A Trimeric HIV-1 Envelope gp120 Immunogen Induces Potent and Broad Anti-V1V2 Loop Antibodies against HIV-1 in Rabbits and Rhesus Macaques

Abstract

Trimeric HIV-1 envelope (Env) immunogens are attractive due to their ability to display quaternary epitopes targeted by broadly neutralizing antibodies (bNAbs) while obscuring unfavorable epitopes. Results from the RV144 trial highlighted the importance of vaccine-induced HIV-1 Env V1V2-directed antibodies, with key regions of the V2 loop as targets for vaccine-mediated protection. We recently reported that a trimeric JRFL-gp120 immunogen, generated by inserting an N-terminal trimerization domain in the V1 loop region of a cyclically permuted gp120 (cycP-gp120), induces neutralizing activity against multiple tier-2 HIV-1 isolates in guinea pigs in a DNA prime/protein boost approach. Here, we tested the immunogenicity of cycP-gp120 in a protein prime/boost approach in rabbits and as a booster immunization to DNA/modified vaccinia Ankara (MVA)-vaccinated rabbits and rhesus macaques. In rabbits, two cycP-gp120 protein immunizations induced 100-fold higher titers of high-avidity gp120-specific IgG than two gp120 immunizations, with four total gp120 immunizations being required to induce comparable titers. cycP-gp120 also induced markedly enhanced neutralizing activity against tier-1A and -1B HIV-1 isolates, substantially higher binding and breadth to gp70-V1V2 scaffolds derived from a multiclade panel of global HIV-1 isolates, and antibodies targeting key regions of the V2-loop region associated with reduced risk of infection in RV144. Similarly, boosting MVA- or DNA/MVA-primed rabbits or rhesus macaques with cycP-gp120 showed a robust expansion of gp70-V1V2-specific IgG, neutralization breadth to tier-1B HIV-1 isolates, and antibody-dependent cellular cytotoxicity activity. These results demonstrate that cycP-gp120 serves as a robust HIV Env immunogen that induces broad anti-V1V2 antibodies and promotes neutralization breadth against HIV-1.IMPORTANCE Recent focus in HIV-1 vaccine development has been the design of trimeric HIV-1 Env immunogens that closely resemble native HIV-1 Env, with a major goal being the induction of bNAbs. While the generation of bNAbs is considered a gold standard in vaccine-induced antibody responses, results from the RV144 trial showed that nonneutralizing antibodies directed toward the V1V2 loop of HIV-1 gp120, specifically the V2 loop region, were associated with decreased risk of infection, demonstrating the need for the development of Env immunogens that induce a broad anti-V1V2 antibody response. In this study, we show that a novel trimeric gp120 protein, cycP-gp120, generates high titers of high-avidity and broadly cross-reactive anti-V1V2 antibodies, a result not found in animals immunized with monomeric gp120. These results reveal the potential of cycP-gp120 as a vaccine candidate to induce antibodies associated with reduced risk of HIV-1 infection in humans.

A facile method of mapping HIV-1 neutralizing epitopes using chemically masked cysteines and deep sequencing

“…Epitopes in plasma from the NAB059 elite neutralizer contained quaternary epitopespecific and CD4-binding site-specific signatures ( Figure 3B, Table S4). The CycP sera contained epitope specificities mapping to the V1V2 loop and CD4-binding site ( Figure 3B, Table S4), which were consistent with earlier observations using mammalian cell surface display and mutant pseudoviruses (31,32). Both polyclonal sera were observed to encompass multiple antibody specificities (Figures 3B), which account for their observed neutralization activity.…”

Bacterially expressed HIV-1 gp120 outer-domain fragment immunogens with improved stability and affinity for CD4-binding site neutralizing antibodies

“…By comparing all the groups boosted with monomeric gp120 protein, the OD priming immunogens can be arranged in increasing order of their ability to induce anti-gp120 titers (week 22) as follows: ⌬BS-OD EC Ͻ OD EC Ͻ OD EC C1 Ͻ OD EC Consensus Ͻ OD EC C2 Ͻ OD EC CycV4. Similarly, a comparison of week 22 anti-gp120 titers for the three groups primed with ⌬BS-OD EC but boosted with different Env derivatives indicated that the V1cycP gp120 previously designed by us (30,35,36) provides the best boost for inducing high anti-gp120 titers. In summary, the ELISA results indicated that the OD EC CycV4 and OD EC C2 are the best primes for eliciting sera with high anti-gp120 titers.…”

Human Immunodeficiency Virus C.1086 Envelope gp140 Protein Boosts following DNA/Modified Vaccinia Virus Ankara Vaccination Fail To Enhance Heterologous Anti-V1V2 Antibody Response and Protection against Clade C Simian-Human Immunodeficiency Virus Challenge

“…To overcome this limitation, a recent study used pentavalent gp120 protein boosts to enhance the breadth of the anti-V2 antibody response and showed that this improved protection against clade C SHIV (41). Toward this goal, we recently developed a trimeric, cyclically permuted gp120 protein that induces a strong and broad anti-V1V2 response in rabbits and macaques (42). In conclusion, these results demonstrate that sequential immunizations with C.1086-based DNA, MVA, and gp140 protein induce a robust cellular and humoral immune response to HIV, but they do not protect against a heterologous intrarectal clade C SHIV challenge.…”

“…It is also important to note that the V2 HS of the C.1086 protein is distant from the V2 HS of the clade C consensus sequence, suggesting that C.1086 Env-induced anti-V2 HS antibodies may not cross-react with the V2 HS of most of the primary clade C isolates. Our recent study with cyclically permuted gp120 protein showed that it is possible to generate broad anti-V2 HS antibodies by vaccination in rabbits and macaques (42).…”