There was mixed news last week for companies working on pig-derived organs for transplant. The good news is the technology is working. The bad news is that there is evidence that pig retroviruses can be active across species, throwing up a question mark on the long term future of xenotransplantation research.

Last week, successful pig cloning experiments were reported by two groups, PPL Therapeutics plc (LSE:PTH, Roslin, U.K.) and the Japanese National Institute of Animal Industry (Tsukuba Norin Danchi, Japan), which published their results in