# 1688
RBD's are receptor binding domains, that area of a virus that allows it to attach to receptor cells in a host's body. Different viruses are attracted to different types of cells, which explains why some viruses that affect man, don't affect other species, or vice versa.
Receptor cells have strands of sugar (carbohydrate) molecules on their surface. These carbohydrate molecules - called glycans' - form a dense sugary coating to all animal cell membranes.
When a virus meets a compatible receptor cell, they bind. And infection ensues.
Researchers have been studying variants of the 1918 H1N1 virus, trying to determine why some strains are highly contagious, while others aren't infectious at all.
It turns out the difference is just two small amino acid substitutions.
This from Science Daily.
Spread Of 1918 Flu Pandemic Explained
ScienceDaily (Feb. 19, 2008) — MIT researchers have explained why two mutations in the H1N1 avian flu virus were critical for viral transmission in humans during the 1918 pandemic outbreak that killed at least 50 million people.
The team showed that the 1918 influenza strain developed two mutations in a surface molecule called hemagglutinin (HA), which allowed it to bind tightly to receptors in the human upper respiratory tract.
"Two mutations dramatically change the HA binding affinity to receptors found in the human upper airways," said Ram Sasisekharan, the Underwood Prescott Professor of Biological Engineering and Health Sciences and Technology.
Sasisekharan is the senior author of a paper on the work to be published in the Feb. 18 issue of the Proceedings of the National Academy of Sciences. In January, Sasisekharan and colleagues reported in Nature Biotechnology that flu viruses can only bind to human respiratory cells if they match the shape of sugar (or glycan) receptors found on those cells.
The glycan receptors found in the human respiratory tract are known as alpha 2-6 receptors, and they come in two shapes-one resembling an open umbrella, and another resembling a cone. To infect humans the MIT team found that avian flu viruses must gain the ability to bind to the umbrella-shaped alpha 2-6 receptor.
In the current study, the team discovered that two mutations in HA allow flu viruses to bind tightly or with high affinity to the umbrella-shaped glycan receptors.
"The affinity between the influenza virus HA and the glycan receptors appears to be a critical determinant for viral transmission," said Sasisekharan.
(Cont.)
Adapted from materials provided by Massachusetts Institute of Technology.
Massachusetts Institute of Technology (2008, February 19). Spread Of 1918 Flu Pandemic Explained. ScienceDaily. Retrieved February 19, 2008, from http://www.sciencedaily.com /releases/2008/02/080218172441.htm
