Methicillin-resistant Staphylococcus aureus bacteria, commonly known as MRSA, pose a serious public health threat, causing more than 80,000 skin, lung, and blood infections and killing about 11,000 people annually in the United States . This microbe wreaks its devastation by secreting a toxin, alpha-hemolysin, that punches holes in the membrane of cells, essentially causing them to leak to death. Now, NIH-funded researchers from the University of California, San Diego, have created tiny sponges capable of trapping and binding MRSA’s toxin . When these toxin-laden sponges are injected into mice, they serve as a vaccine—that is, they stimulate the animal’s immune system in a way that protects them from the toxin’s deadly impact.
For those of you who want more details, here’s how this innovative approach works. Bioengineers wrap spherical polymers in the membrane of a red blood cell to create sponges that measure just 85 nanometers in diameter— about 1,000 times smaller than a human hair. The sponges are then exposed to the MRSA toxin in a lab dish and, after they bind the toxin, they are injected beneath the skin. Once in the body, they are taken up by immune cells called dendritic cells, which then trigger an immune response against the potentially lethal toxins. If they weren’t bound to the sponge, the toxin molecules would destroy the immune cell before it had a chance to fight back. The ultimate result is protection of that mouse (or eventually that human) from some future exposure to MRSA toxin.
This could be a promising new avenue to fighting bacterial infections without the use of antibiotics. Antibiotic resistance is an escalating public health problem worldwide because, as the drugs become ineffective, the bacteria spread faster and are more difficult and more expensive to treat. The researchers also suggest these nanosponges could be used to create vaccines against a range of other toxins—including those produced by other dangerous microbes, such as Escherichia coli, which can cause food poisoning, and Helicobacter pylori, the culprit responsible for stomach ulcers and stomach cancer.
 Antibiotic Resistant Threats in the United States, 2013. (CDC report)
 Nanoparticle-detained toxins for safe and effective vaccination. Hu CM, Fang RH, Luk BT, Zhang L. Nat Nanotechnol. 2013 Dec 1.
Zhang Research Group, Nanomaterials & Nanomedicine Laboratory, UCSD
NIH support: National Institute of Diabetes and Digestive and Kidney Diseases