title: Stabilized HIV-1 envelope glycoprotein trimers lacking the V1V2 domain, obtained by virus evolution.
abstract: The envelope glycoproteins (Env) are the focus of HIV-1 vaccine development strategies based on the induction of humoral immunity, but the mechanisms the virus has evolved to limit the induction and binding of neutralizing antibodies (NAbs) constitute substantial obstacles. Conserved neutralization epitopes are shielded by variable regions and carbohydrates, so one strategy to increase their exposure and, it is hoped, their immunogenicity is to delete the overlying variable loops. However, deleting the variable regions from Env trimers can be problematic, because hydrophobic patches that are normally solvent-inaccessible now become exposed, causing protein misfolding or aggregation, for example. Here, we describe the construction and characterization of recombinant gp140 trimers lacking variable domains 1 and 2 (ΔV1V2). The design of the trimers was guided by HIV-1 evolution studies that identified compensatory changes in V1V2-deleted but functional Env proteins (Bontjer, I., Land, A., Eggink, D., Verkade, E., Tuin, K., Baldwin, C., Pollakis, G., Paxton, W. A., Braakman, I., Berkhout, B., and Sanders, R. W. (2009) J. Virol. 83, 368-383). We now show that specific compensatory changes improved the function of ΔV1V2 Env proteins and hence HIV-1 replication. The changes acted by reducing the exposure of a hydrophobic surface either by replacing a hydrophobic residue with a hydrophilic one or by covering the surface with a glycan. The compensatory changes allowed the efficient expression of well folded, soluble gp140 trimers derived from various HIV-1 isolates. The evolved ΔV1V2 Env viruses were extremely sensitive to NAbs, indicating that neutralization epitopes are well exposed, which was confirmed by studies of NAb binding to the soluble ΔV1V2 gp140 trimers. These evolved ΔV1V2 trimers could be useful reagents for immunogenicity and structural studies.
authors.affiliation: Laboratory of Experimental Virology, Department of Medical Microbiology, Academic Medical Center of the University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Ilja
authors.initials: I
authors.lastname: Bontjer
authors.forename: Mark
authors.initials: M
authors.lastname: Melchers
authors.forename: Dirk
authors.initials: D
authors.lastname: Eggink
authors.forename: Kathryn
authors.initials: K
authors.lastname: David
authors.forename: John P
authors.initials: JP
authors.lastname: Moore
authors.forename: Ben
authors.initials: B
authors.lastname: Berkhout
authors.forename: Rogier W
authors.initials: RW
authors.lastname: Sanders
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D019020:Directed Molecular Evolution; D015483:HIV Antibodies / Q000276:immunology; D015488:HIV Antigens / Q000276:immunology; D015658:HIV Infections / Q000235:genetics / Q000276:immunology / Q000821:virology; D015497:HIV-1 / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D006801:Humans; D047468:Immunoprecipitation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009500:Neutralization Tests; D011134:Polysaccharides / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014779:Virus Replication; D054299:env Gene Products, Human Immunodeficiency Virus / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D015483:HIV Antibodies; D015488:HIV Antigens; D011134:Polysaccharides; D054299:env Gene Products, Human Immunodeficiency Virus; C097729:gp140 envelope protein, Human immunodeficiency virus 1
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