New technology with a Department of Agriculture stamp of approval could offer speedy help to hog producers hit by emerging disease outbreaks. And beef producers may soon see the benefits as well.
USDA’s Center for Veterinary Biologics has approved a new platform for customized vaccine production that allows veterinarians to prescribe vaccines to target specific viruses circulating on hog farms. The platform’s developer, Medgene Labs, based in Brookings, South Dakota, spent 10 years perfecting the technology.
“This approach will change the way veterinarians and producers think about vaccines as a tool for disease management, especially for emerging and constantly-changing viruses,” said Medgene CEO Mark Luecke.
According to Luecke, many of the nation’s largest producers have already used the company’s prescription vaccines.
“We focus on what other vaccine manufacturers cannot do. We are currently working with vets and animal owners on some of the most difficult challenges they are facing in the field, and one is rotavirus C,” Luecke said. “Even before the platform was licensed, we put out more than 500,000 doses so animal owners and vets could make clinical observations to prove the vaccine is clearing viral infections.”
Following an outbreak of porcine epidemic diarrhea virus in 2013, CVB developed guidelines in 2015 for the development of veterinary vaccine platforms. Such platforms, the center concluded, are defined as production platforms that use “a single ‘backbone’ vector, or expression system, and a standard process for inserting a gene(s) of interest into the backbone to generate different recombinant Seeds or Sequences (constructs).”
Once a disease vector is identified, the selected gene or genes then code for a protein. This protein mimics the infectious agent to stimulate the immune system so it can respond when exposed to the circulating virus. These proteins, or constructs, are then used to produce customized non-replicating and nonviable (killed) vaccines that can target a wide variety of the most economically significant diseases facing the industry.
Prescription vaccines could also prove crucial for pervasive, difficult-to-treat viruses, such as rotavirus C, which causes diarrhea in piglets and for which no conventional vaccine exists.
When veterinarians see signs of morbidity or mortality in a swine herd, the first thing they do is send a sample to a university diagnostic lab. The lab then runs tests to isolate the virus causing the disease and then sequences a gene of interest. When a conventional vaccine is to be made, the diagnostic lab sends the actual virus to the manufacturer so it can be inactivated and developed into a vaccine.
All told, the conventional vaccine process, including the time it takes to get regulatory approval for the final product, can take as long as five years. Prescription vaccine platforms can dramatically reduce that timeline.
“We never see the virus in our lab,” Luecke said. “The diagnostic lab just sends us the sequence in an email. Our lab then uses the sequence to program insect cells to make the specific protein needed, and the protein becomes the vaccine.”
Once a veterinarian writes a prescription for a vaccine developed using this new technology, Medgene’s process takes between 2-3 days if the company already has the correct protein, or construct, and up to 10-12 weeks for a novel virus or for a virus for which no construct exists.
Medgene’s construct bank currently holds more than 250 insect proteins in three viral families—rotavirus, coronavirus, and influenza. For some influenzas, the company’s constructs cover 97% of the swine influenza viruses currently circulating, Luecke noted.
Medgene has also developed a prescription vaccine platform for viral diseases of cattle, which is expected to receive CVB approval as early as this month, and continues to work on vaccine platforms for livestock bacterial diseases.
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Clayton Johnson, a veterinarian at Carthage Veterinary Service, in Carthage, Ill., has been using Medgene’s prescription vaccines for rotavirus C for about a year. He started using them under field evaluation to help Medgene determine the vaccine’s efficacy. The clinic, which works with 20% of the U.S. pig industry, has prescribed rotavirus C vaccines for six herds representing about 30,000 producing sows.
“We don’t have conventional vaccines available for rotavirus C, and there aren’t a lot of ready medical solutions,” Johnson said. “It’s a common disease found on most pig farms, and good management doesn’t always result in no disease. Some pigs will get sick even with good management.”
On one of the farms Johnson works with, about 70-80% of litters had scouring, or diarrhea, despite what he described as ideal management by the operation. After vaccinating sows ready to farrow with prescription vaccines from Medgene, scouring dropped to 20-30% of litters; sows pass their protective antibodies to piglets through colostrum, he added.
“In the last decade, we have seen more disease problems develop than solutions,” Johnson said. “The platform technology is of high interest to us in the veterinary community.”
In addition to getting vaccines to market faster than vaccines made with the conventional process, prescription platform vaccines offer protection that more closely matches the actual virus being targeted. Because of the time required to get to market, conventional vaccines need to rely on cross protection, which means a genetic difference typically exists between the original virus and current viral strain, which has likely mutated.
While vets like Johnson may be optimistic about the benefits of the platform, some in the industry are still formulating their opinion. Representatives on the veterinary staff for the National Pork Board, the National Pork Producers Council and National Cattlemen’s Beef Association did not offer comment for this story.
Dr. Paul Sundberg, D.V.M., executive director of the Swine Health Information Center, said the market will decide whether Medgene’s vaccine platform and others are successful. “Getting vaccines to market sooner is good,” Sundberg said. “We want these products available, and the market will sort out whether they are effective and cost-effective for producers.”
Medgene is not the only company with an approved swine prescription vaccine platform. Merck introduced its Sequivity vaccine platform in 2018 that uses RNA-based technology, similar to that used by Moderna and Pfizer in developing their COVID-19 vaccines for humans. However, vaccine platforms have not been approved for human use.
The two processes used by today’s veterinary platforms are similar in that both collect the pathogen and sequence genes of interest. However, instead of creating the protective protein, Merck’s platform inserts the gene into messenger RNA particles. These in turn become the vaccine, which when injected into the animal spur the hog to make its own protective proteins.
At this point, hog vaccines produced through RNA technology can only protect against one pathogen at a time, while the newer technology can combine proteins to protect against more than one pathogen in a single injection, according to Luecke.
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