Scientists have known for a while that HIV hides in the body, undetected by the immune system and unaffected by antiretroviral drugs, but where specifically? Researchers from the University of Michigan have narrowed it down to specific cells in the bone marrow, highlighting a new opportunity for an anti-HIV drug that could finally get rid of the virus completely.
HIV is hard to get rid of entirely. Despite the latest anti-retroviral drug technologies, HIV hides in the body, waiting to “pounce” once the drugs stop to cause an infection, which can lead to AIDS. The way HIV “lurks” is similar to the way the varicella virus, which causes chickenpox, hides out in long-living nerve cells and causes shingles later in life. Current drugs keep HIV at bay, preventing AIDS, but they don’t completely rid the body of the virus.
"Looking for the cells that harbor functional HIV is like searching for a needle in a haystack,” explained research leader Kathleen Collins, MD, PhD. “Our new results expand our understanding of the type of cells that can do it.”
Thanks to several long-term HIV patients who donated bone marrow samples, Collins and her team were able to observe HIV hiding in bone marrow cells, and they saw that HIV was present in many different cell types. Cells harboring the virus divide, passing HIV genetic material to future generations of cells.
They found that HIV hides in hematopoietic progenitor cells (HPCs), which replace blood cells as they get older and die, “blood cells in waiting.” Here, HIV hijacks the HPC’s cellular machinery so the cell starts cranking out viral proteins. To do so, HIV attaches to a CD4 receptor on the surface of HPCs. Two HIV subtypes are capable of binding CD4, those utilizing CXCR4 and CCR5 receptors.
HPCs can live for years, making them a smart choice for HIV to set up shop. However, identifying HPCs as HIV hideouts shows researchers exactly what cell type to target. Collins’s team is doing just that - researching new treatment options that can target HPCs specifically, leaving other bone marrow cells unharmed to minimize collateral damage.
"Today's medications have side effects, as well as financial costs,” Collins pointed out. “To get to the next step, we need to target the types of cells that form a latent infection, including these progenitor cells."
According to the Centers for Disease Control and Prevention, over one million people in the United States are living with HIV, and 1 in 7 of them are completely unaware.
The present study was published in the journal PLOS Pathogens.