Campylobacter is a major cause of bacterial diarrhea worldwide — estimated to be the cause of 4-15 percent of cases. It’s a problem in both developed and developing countries and is associated with unpasteurized dairy products, contaminated water, poultry and produce.
In the U.S., the Centers for Disease Control and Prevention estimates that campylobacteriosis affects more than 1.3 million people every year.
Although Campylobacter infections are generally mild, complications can include reactive arthritis neurological disorders such as Guillain-Barré syndrome, a disorder in which the body’s immune system attacks part of the peripheral nervous system.
The latest potential vaccine for the bacteria was developed through the collaboration of the Naval Medical Research Center (NMRC) and Professor Mario Monteiro of the University of Guelph in Ontario, Canada.
Campylobacter is one of a select group of pathogens that produces a polysaccharide capsule — or sugar coating on the surface of the bug — which is kind of a protective layer, explained Dr. Patricia Guerry, head of the NMRC Campylobacter research group.
So the vaccine is a conjugate containing polysaccharides from C. jejuni joined to a protein to enhance immunogenicity.
“The idea is it can generate antibodies against the polysaccharide capsule,” Guerry says. This, in turn, causes lysis, or a disintegration of the bacteria.
If you were infected by Campylobacter and got sick, you’d generate antibodies and you would likely be protected against a second infection. The vaccine gives an individual the opportunity to make these antibodies without the infection.
There are a number of polysaccharides conjugate vaccines on the market today. Prevnar for pneumococcal pneumonia is one of the best-known examples.
They have been very successful for pneumococcal infections, Guerry notes, but “Campylobacter is unusual for an enteric pathogen in that it also expresses the polysaccharide capsule.”
There are currently no licensed vaccines for Campylobacter, but NMRC has tested two others that it ultimately did not develop past Phase I.
This latest vaccine is currently in Phase I testing where it’s being tested for safety and immunogenicity. The previous ones “passed in terms of safety, but they weren’t particularly immunogenic,” Guerry explains.
If the current vaccine passes into Phase IIB, “we would immunize other volunteers with what appears to be the best dose and then challenge them with a strain of Campylobacter to see if it protects against diarrhea,” she says.
In a 2009 study, the vaccine provided 100-percent protection against diarrhea in monkeys when challenged with C. jejuni 81-176.
It’s important to note that the model for the testing in humans involves a strain of the bacteria developed by NMRC that is unable to induce Guillain-Barré syndrome (caused by a certain structure on the cell wall of some strains).
“We have been through FDA approval of this and it’s been through 100 people already in other studies, so we are unique in having the ability to come back and do a human challenge with this strain,” Guerry says.
If the vaccine were ultimately licensed, Guerry says it would be primarily for travelers.
“The military is interested in it because troops are a certain sub-class of travelers, but it could also be marketed to civilian travelers going to endemic areas,” she says.© Food Safety News