German hematologist Gero Hütter is making a claim very rare in AIDS research: that “he has cured an HIV infection,” said Eben Harrell in Time online. Two years ago, Hütter treated leukemia in a U.S. AIDS patient, now 42, by transplanting bone marrow from a donor with a rare genetic mutation that locks HIV out of cells. Now, even though the patient hasn’t taken antiretrovirals since the transplant, he “shows no signs of carrying the virus.”

AIDS experts “have reacted cautiously” to Hütter’s claims, said Jeremy Laurance in Britain’s The Independent. The HIV virus is “adept at hiding in the body,” and even if the man really was cured of AIDS, bone marrow transplants are “too gruelling and expensive to be adopted as a treatment for HIV.”

There are good reasons for some skepticism, said Eliza Strickland in Discover online, and Hütter’s accomplishment “shouldn’t be taken as a sign that a cure for the 33 million people living with AIDS is around the corner.” But it is still an exciting feat, and “a proof of concept” that gene therapy may one day allow all “AIDS patients to lock out the virus.”