 Right now, 37 million people worldwide are living with HIV. Only a few have ever been cured. The story of Timothy Brown has inspired scientists to develop new methods to try to cure HIV AIDS using stem cells. Here is his story. Timothy Brown was a 40-year-old HIV-positive man who was diagnosed with a fatal blood cancer, acute myeloid leukemia. In order to treat his deadly cancer, he received a bone marrow transplant from a healthy donor, but with a game-changing twist. The donor was chosen from a tiny fraction of people, about 1% of Northern Europeans, who carry a rare genetic mutation that makes them immune to the most common type of HIV. HIV is a virus that infects cells of a person's immune system, killing them. Because their immune system is compromised, the person is prone to dangerous infections, which lead to the development of AIDS. All of the immune cells infected by the HIV virus come from the body's blood-forming stem cells. Timothy Brown's infected blood cells were removed and replaced with new blood stem cells immune to HIV. Eventually, Timothy's entire immune system rebooted and became HIV-resistant, thereby curing his HIV. Unfortunately, not every HIV-positive person is as lucky as Timothy Brown. In fact, these treatments can be very dangerous, so blood stem cell transplants are reserved for cancers that are unresponsive to treatment. In addition, for the transplant to be successful, the donor and patient must be as closely matched as possible. Finding the right bone marrow donor that also has the rare genetic mutation that triggers HIV immunity is very difficult. However, there is hope. Timothy Brown's story has taught us that it is possible to cure HIV by replacing a patient's damaged and HIV-infected immune system cells with HIV-resistant ones that come from HIV-resistant blood stem cells. What if, instead of waiting for the perfect donor to cure someone's HIV, we figured out a way to make the patient's own immune system HIV-resistant by making their own blood stem cells HIV-resistant? A number of research groups are working on this question in novel and exciting ways. Thanks to funding from California's Proposition 71, three groups are making significant contributions. A team led by Dr. Joan Zea at City of Hope in collaboration with the University of Southern California and Sangamo Biosciences has developed a method to take blood stem cells from an HIV-positive patient, use gene therapy to make those cells HIV-resistant, and then return the modified blood stem cells to the patient. Another group led by Dr. Joseph Anderson at University of California Davis is taking a similar approach. They are isolating blood stem cells from an HIV-positive person, modifying the cells to become resistant to HIV by blocking the ability of HIV to infect cells at several stages and then reintroducing only the engineered stem cells after a purification step. A study sponsored by Cal Immune Inc. is genetically modifying both immune cells and stem cells to be HIV-resistant and transplanting them back into the patient. Once the patient receives those modified HIV-resistant blood stem cells, they could begin to rebuild an entirely new immune system that would have the potential to block HIV infection, thereby offering an approach to both cure and prevent HIV. The City of Hope, Cal Immune Inc. and UC Davis teams have been able to make animals immune systems resistant to HIV infection. Human clinical trials are underway to test this therapy in HIV-positive people. Importantly, if this approach can work in AIDS, it can also be applied to certain immune disorders, cancers, and more. Only with continued support for biomedical research can we realize the full potential of stem cell research. But there is another crucial part of the story. These tremendous milestones of progress wouldn't have been possible without the hard work, advocacy, and support of the HIV-AIDS patient advocate community. HIV advocates have been driving policy in support of biomedical research for over 20 years and continue to be an incredibly strong force today. As scientists and patient advocates build on the progress that Proposition 71 funding has enabled, we must keep the momentum going, understanding that there is still much work to be done. We must remember that human trials will celebrate successes, but barriers will surface along with complications and challenges, so patience and understanding of the scientific discovery process are essential.