LONDON, England -- Researchers say a London man appears to be free of the AIDS virus after a stem cell transplant. It's the second such success since "Berlin patient" Timothy Ray Brown more than a decade ago.Such transplants are dangerous and have failed in other patients. The new findings were published online Monday by the journal Nature.The London patient has not been identified. He was diagnosed with HIV in 2003. He developed cancer and agreed to a stem cell transplant to treat the cancer in 2016.His doctors found a donor with a gene mutation that confers natural resistance to HIV.The transplant changed the London patient's immune system, giving him the donor's HIV resistance.