Sunday, June 13, 2010

Yellow Fever

“Malaria is one of the most pressing health crises of developing countries: in communities stricken by infection, attendance at work and school drops, and poverty deepens…There is no vaccine for malaria, which sickens almost a quarter of a billion people each year and kills a child every 30 seconds.” Scientists race to change those statistics, exploring various avenues for human vaccination and malaria eradication. Recently, “researchers at The Rockefeller University have genetically transformed the yellow fever vaccine to prime the immune system to fend off the mosquito borne parasites that cause the disease. The researchers found that the modified vaccine, along with a booster, provided mice with immunity to the deadly disease.”

“It has been known since the 1960s that” the sporozoite, one form of the malaria parasite “can wake up the immune system and help to protect against future infection.” Unfortunately, the only known “way to gather sporozoites…is to pluck them one-by-one from the salivary glands of irradiated, malaria-ridden mosquitoes. To provide immunity, the attenuated parasites must then be injected in high doses” or “delivered by the bites of hundreds of mosquitoes”, which is “a labor intensive approach not feasible for large-scale use.”

In an effort to find a better way to achieve the “benefits of sporozoite immunization”, scientists, led by Charles Rice, thought “that fighting infection with infection might be the key. They began experimenting with the attenuated yellow fever strain used in the yellow fever vaccine, known as YF17D, which has been used to successfully vaccinate more than 400 million people since 1937. Previous work in the Rice laboratory and by others had shown that this vaccine strain could be modified to include short sequences from other pathogens, including malaria.”

“Immunization of mice with the YF17D-CSP vaccine led to a measurable jump in immune activity against the malaria protein, but the single shot was not enough to protect the animals from infection with the mouse form of the malaria parasite.” The scientists added a booster shot, and discovered that “vaccination with YF17D-CSP plus the sporozoites protected 100 percent of the animals against infection.”

Stoyanov et al. Immunogenicity and protective efficacy of a recombinant yellow fever vaccine against the murine malarial parasite Plasmodium yoelii. Vaccine, 2010; 28 (29): 4644 DOI: 10.1016/j.vaccine.2010.04.071

Rockefeller University (2010, June 11). Yellow fever vaccine modified to fight malaria. ScienceDaily. Retrieved June 13, 2010, from¬ /releases/2010/06/100611222839.htm

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