Nanoparticle Adjuvant May Enhance Vaccine Development Programs

Many vaccines require the action of an adjuvant to boost the body's immune response, and nanotechnology has produced a promising new one that has the potential to serve as a universal protein-based vaccine carrier.

Investigators from Oregon State University (Corvallis, USA) created 200-nm nanospheres from emulsions of lecithin, a common food additive. Protein antigens were then covalently bound to the lecithin nanoparticles. In the current study, mice were injected with model vaccines prepared from either bovine serum albumin (BSA) or Bacillus anthracis protective antigen (PA) bound to lecithin nanoparticles. Control groups were vaccinated with these antigens and either incomplete Freund's adjuvant or aluminum hydroxide.

Results published in the September 1, 2009, online edition of the Journal of Controlled Release revealed that animals immunized with the BSA-conjugated nanoparticles developed strong anti-BSA antibody responses comparable to that induced by BSA injected with incomplete Freund's adjuvant and 6.5-fold stronger than that induced by BSA adsorbed onto aluminum hydroxide, one of the few adjuvants approved for use in humans. Immunization of mice with the PA-conjugated nanoparticles elicited a quick, strong, and durable anti-PA antibody response that afforded protection of the mice against a lethal dose of anthrax lethal toxin challenge.

"Our early studies with laboratory animals seem to suggest that a vaccine based on the lecithin nanoparticle adjuvant would not only be more effective, but be tolerated by the body more readily than one using alum," said senior author Dr. Zhengrong Cui, assistant professor of pharmaceutics at Oregon State University. "Lecithin is very nontoxic, it is one of many compounds "generally recognized as safe" by the FDA [U.S. Food and Drug Administration], and at the injection site we saw none of the nodules and tissue hardening you sometimes see with vaccines that use alum. In many cases, to make progress with vaccine development we need new adjuvants," said Dr. Cui. "The material has to be safe, and lecithin is a common food product that is already widely used in pharmaceuticals. This new form of using lecithin nanoparticles as an adjuvant is promising and could become very important."

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