Acquired immunodeficiency syndrome (AIDS) in humans and monkeys is caused by the human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV), respectively. Both viruses express a protein called gp120, which binds to immune cells expressing another protein, called CD4, on their surface. Binding of gp120 to CD4 causes the virus to infect cells. The structure of gp120 bound to CD4 has been known since 1998; however, the unbound form - which is important for the design of therapeutics and vaccines - has eluded researchers for decades.
In the 24 Feb 2005 issue of Nature (Vol. 433, No. 7028, pp. 834-841), Stephen Harrison and his colleagues, in a technical tour de force, describe the structure of the unbound form of gp120 derived from SIV. It turns out that the structure of the protein differs dramatically in the unbound form compared with the CD4-bound form.
In an accompanying News and Views article, Peter Kwong says that the "tantalizing new details" revealed by Harrison's group helps to explain how the HIV virus remains able to simultaneously infect host cells and evade immune surveillance, adding hope to new strategies for vaccine development.
Stephen Harrison (Children's Hospital and HHMI, Harvard Medical School, Boston, MA, USA)
Tel: +1 617 432 5607
Peter Kwong (Vaccine Research Center, NIAID/NIH, Bethesda, MD, USA)
Tel: +1 301 594 8685
(C) Nature press release.
Message posted by: Trevor M. D'Souza