Rationally Designed Immunogens Targeting HIV-1 gp120 V1V2 Induce Distinct Conformation-Specific Antibody Responses in Rabbits

Abstract

The V1V2 region of HIV-1 gp120 harbors a major vulnerable site targeted by a group of broadly neutralizing monoclonal antibodies (MAbs) such as PG9 through strand-strand recognition. However, this epitope region is structurally polymorphic as it can also form a helical conformation recognized by RV144 vaccine-induced MAb CH58. This structural polymorphism is a potential mechanism for masking the V1V2 vulnerable site. Designing immunogens that can induce conformation-specific antibody (Ab) responses may lead to vaccines targeting this vulnerable site. We designed a panel of immunogens engrafting the V1V2 domain into trimeric and pentameric scaffolds in structurally constrained conformations. We also fused V1V2 to an Fc fragment to mimic the unconstrained V1V2 conformation. We tested these V1V2-scaffold proteins for immunogenicity in rabbits and assessed the responses by enzyme-linked immunosorbent assay (ELISA) and competition assays. Our V1V2 immunogens induced distinct conformation-specific Ab responses. Abs induced by structurally unconstrained immunogens reacted preferentially with unconstrained V1V2 antigens, suggesting recognition of the helical configuration, while Abs induced by the structurally constrained immunogens reacted preferentially with constrained V1V2 antigens, suggesting recognition of the ␤-strand conformation. The Ab responses induced by the structurally constrained immunogens were more broadly reactive and had higher titers than those induced by the structurally unconstrained immunogens. Our results demonstrate that immunogens presenting the different structural conformations of the gp120 V1V2 vulnerable site can be designed and that these immunogens induce distinct Ab responses with epitope conformation specificity. Therefore, these structurally constrained V1V2 immunogens are vaccine prototypes targeting the V1V2 domain of the HIV-1 envelope. IMPORTANCEThe correlates analysis of the RV144 HIV-1 vaccine trial suggested that the presence of antibodies to the V1V2 region of HIV-1 gp120 was responsible for the modest protection observed in the trial. In addition, V1V2 harbors one of the key vulnerable sites of HIV-1 Env recognized by a family of broadly neutralizing MAbs such as PG9. Thus, V1V2 is a key target for vaccine development. However, this vulnerable site is structurally polymorphic, and designing immunogens that present different conformations is crucial for targeting this site. We show here that such immunogens can be designed and that they induced conformation-specific antibody responses in rabbits. Our immunogens are therefore prototypes of vaccine candidates targeting the V1V2 region of HIV-1 Env.

Particulate Array of Well-Ordered HIV Clade C Env Trimers Elicits Neutralizing Antibodies that Display a Unique V2 Cap Approach

“…The immunogenic properties of the V2 region were also shown by the isolation of glycan-dependent V2-targeting bNAbs from chronic infected individuals (McLellan et al, 2011; Walker et al, 2009) and isolation of monoclonal antibodies with ADCC activity from RV144 clinical trial vaccine recipients (CH58-59) (Liao et al, 2013), encouraging the design of V2-based immunogens (Jiang et al, 2016; Mayr et al, 2013). Further, the V2 region was shown to interact with the integrin α4β7 (Arthos et al, 2008) proximal to the region where the vaccine-induced mAbs reported here bind.…”

Rationally Designed Vaccines Targeting the V2 Region of HIV-1 gp120 Induce a Focused, Cross-Clade-Reactive, Biologically Functional Antibody Response

“…V1V2 is presented by the 2F5K and 2J9C scaffolds as an apical trimeric structure whose conformation is constrained by their insertion in these scaffolds (47). In contrast, the V1V2 region in gp120 is presented as a monomeric, unconstrained domain.…”

“…Genes of the V1V2 scaffolds were chemically synthesized and cloned into the pVRC8400 plasmid, followed by expression in HEK293 GnTI Ϫ/Ϫ cells and purification by affinity chromatography (46). Details of the design and construction of the immunogens are described separately (47). The V1V2-tags protein of strain 1086 (V1V2 1086 -tags) and V1V2 A244 -tags were provided by H. Liao (Duke University), V1V2 CaseA2 -gp70 and V1V2 92TH023 -gp70 were provided by A Pinter, and gp120 A244 was provided by Global Solutions for Infectious Diseases (South San Francisco, CA).…”

How HIV-1 entry mechanism and broadly neutralizing antibodies guide structure-based vaccine design

“…2). Structures of apex V1V2-directed antibodies (PG9, PG16 [41,42] and more recently CH03 [44••]) in complex with V1V2 domain-scaffolds have been used as templates for glycosylated V1V2 peptide [111] and V1V2-epitope scaffold immunogens [112,113•]. Structures of N332 glycan patch directed antibodies (PGT128, PGT135, PGT122 [51,53,54]) with gp120 core or HIV-1 Env trimer have highlighted a supersite of vulnerability that can be targeted from different angles and have led to designs of V3 glycosylated peptides [115•] and V3 epitope scaffolds [112].…”