"Don't Spit! It is indecent. It is dangerous. It is against the law. It Spreads Disease." In the late 19th and early 20th centuries, public admonishments like this one from the Anti-Tuberculosis League in New York City started to crop up in urban areas. Americans were terrified of tuberculosis, and with good reason: At the time, TB was the leading cause of death in the United States, killing 150,000 people and infecting more than 1.5 million every year. Originally thought to be a hereditary disease, tuberculosis was revealed to be spread by bacteria in 1882, when bacteriologist Robert Koch discovered the tubercle bacillus. As this new germ theory of TB became well known, doctors and city dwellers became concerned about the "promiscuous spitting" problem—on sidewalks, in train stations, and in other public places. "In neither [Denver nor Colorado Springs] can a woman walk down the street without gathering on her skirts a sickening mass of bacilli-laden sputa of all ages and stages quite sufficient . . . to sow a family harvest of death," ran an 1896 editorial in the Denver Medical Times.
A century later, medical researchers are looking more kindly at spit. In fact, the Johns Hopkins School of Nursing has an entire lab devoted to the stuff. The Center for Interdisciplinary Salivary Bioscience Research is directed by Doug Granger, a professor of acute and chronic care who holds joint appointments in the School of Nursing, the Bloomberg School of Public Health, and the School of Medicine. Granger has been at the forefront of salivary research for the past 20 years, founding two companies to support salivary researchers—Salimetrics in 1998 and, more recently, SalivaBio, a one-product company that launched earlier this year with help from the Johns Hopkins Technology Transfer Office. Sometimes referred to as the "Spit King" by colleagues, Granger has fun with it.
"People say, 'You've got to be kidding me. You guys need saliva? I've got tons of saliva, I'll give you all you want,'" Granger says with a laugh.
Granger first became interested in salivary research in the early 1990s while working as a postdoc at the University of California, Los Angeles, where he was doing a behavioral study with children. Finding it difficult to get children involved in a study that required multiple blood draws, Granger and his colleagues started looking into saliva collection, which was emerging as a less invasive alternative to blood tests. The problem, Granger says, was that in the early '90s, saliva bioscience was still a fledgling field. He and his colleagues found that the assays being run weren't really designed for saliva; they were modifications of blood tests. And research protocols were crude and not uniform between labs. Realizing that there was enormous room for improvement, Granger and his colleagues dived right in. He says, "We spent the next 20 years working on the details of how do you collect saliva from an insect, how do you collect saliva from a walrus, how do you collect saliva from a horse, from an adult, from somebody who's sleeping? Does it change the way the measurement is done when you have a material that absorbs the sample, or are there other ways to get the sample out of their mouths that would be minimally invasive, that would preserve the integrity of the specimen?"
Along the way, salivary bioscience researchers have made some big strides. The leading edge of this research, says Granger, is detecting HIV in saliva. In fact, OraSure Technologies, a company that has been producing oral fluid HIV tests for years, is currently developing an over-the-counter version that, if approved, will allow consumers to test themselves at home.
Granger says that more recent work has come out of behavioral studies, with researchers looking not only at individuals but at correlations among groups. For example, a lot of early saliva research focused on the stress hormone cortisol. A recent study found that cortisol levels are correlated between mothers and their babies, and researchers saw similar correlations between college students who were seriously dating. "This raised some really fascinating questions for the researchers about the shared experience and the notion of contagion," Granger says. "My level of stress hormone is not just driven by what I'm experiencing, but it's also driven by what the people around me are experiencing. There's some really cool stuff about social networks. It connects working groups and families and sports teams and special forces teams."
Researchers working at Granger's center are exploring other applications, such as a recent study that tested the use of spit screening to detect heart disease risk. The study, published in the May issue of Brain, Behavior, and Immunity, found saliva to be a reliable measure of CRP (C-reactive protein), a risk factor for heart disease. The possibility of one day using a saliva test instead of a blood test, Granger says, could increase the number of patients who get tested regularly, leading to more early detection.
Granger teaches "spit camps" all over the United States to help researchers in the social sciences and other disciplines incorporate salivary bioscience into their research. "Saliva is a great tool because they can do it really simply," says Granger. "They don't have to have a phlebotomist, they don't have to have their own laboratory. They can come to spit camp for two days and learn the basics of what they need to know."
Spit has come a long way in 100 years. Far from being the problem, spit could hold answers. So, please spit (at least for research purposes). It is safe. It is painless. It helps detect disease.