Researchers have snuck a detailed peek at the crystal structure of a known broadly neutralizing human immunodeficiency virus (HIV-1) antibody as it binds to a specific part of HIV-1. The find, reported in the 15 February 2007 issue of Nature (Vol. 445, No. 7129, pp. 732-737), is important because the binding site represents a chink in HIV's armour that could help guide future vaccine development.
HIV keeps one step ahead of the human immune system by mutating frequently and changing its shape. But certain parts of the virus must remain relatively unchanged so that it can continue to bind to and enter human cells. gp120, a glycoprotein that juts out from the surface of the virus and binds to CD4 receptor on host cells, is one such region, making it a target for vaccine development.
Peter D. Kwong and colleagues made variants of stable gp120 that could be recognized by antibodies. They then looked in detail at the binding of one antibody, called b12, to the glycoprotein and found that the antibody approaches in an orientation very similar to that of CD4. Although other antibodies bind at this sight, b12 is the only one that binds and neutralizes a relatively broad range of HIV-1 isolates, so the results may help explain why.
Peter D. Kwong (National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, USA)
(C) Nature press release.
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