Biology subjects

Bonsignori, M.

Publications and source records attributed to Bonsignori, M..

10 recordsLinked to original sources

bioRxiv2026

Sub-neutralizing concentrations of Zika virus IgM monoclonal antibodies reduce IgG-mediated antibody-dependent enhancement of infectivity.

Zika virus (ZIKV) is an arthropod-borne flavivirus endemic to Latin America and Africa for which IgG-mediated antibody-dependent enhancement of infectivity (ADE) is a phenomenon of concern. The interplay dynamics between flavivirus-specific antibodies of the IgG and IgM isotypes are mostly unknown. Here, we used DH1017.IgM, a previously described human-derived, pentameric, ultrapotent neutralizing ZIKV IgM monoclonal antibody (mAb) and a recombinantly produced IgM version of neutralizing EDE1 mAb C8 (C8.IgM) to assess if IgM antibodies can interfere with IgG-mediated ADE in vitro. Both mAbs consistently reduced IgG-mediated ADE across a panel of ZIKV-binding IgG mAbs in a dose-dependent manner. ADE mitigation was achieved at DH1017.IgM sub-neutralizing concentrations. C8.IgM also mitigated IgG-mediated ADE against the whole panel, demonstrating generalizability. Finally, DH1017.IgM confirmed inhibition of ADE at sub-neutralizing concentrations in sera of ZIKV-infected individuals. In conclusion, mAbs of the IgM isotype may potently counter the adverse effects of IgG-mediated ADE.

immunology↗

bioRxiv2024

HIV-1 neutralizing antibodies in SHIV-infected macaques recapitulate structurally divergent modes of human V2 apex recognition with a single D gene

Broadly neutralizing antibodies targeting the V2 apex of the HIV-1 envelope trimer are among the most common specificities elicited in HIV-1-infected humans and simian-human immunodeficiency virus (SHIV)-infected macaques. To gain insight into the prevalent induction of these antibodies, we isolated and characterized 11 V2 apex-directed neutralizing antibody lineages from SHIV-infected rhesus macaques. Remarkably, all SHIV-induced V2 apex lineages were derived from reading frame two of the rhesus DH3-15*01 gene. Cryo-EM structures of envelope trimers in complex with antibodies from nine rhesus lineages revealed modes of recognition that mimicked three canonical human V2 apex-recognition modes. Notably, amino acids encoded by DH3-15*01 played divergent structural roles, inserting into a hole at the trimer apex, H-bonding to an exposed strand, or forming part of a loop scaffold. Overall, we identify a DH3-15*01-signature for rhesus V2 apex broadly neutralizing antibodies and show that highly selected genetic elements can play multiple roles in antigen recognition. HighlightsO_LIIsolated 11 V2 apex-targeted HIV-neutralizing lineages from 10 SHIV-infected Indian-origin rhesus macaques C_LIO_LICryo-EM structures of Fab-Env complexes for nine rhesus lineages reveal modes of recognition that mimic three modes of human V2 apex antibody recognition C_LIO_LIAll SHIV-elicited V2 apex lineages, including two others previously published, derive from the same DH3-15*01 gene utilizing reading frame two C_LIO_LIThe DH3-15*01 gene in reading frame two provides a necessary, but not sufficient, signature for V2 apex-directed broadly neutralizing antibodies C_LIO_LIStructural roles played by DH3-15*01-encoded amino acids differed substantially in different lineages, even for those with the same recognition mode C_LIO_LIPropose that the anionic, aromatic, and extended character of DH3-15*01 in reading frame two provides a selective advantage for V2 apex recognition compared to B cells derived from other D genes in the naive rhesus repertoire C_LIO_LIDemonstrate that highly selected genetic elements can play multiple roles in antigen recognition, providing a structural means to enhance recognition diversity C_LI

immunology↗

bioRxiv2022

Mutation-Guided Vaccine Design: A Strategy for Developing Boosting Immunogens for HIV Broadly Neutralizing Antibody Induction

A major goal of HIV-1 vaccine development is induction of broadly neutralizing antibodies (bnAbs). While success has been achieved in initiating bnAb B cell lineages, design of boosting immunogens that select for bnAb B cell receptors with improbable mutations required for bnAb affinity maturation remains difficult. Here we demonstrate a process for designing boosting immunogens for a V3-glycan bnAb B cell lineage. The immunogens induced affinity-matured antibodies by selecting for functional improbable mutations in bnAb precursor knock-in mice. Moreover, we show similar success in prime and boosting with nucleoside-modified mRNA-encoded HIV-1 envelope trimer immunogens, with improved selection by mRNA immunogens of improbable mutations required for bnAb binding to key envelope glycans. These results demonstrate the ability of both protein and mRNA prime-boost immunogens for selection of rare B cell lineage intermediates with neutralizing breadth after bnAb precursor expansion, a key proof-of concept and milestone towards development of an HIV vaccine. One-Sentence SummaryA vaccine strategy for selecting key rare antibody mutations is shown to induce HIV broadly neutralizing antibodies in mice.

immunology↗

bioRxiv2021

Zika virus-specific IgM elicited during pregnancy exhibits ultrapotent neutralization

Congenital Zika virus (ZIKV) infection results in neurodevelopmental deficits in up to 14% of infants born to ZIKV-infected mothers. Neutralizing antibodies are a critical component of protective immunity. Here, we demonstrate that plasma IgM responses contribute to ZIKV immunity in pregnancy, mediating neutralization up to three months post symptoms. From a ZIKV-infected pregnant woman, we established a B cell line secreting a pentameric ZIKV-specific IgM (DH1017.IgM) that exhibited ultrapotent ZIKV neutralization dependent on the IgM isotype. DH1017.IgM targets a novel envelope dimer epitope within Domain II. The arrangement of this epitope on the virion is compatible with concurrent engagement of all ten antigen-binding sites of DH1017.IgM, a solution not achievable by IgG antibodies. DH1017.IgM protected against lethal ZIKV challenge in mice. Our findings identify a unique role of antibodies of the IgM isotype in protection against ZIKV and posit DH1017.IgM as a safe and effective candidate immunoprophylactic, particularly during pregnancy. Key pointsO_LIPlasma IgM contributes to early ZIKV neutralization during pregnancy C_LIO_LIUltrapotent neutralization by pentameric DH1017.IgM mAb depends on isotype C_LIO_LIDH1017.IgM can engage all binding sites concurrently through different angles of approach C_LIO_LIDH1017.IgM protects mice against lethal ZIKV challenge C_LI

immunology↗

bioRxiv2021

Ability of nucleoside-modified mRNA to encode HIV-1 envelope trimer nanoparticles

The success of nucleoside-modified mRNAs in lipid nanoparticles (mRNA-LNP) as COVID-19 vaccines heralded a new era of vaccine development. For HIV-1, multivalent envelope (Env) trimer protein nanoparticles are superior immunogens compared to trimers alone for priming of broadly neutralizing antibody (bnAb) B cell lineages. The successful expression of complex multivalent nanoparticle immunogens with mRNAs has not been demonstrated. Here we show that mRNAs can encode antigenic Env trimers on ferritin nanoparticles that initiate bnAb precursor B cell expansion and induce serum autologous tier 2 neutralizing activity in bnAb precursor VH + VL knock-in mice. Next generation sequencing demonstrated acquisition of critical mutations, and monoclonal antibodies that neutralized heterologous HIV-1 isolates were isolated. Thus, mRNA- LNP can encode complex immunogens and are of use in design of germline-targeting and sequential boosting immunogens for HIV-1 vaccine development.

immunology↗

bioRxiv2021

Rapid selection of HIV envelopes that bind to neutralizing antibody B cell lineage members with functional improbable mutations

Elicitation of broadly neutralizing antibodies (bnAbs) by an HIV vaccine will involve priming the immune system to activate antibody precursors, followed by boosting immunizations to select for antibodies with functional features required for neutralization breadth. The higher the number of acquired mutations necessary for function, the more convoluted are the antibody developmental pathways. HIV bnAbs acquire a large number of somatic mutations, but not all mutations are functionally important. Here we identified a minimal subset of mutations sufficient for the function of the naturally occurring V3-glycan bnAb DH270.6. Using antibody library screening, candidate envelope immunogens that interacted with DH270.6-like antibodies containing this set of key mutations were identified and selected in vitro. Our results demonstrate that less complex B cell evolutionary pathways than those naturally observed exist for the induction of HIV bnAbs by vaccination, and establish rational approaches to identify boosting sequential envelope candidate immunogens.

immunology↗

bioRxiv2020

Recapitulation of HIV-1 Env-Antibody Coevolution in Macaques Leading to Neutralization Breadth

Neutralizing antibodies elicited by HIV-1 coevolve with viral Envs in distinctive patterns, in some cases acquiring substantial breadth. Here we show that primary HIV-1 Envs, when expressed by simian-human immunodeficiency viruses in rhesus macaques, elicited patterns of Env-antibody coevolution strikingly similar to those in humans. This included conserved immunogenetic, structural and chemical solutions to epitope recognition and precise Env-amino acid substitutions, insertions and deletions leading to virus persistence. The structure of one rhesus antibody, capable of neutralizing 49% of a 208-strain panel, revealed a V2-apex mode of recognition like that of human bNAbs PGT145/PCT64-35M. Another rhesus antibody bound the CD4-binding site by CD4 mimicry mirroring human bNAbs 8ANC131/CH235/VRC01. Virus-antibody coevolution in macaques can thus recapitulate developmental features of human bNAbs, thereby guiding HIV-1 immunogen design. One sentence summaryVirus-antibody coevolution in rhesus macaques recapitulates developmental features of human antibodies.

immunology↗

bioRxiv2020

Fab-dimerized glycan-reactive antibodies neutralize HIV and are prevalent in humans and rhesus macaques

SummaryThe HIV-1 envelope (Env) is comprised by mass of over 50% glycans. A goal of HIV-1 vaccine development is the induction of Env glycan-reactive broadly neutralizing antibodies (bnAbs). The 2G12 bnAb recognizes an Env glycan cluster using a unique variable heavy (VH) domain-swapped conformation that results in fragment antigen-binding (Fab) dimerization. Here we describe Fab-dimerized glycan (FDG)-reactive antibodies without VH-swapped domains from simian-human immunodeficiency virus (SHIV)-infected macaques that neutralized heterologous HIV-1 isolates. FDG precursors were boosted by vaccination in macaques, and were present in HIV-1-naïve humans with an average estimated frequency of one per 340,000 B cells. These data demonstrate frequent HIV-1 Env glycan-reactive bnAb B cell precursors in macaques and humans and reveal a novel strategy for their induction by vaccination.HighlightsDiscovery of Fab-dimerized HIV-1 glycan-reactive antibodies with a non-domain-swapped architectureFab-dimerized antibodies neutralize heterologous HIV-1 isolates.Antibodies with this architecture can be elicited by vaccination in macaques.Fab-dimerized antibodies are found in HIV-1 naïve humans.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2019

Antibody feedback limits the expansion of cognate memory B cells but drives the diversification of vaccine-induced antibody responses

Generating sufficient antibody to block infection is a key challenge for vaccines against malaria. Here we show that antibody titres to a key target, the repeat region of the Plasmodium falciparum circumsporozoite protein (PfCSP), plateaued after two immunizations in a clinical trial of the radiation-attenuated sporozoite vaccine. To understand the mechanisms limiting vaccine responsiveness, we developed Ig-knockin mice with elevated numbers of PfCSP-binding B cells. We determined that recall responses were inhibited by antibody feedback via epitope masking of the immunodominant PfCSP repeat region. Importantly, the amount of antibody that prevents boosting is below the amount of antibody required for protection. Finally, while antibody feedback limited responses to the PfCSP-repeat region in vaccinated volunteers, potentially protective subdominant responses to C-terminal regions did expand with subsequent boosts. These data suggest that antibody feedback drives the diversification of immune responses and that vaccination for malaria will require the targeting of multiple antigens.

immunology↗

bioRxiv2018

Functional Improbable Antibody Mutations Critical for HIV Broadly Neutralizing Antibody Development

HIV-1 broadly neutralizing antibodies (bnAbs) require high levels of activation-induced cytidine deaminase (AID) catalyzed somatic mutations for optimal neutralization potency. Probable mutations occur at sites of frequent AID activity, while improbable mutations occur where AID activity is infrequent. One bottleneck for induction of bnAbs is the evolution of viral envelopes (Envs) that can select bnAb B cell receptors (BCR) with improbable mutations. Here we define the probability of bnAb mutations and demonstrate the functional significance of key improbable mutations in three bnAb B cell lineages. We show that bnAbs are enriched for improbable mutations, implying their elicitation will be critical for successful vaccine induction of potent bnAb B cell lineages. We outline a mutation-guided vaccine strategy for identification of Envs that can select B cells with BCRs with key improbable mutations required for bnAb development. Our analysis suggests that through generations of viral escape, Env trimers evolved to hide in low probability regions of antibody sequence space.

immunology↗