BANGKOK, July 12 (AFP) - Prayers for a vaginal gel to kill the AIDS virus, thus protecting millions of women from infected sex partners, may be answered by ... the humble lemon.
That is the novel suggestion made by Australian researchers, who have followed up ancient traditions in parts of rural Southeast Asia that lemon or lime juice, used intravaginally, can be a sperm-killing contraceptive.
In research to be presented on Tuesday at the International AIDS Conference here, a team led by Roger Short of the University of Melbourne says a solution of lemon juice -- when tested on a lab dish, not on humans -- was a mighty slayer of the human immunodeficiency virus (HIV).
"Provided that clinical trials confirm that intravaginal lemon juice is acceptable, safe and effective, it could prove to be Nature's own microbicide," according to a resume of their research.
Microbicides have been one of the most frustrating avenues of scientific efforts to find an alternative to the unloved condom to protect men and women during sexual intercourse.
A cream or gel like this would be a godsend, especially in Africa, where the majority of the 25 million with HIV are women who became infected through their husbands or boyfriends.
Women are especially vulnerable because they are expected to be submissive in sex, and cannot persuade or force their partner to wear a condom.
So a gel that they could use discreetly, and which would be cheap and cope with heat, rather than require refrigeration, would be ideal.
In all of AIDS' 23-year history, only one microbicide, a detergent molecule called nonoxynol-9, has been tested, and it proved to be a disaster.
It was trialled along with a lookalike product among more than 400 sex workers in Western Africa and South Africa and Thailand. Those who used the nonoxynol-9 three times a day or more were almost as twice as likely to get infected with HIV as those who used the placebo.
The apparent reason: the tough chemicals damaged the lining of the vagina, creating tiny lesions that helped HIV enter the bloodstream.
Six other large clinical trials of microbicides are either underway or about to start, and the quest has been given a push by a new initiative, the International Partnership for Microbicides.
Short's team tested various solutions of lemon juice on ejaculates of sperm from men with HIV.
A two-percent lemon juice solution had no effect in an hour-long exposure. When this was beefed up to 10 percent, replication of the virus was halved, and was non-toxic.
A 10-percent solution reduced replication by two-thirds and was also non-toxic.
And a 20-percent solution destroyed 90 percent of the virus within just two minutes, but with signs of toxicity.
A long road of careful testing lies ahead before lemons or limes can be used this way.
The research is being viewed skeptically among experts within the microbicide sector.
"The concept is to buffer the pH [acidity] of the vagina and it's being actively looked at in a concept called Buffer Gel," said a specialist at the International AIDS Conference.
"Every concept should be tested first for safety."
But Short says the results should not be ignored.
"We've been looking for the microbicidal Cadillac, when all along we've been overlooking the humble push bike," he told the British science journal Nature last week.
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