Smoking might be dangeous for human health, but tobacco plants are not, claim Japanese scientists who have used the gene genie to get some health benefits from these plants. Tobacco plants could soon become a cheap source of a protein that can detect hepatitis B in donated blood. Shinya Tsuda of the Plant Biotechnology Institute in Ibaraki, Japan, has genetically engineered tobacco plants to produce a viral protein, the hepatitis B virus core antigen. Blood tainted with the virus contains antibodies to this antigen. In a test, the antigen would bind to and detect antibodies to hepatitis B, showing that the blood was contaminated, Tsuda and colleagues reported recently.