Bispecific antibodies combine breadth, potency, and avidity of parental antibodies to neutralize sarbecoviruses.

SARS-CoV-2 variants evade current monoclonal antibody therapies. Bispecific antibodies (bsAbs) combine the specificities of two distinct antibodies taking advantage of the avidity and synergy provided by targeting different epitopes. Here we used controlled Fab-arm exchange to produce bsAbs that neutralize SARS-CoV and SARS-CoV-2 variants, including Omicron and its subvariants, by combining potent SARS-CoV-2-specific neutralizing antibodies with broader antibodies that also neutralize SARS-CoV. We demonstrated that the parental antibodies rely on avidity for neutralization using bsAbs containing one irrelevant Fab arm. Using mass photometry to measure the formation of antibody:spike complexes, we determined that bsAbs increase binding stoichiometry compared to corresponding cocktails, without a loss of binding affinity. The heterogeneous binding pattern of bsAbs to spike, observed by negative-stain electron microscopy and mass photometry provided evidence for both intra- and inter-spike crosslinking. This study highlights the utility of cross-neutralizing antibodies for designing bivalent agents to combat circulating and future SARS-like coronaviruses.

Differences in IgG autoantibody Fab glycosylation across autoimmune diseases.

BACKGROUND: Increased prevalence of autoantibody Fab glycosylation has been demonstrated for several autoimmune diseases. OBJECTIVES: To study whether elevated Fab glycosylation is a common feature of autoimmunity, this study investigated Fab glycosylation levels on serum IgG and its subclasses for autoantibodies associated with a range of different B cell-mediated autoimmune diseases, including rheumatoid arthritis, myasthenia gravis subtypes, pemphigus vulgaris, antineutrophil cytoplasmic antibody-associated vasculitis, systemic lupus erythematosus, anti-glomerular basement membrane glomerulonephritis, thrombotic thrombocytopenic purpura, and Guillain-Barré syndrome. METHODS: The level of Fab glycosylated IgG antibodies was assessed by lectin affinity chromatography and autoantigen-specific immunoassays. RESULTS: In 6 of 10 autoantibody responses, in 5 of 8 diseases, the investigators found increased levels of Fab glycosylation on IgG autoantibodies that varied from 86% in rheumatoid arthritis to 26% in systemic lupus erythematosus. Elevated autoantibody Fab glycosylation was not restricted to IgG4, which is known to be prone to Fab glycosylation, but was also present in IgG1. When autoimmune diseases with a chronic disease course were compared with more acute autoimmune illnesses, increased Fab glycosylation was restricted to the chronic diseases. As a proxy for chronic autoantigen exposure, the investigators determined Fab glycosylation levels on antibodies to common latent herpes viruses, as well as to glycoprotein 120 in individuals who are chronically HIV-1-infected. Immunity to these viral antigens was not associated with increased Fab glycosylation levels, indicating that chronic antigen-stimulation as such does not lead to increased Fab glycosylation levels. CONCLUSIONS: These data indicate that in chronic but not acute B cell-mediated autoimmune diseases, disease-specific autoantibodies are enriched for Fab glycans.

Corrigendum: Anti-HIV-1 nanobody-IgG1 constructs with improved neutralization potency and the ability to mediate Fc effector functions.

[This corrects the article DOI: 10.3389/fimmu.2022.893648.].

Lassa virus glycoprotein nanoparticles elicit neutralizing antibody responses and protection.

The Lassa virus is endemic in parts of West Africa, and it causes hemorrhagic fever with high mortality. The development of a recombinant protein vaccine has been hampered by the instability of soluble Lassa virus glycoprotein complex (GPC) trimers, which disassemble into monomeric subunits after expression. Here, we use two-component protein nanoparticles consisting of trimeric and pentameric subunits to stabilize GPC in a trimeric conformation. These GPC nanoparticles present twenty prefusion GPC trimers on the surface of an icosahedral particle. Cryo-EM studies of GPC nanoparticles demonstrated a well-ordered structure and yielded a high-resolution structure of an unliganded GPC. These nanoparticles induced potent humoral immune responses in rabbits and protective immunity against the lethal Lassa virus challenge in guinea pigs. Additionally, we isolated a neutralizing antibody that mapped to the putative receptor-binding site, revealing a previously undefined site of vulnerability. Collectively, these findings offer potential approaches to vaccine and therapeutic design for the Lassa virus.

A public antibody class recognizes an S2 epitope exposed on open conformations of SARS-CoV-2 spike.

Delineating the origins and properties of antibodies elicited by SARS-CoV-2 infection and vaccination is critical for understanding their benefits and potential shortcomings. Therefore, we investigate the SARS-CoV-2 spike (S)-reactive B cell repertoire in unexposed individuals by flow cytometry and single-cell sequencing. We show that ∼82% of SARS-CoV-2 S-reactive B cells harbor a naive phenotype, which represents an unusually high fraction of total human naive B cells (∼0.1%). Approximately 10% of these naive S-reactive B cells share an IGHV1-69/IGKV3-11 B cell receptor pairing, an enrichment of 18-fold compared to the complete naive repertoire. Following SARS-CoV-2 infection, we report an average 37-fold enrichment of IGHV1-69/IGKV3-11 B cell receptor pairing in the S-reactive memory B cells compared to the unselected memory repertoire. This class of B cells targets a previously undefined non-neutralizing epitope on the S2 subunit that becomes exposed on S proteins used in approved vaccines when they transition away from the native pre-fusion state because of instability. These findings can help guide the improvement of SARS-CoV-2 vaccines.

Anti-HIV-1 Nanobody-IgG1 Constructs With Improved Neutralization Potency and the Ability to Mediate Fc Effector Functions.

The most effective treatment for HIV-1, antiretroviral therapy, suppresses viral replication and averts the disease from progression. Nonetheless, there is a need for alternative treatments as it requires daily administration with the possibility of side effects and occurrence of drug resistance. Broadly neutralizing antibodies or nanobodies targeting the HIV-1 envelope glycoprotein are explored as alternative treatment, since they mediate viral suppression and contribute to the elimination of virus-infected cells. Besides neutralization potency and breadth, Fc-mediated effector functions of bNAbs also contribute to the in vivo efficacy. In this study multivalent J3, 2E7 and 1F10 anti-HIV-1 broadly neutralizing nanobodies were generated to improve neutralization potency and IgG1 Fc fusion was utilized to gain Fc-mediated effector functions. Bivalent and trivalent nanobodies, coupled using long glycine-serine linkers, showed increased binding to the HIV-1 Env and enhanced neutralization potency compared to the monovalent variant. Fusion of an IgG1 Fc domain to J3 improved neutralization potency compared to the J3-bihead and restored Fc-mediated effector functions such as antibody-dependent cellular phagocytosis and trogocytosis, and natural killer cell activation. Due to their neutralization breadth and potency and their ability to induce effector functions these nanobody-IgG1 constructs may prove to be valuable towards alternative HIV-1 therapies.