LINDELL BEACH, B.C. — After years of research, scientists at the United States Department of Agriculture have produced a molecular vaccine for one strain of foot and mouth disease that does not use the live virus and can be used to differentiate between an infected and an inoculated animal.
Marvin Grubman, supervisory research chemist at the USDA Agricultural Research Service’s Plum Island facility in New York, called it a major step forward.
“This new vaccine does not contain the infectious foot and mouth disease virus. It only contains a portion of the viral genome, nucleic acid, therefore it cannot cause disease. It does not have to be produced in a high containment facility so it can be made on the U.S. mainland.”
Grubman said the existing vaccine is made from the infected cells of the virus which has to be inactivated in a high containment facility because technicians are working with an actual, live virus.
The viral structure of foot and mouth disease includes genetic material surrounded by a coat of proteins called a capsid.
The new vaccine produces only the virus coat particles, forming empty capsids. Without the entire genome of the virus, it lacks the full infectious nucleic acids. But when it is injected into an animal, the empty capsids still trigger the protective immune system.
“More recently companies are partially purifying the virus to get rid of viral nonstructural proteins,” he said.
“That was the problem before because animals vaccinated for the disease would have antibodies against the nonstructural proteins and it would look very much like an infection, rather than a vaccination. With this new vaccine, the virus is partially purified to remove the nonstructural proteins.
“The vaccine we produce doesn’t contain the coating regions for a number of nonstructural proteins. If you develop a diagnostic test for a protein that’s not present like with this new vaccine, it’s unequivocal that animals vaccinated with it won’t have antibodies against it whereas animals that are infected will. It’s clear.”
Grubman originally developed this new generation of vaccine but it took him and a team of scientists advancing on a number of new scientific levels over seven years.
A conditional licence has been issued for the A24 virus strain of FMD and, according to Grubman, can be used in cattle now in the event of an outbreak. Vaccines for other strains are still being tested.
The breakthrough marks a major leap forward in effective control of a complex disease that still plagues Asia, Africa and the Middle East. It is now largely contained in South America. Grubman said there was a small outbreak in Venezuela earlier this year.
There are seven strains, or serotypes, of FMD and over 60 subtypes. It’s not unlike the ‘flu virus and the vaccine being administered has to match the specific strain of the virus that is circulating in the field.
“This is a new generation of vaccine,” said Grubman, noting that it should be cheap enough for countries that don’t have the disease but want to have an emergency stockpile.
One problems with the current vaccine is the potential for human error in which the virus escapes and causes an outbreak, as was the case in the U.K. in 2007.
“That can’t happen with the new vaccine,” said Grubman.
The cost of the vaccine is not clear yet clear. The research team is working on enhancing the potency while looking at ways to reduce the cost.