PUBLIC HEALTH REPORTER
August 15, 2006
TORONTO — With the search for an AIDS vaccine proving elusive, scientists and activists are increasingly pinning their hopes for slowing the epidemic on microbicides, easy-to-apply gels that would act as an “invisible condom” to prevent infection.
“The prospect of a microbicide is thrilling,” said Stephen Lewis, United Nations special envoy for HIV-AIDS in Africa. “Regardless of its effectiveness, it will inevitably save millions of lives.”
In fact, a recent study conducted by the London School of Hygiene and Tropical Medicine estimated that a microbicide that reduced the risk of infection by 40 per cent — and that was used by 30 per cent of women at risk in low-income countries — would avert more than two million HIV infections a year and save $1-billion (U.S.) annually in health-care costs.
Gita Ramjee, director of the HIV-AIDS program at the South African Medical Council, said it is impossible to overstate how desperately women — who make up three-quarters of new infections in sub-Saharan Africa — need some form of protection.
Participant Nomvula Mathiso is shown how to use microbicide as part of a University of Witwatersrand scientific trial in Johannesburg last year. John Morstad/The Globe and Mail (John Morstad/The Globe and Mail)
“They do not know if they will be infected tonight, tomorrow night or the next night. The threat is always there,” she said.
Worldwide, an estimated 38.6 million people are infected with HIV-AIDS, half of them women. The epidemic is spreading fastest among young women aged 16 to 24.
Condoms are an effective means of blocking transmission, but condom use is low. In much of the world, women do not have the power — physical, legal or social — to negotiate safer sex. They must succumb to sex when, where and how their partner chooses, even if that partner is HIV-positive.
Microbicides can be packaged in a gel, foam, vaginal ring, sponge, suppository or douche form. Scientists are hoping to develop products that, in addition to blocking the transmission of HIV-AIDS, will prevent other sexually transmitted diseases such as herpes, gonorrhea and chlamydia and, in some cases, also have contraceptive properties. Unlike other forms of protection such as condoms and cervical caps, they also hope to produce products that are long-lasting, able to thwart the virus for days, or even months.
“Women need multiple drugs with multiple delivery options,” said Zeda Rosenberg, chief executive officer of the International Partnership for Microbicides, a group based in Silver Spring, Md.
She said that variety in microbicides is essential because, like birth control, “women have different needs at different stages in their lives.”
Currently, there are dozens of microbicides in development, but five are at a fairly advanced stage, and being tested in humans. One of these, called C31G (brand name Ushercell), is Canadian, and being produced by Polydex Pharmaceuticals Ltd. Results of the first studies will be published late next year, and the product could be on the market by 2009.
Microbicides work in various ways. Some, such as Carraguard, a seaweed-based gel, create a physical barrier that keeps HIV from reaching cells where they will latch on and infect a person; others, like Ushercell, which is derived from cotton, disable the virus by stripping off its outer covering. Another class of microbicides boosts the vagina's natural defence mechanisms by raising pH levels and creating an acidic environment hostile to viruses.
The key is finding out whether the products, which work in the lab, will be effective for people living everyday lives.
There are concerns that the advent of microbicides will be seen as a substitute for safer sex practices such as condom use, and that the products will be shunned because of a belief they prevent pregnancy. (Scientists stress that both contraceptive and non-contraceptive microbicides will be developed.) Alex Coutinho, executive director of the AIDS Support Organization of Uganda (TASO), said the science of blocking is the easy part. The hard part is creating products that women will actually use and that are affordable and readily available.
“It's not just about microbicides, it's how you deliver microbicides that really matters,” he said. “Women need something they can fit and forget.”
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