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Unconventional Vaccine Could Combat MRSA

MRSA bacterial.
Credit: CDC / Unsplash.
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What if a vaccine, given to patients just before or after arriving at the hospital, could protect them against lethal superbugs that lurk in health care settings?

That’s the premise behind an experimental vaccine invented by a USC-led team and patented by the university. Researchers designed the formula to prevent serious infections from drug-resistant pathogens. A new study shows that a single dose, administered in mouse models, put immune cells into “Incredible Hulk” mode, providing rapid protection against nine different bacteria and fungi species.

“It’s an early warning system. It’s like Homeland Security putting out a terror alert. ‘Everybody, keep your eyes open. Keep an eye out for suspicious packages’,” said senior author Brad Spellberg, chief medical officer at the USC-affiliated Los Angeles General Medical Center (formerly Los Angeles County+USC Medical Center). “You’re alerting the soldiers and tanks of your immune system. The vaccine activates them. ‘Oh my god, there’s danger here. I better turn into the Hulk.’ I mean, when you have bad superbugs lurking, that’s when you want the Hulk waiting to pounce rather than Dr. Banner, right?”

The study appears Wednesday in Science Translational Medicine.

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The USC Stevens Center for Innovation — the technology licensing office for USC — successfully filed for a patent on the vaccine. The National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, gave startup company ExBaq LLC nearly $1 million in the form of a small-business grant, aimed at speeding up solutions to high-priority problems.

“The pandemic stimulated unprecedented innovation in vaccine development, where federal funding and university-industry partnerships were game changers for translating promising discoveries from academic labs for the good of all,” said Ishwar K. Puri, senior vice president of research and innovation at USC. “We are both pleased and proud of the critical support the USC Stevens Center provided to enable the development of ExBaq’s experimental vaccine that protects vulnerable populations from serious infections.”

Every year, health care-acquired infections kill more than 90,000 people in the United States and rack up health care costs between $28 billion and $45 billion. On any given day, about 1 in 31 hospital patients has at least one health care-associated infection, according to the Centers for Disease Control and Prevention.

Vaccine aimed at infections often caused by superbugs such as MRSA

In many cases, infections are caused by so-called superbugs such as MRSA — short for methicillin-resistant Staphylococcus aureus — or Acinetobacter baumannii. The infections spread via contaminated surfaces or equipment such as catheters or ventilators or though person to person spread, often from contaminated hands. Risk is highest among patients in the ICU, resulting in surgical site infections, bloodstream infections, urinary tract infections and ventilator-associated pneumonia.

Typical vaccines usually prompt the body to make antibodies against a specific pathogen. Despite the high incidence of health care-acquired infections, there are currently no FDA-approved vaccines that prevent the most serious antibiotic-resistant infections.

“Even if there were such vaccines, multiple vaccines would have to be deployed simultaneously to protect against the full slate of antibiotic-resistant microbes that cause health care-acquired infections,” said Brian Luna, assistant professor of molecular microbiology and immunology at the Keck School of Medicine of USC.

“This is very different from developing new antibiotics. This is using our own immune system to fight against different superbugs.”

— Jun Yan, USC doctoral student

The experimental vaccine takes an entirely different approach: It gooses the body’s preexisting supply of pathogen-gobbling immune cells called macrophages, which engulf and digest bacteria, fungi and other bad actors. These activated fighters, found in all tissues, quickly neutralize incoming invaders which might otherwise multiply rapidly and overwhelm the body’s defenses.

“This is very different from developing new antibiotics,” said Jun Yan, a doctoral student at Keck School of Medicine and the study’s first author. “This is using our own immune system to fight against different superbugs, which is a different approach than everybody else.”

The vaccine is made up of just three ingredients, two of which are already used in FDA-approved vaccines. A third component is a tiny piece from the surface of a fungus commonly found on human skin.

MRSA vaccine works within 24 hours

Tested in two independent labs, the vaccine works within 24 hours and lasts for up to 28 days. In lab models, the number of pathogen-eating immune cells in the blood increased dramatically, and survival time of invasive blood and lung infections improved. Early data suggest that a second dose could extend the window to prevent infection.

To develop the vaccine, Spellberg, Luna, Yan and Travis Nielsen, who earned his PhD in the Keck School of Medicine’s biomedical and biological sciences program before going to medical school, formed a startup called ExBaq LLC.

ExBaq began talking with potential larger partners who might be willing to help develop the vaccine into clinical testing. AstraZeneca expressed interest in learning more about the vaccine, Spellberg said, and then agreed to test it in its own experimental infection models, confirming that it worked in those models too.

The next step is getting guidance from the FDA on the design of a clinical trial. The first such trial would be done in healthy volunteers to find the right dose of vaccine that is safe and triggers the same kind of immune response in people as seen in the mice.

Reference: Yan J, Nielsen TB, Lu P, et al. A protein-free vaccine stimulates innate immunity and protects against nosocomial pathogens. Sci Transl Med. 2023;15(716):eadf9556. doi: 10.1126/scitranslmed.adf9556

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