A vaccine combating Staphylococcus bacteria, even methicillin-resistant strains, may be available on the market in just a handful of years.
News of such a vaccine is a boon for healthcare providers across the country as antibiotic resistance, climbing healthcare costs and changing payment models transform how the industry is approaching managing healthcare-associated infections.
Researchers at the University of Iowa in Iowa City have developed a vaccine that targets toxins produced and secreted by Staphylococcus bacteria. What's more, the vaccination has been found to completely protect against Staphylococcus bacteria and eliminate any traces of the bacteria in the host. Instead of targeting Staphylococcus cell surface molecules like most vaccines, the Iowa researchers' vaccine directly targets three common Staphylococcus toxins: toxic shock syndrome toxin, Staphylococcus enterotoxins, and a cytotoxin called alpha toxin. These three toxins have been mutated to have no toxicity.
"Instead of immunizing against [Staphylococcus causing bacteria], we prevented the organism from being able to set up the disease," says Patrick Schlievert, PhD, professor and chair of microbiology at the University of Iowa Carver College of Medicine and lead researcher of the study.
In animal model trials, the vaccine provided sterilizing immunity, meaning it produced an immune response completely eliminating the infection. In one trial, Dr. Schlievert and researchers introduced Staphylococcus bacteria into rabbits at extremely high doses, up to four million times more bacteria than normal. When the researchers injected their vaccine and then administered the Staphylococcus bacteria into the rabbits' lungs, 86 of the 88 rabbits had sterilizing immunity after seven days.
Dr. Schlievert said the use of the rabbit animal model is an important, yet often overlooked, element in animal model trials regarding Staphylococcus vaccines.
"There's kind of a dirty little secret behind the scenes, but it's important," he says. "Nobody has been able to get solid protection in mice from Staphylococcus aureus. Even when they reduce the fatality rate a little bit in the mice, these mice are a walking bag of pus. They're just full of Staphylococcus."
The reason, he says, is because mice are exponentially more resistant to superantigens (toxic shock syndrome toxin and enterotoxins) and cytotoxins (alpha toxin), substances causing immune response dysfunction, than rabbits and humans. Mice are more physiologically similar to nonhuman primates than they are to humans, while rabbits are more closely connected to humans.
"When [the U.S. Food and Drug Administration] tells people to use two animal models, everyone jumps on mice and nonhuman primates. We've done all our studies on rabbits," he says.
The next step for the Iowa researchers is conducting safety studies, which Dr. Schlievert says could be complete as early as in the next couple of years, pending FDA approval. If all goes well, the implications of this vaccine could be greatly effective and potentially eliminate the threat of certain Staphylococcus infections for good.
"The bad thing is Staphylococcus aureus varieties come and go. They emerge and they disappear and new strains come and they disappear," Dr. Schlievert says. "The thing we've seen consistently over the years is these three targets that we have are maintained over the long term, so we think by protecting against them, we will have a vaccine that will work against any variety of Staphylococcus aureus and would extend into the future."
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