the result: "Viruses are most dangerous when they enter the brain. Compared with untreated mice, we found significantly lower concentrations of the virus in the brain among mice treated with interferon-lambda."
Diamond said that using interferon-lambda as a treatment could reduce side effects like chills, fatigue, and fever, because it has significantly fewer receptors in the body than other forms of interferon, which have also demonstrated potential for assisting the blood-brain barrier: "It's also possible that interferon-lambda may influence other protective barriers in the body, such as those in the skin and the gut, an area of research my laboratory is investigating."
The researchers believe this development could lead to influencing the blood-brain barrier in ways that might help prevent invading cells such as those that cause multiple sclerosis, and even to treat disease such as brain cancer since the barrier could be opened to allow chemotherapy drugs to work directly on tumors.
Robyn Klein, co-author of the study, said: "We have identified a new antiviral function of interferon-lambda that doesn't involve directly attacking a virus but stems viral invasion into the brain. This suggests the possibility of multiple new applications. We're testing one of these right now, conducting studies in mice to see if interferon-lambda can help prevent brain inflammation in a mouse model of multiple sclerosis."
Findings from the study are available online in Science Translational Medicine.
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(Sources: Washington University; Science Daily)