Salmonella Vaccine Uses "Molecular Telephones" to Talk to the Immune System

Salmonella infections are a massive problem—Over 95 million people are affected by this foodborne illness every year. But we have antibiotics to deal with the problem, right? Wrong.

Outbreaks of drug-resistant Salmonella have been steadily occurring across the U.S. There was the outbreak of antibiotic-resistant Salmonella caused by contaminated cucumbers in 2015, another transmitted via papayas in 2017, and more concerningly, a multi-drug resistant strain in pork products that resulted in a number of severe cases in 2015. The WHO estimates 2 million people lose their lives as a result of Salmonella infections annually.

New research on the development of a Salmonella vaccine may be the light at the end of the tunnel. Researchers at the University of Florida have published a study that leverages cells’ communication systems to initiate a protective immune response against the bacteria.

"Cells communicate with each other through particles called extracellular vesicles or EVs. Think of these like molecular telephones that let cells talk to each other. We wanted to know if some of those messages included information related to immune response," said Winnie Hui, first author of the study. The relationship between human EVs and protection against pathogenic bacteria in the gut has, until now, not been extensively explored.

The researchers extracted EVs (or exosomes) from white blood cells infected with the bacteria, which contain fragments of the bacteria known to activate the immune system. They then administered these exosomes in mice to test their hypothesis, with promising results.

"There are two types of immune responses generated when our bodies encounter a pathogen. The first one is called innate immunity, which is an immediate response to an infection, but it is also less specific,” explained Hui. “The other response is called adaptive immunity, and this protective response is specifically tailored to a given pathogen, but it also takes longer to develop.” 

“Exosomes generated by infected white blood cells stimulated both of these responses in animals," Hui concluded.

The study paves the way for exosome-based vaccines to protect against not only Salmonella but potentially other intestinal infections as well. However, more testing in humans needs to be done before such therapies are readily available in the clinic.

Sources: PLOS Pathogens, EurekAlert via the University of Florida.