There is no FDA-approved human vaccine for non-typhoidal salmonella, which kills hundreds of thousands of people and sickens an estimated 93.8 million people globally each year. Non-typhoidal salmonella is a type of salmonella that causes gastrointestinal disease and is spread through contaminated food and water.
However, scientists at the University of Florida are taking an innovative approach toward developing such a vaccine one day.
In a new study, researchers used small extracellular vesicles, or sEVs, to boost immunity against Salmonella in mice. This increased immunity helped the mice survive what could be a potentially fatal infection, the study reported.
“Mice already get more disease from the Salmonella strain than humans, so the fact that our treatment allowed the mice to survive is promising,” said Mariola Edelman, senior author of the study and assistant professor at UF/IFAS. Microbiology and Cell Science.
Extracellular vesicles are small packets of molecules produced by cells to communicate with other cells. Immune cells infected with bacteria or viruses produce viroviruses that alert other cells to the threat.
In this study, the researchers wanted to see if giving mice sEVs produced by cells that had recently fought off Salmonella would inoculate the mice against future Salmonella infection.
The scientists gave these induction analyzes to one group of mice, either orally or through a nasal spray, while another group of mice received a saline solution. Four weeks later, the researchers infected all of the mice with salmonella. Only those mice that received sEVs intranasally were able to produce what the scientists call memory immune responses against these bacteria, and these mice also survived.
The researchers also compared mice that received the sEV treatment with infected mice that had survived a weakened strain of Salmonella. This weakened strain is often used to compare the effectiveness of a potential Salmonella vaccine. The scientists found that both mice treated with sEV and mice infected with the weakened strain survived Salmonella infection.
“The weakened strain is not a valid human vaccine because it is still a live pathogen and can make you sick. However, with sEVs, we saw the same protective effects as the weakened strain but without the risk of disease,” said Lisa Emerson, first author of the study and doctoral student at UF. / IFAS Faculty of Agricultural and Life Sciences working in the Edelmann Laboratory.
The researchers also discovered that mice exposed to the sEVs produced antibodies against Salmonella. These antibodies allow the immune system to recognize and fight Salmonella in the future. However, the researchers do not yet know how long this “memory response” lasts after the four-week period used in the experiment.
Subscribe to Outbreak News TV on YouTube
Moving forward, the researchers want to understand why helping mice build immunity to salmonella through the nose, rather than through the mouth. They will also explore how to ramp up production of sEVs, a necessary step in mass production of a vaccine.
Mass-produced virus sEVs could have benefits beyond salmonella prevention, Edelman said, as sEVs could be used to deliver a vaccine to protect against other infectious diseases.
“Particularly new about this approach is that we are using a tool that cells already use to communicate as a way to boost immunity against disease,” Edelman said.
