A single mutation in dairy cow-associated H5N1 viruses increases receptor binding breadth.

Clade 2.3.4.

Isolation of Rare Antigen-Specific Memory B Cells via Antigen Tetramers.

Immunological memory, which sets the foundation for the adaptive immune response, plays a key role in disease protection and prevention. Obtaining a deeper understanding of the mechanisms underlying this phenomenon can aide in research aimed to improve vaccines and therapies. Memory B cells (MBCs) are a fundamental component of immunological memory but can exist in rare populations that prove challenging to study.

Immunity by AS03ation: The natural adjuvantage.

Humans do not respond equally to vaccination. To investigate why, Mulè et al. developed a multimodal framework and found that high responders after unadjuvanted influenza vaccination exist in a naturally adjuvanted state, mimicking innate immunophenotypes following AS03-adjuvanted vaccination.

An integrated technology for quantitative wide mutational scanning of human antibody Fab libraries.

Antibodies are engineerable quantities in medicine. Learning antibody molecular recognition would enable the in silico design of high affinity binders against nearly any proteinaceous surface. Yet, publicly available experiment antibody sequence-binding datasets may not contain the mutagenic, antigenic, or antibody sequence diversity necessary for deep learning approaches to capture molecular recognition.

Immunization-induced antigen archiving enhances local memory CD8+ T cell responses following an unrelated viral infection.

Antigens from viruses or immunizations can persist or are archived in lymph node stromal cells such as lymphatic endothelial cells (LEC) and fibroblastic reticular cells (FRC). Here, we find that, during the time frame of antigen archiving, LEC apoptosis caused by a second, but unrelated, innate immune stimulus such as vaccina viral infection or CpG DNA administration resulted in cross-presentation of archived antigens and boosted memory CD8 + T cells specific to the archived antigen. In contrast to "bystander" activation associated with unrelated infections, the memory CD8 + T cells specific to the archived antigen from the immunization were significantly higher than memory CD8 + T cells of a different antigen specificity.

An integrated technology for quantitative wide mutational scanning of human antibody Fab libraries.

Antibodies are engineerable quantities in medicine. Learning antibody molecular recognition would enable the design of high affinity binders against nearly any proteinaceous surface. Yet, publicly available experiment antibody sequence-binding datasets may not contain the mutagenic, antigenic, or antibody sequence diversity necessary for deep learning approaches to capture molecular recognition.

Biochemical and biophysical characterization of natural polyreactivity in antibodies.

To become specialized binders, antibodies undergo a process called affinity maturation to maximize their binding affinity. Despite this process, some antibodies retain low-affinity binding to diverse epitopes in a phenomenon called polyreactivity. Here we seek to understand the molecular basis of this polyreactivity in antibodies.

Defining and Studying B Cell Receptor and TCR Interactions.

BCRs (Abs) and TCRs (or adaptive immune receptors [AIRs]) are the means by which the adaptive immune system recognizes foreign and self-antigens, playing an integral part in host defense, as well as the emergence of autoimmunity. Importantly, the interaction between AIRs and their cognate Ags defies a simple key-in-lock paradigm and is instead a complex many-to-many mapping between an individual's massively diverse AIR repertoire, and a similarly diverse antigenic space. Understanding how adaptive immunity balances specificity with epitopic coverage is a key challenge for the field, and terms such as broad specificity, cross-reactivity, and polyreactivity remain ill-defined and are used inconsistently.

Female Antibodies Go the Distance against Influenza Viruses.

Females have long been described to generate superior humoral immune responses relative to those in males. In the article by Ursin et al. (R.

Librator: a platform for the optimized analysis, design, and expression of mutable influenza viral antigens.

Artificial mutagenesis and protein engineering have laid the foundation for antigenic characterization and universal vaccine design for influenza viruses. However, many methods used in this process require manual sequence editing and protein expression, limiting their efficiency and utility in high-throughput applications. More streamlined in silico tools allowing researchers to properly analyze and visualize influenza viral protein sequences with accurate nomenclature are necessary to improve antigen design and productivity.

Broadly neutralizing antibodies target a haemagglutinin anchor epitope.

Broadly neutralizing antibodies that target epitopes of haemagglutinin on the influenza virus have the potential to provide near universal protection against influenza virus infection. However, viral mutants that escape broadly neutralizing antibodies have been reported. The identification of broadly neutralizing antibody classes that can neutralize viral escape mutants is critical for universal influenza virus vaccine design.

Cross-Neutralization of Emerging SARS-CoV-2 Variants of Concern by Antibodies Targeting Distinct Epitopes on Spike.

Several severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have arisen that exhibit increased viral transmissibility and partial evasion of immunity induced by natural infection and vaccination. To address the specific antibody targets that were affected by recent viral variants, we generated 43 monoclonal antibodies (mAbs) from 10 convalescent donors that bound three distinct domains of the SARS-CoV-2 spike. Viral variants harboring mutations at K417, E484, and N501 could escape most of the highly potent antibodies against the receptor binding domain (RBD).

Bridging the B Cell Gap: Novel Technologies to Study Antigen-Specific Human B Cell Responses.

The generation of high affinity antibodies is a crucial aspect of immunity induced by vaccination or infection. Investigation into the B cells that produce these antibodies grants key insights into the effectiveness of novel immunogens to induce a lasting protective response against endemic or pandemic pathogens, such as influenza viruses, human immunodeficiency virus, or severe acute respiratory syndrome coronavirus-2. However, humoral immunity has largely been studied at the serological level, limiting our knowledge on the specificity and function of B cells recruited to respond to pathogens.

Cross neutralization of emerging SARS-CoV-2 variants of concern by antibodies targeting distinct epitopes on spike.

Several severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have arisen that exhibit increased viral transmissibility and partial evasion of immunity induced by natural infection and vaccination. To address the specific antibody targets that were affected by recent viral variants, we generated 43 monoclonal antibodies (mAbs) from 10 convalescent donors that bound three distinct domains of the SARS-CoV-2 spike. Viral variants harboring mutations at K417, E484 and N501 could escape most of the highly potent antibodies against the receptor binding domain (RBD).

An Egg-Derived Sulfated -Acetyllactosamine Glycan Is an Antigenic Decoy of Influenza Virus Vaccines.

Influenza viruses grown in eggs for the purposes of vaccine generation often acquire mutations during egg adaptation or possess different glycosylation patterns than viruses circulating among humans. Here, we report that seasonal influenza virus vaccines possess an egg-derived glycan that is an antigenic decoy, with egg-binding MAbs reacting with a sulfated -acetyllactosamine (LacNAc). Half of subjects that received an egg-grown vaccine mounted an antibody response against this egg-derived antigen.

First exposure to the pandemic H1N1 virus induced broadly neutralizing antibodies targeting hemagglutinin head epitopes.

Broadly neutralizing antibodies are critical for protection against both drifted and shifted influenza viruses. Here, we reveal that first exposure to the 2009 pandemic H1N1 influenza virus recalls memory B cells that are specific to the conserved receptor-binding site (RBS) or lateral patch epitopes of the hemagglutinin (HA) head domain. Monoclonal antibodies (mAbs) generated against these epitopes are broadly neutralizing against H1N1 viruses spanning 40 years of viral evolution and provide potent protection in vivo.

B Cell Responses against Influenza Viruses: Short-Lived Humoral Immunity against a Life-Long Threat.

Antibodies are critical for providing protection against influenza virus infections. However, protective humoral immunity against influenza viruses is limited by the antigenic drift and shift of the major surface glycoproteins, hemagglutinin and neuraminidase. Importantly, people are exposed to influenza viruses throughout their life and tend to reuse memory B cells from prior exposure to generate antibodies against new variants.

Profiling B cell immunodominance after SARS-CoV-2 infection reveals antibody evolution to non-neutralizing viral targets.

Dissecting the evolution of memory B cells (MBCs) against SARS-CoV-2 is critical for understanding antibody recall upon secondary exposure. Here, we used single-cell sequencing to profile SARS-CoV-2-reactive B cells in 38 COVID-19 patients. Using oligo-tagged antigen baits, we isolated B cells specific to the SARS-CoV-2 spike, nucleoprotein (NP), open reading frame 8 (ORF8), and endemic human coronavirus (HCoV) spike proteins.

Hemolysis-associated phosphatidylserine exposure promotes polyclonal plasmablast differentiation.

Antimalarial antibody responses are essential for mediating the clearance of Plasmodium parasite-infected RBCs from infected hosts. However, the rapid appearance of large numbers of plasmablasts in Plasmodium-infected hosts can suppress the development and function of durable humoral immunity. Here, we identify that the formation of plasmablast populations in Plasmodium-infected mice is mechanistically linked to both hemolysis-induced exposure of phosphatidylserine on damaged RBCs and inflammatory cues.

Influenza hemagglutinin-specific IgA Fc-effector functionality is restricted to stalk epitopes.

In this study, we utilized a panel of human immunoglobulin (Ig) IgA monoclonal antibodies isolated from the plasmablasts of eight donors after 2014/2015 influenza virus vaccination (Fluarix) to study the binding and functional specificities of this isotype. In this cohort, isolated IgA monoclonal antibodies were primarily elicited against the hemagglutinin protein of the H1N1 component of the vaccine. To compare effector functionalities, an H1-specific subset of antibodies targeting distinct epitopes were expressed as monomeric, dimeric, or secretory IgA, as well as in an IgG1 backbone.

Extrafollicular CD4 T cell-derived IL-10 functions rapidly and transiently to support anti-Plasmodium humoral immunity.

Immunity against malaria depends on germinal center (GC)-derived antibody responses that are orchestrated by T follicular helper (TFH) cells. Emerging data show that the regulatory cytokine IL-10 plays an essential role in promoting GC B cell responses during both experimental malaria and virus infections. Here we investigated the cellular source and temporal role of IL-10, and whether IL-10 additionally signals to CD4 T-cells to support anti-Plasmodium humoral immunity.

SARS-CoV-2 Infection Severity Is Linked to Superior Humoral Immunity against the Spike.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently causing a global pandemic. The antigen specificity of the antibody response mounted against this novel virus is not understood in detail. Here, we report that subjects with a more severe SARS-CoV-2 infection exhibit a larger antibody response against the spike and nucleocapsid protein and epitope spreading to subdominant viral antigens, such as open reading frame 8 and nonstructural proteins.