News Article
From Times of India - Original
HEADLINE:
Step Forward in Search for Malaria
Vaccine
BYLINE: Times of India News Service
DATELINE: 12 December 1999
By DOUGLAS BIRCH
WASHINGTON: An experimental malaria vaccine
achieved limited success in a field trial in West Africa,
researchers say, fueling cautious hopes that people can one
day be inoculated against one of the planet's most prolific
killers.
The vaccine briefly reduced malaria cases by almost
two-thirds in a group of volunteers in Gambia last year,
researchers said. Scientists disclosed the results last week
at a meeting of the American Society of Tropical Medicine
and Hygiene in Washington.
"I think it's a great step forward," said Dr. Philip K. Russell
of the Center for Immunization Research at the Johns
Hopkins School of Public Health. "We've got, for the first
time, protection against malaria in the wild, even if it's only
short-term."
Scientists recruited 306 men in six rural villaged in Gambia,
a nation about 200 miles long and about 12 miles wide,
lying inside Senegal. After two months, almost two-thirds
were protected, but that rate fell to just 16 percent after 15
weeks. It was too short a time for a practical vaccine.
But researchers were heartened about the results. The
vaccine, developed by the Walter Reed Army Institute of
Research and SmithKline Beecham, protected about half of
volunteers in a series of small-scale trials in the institute's
Washington labs over the past three years. But the African
trial tested the vaccine against different strains of the malaria
parasite in an area of intense transmission.
The vaccine consists of a piece of the malaria parasite
linked to a piece of the hepatitis B virus, and mixed with a
cocktail of compounds called adjuvants, meant to boost the
response of the immune system. Like all vaccines, the
Walter Reed-SmithKline product is designed to teach the
immune system to respond quickly and aggressively to a
particular microbe.
Researchers cautioned that the vaccine isn't ready for
clinical use. "The Gambia trial confirmed the good and bad
things about the vaccine," says Dr. W. Ripley Ballou, until
recently the leader of the Walter Reed effort. "Yes, it
confers immunity on about half the people it's given to. But
it lasts only a couple of months. Nobody believes that we
have a vaccine that is ready for licensing or that will meet
sub-Saharan Africa's needs.''
Still, Ballou and others hope that the product, called
RTS,S, can become the foundation of a practical vaccine.
Dr. Stephen L. Hoffman of the Naval Medical Research
Institute says he plans in January to use RTS,S to "boost"
a vaccine developed in his labs. Hoffman's vaccine works
by inserting malaria genes into the DNA of human muscle
cells, causing those cells to make chemical structures
normally made only by the parasite. Released into the
bloodstream, those chemical structures stimulate the
immune system, preparing it for combat with the parasite
itself.
Malaria is common throughout the tropics. It ranks with
tuberculosis and AIDS as one of the biggest killers among
infectious diseases. The World Health Organization
estimates that each year the mosquito-borne parasite
causes a half-billion cases of clinical illness and 1 million to
2 million deaths.
Scientists have sought a malaria vaccine since 1880, when a
French doctor in Algiers first identified the malaria microbe
in the blood of a soldier. Malaria is a parasite, an animal
with complex tactics for evading the human immune system.
While there are many vaccines against bacterial and viral
illnesses, no one has ever made a workable vaccine against
a parasite.
(LATWP Svc)
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