Your next flu vaccine may be on dental floss

A few years ago, Rohan SJ Ingrole, a chemical engineer at Texas Tech University and his research partner, Harvinder Gill, an engineer at North Carolina State University, decided to test out an idea: can a vaccine be delivered through the gums between teeth? To find the answer, they set out on a radical experiment — they began to floss mice.

The data they got exceeded expectations. Lab mice flossed with special threads coated with inactivated virus developed high antibody levels and survived lethal flu exposure. The unvaccinated mice did not. Flossed mice even had more T cells, a type of white blood cells the body deploys to fight off pathogens.

It was a breakthrough — Ingrole and Gill had used an everyday item to deliver a life-saving tool.

“It transformed how we thought about vaccines,” Ingrole, originally from Kolhapur in Maharashtra, told TOI . “What we found was a painless, easy-to-use method that could reach people who don’t have access to a vaccine or are worried about getting a shot because of a fear of needles.”
Their findings were recently published in ‘Nature Biomedical Engineering’.

WHAT ’ S IN THE GUMS?
Ingrole and Gill’s method tapped into an overlooked part of the mouth: the tiny gum pocket between the teeth, known to dentists as the gingival sulcus. Between the sulcus and a tooth is a layer of ‘sealant’ known as the junctional epithelium, which packs a layer of tissue that is unusually “open” and rich in immune cells — making it the ideal spot to deliver a vaccine.

“Most parts of the mouth don’t let much through,” Ingrole said. “But this tissue is different. It’s more permeable and packed with immune cells that can grab the vaccine and help the body build protection.”

As for the delivery vehicle, dental floss is thin, flexible and already in use by millions of people worldwide, every day.
Overall, the concept by the two engineers was remarkably simple. Floss coated with a dry vaccine is slid between the teeth and into the gum pocket. This coating then dissolves, allowing the vaccine to seep into the tissue. Immune cells pick it up, triggering both whole-body immunity and “mucosal immunity”, which forms the frontline defence in the nose, mouth and gut, where many infections begin.

HUMAN TESTS
After their tests on mice, Ingrole and Gill got 27 human volunteers to use floss picks coated with food dye, to see if the method could deliver material to the gum pocket. Around 60% of the dye ended up at the right spot.

Also, compared with other noninvasive methods like under-thetongue drops or nasal sprays, floss-based delivery performed just as well or better. Data showed it triggered stronger immune responses than the under-the-tongue method and matched nasal sprays in protection, Ingrole said.

CHALLENGES
The ‘floss vaccine’ has hurdles to clear. Dose consistency is the biggest challenge, as the human dye tests showed some variation in how much material had reached the gum pocket. “And babies don’t have developed gum pockets, so they would need something different,” Ingrole said.
Vaccine expert T Jacob John, who was not part of the study, had another question: “In an injection, the empty syringe proves the vaccine was delivered. The shot also raises a swelling (weal). When vaccine is delivered into the gingival sulcus, how do we know it has been properly delivered?” Once these challenges are cleared, Ingrole and Gill are confident of success. “Imagine your yearly flu vaccine arriving by post,” Ingrole said. “You floss once and you’re protected. It’s painless, you can do it yourself and it works. That’s the future we’re working towards.”