Vaccines Using Toxin-Absorbing Nanosponges

As vaccines against infectious diseases, nanoparticles with coatings that soak up unaltered bacterial protein toxins like a sponge could be more effective than heat-deactivated toxins, according to a report by Liangfang Zhang and coworkers at the University of California, San Diego (Nat. Nanotechnol. 2013, DOI: 10.1038/nnano.2013.254). Some bacterial toxins operate by embedding themselves in cell membranes, creating pores that leak cellular contents. Heating the toxins denatures them, thereby reducing their toxicity, but it also potentially reduces a vaccine’s effectiveness in stimulating the immune system to produce antibodies. Zhang’s team leveraged one bacterial toxin’s affinity for cell membranes to make a vaccine containing the unaltered toxin. The researchers coated plastic nanoparticles with red blood cell membranes embedded with α-hemolysin, a red-blood-cell-puncturing protein secreted by methicillin-resistant Staphylococcus aureus. Mice receiving the coated nanoparticles made more anti­bodies than mice receiving heat-treated α-hemolysin alone. Also, more mice receiving the nanoparticles survived direct injection of α-hemolysin. The nanoparticle membranes showed no sign of releasing the pore-forming toxins, which would be a problem in vaccines that use an unaltered toxin. The researchers say they could adapt the nanoparticles for toxins made by other bacteria.