Envelope Variants Circulating as Initial Neutralization Breadth Developed in Two HIV-Infected Subjects Stimulate Multiclade Neutralizing Antibodies in Rabbits

Abstract

Identifying characteristics of the human immunodeficiency virus type 1 (HIV-1) envelope that are effective in generating broad, protective antibodies remains a hurdle to HIV vaccine design. Emerging evidence of the development of broad and potent neutralizing antibodies in HIV-infected subjects suggests that founder and subsequent progeny viruses may express unique antigenic motifs that contribute to this developmental pathway. We hypothesize that over the course of natural infection, B cells are programmed to develop broad antibodies by exposure to select populations of emerging envelope quasispecies variants. To test this hypothesis, we identified two unrelated subjects whose antibodies demonstrated increasing neutralization breadth against a panel of HIV-1 isolates over time. Full-length functional env genes were cloned longitudinally from these subjects from months after infection through 2.6 to 5.8 years of infection. Motifs associated with the development of breadth in published, cross-sectional studies were found in both subjects. We compared the immunogenicity of envelope vaccines derived from time points obtained during and after broadening of neutralization activity within these subjects. Rabbits were coimmunized four times with selected multiple gp160 DNAs and gp140-trimeric envelope proteins. The affinity of the polyclonal response increased as a function of boosting. The most rapid and persistent neutralization of multiclade tier 1 viruses was elicited by envelopes that were circulating in plasma at time points prior to the development of 50% neutralization breadth in both human subjects. The breadth elicited in rabbits was not improved by exposure to later envelope variants. These data have implications for vaccine development in describing a target time point to identify optimal envelope immunogens. IMPORTANCEVaccine protection against viral infections correlates with the presence of neutralizing antibodies; thus, vaccine components capable of generating potent neutralization are likely to be critical constituents in an effective HIV vaccine. However, vaccines tested thus far have elicited only weak antibody responses and very modest, waning protection. We hypothesized that B cells develop broad antibodies by exposure to the evolving viral envelope population and tested this concept using multiple envelopes from two subjects who developed neutralization breadth within a few years of infection. We compared different combinations of envelopes from each subject to identify the most effective immunogens and regimens. In each subject, use of HIV envelopes circulating during the early development and maturation of breadth generated more-potent antibodies that were modestly cross neutralizing. These data suggest a new approach to identifying envelope immunogens that may be more effective in generating protective antibodies in humans.A human immunodeficiency virus type 1 (HIV-1) envelope (Env) component that effectively stimulates the humoral arm of the adaptive immune response will be a critical ...

Achieving Potent Autologous Neutralizing Antibody Responses against Tier 2 HIV-1 Viruses by Strategic Selection of Envelope Immunogens

“…Single genome amplification and env cloning was previously performed and described (22) to isolate sequences subsequently used as DNA and protein immunogens. DNA vaccine gene Gun cartridges.…”

“…A large-scale endotoxin-free plasmid preparation (Qiagen, Valencia, CA) was used for stable expression in 293F cells for protein production as described previously (30). Epitope exposure and antigenicity of gp140 trimeric protein immunogens was assessed by ELISA, biolayer interferometry (BLI), and surface plasmon resonance for binding of multiple bNmAbs as described previously (22).…”

“…Despite multiple efforts to develop an immunogen or immunogens that can elicit bNAbs following vaccination, success has been limited (12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Some incremental advances have been made, including our recent immunogenicity studies (22) and those of others (23)(24)(25) that have shown an advantage of coimmunization with DNA and protein immunogens, including the potential of contracting the vaccine regimen to a small number of immunizations to reach peak NAb responses. Although breadth and potency of an elicited bNAb response is considered a prudent goal, it may be equally important to induce Abs that will rapidly prevent infection of the transmitted/founder (T/F) virus.…”

“…In these subjects, only a few critical epitopes that emerged within the first 2 y of infection accounted for affinity maturation resulting in distinctly unique pathways, leading to moderate breadth (27). After cloning and assessing a sizeable collection of gp160 env quasispecies representing the longitudinal evolution of env circulating within each individual, we designed DNA and protein vaccines using native envs and systematically conducted multiple comparative immunogenicity studies in rabbits (22). Vaccinating with selected natural quasispecies envs, we demonstrated that envs identified from two separate subjects can induce equally strong Ab responses and that some envs were superior to others.…”

“…We studied the phylogeny of HIV-1 envelope gene sequence (env) evolving during infection in two clade B infected individuals enrolled in the Tennessee Center for AIDS Research (CFAR), Vanderbilt University School of Medicine Cohort who developed moderate bNAbs less than 3 y after infection (22). Breadth in subject VC10014 was attributed to an epitope in gp120 that overlaps the CD4 binding site (CD4bs), and VC10013 breadth was mapped to a previously unrecognized epitope in the membrane proximal external region (MPER) of gp41.…”