MIT engineers have designed a new type of nanoparticle that could safely and effectively deliver vaccines for diseases such as HIV and malaria.
The new particles consist of concentric fatty spheres that can carry synthetic versions of proteins normally produced by viruses. These synthetic particles elicit a strong immune response -- comparable to that produced by live virus vaccines -- but should be much safer, says Darrell Irvine, corresponding author of the paper and an associate professor of materials science and engineering and biological engineering.
Such particles could help scientists develop vaccines against cancer as well as infectious diseases. In collaboration with scientists at the Walter Reed Army Institute of Research, Irvine and his students are now testing the nanoparticles' ability to deliver an experimental malaria vaccine in mice.
Previously, rsearch had been done working on synthetic vaccines for HIV and other viral infections such as hepatitis B, vaccines that would not have the potential risks of using a live, attenuated virus. However, these experimental vaccines, while safer, do not elicit a very strong T cell response. Recently, scientists have tried encasing the vaccines in fatty droplets called liposomes, which could help promote T cell responses by packaging the protein in a virus-like particle. However, these liposomes have poor stability in blood and body fluids.
Irvine, who is a member of MIT's David H. Koch Institute for Integrative Cancer Research, decided to build on the liposome approach by packaging many of the droplets together in concentric spheres. Once the liposomes are fused together, adjacent liposome walls are chemically "stapled" to each other, making the structure more stable and less likely to break down too quickly following injection. However, once the nanoparticles are absorbed by a cell, they degrade quickly, releasing the vaccine and provoking a T cell response.
In tests with mice, Irvine and his colleagues used the nanoparticles to deliver a protein called ovalbumin, an egg-white protein commonly used in immunology studies because biochemical tools are available to track the immune response to this molecule. They found that three immunizations of low doses of the vaccine produced a strong T cell response -- after immunization, up to 30 percent of all killer T cells in the mice were specific to the vaccine protein.
That is one of the strongest T cell responses generated by a protein vaccine, and comparable to strong viral vaccines, but without the safety concerns of live viruses, says Irvine. Importantly, the particles also elicit a strong antibody response.
If this technique could be manipulated to work in humans, there would be potential for vaccines to viruses such as HIV and HBV, circumventing the risks present in live attenuated vaccines.
Full Article: http://www.sciencedaily.com/releases/2011/02/110222162318.htm
-Catalina Angel
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