The investigators constructed a live recombinant bacterial vaccine, expressing the H. pylori antigen, adhesin Hp0410, in the food-grade bacterium, Lactobacillus acidophilus. They then used it to orally vaccinate the mice.
The vaccine elicited specific anti-Hp0410 IgG antibodies in serum, and showed “a significant increase” in the level of protection against gastric Helicobacter infection, according to the report. When assayed, following challenge with H. pylori, immunized mice had significantly lower bacterial loads than non-immunized mice.
H. pylori is a class 1 human carcinogen, according to the World Health Organization. It causes gastritis, peptic ulcers, stomach cancer, and mucosa-associated lymphoid tissue lymphoma. Antibiotic therapy is complex, unsuccessful in some patients (particularly in developing countries) and relapse is common. A vaccine against H. pylori could circumvent these difficulties.
L. acidophilus, a bacterium which is common in yogurt cultures, has distinct advantages as an oral vaccine antigen delivery vehicle. It is safe and nontoxic. It resists the stomach’s acidity and tolerates bile, all of which aids in enabling it to survive in the gastrointestinal (GI) tract for more than 72 hours. Additionally, it adheres to, and elicits an immune response from the GI tract mucosa.
The current first-line treatment option for H. pylori infection includes two antibiotics and a proton pump inhibitor, but is ineffective in roughly 20 percent of patients.
“The high cost of treatment, noncompliance, and antibiotic resistance are the most important reasons,” says first author Fan Hongying.
Roughly 15-30 percent of patients relapse quickly, she says, noting that after treatment, H. pylori may be resupplied to the stomach from a reservoir in the mouth. A vaccine would circumvent these problems.
“Our results collectively indicate that adhesin Hp0410 is a promising candidate vaccine antigen and recombinant Lactobacillus acidophilus expressing Hp0410 is likely to constitute an effective, low-cost live bacterial vaccine against H. pylori,” says Hongying.
A copy of the manuscript can be found online at http://bit.ly/asmtip1213d. The final version of the article is scheduled for the February 2014 issue of Clinical and Vaccine Immunology.
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Clinical and Vaccine Immunology is a publication of the American Society for Microbiology (ASM). The ASM is the largest single life science society, composed of over 39,000 scientists and health professionals. Its mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.”