HIV antibody-glycoprotein complex. Molecular model of the human immunodeficiency virus (HIV-1) D5 fab (fragment antigen-binding) antibody (pink) forming a complex with a structure called 5-helix (green and blue). The 5-helix structure is an inner core mimetic gp41 helix. This study is part of the attempts to design antibodies for use in vaccines against HIV, the virus that causes AIDS (acquired immunodeficiency syndrome). The gp41 helix is a region targeted by such vaccines.