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

Abstract

Strong antibody (Ab) responses against V1V2 epitopes of the human immunodeficiency virus type 1 (HIV-1) gp120 envelope (Env) correlated with reduced infection rates in studies of HIV, simian-human immunodeficiency virus (SHIV), and simian immunodeficiency virus (SIV). In order to focus the Ab response on V1V2, we used six V1V2 sequences and nine scaffold proteins to construct immunogens which were tested using various immunization regimens for their ability to induce cross-reactive and biologically active V2 Abs in rabbits. A prime/boost immunization strategy was employed using gp120 DNA and various V1V2-scaffold proteins. The rabbit polyclonal Ab responses (i) were successfully focused on the V1V2 region, with weak or only transient responses to other Env epitopes, (ii) displayed broad cross-reactive binding activity with gp120s and the V1V2 regions of diverse strains from clades B, C, and E, (iii) included V2 Abs with specificities similar to those found in HIV-infected individuals, and (iv) remained detectable >1 year after the last boosting dose. Importantly, sera from rabbits receiving V1V2-scaffold immunogens displayed Ab-dependent cellular phagocytosis whereas sera from rabbits receiving only gp120 did not. The results represent the first fully successful example of reverse vaccinology in the HIV vaccine field with rationally designed epitope scaffold immunogens inducing Abs that recapitulate the epitope specificity and biologic activity of the human monoclonal Abs from which the immunogens were designed. Moreover, this is the first immunogenicity study using epitope-targeting, rationally designed vaccine constructs that induced an Fc-mediated activity associated with protection from infection with HIV, SIV, and SHIV. IMPORTANCENovel immunogens were designed to focus the antibody response of rabbits on the V1V2 epitopes of HIV-1 gp120 since such antibodies were associated with reduced infection rates of HIV, SIV, and SHIV. The vaccine-induced antibodies were broadly cross-reactive with the V1V2 regions of HIV subtypes B, C and E and, importantly, facilitated Fc-mediated phagocytosis, an activity not induced upon immunization of rabbits with gp120. This is the first immunogenicity study of vaccine constructs that focuses the antibody response on V1V2 and induces V2-specific antibodies with the ability to mediate phagocytosis, an activity that has been associated with protection from infection with HIV, SIV, and SHIV. N onneutralizing antibodies (Abs) can protect against various viral infections, contributing to protection from alphaviruses, flaviviruses, respiratory syncytial virus (RSV), and cytomegalovirus, among others (reviewed in references 1 and 2). While the specificity and affinity of nonneutralizing Abs are dependent on the Fab fragment of Abs to target virions and infected cells, many of the biologic activities of these Abs are a function of the Fc fragment. Such activities include Ab-dependent cellular cytotoxicity (ADCC), Ab-dependent cellular phagocytosis (ADCP), Abdependent cell-media...

HIV-1 Vaccine Sequences Impact V1V2 Antibody Responses: A Comparison of Two Poxvirus Prime gp120 Boost Vaccine Regimens

“…Therefore, antibodies directly targeting the linear LDI/V α4β7 binding site, as measured by the peptide microarray, are not likely to contribute significantly to potential protection mechanisms involving gp120-α4β7 interactions with these two vaccine regimens. Nevertheless, V2 hotspot binding mAbs isolated from RV144 and RV305 subjects were shown to be capable of blocking α4β7 binding 24,25 , and a more recent study 22 showed that a group of V2 linear epitope binding antibodies (V2p) 26 that can block α4β7 binding recognized helical V2 conformations involving a potential α4β7 binding secondary determinant at aa170-172 37 , which the V2 hotspot overlaps. Therefore, even though the binding response that directly targets the LDI/V motif was minimal in this study, other V2 antibodies including those targeting the linear V2 hotspot may have the potential to interfere with V2-α4β7 interactions.…”

Phagocytosis of a Model Human Immunodeficiency Virus Target by Human Breast Milk Leukocytes Is Predominantly Granulocyte-Driven When Elicited by Specific Antibody

“…The anti-HIV human mAb 830A was used for all experiments. 43 It was derived from an HIV-infected individual and is weakly neutralizing, specific for a conformational epitope in the V2 region of Env, representative of V2i-specific Abs commonly elicited by natural infection, and been shown previously to function well in ADCP assays. 44,45 Antianthrax human mAb 3865 was used as a nonspecific negative control.…”

“…It was designed to mimic the trimeric V1V2 conformation in the stabilized BG505 SOSIP.664 crystal structure that is thought to be representative of the ground-state conformation of native HIV Env. 50 This scaffolded V1V2-Env protein has been found to elicit V2-specific Abs in rabbits and nonhuman primates (NHP) and is part of a larger study aimed to design V2-based immunogens following the RV144 finding that protection correlated with elicitation of V2-specific Abs in vaccines, although it was not one of the immunogens included in the RV144 trial 43,51 (NHP manuscript submitted). V1V2-2F5K was produced in-house, as described by Jiang et al, 50 and subsequently biotinylated using the EZ-LinkÔ NHS-LC-LC-Biotin kit (Thermo Fisher) according to the manufacturer's protocol.…”

Antibody Functional Assays as Measures of Fc Receptor-Mediated Immunity to HIV - New Technologies and their Impact on the HIV Vaccine Field

“…Since ADCC Abs are relatively easily elicited compared to bNAbs [ 55 - 58 ] and characterised mAbs such as CH58 and CH59 are not extensively hypermutated, the V2 loop is a possible immunogen for developing FcγR functional antibody responses [ 56 ]. Furthermore the V2 loop has been successfully scaffolded in immunisation studies that elicited ADCP active antibodies in rabbits, whereas immunization with gp120 did not raise ADCP functional Abs [ 59 ].…”