CD4 T cells have been called the "general" in the immune cell army because they direct other immune cells, like killer T cells, to attack HIV-1 and other foreign substances. These important immune cells are targeted and infected by HIV-1 and can drop to dangerously low levels in AIDS patients when the virus continues to replicate, unchecked.
Dr. Rinaldo's research team was the first to find that triple therapy regimen of a protease inhibitor (indinavir) with two nucleoside reverse transcriptase inhibitors (zidovudine and lamivudine) allowed a group of killer T cells, sometimes called memory CD8 T cells, to increase dramatically two to three months after initiating treatment in five study participants. These CD8 T cell levels remained high for about a year. The Pitt study also was the first to show a drastic drop in the numbers after a year. Despite the small amount of killer T cells, levels of freely circulating virus in these patients remained so low they weren't detected with a commonly used test known as viral load.
"We're not quite sure why we see the rise in memory CD8 T cells," commented Dr. Rinaldo, who described a possible inhibitory effect on the killer T cells imposed by high viral activity. "But, we think that when the virus is suppressed, these immune cells are able to grow freely, without any inhibition. This may help to explain the immediate rise in the number of memory CD8 T cells.
"Also, we aren't certain what causes the late drop in numbers of memory
killer T cells after one year of triple therapy, but it makes sense that these
cells decline in numbers. When viral levels ar
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Contact: Amy Kemp
kempam@a1.isd.upmc.edu
412-624-2607
University of Pittsburgh Medical Center
29-Jun-1998