If you could choose the method of administering a vaccine, would you prefer a needle or a skin cream? The latter may soon be a viable option as Stanford scientists have used a topical cream to vaccinate guinea pigs against tetanus.
The secret lies in a bacteria that lives on the skin: Staphylococcus epidermidis. Although harmless, it triggers a strong immune response in people, in what appears to be a preventative defense against microbes that enter the bloodstream through cuts and scrapes.
“We obtained blood from human donors and found that their circulating levels of antibodies directed against Staphylococcus epidermidis were as high as anything we are routinely vaccinated against,” said researcher Michael Fischbach, quoted by .
The team began by carrying out experiments on rats, which do not have the Staphylococcus epidermidis on the skin. When the bacteria was placed on their heads, antibody levels increased over the next six weeks, reaching higher levels. higher than those provided by normal vaccines.
The team questioned whether this mechanism could be used as a non-invasive vaccination method against more dangerous pathogens and found that a protein called aap on the surface of the bacteria is responsible for triggering the production of antibodies.
That’s how they decided to modify it to contain a tetanus toxin.
Then the scientists repeated the experiment, giving some animals an improved version of the Staphylococcus epidermidis with tetanus and the normal version for others.
After a few doses to the skin over six weeks, their antibody levels were tested and those who received the bacteria showed extremely high levels of antibodies against tetanus.
The final test consisted of injecting lethal doses of tetanus into rats and everyone who received the bacteria became infected. symptom-free.
Even when they were given a dose six times the lethal dose of tetanus, they survived. Conversely, everyone who received the natural version of Staphylococcus epidermidis succumbed to the infection.
According to the team, this mechanism can be applied to a wide range of pathogens. In another test carried out in the laboratory, experts exchanged tetanus toxin for diphtheria toxin and discovered that it produced, in the same way, a powerful immune response in guinea pigs.
Taking the results into consideration, this could prove to be a new method of administering various types of vaccines.
