Most people wouldn’t mind eating a tomato or banana in order to get a vaccine. But Roy Curtiss is trying to convince people to gulp down Salmonella! Salmonella is a bacterium that likes to hang out in raw poultry and uncooked eggs. It can cause diseases ranging from food poisoning to typhoid fever.

If Curtiss has his way, he will have children drinking liquids laced with this nasty bug! What’s the big idea?

Curtiss is a professor of life sciences at ASU. He is also an expert on Salmonella bacteria. Through genetic engineering, he hopes to develop a form of Salmonella that can deliver a vaccine without causing any harm.

His latest project is to prevent infection from Streptococcus pneumonia, the bacteria that cause pneumonia and meningitis. He also is working on a similar vaccine for bird flu.

“Part of our goal is to develop a vaccine that is safe for newborns or infants,” Curtiss explains. “Most people would say, ‘you have got to be kidding me! With a bacteria like salmonella?’ Yes. We can tame it so it will be a friend of a newborn and not cause any harm.”

Curtiss and his research team have shown that their vaccine protects mice from dying when they are exposed to bacteria that cause pneumonia. It protected them even when they were exposed to a dose 100 times bigger than what would normally kill them.

The current pneumonia vaccine for infants and toddlers requires four separate shots given at specific intervals. This makes it hard to deliver to people in less-developed countries. Many of these people are spread out over large areas. There aren’t many clinics and trained healthcare workers, so people have to travel far to reach them. They don’t usually have cars.

By providing a single-dose oral vaccine, Curtiss hopes to make it easier for people in poor countries to get it. In addition, current pneumonia vaccines are expensive to produce. They cost an average of $40 per dose. Curtiss’ vaccine would cost only about $1 per dose.

But why did he choose Salmonella? The bacterium is actually a good choice for delivering vaccines because it has evolved many ways to get past the immune system. The features that make it so dangerous as a disease also make it a perfect tool for shuttling vaccines through the digestive system.

Salmonella has evolved ways to survive the acid in your stomach, the bile in your small intestine, and the high pressure and toxic iron in your large intestine. After getting through that obstacle course of dangers, the persistent bacteria attach to the cells that line your intestine. They get the cells to take them up and force their entry into your body.

Curtiss and his team have found a way to delay the process through which Salmonella causes disease. They have also designed the bacteria to self-destruct after a certain period of time.

“In the past, we would put anywhere from two to four genetic modifications into some of these live salmonella vaccines. The ones we make now have 15 to 25 genetic alterations. They are very different critters.”

(first published in 2008)