Tackling Noroviruses to Aid Public Health and National Defense
In 18 years of working with noroviruses, Xi Jiang, PhD, has been instrumental in reaching major milestones on the way to controlling and preventing the most common cause of viral gastroenteritis. While still a postdoctoral student at Baylor College of Medicine in Houston, Texas, Dr. Jiang cloned the first norovirus. Now, as director of the norovirus program and professor in the Division of Infectious Diseases at Cincinnati Children's, he is working to develop vaccines or antivirals to stop noroviruses before they can inflict sickness.
'Cruise Ship' Misnomer
Dr. Xi Jiang (right) and fellow researcher Dr. Tibor Farkas review results of a test on noroviruses.
Sometimes called the "Cruise Ship Virus" due to highly publicized cases of boatloads of vomiting vacationers, noroviruses actually take a greater toll on military ships and other close-contact settings, such as schools and nursing homes. Symptoms include nausea, vomiting, diarrhea and abdominal pain. "The symptoms are not severe," Dr. Jiang explains, "but the illness is very widespread."
Noroviruses are extremely contagious and can spread quickly from person to person and through contact with contaminated surfaces, food or water. "We don't need to panic, however," Dr. Jiang advises. "The spread of noroviruses often can be prevented with good health habits, especially washing hands before eating."
"In an aircraft carrier or battleship, crew members are always at risk of an outbreak of norovirus," Dr. Jiang says. "It is a big issue in the military and why we have funding from the Department of Defense to try to develop a strategy to prevent the disease." Since 9/11, noroviruses have been listed as a priority pathogen in the federal biodefense research program.
Origins in Ohio
The first major outbreak of noroviral gastroenteritis occurred among 300 elementary school students and teachers, in Norwalk, Ohio. Although the outbreak occurred in 1969, it wasn't until 1972 that the virus was identified and named the Norwalk Virus. As similar viruses were subsequently discovered in many places, they were called Norwalk-like viruses, but are now known as noroviruses.
"These viruses are part of a very big family, with many different genetic and antigenic types," Dr. Jiang says. "Noroviruses must have coexisted with humans for thousands of years and developed unique strategies, such as varying their genetic makeup and structure, making it difficult for people to develop immunity."
Is a Vaccine Possible?
Noroviruses recognize different histo-blood group antigens (HBGAs), complex carbohydrates present on the surfaces of mucosal epithelium, as receptors. "The human HBGA system is highly polymorphic, and it is interesting that the viruses also are highly diverse in recognizing human HBGAs," Dr. Jiang notes. "A total of eight receptor binding patterns of noroviruses have been described so far. Defining the target HBGAs and the binding specificity of each norovirus strain could lead to the development of antiviral compounds."
New studies are uncovering "decoy" receptors in human milk that protect breastfed infants from norovirus infection and are increasing understanding of virus-receptor interaction. Understanding these structures could result in the design of compounds to block the viruses to their receptors.
The recent discovery of the subviral P-particles of norovirus is another exciting finding. "This type of particle can be potentially used for both antivirals and vaccines against noroviruses," Dr. Jiang says. "The concept of one reagent for two purposes (antiviral and vaccine) is novel," he noted in the research grant application. "If successful, it would greatly increase our ability for the intervention and prevention of norovirus gastroenteritis in either bioterrorism attacks or general disease control and prevention."
Dr. Jiang is a professor in the Division of Infectious Diseases. Recent studies on noroviruses by Dr. Jiang and colleagues have appeared in Trends in Microbiology (13[6]:285-293, June 2005), The Journal of Virology (79[22]:14,017- 14,030, 2005) and The Journal of Infectious Diseases (190:1850-1859, Nov 2004). His current study is supported by grants from the National Institutes of Health and the Department of Defense.
