Role of the IgM Fc Receptor in Immunity and Tolerance

Functions of IgM fc receptor (FcµR) related to autoimmunity

Unlike Fc receptors for switched immunoglobulin (Ig) isotypes, Fc receptor for IgM (FcµR) is selectively expressed by lymphocytes. The ablation of the FcµR gene in mice impairs B cell tolerance as evidenced by concomitant production of autoantibodies of IgM and IgG isotypes. In this essay, we reiterate the autoimmune phenotypes observed in mutant mice, ie IgM homeostasis, dysregulated humoral immune responses including autoantibodies, and Mott cell formation. We also propose the potential phenotypes in individuals with FCMR deficiency and the model for FcµR-mediated regulation of self-reactive B cells.

The Pathogenic Role of Anti-Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies in the Nocardiosis with the Central Nervous System Involvement

PURPOSE

Anti-granulocyte-macrophage colony-stimulating factor autoantibodies (anti-GM-CSF Abs) are implicated in the pathogenesis of Cryptococcus gattii (C. gattii) infection and pulmonary alveolar proteinosis (PAP). Their presence has also been noted in nocardiosis cases, particularly those with disseminated disease. This study delineates a case series characterizing clinical features and specificity of anti-GM-CSF Abs in nocardiosis patients.

METHODS

In this study, eight patients were recruited to determine the presence or absence of anti-GM-CSF Abs. In addition to the detailed description of the clinical course, we thoroughly investigated the autoantibodies regarding the characteristics, isotypes, subclasses, titers, and neutralizing capacities by utilizing the plasma samples from patients.

RESULTS

Of eight patients, five tested positive for anti-GM-CSF Abs, all with central nervous system (CNS) involvement; patients negative for these antibodies did not develop CNS nocardiosis. Distinct from previously documented cases, none of our patients with anti-GM-CSF Abs exhibited PAP symptoms. The titer and neutralizing activity of anti-GM-CSF Abs in our cohort did not significantly deviate from those found in C. gattii cryptococcosis and PAP patients. Uniquely, one individual (Patient 3) showed a minimal titer and neutralizing action of anti-GM-CSF Abs, with no relation to disease severity. Moreover, IgM autoantibodies were notably present in all CNS nocardiosis cases investigated.

CONCLUSION

The presence of anti-GM-CSF Abs suggests an intrinsic immunodeficiency predisposing individuals toward CNS nocardiosis. The presence of anti-GM-CSF Abs helps to elucidate vulnerability to CNS nocardiosis, even with low titer of autoantibodies. Consequently, systematic screening for anti-GM-CSF Abs should be considered a crucial diagnostic step for nocardiosis patients.

Development of an immunoinflammatory indicator-related dynamic nomogram based on machine learning for the prediction of intravenous immunoglobulin-resistant Kawasaki disease patients

BACKGROUND

Approximately 10-20% of Kawasaki disease (KD) patients suffer from intravenous immunoglobulin (IVIG) resistance, placing them at higher risk of developing coronary artery aneurysms. Therefore, we aimed to construct an IVIG resistance prediction tool for children with KD in Shanghai, China.

METHODS

Retrospective analysis was conducted on data from 1271 patients diagnosed with KD and the patients were randomly divided into a training set and a validation set in a 2:1 ratio. Machine learning algorithms were employed to identify important predictors associated with IVIG resistance and to build a predictive model. The best-performing model was used to construct a dynamic nomogram. Moreover, receiver operating characteristic curves, calibration plots, and decision-curve analysis were utilized to measure the discriminatory power, accuracy, and clinical utility of the nomogram.

RESULTS

Six variables were identified as important predictors, including C-reactive protein, neutrophil ratio, procalcitonin, CD3 ratio, CD19 count, and IgM level. A dynamic nomogram constructed with these factors was available at https://hktk.shinyapps.io/dynnomapp/. The nomogram demonstrated good diagnostic performance in the training and validation sets (area under the receiver operating characteristic curve = 0.816 and 0.800, respectively). Moreover, the calibration curves and decision curves analysis indicated that the nomogram showed good consistency between predicted and actual outcomes and had good clinical benefits.

CONCLUSION

A web-based dynamic nomogram for IVIG resistance was constructed with good predictive performance, which can be used as a practical approach for early screening to assist physicians in personalizing the treatment of KD patients in Shanghai.

New Means and Challenges in the Targeting of BTK

Bruton's tyrosine kinase (BTK) is central to the survival of malignant and normal B lymphocytes and has been a crucial therapeutic target of several generations of kinase inhibitors and newly developed degraders. These new means for targeting BTK have added additional agents to the armamentarium for battling cancers dependent on B-cell receptor (BCR) signaling, including chronic lymphocytic leukemia and other non-Hodgkin lymphomas. However, the development of acquired resistance mutations to each of these classes of BTK inhibitors has led to new challenges in targeting BTK as well as novel insights into BCR signaling. The first-generation covalent BTK inhibitor ibrutinib is susceptible to mutations affecting the covalent binding site, cysteine 481 (C481). Newer noncovalent BTK inhibitors, such as pirtobrutinib, overcome C481 mutation-mediated resistance but are susceptible to other kinase domain mutations, particularly at residues Threonine 474 and Leucine 528. In addition, these novel BTK inhibitor resistance mutations have been shown biochemically and in patients to cause cross-resistance to some covalent BTK inhibitors. Importantly, newer generation covalent BTK inhibitors zanubrutinib and acalabrutinib are susceptible to the same mutations that confer resistance to noncovalent inhibitors. The BTK L528W mutation is of particular interest as it disrupts the kinase activity of BTK, rendering it kinase dead. This observation suggests that BTK may act independently of its kinase activity as a scaffold. Thus, the timely development of BTK degrading proteolysis targeting drugs has allowed for degradation, rather than just enzymatic inhibition, of BTK in B-cell lymphomas, and early clinical trials to evaluate BTK degraders are underway.

Characterization of a membrane Fcγ receptor in largemouth bass (Micropterus saloumoides) and its response to bacterial challenge

Fc receptors (FcRs), specific to the Fc portion of immunoglobulin (Ig), are required to regulate immune responses against pathogenic infections. However, FcγR is a member of FcRs family, whose structure and function remains to be elucidated in teleost fish. In this study, the FcγRII, from largemouth bass (Micropterus saloumoides), named membrane MsFcγRII (mMsFcγRII), was cloned and identified. The opening reading frame (ORF) of mMsFcγRII was 750 bp, encoding 249 amino acids with a predicted molecular mass of 27 kDa. The mMsFcγRII contained a signal peptide, two Ig domains, a transmembrane domain, and an intracellular region, which was highly homology with FcγR from other teleost fish. The mRNA expression analysis showed that mMsFcγRII was widely distributed in all tested tissues and with the highest expression level in spleen. After bacterial challenge, the expression of mMsFcγRII was significantly upregulated in vivo (spleen and head kidney), as well as in vitro (leukocytes from head kidney). The subcellular localization assay revealed that mMsFcγRII was mostly observed on the membrane of HEK293T cells which were transfected with mMsFcγRII overexpression plasmid. Flow cytometric analysis showed that natural mMsFcγRII protein was highly expressed in head kidney lymphocytes. Moreover, indirect immunofluorescence assay and pull-down assay indicated that mMsFcγRII could bind to IgM purified from largemouth bass serum. These results suggested that mMsFcγRII was likely to play an influential role in the immune response against pathogens and provided valuable insights for studying the function of FcRs in teleost.

A natural IgM hitchhiking strategy for delivery of cancer nanovaccines to splenic marginal zone B cells

B cell-targeted cancer vaccines are receiving increasing attention in immunotherapy due to the combined antibody-secreting and antigen-presenting functions. In this study, we propose a natural IgM-hitchhiking delivery strategy to co-deliver tumor antigens and adjuvants to splenic marginal zone B (MZB) cells. We constructed nanovaccines (FA-sLip/OVA/MPLA) consisting of classical folic acid (FA)-conjugated liposomes co-loaded with ovalbumin (OVA) and toll-like receptor 4 agonists, MPLA. We found that natural IgM absorption could be manipulated at the bio-nano interface on FA-sLip/OVA/MPLA, enabling targeted delivery to splenic MZB cells. Systemic administration of FA-sLip/OVA/MPLA effectively activated splenic MZB cells via IgM-mediated multiplex pathways, eliciting antigen-specific humoral and cytotoxic T lymphocyte responses, and ultimately retarding E.G7-OVA tumor growth. In addition, combining FA-sLip/OVA/MPLA immunization with anti-PD-1 treatments showed improved antitumor efficiency. Overall, this natural IgM-hitchhiking delivery strategy holds great promise for efficient, splenic MZB cell-targeted delivery of cancer vaccines in future applications.

Secreted IgM modulates IL-10 expression in B cells

IL-10+ B cells are critical for immune homeostasis and restraining immune responses in infection, cancer, and inflammation; however, the signals that govern IL-10+ B cell differentiation are ill-defined. Here we find that IL-10+ B cells expand in mice lacking secreted IgM ((s)IgM-/-) up to 10-fold relative to wildtype (WT) among all major B cell and regulatory B cell subsets. The IL-10+ B cell increase is polyclonal and presents within 24 hours of birth. In WT mice, sIgM is produced prenatally and limits the expansion of IL-10+ B cells. Lack of the high affinity receptor for sIgM, FcμR, in B cells translates into an intermediate IL-10+ B cell phenotype relative to WT or sIgM-/- mice. Our study thus shows that sIgM regulates IL-10 programming in B cells in part via B cell-expressed FcμR, thereby revealing a function of sIgM in regulating immune homeostasis.

Protective effect of Macleaya cordata isoquinoline alkaloids on lipopolysaccharide-induced liver injury in broilers

OBJECTIVE

This experiment aimed to explore the protective action of dietary supplementation with isoquinoline alkaloids (IA) from Macleaya cordata on lipopolysaccharide (LPS)-induced liver injury in broilers.

METHODS

Total 216 healthy broilers were selected in a 21-d trial and assigned randomly to the following 3 treatments: control (CON) group, LPS group, and LPS+IA group. The CON and LPS groups were provided with a basal diet, whereas the LPS+IA group received the basal diet supplemented with 0.6 mg/kg Macleaya cordata IA. Broilers in LPS and LPS+IA groups were intraperitoneally injected with LPS (1 mg/kg body weight) at 17, 19, and 21 days of age, while those in CON group were injected with equivalent amount of saline solution.

RESULTS

Results showed LPS injection caused systemic and liver inflammation in broilers, inhibited immune function, and ultimately lead to liver injury. By contrast, supplementation of IA ameliorated LPS-induced adverse change in serum parameters, boosted immunity in LPS+IA group. Furthermore, IA suppressed the elevation of hepatic inflammatory cytokines and caspases levels induced by LPS, as well as the expressions of genes related to the tolllike receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factorkappa B (NF-κB) pathway.

CONCLUSION

Dietary inclusion of 0.6 mg/kg Macleaya cordata IA could enhance immune function of body and inhibit liver damage via inactivating TLR4/MyD88/NF-κB signaling pathway in broilers.

Mice possess a more limited natural antihuman factor VIII antibody repertoire than humans that is produced disproportionately by marginal zone B cells

BACKGROUND

One-third of patients with severe hemophilia A develop neutralizing antibodies to the factor VIII (FVIII) protein in response to intravenous replacement therapy. Patients may also generate natural, nonneutralizing antibodies to FVIII before FVIII exposure. These patients are at increased risk of developing neutralizing antibodies to FVIII. However, natural anti-FVIII antibodies are also present in healthy human donors.

OBJECTIVES

To further characterize the natural antihuman (h) FVIII antibody repertoire in mice and humans.

METHODS

An in-house ELISA was developed using a purified polyclonal immunoglobulin (Ig) standard to quantify anti-hFVIII Ig in cell culture supernatant or plasma from mice (wild-type and FVIII-/-) and adult human donors.

RESULTS

All naïve wild-type and FVIII-/- mice, as well as healthy human donors, possess natural anti-hFVIII antibodies. Mice only have natural anti-hFVIII IgM, which is present in germ-free mice, suggesting that they are germline encoded. Although murine marginal zone B cells (MZBs) contribute 44% to all circulating natural IgM, they contribute disproportionately to the anti-hFVIII IgM repertoire (82%). This naturally occurring murine MZB-derived IgM is not B-domain specific and is reduced by intravenously administered hFVIII, suggesting that it may form immune complexes immediately upon hFVIII administration. Natural anti-hFVIII antibodies of IgG, IgM, and IgA isotypes can be detected in adult human donors. There were increased levels of B-domain-favoring anti-hFVIII IgG in 14% of healthy donors, which were markedly different from the rest of the "low-titer" population.

CONCLUSIONS

There is a preponderance of natural anti-hFVIII antibodies in both mice and healthy adult human donors.

Signal-to-noise ratio to assess magnitude, kinetics and impact on pharmacokinetics of the immune response to an adalimumab biosimilar

Background: The antidrug antibody (ADA) signal-to-noise (S/N) ratio was explored as a novel immunogenicity measure to evaluate the immune response of healthy subjects to a single dose of GP2017, an adalimumab biosimilar. Methodology/results: Bioanalytical methods used for the analysis of ADA S/N ratios and ADA titers were validated for sensitivity, precision and drug interference. ADA S/N ratios strongly correlated with ADA titers. Correlations between ADA area under the curve and ADAmax and pharmacokinetics (PK) were stronger for ADA S/N ratio than for ADA titers. Conclusion: ADA S/N ratio allowed for a more sensitive evaluation of the magnitude and kinetics of the immune response, was better correlated with adalimumab PK and was superior to ADA titers in assessing the impact of the immune response on PK.

Liver macrophages and sinusoidal endothelial cells execute vaccine-elicited capture of invasive bacteria

Vaccination has substantially reduced the morbidity and mortality of bacterial diseases, but mechanisms of vaccine-elicited pathogen clearance remain largely undefined. We report that vaccine-elicited immunity against invasive bacteria mainly operates in the liver. In contrast to the current paradigm that migrating phagocytes execute vaccine-elicited immunity against blood-borne pathogens, we found that invasive bacteria are captured and killed in the liver of vaccinated host via various immune mechanisms that depend on the protective potency of the vaccine. Vaccines with relatively lower degrees of protection only activated liver-resident macrophage Kupffer cells (KCs) by inducing pathogen-binding immunoglobulin M (IgM) or low amounts of IgG. IgG-coated pathogens were directly captured by KCs via multiple IgG receptors FcγRs, whereas IgM-opsonized bacteria were indirectly bound to KCs via complement receptors of immunoglobulin superfamily (CRIg) and complement receptor 3 (CR3) after complement C3 activation at the bacterial surface. Conversely, the more potent vaccines engaged both KCs and liver sinusoidal endothelial cells by inducing higher titers of functional IgG antibodies. Endothelial cells (ECs) captured densely IgG-opsonized pathogens by the low-affinity IgG receptor FcγRIIB in a "zipper-like" manner and achieved bacterial killing predominantly in the extracellular milieu via an undefined mechanism. KC- and endothelial cell-based capture of antibody-opsonized bacteria also occurred in FcγR-humanized mice. These vaccine protection mechanisms in the liver not only provide a comprehensive explanation for vaccine-/antibody-boosted immunity against invasive bacteria but also may serve as in vivo functional readouts of vaccine efficacy.

Epitope Mapping of BmpA and BBK32 Borrelia burgdorferi Sensu Stricto Antigens for the Design of Chimeric Proteins with Potential Diagnostic Value

Lyme disease is a tick-borne zoonosis caused by Gram-negative bacteria belonging to the Borrelia burgdorferi sensu lato (s.l.) group. In this study, IgM- and IgG-specific linear epitopes of two B. burgdorferi sensu stricto (s.s.) antigens BmpA and BBK32 were mapped using a polypeptide array. Subsequently, two chimeric proteins BmpA-BBK32-M and BmpA-BBK32-G were designed to validate the construction of chimeras using the identified epitopes for the detection of IgM and IgG, respectively, by ELISA. IgG-ELISA based on the BmpA-BBK32-G antigen showed 71% sensitivity and 95% specificity, whereas a slightly lower diagnostic utility was obtained for IgM-ELISA based on BmpA-BBK32-M, where the sensitivity was also 71% but the specificity decreased to 89%. The reactivity of chimeric proteins with nondedicated antibodies was much lower. These results suggest that the identified epitopes may be useful in the design of new forms of antigens to increase the effectiveness of Lyme disease serodiagnosis. It has also been proven that appropriate selection of epitopes enables the construction of chimeric proteins exhibiting reactivity with a specific antibody isotype.

The yin and yang of B cells in a constant state of battle: intestinal inflammation and inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, defined by a clinical relapse-remitting course. Affecting people worldwide, the origin of IBD is still undefined, arising as a consequence of the interaction between genes, environment, and microbiota. Although the root cause is difficult to identify, data clearly indicate that dysbiosis and pathogenic microbial taxa are connected with the establishment and clinical course of IBD. The composition of the microbiota is shaped by plasma cell IgA secretion and binding, while cytokines such as IL10 or IFN-γ are important fine-tuners of the immune response in the gastrointestinal environment. B cells may also influence the course of inflammation by promoting either an anti-inflammatory or a pro-inflammatory milieu. Here, we discuss IgA-producing B regulatory cells as an anti-inflammatory factor in intestinal inflammation. Moreover, we specify the context of IgA and IgG as players that can potentially participate in mucosal inflammation. Finally, we discuss the role of B cells in mouse infection models where IL10, IgA, or IgG contribute to the outcome of the infection.

The combination of circulating IgM and geriatric nutritional risk index predicts the prognostic of hepatocellular carcinoma patients who underwent immune checkpoint inhibitors

OBJECTIVE

Immune checkpoint inhibitors (ICIs) have shown promise in hepatocellular carcinoma (HCC) treatment. With the increasing use of ICIs in cancer treatment, identifying biomarkers that can predict the prognosis of patients receiving ICIs is of great importance. We aimed to investigate the potential of circulating immunoglobulins and the combination of Geriatric Nutritional Risk Index (GNRI) with IgM to predict prognosis in patients with HCC who received ICIs.

METHODS

Clinical and pathological data were collected from 101 patients with HCC who were administered ICIs and underwent circulating immunoglobulin testing between January 2018 and December 2021. Survival analysis, Cox regression analysis, and nomogram construction were performed to evaluate the prognostic value of the indicators.

RESULTS

In the preliminary survival analysis, we observed a significant correlation between patient prognosis and IgM levels. Patients with low IgM had shorter survival times. Upon combining the GNRI with IgM, patients with low GNRI and IgM levels had shorter progression-free survival (PFS) and overall survival (OS) (P < 0.001). Additionally, GNRI-IgM had the highest area under the curve (AUC) and was identified as an independent prognostic marker in this study. The C-indices of the nomograms for PFS and OS were 0.797 (0.734-0.860) and 0.827 (0.778-0.876), respectively.

CONCLUSIONS

IgM was significantly associated with the prognosis of patients with HCC receiving ICIs. The combination of the GNRI with IgM provided superior prognostic value and served as an independent prognostic marker. The GNRI-IgM can be used to effectively identify patients with HCC who are responsive to ICIs.

Reticulocytes in donor blood units enhance red blood cell alloimmunization

Although red blood cell (RBC) transfusions save lives, some patients develop clinically-significant alloantibodies against donor blood group antigens, which then have adverse effects in multiple clinical settings. Few effective measures exist to prevent RBC alloimmunization and/or eliminate alloantibodies in sensitized patients. Donor-related factors may influence alloimmunization; thus, there is an unmet clinical need to identify which RBC units are immunogenic. Repeat volunteer blood donors and donors on iron supplements have elevated reticulocyte counts compared to healthy non-donors. Early reticulocytes retain mitochondria and other components, which may act as danger signals in immune responses. Herein, we tested whether reticulocytes in donor RBC units could enhance RBC alloimmunization. Using a murine model, we demonstrate that transfusing donor RBC units with increased reticulocyte frequencies dose-dependently increased RBC alloimmunization rates and alloantibody levels. Transfusing reticulocyte-rich RBC units was associated with increased RBC clearance from the circulation and a robust proinflammatory cytokine response. As compared to previously reported post-transfusion RBC consumption patterns, erythrophagocytosis from reticulocyte-rich units was increasingly performed by splenic B cells. These data suggest that reticulocytes in a donated RBC unit impact the quality of blood transfused, are targeted to a distinct compartment, and may be an underappreciated risk factor for RBC alloimmunization.

The Effects of Zinc Supplementation on Growth, Diarrhea, Antioxidant Capacity, and Immune Function in Holstein Dairy Calves

The current study examined the effects of supplementary zinc proteinate (ZnPro) and zinc oxide (ZnO) on growth performance, diarrhea, antioxidant capacity, immune function, and mineral element concentrations of calves aged 1 to 28 days. A total of twenty-four newborn calves were divided randomly into 3 groups (n = 8; 2 males and 6 females per group), and each received: 0 mg/d Zn (CON), 627 mg/d ZnPro (80 mg/d Zn; ZnPro group), and 101 mg/d ZnO (80 mg/d Zn; ZnO group). The calves received the additive in their milk during the first 28 days of life. Compared with the CON group: ZnPro and ZnO improved average daily gain (ADG) and decreased the feed:gain ratio (FGR) between days 1 and 14 (p < 0.05), while the ADG increased and FGR decreased only in the ZnPro group between days 1 and 28 (p < 0.05). The incidence of diarrhea decreased (p < 0.05) in the ZnPro and ZnO groups between days 15 and 28 as well as days 1 and 28, but decreased (p < 0.05) only in the ZnPro group between days 1 and 14. The serum immunoglobulin G (IgG) concentration of the ZnPro and ZnO groups increased on days 14 and 28 (p < 0.05). ZnPro supplementation increased serum IgM concentration during the whole study, while ZnO enhanced serum IgM concentration only on day 14 (p < 0.05). In the ZnO group, the serum concentration of cytokines interleukin (IL)-10 increased on day 14, while that of IL-1β increased on day 28 (p < 0.05). In addition, ZnPro reduced the serum malondialdehyde (MDA) concentration on days 14 and 28 (p < 0.05). Both ZnPro and ZnO increased the serum concentrations of alkaline phosphatase (ALP) and metallothionein (MT) on day 14 (p < 0.05). With zinc supplementation, plasma Zn concentration increased (p < 0.05) on days 14 and 28 of age. We concluded that supplementary ZnPro and ZnO reduced incidences of diarrhea and promoted the immune function, but ZnPro improved the growth performance and antioxidant capacity of Holstein dairy calves to a greater extent.

Commutability evaluation of candidate reference materials and ERM-DA470k/IFCC for immunoglobulin M using two international approaches

BACKGROUND

This study aimed to assess the commutability of frozen pooled human serum (PHS), high concentration of Immunoglobulin M (IgM) pure diluted materials (HPDM), commercialized pure materials (CPM), and dilutions of ERM-DA470k/IFCC in IgM detection using the CLSI and IFCC approaches, to support standardization or harmonization of IgM measurement.

METHODS

Twenty-four serum samples, relevant reference materials (PHS, HPDM, CPM), and different ERM-DA470k/IFCC dilutions were analyzed in triplicate using six routine methods. The commutability of the relevant reference materials was carried out following CLSI EP30-A and IFCC bias analysis.

RESULTS

According to the CLSI approach, low, medium, and high concentrations of PHS, HPDM, and CPM were commutable on 10, 13, 15, 13, and 8 of 15 assay combinations, respectively. Using the IFCC approach, low, medium, and high concentrations of PHS, HPDM, and CPM were commutable on 10, 11, 9, 15, and 10 of 15 assay combinations, respectively. The ERM-DA470k/IFCC dilutions with D-PBS and RPMI-1640 Medium were commutable on 13 of 15 assay combinations according to CLSI and were commutable on all 15 assay combinations using IFCC approach.

CONCLUSIONS

High concentration of PHS were commutable on all six detection systems using the CLSI approach. Low and medium concentration of PHS showed unsatisfied commutability. HPDM, not CPM have good commutability, has the potential to become reference materials. ERM-DA470k/IFCC diluted with different medium showed different commutability.

GP2017-HCF, a high concentration formulation, demonstrates similar pharmacokinetics, immunogenicity and safety to GP2017, an approved adalimumab biosimilar

BACKGROUND

GP2017 is an adalimumab biosimilar. The objective of this study is to compare the pharmacokinetics (PK) of GP2017 in its approved formulation and GP2017-high concentration formulation (HCF) in a randomized, double-blind, two-arm PK bridging study.

RESEARCH DESIGN AND METHODS

Healthy male subjects received a single 40 mg subcutaneous injection of either GP2017-HCF (n = 162) or GP2017 (n = 168). PK, safety, and immunogenicity were assessed over 72 days post-injection.

RESULTS

The 90% confidence intervals [CIs] of geometric mean ratios between GP2017-HCF and GP2017 for Cmax, AUC0-inf, AUC0-360 and AUC0-last were within the pre-defined margin of 0.80 to 1.25; thus, PK comparability between GP2017-HCF and GP2017 was demonstrated. Subgroup analysis of PK comparability by anti-drug antibody (ADA) subpopulation showed that the 90% CIs of geometric mean ratios between GP2017-HCF and GP2017 for Cmax, AUC0-inf, AUC0-360 and AUC0-last were within the margin of 0.80 to 1.25 in ADA-positive and ADA-negative subjects. The proportions of subjects with positive ADA responses and with neutralizing antibodies were comparable between the GP2017-HCF and GP2017 groups. GP2017-HCF and GP2017 were well tolerated, and there were no reports of deaths or other serious adverse events.

CONCLUSION

Results show PK comparability between GP2017-HCF and GP2017 and comparable safety and tolerability.

Sub-chronic exposure of Oreochromis niloticus to environmentally relevant concentrations of smaller microplastics: Accumulation and toxico-physiological responses

This study assesses the accumulation and toxic effects of environmentally relevant concentrations (0.01, 0.1 and 1 mg/L) of polystyrene MPs (1 µm) in Oreochromis niloticus (Nile tilapia) for 14 days. The results showed that 1 µm PS-MPs accumulated in the intestine, gills, liver, spleen, muscle, gonad and brain. RBC, Hb and HCT showed a significant decline, while WBC and PLT showed a significant increase after the exposure. Glucose, total protein, A/G ratio, SGOT, SGPT and ALP showed significant increments in 0.1 and 1 mg/L of PS-MPs treated groups. The increase in cortisol level and upregulation of HSP70 gene expression in response to MPs exposure indicate MPs-mediated stress in tilapia. MPs-induced oxidative stress is evident from reduced SOD activity, increased MDA levels and upregulated P53 gene expression. The immune response was enhanced by inducing respiratory burst activity, MPO activity and serum TNF-α and IgM levels. MPs exposure also led to down-regulation of CYP1A gene and decreased AChE activity, GNRH and vitellogenin levels, indicating the toxicity of MPs on the cellular detoxification mechanism, nervous and reproductive systems. The present study highlights the tissue accumulation of PS-MP and its effects on hematological, biochemical, immunological and physiological responses in tilapia with low environmentally relevant concentrations.

Immunoglobulin M perception by FcμR

Immunoglobulin M (IgM) is the first antibody to emerge during embryonic development and the humoral immune response¹. IgM can exist in several distinct forms, including monomeric, membrane-bound IgM within the B cell receptor (BCR) complex, pentameric and hexameric IgM in serum and secretory IgM on the mucosal surface. FcμR, the only IgM-specific receptor in mammals, recognizes different forms of IgM to regulate diverse immune responses^2-5. However, the underlying molecular mechanisms remain unknown. Here we delineate the structural basis of the FcμR-IgM interaction by crystallography and cryo-electron microscopy. We show that two FcμR molecules interact with a Fcμ-Cμ4 dimer, suggesting that FcμR can bind to membrane-bound IgM with a 2:1 stoichiometry. Further analyses reveal that FcμR-binding sites are accessible in the context of IgM BCR. By contrast, pentameric IgM can recruit four FcμR molecules to bind on the same side and thereby facilitate the formation of an FcμR oligomer. One of these FcμR molecules occupies the binding site of the secretory component. Nevertheless, four FcμR molecules bind to the other side of secretory component-containing secretory IgM, consistent with the function of FcμR in the retrotransport of secretory IgM. These results reveal intricate mechanisms of IgM perception by FcμR.

Lymphocyte subset is more suitable than systemic inflammatory response biomarker and immunoglobulin in constructing prognostic nomogram model for advanced gastric cancer

The serum factors of inflammation are known to be useful prognostic indicators of gastric cancer (GC). However, few studies have made comparisons to screen out more suitable biomarkers for the construction of Nomogram models. In this study, 566 patients who underwent radical gastrectomy were randomly selected. We evaluated the prognostic value of markers of systemic inflammation, including WBC, NLR, PLR, circulating total T cells, CD4⁺T cells, CD8⁺T cells and CD19⁺B cells, serum IgA, IgM, IgE and IgG, and compared them with traditional tumor markers (CEA, CA19-9, CA72-4 and CA125). Kaplan‒Meier analysis was used to analyze the correlation between biomarkers and overall survival (OS). We used time-dependent ROC analysis to investigate the prognostic accuracy of each biomarker. The risk of death was evaluated by the Cox regression model, and the Nomogram model was constructed by R software. We found that circulating total T cells, CD8⁺T cells, CEA, and CA125 had statistical significance in predicting advanced GC prognosis. Circulating CD8⁺T cells and CA125 were continuously superior to circulating total T cells and CEA in the prediction of 5-year OS. Cox regression found that CA125, circulating CD8⁺T cells, sex, and lymph node metastasis rate were independent risk factors for advanced GC. Furthermore, we combined all these predictors to construct a nomogram, which can supplement the AJCC 8th system. According to the comparison with commonly used serum immune biomarkers, circulating CD8⁺T cells is more sensitive to advanced GC. The prediction function of the Nomogram will supplement the traditional AJCC system, which contributes to individual survival prediction.

The Integrated Consideration of Vaccine Platforms, Adjuvants, and Delivery Routes for Successful Vaccine Development

Vaccines have proven to be the most cost-efficient and reasonable way to fight and exterminate virulent pathogens. Vaccines can be designed using a variety of platforms including inactivated/attenuated pathogen or subunits of it. The most recent COVID mRNA vaccines have employed nucleic acid sequences for the antigen of interest to combat the pandemic. Different vaccine platforms have been chosen for different licensed vaccines which all have shown their ability to induce durable immune responses and protection. In addition to platforms, different adjuvants have been used to strengthen the immunogenicity of vaccines. Among the delivery routes, intramuscular injection has been the most common for vaccination. In this review, we present a historical overview of the integrated consideration of vaccine platforms, adjuvants, and delivery routes in the success of vaccine development. We also discuss the advantages and limitations of each choice in the efficacy of vaccine development.

Physiological and Pathophysiological Roles of IgM Fc Receptor (FcµR) Isoforms

IgM is the first antibody to emerge during phylogeny, ontogeny, and immune responses and serves as a first line of defense. Effector proteins interacting with the Fc portion of IgM, such as complement and its receptors, have been extensively studied for their functions. IgM Fc receptor (FcµR), identified in 2009, is the newest member of the FcR family and is intriguingly expressed by lymphocytes only, suggesting the existence of distinct functions as compared to the FcRs for switched Ig isotypes, which are expressed by various immune and non-hematopoietic cells as central mediators of antibody-triggered responses by coupling the adaptive and innate immune responses. Results from FcµR-deficient mice suggest a regulatory function of FcµR in B cell tolerance, as evidenced by their propensity to produce autoantibodies of both IgM and IgG isotypes. In this article, we discuss conflicting views about the cellular distribution and potential functions of FcµR. The signaling function of the Ig-tail tyrosine-like motif in the FcµR cytoplasmic domain is now formally shown by substitutional experiments with the IgG2 B cell receptor. The potential adaptor protein associating with FcµR and the potential cleavage of its C-terminal cytoplasmic tail after IgM binding are still enigmatic. Critical amino acid residues in the Ig-like domain of FcµR for interacting with the IgM Cµ4 domain and the mode of interaction are now defined by crystallographic and cryo-electron microscopic analyses. Some discrepancies on these interactions are discussed. Finally, elevated levels of a soluble FcµR isoform in serum samples are described as the consequence of persistent B cell receptor stimulation, as seen in chronic lymphocytic leukemia and probably in antibody-mediated autoimmune disorders.

Reticulocytes in donor RBC units enhance RBC alloimmunization

Although red blood cell (RBC) transfusions save lives, some patients develop clinically-significant alloantibodies against donor blood group antigens, which then have adverse effects in multiple clinical settings. Few effective measures exist to prevent RBC alloimmunization and/or eliminate alloantibodies in sensitized patients. Donor-related factors may influence alloimmunization; thus, there is an unmet clinical need to identify which RBC units are immunogenic. Repeat volunteer blood donors and donors on iron supplements have elevated reticulocyte counts compared to healthy non-donors. Early reticulocytes retain mitochondria and other components, which may act as danger signals in immune responses. Herein, we tested whether reticulocytes in donor RBC units could enhance RBC alloimmunization. Using a murine model, we demonstrate that transfusing donor RBC units with increased reticulocyte frequencies dose-dependently increase RBC alloimmunization rates and alloantibody levels. Transfusing reticulocyte-rich RBC units was associated with increased RBC clearance from the circulation and a robust proinflammatory cytokine response. As compared to previously reported post-transfusion RBC consumption patterns, erythrophagocytosis from reticulocyte-rich units was increasingly performed by splenic B cells. These data suggest that reticulocytes in a donated RBC unit impact the quality of blood transfused, are targeted to a distinct compartment, and may be an underappreciated risk factor for RBC alloimmunization.

Systematic literature review of immunoglobulin trends for anti-CD20 monoclonal antibodies in multiple sclerosis

OBJECTIVE

To exp lore changes in immunoglobulin (Ig) levels for people with relapsing-multiple sclerosis (RMS) treated with ocrelizumab or ofatumumab and the relationship between Ig levels and infections.

METHODS

A systematic literature review (SLR) was conducted to identify clinical trials and real-world evidence (RWE) studies on Ig levels over time and studies on associations with infections for ocrelizumab and ofatumumab for people with RMS through 10 September 2021. Searches were conducted in Embase, MEDLINE, Cochrane Library, trial registries, and recent conference abstracts.

RESULTS

Of 1,580 articles identified, 30 reporting on 11 trials and 5 RWE studies were included. Ocrelizumab trials (n = 4) had 24-336 weeks of follow-up and reported decreasing Ig G (IgG) levels, while RWE (n = 5) had 52-78 weeks of follow-up and reported IgG to be stable or decrease only slightly. IgG levels were stable in ofatumumab trials (n = 5; 104-168 weeks of follow-up), but no RWE or longer-term studies were identified. No apparent association between decreased Ig levels and infections was observed during ofatumumab treatment (ASCLEPIOS I/II), while for ocrelizumab, the only data on apparent associations between decreased IgG levels and serious infection rates were for a pooled population of people with RMS or primary progressive MS.

CONCLUSION

Decreasing IgG levels have been correlated with increased infection risk over time. IgG levels appeared to decrease over time in ocrelizumab trials but remained relatively stable over time in ofatumumab trials. Additional research is needed to understand differences between ocrelizumab and ofatumumab and identify people at risk of decreasing IgG levels and infection.

Decreased natural killer T-like cells correlated to disease activity in systemic lupus erythematosus

OBJECTIVES

To evaluate the absolute numbers and frequencies of natural killer T-like (NKT-like) cells in systemic lupus erythematosus (SLE) and to characterize the possible role of the cells.

METHODS

Seventy-nine patients with SLE together with 30 age- and sex-matched healthy controls were enrolled. Flow cytometric determination of peripheral NKT-like cells was carried out for all participants by detecting the absolute counts (Abs) and percentage (%) of CD3 + CD16 + CD56 + cells. Disease activity index, laboratory parameters, and clinical manifestations were collected. The correlation between the cells and these parameters was analyzed.

RESULTS

SLE patients had, with respect to controls, considerably decreased values of NKT-like cells (P < 0.001 in both absolute number and percentage). The absolute number of NKT-like cells was found to have positive correlations with WBC, RBC, PLT, C3, C4, IgM and negative correlations with the disease duration, SLEDAI-2 K, anti-dsDNA, anti-nucleosome, anti-ribosomal protein, CRP, ESR. Meanwhile, it was found that the percentage values of NKT-like cells decreased in SLE patients with nephritis which was correlated with anti-ribosomal protein and CRP in comparison to SLE patients without nephritis. Moreover, an increase in the NKT-like cell counts was also observed in the patients with a clinical response to the treatment.

CONCLUSIONS

The absolute counts and frequencies of NKT-like cells decreased in SLE patients significantly, which correlated to disease activities and could recover to normal after the treatment. The NKT-like cells may play an important role in the pathogenesis of SLE and could be a useful marker in the disease assessment. Key Points • The absolute counts and frequencies of NKT-like cells decreased in SLE patients significantly. • NKT-like cells were related to the disease activities and could restore after the treatment. • NKT-like cells may be a useful marker in the disease assessment.

Convalescent human IgG, but not IgM, from COVID-19 survivors confers dose-dependent protection against SARS-CoV-2 replication and disease in hamsters

Introduction

Antibody therapeutic strategies have served an important role during the COVID-19 pandemic, even as their effectiveness has waned with the emergence of escape variants. Here we sought to determine the concentration of convalescent immunoglobulin required to protect against disease from SARS-CoV-2 in a Syrian golden hamster model.

Methods

Total IgG and IgM were isolated from plasma of SARS-CoV-2 convalescent donors. Dose titrations of IgG and IgM were infused into hamsters 1 day prior to challenge with SARS-CoV-2 Wuhan-1.

Results

The IgM preparation was found to have ~25-fold greater neutralization potency than IgG. IgG infusion protected hamsters from disease in a dose-dependent manner, with detectable serum neutralizing titers correlating with protection. Despite a higher in vitro neutralizing potency, IgM failed to protect against disease when transferred into hamsters.

Discussion

This study adds to the growing body of literature that demonstrates neutralizing IgG antibodies are important for protection from SARS-CoV-2 disease, and confirms that polyclonal IgG in sera can be an effective preventative strategy if the neutralizing titers are sufficiently high. In the context of new variants, against which existing vaccines or monoclonal antibodies have reduced efficacy, sera from individuals who have recovered from infection with the emerging variant may potentially remain an efficacious tool.

Functional Characterization of Largemouth Bass (Micropterus salmoides) Soluble FcγR Homolog in Response to Bacterial Infection

Fc receptors (FcRs) are key players in antibody-dependent cellular phagocytosis (ADCP) with their specific recognition of the Fc portion of an immunoglobulin. Despite reports of FcγR-mediated phagocytosis in mammals, little is known about the effects of soluble FcγRs on the immune response. In this study, FcγRIα was cloned from the largemouth bass (Micropterus salmoides) (MsFcγRIα). Without a transmembrane segment or a cytoplasmic tail, MsFcγRIα was identified as a soluble form protein and widely distributed in the spleen, head kidney, and intestine. The native MsFcγRIα was detected in the serum of Nocardia seriolae-infected largemouth bass and the supernatants of transfected HEK293 cells. Additionally, it was verified that the transfected cells' surface secreted MsFcRIα could bind to largemouth bass IgM. Moreover, the expression changes of MsFcγRIα, Syk, and Lyn indicated that MsFcγRIα was engaged in the acute phase response to bacteria, and the FcγR-mediated phagocytosis pathway was activated by Nocardia seriolae stimulation. Furthermore, recombinant MsFcγRIα could enhance both reactive oxygen species (ROS) and phagocytosis to Nocardia seriolae of leukocytes, presumably through the interaction of MsFcγRIα with a complement receptor. In conclusion, these findings provided a better understanding of the function of soluble FcγRs in the immune response and further shed light on the mechanism of phagocytosis in teleosts.

Supplementation of Paraformic Acid as a Substitute for Antibiotics in the Diet Improves Growth Performance and Liver Health in Broiler Chickens

The current study aimed to explore the effects of supplementing paraformic acid (PFA) into broilers’ diet on growth performance, inflammatory responses, and liver protection. A total of 567 healthy one-day-old broilers were used in a 42-d study, and they were randomized into three groups. Broilers were fed a basal diet (CON group) or the basal diet supplemented with either 50 mg/kg aureomycin (AB group) or 1000 mg/kg PFA (PFA group). The results showed that the PFA and AB groups had a higher feed conversion rate than the CON group from day 21 to 42 (p < 0.05). Dietary PFA or aureomycin supplementation decreased serum levels of interleukin (IL)-1β, IL-6, IL-10, alanine transaminase, diamine oxidase, and D-lactate, and significantly increased serum concentrations of immunoglobulin (Ig) A, IgM, and complement C4 (p < 0.05). Moreover, dietary PFA or aureomycin supplementation decreased hepatic levels of caspase-1, NOD-like receptor family pyrin domain containing 3 (NLRP3), tumor necrosis factor-alpha, IL-6, and IL-18, as well as NF-κB mRNA expression (p < 0.05). Above all, PFA supplementation into the broilers’ diet improved growth performance, inhibited inflammatory responses, and benefited liver protection. The protective effects of PFA on the liver might be related to inhibition of caspase-1-induced pyroptosis via inactivating the NF-κB/NLRP3 inflammasome axis in broiler chickens.

Differential immunological effects of silica nanoparticles on peripheral blood mononuclear cells of silicosis patients and controls

Silicosis is a fibrotic disease caused by the inhalation of respirable silica particles, which are typically engulfed by alveolar macrophages and subsequently induce the release of inflammatory cytokines. Various animal experimental and human studies have focused on modeling silicosis, to assess the interactions of macrophages and other cell types with silica particles. There is still, however, limited knowledge on the differential response upon silica-exposure between silicosis patients and controls. We focused on studying the responsiveness of peripheral blood mononuclear cells (PBMCs) to silica nanoparticles (SiNPs) - Ludox and NM-200 - of silicosis patients and controls. The proliferative capacity of T- CD3⁺ and B- CD19⁺ cells, were evaluated via Carboxyfluorescein succinimidyl ester (CFSE) assay. The activation status of lymphocyte subsets and response to silica were also evaluated by comparing the extent of micro-granuloma or aggregate formation with the cytokine secretion profiles between both groups of individuals. The proliferative capacity of CD19⁺ cells was elevated in silicotic patients as opposed to controls. Subsets of regulatory T cells (CD4⁺ CD25⁺ and CD8⁺ CD25⁺) and immunoglobulins IgM and IgG were also significantly increased in patients. The number and the size of aggregates formed were higher with SiNPs stimulation in patients compared to controls. Multivariable analysis also elucidated the role of key cytokines like interleukin-1β (IL-1β), IL-6 and interferon-gamma (IFN-γ), which were upregulated in SiNP-stimulated PBMCs of patients compared to controls. Our ex vivo model thus has potential to provide insights into the immunological effects of silica particles in lymphocytes of silicosis patients and controls.

Growth Performance and Hematological Changes in Growing Sika Deers Fed with Spent Mushroom Substrate of Pleurotus ostreatus

Simple Summary

With the rapid development of the mushroom industry, a large number of spent mushroom substrate (SMS) has also been produced. SMS can be easily digested by ruminants and is suitable for feeding animals, such as cows, sheep, as well as deer. The results of this study show that the dietary spent mushroom substrate of Pleurotus ostreatus (SMS-MP) has no obvious effect on the physiological condition of growing sika deer, at the same time it can reduce the cost of feeding and avoid environmental pollution caused by improper disposal of SMS-MP.

Abstract

The purpose of this experiment is to expand the feed of growing sika deer and to explore the effects on growing sika deer of the spent mushroom substrate of Pleurotus ostreatus (SMS-MP). Twelve immature female growing sika deer were randomly assigned to four groups. The ratios of SMS-MP to replace concentration supplements were 0%, 10%, 20%, and 30%, respectively, and the growth performance, feed intake and apparent digestibility, serum biochemical indexes, blood physiological indexes, serum immune globulin and plasma amino acid of growing sika deer were measured. The results of the current study confirmed the applicability of SMS-MP as a feed ingredient in growing sika deer diets. There was no significant change in growth performance and hematology of growing sika deer when the concentrate supplement was replaced with 10–20% SMS-MP. However, replacing 30% of concentrate supplements with SMS-MP in the growing sika deer diet resulted in significantly decreased Hb and HCT levels. It can be concluded that, as a waste resource, adding a small amount of SMS-MP has no significant effect on the growth of sika deer, and at the same time can reduce the consumption of concentrate supplements, thereby improving the economic benefits of sika deer breeding.

WT1 epitope‑specific IgG and IgM antibodies for immune‑monitoring in patients with advanced sarcoma treated with a WT1 peptide cancer vaccine

The Wilms' tumor gene WT1 is highly expressed in various malignancies and may be a common target antigen for cancer immunotherapy. In our group, peptide-based cancer vaccines targeting WT1 CTL epitopes were developed as an immunotherapy for these malignancies. In the present study, WT1 epitope-specific immune responses were analyzed in 31 patients with advanced sarcoma with human leukocyte antigen-A*24:02- and WT1-expressing tumors who received the WT1-235 peptide vaccine as monotherapy. The serum levels of IgG and IgM antibodies against the target epitope WT1-235 and the non-target epitopes WT1-332 and WT1-271 were measured using ELISA. IgM antibodies against WT1-235, WT1-332 and WT1-271 were detected in three (9.6%), four (12.9%) and 20 patients (64.5%), respectively, prior to vaccine administration, indicating immune recognition of the WT1 antigen prior to administering the vaccine. Of 15 patients who had completed the 3-month treatment protocol, WT1-235 IgG was positive in five (33.3%) patients. An enzyme-linked immunospot assay revealed that WT1-235 epitope-specific IL-10 production/secretion in peripheral blood mononuclear cells declined in the first month of vaccine administration in all three patients with positivity for WT1-235 IgM at the start of the vaccine. Furthermore, positivity for both WT1-235 and WT1-271 IgM antibodies at the start of treatment was associated with unfavorable tumor control at 3 months after vaccine administration. These results suggested that WT1 epitope-specific IgG and IgM antibodies may be utilized as immune-monitoring markers for WT1 peptide cancer vaccine immunotherapy. The trials were entered in the University hospital Medical Information Network (UMIN) Clinical Trials Registry (https://www.umin.ac.jp/ctr; no. UMIN000002001 on May 24, 2009 and no. UMIN000015997 on December 20, 2014).

Comparison of Gut Microbiota and Metabolic Status of Sows With Different Litter Sizes During Pregnancy

The experiment was conducted to compare the differences of gut microbiota and metabolic status of sows with different litter sizes on days 30 and 110 of gestation, and uncover the relationship between the composition of maternal gut microbiota during gestation and sow reproductive performance. Twenty-six Large White × Landrace crossbred multiparous sows (2nd parity) with similar back fat thickness and body weight were assigned to two groups [high-reproductive performance group (HP group) and low-reproductive performance group (LP group)] according to their litter sizes and fed a common gestation diet. Results showed that compared with LP sows, HP sows had significantly lower plasma levels of triglyceride (TG) on gestation d 30 (P < 0.05), but had significantly higher plasma levels of TG, non-esterified fatty acid, tumor necrosis factor-α, and immunoglobulin M on gestation d 110 (P < 0.05). Consistently, HP sows revealed increased alpha diversity and butyrate-producing genera, as well as fecal butyrate concentration, on gestation d 30; HP sows showed significantly different microbiota community structure with LP sows (P < 0.05) and had markedly higher abundance of Firmicutes (genera Christensenellaceae_R-7_group and Terrisporobacter) which were positively related with litter size on gestation d 110 than LP sows (P < 0.05). In addition, plasma biochemical parameters, plasma cytokines, and fecal microbiota shifted dramatically from gestation d 30 to d 110. Therefore, our findings demonstrated that microbial abundances and community structures differed significantly between sows with different litter sizes and gestation stages, which was associated with changes in plasma biochemical parameters, inflammatory factors, and immunoglobulin. Moreover, these findings revealed that there was a significant correlation between litter size and gut microbiota of sows, and provided a microbial perspective to improve sow reproductive performance in pig production.

Molecular docking and dynamic simulation of conserved B cell epitope of SARS-CoV-2 glycoprotein Indonesian isolates: an immunoinformatic approach

Background: An immunoinformatic approach may be useful to investigate the conserved region in the spike glycoprotein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Indonesia isolates. The aim of this study was to investigate Indonesian SARS-CoV-2 isolates based on B cell epitopes by targeting the conserved regions in the spike glycoprotein to trigger increased multi-variant virus neutralization and memory response for the development of vaccine seed candidates. Methods: SARS-CoV-2 spike glycoprotein gene sequences originating from Indonesia were compared with Wuhan (China), the United Kingdom, South Africa, India, the United States, and Brazil isolates obtained from the NCBI and GISAID databases. The recognition of antigens was carried out directly using B cells through the B cell receptor (BCR). An indirect B cell activation by Cluster of Differentiation (CD)4+ T cells and major histocompatibility complex (MHC)-II was predicted through the binding with human leukocyte antigen (HLA) based on IC ₅₀ value. In addition, vaccine allergenicity and toxicity were investigated. During the molecular complex examination, the 3D peptide structure was investigated and the lowest amount of energy formed when the vaccine candidate peptide bound to BCR and MHC-II was calculated. Results: As a result, the spike glycoprotein sequences of Indonesian SARS-CoV-2 isolates had conserved regions which were very similar to reference countries such as China, the United Kingdom, South Africa, India, the United States, and Brazil. Conclusion: It was predicted that the conserved regions could be identified as the epitope of B and T CD4+ cells that produced the peptides for vaccine candidate with antigenic, non-allergen, and non-toxic properties.

Overview of Neutralizing Antibodies and Their Potential in COVID-19

The antibody response to respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a major focus of COVID-19 research due to its clinical relevance and importance in vaccine and therapeutic development. Neutralizing antibody (NAb) evaluations are useful for the determination of individual or herd immunity against SARS-CoV-2, vaccine efficacy, and humoral protective response longevity, as well as supporting donor selection criteria for convalescent plasma therapy. In the current manuscript, we review the essential concepts of NAbs, examining their concept, mechanisms of action, production, and the techniques used for their detection; as well as presenting an overview of the clinical use of antibodies in COVID-19.

Francisella and Antibodies

Immune responses to intracellular pathogens depend largely upon the activation of T helper type 1-dependent mechanisms. The contribution of B cells to establishing protective immunity has long been underestimated. Francisella tularensis, including a number of subspecies, provides a suitable model for the study of immune responses against intracellular bacterial pathogens. We previously demonstrated that Francisella infects B cells and activates B-cell subtypes to produce a number of cytokines and express the activation markers. Recently, we documented the early production of natural antibodies as a consequence of Francisella infection in mice. Here, we summarize current knowledge on the innate and acquired humoral immune responses initiated by Francisella infection and their relationships with the immune defense systems.

Development of a new peptide-bead coupling method for an all peptide-based Luminex multiplexing assay for detection of Plasmodium falciparum antibody responses

Using a recombinant protein antigen for antibody testing shows a sum of antibody responses to multiple different immune epitopes existing in the protein antigen. In contrast, the antibody testing to an immunogenic peptide epitope reflects a singular antibody response to the individual peptide epitope. Therefore, using a panel of peptide epitopes provides an advantage for profiling multiple singular antibody responses with potential to estimate recent malaria exposure in human infections. However, transitioning from malaria immune epitope peptide-based ELISA to an all peptide bead-based multiplex Luminex assay presents some challenges including variation in the ability of different peptides to bind beads. The aim of this study was to develop a peptide coupling method while demonstrating the utility of these peptide epitopes from multiple stage antigens of Plasmodium falciparum for measuring antibodies. Successful coupling of peptide epitopes to beads followed three steps: 1) development of a peptide tag appended to the C-terminus of each peptide epitope consisting of beta-alanine-lysine (x 4)--cysteine, 2) bead modification with a high concentration of adipic acid dihydrazide, and 3) use of the peptide epitope as a blocker in place of the traditional choice, bovine serum albumin (BSA). This new method was used to couple 12 peptide epitopes from multiple stage specific antigens of P. falciparum, 1 Anopheles mosquito salivary gland peptide, and 1 Epstein-Barr virus peptide as an assay control. The new method was applied to testing of IgG in pooled samples from 30 individuals with previously repeated malaria exposure in western Kenya and IgM and IgG in samples from 37 U.S. travelers with recent exposure to malaria. The new peptide-bead coupling method and subsequent multiplex Luminex assay showed reliable detection of IgG to all 14 peptides in Kenyan samples. Among 37 samples from U.S. travelers recently diagnosed with malaria, IgM and IgG to the peptide epitopes were detected with high sensitivity and variation. Overall, the U.S. travelers had a much lower positivity rates of IgM than IgG to different peptide epitopes, ranging from a high of 62.2% positive for one epitope to a low of only 5.4% positive for another epitope. In contrast, the travelers had IgG positive rates from 97.3% to 91.9% to various peptide epitopes. Based on the different distribution in IgM and IgG positivity to overall number of peptide epitopes and to the number of pre-erythrocytic, erythrocytic, gametocytic, and salivary stage epitopes at the individual level, four distinct patterns of IgM and IgG responses among the 37 samples from US travelers were observed. Independent peptide-bead coupling and antibody level readout between two different instruments also showed comparable results. Overall, this new coupling method resolves the peptide-bead coupling challenge, is reproducible, and can be applied to any other immunogenic peptide epitopes. The resulting all peptide bead-based multiplex Luminex assay can be expanded to include other peptide epitopes of P. falciparum, different malaria species, or other diseases for surveillance, either in US travelers or endemic areas.

Exploring the Mechanism of Indigo Naturalis in the Treatment of Ulcerative Colitis Based on TLR4/MyD88/NF-κB Signaling Pathway and Gut Microbiota

Background: Clinical trials have proven that indigo naturalis is a candidate drug for treating ulcerative colitis (UC), but its therapeutic mechanism is still unclear.

Purpose: This study aimed to evaluate the protective effect and mechanism of indigo naturalis to treat mice with dextran sulfate sodium (DSS)-induced UC.

Methods: DSS-induced UC mice were treated with indigo naturalis (200 mg/kg), indigo (4.76 mg/kg), and indirubin (0.78 mg/kg) for 1 week. The anti-UC mechanism of indigo naturalis was studied by pathological section, inflammatory factor, western blot, and 16S rRNA sequencing.

Results: According to body weight change, disease activity index, and colon length, indigo naturalis had the strongest anti DSS-induced UC effect, followed by indirubin and indigo. Pathological section showed that indigo naturalis, indigo, and indirubin could reduce the infiltration of inflammatory cells, increase the secretion of intestinal mucus, and repair the intestinal mucosa. Indigo naturalis, indigo, and indirubin could reduce IL-1β,IL-6, and TNF-α by inhibiting TLR4/MyD88/NF-κB signal transduction. Indigo naturalis and indigo could also reduce IgA and IgG both in serum and colon tissue. In addition, indigo naturalis, indigo, and indirubin could adjust the gut microbiota structure of DSS-induced UC mice, reducing the ratio of Firmicutes/Bacteroidetes and increasing the abundance of probiotics.

Conclusion: Indigo and indirubin are one of the main anti-UC components of indigo naturalis. INN could regulate intestinal flora, reduce inflammation, repair intestinal mucosa, and improve the physiological status of DSS-induced UC mice and its anti-UC mechanism may be involved in inhibiting TLR4/MyD88/NF-κB signal transduction.

Differences between Human and Mouse IgM Fc Receptor (FcµR)

Both non-immune "natural" and antigen-induced "immune" IgM are important for protection against pathogens and for regulation of immune responses to self-antigens. Since the bona fide IgM Fc receptor (FcµR) was identified in humans by a functional cloning strategy in 2009, the roles of FcµR in these IgM effector functions have begun to be explored. In this short essay, we describe the differences between human and mouse FcµRs in terms of their identification processes, cellular distributions and ligand binding activities with emphasis on our recent findings from the mutational analysis of human FcµR. We have identified at least three sites of human FcµR, i.e., Asn66 in the CDR2, Lys79 to Arg83 in the DE loop and Asn109 in the CDR3, responsible for its constitutive IgM-ligand binding. Results of computational structural modeling analysis are consistent with these mutational data and a model of the ligand binding, Ig-like domain of human FcµR is proposed. Serendipitously, substitution of Glu41 and Met42 in the CDR1 of human FcµR with mouse equivalents Gln and Leu, either single or more prominently in combination, enhances both the receptor expression and IgM binding. These findings would help in the future development of preventive and therapeutic interventions targeting FcµR.

Is SARS-CoV-2 Neutralized More Effectively by IgM and IgA than IgG Having the Same Fab Region?

Recently, recombinant monoclonal antibodies (mAbs) of three Ig isotypes (IgG, IgA, and IgM) sharing the same anti-spike protein Fab region were developed; we evaluated their neutralizing abilities using a pseudo-typed lentivirus coated with the SARS-CoV-2 spike protein and ACE2-transfected Crandell–Rees feline kidney cells as the host cell line. Although each of the anti-SARS-CoV-2 mAbs was able to neutralize the spike-coated lentiviruses, IgM and IgA neutralized the viral particles at 225-fold and 125-fold lower concentrations, respectively, than that of IgG. Our finding that the neutralization ability of Igs with the same Fab domain was dramatically higher for IgM and IgA than IgG mAbs suggests a strategy for developing effective and affordable antibody therapies for COVID-19. The efficient neutralization conferred by IgM and IgA mAbs can be explained by their capacity to bind multiple virions. While several IgG mAbs have been approved as therapeutics by the FDA, there are currently no IgM or IgA mAbs available. We suggest that mAbs with multiple antigen-binding sites such as IgM and IgA could be developed as the new generation of therapy.

Self-Adjuvant Effect by Manipulating the Bionano Interface of Liposome-Based Nanovaccines

Nanovaccines are of increasing scrutiny due to their plasticity in size, composition, and surface properties to enhance antigenicity. However, inevitable absorption of plasma proteins affects the in vivo fate of nanovaccines by reshaping biological identity. Herein IgM was validated as a self-adjuvant by regulating antigen-presenting cells recognition of liposome-based nanovaccines. ^DCDX-modified liposomes with loading of ovalbumin (^DCDX-sLip/OVA) heavily absorbed IgM via electrostatic interaction, demonstrating significant splenic B cells targeting. IgM absorbed on ^DCDX-sLip/OVA enhanced antigen uptake and presentation by both IgM-complement and IgM-FcμR pathways. ^DCDX-sLip/OVA induced a stronger IgG1 titer than ovalbumin-loaded plain liposomes (sLip/OVA) while maintaining a comparably high level of IgG2a titer with high biosafety, indicating that IgM absorption after ^DCDX modification could improve the antigenicity by enhancing the Th2-polarized immune response. The present work suggested manipulation of IgM absorption may provide a new impetus to improve in vivo performance of nanovaccines.

Role of Polymeric Immunoglobulin Receptor in IgA and IgM Transcytosis

Transcytosis of polymeric IgA and IgM from the basolateral surface to the apical side of the epithelium and subsequent secretion into mucosal fluids are mediated by the polymeric immunoglobulin receptor (pIgR). Secreted IgA and IgM have vital roles in mucosal immunity in response to pathogenic infections. Binding and recognition of polymeric IgA and IgM by pIgR require the joining chain (J chain), a small protein essential in the formation and stabilization of polymeric Ig structures. Recent studies have identified marginal zone B and B1 cell-specific protein (MZB1) as a novel regulator of polymeric IgA and IgM formation. MZB1 might facilitate IgA and IgM transcytosis by promoting the binding of J chain to Ig. In this review, we discuss the roles of pIgR in transcytosis of IgA and IgM, the roles of J chain in the formation of polymeric IgA and IgM and recognition by pIgR, and focus particularly on recent progress in understanding the roles of MZB1, a molecular chaperone protein.

Structure of the human secretory immunoglobulin M core

Immunoglobulins (Ig) A and M are the only human antibodies that form oligomers and undergo transcytosis to mucosal secretions via the polymeric Ig receptor (pIgR). When complexed with the J-chain (JC) and the secretory component (SC) of pIgR, secretory IgA and IgM (sIgA and sIgM) play critical roles in host-pathogen defense. Recently, we determined the structure of sIgA-Fc which elucidated the mechanism of polymeric IgA assembly and revealed an extensive binding interface between IgA-Fc, JC, and SC. Despite low sequence identity shared with IgA-Fc, IgM-Fc also undergoes JC-mediated assembly and binds pIgR. Here, we report the structure of sIgM-Fc and carryout a systematic comparison to sIgA-Fc. Our structural analysis reveals a remarkably conserved mechanism of JC-templated oligomerization and SC recognition of both IgM and IgA through a highly conserved network of interactions. These studies reveal the structurally conserved features of sIgM and sIgA required for function in mucosal immunity.

Identification of Amino Acid Residues in Human IgM Fc Receptor (FcµR) Critical for IgM Binding

Both non-immune “natural” and antigen-induced “immune” IgM are important for protection against infections and for regulation of immune responses to self-antigens. The roles of its Fc receptor (FcµR) in these IgM effector functions have begun to be explored. In the present study, by taking advantage of the difference in IgM-ligand binding of FcµRs of human (constitutive binding) and mouse (transient binding), we replaced non-conserved amino acid residues of human FcµR with mouse equivalents before establishment of cell lines stably expressing mutant or wild-type (WT) receptors. The resultant eight-different mutant FcµR-bearing cells were compared with WT receptor-bearing cells for cell-surface expression and IgM-binding by flow cytometric assessments using receptor-specific mAbs and IgM paraproteins as ligands. Three sites Asn66, Lys79-Arg83, and Asn109, which are likely in the CDR2, DE loop and CDR3 of the human FcµR Ig-like domain, respectively, were responsible for constitutive IgM binding. Intriguingly, substitution of Glu41 and Met42 in the presumed CDR1 with the corresponding mouse residues Gln and Leu, either single or more prominently in combination, enhanced both the receptor expression and IgM binding. A four-aa stretch of Lys24-Gly27 in the predicted A ß-strand of human FcµR appeared to be essential for maintenance of its proper receptor conformation on plasma membranes because of reduction of both receptor expression and IgM-binding potential when these were mutated. Results from a computational structural modeling analysis were consistent with these mutational data and identified a possible mode of binding of FcµR with IgM involving the loops including Asn66, Arg83 and Asn109 of FcµR interacting principally with the Cµ4 domain including Gln510 and to a lesser extent Cµ3 domain including Glu398, of human IgM. To our knowledge, this is the first experimental report describing the identification of amino acid residues of human FcµR critical for binding to IgM Fc.

Characteristics of Immunoglobulin M Type Antibodies of Different Origins from the Immunologic and Clinical Viewpoints and Their Application in Controlling Antibody-Mediated Allograft Rejection

Antibody-mediated allograft rejection (AMR) hinders patient prognosis after organ transplantation. Current studies concerning AMR have mainly focused on the diagnostic value of immunoglobulin G (IgG)-type donor-specific antihuman leukocyte antigen antibodies (DSAs), primarily because of their antigen specificity, whereas the clinical significance of immunoglobulin M (IgM)-type DSAs has not been thoroughly investigated in the context of organ transplantation because of their nonspecificity against antigens. Although consensus regarding the clinical significance and role of IgM antibodies is not clear, as discussed in this review, recent findings strongly suggest that they also have a huge potential in novel diagnostic as well as therapeutic application for the prevention of AMR. Most serum IgM antibodies are known to comprise natural antibodies with low affinity toward antigens, and this is derived from B-1 cells (innate B cells). However, some of the serum IgM-type antibodies reportedly also produced by B-2 cells (conventional B cells). The latter are known to have a high affinity for donor-specific antigens. In this review, we initially discuss how IgM-type antibodies of different origins participate in the pathology of various diseases, directly or through cell surface receptors, complement activation, or cytokine production. Then, we discuss the clinical applicability of B-1 and B-2 cell-derived IgM-type antibodies for controlling AMR with reference to the involvement of IgM antibodies in various pathological conditions.

Testing IgG antibodies against the RBD of SARS-CoV-2 is sufficient and necessary for COVID-19 diagnosis

The COVID-19 pandemic and the fast global spread of the disease resulted in unprecedented decline in world trade and travel. A critical priority is, therefore, to quickly develop serological diagnostic capacity and identify individuals with past exposure to SARS-CoV-2. In this study serum samples obtained from 309 persons infected by SARS-CoV-2 and 324 of healthy, uninfected individuals as well as serum from 7 COVID-19 patients with 4-7 samples each ranging between 1-92 days post first positive PCR were tested by an "in house" ELISA which detects IgM, IgA and IgG antibodies against the receptor binding domain (RBD) of SARS-CoV-2. Sensitivity of 47%, 80% and 88% and specificity of 100%, 98% and 98% in detection of IgM, IgA and IgG antibodies, respectively, were observed. IgG antibody levels against the RBD were demonstrated to be up regulated between 1-7 days after COVID-19 detection, earlier than both IgM and IgA antibodies. Study of the antibody kinetics of seven COVID 19 patients revealed that while IgG levels are high and maintained for at least 3 months, IgM and IgA levels decline after a 35-50 days following infection. Altogether, these results highlight the usefulness of the RBD based ELISA, which is both easy and cheap to prepare, to identify COVID-19 patients even at the acute phase. Most importantly our results demonstrate that measuring IgG levels alone is both sufficient and necessary to diagnose past exposure to SARS-CoV-2.

Considerations of Antibody Geometric Constraints on NK Cell Antibody Dependent Cellular Cytotoxicity

It has been well-established that antibody isotype, glycosylation, and epitope all play roles in the process of antibody dependent cellular cytotoxicity (ADCC). For natural killer (NK) cells, these phenotypes are linked to cellular activation through interaction with the IgG receptor FcγRIIIa, a single pass transmembrane receptor that participates in cytoplasmic signaling complexes. Therefore, it has been hypothesized that there may be underlying spatial and geometric principles that guide proper assembly of an activation complex within the NK cell immune synapse. Further, synergy of antibody phenotypic properties as well as allosteric changes upon antigen binding may also play an as-of-yet unknown role in ADCC. Understanding these facets, however, remains hampered by difficulties associated with studying immune synapse dynamics using classical approaches. In this review, I will discuss relevant NK cell biology related to ADCC, including the structural biology of Fc gamma receptors, and how the dynamics of the NK cell immune synapse are being studied using innovative microscopy techniques. I will provide examples from the literature demonstrating the effects of spatial and geometric constraints on the T cell receptor complex and how this relates to intracellular signaling and the molecular nature of lymphocyte activation complexes, including those of NK cells. Finally, I will examine how the integration of high-throughput and "omics" technologies will influence basic NK cell biology research moving forward. Overall, the goal of this review is to lay a basis for understanding the development of drugs and therapeutic antibodies aimed at augmenting appropriate NK cell ADCC activity in patients being treated for a wide range of illnesses.

Low FCMR mRNA expression in leukocytes of patients with Kawasaki disease six months after disease onset

BACKGROUND

Immunoglobulin (Ig) M plays an important role in immune regulation. FCMR-encoded FcμR is a receptor of IgM. Previous research has suggested that IgM levels may be involved in the coronary artery lesions of Kawasaki syndrome or Kawasaki disease (KD). In this study, we aimed to explore the roles of mRNA expressions of IgM receptors, particularly FCMR, in KD patients. FCMR encodes the Fc fragment of immunoglobulin M receptor.

METHODS

We enrolled 60 KD patients and 55 non-KD controls. Whole-blood leukocytes were isolated, and the mRNA expression for FCMR was determined. Each mRNA consisted of a sample taken before intravenous immunoglobulin (IVIG) was administered (acute, KD1) and those taken at three weeks, six months, and one year later (KD3, KD4, KD5). Paired KD subjects were analyzed from both the acute and convalescent phases (n = 28).

RESULTS

After six months and one year of treatment, KD patients still apparently have lower FCMR compared with controls (P = .004). FCMR expressions were downregulated in male patients with KD prior to IVIG administration (P = .044). The FCMR of paired KD patients who received IVIG treatments after six months was significantly lower than before undergoing IVIG treatment (P = .044). Expressions in the polymorphonuclear leukocytes were similar to those in the peripheral blood mononuclear cells.

CONCLUSION

The unique data supported that FCMR is expressed by granulocytes at RNA levels in humans and demonstrated lower FCMR six months after the onset of KD. The findings remind us of the need to track the health of children with KD over the long term, even if we think patients have fully recovered.