[Preparation technology comparison and performance evaluation of different protein A affinity chromatographic materials]

Protein A affinity chromatographic materials are widely used in clinical medicine and biomedicine because of their specific interactions with immunoglobulin G (IgG). Both the characteristics of the matrix, such as its structure and morphology, and the surface modification method contribute to the affinity properties of the packing materials. The specific, orderly, and oriented immobilization of protein A can reduce its steric hindrance with the matrix and preserve its bioactive sites. In this study, four types of affinity chromatographic materials were obtained using agarose and polyglycidyl methacrylate (PGMA) spheres as substrates, and multifunctional epoxy and maleimide groups were used to fix protein A. The effects of the ethylenediamine concentration, reaction pH, buffer concentration, and other conditions on the coupling efficiency of protein A and adsorption performance of IgG were evaluated. Multifunctional epoxy materials were prepared by converting part of the epoxy groups of the agarose and PGMA matrices into amino groups using 0.2 and 1.6 mol/L ethylenediamine, respectively. Protein A was coupled to the multifunctional epoxy materials using 5 mmol/L borate buffer (pH 8) as the reaction solution. When protein A was immobilized on the substrates by maleimide groups, the agarose and PGMA substrates were activated with 25% (v/v) ethylenediamine for 16 h to convert all epoxy groups into amino groups. The maleimide materials were then converted into amino-modified materials by adding 3 mg/mL 3-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS) dissolved in dimethyl sulfoxide (DMSO) and then suspended in 5 mmol/L borate buffer (pH 8). The maleimide groups reacted specifically with the C-terminal of the sulfhydryl group of recombinant protein A to achieve highly selective fixation on both the agarose and PGMA substrates. The adsorption performance of the affinity materials for IgG was improved by optimizing the bonding conditions of protein A, such as the matrix type, matrix particle size, and protein A content, and the adsorption properties of each affinity material for IgG were determined. The column pressure of the protein A affinity materials prepared using agarose or PGMA as the matrix via the maleimide method was subsequently evaluated at different flow rates. The affinity materials prepared with PGMA as the matrix exhibited superior mechanical strength compared with the materials prepared with agarose. Moreover, an excellent linear relationship between the flow rate and column pressure of 80 mL/min was observed for this affinity material. Subsequently, the effect of the particle size of the PGMA matrix on the binding capacity of IgG was investigated. Under the same protein A content, the dynamic binding capacity of the affinity materials on the PGMA matrix was higher when the particle size was 44-88 μm than when other particle sizes were used. The properties of the affinity materials prepared using the multifunctional epoxy and maleimide-modified materials were compared by synthesizing affinity materials with different protein A coupling amounts of 1, 2, 4, 6, 8, and 10 mg/mL. The dynamic and static binding capacities of each material for bovine IgG were then determined. The prepared affinity material was packed into a chromatographic column to purify IgG from bovine colostrum. Although all materials showed specific adsorption selectivity for IgG, the affinity material prepared by immobilizing protein A on the PGMA matrix with maleimide showed significantly better performance and achieved a higher dynamic binding capacity at a lower protein grafting amount. When the protein grafting amount was 15.71 mg/mL, the dynamic binding capacity of bovine IgG was 32.23 mg/mL, and the dynamic binding capacity of human IgG reached 54.41 mg/mL. After 160 cycles of alkali treatment, the dynamic binding capacity of the material reached 94.6% of the initial value, indicating its good stability. The developed method is appropriate for the production of protein A affinity chromatographic materials and shows great potential in the fields of protein immobilization and immunoadsorption material synthesis.

A highly specific antibody against the core fucose of the N-glycan in IgG identifies the pulmonary diseases and its regulation by CCL2

Glycan structure is often modulated in disease or predisease states, suggesting that such changes might serve as biomarkers. Here, we generated a monoclonal antibody (mAb) against the core fucose of the N-glycan in human IgG. Notably, this mAb can be used in Western blotting and ELISA. ELISA using this mAb revealed a low level of the core fucose of the N-glycan in IgG, suggesting that the level of acore fucosylated (noncore fucosylated) IgG was increased in the sera of the patients with lung cancer, chronic obstructive pulmonary disease, and interstitial pneumonia compared to healthy subjects. In a coculture analysis using human lung adenocarcinoma A549 cells and antibody-secreting B cells, the downregulation of the FUT8 (α1,6 fucosyltransferase) gene and a low level of core fucose of the N-glycan in IgG in antibody-secreting B cells were observed after coculture. A dramatic alteration in gene expression profiles for cytokines, chemokines, and their receptors were also observed after coculturing, and we found that the identified C-C motif chemokine 2 was partially involved in the downregulation of the FUT8 gene and the low level of core fucose of the N-glycan in IgG in antibody-secreting B cells. We also developed a latex turbidimetric immunoassay using this mAb. These results suggest that communication with C-C motif chemokine 2 between lung cells and antibody-secreting B cells downregulate the level of core fucose of the N-glycan in IgG, i.e., the increased level of acore fucosylated (noncore fucosylated) IgG, which would be a novel biomarker for the diagnosis of patients with pulmonary diseases.

FcRn inhibitors: a novel option for the treatment of myasthenia gravis

Myasthenia gravis is an acquired, humoral immunity-mediated autoimmune disease characterized by the production of autoantibodies that impair synaptic transmission at the neuromuscular junction. The intervention-mediated clearance of immunoglobulin G (IgG) was shown to be effective in controlling the progression of the disease. The neonatal Fc receptor (FcRn) plays a key role in prolonging the serum half-life of IgG. Antagonizing FcRn to prevent its binding to IgG can accelerate the catabolism of the latter, resulting in decreased levels of IgG, including pathogenic autoantibodies, thereby achieving a therapeutic effect. In this review, we detail the substantial research progress, both basic and clinical, relating to the use of FcRn inhibitors in the treatment of myasthenia gravis.

IgG glycomic profiling identifies potential biomarkers for diagnosis of echinococcosis

Echinococcosis caused by larval stage of the genus Echinococcus, is a serious and potentially fatal parasitic zoonosis distributed globally. The two types of the disease in human are cystic echinococcosis (CE) and alveolar echinococcosis (AE). As the biological and encysting characteristics of the parasite, early diagnosis remains to address. In the present study, we demonstrate the value of Immunoglobulin G (IgG) glycome as a potential diagnostic biomarker for echinococcosis. Serum IgG glycome profiles were analyzed by ultra-performance liquid chromatography in a cohort comprised of 127 echinococcosis patients, of them 98 were diagnosed as CE and 29 as AE. IgG N-glycome analysis in pretreatment serum of echinococcosis patients presents 25 glycans and 64 derived traits. Compared with IgG glycans of healthy control group, neutral glycans, fucosylation and agalactosylated N-glycans increased while sialylation and galactosylation decreased in echinococcosis patients. Combined with a machine-learning-based approach, we built three biomarker combinations to distinguish CE, AE and healthy controls. Meanwhile, galactosylation, sialylation and A2BG2S1 in IgG glycan profiles were evidently associated with different types of CE (from CE1 to CE5). Our findings suggest that the alterations in IgG N-glycome may be of value in CE and AE diagnosis and follow-up CE disease progress. The role of IgG N-glycans as diagnostic biomarker remains to be verified in future study.

Association between the Treatment of Rosacea and Eradication of Helicobacter Pylori Infection

Background

Rosacea is a multifactorial skin inflammatory disorder with an unknown cure. Genetics and environmental factors such as microorganisms are involved in the rosacea etiology, for example, Helicobacter pylori have been suggested in rosacea progression. The present study investigated the relationship between H. pylori eradication and rosacea patient's improvement.

Materials and Methods

H. pylori infection was investigated in 60 rosacea patients and 65 sex- and age-matched healthy control through enzyme-linked immunosorbent assay (ELISA) and HpSag tests. After infection confirmation, randomly half of the rosacea patients were treated for H. pylori eradication (test), and others received standard treatment (control). HpSag and ELISA tests were repeated after infection eradication and disease flow was surveyed for 60 days. The groups were compared using the ANOVA (Analysis Of Variance) test at the significant level of P < 0.05.

Results

At the baseline, the mean of immunoglobulin G (IgG) (59.27 ± 41.4 RU/mL) and immunoglobulin M (IgM) (11.55 ± 6.1 RU/mL) in rosacea patients was higher than the level of IgG (41.38 ± 54.33 RU/mL) and IgM (8.11 ± 8.91 RU/mL) in healthy control (P < 0.04) and (P < 0.01), respectively. Also, the values for H. pylori infection were positive in all patients and 10 healthy controls. The mean titer of IgM and IgG in the test and control patients groups were different at baseline and after treatment. Furthermore, in the test patients group, the mean of IgG was reduced in active rosacea after treatment, and 63.9% of active patients showed rosacea remission after H. pylori eradication.

Conclusion

Data suggest the exacerbating role of H. pylori in rosacea, and its eradication along with other therapeutic methods causes rosacea improvement.

Antibody-guided proteases enable selective and catalytic degradation of challenging therapeutic targets

The exquisite specificity, natural biological functions, and favorable development properties of antibodies make them highly effective agents as drugs. Monoclonal antibodies are particularly strong as inhibitors of systemically accessible targets where trough-level concentrations can sustain full target occupancy. Yet beyond this pharmacologic wheelhouse, antibodies perform suboptimally for targets of high abundance and those not easily accessible from circulation. Fundamentally, this restraint on broader application is due largely to the stoichiometric nature of their activity - one drug molecule is generally able to inhibit a maximum of two target molecules at a time. Enzymes in contrast are able to catalytically turnover multiple substrates, making them a natural sub-stoichiometric solution for targets of high abundance or in poorly accessible sites of action. However, enzymes have their own limitations as drugs, including, in particular the polypharmacology and broad specificity often seen with native enzymes. In this study, we introduce antibody-guided proteolytic enzymes to enable selective sub-stoichiometric turnover of therapeutic targets. We demonstrate that antibody-mediated substrate targeting can enhance enzyme activity and specificity, with proof of concept for two challenging target proteins, amyloid-β (Aβ) and immunoglobulin G (IgG). This work advances a new biotherapeutic platform that combines the favorable properties of antibodies and proteolytic enzymes to more effectively suppress high-bar therapeutic targets.

Modifying antibody-FcRn interactions to increase the transport of antibodies through the blood-brain barrier

The blood-brain barrier (BBB) largely excludes antibodies from entering the central nervous system, thus limiting the potential of therapeutic antibodies to treat conditions such as neurodegenerative diseases and neuro-psychiatric disorders. Here, we demonstrate that the transport of human antibodies across the BBB in mice can be enhanced by modulating their interactions with the neonatal Fc receptor (FcRn). When M252Y/S254T/T246E substitutions are introduced on the antibody Fc domain, immunohistochemical assays reveal widespread distribution of the engineered antibodies throughout the mouse brain. These engineered antibodies remain specific for their antigens and retain pharmacological activity. We propose that novel brain-targeted therapeutic antibodies can be engineered to differentially engage FcRn for receptor-mediated transcytosis across the BBB in order to improve neurological disease therapeutics in the future.

Evaluation of S- and M-Proteins Expressed in Escherichia coli and HEK Cells for Serological Detection of Antibodies in Response to SARS-CoV-2 Infections and mRNA-Based Vaccinations

This study investigated the IgG and IgA antibody response against recombinant S1 and receptor binding domains (RBD) of the spike (S-) protein and the membrane (M-) protein using a set of 115 serum samples collected from patients infected with SARS-CoV-2 in Germany before April 2021 using protein and peptide ELISA. As S1- and RBD-proteins expressed in Escherichia coli provided poor sensitivities in ELISA, they were replaced by proteins expressed in HEK cells. The RBD-ELISA provided a sensitivity of 90.6% (N = 85) for samples collected from patients with confirmed SARS-CoV-2 infections more than 14 days after symptom onset or a positive PCR test. In population-based controls, the specificity was 97.9% (N = 94). In contrast, the sensitivities were only 41.2% and 72.6% for M- and N-proteins, respectively, while the specificities were 88.5% and 100%, respectively. Considering also 20 samples collected during the first two weeks of symptom onset or PCR confirmation, the sensitivity of RBD- and N-protein ELISA decreased to 82.6% and 72.6%, respectively. The combination of two data sets, i.e., N- and RBD-, N- and M-, or RBD- and M-proteins increased the sensitivity to 85.8%, 77.9%, and 87.8%, respectively. Peptide mapping mostly confirmed epitopes previously reported for S1- and M-proteins, but they were only recognized by a few samples already tested positive in the corresponding protein ELISA indicating that peptide-based assays will not improve the diagnostic sensitivity.

Waning of Humoral Immunity and the Influencing Factors after BNT162b2 Vaccination: A Cohort Study with a Latent Growth Curve Model in Fukushima

Measuring long-term antibody titer kinetics and subsequent coronavirus disease 2019 (COVID-19) vaccinations are crucial for identifying vulnerable populations. Our aim was to determine the association between long-term antibody kinetics, including peak titers and factors, up to seven months post-second vaccination. A three-time antibody survey was conducted in 2021 among healthcare workers in Japan to investigate the changes in humoral immunity using chemiluminescence immunoassay. The study involved 205 participants who had received the second vaccine dose, completed the three-time survey, and were not infected with SARS-CoV-2. A latent growth curve model was used to identify factors affecting the peak titer and decreasing the antibody slope. Of the eligible participants, the mean titers of immunoglobulin G (IgG) against the spike (S) protein and the neutralizing activity 7 months after the second vaccination decreased to 154.3 (8.8% of the peak titer) and 62.1 AU/mL (9.5% of the peak titer), respectively. The IgG growth model showed that age significantly affected peak titers (p < 0.001); however, a significant difference was not found for the decreasing slope. Ultimately, aging adults had significantly low peak antibody titers; however, age was unrelated to the slope of log-transformed IgG against the S protein.

Nonenzymatic glycosylation of isolated human immunoglobulin-G by D-ribose

Glycation is vital in terms of its damaging effect on macromolecules resulting in the formation of end products, which are highly reactive and cross-linked irreversible structures, known as advanced glycation end products (AGEs). The continuous accumulation of AGEs is associated with severe diabetes and its associated ailments. Saccharides with their reducing ends can glycate amino acid side chains of proteins, among them glucose is well-known for its potent glycating capability. However, other reducing sugars can be more reactive glycating agents than glucose. The D-ribose is a pentose sugar-containing an active aldehyde group in its open form and is responsible for affecting the biological processes of the cellular system. D-ribose, a key component of many biological molecules, is more reactive than most reducing sugars. Protein glycation by reducing monosaccharides such as D-ribose promotes the accelerated formation of AGEs that could lead to cellular impairments and dysfunctions. Also, under a physiological cellular state, the bioavailability rate of D-ribose is much higher than that of glucose in diabetes, which makes this species much more active in protein glycation as compared with D-glucose. Due to the abnormal level of D-ribose in the biological system, the glycation of proteins with D-ribose needs to be analyzed and addressed carefully. In the present study, human immunoglobulin G (IgG) was isolated and purified via affinity column chromatography. D-ribose at 10 and 100 mM concentrations was used as glycating agent, for 1-12 days of incubation at 37°C. The postglycation changes in IgG molecule were characterized by UV-visible and fluorescence spectroscopy, nitroblue tetrazolium assay, and various other physicochemical analyses for the confirmation of D-ribose mediated IgG glycation.

Patients With Inflammatory Bowel Disease Show IgG Immune Responses Towards Specific Intestinal Bacterial Genera

Introduction

Inflammatory bowel disease (IBD) is characterized by a disturbed gut microbiota composition. Patients with IBD have both elevated mucosal and serum levels of IgG-antibodies directed against bacterial antigens, including flagellins. In this study, we aimed to determine to which intestinal bacteria the humoral immune response is directed to in patients with IBD.

Methods

Fecal and serum samples were collected from patients with IBD (n=55) and age- and sex-matched healthy controls (n=55). Fecal samples were incubated with autologous serum and IgG-coated fractions were isolated by magnetic-activated cell sorting (MACS) and its efficiency was assessed by flow cytometry. The bacterial composition of both untreated and IgG-coated fecal samples was determined by 16S rRNA-gene Illumina sequencing.

Results

IgG-coated fecal samples were characterized by significantly lower microbial diversity compared to the fecal microbiome. Both in patients with IBD and controls, serum IgG responses were primarily directed to Streptococcus, Lactobacillus, Lactococcus, Enterococcus, Veillonella and Enterobacteriaceae, as well as against specific Lachnospiraceae bacteria, including Coprococcus and Dorea (all P<0.001), and to Ruminococcus gnavus-like bacteria (P<0.05). In contrast, serological IgG responses against typical commensal, anaerobic and colonic microbial species were rather low, e.g. to the Lachnospiraceae members Roseburia and Blautia, to Faecalibacterium, as well as to Bacteroides. Patients with IBD showed more IgG-coating of Streptococcus, Lactobacillus, and Lactococcus bacteria compared to healthy controls (all P<0.05). No differences in IgG-coated bacterial fractions were observed between Crohn's disease and ulcerative colitis, between active or non-active disease, nor between different disease locations.

Conclusion

The IgG immune response is specifically targeted at distinct intestinal bacterial genera that are typically associated with the small intestinal microbiota, whereas responses against more colonic-type commensals are lower, which was particularly the case for patients with IBD. These findings may be indicative of a strong immunological exposure to potentially pathogenic intestinal bacteria in concordance with relative immune tolerance against commensal bacteria.

[What Is an Antibody Test? Characteristics of Antibodies against SARS-CoV-2 and Their Tests]

Antibodies play a major role in immune responses against viruses, which inhibit infection by binding to target viral antigen. Antibodies are induced by viral entry to the body and vaccination that artificially induces immune responses; therefore, antibody tests are used in research for infection history and evaluation of vaccine efficacy. Currently, antibody tests against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) by immunochromatography, enzyme-linked immunosorbent assay (ELISA), and electrochemiluminescence immunoassay (ECLIA), or other kits used for automated analyzer are available. However, the test results should be carefully interpreted because requirements for the antibody test to obtain reliable results have not been established. Also, antibodies in human samples are heterogeneous, and their expression level changes over time. This review briefly explains the basic knowledge about antibodies against SARS-CoV-2 and outlines the classification and characteristics of the antibody tests with points to consider in their use. A summary of the collaborative study that evaluated the analytical performance of antibody test kits conducted by the National Institute of Health Sciences is also introduced. Then, the issues in ensuring the reliability of antibody tests results are discussed by considering the usefulness and availability of the World Health Organization international standard for anti-SARS-CoV-2 immunoglobulin.

Changes of IgG N-Glycosylation in Thyroid Autoimmunity: The Modulatory Effect of Methimazole in Graves' Disease and the Association With the Severity of Inflammation in Hashimoto's Thyroiditis

The N-glycome of immunoglobulin G (IgG), the most abundant glycoprotein in human blood serum, reflects pathological conditions of autoimmunity and is sensitive to medicines applied in disease therapy. Due to the high sensitivity of N-glycosylation, the IgG N-glycan profile may serve as an indicator of an ongoing inflammatory process. The IgG structure and its effector functions are strongly dependent on the composition of N-glycans attached to the Fc fragment, and the binding of antigens is regulated by Fab sugar moieties. Because of the crucial role of N-glycans in IgG function, remodeling of its N-oligosaccharides can induce pathological changes that ultimately contribute to the development of autoimmunity; restoration of their physiological structure is critical to the reduction of disease symptoms. Our recently published data have shown that the pathology of autoimmune thyroid diseases (AITDs), including Hashimoto’s thyroiditis (HT) and Graves’ disease (GD), is accompanied by alterations of the composition of IgG N-glycans. The present study is a more in-depth investigation of IgG glycosylation in both AITDs, designed to determine the relationship between the severity of thyroid inflammation and IgG N-glycan structures in HT, and to assess the impact of immunosuppressive therapy on the N-glycan profile in GD patients. The study material consisted of human serum samples collected from donors with elevated anti-thyroglobulin (Tg) and/or anti-thyroperoxidase (TPO) IgGs without symptoms of hypothyroidism (n=68), HT patients characterized by high autoantibody titers and advanced destruction of the thyroid gland (n=113), GD patients with up-regulated IgG against thyroid-stimulating hormone receptor (TSHR) before (n=62) and after (n=47) stabilization of TSH level as a result of methimazole therapy (study groups), and healthy donors (control group, n=90). IgG was isolated from blood serum using protein G affinity chromatography. N-glycans were released from IgG by PNGase F digestion and analyzed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) after 2-aminobenzamide (2-AB) labeling. UPLC-MS chromatograms were integrated into 25 peaks (GP) in the Waters UNIFI Scientific Information System, and N-glycans were assigned based on the glucose unit values and mass-to-charge ratios (m/z) of the detected ions. The Kruskal-Wallis non-parametric test was used to determine the statistical significance of the results (p<0.05). The obtained results suggest that modifications of IgG sialylation, galactosylation and core-fucosylation are associated with the severity of HT symptoms. Methimazole therapy implemented in GD patients affected the IgG N-glycan profile; as a result, the content of the sialylated and galactosylated oligosaccharides with core fucose differed after treatment. Our results suggest that N-glycosylation of IgG undergoes dynamic changes during the intensification of thyroiditis in HT, and that in GD autoimmunity it is affected significantly by immunosuppressive therapy.

Serum immunoglobulin G as a discriminator of infection in follicular lymphoma patients undergoing chemotherapy with bendamustine in combination with rituximab

OBJECTIVES

Chemotherapy, including bendamustine, usually causes lymphocytopaenia and hypogammaglobulinaemia as side effects in patients with haematological malignancies. Therefore, the possibility has been considered that these immunological adverse events induced by bendamustine may lead to infectious diseases. However, lymphocytopaenia and/or hypogammaglobulinaemia have not yet been shown to have a statistically significant association with infection in cancer patients who receive bendamustine.

METHODS

We retrospectively studied 27 patients with relapsed or refractory indolent follicular lymphoma who were treated with bendamustine and rituximab (BR). In order to elucidate relationships between immune-related laboratory parameters (i.e. peripheral blood leukocyte, neutrophil, lymphocyte and immunoglobulin G [IgG]) and infectious events, receiver operating characteristic (ROC) curve and multivariate logistic regression analyses were performed.

RESULTS

Infectious diseases occurred in 11 patients (11/27, 41%), including 3 (3/27, 11%) with severe diseases. The area under the ROC curve (AUC) showed that the lowest IgG level during and after BR discriminated infectious events (cut-off value, 603 mg/dL) with 81.8% sensitivity and 68.8% specificity (AUC, 0.76; 95% CI, 0.52-0.90). Furthermore, a multivariate regression analysis revealed that the minimal serum IgG value during and after BR therapy was the only variable that was significantly associated with infection (odds ratio, 8.29; 95% CI, 1.19-57.62; p value, 0.03).

CONCLUSION

Serum IgG ≤603 mg/dL during and after BR therapy was independently associated with an increased risk of infection. The monitoring of serum IgG during chemotherapy may help to predict the development of infection in blood cancer patients undergoing chemotherapy with bendamustine in combination with rituximab.

The Combined Effect of IgG and Fe Supply and Feeding Management on Growth Rates of Calves on Eight Commercial Dairy Farms in Germany

During the first days of a calf’s life, the foundations are laid for successful growth and thus also for the later performance of the cows. The aim of the present study was to analyze the impact on the weight gain of newborn calves due to important management factors related to colostrum supply, iron supply, feeding regime and microbial load at first feeding. In spring 2017, information of 123 Holstein calves were analyzed with regard to the colostrum supply and management factors on eight commercial dairy farms located in Germany. Additionally, blood samples of newborn calves were analyzed for total immunoglobulin G (IgG) and serum iron content. Furthermore, Brix analysis and analysis of contamination by E. coli were performed on first colostrum samples from teats or buckets. Average daily weight gain of calves at days 14 and 50 was calculated. The colostrum IgG was estimated by Brix refractometer. The volume of initial colostrum supply and the time between birth and colostrum intake significantly (p < 0.05) influenced the serum IgG concentration. The serum IgG concentration, the serum iron concentration and the feeding regimen (restrictive or not restrictive feeding) had a significant effect (p < 0.05) on daily weight gains. In conclusion, this study shows that, in addition to a sufficient supply of immunoglobulins, other aspects, such as an adequate colostrum, iron and milk supply, play an essential role in calf growth rates.

Serum Protein Electrophoresis May Be Used as a Screening Tool for Antibody Deficiency in Children and Adolescents

Background

Patients with antibody deficiency may experience exceptionally long diagnostic delays, increasing the risk of life-threatening infections, end-organ damage, mortality, and health costs.

Objective

This study aimed to analyze serum protein electrophoresis and verify the correlation between calculated globulin (CG, total protein minus albumin levels) or electrophoretically determined serum gamma globulin fraction (Gamma) with IgG levels in children and adolescents under 18 years old (yo).

Methods

We analyzed serum protein electrophoresis (GC or Gamma) and IgG levels from 1215 children and adolescents under 18 yo, classified into 5 age groups. We verified the correlation between CG or Gamma with serum IgG levels.

Results

Serum IgG levels varied according to age groups (from 4.3 ± 2.3 g/l in children under 6 months old to 11.4 ± 3.2 g/l in adolescents in the 10-<18 yo group). CG sensitivity and specificity to detect IgG below the reference range for all patients were 93.1% and 81.8%, respectively, and varied according to age group. Gamma sensitivity and specificity for all patients were 100% and 87.8%, respectively, and varied according to age group as well. We found serum IgG levels below the age reference level in 29 patients (2.4% of the cases) using CG or Gamma levels.

Conclusion

Both CG and Gamma levels may be of utility as a screening tool for earlier diagnosis of antibody deficiency in children and adolescents under 18 yo.

Effects of Litter Size and Parity Number on Mammary Secretions Including, Insulin-Like Growth Factor-1, Immunoglobulin G and Vitamin A of Black Bengal, Saanen and Their Crossbred Goats in Thailand

The present study aims to investigate the composition including concentrations of IGF-1, IgG and Vit A in colostrum and their effects by litter size and goat parity in 3 groups of goats; Black Bengal (BB), Saanen (SA) and their crossbred (BBSA). Thirty-eight goats were used (23 BB, 7 BBSA and 8 SA). The composition (fat, protein, lactose and total solid; TS) in colostrum (Day 0; D0) and milk (Day 4; D4 and Day 7; D7) were measured. The IGF-1, IgG concentrations were analysed in some samples collected at D0, D4 and D7 while Vit A was analysed only in colostrum. The results showed that colostrum components were similar among experimental groups. However, the colostral IGF-1 concentration of BBSA (983.0 ± 163.6 ng/mL) was higher than that of BB (340.7 ± 85.5 ng/mL, p < 0.01) and SA (417.1 ± 93.9 ng/mL, p < 0.01). The colostral IgG concentration of BB (8.2 ± 0.9 mg/mL) was lower than that of BBSA (12.9 ± 1.7 mg/mL, p < 0.05) and SA (12.9 ± 1.0 mg/mL, p < 0.01). Colostral Vit A concentration in BBSA (787.2 ± 152.6 µg/100 gm) was higher than that in BB (388.9 ± 84.3 µg/100 gm, p < 0.05) but was not different from SA (522.8 ± 96.9 µg/100 gm). Colostrum from all groups contained higher protein and TS but was lower in lactose concentration than milk. The IGF-1 and IgG concentrations in colostrum were much higher than in milk both D4 and D7 (p < 0.001). Additionally, litter size had no effects on colostrum contents but colostrum from goats with a higher parity number had higher IgG concentration. It is concluded that colostrum from BBSA may be superior when fed to BB newborn goats in terms of higher IGF-1, IgG and Vit A contents. Moreover, colostrum from goats with a high parity number contained more IgG content.

Anti-glomerular basement membrane disease mediated by IgG and IgA: a case report

Background

Anti-glomerular basement membrane (anti-GBM) disease is a rare autoimmune condition responsible for rapidly progressive glomerulonephritis. This disease is usually mediated by IgG autoantibodies against the noncollagenous domain of the α3(IV) collagen chain. In rare cases, IgA or IgM anti-GBM antibodies are involved. This raises the question of whether there are different types of antibody-mediated anti-GBM disease at the same time.

Case report

A 37-year-old woman with anti-GBM disease mediated by IgG and IgA. The patient developed rapidly progressive glomerulonephritis with nephrotic syndrome. Indirect immunofluorescence analysis indicated the presence of IgG and IgA antibodies reactive with a basement membrane component, identified by enzyme-linked immunoadsorbent assay and Western blotting as the α3(IV) collagen chain. After plasmapheresis and immunotherapy (steroids and cyclophosphamide), much improved the massive proteinuria and renal function. Follow up to date, she had normal renal function without proteinuria.

Conclusions

This is the first case report of anti-GBM disease mediated by IgG and IgA. If the clinical presentation and histopathological findings are suggestive of atypical anti-GBM disease, alternative laboratory tests such as Western blotting analysis can be used to confirm the diagnosis.

Effect of Processing on Fish Protein Antigenicity and Allergenicity

Fish allergy is a life-long food allergy whose prevalence is affected by many demographic factors. Currently, there is no cure for fish allergy, which can only be managed by strict avoidance of fish in the diet. According to the WHO/IUIS Allergen Nomenclature Sub-Committee, 12 fish proteins are recognized as allergens. Different processing (thermal and non-thermal) techniques are applied to fish and fishery products to reduce microorganisms, extend shelf life, and alter organoleptic/nutritional properties. In this concise review, the development of a consistent terminology for studying food protein immunogenicity, antigenicity, and allergenicity is proposed. It also summarizes that food processing may lead to a decrease, no change, or even increase in fish antigenicity and allergenicity due to the change of protein solubility, protein denaturation, and the modification of linear or conformational epitopes. Recent studies investigated the effect of processing on fish antigenicity/allergenicity and were mainly conducted on commonly consumed fish species and major fish allergens using in vitro methods. Future research areas such as novel fish species/allergens and ex vivo/in vivo evaluation methods would convey a comprehensive view of the relationship between processing and fish allergy.

Identification and biochemical characterization of Asp t 36, a new fungal allergen from Aspergillus terreus

Aspergillus terreus is an allergenic fungus, in addition to causing infections in both humans and plants. However, the allergens in this fungus are still unknown, limiting the development of diagnostic and therapeutic strategies. We used a proteomic approach to search for allergens, identifying 16 allergens based on two-dimensional immunoblotting with A. terreus susceptible patient sera. We further characterized triose-phosphate isomerase (Asp t 36), one of the dominant IgE (IgE)-reactive proteins. The gene was cloned and expressed in Escherichia coli. Phylogenetic analysis showed Asp t 36 to be highly conserved with close similarity to the triose-phosphate isomerase protein sequence from Dermatophagoides farinae, an allergenic dust mite. We identified four immunodominant epitopes using synthetic peptides, and mapped them on a homology-based model of the tertiary structure of Asp t 36. Among these, two were found to create a continuous surface patch on the 3D structure, rendering it an IgE-binding hotspot. Biophysical analysis indicated that Asp t 36 shows similar secondary structure content and temperature sensitivity with other reported triose-phosphate isomerase allergens. In vivo studies using a murine model displayed that the recombinant Asp t 36 was able to stimulate airway inflammation, as demonstrated by an influx of eosinophils, goblet cell hyperplasia, elevated serum Igs, and induction of Th2 cytokines. Collectively, our results reveal the immunogenic property of Asp t 36, a major allergen from A. terreus, and define a new fungal allergen more broadly. This allergen could serve as a potent candidate for investigating component resolved diagnosis and immunotherapy.

Hydrogen/deuterium exchange memory NMR reveals structural epitopes involved in IgE cross-reactivity of allergenic lipid transfer proteins

Identification of antibody-binding epitopes is crucial to understand immunological mechanisms. It is of particular interest for allergenic proteins with high cross-reactivity as observed in the lipid transfer protein (LTP) syndrome, which is characterized by severe allergic reactions. Art v 3, a pollen LTP from mugwort, is frequently involved in this cross-reactivity, but no antibody-binding epitopes have been determined so far. To reveal human IgE-binding regions of Art v 3, we produced three murine high-affinity mAbs, which showed 70-90% coverage of the allergenic epitopes from mugwort pollen-allergic patients. As reliable methods to determine structural epitopes with tightly interacting intact antibodies under native conditions are lacking, we developed a straightforward NMR approach termed hydrogen/deuterium exchange memory (HDXMEM). It relies on the slow exchange between the invisible antigen-mAb complex and the free ¹⁵N-labeled antigen whose ¹H-¹⁵N correlations are detected. Due to a memory effect, changes of NH protection during antibody binding are measured. Differences in H/D exchange rates and analyses of mAb reactivity to homologous LTPs revealed three structural epitopes: two partially cross-reactive regions around α-helices 2 and 4 as well as a novel Art v 3-specific epitope at the C terminus. Protein variants with exchanged epitope residues confirmed the antibody-binding sites and revealed strongly reduced IgE reactivity. Using the novel HDXMEM for NMR epitope mapping allowed identification of the first structural epitopes of an allergenic pollen LTP. This knowledge enables improved cross-reactivity prediction for patients suffering from LTP allergy and facilitates design of therapeutics.

Glycosylation of recombinant rabbit immunoglobulins influences protease susceptibility as shown by comprehensive mass spectrometric glycan analysis

Recombinant immunoglobulins (rIgGs) have become increasingly important as therapeutic agents and diagnostic tools in recent years. Genetic engineering allows the introduction of non-natural features such as the Sortase motif for site-directed labeling. In this study, the enzyme Sortase A (SrtA) was used for the proteolytic cleavage of rIgGs to produce their biotinylated Fab fragments by locating the cleavage site close to the hinge region. However, SrtA cleavage of engineered rabbit IgGs (rRb-IgGs) derived from human embryonic kidney (HEK) 293 cells showed significantly lower yields compared with their mouse counterparts. Nonrecombinant Rb-IgGs have N- and O-glycans, and the presence of O-glycans close to the hinge region of the rRb-IgGs might affect the susceptibility of these antibodies to SrtA cleavage. In addition, the glycosylation pattern of rIgGs differs depending on the host cell used for expression. Therefore, we analyzed the N- and O-glycans of various rRb-IgGs expressed in HEK293 cells, detecting and quantifying 13 different N-glycan and 3 different O-glycan structures. The distribution of the different detected glycoforms in our rRb-IgG N-glycan analysis is in agreement with previous studies on recombinant human IgG N-glycans, confirming the hypothesis that the host cell defines the glycosylation of the recombinant produced IgGs. O-glycosylation could be mapped onto the threonine residue within the hinge region sequence XPTCPPPX, as already described previously for nonrecombinant Rb-IgGs. Substitution of this threonine allowed an almost complete Fab fragment cleavage. Therefore, we could confirm the hypothesis that the O-glycans affect the SrtA activity, probably due to steric hindrance.

Kinetics of Serological Response in Patients with Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is caused by SFTS virus (SFTSV). We investigated the detailed kinetics of serologic response in patients with SFTS. Twenty-eight patients aged ≥18 years were enrolled between July 2015 and October 2018. SFTS was confirmed by detecting SFTSV RNA in their plasma using reverse transcription polymerase chain reaction. SFTSV-specific IgG and IgM were measured using immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA). We found that SFTSV-specific IgG was detected at days 5–9 after symptom onset, and its titer was rising during the course of disease. SFTSV-specific IgM titer peaked at around week 2–3 from symptom onset. The SFTSV-specific seropositive rates for days 5–9, 10–14, 15–19, and 20–24 from symptom onset using IFA and ELISA were 63%, 76%, 90%, and 100%, and 58%, 86%, 100%, and 100%, respectively, for IgG, whereas they were 32%, 62%, 80%, and 100%, and 53%, 62%, 70%, and 100%, respectively, for IgM. The delayed IgM response could be attributed to the low sensitivity of SFTSV-specific IgM IFA or ELISA and/or impaired immune responses. The IgM test using IFA or ELISA that we used in this study is, therefore, insufficient for the early diagnosis of SFTS.

Structural features of bovine colostral immunoglobulin that confer proteolytic stability in a simulated intestinal fluid

Bovine colostral antibodies, purified from cow's milk produced immediately after calving, have enhanced resistance to degradation by intestinal proteases relative to antibodies from human or bovine serum, making them of particular interest as orally administered therapeutic agents. However, the basis of this resistance is not well defined. We evaluated the stability of AVX-470, a bovine colostral anti-tumor necrosis factor (TNF) polyclonal antibody used in early clinical studies for treatment of ulcerative colitis, using conditions that mimic the human small intestine. AVX-470 was degraded ∼3 times more slowly than human IgG antibodies or infliximab (a monoclonal mouse-human chimeric IgG). Bovine IgG1 antibodies, the primary component of AVX-470, were slowly cleaved to F(ab')2 fragments. In contrast, bovine IgG2 and human IgG1 antibodies were cleaved rapidly into Fab and smaller fragments, pointing to specific regions where additional stability might be gained. Infliximab was modified to incorporate the sequences from these regions, including the bovine IgG1 hinge region and a predicted disulfide bonding motif linking the upper hinge region, the CH1 domain, and the light chain. This infliximab-bovine IgG1 chimera (bovinized infliximab) retained the antigen binding and neutralization activity of the WT sequence but was degraded 9-fold more slowly than the unmodified infliximab. This remarkable increase in stability with as few as 18 amino acid substitutions suggests that this bovinization process is a means to enable oral delivery of proven therapeutic antibodies as well as novel antibodies to targets that have been previously inaccessible to therapies delivered by injection.

Molecular mechanism of the recognition of bacterially cleaved immunoglobulin by the immune regulatory receptor LILRA2

Human leukocyte immunoglobulin-like receptors (LILRs) typically regulate immune activation by binding to the human leukocyte antigen class I molecules. LILRA2, a member of the LILR family, was recently reported to bind to other unique ligands, the bacterially degraded Igs (N-truncated Igs), for the activation of immune cells. Therefore, LILRA2 is currently attracting significant attention as a novel innate immune receptor. However, the detailed recognition mechanisms required for this interaction remain unclear. In this study, using several biophysical techniques, we uncovered the molecular mechanism of N-truncated Ig recognition by LILRA2. Surface plasmon resonance analysis disclosed that LILRA2 specifically binds to N-truncated Ig with weak affinity (K_d = 4.8 μm) and fast kinetics. However, immobilized LILRA2 exhibited a significantly enhanced interaction with N-truncated Ig due to avidity effects. This suggests that cell surface-bound LILRA2 rapidly monitors and identifies bi- or multivalent abnormal N-truncated Igs through specific cross-linking to induce immune activation. Van't Hoff analysis revealed that this interaction is enthalpy-driven, with a small entropy loss, and results from differential scanning calorimetry indicated the instability of the putative LILRA2-binding site, the Fab region of the N-truncated Ig. Atomic force microscopy revealed that N truncation does not cause significant structural changes in Ig. Furthermore, mutagenesis analysis identified the hydrophobic region of LILRA2 domain 2 as the N-truncated Ig-binding site, representing a novel ligand-binding site for the LILR family. These results provide detailed insights into the molecular regulation of LILR-mediated immune responses targeting ligands that have been modified by bacteria.

Role of natural salivary defenses in the maintenance of healthy oral microbiota in children and adolescents

Aim

The present study served the purpose of assessing the levels of salivary immunoglobulin A (IgA), immunoglobulin G (IgG), proteins, calcium, inorganic phosphorus, and alkaline phosphatase levels in caries-free and caries active children.

Materials and Methods

Stratified randomized sampling method was used to include 40 subjects in the age group 12-15 years having a full complement of permanent dentition except for third molars. The selected pediatric subjects were further divided into two groups of 20 each based on DMFS score, Group-I - Caries free (DMFS score = 0) and Group-II - Caries active (DMFS score ≥10). Unstimulated midmorning saliva samples were collected and analyzed colorimetrically and by radial immunodiffusion method for constituents of saliva understudy.

Results

The mean salivary IgA levels in children in Group-I (caries-free children) was 10.63 ± 2.85 mg/dL which was statistically higher as compared to caries active children in Group-II (8.50 ± 1.43 mg/dL).The mean salivary protein level in children of Group-II was statistically higher at 3.28 ± 0.12 mg/dL as compared to Group-I (2.89 ± 0.11 mg/dL).

Conclusion

The present study showed decreased levels of salivary immunoglobulin A and high concentration of salivary protein in children with increased caries experience which is indicative of the protective role of salivary constituents in caries-free children.

Selection of Antibody Responses Associated With Plasmodium falciparum Infections in the Context of Malaria Elimination

In our aim to eliminate malaria, more sensitive tools to detect residual transmission are quickly becoming essential. Antimalarial antibody responses persist in the blood after a malaria infection and provide a wider window to detect exposure to infection compared to parasite detection metrics. Here, we aimed to select antibody responses associated with recent and cumulative exposure to malaria using cross-sectional survey data from Haiti, an elimination setting. Using a multiplex bead assay, we generated data for antibody responses (immunoglobulin G) to 23 Plasmodium falciparum targets in 29,481 participants across three surveys. This included one community-based survey in which participants were enrolled during household visits and two sentinel group surveys in which participants were enrolled at schools and health facilities. First, we correlated continuous antibody responses with age (Spearman) to determine which showed strong age-related associations indicating accumulation over time with limited loss. AMA-1 and MSP-119 antibody levels showed the strongest correlation with age (0.47 and 0.43, p < 0.001) in the community-based survey, which was most representative of the underlying age structure of the population, thus seropositivity to either of these antibodies was considered representative of cumulative exposure to malaria. Next, in the absence of a gold standard for recent exposure, we included antibody responses to the remaining targets to predict highly sensitive rapid diagnostic test (hsRDT) status using receiver operating characteristic curves. For this, only data from the survey with the highest hsRDT prevalence was used (7.2%; 348/4,849). The performance of the top two antigens in the training dataset (two-thirds of the dataset; n = 3,204)-Etramp 5 ag 1 and GLURP-R0 (area-under-the-curve, AUC, 0.892 and 0.825, respectively)-was confirmed in the test dataset (remaining one-third of the dataset; n = 1,652, AUC 0.903 and 0.848, respectively). As no further improvement was seen by combining seropositivity to GLURP-R0 and Etramp 5 ag 1 (p = 0.266), seropositivity to Etramp 5 ag 1 alone was selected as representative of current or recent exposure to malaria. The validation of antibody responses associated with these exposure histories simplifies analyses and interpretation of antibody data and facilitates the application of results to evaluate programs.

Conjugation of Synthetic Trisaccharide of Staphylococcus aureus Type 8 Capsular Polysaccharide Elicits Antibodies Recognizing Intact Bacterium

Staphylococcus aureus causes a wide range of life-threatening diseases. One of the powerful approaches for prevention and treatment is to develop an efficient vaccine as antibiotic resistance greatly increases. S. aureus type 8 capsular polysaccharide (CP8) has shown great potential in vaccine development. An understanding of the immunogenicity of CP8 trisaccharide repeating unit is valuable for epitope-focused vaccine design and cost-efficient vaccine production. We report the chemical synthesis of conjugation-ready CP8 trisaccharide 1 bearing an amine linker, which effectively served for immunological evaluation. The trisaccharide 1-CRM197 conjugate elicited a robust immunoglobulin G (IgG) immune response in mice. Both serum antibodies and prepared monoclonal antibodies recognized S. aureus strain, demonstrating that synthetic trisaccharide 1 can be an efficient antigen for vaccine development.

Glycomic Signatures of Plasma IgG Improve Preoperative Prediction of the Invasiveness of Small Lung Nodules

Preoperative assessment of tumor invasiveness is essential to avoid overtreatment for patients with small-sized ground-glass nodules (GGNs) of 10 mm or less in diameter. However, it is difficult to determine the pathological state by computed tomography (CT) examination alone. Aberrant glycans has emerged as a tool to identify novel potential disease biomarkers. In this study, we used a lectin microarray-based strategy to investigate whether glycosylation changes in plasma immunoglobulin G (IgG) provide additional information about the invasiveness of small GGNs before surgery. Two independent cohorts (discovery set, n = 92; test set, n = 210) of GGN patients were used. Five of 45 lectins (Sambucus nigra agglutinin, SNA; Datura stramonium agglutinin, DSA; Galanthus nivalis agglutinin, GNA; Euonymus europaeus lectin, EEL; and Vicia villosa agglutinin, VVA) were identified as independent factors associated with pathological invasiveness of small GGNs (p < 0.01). Receiver-operating characteristic (ROC) curve analysis indicated the combination of these five lectins could significantly improve the accuracy of CT in diagnosing invasive GGNs, with an area under the curve (AUC) of 0.792 (p < 0.001), a sensitivity of 74.6%, and specificity of 74.4%, which was superior to current clinical biomarkers. These results suggest that the multilectin assay based on plasma IgG glycosylation may be a useful in vitro complementary test to enhance preoperative determination of the invasiveness of GGNs and guide surgeons to select proper clinical management to avoid overtreatment.

The solution structure of the human IgG2 subclass is distinct from those for human IgG1 and IgG4 providing an explanation for their discrete functions

Human IgG2 antibody displays distinct therapeutically-useful properties compared with the IgG1, IgG3, and IgG4 antibody subclasses. IgG2 is the second most abundant IgG subclass, being able to bind human FcγRII/FcγRIII but not to FcγRI or complement C1q. Structural information on IgG2 is limited by the absence of a full-length crystal structure for this. To this end, we determined the solution structure of human myeloma IgG2 by atomistic X-ray and neutron-scattering modeling. Analytical ultracentrifugation disclosed that IgG2 is monomeric with a sedimentation coefficient (s20, w0) of 7.2 S. IgG2 dimer formation was ≤5% and independent of the buffer conditions. Small-angle X-ray scattering in a range of NaCl concentrations and in light and heavy water revealed that the X-ray radius of gyration (Rg ) is 5.2-5.4 nm, after allowing for radiation damage at higher concentrations, and that the neutron Rg value of 5.0 nm remained unchanged in all conditions. The X-ray and neutron distance distribution curves (P(r)) revealed two peaks, M1 and M2, that were unchanged in different buffers. The creation of >123,000 physically-realistic atomistic models by Monte Carlo simulations for joint X-ray and neutron-scattering curve fits, constrained by the requirement of correct disulfide bridges in the hinge, resulted in the determination of symmetric Y-shaped IgG2 structures. These molecular structures were distinct from those for asymmetric IgG1 and asymmetric and symmetric IgG4 and were attributable to the four hinge disulfides. Our IgG2 structures rationalize the existence of the human IgG1, IgG2, and IgG4 subclasses and explain the receptor-binding functions of IgG2.

The Molecular Basis of Human IgG-Mediated Enhancement of C4b-Binding Protein Recruitment to Group A Streptococcus

Streptococcus pyogenes infects over 700 million people worldwide annually. Immune evasion strategies employed by the bacteria include binding of the complement inhibitors, C4b-binding protein (C4BP) and Factor H in a human-specific manner. We recently showed that human IgG increased C4BP binding to the bacterial surface, which promoted streptococcal immune evasion and increased mortality in mice. We sought to identify how IgG promotes C4BP binding to Protein H, a member of the M protein family. Dimerization of Protein H is pivotal for enhanced binding to human C4BP. First, we illustrated that Protein H, IgG, and C4BP formed a tripartite complex. Second, surface plasmon resonance revealed that Protein H binds IgG solely through Fc, but not Fab domains, and with high affinity (IgG-Protein H: K_D = 0.4 nM; IgG-Fc-Protein H: K_D ≤ 1.6 nM). Each IgG binds two Protein H molecules, while up to six molecules of Protein H bind one C4BP molecule. Third, interrupting Protein H dimerization either by raising temperature to 41°C or with a synthetic peptide prevented IgG-Protein H interactions. IgG-Fc fragments or monoclonal human IgG permitted maximal C4BP binding when used at concentrations from 0.1 to 10 mg/ml. In contrast, pooled human IgG enhanced C4BP binding at concentrations up to 1 mg/ml; decreased C4BP binding at 10 mg/ml occurred probably because of Fab-streptococcal interactions at these high IgG concentrations. Taken together, our data show how S. pyogenes exploits human IgG to evade complement and enhance its virulence. Elucidation of this mechanism could aid design of new therapeutics against S. pyogenes.

Screening Naturally Occurring Phenolic Antioxidants for Their Suitability as Additives to CHO Cell Culture Media Used to Produce Monoclonal Antibodies

This study identified several antioxidants that could be used in Chinese hamster ovary (CHO)cell culture media and benefit monoclonal antibody production. The flavan-3-ols, catechin, epicatechin, epigallocatechin gallate and gallocatechin gallate all had no detrimental effect on cell viability at the concentrations tested, and they reduced the final viable cell count with a resulting rise in the cell specific productivity. The flavone, luteolin behave similarly to the flavan-3-ols. Resveratrol at 50 μM concentration resulted in the most pronounced reduction in viable cell density with minimal decrease in IgG synthesis and the largest increase in cell specific productivity. Low concentrations of α-tocopherol (35 μM) reduced viable cell density and raised cell specific productivity, but at higher concentration it had little additional effect. As high concentrations of α-tocopherol are not toxic to CHO cells, its addition as an anti-oxidant has great potential. Kaempferol up to 50 μM, curcumin up to 20 μM and piceid up to 100 μM showed little effect on growth or IgG synthesis and could be useful as antioxidants. Caffeic acid phenethyl ester was toxic to CHO cell and of no interest. Seven of the phenolic compounds tested are potential cell cycle inhibitors as well as having intrinsic antioxidant properties.

Serologic and viral genome prevalence of HSV, EBV, and HCMV among healthy adults in Wuhan, China

The worldwide infection rate of herpesvirus is high, but the detailed prevalence in China, especially the central area, remains unclear. In the present study, the prevalence of herpes simplex virus (HSV), Epstein-Barr virus (EBV), and human cytomegalovirus (HCMV) was investigated in 303 healthy adults in Wuhan, a representative city in Central China. Viral-specific IgG and IgM titers were examined in the serum by chemiluminescent immunoassay, and the existence of viral genomic DNA in blood cells was determined by nested PCR. The overall IgG seroprevalences were 81.5%, 95.4%, and 93.7% for HSV, EBV, and HCMV, while the corresponding IgM seroprevalences were only 6.3%, 2.3%, and 0. The viral genomic DNA of HSV, EBV, and HCMV was identified in the blood samples of 5.9%, 14.2%, and 22.8% of the tested donors, respectively. Significantly, less HSV IgM-positive samples were found in the population over 20 years old than below 20 group; female displayed higher chances for HSV IgG and genome positivity; and occupations such as waiters and medical staffs were shown to be with higher risk for HCMV genome positivity. This study provided useful reference data for the HSV, EBV, and HCMV prevalence in central China, and suggested the potential importance of detecting viral genome to complement serum test data.

Impact of host cell line choice on glycan profile

Protein glycosylation is post-translational modification (PTM) which is important for pharmacokinetics and immunogenicity of recombinant glycoprotein therapeutics. As a result of variations in monosaccharide composition, glycosidic linkages and glycan branching, glycosylation introduces considerable complexity and heterogeneity to therapeutics. The host cell line used to produce the glycoprotein has a strong influence on the glycosylation because different host systems may express varying repertoire of glycosylation enzymes and transporters that contributes to specificity and heterogeneity in glycosylation profiles. In this review, we discuss the types of host cell lines currently used for recombinant therapeutic production, their glycosylation potential and the resultant impact on glycoprotein properties. In addition, we compare the reported glycosylation profiles of four recombinant glycoproteins: immunoglobulin G (IgG), coagulation factor VII (FVII), erythropoietin (EPO) and alpha-1 antitrypsin (A1AT) produced in different mammalian cells to establish the influence of mammalian host cell lines on glycosylation.

Molecular characterization of human anti-hinge antibodies derived from single-cell cloning of normal human B cells

Anti-hinge antibodies (AHAs) are an autoantibody subclass that, following proteolytic cleavage, recognize cryptic epitopes exposed in the hinge regions of immunoglobulins (Igs) and do not bind to the intact Ig counterpart. AHAs have been postulated to exacerbate chronic inflammatory disorders such as inflammatory bowel disease and rheumatoid arthritis. On the other hand, AHAs may protect against invasive microbial pathogens and cancer. However, despite more than 50 years of study, the origin and specific B cell compartments that express AHAs remain elusive. Recent research on serum AHAs suggests that they arise during an active immune response, in contrast to previous proposals that they derive from the preexisting immune repertoire in the absence of antigenic stimuli. We report here the isolation and characterization of AHAs from memory B cells, although anti-hinge-reactive B cells were also detected in the naive B cell compartment. IgG AHAs cloned from a single human donor exhibited restricted specificity for protease-cleaved F(ab')₂ fragments and did not bind the intact IgG counterpart. The cloned IgG-specific AHA-variable regions were mutated from germ line-derived sequences and displayed a high sequence variability, confirming that these AHAs underwent class-switch recombination and somatic hypermutation. Consistent with previous studies of serum AHAs, several of these clones recognized a linear, peptide-like epitope, but one clone was unique in recognizing a conformational epitope. All cloned AHAs could restore immune effector functions to proteolytically generated F(ab')₂ fragments. Our results confirm that a diverse set of epitope-specific AHAs can be isolated from a single human donor.

Structural basis for pH-insensitive inhibition of immunoglobulin G recycling by an anti-neonatal Fc receptor antibody

The neonatal Fc receptor FcRn plays a critical role in the trafficking of IgGs across tissue barriers and in retaining high circulating concentrations of both IgG and albumin. Although generally beneficial from an immunological perspective in maintaining IgG populations, FcRn can contribute to the pathogenesis of autoimmune disorders when an abnormal immune response targets normal biological components. We previously described a monoclonal antibody (DX-2507) that binds to FcRn with high affinity at both neutral and acidic pH, prevents the simultaneous binding of IgG, and reduces circulating IgG levels in preclinical animal models. Here, we report a 2.5 Å resolution X-ray crystal structure of an FcRn-DX-2507 Fab complex, revealing a nearly complete overlap of the IgG-Fc binding site in FcRn by complementarity-determining regions in DX-2507. This overlap explains how DX-2507 blocks IgG binding to FcRn and thereby shortens IgG half-life by preventing IgGs from recycling back into circulation. Moreover, the complex structure explains how the DX-2507 interaction is pH-insensitive unlike normal Fc interactions and how serum albumin levels are unaffected by DX-2507 binding. These structural studies could inform antibody-based therapeutic approaches for limiting the effects of IgG-mediated autoimmune disease.

A new approach for generating bispecific antibodies based on a common light chain format and the stable architecture of human immunoglobulin G1

Bispecific antibodies combine two different antigen-binding sites in a single molecule, enabling more specific targeting, novel mechanisms of action, and higher clinical efficacies. Although they have the potential to outperform conventional monoclonal antibodies, many bispecific antibodies have issues regarding production, stability, and pharmacokinetic properties. Here, we describe a new approach for generating bispecific antibodies using a common light chain format and exploiting the stable architecture of human immunoglobulin G₁ We used iterative experimental validation and computational modeling to identify multiple Fc variant pairs that drive efficient heterodimerization of the antibody heavy chains. Accelerated stability studies enabled selection of one Fc variant pair dubbed "DEKK" consisting of substitutions L351D and L368E in one heavy chain combined with L351K and T366K in the other. Solving the crystal structure of the DEKK Fc region at a resolution of 2.3 Å enabled detailed analysis of the interactions inducing CH3 interface heterodimerization. Local shifts in the IgG backbone accommodate the introduction of lysine side chains that form stabilizing salt-bridge interactions with substituted and native residues in the opposite chain. Overall, the CH3 domain adapted to these shifts at the interface, yielding a stable Fc conformation very similar to that in wild-type IgG. Using the DEKK format, we generated the bispecific antibody MCLA-128, targeting human EGF receptors 2 and 3. MCLA-128 could be readily produced and purified at industrial scale with a standard mammalian cell culture platform and a routine purification protocol. Long-term accelerated stability assays confirmed that MCLA-128 is highly stable and has excellent biophysical characteristics.

Engineering the fragment crystallizable (Fc) region of human IgG1 multimers and monomers to fine-tune interactions with sialic acid-dependent receptors

Multimeric fragment crystallizable (Fc) regions and Fc-fusion proteins are actively being explored as biomimetic replacements for IVIG therapy, which is deployed to manage many diseases and conditions but is expensive and not always efficient. The Fc region of human IgG1 (IgG1-Fc) can be engineered into multimeric structures (hexa-Fcs) that bind their cognate receptors with high avidity. The critical influence of the unique N-linked glycan attached at Asn-297 on the structure and function of IgG1-Fc is well documented; however, whether the N-linked glycan has a similarly critical role in multimeric, avidly binding Fcs, is unknown. Hexa-Fc contains two N-linked sites at Asn-77 (equivalent to Asn-297 in the Fc of IgG1) and Asn-236 (equivalent to Asn-563 in the tail piece of IgM). We report here that glycosylation at Asn-297 is critical for interactions with Fc receptors and complement and that glycosylation at Asn-563 is essential for controlling multimerization. We also found that introduction of an additional fully occupied N-linked glycosylation site at the N terminus at position 1 (equivalent to Asp-221 in the Fc of IgG1) dramatically enhances overall sialic acid content of the Fc multimers. Furthermore, replacement of Cys-575 in the IgM tail piece of multimers resulted in monomers with enhanced sialic acid content and differential receptor-binding profiles. Thus insertion of additional N-linked glycans into either the hinge or tail piece of monomers or multimers leads to molecules with enhanced sialylation that may be suitable for managing inflammation or blocking pathogen invasion.

Cytoplasmic poly(A)-binding protein 1 (PABPC1) interacts with the RNA-binding protein hnRNPLL and thereby regulates immunoglobulin secretion in plasma cells

Increasing evidence indicates that alternative processing of mRNA, including alternative splicing, 3' alternative polyadenylation, and regulation of mRNA stability/translation, represents a major mechanism contributing to protein diversification. For example, in alternative polyadenylation, the 3' end of the immunoglobulin heavy chain mRNA is processed during B cell differentiation, and this processing involves RNA-binding proteins. hnRNPLL (heterogeneous nuclear ribonucleoprotein L-like protein) is an RNA-binding protein expressed in terminally differentiated lymphocytes, such as memory T cells and plasma cells. hnRNPLL regulates various processes of RNA metabolism, including alternative pre-mRNA splicing and RNA stability. In plasma cells, hnRNPLL also regulates the transition from the membrane isoform of the immunoglobulin heavy-chain (mIgH) to the secreted isoform (sIgH), but the precise mechanism remains to be identified. In this study, we report that hnRNPLL specifically associates with cytoplasmic PABPC1 (poly(A)-binding protein 1) in both T cells and plasma cells. We found that although PABPC1 is not required for the alternative splicing of CD45, a primary target of hnRNPLL in lymphocytes, PABPC1 does promote the binding of hnRNPLL to the immunoglobulin mRNA and regulates switching from mIgH to sIgH in plasma cells. Given the recently identified role of PABPC1 in mRNA alternative polyadenylation, our findings suggest that PABPC1 recruits hnRNPLL to the 3'-end of RNA and regulates the transition from membrane Ig to secreted Ig through mRNA alternative polyadenylation. In conclusion, our study has revealed a mechanism that regulates immunoglobulin secretion in B cells via cooperation between a plasma cell-specific RBP (hnRNPLL) and a universally expressed RBP (PABPC1).

An antidote approach to reduce risk and broaden utility of antibody-based therapeutics

Antibody therapeutics offer effective treatment options for a broad range of diseases. One of the greatest benefits of antibody therapeutics is their extraordinarily long serum half-life, allowing infrequent dosing with long-lasting effects. A characteristic of antibodies that drives long half-life is the ability to interact with the recycling receptor, FcRn, in a pH-dependent manner. The benefit of long half-life, however, carries with it liabilities. Although the positive effects of antibody therapeutics are long-lasting, any acute adverse events or chronic negative impacts, such as immunosuppression in the face of an infection, are also long-lasting. Therefore, we sought to develop antibodies with a chemical handle that alone would enjoy the long half-life of normal antibodies but, upon addition of a small-molecule antidote, would interact with the chemical handle and inhibit the antibody recycling mechanism, thus leading to rapid degradation and shortened half-life in vivo Here we present a proof of concept study where we identify sites to incorporate a non-natural amino acid that can be chemically modified to modulate FcRn interaction in vitro and antibody half-life in vivo This is an important first step in developing safer therapeutics, and the next step will be development of technology that can perform the modifying chemistry in vivo.

Engineering an IgG Scaffold Lacking Effector Function with Optimized Developability

IgG isotypes can differentially bind to Fcγ receptors and complement, making the selection of which isotype to pursue for development of a particular therapeutic antibody important in determining the safety and efficacy of the drug. IgG2 and IgG4 isotypes have significantly lower binding affinity to Fcγ receptors. Recent evidence suggests that the IgG2 isotype is not completely devoid of effector function, whereas the IgG4 isotype can undergo in vivo Fab arm exchange leading to bispecific antibody and off-target effects. Here an attempt was made to engineer an IgG1-based scaffold lacking effector function but with stability equivalent to that of the parent IgG1. Care was taken to ensure that both stability and lack of effector function was achieved with a minimum number of mutations. Among the Asn²⁹⁷ mutants that result in lack of glycosylation and thus loss of effector function, we demonstrate that the N297G variant has better stability and developability compared with the N297Q or N297A variants. To further improve the stability of N297G, we introduced a novel engineered disulfide bond at a solvent inaccessible location in the CH2 domain. The resulting scaffold has stability greater than or equivalent to that of the parental IgG1 scaffold. Extensive biophysical analyses and pharmacokinetic (PK) studies in mouse, rat, and monkey further confirmed the developability of this unique scaffold, and suggest that it could be used for all Fc containing therapeutics (e.g. antibodies, bispecific antibodies, and Fc fusions) requiring lack of effector function or elimination of binding to Fcγ receptors.

Biological Characterization of a Stable Effector Functionless (SEFL) Monoclonal Antibody Scaffold in Vitro

The stable effector functionLess (SEFL) antibody was designed as an IgG1 antibody with a constant region that lacks the ability to interact with Fcγ receptors. The engineering and stability and pharmacokinetic assessments of the SEFL scaffold is described in the accompanying article (Jacobsen, F. W., Stevenson, R., Li, C., Salimi-Moosavi, H., Liu, L., Wen, J., Luo, Q., Daris, K., Buck, L., Miller, S., Ho, S-Y., Wang, W., Chen, Q., Walker, K., Wypych, J., Narhi, L., and Gunasekaran, K. (2017) J. Biol. Chem 292). The biological properties of these SEFL antibodies were assessed in a variety of human and cynomolgus monkey in vitro assays. Binding of parent molecules and their SEFL variants to human and cynomolgus monkey FcγRs were evaluated using flow cytometry-based binding assays. The SEFL variants tested showed decreased binding affinity to human and cynomolgus FcγRs compared with the wild-type IgG1 antibody. In addition, SEFL variants demonstrated no antibody-dependent cell-mediated cytotoxicity in vitro against Daudi cells with cynomolgus monkey peripheral blood mononuclear cells, and had minimal complement-dependent cytotoxicity activity similar to that of the negative control IgG2 in a CD20⁺ human Raji lymphoma cell line. SEFL mutations eliminated off-target antibody-dependent monocyte phagocytosis of cynomolgus monkey platelets, and cynomolgus platelet activation in vitro These experiments demonstrate that the SEFL modifications successfully eliminated Fc-associated effector binding and functions.

Pharmacokinetic properties of IgG and various Fc fusion proteins in mice

Fusion to an IgG Fc region is an established strategy to extend the half-life of therapeutic proteins. Most Fc fusion proteins, however, do not achieve the long half-life of IgGs. Based on findings that scFv-Fc fusion proteins exhibit a shorter half-life than the corresponding IgG molecules, we performed a comparative study of different antibody-derived Fc fusion proteins. We could confirm that fusion of single-chain Fv (scFv) and single-chain diabody (scDb) molecules to an Fc region yields in fusion proteins with substantially extended half-lives compared with the single-chain versions. However, even fusion proteins with a size similar to that of IgG, e.g., scDb-Fc, did not have a half-life as long as an IgG molecule. Binding to the neonatal Fc receptor (FcRn) under acidic and neutral conditions was similar for IgG and all Fc fusion proteins. However, we observed differences between IgG and the Fc fusion proteins for dissociation of FcRn-bound proteins induced by shifting from acidic to neutral pH, reflecting the physiological release mechanism, further supporting a contribution of the kinetics of pH-dependent release from FcRn to the pharmacokinetic properties of IgG and Fc fusion proteins.

Neuroimmunological Implications of AQP4 in Astrocytes

The brain has high-order functions and is composed of several kinds of cells, such as neurons and glial cells. It is becoming clear that many kinds of neurodegenerative diseases are more-or-less influenced by astrocytes, which are a type of glial cell. Aquaporin-4 (AQP4), a membrane-bound protein that regulates water permeability is a member of the aquaporin family of water channel proteins that is expressed in the endfeet of astrocytes in the central nervous system (CNS). Recently, AQP4 has been shown to function, not only as a water channel protein, but also as an adhesion molecule that is involved in cell migration and neuroexcitation, synaptic plasticity, and learning/memory through mechanisms involved in long-term potentiation or long-term depression. The most extensively examined role of AQP4 is its ability to act as a neuroimmunological inducer. Previously, we showed that AQP4 plays an important role in neuroimmunological functions in injured mouse brain in concert with the proinflammatory inducer osteopontin (OPN). The aim of this review is to summarize the functional implication of AQP4, focusing especially on its neuroimmunological roles. This review is a good opportunity to compile recent knowledge and could contribute to the therapeutic treatment of autoimmune diseases through strategies targeting AQP4. Finally, the author would like to hypothesize on AQP4’s role in interaction between reactive astrocytes and reactive microglial cells, which might occur in neurodegenerative diseases. Furthermore, a therapeutic strategy for AQP4-related neurodegenerative diseases is proposed.

Evading pre-existing anti-hinge antibody binding by hinge engineering

Antigen-binding fragments (Fab) and F(ab')₂ antibodies serve as alternative formats to full-length anti-bodies in therapeutic and immune assays. They provide the advantage of small size, short serum half-life, and lack of effector function. Several proteases associated with invasive diseases are known to cleave antibodies in the hinge-region, and this results in anti-hinge antibodies (AHA) toward the neoepitopes. The AHA can act as surrogate Fc and reintroduce the properties of the Fc that are otherwise lacking in antibody fragments. While this response is desired during the natural process of fighting disease, it is commonly unwanted for therapeutic antibody fragments. In our study, we identify a truncation in the lower hinge region of the antibody that maintains efficient proteolytic cleavage by IdeS protease. The resulting neoepitope at the F(ab')₂ C-terminus does not have detectable binding of pre-existing AHA, providing a practical route to produce F(ab')₂ in vitro by proteolytic digestion when the binding of pre-existing AHA is undesired. We extend our studies to the upper hinge region of the antibody and provide a detailed analysis of the contribution of C-terminal residues of the upper hinge of human IgG1, IgG2 and IgG4 to pre-existing AHA reactivity in human serum. While no pre-existing antibodies are observed toward the Fab of IgG2 and IgG4 isotype, a significant response is observed toward most residues of the upper hinge of human IgG1. We identify a T₂₂₅L variant and the natural C-terminal D₂₂₁ as solutions with minimal serum reactivity. Our work now enables the production of Fab and F(ab')₂ for therapeutic and diagnostic immune assays that have minimal reactivity toward pre-existing AHA.

Identification and Characterization of IgdE, a Novel IgG-degrading Protease of Streptococcus suis with Unique Specificity for Porcine IgG

Streptococcus suisis a major endemic pathogen of pigs causing meningitis, arthritis, and other diseases. ZoonoticS. suisinfections are emerging in humans causing similar pathologies as well as severe conditions such as toxic shock-like syndrome. Recently, we discovered an IdeS family protease ofS. suisthat exclusively cleaves porcine IgM and represents the first virulence factor described, linkingS. suisto pigs as their natural host. Here we report the identification and characterization of a novel, unrelated protease ofS. suisthat exclusively targets porcine IgG. This enzyme, designated IgdE forimmunoglobulinG-degradingenzyme ofS. suis, is a cysteine protease distinct from previous characterized streptococcal immunoglobulin degrading proteases of the IdeS family and mediates efficient cleavage of the hinge region of porcine IgG with a high degree of specificity. The findings that allS. suisstrains investigated possess the IgG proteolytic activity and that piglet serum samples contain specific antibodies against IgdE strongly indicate that the protease is expressedin vivoduring infection and represents a novel and putative important bacterial virulence/colonization determinant, and a thus potential therapeutic target.

Targeting Stereotyped B Cell Receptors from Chronic Lymphocytic Leukemia Patients with Synthetic Antigen Surrogates

Chronic lymphocytic leukemia (CLL) is a disease in which a single B-cell clone proliferates relentlessly in peripheral lymphoid organs, bone marrow, and blood. DNA sequencing experiments have shown that about 30% of CLL patients have stereotyped antigen-specific B-cell receptors (BCRs) with a high level of sequence homology in the variable domains of the heavy and light chains. These include many of the most aggressive cases that haveIGHV-unmutated BCRs whose sequences have not diverged significantly from the germ line. This suggests a personalized therapy strategy in which a toxin or immune effector function is delivered selectively to the pathogenic B-cells but not to healthy B-cells. To execute this strategy, serum-stable, drug-like compounds able to target the antigen-binding sites of most or all patients in a stereotyped subset are required. We demonstrate here the feasibility of this approach with the discovery of selective, high affinity ligands for CLL BCRs of the aggressive, stereotyped subset 7P that cross-react with the BCRs of several CLL patients in subset 7p, but not with BCRs from patients outside this subset.

Conformational Destabilization of Immunoglobulin G Increases the Low pH Binding Affinity with the Neonatal Fc Receptor

Crystallographic evidence suggests that the pH-dependent affinity of IgG molecules for the neonatal Fc receptor (FcRn) receptor primarily arises from salt bridges involving IgG histidine residues, resulting in moderate affinity at mildly acidic conditions. However, this view does not explain the diversity in affinity found in IgG variants, such as the YTE mutant (M252Y,S254T,T256E), which increases affinity to FcRn by up to 10×. Here we compare hydrogen exchange measurements at pH 7.0 and pH 5.5 with and without FcRn bound with surface plasmon resonance estimates of dissociation constants and FcRn affinity chromatography. The combination of experimental results demonstrates that differences between an IgG and its cognate YTE mutant vary with their pH-sensitive dynamics prior to binding FcRn. The conformational dynamics of these two molecules are nearly indistinguishable upon binding FcRn. We present evidence that pH-induced destabilization in the CH2/3 domain interface of IgG increases binding affinity by breaking intramolecular H-bonds and increases side-chain adaptability in sites that form intermolecular contacts with FcRn. Our results provide new insights into the mechanism of pH-dependent affinity in IgG-FcRn interactions and exemplify the important and often ignored role of intrinsic conformational dynamics in a protein ligand, to dictate affinity for biologically important receptors.