title: HIV-1 neutralizing antibodies display dual recognition of the primary and coreceptor binding sites and preferential binding to fully cleaved envelope glycoproteins.
abstract: The gp120 CD4 binding site (CD4bs) and coreceptor binding site (CoRbs) are two functionally conserved elements of the HIV-1 envelope glycoproteins (Env). We previously defined the presence of CD4bs-neutralizing antibodies in the serum of an HIV-1-infected individual and subsequently isolated the CD4bs-specific monoclonal antibodies (MAbs) VRC01 and VRC03 from the memory B cell population. Since this donor's serum also appeared to contain neutralizing antibodies to the CoRbs, we employed a differential fluorescence-activated cell sorter (FACS)-based sorting strategy using an Env trimer possessing a CoRbs knockout mutation (I420R) to isolate specific B cells. The MAb VRC06 was recovered from these cells, and its genetic sequence allowed us to identify a clonal relative termed VRC06b, which was isolated from a prior cell sort using a resurfaced core gp120 probe and its cognate CD4bs knockout mutant. VRC06 and VRC06b neutralized 22% and 44% of viruses tested, respectively. Epitope mapping studies revealed that the two MAbs were sensitive to mutations in both the gp120 CoRbs and the CD4bs and could cross-block binding of both CD4bs and CoRbs MAbs to gp120. Fine mapping indicated contacts within the gp120 bridging sheet and the base of the third major variable region (V3), which are elements of the CoRbs. Cell surface binding assays demonstrated preferential recognition of fully cleaved Env trimers over uncleaved trimers. Thus, VRC06 and VRC06b are Env trimer precursor cleavage-sensitive neutralizing MAbs that bind to a region of gp120 that overlaps both the primary and the secondary HIV-1 receptor binding sites.
authors.affiliation: Vaccine Research Center, NIAID, NIH, Bethesda, Maryland, USA.
authors.forename: Yuxing
authors.initials: Y
authors.lastname: Li
authors.forename: Sijy
authors.initials: S
authors.lastname: O'Dell
authors.forename: Richard
authors.initials: R
authors.lastname: Wilson
authors.forename: Xueling
authors.initials: X
authors.lastname: Wu
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Schmidt
authors.forename: Carl-Magnus
authors.initials: CM
authors.lastname: Hogerkorp
authors.forename: Mark K
authors.initials: MK
authors.lastname: Louder
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Longo
authors.forename: Christian
authors.initials: C
authors.lastname: Poulsen
authors.forename: Javier
authors.initials: J
authors.lastname: Guenaga
authors.forename: Bimal K
authors.initials: BK
authors.lastname: Chakrabarti
authors.forename: Nicole
authors.initials: N
authors.lastname: Doria-Rose
authors.forename: Mario
authors.initials: M
authors.lastname: Roederer
authors.forename: Mark
authors.initials: M
authors.lastname: Connors
authors.forename: John R
authors.initials: JR
authors.lastname: Mascola
authors.forename: Richard T
authors.initials: RT
authors.lastname: Wyatt
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism; D057134:Antibodies, Neutralizing / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology; D001666:Binding Sites, Antibody; D015704:CD4 Antigens / Q000276:immunology* / Q000378:metabolism; D002478:Cells, Cultured; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology; D015483:HIV Antibodies / Q000276:immunology* / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000276:immunology* / Q000378:metabolism; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology; D009154:Mutation; D015728:Receptors, HIV / Q000276:immunology* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D015704:CD4 Antigens; D000939:Epitopes; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; D007074:Immunoglobulin G; D015728:Receptors, HIV