Our body sets off a chain reaction that disrupts the levels of cholesterol required in cell membranes to enable viruses to enter cells, researchers said.
The findings, discovered by researchers in molecular microbiology and immunology at the Keck School of Medicine, hold promise for the development of therapies to fight a variety of viral infections.
"Previous studies have shown that our bodies are already equipped to block viruses such as Ebola, influenza, West Nile, and SARS," said Jae U Jung, principal investigator and distinguished professor and chair of the Molecular Microbiology and Immunology Department.
"We showed how this occurs. When a virus tries to enter, the immune system gets stimulated by interferon, which produces almost 300 host proteins, including IFITM3," Jung said.
"This protein then disrupts the interaction between two other proteins, which, in turn, significantly increases the level of cholesterol in cells, and thereby blocks the virus," said Jung.
Jung added that the increase in cholesterol is only within the endosome compartment of cells and has no impact on or effect from the level of cholesterol in the bloodstream.
Scientists long have known that interferon, a protein released by the body's cells can inhibit the spread of viruses, but didn't understand how.
Researchers found that interferon-inducible trans-membrane protein 3 (IFITM3) can disrupt the interaction between Vesicle-membrane-associated protein (VAPA) and oxysterol-binding protein (OSBP) that regulates the transport and stability of cholesterol, which are required for many viruses to take hold.
One of the main goals of his lab, Jung said, is to understand how the immune system recognises viruses and blocks entry.
The study was published in the journal Cell Host & Microbe.