Structure-based design of a protein immunogen that displays an HIV-1 gp41 neutralizing epitope.
Antibody Z13e1 is a relatively broadly neutralizing anti-human immunodeficiency virus type 1 antibody that recognizes the membrane-proximal external region (MPER) of the human immunodeficiency virus type 1 envelope glycoprotein gp41. Based on the crystal structure of an MPER epitope peptide in complex with Z13e1 Fab, we identified an unrelated protein, interleukin (IL)-22, with a surface-exposed region that is structurally homologous in its backbone to the gp41 Z13e1 epitope. By grafting the gp41 Z13e1 epitope sequence onto the structurally homologous region in IL-22, we engineered a novel protein (Z13-IL22-2) that contains the MPER epitope sequence for use as a potential immunogen and as a reagent for the detection of Z13e1-like antibodies. The Z13-IL22-2 protein binds Fab Z13e1 with a K(d) of 73 nM. The crystal structure of Z13-IL22-2 in complex with Fab Z13e1 shows that the epitope region is faithfully replicated in the Fab-bound scaffold protein; however, isothermal calorimetry studies indicate that Fab binding to Z13-IL22-2 is not a lock-and-key event, leaving open the question of whether conformational changes upon binding occur in the Fab, in Z13-IL-22, or in both.
Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA. robyn@scripps.edu
Robyn L
RL
Stanfield
Jean-Philippe
JP
Julien
Robert
R
Pejchal
Johannes S
JS
Gach
Michael B
MB
Zwick
Ian A
IA
Wilson
D000595:Amino Acid Sequence; D002151:Calorimetry / Q000379:methods; D018360:Crystallography, X-Ray / Q000379:methods; D000939:Epitopes / Q000737:chemistry; D015700:HIV Envelope Protein gp41 / Q000737:chemistry*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry; D007378:Interleukins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D010455:Peptides / Q000737:chemistry*; D015202:Protein Engineering / Q000379:methods; D017386:Sequence Homology, Amino Acid; D013499:Surface Properties; D013816:Thermodynamics; D000097043:Interleukin-22
D000939:Epitopes; D015700:HIV Envelope Protein gp41; D007140:Immunoglobulin Fab Fragments; D007378:Interleukins; D010455:Peptides; D000097043:Interleukin-22