It's known that HIV enters the brain within eight days of infection, but less is known about whether HIV-infected brain cells can release HIV that can then infect other tissues.
This new work from Rush University Medical Center in Chicago found that certain types of brain cells can harbor HIV, which can then spread to immune cells that carry it elsewhere in the body -- even if HIV has been suppressed by antiretroviral therapy.
"Our study demonstrates that HIV in the brain is not trapped in the brain -- it can and does move back into peripheral organs through leukocyte trafficking," said study lead author Lena Al-Harthi, an immunology expert at Rush.
The study results could prove important in attempts to find cures for HIV, Al-Harthi said in a news release from the U.S. National Institute of Mental Health (NIMH).
In the study, the researchers transplanted HIV-infected or noninfected human astrocyte brain cells into the brains of immunodeficient mice.
The human brain contains billions of astrocytes, which perform a variety of tasks, from supporting communication between brain cells to maintaining the blood-brain barrier.
The researchers found that the transplanted HIV-infected astrocytes were able to spread the virus to CD4-positive T immune cells in the brain. These immune cells then migrated out of the brain and into the rest of the body, spreading the infection to organs such as the spleen and lymph nodes.
This occurred, although at lower levels, even when the mice received combination antiretroviral therapy, a standard treatment for HIV, according to the study.
"This study demonstrates the critical role of the brain as a reservoir of HIV that is capable of reinfecting the peripheral organs with the virus," said Jeymohan Joseph, an HIV expert at the NIMH.
"The findings suggest that in order to eradicate HIV from the body, cure strategies must address the role of the central nervous system," Joseph added.
However, the work is still in its early stages, and animal research is not necessarily replicated in humans.
The study was co-funded by the NIMH and the National Institute of Neurological Disorders and Stroke. The results were published June 11 in the journal PLOS Pathogens.