New Delivery System Uses Biodegradable Microspheres

"Current vaccines are good at producing antibodies that block entry into the cell. In the case of some diseases, such as malaria or tuberculosis, antibody vaccines just aren't effective," says Jenny Wilson-Welder from Iowa State University, a lead researcher on the study.

Wilson-Welder and her colleagues initially began their research looking for a way to eliminate the need for booster vaccinations, by developing a vaccine delivery system that released the vaccine into the system slowly over time. They chose a biodegradable polymer, called polyandydride, in a microsphere formulation. This polymer was already being used as a delivery system for a brain cancer drug designed to inhibit tumour growth.

The researchers vaccinated mice with microspheres loaded with ovalbumin, a protein from chicken eggs, and measured immune response. While mice exhibited the expected antibody response, the researchers also noticed something unexpected. The vaccine enhanced another type of immune response known as cellular-mediated immunity (CMI). CMI allows the immune system to identify, target and kill cells that have already become infected, something antibodies can not do.

To determine the cause of this effect, Wilson-Welder and her colleagues next incubated human dendritic cells in the presence of polyanhydride microspheres (without ovalbumin). Dendritic cells are responsible for initiating CMIs. "We observed that the polymer microspheres were activating dendritic cells," says Wilson-Welder.

The implications of these findings are two-fold, says Wilson-Welder. First, they have shown that polyanhydride microspheres can be used to deliver time-released vaccines. This could lead to the development of single-dose vaccines for diseases that currently require booster innoculations to be most effective, such as tetanus, whooping cough and chicken pox.; Source: American Society for Microbiology