Scientists have developed a new vaccination method that may improve vaccination efficacy. The results of this study were reported in the journal Nature Nanotechnology on Dec. 1, 2013. Unlike traditional inactivated vaccines where the inactivation process modifies a toxin’s structure, this new method uses nanotechnology and maintains a toxin’s structure.
Vaccination saves lives, lowers medical costs and prevents serious illness and disabilities. Vaccination prevents diseases such as meningitis, shingles, measles, chicken pox, tetanus, and whooping cough. For every $1 invested in just one Diphtheria, Tetanus, Pertussis (DTaP) vaccination, medical costs in Connecticut are reduced by $6.21.
Inactivating agents are used during the manufacture of some vaccines to inactivate viruses or detoxify bacterial toxins (so that they don’t cause disease). One of the main problems with inactivated vaccines is that inactivating agents decrease the neutralizing antibody response in the body, which reduces the effectiveness of the vaccine.
In this recent study, scientists engineered a method to preserve the toxin structure of staphylococcal alpha-haemolysin (staph-aH). Staph-aH is the toxin in the antibiotic-resistant Staphylococcus aureus bacteria. The new method uses a nanoparticle to capture this toxin. The nanoparticles are bio-compatible particles made of a polymer core wrapped in a red-blood-cell membrane. Each nanoparticle’s red-blood-cell membrane seizes and detains the staph-aH without compromising the toxin’s structural integrity. This method avoids any heating or chemical processing. Heating or chemical processing damages the structure of the toxin. This structure is what the immune cell recognizes, and builds its antibodies against.
“The more you heat it, the safer the toxin is, but the more you heat it, the more you damage the structure of the protein ... this structure is what the immune cell recognizes, and builds its antibodies against,” said Liangfang Zhang, PhD, senior author of this study.
To determine the safety and efficacy of this nanoparticle-based vaccine, it was injected into the skin of mice and results were compared with injection with control vaccines containing heat-inactivated toxins. The nanoparticle-based vaccine was found to induce higher concentrations of antibodies than the control vaccine. They also produced antibodies that are more able to neutralize the toxin when exposed to it. The survival rate of mice vaccinated with the control was 90% compared with a survival rate of 100% for those injected with the nanoparticle-based vaccine.
Toxoid vaccines protect against a toxin or set of toxins, rather than the organism that produces the toxin(s). As the problem of antibiotic resistance worsens, toxoid vaccines offer a promising approach to fight infections without relying on antibiotics. “With our toxoid vaccine, we don’t have to worry about antibiotic resistance. We directly target the alpha-haemolysin toxin,” said Dr. Zhang.
In summary, these toxin-studded nanoparticles worked well as vaccines, triggering neutralizing antibodies, and fighting off otherwise lethal doses of the toxin in mice. Currently, there is no way to deliver a native toxin to the immune cells without damaging the cells. This technology may be the answer. This new vaccination method opens fresh possibilities in the preparation of vaccines against the many virulence factors that threaten public health.
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