Researchers at the
Institute of Human Virology, University of Maryland, US have identified a
new behaviour for the human macrophage that provides new explanations
for several features of HIV biology.
This was contained in a statement signed and made available to the News Agency of Nigeria by the Communications Manager, Institute of Human Virology of Nigeria, Mr Dennis Mordi on Monday.
Macrophages are white blood cells within tissues.
It stated that the
discovery explains how the virus persists within the body, how inactive
infected CD4+ T-cells arise and how the infection leads to depletion of
CD4+ T-cells.
CD4+cells are specialised
cells that are a part of the immune system, while the T-cell is a type
of blood cell that protects the body from infection.
According to the statement,
the research team found that the macrophages cultured from human blood
can function as “nurse cells” and in this capacity, generate and release
newly formed cells.
“The new cells released
include a previously unknown small cell, termed “self-renewing
monocytoid cell” that is highly susceptible to infection with HIV.
“This small cell can develop into another nurse macrophage that can, in turn, produce another small cell.
“This nurse
macrophage/small cell developmental cycle can continue in culture for
several generations, even during continuous production of HIV.
“Current anti-HIV drugs cannot inhibit HIV maintained through this process, because they act to prevent new infection. ’’
It said the researchers
emphasised that, although working with HIV led them to recognise nurse
macrophage behaviour all of the phenomena observed could be seen in
uninfected, as well as HIV-infected macrophage cultures.
“Amazingly, nurse
macrophages can also produce CD4+ T-cells, which are released as resting
cells. These cells are a specific subtype of CD4+ T-cells, the subtype
preferentially targeted by HIV.’’
According to the report the
researchers observed a dramatic decline in T-cell production in
HIV-infected macrophage cultures, as well as release of resting CD4+
T-cells that contained HIV DNA, but were not producing the virus.
It said that the findings
suggested that nurse macrophages might represent a source of latently
infected CD4+ T-cells, and the compromise of nurse macrophage production
of CD4+ T-cells, brought about by HIV infection, might contribute to
the CD4+ T-cell decline that characterises AIDS.
Dr. Suzanne Gartner, the
leader of the Institute’s stem cell research team, noted, “Thus far, the
experiments have been performed using macrophages obtained from blood,
and then cultured in the laboratory.
“We are now trying to determine if this phenomenon is operational in vivo – within the human body.”
Dr. Robert Gallo, Director of the Institute
of Human Virology adds, “The concept that a cell can be produced within
another cell, a mother cell, is new and thought-provoking (at least in
human biology) and it makes sense that a virus would exploit this
process as a survival strategy.’’
