Microgel polymer beads may provide general vehicle for vaccines, gene therapy.

2003 MAY 21 - (NewsRx.com & NewsRx.net) -- A simple method of shuttling proteins into cells via microscopic polymer beads shows promise as a general way of carrying vaccines or bits of DNA for gene therapy, according to chemists at the University of California, Berkeley, and Lawrence Berkeley National Laboratory.

The polymer beads are imbedded with a protein - a vaccine antigen, for example - and made large enough to attract the attention of the immune system's scavenger cells, which engulf them and try to digest them with acid.

Professor of chemistry Jean M. Frechet, with postdoctoral fellow Niren Murthy and their colleagues, designed a polymer that falls apart in acid to form thousands of little molecules that swell and explode the cell's digestive chamber before the acids have a chance to degrade the antigens. The technique avoids a big problem of similar techniques: the cell's stomach acids often destroy the protein antigens before they can be used for display on the cell surface. Without such display, the immune system cannot detect the presence of the foreign protein.

Tests so far have been conducted only in cultured cells, but the results were impressive enough to warrant test injections in mice, which are currently under way.

Frechet, who reported the results in April 21, 2003, in the early online edition of the Proceedings of the National Academy of Sciences, said the technique skirts the disadvantages of today's injectable vaccines, which employ deactivated viruses to ferry antigens into the cell interior. The antigens stimulate an immune attack against an invading organism or a cancer.

"Deactivated viruses are not always so deactivated, so it is not clear whether viruses can always be turned into a vaccine," said Frechet. "We've developed a general delivery system that can be adapted to many different proteins. What's good about it is, it's simple."

Frechet is head of materials synthesis in the materials science division at Lawrence Berkeley National Laboratory and director of the Organic and Macromolecular Facility at its Molecular Foundry.