Modified HIV envelope proteins with enhanced binding to neutralizing monoclonal antibodies.
The target for neutralizing antibodies against human immunodeficiency virus (HIV) is the trimeric Env protein on the native virion. Conserved neutralizing epitopes of receptor binding sites are located in the recessed core of the Env protein, partially masked by glycosylations and variable loops. In this study, we have investigated the effects of modifications of the HIV Env protein by glycosylation site mutations, deletions of variable loops, or combinations of both types of mutations on their protein functions and reactivities with neutralizing antibodies. Modified Env proteins were expressed in insect or mammalian cells, and their reactivity with epitope-specific broadly neutralizing monoclonal antibodies (Mabs) was determined by flow cytometry. A unique mutant designated 3G with mutations in three glycosylation motifs within the V3/C3 domains surrounding the CD4 binding site showed higher levels of binding to most broadly neutralizing Mabs (b12 and 2F5) in both insect and mammalian expression systems. Mutants with a deletion of both V1 and V2 loop domains or with a unique combination of both types of mutations also bound to most neutralizing Mabs at higher levels compared to the wild-type control. Most mutants maintained the ability to bind CD4 and to induce syncytium formation at similar or higher levels as compared to that of the wild-type Env protein, except for a mutant with a combination of variable loop deletions and deglycosylation mutations. Our study suggests that modified HIV Env proteins with reduced glycosylation in domains surrounding the CD4 binding site or variable loop-deleted mutants expose important neutralizing epitopes at higher levels than wild type and may provide novel vaccine immunogens.
Kang
Sang-Moo
SM
Department of Microbiology and Immunology, Emory University School of Medicine, 1510 Clifton Road, RRC 3086, Atlanta, GA 30322, USA. Skang2@emory.edu
Quan
Fu Shi
FS
Huang
Chunzi
C
Guo
Lizheng
L
Ye
Ling
L
Yang
Chinglai
C
Compans
Richard W
RW
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology*; D000937:Antigen-Antibody Reactions; D015704:CD4 Antigens / Q000276:immunology; D002460:Cell Line; D000939:Epitopes; D015686:Gene Products, env / Q000096:biosynthesis / Q000737:chemistry / Q000276:immunology*; D015726:Giant Cells / Q000276:immunology; D006031:Glycosylation; D015497:HIV-1 / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000096:biosynthesis
D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D000939:Epitopes; D015686:Gene Products, env; D011994:Recombinant Proteins