Viral protein could help liver therapy. (Biomedicine).

Researchers experimenting with a protein from hepatitis B virus have developed a new technique for delivering therapeutic genes to the liver while minimizing the accidental introduction of genes to other tissues.

The ideal delivery system for a gene therapy would target only those organs or tissues that need genetic repairs. Live viruses that are altered to carry human genes meet that criterion, but they can trigger dangerous immune responses and cause other problems. Other delivery vectors tend to usher genes to tissues other than the intended ones, a flaw that can lead to side effects.

Shun'ichi Kuroda of Osaka University in Japan and his colleagues suggest a hybrid vehicle: hollow globules of fat covered with a protein isolated from hepatitis B virus. These so-called L particles selectively target liver cells, just as hepatitis B virus does, but are less likely than an intact virus to get out of hand, the researchers say.

Using L particles, the researchers introduced a test gene into clusters of human liver cells growing in laboratory dishes and into mice that had received injections of cancerous human liver cells. In both sets of experiments, the viral protein helped guide the particles to targeted cells, the researchers report in an upcoming Nature Biotechnology.

L particles are big enough to accommodate even relatively large medicinal parcels, which could include some conventional drug molecules in addition to therapeutic genes, the researchers note. Furthermore, they suggest, the particles could be engineered to have different surface proteins that would target organs and tissues other than the liver.--B.H.