In a major development that could lead to ways to prevent colds and other illnesses, scientists announced Wednesday that they have deciphered the atomic structure of a common cold virus, creating a detailed blueprint of the cause of one of humanity's most irksome ailments.
The findings will make it "much more possible, absolutely," to find ways to thwart attacks by cold-causing rhinoviruses and related viruses, said lead researcher Michael G. Rossmann, professor of biological sciences at Purdue University.
"The results are very important," he told a news conference sponsored by the National Science Foundation.
Moreover, the findings and techniques used in studying the cold virus could be applied to members of the same viral family, such as hepatitis A, polio and foot-and-mouth disease, as well as to other viruses, such as those responsible for AIDS and leukemia, Rossmann said.
He cautioned, however, that the more than 100 known strains of cold viruses probably will make it difficult to develop a single vaccine to protect against the illness. But, he added, the new data will allow scientists to determine what part of the virus attaches to the human "host" cells to cause infection, thus enabling researchers to devise strategies to disrupt its function.
"I am doubtful that a vaccine for the common cold is possible, but there are other ways that could be considered," Rossmann said. "You might want to do something with the receptor, which is constant."
The coat of each virus contains sites that can find and attach themselves to cell "receptors" in the host, in this case in the upper respiratory system, he said. Thus, protection from the common cold could be achieved, he said, if a method could be found to somehow change the receptor so "the virus can no longer stick to it."
Although the site of host receptors is not precisely known yet, he said, "it's like a lock and key--if you've got the structure of a lock, you can figure out the structure of the key."
Rossmann said this is the first time that the design of any animal virus has been reduced to its atomic arrangement.
"We had no idea whatsoever what the three-dimensional structure was of any animal virus until now--none whatsoever," he said.
Eckard Wimmer, chairman of the microbiology department of the State University of New York at Stony Brook's School of Medicine who is considered a leading expert on these viruses, called Rossmann's work "of fundamental importance."
"Now that the structure of rhinoviruses has been solved, one can make conclusions concerning all the other human pathogens as well," Wimmer, who was not a member of the Purdue team, said in an interview. "It is a further step toward protecting man against infections caused by this family of viruses."
Rossmann, working with a group headed by Dr. Roland Rueckert of the University of Wisconsin and computer scientists at Cornell University, used a super-computer to bring the viral structure to a resolution of three angstroms--so precise that they were able to create a comprehensive map in which various proteins in the virus could be easily identified. An angstrom is one hundred millionth of a centimeter, or about .000000004 of an inch.
Rossmann described the virus, known as rhinovirus-14, as an "icosahedron," a 20-sided, sphere-like structure made up of 60 copies of four proteins surrounding a core of ribonucleic acid (RNA), the genetic material. Three of the proteins make up the outer shell, and the fourth is situated between the shell and the RNA, he said.
Rossmann said that the researchers, funded by the National Science Foundation and the National Institutes of Health, found four "antigenic" sites on the viral surface--that is, places where the host's antibodies can attach to fight the infection.
In addition, he said, the researchers made one "unexpected finding": that the cold virus structure is closely related to that of a plant virus previously investigated by the Purdue team. This, he said, provides "the strongest evidence to date that viruses from both the plant and animal kingdoms had a common evolutionary precursor."