A new poultry vaccine in development at the University
of Arizona offers a unique approach in controlling Campylobacter jejuni
infection in chickens.
Trials have shown that the vaccine significantly reduced the pathogen's
ability to colonise young chickens' intestines, where the infection begins. The
goal is to halt the contamination before it spreads and survives on raw chicken
sold in stores.
"Chickens don't actually cause the disease, nor does it make them ill. It's
the organism they carry that makes people sick," said Lynn Joens, a professor in
The University of Arizona Dept of Veterinary Science and Microbiology.
Funded by the USDA, Joens and UA graduate students started analysing
Campylobacter's infection process about 4 years ago, looking for a way to
interrupt it. The laboratory team discovered that the pathogen first attached
itself to the surface of the chick's intestines and then began to multiply.
Attacking the "sticking" mechanism seemed to be the key.
When the UA researchers sequenced the intestinal surface protein they
identified the gene responsible for producing Campylobacter's adherence protein.
Then they built a trial vaccine around it using Salmonella bacteria as a vector.
The adherence gene was inserted into Salmonella bacteria, which is nonpathogenic
for poultry. The resulting live vaccine - containing Salmonella programmed to
make the Campylobacter adhering protein - was fed to young chickens to protect
â€œOnce the Salmonella in the vaccine produced the Campylobacter protein, the
chicks made antibodies against it in their intestines,â€ Joens says. "In our
first study of 15 birds we got a very significant reduction - 98% - in
Campylobacter infection, compared with a control group. We're now repeating the
trial on a larger scale."
Joens' preliminary figures show that 270 million Campylobacter organisms
were present in non-vaccinated birds, compared with 67,000 organisms in the
"You need at least 500 organisms to produce disease in humans," he
explained. "The chlorine in the packinghouse chillers usually reduces numbers of
bacteria by 1,000 to 100,000 organisms, so the chickens should be free of
Campylobacter after processing."
The UA group was the first to discover the adherence protein, which is only
produced when Campylobacter jejuni colonizes certain surfaces, like chicken
intestine and skin. They have a patent pending in both the US and the EU for the
gene that produces it.
"If everything goes right we could have a commercial vaccine in 3-5 years,"
Source: University of Arizona