Brittany Barreto first got the idea to make a DNA-based dating platform nearly 10 years ago when she was in a college seminar on genetics. She joked that it would be called GeneHarmony.com.
Pheramor and startups, like DNA Romance and Instant Chemistry, both based in Canada, claim to match you to a romantic partner based on your genetics.
The idea stuck with her while she was getting her PhD in genetics at Baylor College of Medicine, and in March 2018, she launched Pheramor, a dating app that measures compatibility based on physical chemistry and what the company calls "social alignment."
"I wanted to use genetics and science to help people connect more. Our world is so hungry for connection," says Barreto, who serves as Pheramor's CEO.
With the direct-to-consumer genetic testing market booming, more and more companies are looking to capitalize on the promise of DNA-based services. Pheramor and startups, like DNA Romance and Instant Chemistry, both based in Canada, claim to match you to a romantic partner based on your genetics. It's an intriguing alternative to swiping left or right in hopes of finding someone you're not only physically attracted to but actually want to date. Experts say the science behind such apps isn't settled though.
For $40, Pheramor sends you a DNA kit to swab the inside of your cheek. After you mail in your sample, Pheramor analyzes your saliva for 11 different HLA genes, a fraction of the more than 200 genes that are thought to make up the human HLA complex. These genes make proteins that regulate the immune system by helping protect against invading pathogens.
It takes three to four weeks to get the results backs. In the meantime, users can still download the app and start using it before their DNA results are ready. The app asks users to link their social media accounts, which are fed into an algorithm that calculates a "social alignment." The algorithm takes into account the hashtags you use, your likes, check-ins, posts, and accounts you follow on Facebook, Twitter, and Instagram.
The DNA test results and social alignment algorithm are used to calculate a compatibility percentage between zero and 100. Barreto said she couldn't comment on how much of that score is influenced by the algorithm and how much comes from what the company calls genetic attraction. "DNA is not destiny," she says. "It's not like you're going to swab and I'll send you your soulmate."
Despite its name, Pheramor doesn't actually measure pheromones, chemicals released by animals that affect the behavior of others of the same species. That's because human pheromones have yet to be identified, though they've been discovered throughout the animal kingdom in moths, mice, rabbits, pigs, and many other insects and mammals. The HLA genes Pheramor analyzes instead are the human version of the major histocompatibility complex (MHC), a gene group found in many species.
The connection between HLA type and attraction goes back to the 1970s, when researchers found that inbred male mice preferred to mate with female mice with a different MHC rather than inbred female mice with similar immune system genes. The researchers concluded that this mating preference was linked to smell. The idea is that choosing a mate with different MHC genes gives animals an evolutionary advantage in terms of immune system defense.
The couples who had more dissimilar HLA types reported a more satisfied sex life and satisfied partnership, but it was a small effect.
In the 1990s, Swiss scientists wanted to see if body odor also had an effect on human attraction. In a famous experiment known as the "sweaty T-shirt study", they recruited 49 women to sniff sweaty, unwashed T-shirts from 44 men and put each in a box with a smelling hole and describe the odors of every shirt. The study found that women preferred the scents of T-shirts worn by men who were immunologically different from them compared to men whose HLA genes were similar to their own.
"The idea is, if you are very similar with your partner in HLA type then your offspring is similar in terms of HLA. This reduces your resistance against pathogens," says Illona Croy, a psychologist at the Technical University of Dresden who has studied HLA type in relation to sexual attraction in humans.
In a 2016 study Pheramor cites on its website, Croy and her colleagues tested the HLA types of 250 couples—all of them university students—and asked them how satisfied they were with their partnerships, with their sex lives, and with the odors of their partners. The couples who had more dissimilar HLA types reported a more satisfied sex life and satisfied partnership, but Croy cautions that it was a small effect. "It's not like they were super satisfied or not satisfied at all. It's a slight difference," she says.
Croy says we're much more likely to choose a partner based on appearance, sense of humor, intelligence and common interests.
Other studies have reported no preference for HLA difference in sexual attraction. Tristram Wyatt, a zoologist at the University of Oxford in the U.K. who studies animal pheromones, says it's been difficult to replicate the original T-shirt study. And one of the caveats of the original study is that women who were taking birth control pills preferred men who were more immunologically similar.
"Certainly, we learn to really like the smell of our partners," Wyatt says. "Whether it's the reason for choosing them in the first place, we really don't know."
Wyatt says he's skeptical of DNA-based dating apps because there are many subtypes of HLA genes, meaning there's a fairly low chance that your HLA type and your romantic partner's would be an exact match, anyway. It's why finding a suitable match for a bone marrow transplant is difficult; a donor's HLA type has to be the same as the recipient's.
"What it means is that since we're all different, it's hard statistically to say who the best match will be," he says.
DNA-based dating apps haven't yet gone mainstream, but some people seem willing to give them a try. Since Pheramor's launch a little over a year ago, about 10,000 people have signed up to use the app, about half of which have taken the DNA test, Barreto says. By comparison, an estimated 50 million people use Tinder, which has been around since 2012, and about 40 million people are on Bumble, which was released in 2014.
In April, Barreto launched a second service, this one for couples, called WeHaveChemistry.com. A $139 kit includes two genetic tests, one for you and your partner, and a detailed DNA report on your sexual compatibility.
Unlike the Phermor app, WeHaveChemistry doesn't provide users with a numeric combability score but instead makes personalized recommendations based on your genetic results. For instance, if the DNA test shows that your HLA genes are similar, Barreto says, "We might recommend pheromone colognes, working out together, or not showering before bed to get your juices running."
Despite her own research on HLA and sexual compatibility, Croy isn't sure how knowing HLA type will help couples. However, some researchers are doing studies on whether HLA types are related to certain cases of infertility, and this is where a genetic test might be very useful, says Croy.
"Otherwise, I think it doesn't matter whether we're HLA compatible or not," she says. "It might give you one possible explanation about why your sexual life isn't as satisfactory as it could be, but there are many other factors that play a role."
The Friday Five covers five stories in research that you may have missed this week. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on scientific creativity and progress to give you a therapeutic dose of inspiration headed into the weekend.
Here are the promising studies covered in this week's Friday Five:
- Research on a "smart" bandage for wounds
- A breakthrough in fighting inflammation
- The pros and cons of a new drug for Alzheimer's
- Benefits of the Mediterranean diet - with a twist
- How to recycle a plastic that was un-recyclable
Sexually transmitted infections (STIs) are surging across the U.S. to 2.5 million cases in 2021 according to preliminary data from the CDC. A new prevention and treatment strategy now in clinical trials may provide a way to get a handle on them.
It's easy to overlook the soaring rates of gonorrhea, chlamydia, and syphilis because most of those infections have few or no symptoms and can be identified only through testing. But left untreated, they can lead to serious damage to nerves and tissue, resulting in infertility, blindness, and dementia. Infants developing in utero are particularly vulnerable.
Covid-19 played havoc with regular medical treatment and preventive care for many health problems, including STIs. After formal lockdowns ended, many people gradually became more socially engaged, with increases in sexual activity, and may have prioritized these activities over getting back in touch with their doctors.
A second blow to controlling STIs is that family planning clinics are closing left and right because of the Dobbs decision and legislation in many states that curtailed access to an abortion. Discussion has focused on abortion, but those same clinics also play a vital role in the diagnosis and treatment of STIs.
Routine public health is the neglected stepchild of medicine. It is called upon in times of crisis but as that crisis resolves, funding dries up. Labs have atrophied and personnel have been redirected to Covid, “so access to routine screening for STIs has been decimated,” says Jennifer Mahn, director of sexual and clinical health with the National Coalition of STD Directors.
A preview of what we likely are facing comes from Iowa. In 2017, the state legislature restricted funding to family health clinics in four counties, which closed their doors. A year later the statewide rate of gonorrhea skyrocketed from 83 to 153.7 cases per 100,000 people. “Iowa counties with clinic closures had a significantly larger increase,” according to a study published in JAMA. That scenario likely is playing out in countless other regions where access to sexual health care is shrinking; it will be many months before we have the data to know for sure.
A decades-old antibiotic finds a new purpose
Using drugs to protect against HIV, either as post exposure prophylaxis (PEP) or pre-exposure prophylaxis (PrEP), has proven to be quite successful. Researchers wondered if the same approach might be applied to other STIs. They focused on doxycycline, or doxy for short. One of the most commonly prescribed antibiotics in the U.S., it’s a member of the tetracycline family that has been on the market since 1967. It is so safe that it’s used to treat acne.
Two small studies using doxy suggested that it could work to prevent STIs. A handful of clinical trials by different researchers and funding sources set out to generate the additional evidence needed to prove their hypothesis and change the standard of care.
Senior researcher Victor Omollo, with the Kenya Medical Research Institute, noted, “These are prevention interventions that women can control on their own without having to seek or get consent from another person,” as is the case with condom use.
The first with results is the DoxyPEP study, conducted at two sexual health clinics in San Francisco and Seattle. It drew from a mix of transgender women and men who have sex with men, who had at least one diagnosed STI over the last year. The researchers divided the participants into two groups: one with people who were already HIV-positive and engaged in care, while the other group consisted of people who were on PrEP to prevent infection with HIV. For the active part of the study, a subset of the participants received doxy, and the rest of the participants did not.
The researchers intentionally chose to do the study in a population at the highest risk of having STIs, who were very health oriented, and “who were getting screened every three months or so as part of their PrEP program or their HIV care program,” says Connie Celum, a senior researcher at the University of Washington on the study.
Each member of the active group was given a supply of doxy and asked to take two pills within 72 hours of having sex where a condom was not used. The study was supposed to run for two years but, in May, it stopped halfway through, when a safety monitoring board looked at the data and recommended that it would be unethical to continue depriving the control group of the drug’s benefits.
Celum presented these preliminary results from the DoxyPEP study in July at the International AIDS Conference in Montreal. “We saw about a 56 percent reduction in gonorrhea, about 80 percent reduction in chlamydia and syphilis, so very significant reductions, and this is on a per quarter basis,” she told a later webinar.
In Kenya, another study is following a group of cisgender women who are taking the same two-pill regimen to prevent HIV, and the data from this research should become available in 2023. Senior researcher Victor Omollo, with the Kenya Medical Research Institute, noted that “these are prevention interventions that women can control on their own without having to seek or get consent from another person,” as is the case with condom use, another effective prevention tool.
Antibiotic resistance is a potentially big concern. About 25 percent of gonorrhea strains circulating in the U.S. are resistant to the tetracycline class of drugs, including doxy; rates are higher elsewhere. But resistance often is a matter of degree and can be overcome with a larger or longer dose of the drug, or perhaps with a switch to another drug or a two-drug combination.
Research has shown that an established bacterial infection is more difficult to treat because it is part of a biofilm, which can leave only a small portion or perhaps none of the cell surface exposed to a drug. But a new infection, even one where the bacteria is resistant to a drug, might still be vulnerable to that drug if it's used before the bacterial biofilm can be established. Preliminary data suggests that may be the case with doxyPEP and drug resistant gonorrhea; some but not all new drug resistant infections might be thwarted if they’re treated early enough.
“There are some tradeoffs” to these interventions, Celum says, and people may disagree on the cost of increased resistance balanced against the benefits of treating the STIs and reducing their spread within the community.
Resistance does not seem to be an issue yet for chlamydia and syphilis even though doxy has been a recommended treatment for decades, but a remaining question is whether broader use of doxy will directly worsen antibiotic resistance in gonorrhea, or promote it in other STIs. And how will it affect the gut microbiome?
In addition, Celum notes that we need to understand whether doxy will generate mutations in other bacteria that might contribute to drug resistance for gonorrhea, chlamydia or syphilis. The studies underway aim to provide data to answer these questions.
“There are some tradeoffs” to these interventions, Celum says, and people may disagree on the cost of increased resistance balanced against the benefits of treating the STIs and reducing their spread within the community. That might affect doctors' willingness to prescribe the drug.
Turning research into action
The CDC makes policy recommendations for prevention services such as taking doxy, requiring some and leaving others optional. Celum says the CDC will be reviewing information from her trial at a meeting in December, but probably will wait until that study is published before making recommendations, likely in 2023. The San Francisco Department of Public Health issued its own guidance on October 20th and anecdotally, some doctors around the country are beginning to issue prescriptions for doxy to select patients.
About half of new STIs occur in young people ages 15 to 24, a group that is least likely to regularly see a doctor. And sexual health remains a great taboo for many people who don't want such information on their health record for prying parents, employers or neighbors to find out.
“People will go out of their way and travel extensive distances just to avoid that,” says Mahn, the National Coalition director. “People identify locations where they feel safe, where they feel welcome, where they don't feel judged,” Mahn explains, such as community and family planning clinics. They understand those issues and have fees that vary depending on a person’s ability to pay.
Given that these clinics already are understaffed and underfunded, they will be hard pressed to expand services covering the labor intensive testing and monitoring of a doxyPEP regimen. Sexual health clinics don't even have a separate line item in the federal budget for health. That is something the National Association of STI Directors is pushing for in D.C.
DoxyPEP isn't a panacea, and it isn't for everyone. “We really want to try to reach that population who is most likely going to have an STI in the next year,” says Celum, “Because that's where you are going to have the biggest impact.”