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Monday, February 13, 2012

How Protein Protect Cells From HIV

HIV structure
HIV Structure
Basically, people have a good immune system. Damage to the immune system by HIV (Human immunodeficiency virus) that does not mean our bodies are not able to make improvements to the immune system. A recent discovery by researchers at NYU Langone Medical Center and colleagues showed that the immune system tries to stop the spread of HIV.

HIV is a lentivirus that causes AIDS (acquired immunodeficiency syndrome), a condition of a person where his immune condition continued to decline. The decline immune can provoke other diseases are present in a human.

“A lot of research on viruses, especially HIV, is aimed at trying to understand what the body’s mechanisms of resistance are and then to understand how the virus has gotten around these mechanisms,” said co-lead investigator Nathaniel R. Landau, PhD, a professor of microbiology at the Joan and Joel Smilow Research Center at NYU School of Medicine.

The research focused on a protein called SAMHD1. Recent studies have found that immune cells, called dendritic cells, containing the protein are resistant to infection by HIV. Since the discovery, scientists have sought to understand how SAMHD1 works to protect these cells, with hopes that science might find a way to synthetically apply that protection to other cells. Dr. Landau and his team are now able to provide an answer:
When a virus, like HIV, infects a cell, it hijacks the cell’s molecular material to replicate. That molecular material is in the form of deoxynucleotide triphosphates (dNTPs), which are the building blocks for DNA. Once the virus replicates, the resulting DNA molecule contains all the genes of the virus and instructs the cell to make more virus.

SAMHD1 protein protects cells from viruses by destroying dNTPs, leaving the virus without having to make the building blocks of genetic information - a process called nucleotide pool depletion research. As a result, the most common form of HIV does not readily infect these cells. Instead, the virus has evolved to replicate mainly in a different kind of cell, called CD4 T-cells, which do not contain SAMHD1 and therefore have a healthy pool of dNTPs. SAMHD1 essentially starves the virus,” Dr. Landau said. “The virus enters the cell and then nothing happens. It has nothing to build and replicate with, so no DNA is made.” Dr. Landau explained that the virus has evolved in such a way that it may deliberately avoid trying to infect immune cells with SAMHD1 to avoid alerting the greater immune system to activate a variety of antiviral mechanisms to attack the virus. Viruses that are related to HIV, like HIV-2 and SIV, have developed a protein called viral protein X (VPX) that directly attacks SAMHD1. This allows the virus to infect dendritic cells, an important type of immune cell.

“Viruses are remarkably clever about evading our immune defenses,” Dr. Landau said. “They can evolve quickly and have developed ways to get around the systems we naturally have in place to protect us. It’s a bit of evolutionary warfare and the viruses, unfortunately, usually win. We want to understand how the enemy fights so that we can outsmart it in the end.”

Understanding the mechanism by which SAMHD1 provides protection to cells may provide a new idea about how to stop or slow the virus’ ability to spread, Dr. Landau explained. Potential future research efforts, for example, might focus on finding a way to increase the amount of SAMHD1 in cells where it does not exist, or to reduce the amount of dNTPs in cells vulnerable to infection.

“Over the past few years, a number of these natural resistance mechanisms have been identified, specifically in HIV, but some have potential applications to other viruses, as well,” he said. “This is a very exciting time in HIV research. Many of the virus’ secrets are being revealed through molecular biology, and we’re learning a tremendous amount about how our immune system works through the study of HIV.”

This article has edited by authors of threelas
Source: http://www.newswise.com/articles/new-research-reveals-how-protein-protects-cells-from-hiv-infection
Publication: http://www.nature.com/ni/journal/vaop/ncurrent/full/ni.2236.html

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