Immunosuppressant drugs used to prevent rejection of transplanted organs may combat the HIV reservoir, the presence of which thwarts attempts to cure HIV with standard antiretrovirals (ARVs). Researchers studied how the transplant drug sirolimus (rapamycin) affected the disease state of 91 HIV-positive transplantees, who were followed for just over three years. The investigators found that those who took the drug had lower levels of HIV DNA in their blood, indicating a reduction of the reservoir. They theorized that the drug may attack the reservoir from various fronts: reducing the capacity of the long-lived memory CD4 cells, which make up much of the reservoir, to make new copies of themselves; enhancing HIV-specific CD8 cells’ ability to attack the virus and help clear the reservoir; and reducing CD4 activation, thus slowing the spread of HIV from infected cells.