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.
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.
Stem cell transplants are quite expensive—in the $20,000 to $30,000 range— with some estimates as high as $350,000 to $800,000.
The transplants are also risky, with common complications being infection (often pneumonia), sepsis, bleeding, organ failure, and chronic graft vs. host disease, which happens when the donor cells attack the recipient’s tissue. Depending on the site, 25-40% of patients will die in the first year following transplant.
Both the “Berlin” and “London” patients received the transplant as part of their cancer therapy, not specifically for their HIV. But donors were chosen, in part, to have this CCR5 mutation, which likely confers immunity.
While these cases of long-term remission of HIV open new areas of research, another promising line of study has been closed. In December, Science and the Washington Post reported that fetal tissue research at NIH, which was looking for a cure for HIV, was abruptly halted.
HIVMA’s immediate past chair, Dr. Melanie Thompson, a leading HIV researcher and clinician, puts this HIV research development in perspective:
“In reality, we must focus our attention and our money on the half of people living with HIV in the US who are not in routine care and who do not have suppressed virus. These individuals are not benefiting from our scientific discoveries and may continue to transmit the virus to others because their virus is not undetectable. Likewise we must scale up PrEP and PEP.”
So while this new case of successful treatment of HIV with stem-cell replacement is exciting, it’s limitations of side effects and cost will make it unfeasible for most patients. Instead, we should be focusing now on other research avenues, education, and strong public health efforts to reduce transmission of HIV.