Scientists report advance in tackling respiratory virus reproduction

Scientists have determined the structure of a key protein from a paramyxovirus, a leading cause of respiratory disease in children throughout the world. In the study, published in Nature Structural Biology (vol. 7, no. 11), researchers describe the three-dimensional structure of a protein used by paramyxoviruses to latch onto, penetrate and exit the cells of the respiratory tract. Paramyxoviruses cause several respiratory diseases in humans and animals. One of these viruses, parainfluenza, infects almost all children before they reach the age of five, causing illnesses ranging from colds to pneumonia.

The study could reveal clues for effective new drugs, and highlights the benefits of structural biology in guiding drug design against communicable diseases.

"This report is the most exciting discovery in the field in quite some time," said Fran Rubin, program officer for respiratory diseases at the National Institute of Allergy and Infectious Diseases, which partially funded the study. "We have no vaccines or effective drugs to stop viruses like parainfluenza. This study opens new possibilities for drug development."

Study details

The study focuses on a protein called hemagglutinin-neuraminidase, which is found on the surface of many paramyxoviruses. The protein plays a key role in infection, helping the virus recognize and enter cells and spread to neighboring cells as the virus reproduces. Each of these properties depends on the unique shape of the protein and the chemical charges distributed across its surface.

The researchers in this study used X-rays to probe the molecular structure of HN from Newcastle disease virus, a paramyxovirus that causes respiratory illness in chickens. "My laboratory has tried for years to find an HN protein that would permit us to take a look at its molecular structure, but many would not form the crystals required to get an X-ray picture," said researcher Alan Portner. "Newcastle disease virus finally provided a protein that solved our problems." The scientists knew from genetic and biochemical analysis that this HN gene is very similar to the HN of other paramyxoviruses, making their results applicable to parainfluenza and related viruses.

Once they determined the HN structure, the researchers were surprised to learn that two different virus properties - attachment and release from the cells lining the respiratory tract - are controlled by the same region of HN. Because viruses must latch onto the cell before entering, this one region is critical for several virus functions. "What this means is we might be able to attack multiple facets of the virus through a single site," said researcher Garry Taylor. "If we can design a molecule that blocks this site, we might have a drug that prevents all three key steps in virus infection – attachment, cell entry and release."

Concluded Portner, "This study offers hope that we will one day be able to treat the infection before the damage is done, improving the health of many children and beating back a leading respiratory infectious disease." PR