Citrus juices inactivate HIV; researcher defends investigation as possible microbicide

In an in vitro study by Roger Short of the University of Melbourne presented at a poster at the Fifteenth International AIDS Conference In Bangkok, a solution containing 20 per cent lemon or lime juice was found to inactivate 90 per cent of HIV reverse transcriptase activity within two minutes. A phase I safety study of using citrus juices as topical microbicides is now planned.

Obviously, finding that something as cheap and universally available as lemon juice could be an HIV preventative is an exciting idea, and Short mooted the idea of using it as a microbicide

At the Bangkok Confernece he explained to aidsmap.com that the idea had come to him during a conversation with Senator Mechai Viravaidya, Community Co-Chair of the Bangkok Conference and architect of Thailand’s ‘100% Condom’ campaign.

“I had been aware that women had used it as a folk contraceptive for centuries. And since then I have learned that sex workers in Nigeria and possibly other high-prevalence countries are using lemon and lime douches regularly as a post-coital contraceptive and anti-infective precaution. This means that we can design an ethical placebo-controlled study, whereas previously the possibility that the approach could cause damage would have made this very difficult.”

Prevention researchers had urged considerable caution about Short’s ideas, given the previous experience when the spermicide nonoxynol-9, which inactivates HIV in vitro, was found to actually facilitate HIV transmission in vivo because it damages the epithelial cells lining the vagina (and rectum).

However nonoxynol-9 is a surfactant, not an acid. Short said that the environment of the vagina is normally acid and that citric acid is a major component of semen. “The vagina is no stranger to an acidic environment,” he said. One of the candidates in the efficacy studies of microbicides due to start in the second half of this year, BufferGel, uses the same principle.

Short’s poster says that daily intravaginal administration of neat lime juice to macaque monkeys for one month caused no discernible epithelial damage.

Short then investigated the degree to which different dilutions of lime and lemon juice inactivated HIV replication and the viability of HIV-infected cells in a test-tube cell culture.

Short says he was optimistic “because if you can get the pH in ejaculate down to 4” (the lower the pH of a fluid, the higher its acidity) you can efficiently immobilize 100% of sperm cells within 30 seconds.” The pH of neat lemon or lime juice is about 2.4.

Short exposed peripheral blood mononuclear cells (PBMCs) to different dilutions of lemon or lime juice. He them cultured HIV within the cells for two weeks and measured HIV replication by measuring reverse transcriptase activity.

A 5% lemon juice solution in culture halved HIV replication within an hour, while a 10% solution cut it by two thirds. Both of these were non-toxic to the PBMCs in culture. A 20% solution, while it reduced HIV replication by 90% within two minutes, also killed off 25% of the PBMCs, indicating possible toxicity limits to the approach.

Short has already conducted further in vitro research on the ejaculate of HIV positive men, and intends to move forward into phase I safety trials.