Single dose salmonella vaccine to fight infant pneumonia

January 13th, 2009 - 1:50 pm ICT by IANS  

Washington, Jan 13 (IANS) Researchers are close to what may be a winning strategy to fight infant bacterial pneumonia that claims two million lives worldwide every year. Two new vaccine strains developed by them draw on the properties of an unlikely vaccine carrier - one associated with causing sickness like Salmonella.

Salmonella typhimurium, a rod-shaped, motile pathogen is one of over 2,000 strains or serotypes comprising the same constellation. They are responsible for causing serious, sometimes fatal diseases, to which children under two years of age are particularly vulnerable.

Hence, Salmonella’s choice as the principal component in a new vaccine for babies has been something of a hard sell. “People said you gotta be kidding,” said Roy Curtiss, investigator of vaccines and infectious diseases at Arizona State University’s Biodesign Institute, who is conducting the research.

Curtiss recalled that 20 years ago, Salmonella outbreaks were a grave concern in nurseries and hospitals, sometimes leading to the deaths of over half the children in such facilities.

Salmonella strains are violently infectious, ransacking the body’s defences, as anyone who has suffered a bout of food poisoning can attest.

Curtiss hopes to recruit Salmonella’s appetite for infection and use it to speed delivery of a suite of key antigens-surface proteins of Streptococcus pneumoniae, causative agent of bacterial pneumonia.

In the body, such antigens stimulate an immune response, but the additional pathogenic ingredients necessary to cause the disease are absent, said an Arizona state release.

The strategy of using a live bug like Salmonella to stimulate a protective immune response has been around for a while. But such microbes have typically had to be weakened or attenuated before safe use, disabling some of their virulence in order to prevent a full-blown occurrence of disease in the vaccine recipient.

Besides Salmonella-based vaccines offer an inexpensive alternative which may be administered orally in a single dose - a significant advantage in the developing world.

These findings were published recently in the Proceedings of the National Academy of Science.

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