An HIV-positive man in Britain has become the second known adult worldwide to be cleared of the AIDS virus after he received a bone marrow transplant from an HIV-resistant donor, his doctors said. Almost three years after he received bone marrow stem cells from a donor with a rare genetic mutation that resists HIV infection – and more than 18 months after he came off antiretroviral drugs – highly sensitive tests still show no trace of the man’s previous HIV infection. “There is no virus there that we can measure. We can’t detect anything,” said Ravindra Gupta, a professor and HIV biologist who co-led a team of doctors treating the man.