Scientists think they finally know why a staph vaccine failed

Scientists think they finally know why a staph vaccine failed

After several vaccines were shown to be effective in animals, they subsequently failed in human trials. But now this decades-old dilemma has finally been resolved.

Staphylococcus aureus It is a germ that infects many people, especially on the skin and nose. In general, bacteria are harmless. However, sometimes harmless bacteria turn into a pathogen, causing various skin infections or even food poisoning. For more than a century, scientists have been searching for an effective vaccine, but without much success. And now scientists think they finally know why.

mystery
Researchers have been baffled for decades. The search for a staph vaccine always seems to be a dead end. At least fifteen successful preclinical animal studies have been conducted over the past thirty years, demonstrating the efficacy of proposed vaccines. But in all subsequent human trials, these vaccines failed. “It’s a long-standing problem and one of the most perplexing problems facing staphylococcus,” said study researcher George Liu. None of these human trials have been successful. And scientists don’t understand why.”

urgent
However, the need for an effective vaccine is becoming increasingly urgent. This is mainly due to the spread of methicillin-resistant Staphylococcus aureus (MRSA). Also known as “hospital bacteria,” these bacteria have become resistant to many of the antibiotics commonly used to treat staphylococcus. Bacteria mainly cause infections and epidemics in hospitals and health care institutions. A recently published study found that bacterial resistance to antimicrobials led to tens of millions of infections and 1.2 million deaths worldwide in 2019, with MRSA as the leading cause. Liu concludes, “Vaccines are the most effective way to reduce the health burden and treat antibiotic resistance.”

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In a new study, Liu and his colleagues set out to find an answer to the most pressing question: How did the failure of a staph vaccine happen? The researchers hypothesized that it could be related to previous exposure to the bacteria. Lab mice rarely come into contact aureus bacteriaScholar Chi Ming Cai said. “But people are exposed to staphylococcus from the first weeks of life.” In fact, within two months, half of the babies have active colonies and abundant antibodies. “So we suspect that if the mice were also infected before vaccination, the proposed vaccines might not work in them as well,” Tsai said.

experiments
To test this hypothesis, the researchers conducted a series of experiments with the IsdB vaccine. A vaccine developed to combat staphylococcus, but has not been shown to be effective in humans. Indeed, the vaccine worked in mice that were not exposed to staphylococcus. But when the researchers vaccinated mice that had previously come in contact with the bacteria, the vaccine did nothing. Researchers also discovered why. It seems that aureus bacteria Develop strong defense mechanisms. “The bacteria have devised a strategy to render our immune response to them ineffective,” Tsai explains.

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According to the researchers, this explains a lot. Thus, they say, it explains why all human trials of proposed staphylococcal vaccines have failed in the past. “It’s also possible that the same principle explains why trials with many other vaccines have failed,” Tsai says.

They are promising results. Because now that researchers better understand why previous vaccine trials failed, they can also actively look for ways to deal with the problems. Researchers already have an idea of ​​how to do this. For example, they were able to use the newly acquired knowledge to develop a vaccine that was also successful in mice previously exposed to aureus bacteria† Tsai concludes, “If our findings are confirmed, an effective staphylococcal vaccine may not be far off.”

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