Vaginal Dreams
After 10 years, microbicide research demands attention.
By Anna Forbes

Anna Forbes is a public health activist, teacher, and writer who's been working in the AIDS/HIV field since 1985 and specializes in women's health issues, including microbicide development.

A gawky-looking mobile made of lab supplies hangs in the sleek, modern window of Sharon Hillier's cluttered office at Magee Women's Hospital in Pittsburgh. Suspended from its plastic petri-dish center are various tools of her trade: a paper chem strip for measuring pH levels, a microscope slide, colorful paper-cutout rods, and squiggles in the shapes of various vaginal flora. Dangling alone in the center is the crown jewel: a lactobacillus capsule- the "vaginal vitamin" for which Hillier, after a decade of hard research, is slowly becoming famous.

The mobile was a gift from Hillier's research staff, people that she misses spending weeks with now that she's hitting the big time, her days filled with teaching, grant writing, traveling, and public speaking. To stay connected, she leaves the posh environs of the hospital every day and takes her bag lunch over to the lab next door. There, in a cramped lunchroom, she and her team review the day's events, solve problems, and have a few laughs.

With a Ph.D. in bacteriology and public health, Hillier, 44 (pictured above left), is considered a pioneer in the field of women's health and sexual transmission, a walking dictionary on nasty diseases down there who knows more about your private parts than you could imagine. "Even seen one of these? That's what we call a vagina," she jokes during lectures, drawing nervous laughter from male colleagues as she throws up a hand-drawn slide of the female genital tract and launches into a Sex Ed 101 tour of that famed orifice. Her upbringing on a Washington State farm comes through in her warm, forthright manner. "Now I know it can be a little scary," she teases. Her female colleagues smile wryly; they know it's all too true.

Hillier's mission is to spotlight a long-neglected goal of AIDS research: the development of a vaginal microbicide, a product designed to protect women against sexually transmitted diseases, especially HIV, that would provide a much-needed alternative to male condoms. While her soft sandy brown bob, business suit, and pumps are standard issue, she's not. Underneath her casual manner there's a steely mind at work-and the radical spirit of a public health activist. After she's lured her audience in, Hillier goes for the kill, pointing out how little we've progressed in a decade of effort to protect millions of women at risk for HIV and those already infected. "I'd like to declare this the Year of the Vagina," she says, throwing up a challenge to the scientific community and prevention advocates. By putting microbicide research high on the HIV agenda and dedicating money to the field, she's convinced we could make a major dent on this epidemic.

For that to happen, though, much more advocacy is needed. Since the need is clearly there, why the gap in our knowledge? One reason, say researchers, is a lack of public awareness. Even among HIV activists, the subject of microbicides tends to provoke a blank or puzzled reaction. Try asking a politician. (Microbi-what? Oh yeah, something for women. Right, we need that. But can't they use condoms?)

Public support for such research is miniscule compared with HIV treatment or vaccine research. Federal funding for microbicides stands at a paltry $25 million per year-only 1 percent of this year's federal NIH AIDS budget and seven times less that the admittedly underfunded government vaccine budget. Nevertheless, a recent international survey shows that women are very eager, even desperate, to use an effective microbicide, since many find it difficult to negotiate condom usage with partners (see "Pipeline," page 24).

In her own work, Hillier likes to apply harm-reduction principles to biological as well as behavioral realities. She's looking for a way to "tip the balance" of the body's defenses with a microbicide, to somehow enhance a woman's natural resistance to STDs, including HIV. Her focus is on what she calls "the delicate ecosystem of the vagina"-a veritable hothouse of microorganisms. When stress, infections, or illnesses occur, they can upset this natural ecological balance, giving rise to bacterial or other infections, which irritate the mucosal lining of the genital tract and greatly increase a woman's risk for STDs. Many studies show STDs are a significant cofactor in HIV transmission-for both sexes.

Years ago, Hillier began exploring the connection between the presence of a thriving lactobacillus population in the vagina and its ability to resist sexually transmitted infections. In her view, boosting the growth of lactobacilli (LB) may be an important key to slowing HIV infection in women.

Her test weapon-the "vaginal vitamin"-is a small suppository capsule that melts at body temperature and contains hydrogen peroxide-producing lactobacilli, one of the "friendly flora" found normally in the vagina. Based on her early data, Hillier says her LB capsule has the potential to balance the pH of the vagina and prevent STDs from developing, thereby decreasing the risk of HIV infection. Even better, it would be cheap to produce.

Unfortunately, her vaginal pill been a hard sell. Most virologists, she says, "don't buy into what we're trying to do" because they see attempts to decrease susceptibility to disease as too simplistic. Overall, she adds, the public health profession has never taken an ecological view of infectious diseases despite the fact that "infection happens in human environments and not a test tube."

Today, that may be changing. Over the past year, progress in the field of AIDS has renewed interest in immunolgy and in its shadow, the subjects of vaginal and mucosal immunity. While Hillier's lactobacillus pill is designed to prevent an infection from occurring, others are trying to stop them from taking hold by inducing a genital immune response to STDs and HIV. This approach, building on studies by Harvard University researcher Bruce Walker and others, suggests that HIV-specific immune responses are critical for controlling HIV; it's an approach based on data from long-term "non-progressors" with HIV and acutely infected individuals. Such individuals typically have high, sustained levels of a subset of white blood cells (T-cells) called cytotoxic T-lymphocytes or CTLs (also called killer cells). HIV-specific CTLs are primed to destroy HIV-infected cells in the body.

Recent studies have shown that a local immune T-cell response to HIV can also develop in separate tissue compartments. What we generally refer to as "immunity" covers systemic immunity-the circulation of bloodborne pathogens (disease-causing organisms), antibodies, vaccines, etc. But the body also maintains distinct local mucosal immune responses that protect us from invading organisms in the lungs, nasal passages, eyes, gut (including rectum), mouth, urethra, and vagina.

The question now being asked is whether we might induce protective CTL immune responses to HIV or STDs in the genital and rectal tracts. The few studies we have are tantalizing. In 1995, Deborah Anderson, a leading researcher at Harvard's Fearing Research Labs, found that eight of the 222 HIV-negative women enrolled in one study had tested HIV positive at least once on cervico-vaginal lavage (a test of the amount of virus in vaginal mucosa) but negative by standard ELISA and Western Blot antibody tests. These women were having regular, unprotected, vaginal intercourse with their HIV-positive male partners but abstaining from intercourse for 48 hours prior to the lavages (a factor verified with SEMA rape-detection tests). All eight remained HIV negative throughout the study (one to five years).

It is evident, Anderson concluded, that "a percentage of women that engage in unprotected intercourse with HIV-positive partners develop localized mucosal immune response against HIV-1." Other studies by Mazzoli et al. in 1997 and others confirm the existence of this phenomenon.

At the recent World AIDS Con-ference in Geneva, several researchers also noted the association between a strong immune response, including high CTL levels in the bloodstream, and the absence of HIV infection among women, including sex workers who had been repeatedly exposed to HIV. A new study by Grant Yeaman and colleagues at Dartmouth Medical School found strong localized CTL responses in the vaginas of women who remained HIV negative despite repeated sexual exposure to HIV by their positive male partners.

Looking ahead, microbicide advocates hope that current vaccine trials looking at CTL may be expanded to also look at intravaginal vaccines and genital immunity.

Women have evolved with a threefold vaginal defense system in place. The first is a physical barrier provided by the vaginal epithelium, or cell wall, which is made of a dense layer 16 to 30 cells thick that lines most of the vagina from the entrance to the fornix (the back of the vagina surrounding the cervix). Although capable of stretching enough for childbirth, the vaginal epithelium in its relaxed state is like an uninflated balloon. While generally resistant to infection, its surface is nonetheless punctuated by star-shaped, dendritic cells. These cells are thought by some researchers to be among the first targets for HIV infection.

At the top of the vagina, at the cervix, lies a "transformation zone" where the tough squamous epithelium gives way to a fragile, columnar layer that is only one cell thick. In a healthy woman of childbearing age, very little if any of this columnar layer is exposed. It is protected inside the closed cervical os-the opening to the uterus that, except during childbirth, is closed like a clenched fist. The tougher vaginal epithelium covers the outside of the cervix to protect it from abrasion during intercourse.

Since HIV can attach easily to columnar cells, women are at higher risk of infection when this easily infected lining becomes exposed on the outside of the cervix. This condition, known as cervical ectopy, most commonly occurs postpartum, postmenopausal, in adolescence, or during pregnancy; and it may be associated with the use of hormonal contraceptives.

The second arm of the vagina's self-defense system consists of the antimicrobial substances called natural microbicides and antibodies secreted by specific vaginal cells (see "Pipeline," page 24). The third arm of the vagina's defense system is its normally low, or acidic, pH. A measure of the amount of acid or alkaline in an environment, pH level (like oxygen level) is a critical factor in any living organism's survival. Too much or too little, depending on the organism's needs, can kill. Think of the impact of acid rain on grass and foliage. A healthy vagina has a pH level of approximately 4. Semen, on the other hand, has a neutral pH of around 7.

HIV appears to survive best at a neutral pH, according to recent studies by Ken Mayer of the Memorial Hospital of Rhode Island. In test-tube studies, both cell-free HIV and HIV-infected cells are rapidly inactivated at pH levels below 4.5 and 5.5 respectively, as are several harmful bacteria including those causing gonorrhea and bacterial vaginosis. When a man ejaculates during unprotected vaginal intercourse, his semen raises the pH of the vagina and keeps it elevated at around 5.5 to 7.0 for at least two hours, according to John Hopkins researcher Kevin Whaley. (This information is gleaned from a 1960s Masters and Johnson sex study that showed the vaginal pH moves from an average of pH 4 to pH 7 within nine seconds of ejaculation and stays at the elevated pH for two to eight hours.) It is believed that this facilitates the survival of both sperm and any HIV that may be present in the semen, says Whaley.

Not surprisingly, the antimicrobial impact of low vaginal pH was one of the first aspects of vaginal immunity to be explored in microbicide research. Hillier's "vaginal vitamin" enables women to boost the number of hydrogen peroxide-producing lactobacilli growing in their vaginas, thus facilitating their ability to maintain a healthy, low vaginal pH. Her newest unpublished data backs this up. In a clinical study involving 90 female teenagers, her team found that the hydrogen peroxide-producing test strain of lactobacilli could be successfully grown in women with suboptimal lactobacillus (LB) populations up to 88 percent of the time simply by inserting LB capsules twice daily for three days.

The beauty of this product, Hillier says, is that as with vitamin C, "the body takes what it needs and the rest washes away." So far, no significant negative side effects have been associated with the introduction of additional LB to the vaginal environment.

In an earlier 1992 study, Hillier showed also showed that by lowering vaginal pH, LB helps prevent genital colonization by the anaerobic bacteria that she refers to as the "bad boys of bacterial vaginosis." These bacteria produce an enzyme called sialidase (or neuraminidase) that, in turn, may enhance vaginal susceptibility to HIV infection. At least four other studies to date have now documented the strong association between bacterial vaginosis and HIV infection.

Another product inspired by the protective effect of a low vaginal pH is BufferGel (see box).

An antiretroviral is also being studied as a microbicide. In recent monkey studies, PMPA (Gilead), a nucleotide analog drug, prevented HIV transmission in all treated animals. Phase I human trials will soon begin.

Looking ahead, cost is a deciding factor since the most widespread, urgent need for microbicides is among impoverished women at the highest risk for HIV, many living in the developing world. Up to now, the high production costs of many potential microbicides has limited their investigation.

According to the late, great Jonathan Mann, once head of the world's AIDS program, we are now investing nearly five time as much globally in AIDS care and treatment than we are in prevention. With 5,700 women contracting HIV every day and hundreds of thousands more becoming infected with HIV-facilitating STDs, simple common sense demands reevaluation of these priorities. Even vaccine researchers concede it will take at least a decade before we'll have an effective HIV vaccine. Meanwhile Hillier and other advocates are sure a microbicide could be developed in far less time.

With a moderate increase of the fiscal HIV pie and a slight reorganizing of priorities, they argue, we could profoundly change the survival odds for millions of people. Lately there are signs that public health officials are waking up to that promise. When questioned, two leaders in the AIDS fight-Peter Piot, head of the Global Programme on AIDS, and Neil Nathanson, new head of the U.S. Office of AIDS Research-respectively put microbicide research high on the agenda.

That's good news to Sharon Hillier and her colleagues, but she's not holding her breath. She wants action. Sitting amid the calm blue walls and muted hum of her office at Magee, she's getting worked up again. "The issue of HIV prevention is not a gay issue or a women's issue - it's a human issue" she declares passionately. "We can make good, safe microbicides publicly available if we choose to. We have everything we need to make it happen-except the will and the money."