HIV Reservoir in Bone Marrow

HIV can hide inside multipotent hematopoietic progenitor cells (HPCs) in the bone marrow, presenting a challenge for efforts at eradication, according to a study in the March 7, 2010, online edition of Nature Medicine. HPCs are a type of stem cell that gives rise to multiple types of blood cells.

Kathleen Collins and colleagues from the University of Michigan at Ann Arbor looked at CD34+ HPCs in bone marrow samples from 15 HIV positive individuals. They found HIV genetic material in HPCs from all six participants with high plasma viral load, and from four of nine individuals who had undetectable plasma HIV RNA on ART for at least six months.

When the researchers added wild-type HIV to laboratory cultures of HPCs from HIV negative donors, the virus infected and killed most HPCs, but some containing the latent provirus, or viral genome, went dormant. When they used differentiation factors to force the HPCs to start developing into blood cells, the viral genome was activated and began producing new virus particles.

This research helps solve the mystery of where -- besides latent CD4 T-cells -- HIV is able to hide in the body for prolonged periods. "This finding is important because it helps explain why it's hard to cure the disease," said Collins. "Ultimately, to cure this disease, we're going to have to develop specific strategies aimed at targeting these latently infected cells."

Liz Highleyman ( is a freelance medical writer based in San Francisco.