Noroviruses are perhaps best known for ruining cruise ship vacations, but they also wreak havoc in other closed settings such as day care centers, dormitories and nursing homes. Worldwide, they are the most common cause of acute gastroenteritis, an illness that can lead to abdominal cramps, diarrhea and vomiting in all age groups. While there is no vaccine to prevent norovirus infection, early detection of an outbreak could help curb its spread through a community and enable medical workers to provide the appropriate treatment to those affected.
Researchers have worked for years to develop diagnostic tools for norovirus. These efforts reached an important milestone recently when the FDA approved the first screening test for the preliminary identification of norovirus. The test, called the Ridascreen Norovirus 3rd Generation EIA, is based in part on technology developed by NIAID scientists.
Human noroviruses cannot yet be grown in the laboratory, making it difficult for researchers to study their interaction with immune cells. Scientists in NIAID’s Laboratory of Infectious Diseases used genetic engineering to sidestep this challenge. They modified the DNA of another family of viruses, called baculoviruses, to carry the gene that encodes the protein shell, or capsid, of several norovirus strains. When grown in insect cells, the modified baculoviruses express virus-like particles (VLPs) that mimic the norovirus capsid. The capsid contains antigens that stimulate the immune system to produce antibodies that attack the virus.
Diagnostics manufacturer R-Biopharm licensed the recombinant baculoviruses from NIAID in 2004 and used the virus-derived VLPs to create monoclonal antibodies against norovirus. In R-Biopharm’s Ridascreen test, these antibodies serve to capture norovirus antigen from a stool sample. If the antigen is present, the antibodies bind to it so it can be detected in later steps of the test.
The FDA approved the Ridascreen Norovirus test for use in situations where a number of people have simultaneously contracted gastroenteritis and there is a clear potential avenue for virus transmission such as a shared location or food. The ability of the test to detect a norovirus outbreak becomes greater as the number of patient samples increases, so while the test is not recommended for diagnosing norovirus infection in sporadic cases of gastroenteritis, it is useful for the preliminary screening of multiple stool samples.
According to R-Biopharm, the test yields results in less than 2 hours, enabling faster implementation of outbreak control procedures. In March, the CDC updated its norovirus outbreak management and disease prevention guidelines to reflect Ridascreen’s approval.
NIAID’s contribution to the Ridascreen test is its latest accomplishment in a decades-long commitment to better understand noroviruses and develop new strategies to prevent, detect and treat infections caused by them. In 1972, NIAID scientist Dr. Albert Z. Kapikian and his colleagues first identified norovirus, initially called Norwalk virus, as a cause of acute epidemic gastroenteritis. Kapikian and his team made this seminal observation while examining virus-containing stool samples originating from a 1968 outbreak of gastroenteritis in Norwalk, Ohio. Institute scientists continue to pursue the development of vaccines and antiviral compounds against norovirus, including research on possible experimental systems to facilitate study of the immune response to norovirus infection in cells and in animals.