In the afterglow of successful fecal transplants, researchers are now sniffing around vaginal fluids for the next possible bodily product to improve health—and they’re roused by the possibilities.

Vaginal fluid transplants could “revolutionize the way we view and treat conditions affecting the female reproductive tract,” researchers at Johns Hopkins wrote in a recent study on vaginal microbiota transplants (VMTs). If they work as researchers hypothesize, they could rub out many common problems at once. And based on what we know of vaginas, they could be far less messy than transplants involving poop.

Microbial muck

The basic idea behind VMTs is identical to that of poop transplants, aka fecal microbiota transplants (FMTs), which have been around for centuries. Generally, FMTs aim to use microbe-laden bodily products—in this case excrement—to introduce or restore rich, complex microbial communities into the innards of ailing recipients.

In healthy human intestines, thriving microbial inhabitants are involved in everything from cycling hormones and influencing immune responses to protecting from pathogenic germs, not to mention helping extract nutrients from food. When these communities die off, get out of balance (a condition generally called dysbiosis), or become overrun by disease-causing germs, our health can wane. That’s where FMTs come in.

Some researchers say they can trace deuce-based remedies back centuries , to people slurping "yellow soup” to treat severe diarrhea in 4century China, and Bedouin groups tossing back camel patties to cure dysentery centuries later. The idea plopped into western medicine in the 1950s but was largely dismissed until recently. The brown tide began to turn as researchers learned more about our microbial residents, and the rise of antibiotic-resistant infections spurred them to explore new treatment options.

Modern FMT recipients now take in the goods by piping them into their bowels, gulping them in capsules, or injecting them in enemas. And researchers are looking into using FMTs to treat a range of conditions including obesity, food allergies, inflammatory bowel disease, depression and multiple sclerosis.

But despite the fact that the medicine has come a long way from serving poopy soup, researchers are still straining to squeeze out all of FMTs potential. So far, the only condition for which there’s firm evidence that FMTs are effective is recalcitrant Clostridium difficile infections, which cause severe diarrhea—echoing the centuries-old uses of FMTs.

Against the life-threatening C. diff infections, FMTs have proven highly effective, clearing the infection in 80% to 90% of patients after one round. As such, FMTs are seen by many as a clear—albeit limited—success story, and they’ve garnered considerable attention from researchers and patients alike who hope they’ll be just as potent at treating other conditions.

Still, even with the focus on FMTs and microbiome research, our gut communities have remained enigmatic, proving extremely complex and variable. Researchers still don’t understand them enough to cure other conditions. We have yet to flush out what features, mixes, ratios, or microbial groups or species may be key to particular health outcomes. In other words, it’s unclear what makes for solid donor poop—let alone how to regulate and administer said poop.

On the flip side

Vaginal microbiota transplants, on the other hand, may not face such onerous hurdles. Based on what researchers have gathered so far, the microbial communities of a healthy vagina are relatively simple compared with that of the gut, and they play key roles in health.

As the Johns Hopkins researchers note in their recent study, “Although there has been increasing awareness of the broad spectrum of ‘normal,’ it is generally considered that the ‘optimal’ vaginal microbiota communities are dominated by one of only a handful of species of Lactobacillus” bacteria.

But if those communities get frisky, growing more diverse and ditching a dominant Lactobacillus, women can develop a common medical condition called bacterial vaginosis. This is linked to a range of problems including increased risk of urinary tract infections, greater susceptibility to getting and spreading sexually transmitted infections, issues with infertility, and preterm birth. Bacterial vaginosis is estimated to affect around 30% of US women aged 14 to 49, according to the Centers for Disease Control and Prevention. Other imbalances in vaginal microbes have been linked to recurrent yeast infections, some reproductive tract cancers, and the harboring of group B Streptococcus (bacteria that can cause severe infections in newborns).

A standard treatment for bacterial vaginosis is antibiotics, but the condition can relapse in as much as 70% of cases within 3 months. The hope of VMTs is that they could restore a healthy, simple vaginal microbiome and wipe out all of those risks in one clean stroke.

In anticipation of such a clinical peak, the researchers at Johns Hopkins set up a pilot study of 20 women to try to figure out how to screen potential donors of cervicovaginal secretions, which could then be used for transplants.

The pilot screening process first involved a questionnaire about sexual behavior, vaginal product use, infections, and vaginal symptoms. Researchers next did tests for active infections and past exposures, probed the genetics of vaginal microbes, and looked at the physicochemical properties of vaginal fluids. They determined, among other things, that a good cut-off point for the pH of transplantable vaginal fluids is ≤4.2.

Only seven of the 20 women in the study (35%) were considered potentially eligible to be VMT donors in the end, and the researchers expect that percentage to be even lower in larger screenings.

While few women may end up qualifying to be donors, the researchers note that “the idea of a ‘super-donor’ with no identified past or current infections and with favorable Lactobacillus-dominated microbiota is one that should be explored and is of potential high impact to the project and the field.”

Once safe and desirable donors are identified, researchers face the real test of whether VMTs actually work. Based on epidemiological data of women who have sex with women, vaginal microbiota transfers are possible. But they still need to be proven and refined in clinical setting.

There are some key unknowns, for instance, whether aspects of the vaginal environment—such as mucus or lactic acid—might be critical for transplant success, or whether minority bacterial community members are key to overall health.

For now, the researchers “anticipate that the framework described [in the study] will help accelerate clinical studies of VMT.” In the meantime, “the development of the FMT field is an obvious source of inspiration for initiating study of other forms of microbiota transplantation, such as VMT.”

Frontiers in Cellular and Infection Microbiology, 2019. DOI: 10.3389/fcimb.2019.00306 (About DOIs).