STD Awareness: Can Gene Editing Cure HIV?

For the first time in history, someone with HIV has been treated with cells edited in the lab. It was a bold attempt to try to replicate previous successes in “curing” HIV through bone marrow transplants, but the results were a mixed bag.

Your DNA is like a book, and each sentence is a gene. Imagine a word is misspelled. Sometimes, a misspelling won’t affect your ability to understand the sentence, but other times, it will be so bad that you’ll have trouble figuring out the intended meaning. Think of the difference between “I drive a car” and “I driv a car,” or “I like food” and “I like flod.” You might not be able to tell what that last sentence is even trying to say! Those misspellings are mutations, and sometimes mutations are relatively benign (“I driv a car”), while other times they can cause diseases (“I like flod”).


A mutated version of the CCR5 gene confers near-immunity to HIV — but increases susceptibility to other viruses.


CRISPR, pronounced crisper, is a powerful new technology that can edit genes. By cutting DNA at a specific location and replacing some of the letters in the genetic alphabet, CRISPR can edit genes like you can edit a document using “find and replace.” The hope is that, someday, CRISPR could be used to fight disease by tweaking faulty genes. Continue reading

STD Awareness: The Vaginal Microbiome and Cervical Cancer

Cervical cancer is caused by human papillomavirus (HPV), which has been nicknamed “the common cold of STDs” — because pretty much every sexually active person will get it at some point. Luckily, that scary stat is poised to change as more people receive the HPV vaccination, which protects against nine major strains of the virus.

HPV jumps easily from person to person, spread by pretty much all types of sexual contact. For most people, the infection clears up within 8 to 13 months, but sometimes the infection develops into a chronic condition, which increases risk for certain cancers — including cervical cancer, but also cancers of the anus, genitals, and throat. Unfortunately, it’s hard to predict if your immune system will vanquish your infection, or if you’ll develop a chronic infection.

Members of the lactobacilli family, keeping vaginas healthy across the globe. Image: Josef Reischig

Luckily, the vagina has some tricks up its sleeve to protect itself from HPV, and some of its best weapons are bacteria. Yep — a healthy vagina isn’t germ-free. To the contrary, it needs lactobacilli and other beneficial microbes to maintain a healthy environment. Bacteria from the Lactobacillus genus produce lactic acid and other chemicals, which help keep dangerous bugs away. Vaginal environments in which Lactobacillus gasseri dominate, for example, are more likely to clear HPV infections. L. crispatus helps trap HIV in a thick mucus, reducing infection risk. Other lactobacilli species secrete chemicals that ward off yeast infections. Sometimes, however, good bacteria lose this turf war, and “bad guys” move in.


The population of microbes that live in your vagina are known collectively as the vaginal microbiome.


University of Arizona researchers in Phoenix performed a “census” of the vaginal microbial communities of 100 premenopausal women. They learned that women who have cervical cancer or precancerous abnormalities have drastically different vaginal microbiomes. Healthy vaginas were generally dominated by lactobacilli, but as cervical health declined, their populations declined, and “bad” bacteria took over. One such bad guy, called Sneathia, was linked to HPV infection, precancer, and cervical cancer.

Which Came First?

Finding a new vaginal “bad guy” was exciting, and Sneathia had previously been linked to other gynecological problems, ranging from bacterial vaginosis to pregnancy complications. But the researchers were looking at a snapshot in time — they didn’t know what came first, the Sneathia or the cervical abnormalities. Were lactobacilli protecting the cervix whereas Sneathia were harming it, or did a chronic HPV infection set the stage for Sneathia to move in and thrive? It’s a real “chicken-and-egg” conundrum. Continue reading

STD Awareness: Winning One War on Cancer

Cancer starts with the uncontrolled division of cells.

The developed world is in the midst of a huge nosedive in genital warts and cervical “precancer” — all thanks to the human papillomavirus (HPV) vaccine. This simple shot trains the immune system to defend itself against HPV, a virus that causes genital warts and several types of cancer. Most sexually active people will be exposed to it in their lifetimes — it’s even been nicknamed the “common cold” of sexually transmitted infections.

Gardasil 9 protects against seven strains of HPV that collectively cause 90% of cervical cancers and anal cancers, plus the two HPV strains that are jointly responsible for 90% of genital warts. Vaccination also reduces the frequency of “precancers,” which are cellular abnormalities that can be treated before progressing into full-fledged cancer — meaning less time, money, and anxiety spent dealing with follow-up procedures and treatments.


The HPV vaccine is an anti-cancer vaccine.


The vaccine is safe and effective — and when we say “effective,” we mean it could lead to the eradication of HPV, and with it the cancers it causes. A recent analysis of 66 million vaccine recipients published in The Lancet points to plummeting rates of genital warts and precancer. Among teenage girls, there was an 83% drop in HPV-16 and HPV-18 infections (the two strains of HPV that together cause 70% of cervical cancers) — and cervical precancers were cut in half.

The most dramatic gains were made in countries that offered the HPV vaccine to both boys and girls. Additionally, there were even decreases in the HPV strains that aren’t covered by the vaccine — evidence of “cross-protection,” the phenomenon in which the immune system recognizes close relatives of the viruses it has been trained to attack. Even people who did not receive the vaccine were less likely to catch the virus, simply because their risk was reduced if their partners were vaccinated. Continue reading

STD Awareness: Can I Get Gonorrhea from Kissing?

Not all types of kissing feature the exchange of saliva.

Some pretty depressing news hit a couple of months ago, when headlines proclaimed kissing could allow gonorrhea to jump from one person to another.

We already knew gonorrhea could be transmitted during oral sex — a terrible fact, given that most people don’t use condoms or dental dams during oral sex. And we knew that oral gonorrhea is more likely to develop drug resistance, which could be helping to drive the possibly untreatable gonorrhea of the near future.


Mouth-to-mouth kissing could be transmitting gonorrhea right under our noses — literally.


Gonorrhea is most famous as an infection of the cervix or the urethra. But the bacteria that cause gonorrhea can thrive in other warm, moist areas of your body — not just the reproductive tract, but also in the mouth, throat, eyes, and anus. Unprotected oral sex can allow those bacteria to travel in either direction between one person’s genitals and another person’s throat.

But what about mouth-to-mouth kissing, like French kissing? Is that enough to allow these bacteria to hitch a ride from one mouth to another? Previous research, using a mathematical model, estimated that mouth-to-mouth contact might be a significant — and underappreciated — mode of gonorrhea transmission. But that was a mathematical model, a sophisticated equation using what we know about a population’s gonorrhea prevalence and sexual behavior to estimate how frequently the infection is transmitted from one mouth to another. Continue reading

STD Awareness: Trichomoniasis, the Pear-Shaped, Blood-Sucking, Silent Scourge

What’s shaped like a pear, hangs with a posse of bacteria, and is a silent scourge upon millions of urogenital tracts? I hope you guessed Trichomonas vaginalis, the single-celled parasite that causes trichomoniasis, or trich (pronounced “trick”). Trich is the most common curable sexually transmitted disease out there — currently afflicting around 3.7 million Americans and 156 million Earthlings.


These single-celled creatures pack a punch, but the body fights back.


When trich causes symptoms, sufferers might experience vaginal discharge (which sometimes has a bad odor), penile burning or discharge, spotting, and itching or swelling in the genital area. But around 70 percent of infections have no symptoms at all, making it a mostly “silent” disease. Based on the totality of the evidence, the Centers for Disease Control and Prevention (CDC) doesn’t currently recommend routine screening for trich in people without symptoms.

But it’s the subject of some debate. Since both symptoms and screenings are rare, and the disease isn’t reportable, some health experts worry that trich could be doing a lot of damage right under our noses. An infection during pregnancy could increase risk for preterm labor or low birth weight. It can increase risk for both acquiring and transmitting HIV from or to a partner. Women with trich are more likely to acquire an HIV infection when sexually exposed to the virus — in fact, one study estimated that 6.2 percent of all HIV infections among U.S. women could be attributed to trich. It’s also easier to catch HIV from a man with trich than from a man without trich. Continue reading

STD Awareness: Searching for an HIV Vaccine

Ever since the dawn of the AIDS era, researchers have worked nonstop to develop an HIV vaccine. In 1984, Margaret Heckler of the U.S. Department of Health and Human Services famously (over)promised that a vaccine would be ready for testing in two years. But it’s taken much, much longer. This Saturday, May 18, is HIV Vaccine Awareness Day, a celebration of the patients, community members, and scientists who are hard at work bringing this vaccine into existence.


Only one vaccine — still in the experimental stage — has shown any effectiveness against HIV.


Hiding from the Immune System

Vaccines are inspired by our own bodies’ ability to fight disease. Usually, when our immune system encounters a threat, it takes note of the viral “antigens,” which are like facial features — a button nose, say, or dramatically arched eyebrows — that make it instantly recognizable. It creates “antibodies,” weapons that can target those antigens like guided missiles. Often, the immune system can remember the distinguishing facial features so it’s ready to attack if the enemy ever returns — giving us immunity, possibly for life.

Vaccines take advantage of our natural ability to create these immune memories by exposing our immune systems to antigens without actually exposing us to infectious viruses. Think of it as a “wanted” poster that helps the immune system recognize “bad guys” before it actually sees them on the street, enabling it to attack and destroy them before they cause disease. Continue reading

STD Awareness: Can HIV Be Cured Now?

In 1991, when Timothy Ray Brown was in his 20s, he moved from the United States to Europe in search of adventure. His travels brought him to Berlin, where he put down roots and became a translator — but this newfound stability was quickly disrupted. A former boyfriend told him he had been diagnosed with HIV, the virus that causes AIDS, and suggested Brown be tested as well. The results were positive. Brown calculated he had about two more years left to live.

His fortunes changed the next year when antiretroviral drugs transformed HIV from a death sentence to a manageable chronic disease. Life went on. But 10 years later, in 2006, he started noticing changes. While he usually made a 14-mile round trip on his bike to and from work, a quick ride to a café one mile away left him so winded he had to stop halfway through.


We still don’t have an HIV cure that works for everyone.


He was diagnosed with leukemia, a type of cancer that affects certain types of blood cells. He immediately began chemotherapy, a taxing regimen that nearly killed him when an infection forced his doctors to induce a coma. And when the cancer came back, his doctors recommended a bone marrow transplant, which involved wiping out his immune system with drugs and radiation. A year later, after his leukemia came back, he received a second bone marrow transplant. Recovery was grueling. He descended into delirium, nearly went blind, and was temporarily paralyzed. He had to undergo physical therapy to relearn how to walk and talk.

Miraculously, he came out of this near-death experience in full remission from leukemia. But the bone marrow transplants hadn’t just gotten rid of his leukemia. They had gotten rid of his HIV infection, too. The media dubbed him the “Berlin patient.” Continue reading