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.’’