Posted on January 17, 2019
"HIV is a master of sneaking past our natural defenses. Typically, when the body encounters a harmful virus, immune cells recognize viral proteins and stimulate the production of protective proteins called antibodies. These antibodies mount a powerful immune response that clears the virus and protects the body from future infection. HIV, however, has evolved several ways to cloak vulnerable areas of viral proteins that antibodies might otherwise recognize. A report released last month from NIAID scientists in the journal MBio reveals new insights into one such tactic of immune invisibility."
"The findings center on an important protein on the surface of HIV, or envelope protein, known as Env. After the discovery of HIV, scientists noticed that Env plays a critical role in establishing HIV infection in the body. A region of the protein connects with a receptor on the surface of certain human T cells, allowing the virus to enter the cell and eventually replicate. Env slips past the immune system in part because of its clever shape: three identical subunits arrange so that Env’s sugar-coated surface faces the environment while protein areas immune cells can recognize, called epitopes, are sheltered within the “closed” structure. The immune system is much less likely to recognize sugars than proteins, and the physical arrangement of Env—resembling the closed petals of a crocus flower at night—keeps the vulnerable epitopes hidden away from lurking antibodies."