A stolen shield also protects
In a virus that affects the skin of people with a weakened immune system, a gene was discovered that might help the pathogen to protect itself against ultraviolet radiation and the human immune system protein, while other viruses have nothing comparable. Molluscum contagiosum virus (MCV) causes a stubborn and sometimes disfiguring skin condition that is common among people living with HIV and other people with compromised immune systems. Scientists have found a gene in his genetic material that is very similar to the human gene for glutathione peroxidase. This enzyme neutralizes dangerous chemicals called peroxides, which are made by cells in the immune system to fight infection.
Bernard Moss of the Laboratory of Viral Diseases (LVD) and his colleagues at the same research facility and the Harvard Institutes of Medicine report in Science of January 2, 1998 that the viral gene encodes a protein just like its human counterpart, which contains selenium. This element is rare in proteins, none of which have been found in viruses.
Human cell cultures into which the researchers introduced the MCV gene were largely protected against UV light and peroxides. Normally, the radiation and chemicals should have caused cell death.
But according to Moss, it is too early to make definitive statements about the real role of selenoprotein in the virus. Since there is no suitable animal model for MCV infection and the virus does not grow in tissue culture, relevant information is difficult to obtain. The scientists therefore only speculate that MCV "stole" the selenoprotein gene from human skin cells to protect itself against radiation and the immune system. Because the base sequences of the viral and human genes are nearly 75 percent identical, Moss and his co-workers believe MCV acquired the gene only recently. The remaining genes of the virus are only 20 to 25 percent identical to their human counterparts.
"That would be a clever trick for a virus that replicates in the epidermis," says Moss. And he adds that the results not only advance our understanding of the virus-human interaction, but could also provide valuable insight into how human glutathione peroxidase works.
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