Research presented at last week's ASM Biodefense and Emerging Disease Research Meeting revealed that a biodegradable polymer in a microsphere formulation could be used to develop time-released vaccines, thus reducing the need for vaccine booster shots, as well as stimulate an immune response that traditional vaccines do not. "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," said Jenny Wilson-Welder, a lead researcher on the study conducted at Iowa State University.
The polymer, called polyandydride, is already being used as a delivery system for a brain cancer drug designed to inhibit tumor growth but this is the first time its application in vaccines has been shown. "It's like an everlasting gobstopper or a bar of soap. It wears away slowly over time, delivering its payload," says Wilson-Welder.
Initially intended to find a controlled-release drug delivery mechanism that would eliminate the need for booster vaccinations, the study found that polyanhydride microspheres not only achieved this, but also enhanced a 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.
According to Wilson-Welder, these research findings could lead to the development of single-dose vaccines for diseases that currently require booster innoculations in order to be most effective, such as tetanus, whooping cough and chicken pox. "The slow release mechanism of the polymers means that vaccines that currently require multiple doses might only need a single dose in the future," she said.
In addition, the finding that vaccine adjuvants can elicit a CMI provides hope for vaccines against intracellular diseases that there are currently no effective vaccines for, like malaria, tuberculosis and even AIDS, said Wilson-Welder.
"If we understand how an adjuvant activates the dendritic cells, we can start tailoring our vaccines to induce a better cellular response. If we can tailor the immune response, it holds greater promise for vaccines that we do not currently have."