A team of researchers at UC Davis led by Stephen McSorley, in conjunction with collaborators at UC Irvine, identified antigens on salmonella bacteria. This new discovery could lead to salmonella prevention.
Salmonella is a bacterial infection that is carried through food. According to the Centers for Disease Control and Prevention, 400,000 cases of salmonella are reported in the United States alone.
Most salmonella infections are mild. Diarrhea, fever and cramps develop within three days of initial infection. These symptoms typically persist for around a week and abate without need for medical aid. However, there do exist more severe cases of salmonella in less fortunate individuals in which the infection spreads to the blood, which is often fatal.
In this regard, McSorley’s lab has been trying to identify targets for immune attack in salmonella in hopes of being able to vaccinate.
“There has been a lot of progress over the years in identification in other infectious diseases, but for some reason salmonella research seemed to be left behind,” McSorley said, “Which is terrible since many young children die of salmonella infections every year in Africa and Asia.”
Currently, there exist no vaccinations for the salmonella bacterial infection. Patients whose condition necessitates medical action are treated with antiobiotics. Those who are young, elderly, have compromised immune systems, and especially those without adequate medical facilities are less likely to benefit from this treatment.
Logical targets for vaccines are called antigens, which are proteins that are exposed on the bacteria. These foreign proteins are noticed by a person’s immune system, which targets the bacteria for destruction. Once these antigens have been targeted, the immune system will always react to that particular protein.
In addition to antigens, bacteria and other cells produce many more proteins that are not exposed as antigens. Immune systems cannot identify proteins that are not exposed. Therefore, the trouble in identifying immune system targets lies in distinguishing between antigens and other proteins.
McSorley’s lab synthetically produced 2,700 proteins for testing that the salmonella produces naturally. These proteins were then isolated and injected into the blood of mice that had been previously infected with salmonella. These mice were then tested for a response.
Since the mice’s immune systems had previously been exposed to salmonella, any protein that was exposed in the bacteria would trigger a response. When a protein caused no response, it was shown not to be an antigen. If a protein did cause a response, that means it was an antigen.
These proteins can potentially be used in vaccines to prevent infections. Exposing someone to the protein without any actual bacteria will prepare an immunity without the danger of infection.
According to McSorley, “the vaccine won’t contain any live organisms and should be very safe for young children.”
By these methods, the lab has identified 117 proteins that were antigens. Only a handful have been tested due to labor and monetary constraints. By identifying these antigens, the hope is that researchers in McSorley’s lab and other institutions can continue testing for good vaccines.
McSorley collaborated closely with Renee Tsolis of the UC Davis Medical School due to similar interests and pertinent information.
“I worked together with Dr. McSorley on this project, because we had done some work trying to define the salmonella antigens recognized by mice,” Tsolis said. “We realized that we had a common interest and decided to share our data and work together.”
ALEX STANTON can be reached at firstname.lastname@example.org.