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SARS-CoV-2-neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) or the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-γ (FcγR)-mediated enhancement of virus infection in vitro, while five non-neutralizing NTD antibodies mediated FcγR-independent in vitro infection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Three of 46 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, while in vitro antibody-enhanced infection does not necessarily herald enhanced infection in vivo, increased lung inflammation can rarely occur in SARS-CoV-2 antibody-infused macaques., Competing Interests: Declaration of interests B.F.H., G.D.S., K.O.S., R.P., D.L., P.A., and X.L. have applied for patents concerning SARS-CoV-2 Abs that are related to this work. All other authors declare no conflict of interest., (Copyright © 2021 Elsevier Inc. All rights reserved.) more...

A goal for an HIV-1 vaccine is to overcome virus variability by inducing broadly neutralizing antibodies (bnAbs). One key target of bnAbs is the glycan-polypeptide at the base of the envelope (Env) third variable loop (V3). We have designed and synthesized a homogeneous minimal immunogen with high-mannose glycans reflective of a native Env V3-glycan bnAb epitope (Man 9 -V3). V3-glycan bnAbs bound to Man 9 -V3 glycopeptide and native-like gp140 trimers with similar affinities. Fluorophore-labeled Man 9 -V3 glycopeptides bound to bnAb memory B cells and were able to be used to isolate a V3-glycan bnAb from an HIV-1-infected individual. In rhesus macaques, immunization with Man 9 -V3 induced V3-glycan-targeted antibodies. Thus, the Man 9 -V3 glycopeptide closely mimics an HIV-1 V3-glycan bnAb epitope and can be used to isolate V3-glycan bnAbs., (Copyright © 2017, American Association for the Advancement of Science.) more...

Induction of broadly neutralizing antibodies (bnAbs) that target HIV-1 envelope (Env) is a goal of HIV-1 vaccine development. A bnAb target is the Env third variable loop (V3)-glycan site. To determine whether immunization could induce antibodies to the V3-glycan bnAb binding site, we repetitively immunized macaques over a 4-year period with an Env expressing V3-high mannose glycans. Env immunizations elicited plasma antibodies that neutralized HIV-1 expressing only high-mannose glycans-a characteristic shared by early bnAb B cell lineage members. A rhesus recombinant monoclonal antibody from a vaccinated macaque bound to the V3-glycan site at the same amino acids as broadly neutralizing antibodies. A structure of the antibody bound to glycan revealed that the three variable heavy-chain complementarity-determining regions formed a cavity into which glycan could insert and neutralized multiple HIV-1 isolates with high-mannose glycans. Thus, HIV-1 Env vaccination induced mannose-dependent antibodies with characteristics of V3-glycan bnAb precursors., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.) more...

Detailed studies of the broadly neutralizing antibodies (bNAbs) that underlie the best available examples of the humoral immune response to HIV are providing important information for the development of therapies and prophylaxis for HIV-1 infection. Here, we report a CD4-binding site (CD4bs) antibody, named N6, that potently neutralized 98% of HIV-1 isolates, including 16 of 20 that were resistant to other members of its class. N6 evolved a mode of recognition such that its binding was not impacted by the loss of individual contacts across the immunoglobulin heavy chain. In addition, structural analysis revealed that the orientation of N6 permitted it to avoid steric clashes with glycans, which is a common mechanism of resistance. Thus, an HIV-1-specific bNAb can achieve potent, near-pan neutralization of HIV-1, making it an attractive candidate for use in therapy and prophylaxis., (Published by Elsevier Inc.) more...

Antibody polyreactivity can be an obstacle to translating a candidate antibody into a clinical product. Standard tests such as antibody binding to cardiolipin, HEp-2 cells, or nuclear antigens provide measures of polyreactivity, but its causes and the means to resolve are often unclear. Here we present a method for eliminating antibody polyreactivity through the computational design and genetic addition of N-linked glycosylation near known sites of polyreactivity. We used the HIV-1-neutralizing antibody, VRC07, as a test case, since efforts to increase VRC07 potency at three spatially distinct sites resulted in enhanced polyreactivity. The addition of N-linked glycans proximal to the polyreactivity-enhancing mutations at each of the spatially distinct sites resulted in reduced antibody polyreactivity as measured by (i) anti-cardiolipin ELISA, (ii) Luminex AtheNA Multi-Lyte ANA binding, and (iii) HEp-2 cell staining. The reduced polyreactivity trended with increased antibody concentration over time in mice, but not with improved overall protein stability as measured by differential scanning calorimetry. Moreover, glycan proximity to the site of polyreactivity appeared to be a critical factor. The results provide evidence that antibody polyreactivity can result from local, rather than global, features of an antibody and that addition of N-linked glycosylation can be an effective approach to reducing antibody polyreactivity., (© 2015 The Protein Society.) more...