WSU to develop advanced vaccine for costly tick-borne pathogen

Washington State University researchers have been awarded an $800,000 grant to develop a safer and more effective vaccine for Anaplasma marginale, a tick-borne pathogen responsible for billions of dollars of losses globally for the cattle industry.

Led by WSU College of Veterinary Medicine professor Kelly Brayton, the researchers aim to address the limitations of existing vaccines by creating a solution that will not only be universally effective against all strains of the prolific bacteria, but will also not require cold storage, making it more accessible for remote and under-resourced regions.

"Anaplasma marginale poses a serious threat to livestock worldwide, leading to substantial economic losses and impacting cattle health," Brayton said. "Our goal is to provide a practical and effective solution that will help protect cattle from this debilitating pathogen and reduce its economic impact."

Anaplasma marginale, transmitted through tick bites, can cause severe anemia, illness, abortions, and even death in cattle. In the United States alone, the disease costs cattle producers an estimated $300 million annually. Current vaccines are not approved for use in the U.S. and have notable drawbacks, including that they are not effective against all strains of the bacteria and the need to be maintained at low temperatures, which is impractical in many areas.

The team plans to use a unique approach to develop a DNA vaccine, a type of vaccine that uses a small piece of DNA containing genes that code for specific proteins - or antigens - from pathogens like viruses or bacteria. When the DNA is introduced into the body, the cells take up the DNA and use it to produce the antigen, triggering an immune response.

Unlike traditional vaccines that rely on a single antigen, this new vaccine will introduce a "cocktail" of 10 antigens using a gene gun, a device that shoots tiny particles coated with genetic material into target cells at high speed.

"Often, vaccine testing involves one antigen at a time. If it doesn't work, researchers move on to the next. But combining multiple antigens might stimulate enough immunity to benefit the animal," Brayton said. "Using multiple immunogens also makes it less likely for the organism to adapt and evade the immune response."

The researchers will initially test and refine the vaccine on controlled herds before conducting field trials in the U.S. and South Africa against multiple strains of Anaplasma marginale. A key part of their strategy involves working with tick challenges, a method that mimics real-world conditions more closely than traditional injection challenges.

"Many studies just inject the pathogen because they don't have the ability to do tick challenges, but we do thanks to our specialized facilities and our partnership with the USDA," Brayton said, referring to the long-standing collaboration between WSU and the USDA focusing on agricultural research and innovation. "When ticks feed, they secrete substances into the host that dampen the initial immune reaction. We believe this is why protection from injection challenges doesn't always translate to real-world effectiveness."

Brayton said the new methods that will be used in the project could hold promise not only for combating Anaplasma marginale but also for future vaccine development.

"One of the biggest issues with vaccine development has been the piecemeal approach -testing one antigen at a time," she said. "We believe that our approach of using a comprehensive array of antigens will be really important and could pave the way to new and more effective vaccines."

Brayton is collaborating with WSU co-investigators Jason Park, an assistant professor in the Department of Veterinary Microbiology and Pathology, and Massaro Ueti, a research veterinary medical officer in WSU's Animal Disease Research Unite and the USDA Agricultural Research Service, on the four-year project. Additionally, Nicola Collins at the University of Pretoria in South Africa will contribute to the research efforts.