Scientists from Georgia Tech and the Centers for Disease Control and Prevention have discovered surprisingly complex behavior in the Hepatitis C virus. Illustration: iStockPhoto.com.
Warring armies use a variety of tactics to gain the upper hand. Among them: Attacking with a decoy force that occupies the defenders while an unseen force launches a separate attack that the defenders fail to notice.
A study published in the journal Proceedings of the National Academy of Sciences suggests the Hepatitis C virus may employ a similar tactic to distract the body’s natural defenses. After infecting patients, Hepatitis C evolves many variants, among them an “altruistic” group of viral particles that appear to sacrifice themselves to protect other mutants from the body’s immune system.
Reported by researchers from Georgia Tech and the Centers for Disease Control and Prevention (CDC), the findings could help guide development of future vaccines for the virus, which affects an estimated 170 million people worldwide.
“The members of viral populations in Hepatitis C don’t act like separate entities; the different variants work together almost like a team,” said Leonid Bunimovich, a Regents Professor in the Georgia Tech School of Mathematics. “There is a clear separation of responsibilities, including variants we call ‘altruistic’ because they sacrifice themselves for the good of the whole viral population. These variants seem to draw the immune system attack on themselves.”
The scientists first developed a mathematical model for how the virus variants and immune system antibodies interact. They then used the model to analyze and explain data gathered from a group of Hepatitis C patients, some of whom had been followed for as long as 20 years.
The virus evolves differently in each person, producing a mix of genetically related variants. The variants and the antibodies form a complex network in which an antibody to one variant can react to another variant — a phenomenon known as cross-immunoreactivity.
“The virus variants do not communicate directly with one another, but in this system of viruses and antibodies, they interact through the antibodies,” Bunimovich explained. “When one antibody-producing cell responds to one variant, and then to another, that is a form of interaction that affects both variants. An indirect interaction occurs when the virus variants interact with the same antibody in the network.”—JOHN TOON