With the receptor identified, a therapy can be developed that will bind to the receptor, preventing the deadly immune response. Also, by targeting a receptor in humans rather than a particular strain of flu, therapies developed to exploit this discovery would work regardless of the rapid mutations that beguile flu vaccine producers every year.
This discovery could lead to treatments which turn off the inflammation in the lungs caused by influenza and other infections, according to a study published today in the journal Nature Immunology. The virus is often cleared from the body by the time symptoms appear and yet symptoms can last for many days, because the immune system continues to fight the damaged lung. The immune system is essential for clearing the virus, but it can damage the body when it overreacts if it is not quickly contained.
The immune overreaction accounts for the high percentage of young, healthy people who died in the vicious 1918 flu pandemic. While the flu usually kills the very young or the sickly and old, the pandemic flu provoked healthy people’s stronger immune systems to react even more profoundly than usual, exacerbating the symptoms and ultimately causing between 50 and 100 million deaths world wide. These figures from the past make the new discovery that much more important, as new therapies based on this research could prevent a future H5N1 bird flu pandemic from turning into a repeat of the 1918 Spanish flu.
In the new study, the researchers gave mice infected with influenza a mimic of CD200, or an antibody to stimulate CD200R, to see if these would enable CD200R to bring the immune system under control and reduce inflammation.
The mice that received treatment had less weight loss than control mice and less inflammation in their airways and lung tissue. The influenza virus was still cleared from the lungs within seven days and so this strategy did not appear to affect the immune system’s ability to fight the virus itself.
The researchers hope that in the event of a flu pandemic, such as a pandemic of H5N1 avian flu that had mutated to be transmissible between humans, the new treatment would add to the current arsenal of anti-viral medications and vaccines. One key advantage of this type of therapy is that it would be effective even if the flu virus mutated, because it targets the body’s overreaction to the virus rather than the virus itself.
In addition to the possible applications for treating influenza, the researchers also hope their findings could lead to new treatments for other conditions where excessive immunity can be a problem, including other infectious diseases, autoimmune diseases and allergy.