A second patient appears to have been “cured” of HIV following a stem cell transplant procedure, which replaces unhealthy, infected cells, with healthy blood cell precursors. The first successful stem cell transplant occurred in the “Berlin patient,” Timothy Ray Brown, in 2008 and, ten years later, he is still free of HIV.
The current unidentified patient has been free of HIV for eighteen months now, a remarkable achievement, though too early to really claim as a cure.
HIV treatment has been stymied because reservoirs of infected cells have remained latent, or “in hiding,” in the bone marrow of patients, and can later reactivate. Treatment with anti-virals can suppress the virus in a person’s blood, but does not eradicate it in these reservoirs. This is why patients with HIV are thought to need life-long treatment.
HIV infected T-cell
How susceptible an individual is to HIV infection is in part dependent on viral receptors on the surface of their own white blood cells. People with a specific mutation (called Δ32) on the CCR5 gene develop defective receptors, so the HIV virus can’t enter the cell. The person is thus very unlikely to become infected with HIV.
The latest transplant was led by Dr. Ravindra Gupta, of the University of Cambridge, UK. Both transplants relied on selecting donors who had this mutation in their genes, so were resistant to HIV. When the donor’s stem cells were successfully transplanted, it replaced the patients’ own cells, conferring this HIV-resistance. Some viruses enter by other receptors, so focusing only on CCR5 receptors may not work long-term.
Stem cell transplants are typically used for patients with leukemia or specific cancers. They require extensive radiation and chemotherapy first—both are expensive and dangerous treatments. Stem cell transplants are also curative for sickle cell disease, but are not widely used because of these issues.