Scientists at the Pirbright Institute in the UK found a new way to diagnose foot-and-mouth disease (FMD) in pigs and other animals. The researchers suggested that their new test is more cost effective and relies less on the use of small animals than previous methods of FMD detection.
FMD is a highly contagious viral disease that infects cloven-hoofed mammals such as pigs, cattle, sheep, goats and various wildlife species. The disease occurs in parts of Africa, the Middle East, Asia and parts of South America and causes serious economic losses annually. While FMD doesn’t currently threaten US pig herds, some lawmakers advocate for stockpiling FMD vaccine in the US.
Current FMD diagnosis
There are seven types (serotypes) of FMD virus (FMDV) that have high mutation rates which constantly generate new FMDV variants. This makes rapid diagnosis essential for vaccinating against the correct type of FMDV and ensuring control policies are put in place quickly.
Previously, diagnostic tests known as ELISA’s have required small animals such as rabbits and guinea pigs to produce proteins called antibodies. These antibodies bind to FMDV enabling the disease to be detected in samples. Each strain of FMDV requires highly specific antibodies which means new antibodies are regularly required to keep up with emerging new strains.
New FMD technique
Instead of using animal antibodies, previous research has shown that a protein called integrin αvβ6 can be used to detect the presence of FMDV. This works because integrin αvβ6 is a receptor that universally binds to field strain FMD viruses in order to gain entry into cells. The group therefore used a truncated bovine integrin αvβ6 (a shorter, modified cow version of the protein) in their ELISA tests that all FMDV types would bind to.
The researchers have been able to create large amounts of bovine integrin αvβ6 in the lab using a rapid technique called transient cell transfection. This could make diagnosis of FMD strains cheaper and easier, as only one integrin would be needed to identify all strains of FMDV, compared to the many antibodies that were needed previously.
Another major benefit is that animals are not needed to produce bovine integrin αvβ6. This is a huge step towards supporting the 3Rs agenda (Refine, Replace and Reduce) in science regarding the use of lab animals.
Further experiments are needed to optimize and validate the test for routine FMDV diagnosis, but it is hoped that bovine integrin αvβ6 could eventually be used in the FMDV diagnostic kits that the Institute distributes all over the world.
Alternative to live virus
The researchers also set out to find an alternative to using inactivated FMD virus as a positive control for the integrin diagnostic tests, which is used to confirm the test is working. Previously this required the production of live FMD virus, which is costly since this infectious virus must be produced in a high containment laboratory.
Pirbright Institute scientists successfully demonstrated that modified empty shells of FMD virus (capsids) without any genetic material, can be used instead of the inactivated live virus, as these capsids have the ability to bind to integrin and can be produced without the need for high containment. This could lower the cost for positive control production and make the process faster and more efficient.
This study was published in the journal PLOS One.
FMD in the US
There has not been a case of the disease in the U.S. since 1929, but industry and government leaders want to be prepared if it returns.
The United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) will be seeking a supply of FMD vaccines to protect U.S. swine, cattle, sheep and goat herds.
APHIS would like to have a minimum of 25 million doses for each of the 10 high-risk strains available. Over the coming years, APHIS is looking to incrementally increase the amount of stored FMD vaccine that is readily or quickly available for the agency to use should it be necessary to vaccinate.