Question: How does a stem cell transplant work and how did it cure a man with HIV of a transplant?

Srinath Kasturirangan answered on 13 Mar 2019:

Hey Gareth! I notice you want to be a Biomedical Engineer!! Welcome to my world!! This is a great question, glad to see you have been following the news, this one has been making waves recently. So this cancer patient also happens to be HIV positive. Stem cell transplants are used to replace bone marrow that has been destroyed by cancer or destroyed by the chemo and/or radiation used to treat the cancer. First high doses of chemo is used to kill cancer cells. But such high doses can also kill all the stem cells and cause the bone marrow to completely stop making blood cells, which we need to live. This is where stem cell transplants come in. The transplanted stem cells replace the body’s stem cells after the bone marrow and its stem cells have been destroyed by treatment. In this case, however, there was a second goal: to cure the patient’s HIV. The stem cells came from a donor who carried a rare gene mutation that confers resistance to HIV — and doctors were banking on that benefit being transferred to their patient. In this case it did and the patient has been HIV free for over 13 months! Cool!