Progression Of SIV Infection In Monkeys Points To Differences Between Human And Simian Forms Of AIDS

The research highlights differences between the simian and human forms of AIDS and how the progression of the disease in monkeys takes a different course. Without treatment, humans infected with HIV -- unlike monkeys infected with SIV -- can experience a sudden, acute loss of T cells, which is considered to be sufficient to predict progression to the disease's last stages: final collapse of the immune system and death.

The team, led by Ivona V. Pandrea and Cristian Apetrei of Tulane University, states that although a severe acute depletion of T cells (white blood cells that provide continuing immunity to infection) is considered to trigger progression to full-blown AIDS in humans, some non-human primates infected with simian immunodeficiency virus do not develop AIDS after such a depletion. African green monkeys infected with SIV, for example, were found to recover even after a period of severe T cell depletion.

Two companion papers in the Journal of Immunology by researchers from the University of Pennsylvania and Southwestern University of Dallas came to the same conclusions in their studies of sooty mangabeys.

Another major question raised by the study is why monkeys with SIV, unlike HIV-positive humans, are generally resistant to progression to AIDS after infection with the virus.

The answer, the authors propose, is that thousands of years of host/virus co-adaptation has enabled monkeys, the natural hosts of SIV, to effectively limit T cell immune activation and apoptosis, a mechanism that leads to progression of the disease. By contrast, humans, who were introduced to the virus relatively recently, have not had the opportunity to develop such protective adaptations.

The authors also suggested that approaches to control immune system activation and resultant cell death should be considered for use in addition to currently available therapies to slow progression of the disease in HIV-infected individuals.

Editor's Note: This story has been modified from its original version, which can be accessed here: http://web.archive.org/web/*/http://www.sciencedaily.com/releases/2007/09/070923193631.htm (via the Internet Archive's Wayback Machine). This version clarifies that the research described in the story examined the differences in how the simian and human forms of AIDS progress. The purpose of the story was NOT meant to suggest that the sudden loss of T cells is not the trigger of AIDS in humans, nor was there any intent to support the erroneous belief that HIV somehow does not cause AIDS. We regret any confusion that this may have caused. Links to the abstracts of the journal papers referred to above are provided below.