HIV/AIDS and Microbicides

What's the Problem?

The human immunodeficiency virus (HIV) is a virus that suppresses the immune system of an infected person. It targets and destroys particular white blood cells (CD4 cells, a type of T cell) that the immune system needs in order to fight disease. The virus is transmitted from person to person through contact with HIV-infected blood or other bodily fluids such as semen.

At the end of 2007, more than 32 million people were living with HIV and approximately 2 million people died of HIV-related causes. Sub-Saharan Africa remains the region most heavily affected by HIV/AIDS, accounting for 67% of all people living with HIV and for 75% of all AIDS deaths in 2007 (1). More than 14 million children have lost one or both parents to HIV/AIDS (2).

HIV transmission can be prevented through a variety of methods—such as abstinence, monogamy with an uninfected partner, and the use of latex or polyurethane condoms—but these methods are not always available, affordable, or practical. This has led researchers down a promising new path to develop microbicides that block or kill HIV as soon as it enters an uninfected person's body.

Who's at Risk?

Anyone engaging in unprotected sex (anal, vaginal, or oral) can become infected with HIV, since the HIV virus spreads through blood and bodily fluids. Individuals with multiple sex partners, including commercial sex workers, are at increased risk. Additionally, groups with high levels of mobility, such as migrant workers and refugees, also have increased susceptibility to HIV transmission (3).

Women are especially vulnerable to HIV, making up half of all people living with HIV worldwide. In sub-Saharan Africa, women are even harder hit, accounting for nearly 60% of the region's HIV infections (1). Women's vulnerability to HIV is due, in part, to cultural norms related to sexual activity between men and women, which make women less empowered to negotiate safe sex (such as sex with condoms, which block the HIV virus). For example, some men may refuse to wear condoms or practice monogamy with their uninfected female partner.

The increased vulnerability of women to HIV infection makes plain the need for new interventions such as microbicides to block the transmission of HIV. These types of interventions give women the ability to protect themselves against HIV and other sexually transmitted infections (STIs) without the need to negotiate a different method with their partner.

Microbicides and HIV/AIDS Prevention

Microbicides are currently in the research and development phase. But what are they made of, exactly? This is a complicated question to answer, because so many different microbicides are in development. But there are some basic components being tested for use as HIV-fighting microbicides: certain types of bacteria, chemical compounds, synthetic molecules, antiretroviral drugs, and/or natural agents.

Some microbicides act as a physical barrier between HIV and other pathogens in the cells of the rectum or vagina, while others eliminate or immobilize pathogens. Microbicides may also prevent HIV infection from progressing after the virus has entered the body. The ideal microbicide will combine all three mechanisms to prevent HIV infections.

Most microbicide products are being developed as gels, creams, suppositories, or films that are applied before sexual intercourse or as a sponge or in a vaginal ring that releases the active ingredient over time (4). This innovative form of protection is being considered one of the most important approaches in reproductive health since oral contraception (i.e. "the pill").

Microbicides could be an especially important line of defense for women. For millions of women around the world, other forms of HIV prevention are not an option, as they are impractical, too expensive, sporadically available (or not available at all), or too difficult to negotiate with partners. Unfortunately, many women lack the social or economic power to insist on condom use or fidelity, or to walk away from partnerships that put them at risk. Microbicides can put the power to protect themselves directly in women's hands, as microbicides do not require the cooperation of their partners in protecting their bodies from HIV and other STIs (4).

Although presently scientists are testing various versions of microbicides, there is no safe and effective microbicide available yet to the public. Trials of some first generation, non-antriretroviral products, failed to show any protection against HIV. Recently, one such microbicide, Pro-2000®, was shown in a non-definitive study to have modest efficacy. A much larger study of Pro-2000 will be completed within the year. Second-generation products containing HIV-specific antiretroviral product such as Dapirivine, Tenofovir, and CONRAD's UC781 are in efficacy trials throughout Africa and India (5).

The costs of researching and developing microbicides are high and funding from governments and philanthropic donors is important to the development of microbicides. While no microbicides have been approved for release to the public, dozens of agents that interrupt HIV infection have been identified and are currently under study and testing (6).

The Bottom Line

Microbicides are still in development and are not yet available to the public, but once produced they will be an important tool in the fight against the spread of HIV/AIDS, especially for women around the world.

Case Example

As microbicides are still in development, there are no readily available case examples.