Polyreactivity of antibody molecules

Unique characteristics of autoantibodies targeting MET in patients with breast and lung cancer

The presence of B cells in tumors is correlated with favorable prognosis and efficient response to immunotherapy. While tumor-reactive antibodies have been detected in several cancer types, identifying antibodies that specifically target tumor-associated antigens remains a challenge. Here, we investigated the antibodies spontaneously elicited during breast and lung cancer that bind the cancer-associated antigen MET. We screened patients with lung (n = 25) and breast (n = 75) cancer and found that 13% had antibodies binding to both the recombinant ectodomain of MET, and the ligand binding part of MET, SEMA. MET binding in the breast cancer cohort was significantly correlated with hormone receptor-positive status. We further conducted immunoglobulin sequencing of peripheral MET-enriched B cells from 6 MET-reactive patients. The MET-enriched B cell repertoire was found to be polyclonal and prone to non-IgG1 subclass. Nine monoclonal antibodies were cloned and analyzed, and these exhibited MET binding, low thermostability, and high polyreactivity. Among these, antibodies 87B156 and 69B287 effectively bound to tumor cells and inhibited MET-expressing breast cancer cell lines. Overall, our data demonstrate that some patients with breast and lung cancer develop polyreactive antibodies that cross-react with MET. These autoantibodies have a potential contribution to immune responses against tumors.

New insights into antibody structure with implications for specificity, variable region restriction and isotype choice

The mystery surrounding the mechanisms by which antibody diversity is generated was largely settled in the 1970s by the discoveries of variable gene rearrangements and somatic hypermutation. This led to the paradigm that immunoglobulins are composed of two independent domains - variable and constant - that confer specificity and effector functions, respectively. However, since these early discoveries, there have been a series of observations of communication between the variable and constant domains that affects the overall antibody structure, which suggests that immunoglobulins have a more complex, interconnected functionality than previously thought. Another unresolved issue has been the genesis of 'restricted' antibody responses, characterized by the use of only a few variable region gene segments, despite the enormous potential combinatorial diversity. In this Perspective, we place recent findings related to immunoglobulin structure and function in the context of these immunologically important, historically unsolved problems to propose a new model for how antibody specificity is achieved without autoreactivity.

Persistent splenic-derived IgMs preferentially recognize factor VIII A2 and C2 domain epitopes but do not alter antibody production

BACKGROUND

The most significant treatment complication for patients with hemophilia A is the development of neutralizing immunoglobins (Igs) G, termed inhibitors, against factor VIII (FVIII), which prevent FVIII replacement therapy. Low titers of FVIII-specific IgMs have been identified in hemophilia A patients with and without inhibitors, as well as in healthy individuals. However, the duration and influence of IgMs on the immune response to FVIII remains unclear.

OBJECTIVES

To characterize the binding interactions of persistently secreted FVIII-specific IgMs in hemophilia A mice and assess their effect on IgG antibody development.

METHODS

Splenic-derived monoclonal antibodies (mAbs) from immunized FVIII knockout mice were isolated and purified using hybridoma technology. Binding interactions were assessed utilizing a novel fluid-phase enzyme-linked immunosorbent assay and computational modeling with High Ambiguity-Driven protein-protein DOCKing to account for weak IgM binding.

RESULTS

Sixteen porcine cross-reactive and noninhibitory FVIII-specific IgM mAbs were identified. RNA sequencing of FVIII-specific IgMs revealed 13 unique variable, diversity, and joining (VDJ)/variable and joining (VJ) sequences indicating derivation from 13 unique B cell clones. The IgMs demonstrated polyclonal and polyreactive binding to FVIII in vitro and in silico. Molecular docking studies with reconstructed IgM variable, diversity, and joining/variable and joining regions identified frequent IgM interactions with amino acid residues K376, T381, K437, R2215, or K2249 within the FVIII A2 and C2 domains. Injections of individual IgMs prior to FVIII exposure and co-injection of FVIII/IgM immune complexes did not affect de novo FVIII antibody production.

CONCLUSION

Persistent FVIII-specific IgMs are polyclonal but preferentially bind the A2 and C2 domains. FVIII/IgM immune complex formation does not significantly alter inhibitor development.

Contribution of long-lived plasma cells to antibody-mediated allograft rejection

Persistent alloantigens derived from allograft tissues can be recognized by the host's alloreactive immune system. This process enables cognate B cells to differentiate into plasma cells, which secrete donor-specific antibodies that are key drivers of antibody-mediated allograft rejection. A subset of these plasma cells can survive for extended periods in a suitable survival niche and mature into long-lived plasma cells (LLPCs), which are a cellular component of humoral memory. The current understanding of LLPCs is limited due to their scarcity, heterogeneity, and absence of unique markers. However, accumulating evidence indicates that LLPCs, unlike conventional short-lived plasma cells, can respond to extrinsic signals from their survival niches and can resist cell death associated with intracellular stress through cell-intrinsic mechanisms. Notably, they are refractory to traditional immunosuppressants and B cell depletion therapies. This resistance, coupled with their longevity, may explain why current treatments targeting antibody-mediated rejection are often ineffective. This review offers insights into the biology of LLPCs and discusses ongoing therapeutic trials that target LLPCs in the context of antibody-mediated allograft rejection.

Clones reactive to apoptotic cells and specific chemical adducts are prevalent among human thymic B cells

Introduction

Thymus resident B cells were described more than 40 years ago. In early human life, these cells are found predominantly in the medulla and overwhelmingly display an unswitched IgM+ phenotype. The reactivity of thymic IgM B cells, however, is still unclear.

Methods

Here, we generated 120 IgM-producing B cell clones from 3 separate thymus specimens obtained from infant, adolescent, and adult donors. Using flow cytometry and a unique high-dimensional ELISA platform, we investigated the clones' reactivity to apoptotic cells as well as to common chemical adducts exposed on modified amino acids and other macromolecules.

Results

Regardless of the age, approximately 30-40% of thymic IgM B cells reacted to apoptotic cells. Further, 30-40% displayed reactivity to at least one adduct, including malondialdehyde, Homocysteine, and NEDD 8. Four distinct reactivity patterns were identified through this profiling. Notably, a significant association was observed between reactivity to apoptotic cells, and to one or more adducts, suggesting that the same determinants were recognized in both assays. Additionally, thymic IgM B cells reactive to adducts were more likely to recognize intra-nuclear or intra-cytoplasmic structures in Hep-2 cells as revealed by immunofluorescence staining.

Conclusion/Discussion

Collectively, our findings suggest that thymic IgM B cells actively uptake apoptotic bodies and cellular debris in the medulla by binding specific chemical adducts. This mechanism could underpin their antigen-presenting function and further support their role in T-cell negative selection.

Antigen specificity affects analysis of natural antibodies

Natural antibodies are used to compare immune systems across taxa, to study wildlife disease ecology, and as selection markers in livestock breeding. These immunoglobulins are present prior to immune stimulation. They are described as having low antigen specificity or polyreactive binding and are measured by binding to self-antigens or novel exogenous proteins. Most studies use only one or two antigens to measure natural antibodies and ignore potential effects of antigen specificity in analyses. It remains unclear how different antigen-specific natural antibodies are related or how diversity among natural antibodies may affect analyses of these immunoglobulins. Using genetically distinct lines of chickens as a model system, we tested the hypotheses that (1) antigen-specific natural antibodies are independent of each other and (2) antigen specificity affects the comparison of natural antibodies among animals. We used blood cell agglutination and enzyme-linked immunosorbent assays to measure levels of natural antibodies binding to four antigens: (i) rabbit erythrocytes, (ii) keyhole limpet hemocyanin, (iii) phytohemagglutinin, or (iv) ovalbumin. We observed that levels of antigen specific natural antibodies were not correlated. There were significant differences in levels of natural antibodies among lines of chickens, indicating genetic variation for natural antibody production. However, line distinctions were not consistent among antigen specific natural antibodies. These data show that natural antibodies are a pool of relatively distinct immunoglobulins, and that antigen specificity may affect interpretation of natural antibody function and comparative immunology.

Evaluation of Immune Response to Mucosal Immunization with an Oral Probiotic-Based Vaccine in Mice: Potential for Prime-Boost Immunization against SARS-CoV-2

Following the conclusion of the COVID-19 pandemic, the persistent genetic variability in the virus and its ongoing circulation within the global population necessitate the enhancement of existing preventive vaccines and the development of novel ones. A while back, we engineered an orally administered probiotic-based vaccine, L3-SARS, by integrating a gene fragment that encodes the spike protein S of the SARS-CoV-2 virus into the genome of the probiotic strain E. faecium L3, inducing the expression of viral antigen on the surface of bacteria. Previous studies demonstrated the efficacy of this vaccine candidate in providing protection against the virus in Syrian hamsters. In this present study, utilizing laboratory mice, we assess the immune response subsequent to immunization via the gastrointestinal mucosa and discuss its potential as an initial phase in a two-stage vaccination strategy. Our findings indicate that the oral administration of L3-SARS elicits an adaptive immune response in mice. Pre-immunization with L3-SARS enhances and prolongs the humoral immune response following a single subcutaneous immunization with a recombinant S-protein analogous to the S-insert of the coronavirus in Enterococcus faecium L3.

Polyreactivity of antibodies from different B-cell subpopulations is determined by distinct sequence patterns of variable region

An antibody molecule that can bind to multiple distinct antigens is defined as polyreactive. In the present study, we performed statistical analyses to assess sequence correlates of polyreactivity of >600 antibodies cloned from different B-cell types of healthy humans. The data revealed several sequence patterns of variable regions of heavy and light immunoglobulin chains that determine polyreactivity. The most prominent identified patterns were increased number of basic amino acid residues, reduced frequency of acidic residues, increased number of aromatic and hydrophobic residues, and longer length of CDR L1. Importantly, our study revealed that antibodies isolated from different B-cell populations used distinct sequence patterns (or combinations of them) for polyreactive antigen binding. Furthermore, we combined the data from sequence analyses with molecular modeling of selected polyreactive antibodies and demonstrated that human antibodies can use multiple pathways for achieving antigen-binding promiscuity. These data reconcile some contradictions in the literature regarding the determinants of antibody polyreactivity. Moreover, our study demonstrates that the mechanism of polyreactivity of antibodies evolves during immune response and might be tailored to specific functional properties of different B-cell compartments. Finally, these data can be of use for efforts in the development and engineering of therapeutic antibodies.

Clonal redemption of B cells in cancer

Potentially self-reactive B cells constitute a large portion of the peripheral B cell repertoire in both mice and humans. Maintenance of autoreactive B cell populations could conceivably be detrimental to the host but their conservation throughout evolution suggests performance of a critical and beneficial immune function. We discuss herein how the process of clonal redemption may provide insight to preservation of an autoreactive B cell pool in the context of infection and autoimmunity. Clonal redemption refers to additional recombination or hypermutation events decreasing affinity for self-antigen, while increasing affinity for foreign antigens. We then review findings in murine models and human patients to consider whether clonal redemption may be able to provide tumor antigen-specific B cells and how this may or may not predispose patients to autoimmunity.

Mechanistic Insight into Poly-Reactivity of Immune Antibodies upon Acid Denaturation or Arginine Mutation in Antigen-Binding Regions

The poly-reactivity of antibodies is defined as their binding to specific antigens as well as to related proteins and also to unrelated targets. Poly-reactivity can occur in individual molecules of natural serum antibodies, likely due to their conformation flexibility, and, for therapeutic antibodies, it plays a critical role in their clinical development. On the one hand, it can enhance their binding to target antigens and cognate receptors, but, on the other hand, it may lead to a loss of antibody function by binding to off-target proteins. Notably, poly-reactivity has been observed in antibodies subjected to treatments with dissociating, destabilizing or denaturing agents, in particular acidic pH, a common step in the therapeutic antibody production process involving the elution of Protein-A bound antibodies and viral clearance using low pH buffers. Additionally, poly-reactivity can emerge during the affinity maturation in the immune system, such as the germinal center. This review delves into the underlying potential causes of poly-reactivity, highlighting the importance of conformational flexibility, which can be further augmented by the acid denaturation of antibodies and the introduction of arginine mutations into the complementary regions of antibody-variable domains. The focus is placed on a particular antibody's acid conformation, meticulously characterized through circular dichroism, differential scanning calorimetry, and sedimentation velocity analyses. By gaining a deeper understanding of these mechanisms, we aim to shed light on the complexities of antibody poly-reactivity and its implications for therapeutic applications.

Paper-based biosensors as point-of-care diagnostic devices for the detection of cancers: a review of innovative techniques and clinical applications

The development and rapid progression of cancer are major social problems. Medical diagnostic techniques and smooth clinical care of cancer are new necessities that must be supported by innovative diagnostic methods and technologies. Current molecular diagnostic tools based on the detection of blood protein markers are the most common tools for cancer diagnosis. Biosensors have already proven to be a cost-effective and accessible diagnostic tool that can be used where conventional laboratory methods are not readily available. Paper-based biosensors offer a new look at the world of analytical techniques by overcoming limitations through the creation of a simple device with significant advantages such as adaptability, biocompatibility, biodegradability, ease of use, large surface-to-volume ratio, and cost-effectiveness. In this review, we covered the characteristics of exosomes and their role in tumor growth and clinical diagnosis, followed by a discussion of various paper-based biosensors for exosome detection, such as dipsticks, lateral flow assays (LFA), and microfluidic paper-based devices (µPADs). We also discussed the various clinical studies on paper-based biosensors for exosome detection.

Broad responses to chemical adducts shape the natural antibody repertoire in early infancy

Natural antibodies are an integral part of innate humoral immunity yet their development and polyreactive nature are still enigmatic. Here, we show that characteristic monoclonal natural antibodies recognize common chemical moieties or adducts, supporting the view that polyreactive antibodies may often correspond to anti-adduct antibodies. We next examined the development of immunoglobulin M (IgM) and IgG to 81 ubiquitous adducts from birth to old age. Newborn IgM only reacted to a limited number of consensus determinants. This highly restricted neonatal repertoire abruptly diversified around 6 months of age through the development of antibodies to environmental antigens and age-driven epigenetic modifications. In contrast, the IgG repertoire was diverse across the entire life span. Our studies reveal an unrecognized component of humoral immunity directed to common adducts. These findings set the ground for further investigations into the role of anti-adduct B cell responses in homeostatic functions and pathological conditions.

Antibodies to Combat Fungal Infections: Development Strategies and Progress

The finding that some mAbs are antifungal suggests that antibody immunity may play a key role in the defense of the host against mycotic infections. The discovery of antibodies that guard against fungi is a significant advancement because it gives rise to the possibility of developing vaccinations that trigger protective antibody immunity. These vaccines might work by inducing antibody opsonins that improve the function of non-specific (such as neutrophils, macrophages, and NK cells) and specific (such as lymphocyte) cell-mediated immunity and stop or aid in eradicating fungus infections. The ability of antibodies to defend against fungi has been demonstrated by using monoclonal antibody technology to reconsider the function of antibody immunity. The next step is to develop vaccines that induce protective antibody immunity and to comprehend the mechanisms through which antibodies mediate protective effects against fungus.

Oxidized hemoglobin triggers polyreactivity and autoreactivity of human IgG via transfer of heme

Intravascular hemolysis occurs in diverse pathological conditions. Extracellular hemoglobin and heme have strong pro-oxidative and pro-inflammatory potentials that can contribute to the pathology of hemolytic diseases. However, many of the effects of extracellular hemoglobin and heme in hemolytic diseases are still not well understood. Here we demonstrate that oxidized hemoglobin (methemoglobin) can modify the antigen-binding characteristics of human immunoglobulins. Thus, incubation of polyclonal or some monoclonal human IgG in the presence of methemoglobin results in an appearance of binding reactivities towards distinct unrelated self-proteins, including the protein constituent of hemoglobin i.e., globin. We demonstrate that a transfer of heme from methemoglobin to IgG is indispensable for this acquisition of antibody polyreactivity. Our data also show that only oxidized form of hemoglobin have the capacity to induce polyreactivity of antibodies. Site-directed mutagenesis of a heme-sensitive human monoclonal IgG1 reveals details about the mechanism of methemoglobin-induced antigen-binding polyreactivity. Further here we assess the kinetics and thermodynamics of interaction of a heme-induced polyreactive human antibody with hemoglobin and myoglobin. Taken together presented data contribute to a better understanding of the functions of extracellular hemoglobin in the context of hemolytic diseases.

Binding of adenovirus species C hexon to prothrombin and the influence of hexon on vector properties in vitro and in vivo

The majority of adenovirus (Ad) vectors are based on human Ad type 5, which is a member of Ad species C. Species C also includes the closely-related types 1, 2, 6, 57 and 89. It is known that coagulation factors bind to Ad5 hexon and play a key role in the liver tropism of Ad5 vectors, but it is unclear how coagulation factors affect vectors derived from other species C Ads. We evaluated species C Ad vectors both in vitro and following intravenous injection in mice. To assess the impact of hexon differences, we constructed chimeric Ad5 vectors that contain the hexon hypervariable regions from other species C types, including vectors with hexon mutations that decreased coagulation factor binding. After intravenous injection into mice, vectors with Ad5 or Ad6 hexon had strong liver tropism, while vectors with chimeric hexon from other Ad types had weaker liver tropism due to inhibition by natural antibodies and complement. In addition, we discovered a novel ability of hexon to bind prothrombin, which is the most abundant coagulation factor in blood, and we found striking differences in the affinity of Ads for human, mouse and bovine coagulation factors. When compared to Ad5, vectors with non-Ad5 species C hexons had considerably higher affinity for both human and mouse prothrombin. Most of the vectors tested were strongly dependent on coagulation factors for liver transduction, but vectors with chimeric Ad6 hexon showed much less dependence on coagulation factors than other vectors. We found that in vitro neutralization experiments with mouse serum predicted in vivo behavior of Ad5 vectors, but in vitro experiments did not predict the in vivo behavior of vectors based on other Ad types. In sum, hexons from different human Ad species C viruses confer diverse properties on vectors, including differing abilities to target the liver.

Autoantibodies as Biomarker and Therapeutic Target in Systemic Sclerosis

Systemic sclerosis (SSc) is a rare connective tissue disorder characterized by immune dysregulation evoking the pathophysiological triad of inflammation, fibrosis and vasculopathy. In SSc, several alterations in the B-cell compartment have been described, leading to polyclonal B-cell hyperreactivity, hypergammaglobulinemia and autoantibody production. Autoreactive B cells and autoantibodies promote and maintain pathologic mechanisms. In addition, autoantibodies in SSc are important biomarkers for predicting clinical phenotype and disease progression. Autoreactive B cells and autoantibodies represent potentially promising targets for therapeutic approaches including B-cell-targeting therapies, as well as strategies for unselective and selective removal of autoantibodies. In this review, we present mechanisms of the innate immune system leading to the generation of autoantibodies, alterations of the B-cell compartment in SSc, autoantibodies as biomarkers and autoantibody-mediated pathologies in SSc as well as potential therapeutic approaches to target these.

Repertoire-scale measures of antigen binding

Antibodies and T cell receptors (TCRs) are the fundamental building blocks of adaptive immunity. Repertoire-scale functionality derives from their epitope-binding properties, just as macroscopic properties like temperature derive from microscopic molecular properties. However, most approaches to repertoire-scale measurement, including sequence diversity and entropy, are not based on antibody or TCR function in this way. Thus, they potentially overlook key features of immunological function. Here we present a framework that describes repertoires in terms of the epitope-binding properties of their constituent antibodies and TCRs, based on analysis of thousands of antibody-antigen and TCR-peptide-major-histocompatibility-complex binding interactions and over 400 high-throughput repertoires. We show that repertoires consist of loose overlapping classes of antibodies and TCRs with similar binding properties. We demonstrate the potential of this framework to distinguish specific responses vs. bystander activation in influenza vaccinees, stratify cytomegalovirus (CMV)-infected cohorts, and identify potential immunological "super-agers." Classes add a valuable dimension to the assessment of immune function.

Computational counterselection identifies nonspecific therapeutic biologic candidates

Effective biologics require high specificity and limited off-target binding, but these properties are not guaranteed by current affinity-selection-based discovery methods. Molecular counterselection against off targets is a technique for identifying nonspecific sequences but is experimentally costly and can fail to eliminate a large fraction of nonspecific sequences. Here, we introduce computational counterselection, a framework for removing nonspecific sequences from pools of candidate biologics using machine learning models. We demonstrate the method using sequencing data from single-target affinity selection of antibodies, bypassing combinatorial experiments. We show that computational counterselection outperforms molecular counterselection by performing cross-target selection and individual binding assays to determine the performance of each method at retaining on-target, specific antibodies and identifying and eliminating off-target, nonspecific antibodies. Further, we show that one can identify generally polyspecific antibody sequences using a general model trained on affinity data from unrelated targets with potential affinity for a broad range of sequences.

Reduction of therapeutic antibody self-association using yeast-display selections and machine learning

Self-association governs the viscosity and solubility of therapeutic antibodies in high-concentration formulations used for subcutaneous delivery, yet it is difficult to reliably identify candidates with low self-association during antibody discovery and early-stage optimization. Here, we report a high-throughput protein engineering method for rapidly identifying antibody candidates with both low self-association and high affinity. We find that conjugating quantum dots to IgGs that strongly self-associate (pH 7.4, PBS), such as lenzilumab and bococizumab, results in immunoconjugates that are highly sensitive for detecting other high self-association antibodies. Moreover, these conjugates can be used to rapidly enrich yeast-displayed bococizumab sub-libraries for variants with low levels of immunoconjugate binding. Deep sequencing and machine learning analysis of the enriched bococizumab libraries, along with similar library analysis for antibody affinity, enabled identification of extremely rare variants with co-optimized levels of low self-association and high affinity. This analysis revealed that co-optimizing bococizumab is difficult because most high-affinity variants possess positively charged variable domains and most low self-association variants possess negatively charged variable domains. Moreover, negatively charged mutations in the heavy chain CDR2 of bococizumab, adjacent to its paratope, were effective at reducing self-association without reducing affinity. Interestingly, most of the bococizumab variants with reduced self-association also displayed improved folding stability and reduced nonspecific binding, revealing that this approach may be particularly useful for identifying antibody candidates with attractive combinations of drug-like properties.Abbreviations: AC-SINS: affinity-capture self-interaction nanoparticle spectroscopy; CDR: complementarity-determining region; CS-SINS: charge-stabilized self-interaction nanoparticle spectroscopy; FACS: fluorescence-activated cell sorting; Fab: fragment antigen binding; Fv: fragment variable; IgG: immunoglobulin; QD: quantum dot; PBS: phosphate-buffered saline; V_H: variable heavy; V_L: variable light.

Immunogenetics of heteroclitic recognition of HLA-DQB1 55R eplet specificity by human alloantibody

Heteroclitic antibodies bind to a related antigen with higher affinity than to the immunizing antigen to which they were generated. This uncommon phenomenon is not well characterized for antibodies to HLA antigens. Here we analyzed allosera reactivity from two transplant recipients sensitized to mismatched donor alleles DQB1*06:01 and DQB1*06:02 respectively. Epitope analysis demonstrated the reactivity of both sera was restricted to DQB1*04, 05, and 06 alleles, with a specificity associated with the 55R eplet. Serum from one of these subjects (TE) was significantly more reactive with DQB1*04 alleles than the immunizing DQB1*06:01 or other alleles, a pattern not present in serum from the other patient. Antibody absorption/elution experiments using B cell lines expressing DQB1*06:01 or DQB1*04:02 alleles confirmed that the heteroclitic TE antibody eluted from cells carrying DQB1*06:01 was significantly more reactive with beads carrying the DQB1*04 alleles than with the DQB1*06 or other alleles. The significantly higher reactivity of the heteroclitic alloantibody with DQB1*04 specificity was explained structurally by variations of amino acid residues within 3.5 Å of 55R. These findings have important implications for the interpretation of DQ alloantibody cross-reactivity frequently observed in transplant recipients.

Polyreactivity and polyspecificity in therapeutic antibody development: risk factors for failure in preclinical and clinical development campaigns

Antibody-based drugs, which now represent the dominant biologic therapeutic modality, are used to modulate disparate signaling pathways across diverse disease indications. One fundamental premise that has driven this therapeutic antibody revolution is the belief that each monoclonal antibody exhibits exquisitely specific binding to a single-drug target. Herein, we review emerging evidence in antibody off-target binding and relate current key findings to the risk of failure in therapeutic development. We further summarize the current state of understanding of structural mechanisms underpining the different phenomena that may drive polyreactivity and polyspecificity, and highlight current thinking on how de-risking studies may be best implemented in the screening triage. We conclude with a summary of what we believe to be key observations in the field to date, and a call for the wider antibody research community to work together to build the tools needed to maximize our understanding in this nascent area.

Immunoaffinity Capillary Electrophoresis in the Era of Proteoforms, Liquid Biopsy and Preventive Medicine: A Potential Impact in the Diagnosis and Monitoring of Disease Progression

Over the years, multiple biomarkers have been used to aid in disease screening, diagnosis, prognosis, and response to therapy. As of late, protein biomarkers are gaining strength in their role for early disease diagnosis and prognosis in part due to the advancements in identification and characterization of a distinct functional pool of proteins known as proteoforms. Proteoforms are defined as all of the different molecular forms of a protein derived from a single gene caused by genetic variations, alternative spliced RNA transcripts and post-translational modifications. Monitoring the structural changes of each proteoform of a particular protein is essential to elucidate the complex molecular mechanisms that guide the course of disease. Clinical proteomics therefore holds the potential to offer further insight into disease pathology, progression, and prevention. Nevertheless, more technologically advanced diagnostic methods are needed to improve the reliability and clinical applicability of proteomics in preventive medicine. In this manuscript, we review the use of immunoaffinity capillary electrophoresis (IACE) as an emerging powerful diagnostic tool to isolate, separate, detect and characterize proteoform biomarkers obtained from liquid biopsy. IACE is an affinity capture-separation technology capable of isolating, concentrating and analyzing a wide range of biomarkers present in biological fluids. Isolation and concentration of target analytes is accomplished through binding to one or more biorecognition affinity ligands immobilized to a solid support, while separation and analysis are achieved by high-resolution capillary electrophoresis (CE) coupled to one or more detectors. IACE has the potential to generate rapid results with significant accuracy, leading to reliability and reproducibility in diagnosing and monitoring disease. Additionally, IACE has the capability of monitoring the efficacy of therapeutic agents by quantifying companion and complementary protein biomarkers. With advancements in telemedicine and artificial intelligence, the implementation of proteoform biomarker detection and analysis may significantly improve our capacity to identify medical conditions early and intervene in ways that improve health outcomes for individuals and populations.

Antinuclear Autoantibodies in Health: Autoimmunity Is Not a Synonym of Autoimmune Disease

The incidence of autoimmune diseases is increasing. Antinuclear antibody (ANA) testing is a critical tool for their diagnosis. However, ANA prevalence in healthy persons has increased over the last decades, especially among young people. ANA in health occurs in low concentrations, with a prevalence up to 50% in some populations, which demands a cutoff revision. This review deals with the origin and probable physiological or compensatory function of ANA in health, according to the concept of immunological clearance, theory of autoimmune regulation of cell functions, and the concept of functional autoantibodies. Considering ANA titers ≤1:320 as a serological marker of autoimmune diseases seems inappropriate. The role of anti-DFS70/LEDGFp75 autoantibodies is highlighted as a possible anti-risk biomarker for autoimmune rheumatic disorders. ANA prevalence in health is different in various regions due to several underlying causes discussed in the review, all influencing additive combinations according to the concept of the mosaic of autoimmunity. Not only are titers, but also HEp-2 IFA) staining patterns, such as AC-2, important. Accepting autoantibodies as a kind of bioregulator, not only the upper, but also the lower borders of their normal range should be determined; not only their excess, but also a lack of them or "autoimmunodeficiency" could be the reason for disorders.

The human natural anti-αGal antibody targets common pathogens by broad-spectrum polyreactivity

Naturally occurring antibodies are abundant in human plasma, but their importance in the defence against bacterial pathogens is unclear. We studied the role of the most abundant of such antibodies, the antibody against terminal galactose-α-1,3-galactose (anti-αGal), in the protection against pneumococcal infections (Streptococcus pneumonia). All known pneumococcal capsular polysaccharides lack terminal galactose-α-1,3-galactose, yet highly purified human anti-αGal antibody of the IgG class reacted with 48 of 91 pneumococcal serotypes. Anti-αGal was found to contain multiple antibody subsets that possess distinct specificities beyond their general reactivity with terminal galactose-α-1,3-galactose. These subsets in concert targeted a wide range of microbial polysaccharides. We found that anti-αGal constituted up to 40% of the total antibody reactivity to pneumococci in normal human plasma, that anti-αGal drives phagocytosis of pneumococci by human neutrophils and that the anti-αGal level was twofold lower in patients prone to pneumococcal infections compared with controls. Moreover, during a 48-year period in Denmark, the 48 anti-αGal-reactive serotypes caused fewer invasive pneumococcal infections (n = 10 927) than the 43 non-reactive serotypes (n = 18 107), supporting protection on the population level. Our findings explain the broad-spectrum pathogen reactivity of anti-αGal and support that these naturally occurring polyreactive antibodies contribute significantly to human protective immunity.

Purification and Immune Phenotyping of B-1 Cells from Body Cavities of Mice

B-1 cells are fetal-origin B lymphocytes with unique developmental and functional characteristics that can generate natural, polyreactive antibodies with important functions in tissue homeostasis and immune defense. While B-1 cell frequencies in bone marrow and secondary lymphoid tissues are low, relative high frequencies exist within peritoneal and pleural cavities of mice, including both CD5⁺ and CD5^- B-1 cells. These cells represent B-1 reservoirs that, when activated, migrate to lymphoid tissues to secrete antibodies and/or cytokines. Here, we outline efficient methods for the extraction and magnetic isolation of CD5⁺ B-1 cells from the peritoneal and pleural cavities as well as the separation and phenotypic characterization of CD5⁺ and CD5^- B-1 cells by flow cytometry.

Polyreactive antibodies as potential humoral biomarkers of host resistance to cystic echinococcosis

Polyreactive antibodies (pAb) bind to a broad range of unrelated structures, providing hosts with functional components able to rapidly recognize and protect against different pathogens. However, their roles against helminth parasites are still unexplored. Here, pAb profiles were analysed in cystic echinococcosis (CE), a zoonosis caused by the cestode Echinococcus granulosus sensu lato. Levels of anti-DNP (2,4-dinitrophenyl-hapten) antibodies were measured as a surrogate parameter of pAb in different biological settings. Firstly, levels of serum and peritoneal pAb were measured during early experimental secondary CE, using both high (Balb/c) and low (C57Bl/6) susceptible mouse strains. Serum pAb mostly differed in normal mice, being pAb levels of IgG subclasses with poor anti-parasite activities predominant in Balb/c animals. Conversely, peritoneal pAb isotypes/subclasses with efficient anti-parasite activities predominated in normal and infected C57Bl/6 mice. Secondly, sera from potentially resistant patients, susceptible individuals and healthy donors were analysed, showing higher pAb levels of the IgA and IgG-particularly IgG1-isotypes in potentially resistant individuals compared to control groups. Finally, since remarkable differences were observed in pAb profiles according to the intrinsic host susceptibility to the infection, we proposed here that pAb might be considered as potential humoral biomarkers for host resistance to CE.

A Two-Dimensional Affinity Capture and Separation Mini-Platform for the Isolation, Enrichment, and Quantification of Biomarkers and Its Potential Use for Liquid Biopsy

Biomarker detection for disease diagnosis, prognosis, and therapeutic response is becoming increasingly reliable and accessible. Particularly, the identification of circulating cell-free chemical and biochemical substances, cellular and subcellular entities, and extracellular vesicles has demonstrated promising applications in understanding the physiologic and pathologic conditions of an individual. Traditionally, tissue biopsy has been the gold standard for the diagnosis of many diseases, especially cancer. More recently, liquid biopsy for biomarker detection has emerged as a non-invasive or minimally invasive and less costly method for diagnosis of both cancerous and non-cancerous diseases, while also offering information on the progression or improvement of disease. Unfortunately, the standardization of analytical methods to isolate and quantify circulating cells and extracellular vesicles, as well as their extracted biochemical constituents, is still cumbersome, time-consuming, and expensive. To address these limitations, we have developed a prototype of a portable, miniaturized instrument that uses immunoaffinity capillary electrophoresis (IACE) to isolate, concentrate, and analyze cell-free biomarkers and/or tissue or cell extracts present in biological fluids. Isolation and concentration of analytes is accomplished through binding to one or more biorecognition affinity ligands immobilized to a solid support, while separation and analysis are achieved by high-resolution capillary electrophoresis (CE) coupled to one or more detectors. When compared to other existing methods, the process of this affinity capture, enrichment, release, and separation of one or a panel of biomarkers can be carried out on-line with the advantages of being rapid, automated, and cost-effective. Additionally, it has the potential to demonstrate high analytical sensitivity, specificity, and selectivity. As the potential of liquid biopsy grows, so too does the demand for technical advances. In this review, we therefore discuss applications and limitations of liquid biopsy and hope to introduce the idea that our affinity capture-separation device could be used as a form of point-of-care (POC) diagnostic technology to isolate, concentrate, and analyze circulating cells, extracellular vesicles, and viruses.

Homeostasis and regulation of autoreactive B cells

In contrast to the previous belief that autoreactive B cells are eliminated from the normal repertoire of B cells, many autoreactive B cells actually escape clonal deletion and develop into mature B cells. These autoreactive B cells in healthy individuals perform some beneficial functions in the host and are homeostatically regulated by regulatory T and B cells or other mechanisms to prevent autoimmune diseases. Autoreactive B-1 cells constitutively produce polyreactive natural antibodies for tissue homeostasis. Recently, autoreactive follicular B cells were reported to participate actively in the germinal center reaction. Furthermore, the selection and usefulness of autoreactive marginal zone (MZ) B cells found in autoimmune diseases are not well understood, although the repertoire of MZ B-cell receptors (BCRs) is presumed to be biased to detect bacterial antigens. In this review, we discuss the autoreactive B-cell populations among all three major B-cell subsets and their regulation in immune responses and diseases.

Aromatic Guanylhydrazones for the Control of Heme-Induced Antibody Polyreactivity

In a healthy immune repertoire, there exists a fraction of polyreactive antibodies that can bind to a variety of unrelated self- and foreign antigens. Apart from naturally polyreactive antibodies, in every healthy individual, there is a fraction of antibody that can gain polyreactivity upon exposure to porphyrin cofactor heme. Molecular mechanisms and biological significance of the appearance of cryptic polyreactivity are not well understood. It is believed that heme acts as an interfacial cofactor between the antibody and the newly recognized antigens. To further test this claim and gain insight into the types of interactions involved in heme binding, we herein investigated the influence of a group of aromatic guanylhydrazone molecules on the heme-induced antibody polyreactivity. From the analysis of SAR and the results of UV-vis absorbance spectroscopy, it was concluded that the most probable mechanism by which the studied molecules inhibit heme-mediated polyreactivity of the antibody is the direct binding to heme, thus preventing heme from binding to antibody and/or antigen. The inhibitory capacity of the most potent compounds was substantially higher than that of chloroquine, a well-known heme binder. Some of the guanylhydrazone molecules were able to induce polyreactivity of the studied antibody themselves, possibly by a mechanism similar to heme. Results described here point to the conclusion that heme indeed must bind to an antibody to induce its polyreactivity, and that both π-stacking interactions and iron coordination contribute to the binding affinity, while certain structures, such as guanylhydrazones, can interfere with these processes.

Interaction of adenovirus with antibodies, complement, and coagulation factors

Adenovirus (AdV) is one of the most widely used vectors for gene therapy and vaccine studies due to its excellent transduction efficiency, capacity for large transgenes, and high levels of gene expression. When administered intravascularly, the fate of AdV vectors is heavily influenced by interactions with host plasma proteins. Some plasma proteins can neutralize AdV, but AdV can also specifically bind plasma proteins that protect against neutralization and preserve activity. This review summarizes the plasma proteins that interact with AdV, including antibodies, complement, and vitamin K-dependent coagulation factors. We will also review the complex interactions of these plasma proteins with each other and with cellular proteins, as well as strategies for developing better AdV vectors that evade or manipulate plasma proteins.

Minding the gap: The impact of B-cell tolerance on the microbial antibody repertoire

B lymphocytes must respond to vast numbers of foreign antigens, including those of microbial pathogens. To do so, developing B cells use combinatorial joining of V-, D-, and J-gene segments to generate an extraordinarily diverse repertoire of B-cell antigen receptors (BCRs). Unsurprisingly, a large fraction of this initial BCR repertoire reacts to self-antigens, and these "forbidden" B cells are culled by immunological tolerance from mature B-cell populations. While culling of autoreactive BCRs mitigates the risk of autoimmunity, it also opens gaps in the BCR repertoire, which are exploited by pathogens that mimic the forbidden self-epitopes. Consequently, immunological tolerance, necessary for averting autoimmune disease, also acts to limit effective microbial immunity. In this brief review, we recount the evidence for the linkage of tolerance and impaired microbial immunity, consider the implications of this linkage for vaccine development, and discuss modulating tolerance as a potential strategy for strengthening humoral immune responses.

Detection of Salmonid IgM Specific to the Piscine Orthoreovirus Outer Capsid Spike Protein Sigma 1 Using Lipid-Modified Antigens in a Bead-Based Antibody Detection Assay

Bead-based multiplex immunoassays are promising tools for determination of the specific humoral immune response. In this study, we developed a multiplexed bead-based immunoassay for the detection of Atlantic salmon (Salmo salar) antibodies against Piscine orthoreovirus (PRV). Three different genotypes of PRV (PRV-1, PRV-2, and PRV-3) cause disease in farmed salmonids. The PRV outer capsid spike protein σ1 is predicted to be a host receptor binding protein and a target for neutralizing and protective antibodies. While recombinant σ1 performed poorly as an antigen to detect specific antibodies, N-terminal lipid modification of recombinant PRV-1 σ1 enabled sensitive detection of specific IgM in the bead-based assay. The specificity of anti-PRV-1 σ1 antibodies was confirmed by western blotting and pre-adsorption of plasma. Binding of non-specific IgM to beads coated with control antigens also increased after PRV infection, indicating a release of polyreactive antibodies. This non-specific binding was reduced by heat treatment of plasma. The same immunoassay also detected anti-PRV-3 σ1 antibodies from infected rainbow trout. In summary, a refined bead based immunoassay created by N-terminal lipid-modification of the PRV-1 σ1 antigen allowed sensitive detection of anti-PRV-1 and anti-PRV-3 antibodies from salmonids.

IgM Antibodies Can Access Cryptic Antigens Denied to IgG: Hypothesis on Novel Binding Mechanism

Antibodies are well-known protein mediators of immunity. IgM is the primordial member and the neglected sibling of the later-evolved and more proficient IgG in regard to their therapeutic and diagnostic use. Serendipitously, however, we found a paradox: While murine IgM antibodies specific for guanosine triphosphate (GTP) were able to recognize native guanylyl antigens found in primate or rat muscle tissues by immunofluorescence assays (which mimicked the auto-antibodies from autoimmune patients to skeletal or smooth muscle), the murine and human IgG counterparts failed. The results were replicated in cell-free direct binding assays using small latex microspheres decorated densely with GTP. The IgG antibodies could bind, however, if GTP was presented more spaciously on larger particles or as a univalent hapten. Accordingly, oligomerization of GTP (30-mer) destroyed the binding of the IgG antibodies but enhanced that of the IgMs in inhibition ELISA. We reason that, contrary to current belief, IgM does not bind in a lock-and-key manner like IgG. We hypothesize that whereas the intact and rigid antigen-binding site of IgG hinders the antibody from docking with antigens that are obstructed, in IgM, the two component polypeptides of the antigen-binding site can dissociate from each other and navigate individually through obstacles like the ancestral single-polypeptide antibodies found in sharks and camelids, both components eventually re-grouping around the antigen. We further speculate that polyreactive IgMs, which enigmatically bind to more than one type of antigen, use the same modus operandi. These findings call for a re-look at the clinical potential of IgM antibodies particularly in specific areas of cancer therapy, tissue pathology and vaccine design, where IgG antibodies have failed due to target inaccessibility.

T Cell-Dependent Maturation of Pathogen-Specific Igs in the Antrum of Chronically Helicobacter pylori-Infected Patients

Mucosal plasma cells (PC) and Ig production are essential to fend pathogens and to maintain mucosal homeostasis. In human Helicobacter pylori infection, mucosal PC express inducible NO synthase (iNOS), which positively correlates with clearance of experimental human infection. To characterize Ig genes and specificities of antral mucosal iNOS⁺ and iNOS^- PC in H. pylori infection, we sequenced rearranged Ig genes from single cell-sorted PC from biopsy specimens of chronically infected patients and analyzed them with respect to their molecular features. The binding specificity of individual PC's Ig was determined following recombinant expression. We identified high rates of somatic hypermutations, especially targeting RGYW/WRCY hotspot motifs in the individual Ig genes, indicating T cell-dependent maturation. For seven of 14 recombinantly expressed Ig, Ag specificity could be determined. Two clones reacted to H. pylori proteins, and five were found to be polyreactive against LPSs, dsDNA, and ssDNA. All specific Ig originated from iNOS⁺ PC. H. pylori-specific Ig are encoded by V and J family genes previously shown to be also used in rearranged Ig loci of MALT B cell lymphomas. In summary, mucosal iNOS⁺ PC producing H. pylori-specific Ig accumulate in infection and appear to be a product of T cell-dependent B cell maturation. Moreover, the Ig's molecular features partly resembled that of MALT B cell lymphoma Ig genes, suggestive of a mechanism in which a progressive molecular evolution of pathogen-specific B cells to MALT B cell lymphoma occurs.

Factors of early protective action of live influenza vaccine combined with recombinant bacterial polypeptides against homologous and heterologous influenza infection

We are developing an associated vaccine based on live influenza vaccine (LAIV) and streptococcal recombinant peptides. The recombinant group B streptococcus (GBS) peptides P6 and ScaAB demonstrated a distinguished immunomodulating effect in THP-1 cells. The increase in IFN 1-alpha expression after ScaAB inoculation was similar to that against LAIV. We immunized mice intranasal using of A/H7N3 LAIV or/and ScaAB peptide. At day 5 after immunization, we detected serum IgM which reacted with non-vaccine influenza viruses. Associated vaccination of mice using LAIV and GBS peptide was the most effective against sub-lethal infection with A/H7N9 influenza virus and against lethal challenge with A/H1N1pdm virus at day 5 after immunization. Not only LAIV but also the ScaAB protected about 20% of the immunized animals against lethal challenge with A/H1N1pdm virus. The early protection was related to increasing type 1 interferons expression in the lungs.

Our results in mice have shown that successful protection against homologous and heterologous influenza infections can be achieved soon after vaccination with either LAIV or LAIV in combination with GBS recombinant peptide. Presumably, such protection may be mediated by non-specific IgM antibodies and an increase in the expression of early cytokines in the airway.

Effector B cells in cardiac allograft vasculopathy

PURPOSE OF REVIEW

B cells have recently emerged as important immune players in solid organ rejection, especially in cardiac allograft vasculopathy (CAV), a chronic form of rejection following heart transplantation. B cells can exert either regulatory or effector functions. This review will provide an update on effector B cells in CAV.

RECENT FINDINGS

Independent studies reported the abundance of B cells in graft infiltrates during CAV, especially around coronary arteries. Infiltrates comprise CD20+ CD27+ memory B cells together with differentiated CD20-CD138+ plasma cells, which are almost always associated with T cells and macrophages. The structure of some of these infiltrates evokes that of germinal centers, suggesting the generation of tertiary lymphoid organs in the graft. Remarkably, B-cell infiltrates are most often detected in the absence of circulating donor human leukocyte antigen-specific antibodies, strongly suggesting that the two components are unrelated. Characterization of B-cell clones isolated from explanted human cardiac graft infiltrates revealed the prevalence of polyreactive innate, B1-like B cells. Accumulating evidence suggests that these cells act primarily as antigen-presenting cells in situ. Additional effector functions, such as local antibody secretion and pro-inflammatory cytokine production, promoting T-cell polarization, macrophage activation and fibrosis are also considered.

SUMMARY

Converging observations made through animal and human studies add substantial support for an effector B-cell role in the pathophysiology of CAV. On the basis of these collective findings, a therapeutic strategy targeting B cells could reasonably be envisaged to prevent or treat this complication.

Anti-PD1 'SHR-1210' aberrantly targets pro-angiogenic receptors and this polyspecificity can be ablated by paratope refinement

Monoclonal anti-programmed cell death 1 (PD1) antibodies are successful cancer therapeutics, but it is not well understood why individual antibodies should have idiosyncratic side-effects. As the humanized antibody SHR-1210 causes capillary hemangioma in patients, a unique toxicity amongst anti-PD1 antibodies, we performed human receptor proteome screening to identify nonspecific interactions that might drive angiogenesis. This screen identified that SHR-1210 mediated aberrant, but highly selective, low affinity binding to human receptors such as vascular endothelial growth factor receptor 2 (VEGFR2), frizzled class receptor 5 and UL16 binding protein 2 (ULBP2). SHR-1210 was found to be a potent agonist of human VEGFR2, which may thereby drive hemangioma development via vascular endothelial cell activation. The v-domains of SHR-1210's progenitor murine monoclonal antibody 'Mab005' also exhibited off-target binding and agonism of VEGFR2, proving that the polyspecificity was mediated by the original mouse complementarity-determining regions (CDRs), and had survived the humanization process. Molecular remodelling of SHR-1210 by combinatorial CDR mutagenesis led to deimmunization, normalization of binding affinity to human and cynomolgus PD1, and increased potency in PD1/PD-L1 blockade. Importantly, CDR optimization also ablated all off-target binding, rendering the resulting antibodies fully PD1-specific. As the majority of changes to the paratope were found in the light chain CDRs, the germlining of this domain drove the ablation of off-target binding. The combination of receptor proteome screening and optimization of the antibody binding interface therefore succeeded in generating novel, higher-potency, specificity-enhanced therapeutic IgGs from a single, clinically sub-optimal progenitor. This study showed that highly-specific off-target binding events might be an under-appreciated phenomenon in therapeutic antibody development, but that these unwanted properties can be fully ameliorated by paratope refinement.

New insights on innate B-cell immunity in transplantation

Innate B cells and natural antibodies (Nabs) have been extensively studied in normal physiological conditions as well as in several diseases. However, their significance in the context of ABO-compatible solid organ transplantation is only emerging. This review summarizes recent studies exploring these often neglected innate immune elements in situations related to sensitization and clinical graft rejection. A focus is placed on class-switched IgG Nabs that develop amidst inflammation, rather than IgM Nabs abundant at the steady state, as new evidence point to their implication in serum reactivity to HLA and kidney graft failure. The involvement of innate B cells in the pathophysiology of CAV is also presented. Lastly, we discuss key questions that need answering to understand whether and how innate B-cell immunity contributes to the outcome of solid organ transplantation.

Autoantibodies reactive to adrenocorticotropic hormone can alter cortisol secretion in both aggressive and nonaggressive humans

Violent aggression in humans may involve a modified response to stress, but the underlying mechanisms are not well understood. Here we show that naturally present autoantibodies reactive to adrenocorticotropic hormone (ACTH) exhibit distinct epitope-binding profiles to ACTH peptide in subjects with a history of violent aggression compared with controls. Namely, while nonaggressive male controls displayed a preferential IgG binding to the ACTH central part (amino acids 11-24), subjects who had committed violent acts of aggression had IgG with increased affinity to ACTH, preferentially binding to its N terminus (amino acids 1-13). Purified IgGs from approximately half of the examined sera were able to block ACTH-induced cortisol secretion of human adrenal cells in vitro, irrespective of the source of sample (from a control subject or a violent aggressor). Nevertheless, in the resident-intruder test in mice, i.p. injection of residents with ACTH and IgG from aggressive subjects, but not from control subjects, shortened latency for the first attack against intruders. Immunohistochemical screening of violent aggressors' sera on rat brain and pituitary sections did not show IgG binding to ACTH-producing cells, but 4 of 16 sera revealed selective binding to a nonidentified antigen in vasopressinergic neurons of the hypothalamic paraventricular and supraoptic nuclei. Thus, the data show that ACTH-reactive plasmatic IgGs exhibit differential epitope preference in control and violently aggressive subjects. These IgGs can modulate ACTH-induced cortisol secretion and, hence, are involved in the regulation of the stress response. However, the possible role of ACTH-reactive autoantibodies in aggressive behavior needs further investigation.

Linear pharmacokinetic parameters for monoclonal antibodies are similar within a species and across different pharmacological targets: A comparison between human, cynomolgus monkey and hFcRn Tg32 transgenic mouse using a population-modeling approach

The linear pharmacokinetics (PK) of therapeutic monoclonal antibodies (mAbs) can be considered a class property with values that are similar to endogenous IgG. Knowledge of these parameters across species could be used to avoid unnecessary in vivo PK studies and to enable early PK predictions and pharmacokinetic/pharmacodynamic (PK/PD) simulations. In this work, population-pharmacokinetic (popPK) modeling was used to determine a single set of ‘typical’ popPK parameters describing the linear PK of mAbs in human, cynomolgus monkey and transgenic mice expressing the human neonatal Fc receptor (hFcRn Tg32), using a rich dataset of 27 mAbs. Non-linear PK was excluded from the datasets and a 2-compartment model was applied to describe mAb disposition. Typical human popPK estimates compared well with data from comparator mAbs with linear PK in the clinic. Outliers with higher than typical clearance were found to have non-specific interactions in an affinity-capture self-interaction nanoparticle spectroscopy assay, offering a potential tool to screen out these mAbs at an early stage. Translational strategies were investigated for prediction of human linear PK of mAbs, including use of typical human popPK parameters and allometric exponents from cynomolgus monkey and Tg32 mouse. Each method gave good prediction of human PK with parameters predicted within 2-fold. These strategies offer alternative options to the use of cynomolgus monkeys for human PK predictions of linear mAbs, based on in silico methods (typical human popPK parameters) or using a rodent species (Tg32 mouse), and call into question the value of completing extensive in vivo preclinical PK to inform linear mAb PK.

Post-Transplant Natural Antibodies Associate with Kidney Allograft Injury and Reduced Long-Term Survival

Background The development of antibodies specific to HLA expressed on donor tissue (donor-specific antibodies [DSAs]) is a prominent risk factor for kidney graft loss. Non-HLA antibodies with pathogenic potential have also been described, including natural antibodies (Nabs). These IgG Nabs bind to immunogenic self-determinants, including oxidation-related antigens.Methods To examine the relationship of Nabs with graft outcomes, we assessed Nabs in blinded serum specimens collected from a retrospective cohort of 635 patients who received a transplant between 2005 and 2010 at Necker Hospital in Paris, France. Serum samples were obtained immediately before transplant and at the time of biopsy-proven rejection within the first year or 1 year after transplant. Nabs were detected by ELISA through reactivity to the generic oxidized epitope malondialdehyde.Results Univariate Cox regression analysis identified the development of post-transplant Nabs (defined as 50% increase in reactivity to malondialdehyde) as a significant risk factor for graft loss (hazard ratio, 2.68; 95% confidence interval, 1.49 to 4.82; P=0.001). Post-transplant Nabs also correlated with increased mean Banff scores for histologic signs of graft injury in post-transplant biopsy specimens. Multivariable Cox analyses confirmed Nabs development as a risk factor independent from anti-HLA DSAs (hazard ratio, 2.07; 95% confidence interval, 1.03 to 4.17; P=0.04). Moreover, patients with Nabs and DSAs had a further increased risk of kidney graft loss.Conclusions These findings reveal an association between Nabs, kidney graft injury, and eventual graft failure, suggesting the involvement of Nabs in immune mechanisms of rejection.

Hexons from adenovirus serotypes 5 and 48 differentially protect adenovirus vectors from neutralization by mouse and human serum

Adenovirus vectors are widely used in gene therapy clinical trials, and preclinical studies with these vectors are often conducted in mice. It is therefore critical to understand whether mouse studies adequately predict the behavior of adenovirus vectors in humans. The most commonly-used adenovirus vectors are derived from adenovirus serotype 5 (Ad5). The Ad5 hexon protein can bind coagulation factor X (FX), and binding of FX has a major impact on vector interactions with other blood proteins. In mouse serum, FX protects Ad5 vectors from neutralization by natural antibodies and complement. In the current study, we similarly find that human FX inhibits neutralization of Ad5 vectors by human serum, and this finding is consistent among individual human sera. We show that human IgM and human IgG can each induce complement-mediated neutralization when Ad5 vectors are not protected by FX. Although mouse and human serum had similar effects on Ad5 vectors, we found that this was not true for a chimeric Ad5 vector that incorporated hexon regions from adenovirus serotype 48. Interestingly, this hexon-chimeric vector was neutralized by human serum, but not by mouse serum. These findings indicate that studies in mouse serum accurately predict the behavior of Ad5 vectors in human serum, but mouse serum is not an accurate model system for all adenovirus vectors.

A natural human monoclonal antibody protects from axonal injury in different CNS degenerative disease models

Axon regeneration after CNS injury is incomplete. This is partially due to the presence of multiple growth inhibitory molecules within myelin that prevent axonal extension. These inhibitors include myelin-associated glycoprotein, Nogo and oligodendrocyte myelin glycoprotein. A natural human recombinant antibody, rHIgM12, was identified by its ability to promote neurite outgrowth in vitro. rHIgM12 overrides the neurite outgrowth inhibition of myelin by binding with high affinity to neuronal PSA-NCAM and gangliosides. This neurite outgrowth is accompanied by increased α-tubulin tyrosination and decreased acetylation which occurs after treatment with rHIgM12. rHIgM12 is efficacious in murine models of human multiple sclerosis and amyotrophic lateral sclerosis, improving axon survival and neurologic function. rHIgM12 has great promise as a therapeutic molecule in a number of CNS disorders characterized by neuronal loss and axonal transection including multiple sclerosis. This review will focus on rHIgM12 discovery, effects in preclinical models and potential applications as a therapeutic reagent for CNS disease.