A Los Alamos National Laboratory mathematical model has helped an international research team understand for the first time the number of offspring produced by a single Simian Immunodeficiency Virus (SIV), the first-cousin of the virus that causes AIDS in humans. The research indicates the immunodeficiency virus produces ten to a hundred times more progeny than previously believed.
The research-by Los Alamos researcher Alan Perelson and colleagues from Aaron Diamond AIDS Research Center, the National Institutes of Health and the Chinese Academy of Medical Sciences-appears in a paper published this week in the Proceedings of the National Academy of Sciences.
For the research, Perelson and his colleagues used an engineered strain of the SIV virus containing a defective protein that renders the virus unable to survive beyond a single generation. SIV is the viral counterpart of the Human Immunodeficiency Virus (HIV), the virus that causes AIDS.
The team infected blood cells from Rhesus Macaque monkeys with the single-cycle SIV strain. Perelson then used a simple mathematical model developed at Los Alamos to accurately count the next generation of virus bursting from the infected blood cells.
Perelson found that on average, a single virus produces about 50,000 offspring from a single infected cell.
"Previously within the field of HIV research, estimates of viral burst ranged from a couple hundred virus particles to several thousand," Perelson said. "Our research showed the viral burst size is one to two orders of magnitude greater than what was previously thought."
Earlier attempts to quantify HIV viral burst relied on using tissue samples and then attempting to physically count parts of HIV chromosomes or by taking a blood sample and extrapolating a burst count for the entire body. This research provides the first highly accurate burst count for SIV and provides critical insight into the process of viral production and its interplay with an infected host.
Typically, when SIV or HIV infects its host, the virus invades a type of immune-system cell called a "T-cell" found within the blood of the host. The virus uses components of the invaded cell to reproduce. The reproduction process kills the T-cell, which normally is used by the body to fight infection. Each subsequent generation of virus whittles away more of the body's T-cells until, in later stages of SIV or HIV infection, so many T-cells have been killed by the virus that the host is unable to fight secondary infections. The host usually dies from complications of secondary infections.
With a more realistic understanding of SIV and HIV burst size, AIDS researchers and the medical community may now focus on strategies to reduce the number of virus progeny and possibly limit or prevent continued infection.
Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and the Washington Division of URS for the Department of Energy's National Nuclear Security Administration.
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