STD Awareness: Genetics and the Gonococcus

Illustration: CDC

Illustration: CDC

Ever since the discovery of effective antibacterial therapies less than a century ago, humans have been able to easily cure gonorrhea, the sexually transmitted scourge that laid waste to fallopian tubes and robbed newborns of vision. Most of us in the developed world have forgotten that this disease was once a leading cause of infertility in women and blindness in babies — and still is in much of the developing world.

Unfortunately, gonococci — the species of bacteria that cause gonorrhea — have been evolving resistance to every antibiotic we’ve thrown at them, including sulfonamides, penicillins, tetracyclines, macrolides, fluoroquinolones, and narrow-spectrum cephalosporins. We have one remaining first-line gonorrhea treatment left: extended-spectrum cephalosporins, which include cefixime, which is taken orally, and ceftriaxone, which is administered as a shot — and resistance is emerging to those drugs, as well.

Gonococci don’t swap potato salad recipes at family reunions — they swap genetic material!

The emergence of antibiotic-resistant gonorrhea is considered one of the most pressing problems in infectious disease — just two years ago, the Centers for Disease Control and Prevention named it an “urgent threat,” and indeed, gonorrhea seems to be evolving resistance to drugs at quite a rapid clip. Gonococci can acquire resistance to antibiotics in three ways.

First, a genetic mutation can endow bacteria with special antibiotic-fighting powers, making it harder for a drug like penicillin to attach to their cells and destroy them. Such a mutant is more likely to gain evolutionary traction if it finds itself in an antibiotic-drenched environment in which resistance to that drug allows it to “outcompete” other bacteria. Indeed, antibiotic resistance was first documented in the 1940s, just years after sulfonamides and penicillin were introduced as the first effective cures for gonorrhea. Continue reading

STD Awareness: The Next Generation of Gardasil Is Coming!

noisemakersIt’s January, which means it’s time to festoon our surroundings with streamers, throw around the confetti, break out the noisemakers, and shout Happy Cervical Health Awareness Month!

And, in 2015, we have something huge to celebrate: Last month, the Food and Drug Administration (FDA) approved Gardasil 9, the next-generation HPV vaccine, which provides broader protection than the current version. Next month, the new and improved vaccine will start to be shipped to health care providers, and the Advisory Committee on Immunization Practices is expected to give the Centers for Disease Control and Prevention the green light to recommend the vaccine, after which insurance plans and the Vaccines for Children program should start covering it.

The newest version of Gardasil protects against the seven strains of human papillomavirus that together cause 90 percent of cervical cancers.

Why is this news so exciting for people who care about cervical health? Because, while the current version of Gardasil, which debuted in 2006, protects recipients from the two HPV strains that cause 70 percent of cervical cancers, Gardasil 9 will protect against seven strains of HPV that collectively cause 90 percent of cervical cancers. On top of that, both versions of Gardasil protect against the two HPV strains that are together responsible for 90 percent of genital warts.

Gardasil 9 has been shown to be highly effective in clinical studies, and it is safe to use, which means Gardasil just became an even more potent weapon against cancers caused by HPV. Not only that, but vaccination against HPV will also reduce the frequency of precancerous lesions, which are cellular abnormalities that can be treated before progressing into full-fledged cancer. Less pre-cancer means less time, money, and anxiety spent dealing with followup procedures after an abnormal Pap test, for example. Continue reading

STD Awareness: The Herpes Virus and Herpes Medications

herpes medicationOne of the most common sexually transmitted diseases (STDs) is herpes, which affects an estimated 1 out of 6 Americans between the ages of 14 and 49. Herpes is caused by a virus, and one reason that it’s so widespread is that the herpesvirus is ancient. Prehistoric, even — dinosaurs are thought to have been infected by herpesviruses! The Herpesviridae family is huge, with at least 100 members infecting mammals, birds, reptiles, bony fish, amphibians, and oysters.

Herpes drugs from the acyclovir family physically block herpes DNA from replicating — which is pretty amazing!

Humans can suffer from both oral herpes and genital herpes, which are caused by two types of the herpes simplex virus (HSV-1 and HSV-2). Recent genetic analysis reveals that the virus that causes cold sores, HSV-1, has been evolving with us since before we were Homo sapiens, diverging from the viruses that infected our common ancestors 6 million years ago. Interestingly, we didn’t acquire HSV-2 — which mostly causes genital herpes — until our Homo erectus ancestors caught it from early chimpanzees 1.6 million years ago, well before the emergence of modern Homo sapiens around 200,000 years ago.

Most people know what the virus doesgenital herpes can involve blisters, pain, and itching — but most people don’t know how the virus works. Luckily, scientists have uncovered a lot of the virus’ secrets — which has allowed them to develop some pretty effective drugs that we can use to foil herpes’ plans. Continue reading

Are Pap Tests Accurate?

If you follow health news, you might have noticed some controversy over certain cancer-screening methods: Does the evidence support mammograms as a tool to reduce breast cancer deaths? Are PSA tests effective in saving lives from prostate cancer? These are questions that we are beginning to answer as more and more evidence comes in. But don’t let these questions dissuade you from all cancer screening.

With regular Pap testing, cervical cancer is almost 100 percent preventable.

In fact, although we’re reevaluating data for other cancer-screening methods, we have mountains of solid evidence that the Pap test is one of the best cancer-screening methods out there. Because it detects signature mutations that mark cells as headed toward becoming cancerous, Pap testing detects “pre” cancer while other cancer-screening techniques, like mammography, only detect cancer.

Cervical cancer used to be a top killer in developed nations — and it remains a major cause of death in countries without widespread health-care access — but in the last 50 years, cervical cancer deaths fell by 70 percent in the United States, transforming cervical cancer from the leading cause of cancer death among American women to a less common, nearly preventable cancer. Despite this, you might hear people complain that the Pap test isn’t accurate, citing the possibility of receiving “false positive” or “false negative” results.

A Pap test looks for abnormalities in cervical cells, and you can receive one of these four results:

True Positive: Cellular abnormalities are detected, and they are in fact present. True Negative: Cellular abnormalities are not detected, and in fact the cells are normal.
False Positive: Cellular abnormalities are detected, but the cells are actually normal. False Negative: Cellular abnormalities are not detected, but are actually present.

When we receive a true positive result, we can receive treatment for precancerous lesions that in fact might otherwise lead to cancer. Likewise, when we receive a true negative result, no further treatment is needed. Continue reading

How Does HIV Cause AIDS?

diagram of a human immunodeficiency virus

Last week, we gave a general background of human immunodeficiency virus (HIV), the virus that causes AIDS by destroying the immune system. But how is HIV able to disable our immune systems so effectively, anyway? The answer lies in its structure.

HIV, just like any other virus, is made up of a tiny capsule with a small piece of genetic code inside. While most viruses we’re familiar with store their genes on a molecule called DNA, HIV contains two pieces of RNA, which is another type of gene-storing molecule. The HIV capsules also contain an enzyme called transcriptase, which “translates” the RNA into a strand of DNA that our cells can read. Our cells are then tricked into reading this DNA and producing more copies of the virus — which are then released from the host cell, at which point they are free to infect other cells. In this manner, an HIV infection slowly grows.

HIV targets our immune systems, the very mechanism that evolved to keep us safe from pathogens.

When a virus is introduced into a host’s body, immune cells pick it up and carry it to the lymphoid organs — which are a sort of meeting place for other types of immune cells, including CD4+ T helper cells (also called helper T cells). Helper T cells enlist the help of other immune cells, called killer T cells, which destroy cells infected with viruses. Helper T cells also activate the production of antibodies, molecules that are specialized to attach to a specific pathogen so that it can be destroyed. Normally, this is where the virus meets its end. Unfortunately, HIV is different from run-of-the-mill viruses in that it is specialized to invade helper T cells. Now, instead of coordinating an attack against HIV, the helper T cells have been hijacked — converted into factories for the production of yet more HIV. Continue reading

How Often Do I Need a Pap Test?

Almost 80 years ago, Dr. George Papanicolaou developed a simple test, the Pap test (also called the Pap smear), done in a doctor’s office to check for cervical cancer. During a pelvic exam, a doctor swabs a small sample of cervical tissue and looks for abnormal cells. If these precancerous cells are detected, it will lead to more tests or other more invasive treatments such as a colposcopy (in which actual tissue may be removed). In the 1930s, when Papanicolaou was developing his test, cervical cancer was more lethal than breast cancer. But since the development of this test, the number of women dying from cervical cancer has dropped dramatically. In 2009, of the 4,000 women in the United States who died of cervical cancer, most had never been screened or had not been screened in the 10 years before their diagnosis.

This year, the U.S. Preventive Services Task Force recommended less frequent Pap testing.

Cervical cancer is most common in women between ages 35 and 55, and usually develops from a human papillomavirus or HPV infection. Not all HPV infections lead to cervical cancer, and it can take decades for a persistent infection with a high-risk type of HPV to become cancer. High-risk HPV types are sexually transmitted and can lead to cervical cancer and also anal, penile, and oral cancers.

There are two types of screening: Pap tests and HPV tests. While they both require a pelvic exam in which cells are taken from the cervix, Pap tests look for abnormal or precancerous cells, and HPV tests look for DNA or RNA from high-risk HPV types in cervical cells. Both tests are used to try to catch cervical cancer in its earliest stages so that it can be successfully treated. Continue reading

World Hepatitis Day: The History of the Hepatitis B Vaccine

Hepatitis B particles are made of a protein shell with viral DNA inside. Image: CDC

A few hepatitis B virus particles amid an excess of surface proteins. Image: CDC

In the early 1970s, Ted Slavin, a hemophiliac, learned his blood was special. Over a lifetime of transfusions, he had slowly amassed a huge collection of antibodies, which are proteins produced by the immune system that attach to invaders, such as viruses and bacteria. When he started receiving transfusions in the 1950s, blood wasn’t screened for diseases, which meant that he’d been repeatedly exposed to some pathogens. His immune system manufactured large amounts of protective antibodies to battle these constant invaders, one of which was hepatitis B virus (HBV) — resulting in blood with extremely high concentrations of hepatitis B antibodies.

After sunshine and smoking, hepatitis B is the most common cause of cancer.

His physician relayed this discovery to Slavin — most doctors wouldn’t have bothered, and in fact might have surreptitiously sold his blood to researchers. Back then, scientists were at work on a hepatitis B vaccine, and hepatitis B antibodies were a hot commodity. Likewise, Slavin needed money — his medical condition precluded regular work, and treatments were costly. He contracted with labs and pharmaceutical companies to sell his antibodies directly, for as much as $10 per milliliter and up to 500 milliliters per order.

When someone has a chronic HBV infection, the virus has “hijacked” some of his or her cells, “tricking” them into manufacturing copies of the virus. A virus consists of an outer protein shell housing genetic information — the blueprint that cells follow when they produce virus copies. When hepatitis B viruses are manufactured in cells, an excess of surface proteins is produced — these waste products litter the bloodstream, and testing for their presence allows people to be diagnosed with HBV infections. These surface proteins are called antigens — and as luck (or evolution) would have it, the antibodies our immune systems produce can attach to viral antigens, helping us to keep pathogens at bay. Continue reading