||Are viruses alive? After more than 25 years of studying the tiny disease-carrying microbes, Michael Lai thinks so.
Viruses are very intelligent. They can think. They do things that we do not expect. They adapt to the environment. They change themselves in order to survive, says Lai, a professor of molecular microbiology and im-munology and Howard Hughes Medical Institute Investigator.
Viruses that cause infection in humans hold a key that allows them to unlock normal molecules (called viral receptors) on a human cell surface and slip inside. Once in, they commandeer the cells nucleic acid and protein-making machinery so that more copies of the virus can be made.
Lai has long probed how these tricky parasites work. He has been especially interested in RNA viruses, which carry their genetic blueprints in what scientists have long considered a flimsy coin. Because of the way RNA is copied, it is more prone to mistakes in the genetic code and, unlike DNA, the new copy of RNA is never proofread and corrected.
Recently, Lai has shifted much of his research efforts to the hepatitis C virus.
Hepatitis C, an RNA virus that attacks liver cells, spreads mainly through blood products and intimate sexual contact. Some four million Americans are believed to be chronic carriers of the virus, and about 20 percent of these will go on to develop more serious liver disease, including cirrhosis and cancer.
The virus was only identified in 1989, and theres still much about it that is unknown. Receptors are an important part of the story of how viruses cause infection, Lai says. But we dont know what receptor hepatitis C uses to get into the cell.
Whats more, no one knows how to grow hepatitis C in the lab. That means that any research on how the virus replicates in cells is incredibly difficult.
However, Lai and his research group have managed to study the function of some of the viral genes. They have discovered that one of the hepatitis C viral proteins binds to a few key players in the human immune system, members of the tumor necrosis factor receptor family.
Lai suspects that this may help explain how the virus is able to escape the im-mune systems attack and so can develop into a chronic infection in many patients. It may also explain how the virus damages the liver and causes hepatitis.
After all these years, studying viruses shifty ways continues to leave Lai with a sense of amazement. Part of this comes from their ability to shuffle genes as deftly as some genetic engineers can.
Viruses can pick up pieces of cellular genes or incorporate their genes into the cells genome, he says. That means that evolution occurs all the time in viruses. Its a very dynamic process thats why I always feel that the viruses are alive.