Over the past 3 decades, researchers have made phenomenal gains in the fight against HIV. The deadly virus attacks the T-lymphocyte cell, specifically CD4, then causes the immune fighting cell to churn out more HIV virus’. CD4 T cells send signals to the body’s immune system when something foreign is in its path, recruiting more immune cells to the scene. When HIV has used the CD4 T lymphocyte cell to replicate itself, the latter dies. As CD4 cells drop, so do immune defenses. HIV could lead to AIDS, Acquired ImmunoDeficiency Syndrome, giving rise to infections that healthy immune systems could normally withstand, but an immuno-compromised patient could not.
Anti-HIV drugs have targeted how the virus attacks the T-cells, and specifically how its DNA enters the T cells to cause its parasitic replication; however, millions of HIV individuals have yet to be “cured”, even if their viral load remains low or undetectable. Many cases have been reported of an individual with undetectable HIV coming OUT of remission, with reactivation of the virus. If T-lymphocytes have short life spans, how does HIV persist? The assumption exists that HIV hides out in a reservoir. But where?
Researchers from the University of North Carolina discovered that the HIV virus can live in macrophages. Macrophages are derived from monocytes, a type of white blood cell that finds, engulfs, and destroys pathogens as well as debris and dead cells in the body. I picture them to be Pac-Men that can gobble up unwanted microscopic particles, including bacteria, and will “digest” the substances they engulf with enzymes. Moreover macrophages alert the immune system of their work and that something foreign is in the body, just as CD4 T cells do. However, one major difference is that the macrophage can live for months, even years. This could make a cozy home for an HIV virus that hasn’t been destroyed by the macrophage’s enzymes.
According to Dr. Jenna Honeycutt, lead author and postdoctoral research associate in the UNC Division of Infectious Diseases, “The fact that HIV-infected macrophages can persist means that any possible therapeutic intervention to eradicate HIV might have to target two very different types of cells.” Their findings were published this week in Nature Medicine.
In January, Professor Ravindra Gupta, from the University of College London, and colleagues also found HIV to infect macrophages. HIV replication appears to be active in the brain, where the virus targets macrophages.
With these new developments, researchers want to now investigate where infected macrophages hide and hopefully find new therapeutic interventions that would limit HIV’s entry into this ubiquitous immune cell.
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Daliah Wachs, MD, FAAFP is a Board Certified Family Physician. The Dr. Daliah Show , is nationally syndicated M-F from 11:00am-2:00pm and Saturday from Noon-1:00pm (Central) at GCN.