Hongying Duan (Holdsworth), M.D., Ph.D.

1. Elicitation and maturation of VRC01-class antibodies in transgenic mouse models, which allows a germline human IGHV1-2*02 segment to undergo normal V(D)J recombination and, thereby, leads to the generation of peripheral B cells that express a highly diverse repertoire of VRC01-related receptors. A strong VRC01-class predicted germline precursor binder, eOD-GT8 60mer, was able to elicit and enrich VRC01-class antibodies in this mouse model.

2. Induction of HIV Neutralizing Antibody Lineages in Mice with Diverse Precursor Repertoires with sequential immunization. The serum from the stepwise immunized mice exhibited cross-strain neutralizing activities and the mutation frequency of both the IGHV1-2*02 IgH and VRC01 IgL chains steadily increased.

 3. Glycan Masking Focuses Immune Responses to the HIV-1 CD4-Binding Site and Enhances Elicitation of VRC01-Class Precursor Antibodies. A substantial portion of eOD-GT8-elicited antibodies target non-CD4bs epitopes, potentially limiting its efficacy. To mask irrelevant epitopes, we introduced N-linked glycans into non-CD4bs surfaces of eOD-GT8 and evaluated the mutants in a VRC01-class mouse model. Compared to the parental eOD-GT8, a mutant with five added glycans stimulated significantly higher proportions of CD4bs specific serum responses and CD4bs-specific immunoglobulin G+ B cells including VRC01-class precursors.

4. Antibody Lineages with Vaccine-Induced Antigen-Binding Hotspots Develop Broad HIV Neutralization. The vaccine-mediated elicitation of antibodies (Abs) capable of neutralizing diverse HIV-1 strains has been a long-standing goal. To understand how broadly neutralizing antibodies (bNAbs) develop, we identified, characterized, and tracked five neutralizing Ab lineages targeting the HIV-1-fusion peptide (FP) in vaccinated macaques over time. Genetic and structural analyses revealed two of these lineages to belong to a reproducible class capable of neutralizing up to 59% of 208 diverse viral strains. B cell analysis indicated that each of the five lineages was initiated and expanded by FP-carrier priming, with envelope (Env)-trimer boosts inducing cross-reactive neutralization.

5. Fusion Peptide Priming –Alone or in Cocktail with Env Trimer– Imprints Broad HIV-1-Neutralizing Responses with a Characteristic Early B Cell Signature. To optimize the immunization regimen and shorten the “neutralization-eclipse phase”, we analyzed plasma and antigen-specific B cells from 7 different immunization regimens in 32 macaques with a common boosting module comprising five FP/Trimer immunizations. We found that FP priming to imprint cross-reactive FP-directed HIV-neutralizing responses, with FP-trimer cocktail elicited the earliest cross-strain responses.

6. Fusion Peptide Priming Reduces Immune Responses to HIV-1 Envelope Trimer Base. Soluble ‘SOSIP’-stabilized envelope (Env) trimers are promising HIV-vaccine immunogens. However, they induce high titer responses against the glycan-free trimer base, which is occluded on native virions. To delineate the impact on base responses of priming with immunogens targeting the fusion peptide (FP) site of vulnerability, we quantified the prevalence of trimer-base antibody responses in 49 non-human primates (NHPs) immunized with various SOSIP-stabilized Env trimers and FP-carrier conjugates. We found that trimer-base responses accounted for ~90% of the overall trimer response in animals immunized with trimer only, ~70% in animals immunized with a cocktail of SOSIP-trimer and FP-conjugate, and ~30% in animals primed with FP-conjugate prior to trimer immunization, with neutralization breadth in FP-conjugate-primed animals correlated inversely with trimer-base responses.