Enhanced potency of an IgM-like nanobody targeting conserved epitope in SARS-CoV-2 spike N-terminal domain

Almost all the neutralizing antibodies targeting the receptor-binding domain (RBD) of spike (S) protein show weakened or lost efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged or emerging variants, such as Omicron and its sub-variants. This suggests that highly conserved epitopes are crucial for the development of neutralizing antibodies. Here, we present one nanobody, N235, displaying broad neutralization against the SARS-CoV-2 prototype and multiple variants, including the newly emerged Omicron and its sub-variants. Cryo-electron microscopy demonstrates N235 binds a novel, conserved, cryptic epitope in the N-terminal domain (NTD) of the S protein, which interferes with the RBD in the neighboring S protein. The neutralization mechanism interpreted via flow cytometry and Western blot shows that N235 appears to induce the S1 subunit shedding from the trimeric S complex. Furthermore, a nano-IgM construct (MN235), engineered by fusing N235 with the human IgM Fc region, displays prevention via inducing S1 shedding and cross-linking virus particles. Compared to N235, MN235 exhibits varied enhancement in neutralization against pseudotyped and authentic viruses in vitro. The intranasal administration of MN235 in low doses can effectively prevent the infection of Omicron sub-variant BA.1 and XBB in vivo, suggesting that it can be developed as a promising prophylactic antibody to cope with the ongoing and future infection.

MicroRNA and long non-coding RNA analysis in IgM-monoclonal gammopathies reveals epigenetic influence on cellular functions and oncogenesis

Not available.

Hepatitis E virus infections among patients with acute febrile jaundice in two regions of Cameroon: First molecular characterization of hepatitis E virus genotype 4

BACKGROUND

Febrile jaundice is a common indicator of certain infectious diseases, including hepatitis E. In Cameroon, the yellow fever virus is the only pathogen that is monitored in patients who present with this symptom. However, more than 90% of the samples received as part of this surveillance are negative for yellow fever. This study aimed to describe the prevalence and hepatitis E virus (HEV) genotype among yellow fever-negative patients in the Far North and West regions of Cameroon.

METHODS

In a cross-sectional study, yellow fever surveillance-negative samples collected between January 2021 and January 2023 were retrospectively analyzed. Anti-HEV IgM and IgG antibodies were tested using commercially available ELISA kits. Anti-HEV IgM and/or IgG positive samples were tested for HEV RNA by real-time RT-PCR, followed by nested RT-PCR, sequencing and phylogenetic analysis.

RESULTS

Overall, 121 of the 543 samples (22.3%, 95% CI: 19.0% - 26.0%) were positive for at least one anti-HEV marker. Amongst these, 8.1% (44/543) were positive for anti-HEV IgM, 5.9% (32/543) for anti-HEV IgG, and 8.3% (45/544) for both markers. A total of 15.2% (12/79) samples were positive for HEV RNA real-time RT-PCR and 8 samples were positive for HEV RNA by nested RT-PCR. Phylogenetic analysis showed that the retrieved sequences clustered within HEV genotypes/subtypes 1/1e, 3/3f and 4/4b.

CONCLUSION

Our results showed that HEV is one of the causes of acute febrile jaundice in patients enrolled in the yellow fever surveillance program in two regions of Cameroon. We described the circulation of three HEV genotypes, including two zoonotic genotypes. Further studies will be important to elucidate the transmission routes of these zoonotic HEV genotypes to humans in Cameroon.

[Preparation of HSV-IgM human-mouse chimeric antibody and development of stable recombinant cell line]

In order to achieve large-scale production of HSV-IgM (HSV1, HSV2) human-mouse chimeric antibody in vitro, the gene sequence of the corresponding hybridoma cell was harvested by RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE) technique to clone the chimeric antibody into eukaryotic expression vectors, and express the target proteins in CHO-S cells. At the same time, the screening process of stable cell lines was optimized, and the pressure conditions of pool construction stage and monoclonal screening stage were explored. Finally, the target protein was purified by protein L affinity purification method and the biological activity was detected. The recombinant IgM antibodies, HSV1 and HSV2, weighted at 899 kDa and 909 kDa respectively, were prepared. The optimal screening pressure was 20P200M (the first phase of pressure) and 50P1000M (the second phase of pressure). The final titer for the monoclonal expression of HSV1-IgM and HSV2-IgM was 1 620 mg/L and 623 mg/L, respectively. This study may facilitate the development of quality control products of HSV1 and HSV2 IgM series recombinant antibodies as well as efficient expression of IgM subtype antibodies in vitro.

Colistin resistance mutations in phoQ can sensitize Klebsiella pneumoniae to IgM-mediated complement killing

Due to multi-drug resistance, physicians increasingly use the last-resort antibiotic colistin to treat infections with the Gram-negative bacterium Klebsiella pneumoniae. Unfortunately, K. pneumoniae can also develop colistin resistance. Interestingly, colistin resistance has dual effects on bacterial clearance by the immune system. While it increases resistance to antimicrobial peptides, colistin resistance has been reported to sensitize certain bacteria for killing by human serum. Here we investigate the mechanisms underlying this increased serum sensitivity, focusing on human complement which kills Gram-negatives via membrane attack complex (MAC) pores. Using in vitro evolved colistin resistant strains and a fluorescent MAC-mediated permeabilization assay, we showed that two of the three tested colistin resistant strains, Kp209_CSTR and Kp257_CSTR, were sensitized to MAC. Transcriptomic and mechanistic analyses focusing on Kp209_CSTR revealed that a mutation in the phoQ gene locked PhoQ in an active state, making Kp209_CSTR colistin resistant and MAC sensitive. Detailed immunological assays showed that complement activation on Kp209_CSTR in human serum required specific IgM antibodies that bound Kp209_CSTR but did not recognize the wild-type strain. Together, our results show that developing colistin resistance affected recognition of Kp209_CSTR and its killing by the immune system.

Enhanced Mott cell formation linked with IgM Fc receptor (FcμR) deficiency

In previous studies, Mott cells, an unusual form of plasma cells containing Ig-inclusion bodies, were frequently observed in peripheral lymphoid tissues in our IgM Fc receptor (FcμR)-deficient (KO) mouse strain. Because of discrepancies in the reported phenotypes of different Fcmr KO mouse strains, we here examined two additional available mutant strains and confirmed that such enhanced Mott-cell formation was a general phenomenon associated with FcμR deficiency. Splenic B cells from Fcmr KO mice clearly generated more Mott cells than those from WT mice when stimulated in vitro with LPS alone or a B-1, but not B-2, activation cocktail. Nucleotide sequence analysis of the Ig variable regions of a single IgMλ+ Mott-hybridoma clone developed from splenic B-1 B cells of Fcmr KO mice revealed the near (VH) or complete (Vλ) identity with the corresponding germline gene segments and the addition of six or five nucleotides at the VH/DH and DH/JH junctions, respectively. Transduction of an FcμR cDNA into the Mott hybridoma significantly reduced cells containing IgM-inclusion bodies with a concomitant increase in IgM secretion, leading to secreted IgM binding to FcμR expressed on Mott transductants. These findings suggest a regulatory role of FcμR in the formation of Mott cells and IgM-inclusion bodies.

Characterization of T-cell receptors and immunoglobulin heavy chains loci and identification of T/B cell clusters in teleost

Bacterial disease is one of the important factors leading to economic losses in the turbot (Scophthalmus maximus) cultivation industry. T lymphocytes are major components of cellular immunity, whereas B lymphocytes produce immunoglobulins (Ig) that are key elements of humoral immune responses against infection. However, the genomic organization of genes encoding T-cell receptors (TCR) and immunoglobulin heavy chains (IgHs) in turbot remains largely unknown. In this study, abundant full-length transcripts of TCRs and IgHs were sequenced by Isoform-sequencing (Iso-seq), and we investigated and annotated the V, D, J and C gene loci of TCRα, TCRβ, IgT, IgM and IgD in turbot. Furthermore, through single-cell RNA sequencing (scRNA-seq) of blood leukocytes, we confirmed that these identified TCRs and IgHs were highly expressed in T/B cell clusters, respectively. Meanwhile, we also identified the IgM⁺IgD⁺ B and IgT⁺ B cells with differential gene expression profiles and potential functions. Taken together, our results provide a comprehensive understanding of TCRs and IgHs loci in turbot, which will contribute to evolutionary and functional characterization of T and B lymphocytes in teleost.

Molecular and functional characterization of two IgM subclasses in large yellow croaker (Larimichthys crocea)

As the predominant immunoglobulin (Ig) isotype, IgM plays a crucial role in the acquired immunity of vertebrates. There is only one Igμ gene in mammals, except cattle, while the number of Igμ gene varies among teleost fish. In the current study, we found two functional Igμ genes (Igμ1 and Igμ2) and a pseudo Cμ gene (ψIgμ) in large yellow croaker (Larimichthys crocea). Both Igμ1 and Igμ2 genes possessed two transcript variants, which encoded the heavy chains of secreted (sIgM1 and sIgM2) and membrane-bound IgM1 and IgM2 (mIgM1 and mIgM2), respectively. Both the heavy chains of sIgM1 and sIgM2 consisted of a variable Ig domain, four constant Ig domains (CH1, CH2, CH3 and CH4) and a secretory tail, while those of mIgM1 and mIgM2 consisted of a variable Ig domain, three constant Ig domains (CH1, CH2 and CH3), a transmembrane domain and a short cytoplasmic tail. Cysteine residues that are necessary for the formation of intrachain and interchain disulfide bonds and tryptophan residues that are important for the folding of the Ig superfamily domain were well conserved in large yellow croaker IgM1 and IgM2. Interestingly, large yellow croaker IgM2 had an extra cysteine (C94) in the CH1 domain compared with IgM1, which may cause the structural difference between IgM1 and IgM2. A liquid chromatography-tandem mass spectrometry analysis revealed that both IgM1 and IgM2 were present at the protein level in large yellow croaker serum. Both the Igμ1 and Igμ2 genes were mainly expressed in systemic immune tissues, such as head kidney and spleen, but the expression level of Igμ2 was much lower than that of Igμ1. After Pseudomonas plecoglossicida infection, the expression levels of Igμ1 and Igμ2 in both the spleen and head kidney were significantly upregulated, with a higher upregulation of Igμ2 than that of Igμ1. These results suggested that Igμ1 and Igμ2 may play a differential role in the immune response of large yellow croaker against bacterial infection.

Molecular characterization and expression analysis of immunoglobulins (IgM and IgT) heavy chains in black rockfish (Sebastes schlegelii) that response to bacterial challenge

Sebastes schlegelii is a kind of fish with great economic values. Recently, with the continuous expansion of aquaculture scale and the continuous improvement of aquaculture density, outbreak of various diseases has caused huge economic losses to its aquaculture industry. Study of fish immune system can help to understand the mechanism of immune response to external pathogens and can promote the development of immune prevention and control methods. Immunoglobulins (Igs) are complex glycoproteins that appear to be unique to the vertebrates that can recognize a wide variety of pathogens and recruit immune cells and molecules to destroy pathogens, which are generated by a series of rearrangement and somatic mutations. We therefore studied the immunoglobulin genes of S. schlegelii in view of their important roles in resisting to external pathogen infections. In this study, the immunoglobulin heavy chain genes (sIgM, mIgM, sIgT, and mIgT) of S. schlegelii were successfully identified and cloned. Phylogenetic analysis showed that the IgM and IgT genes of S. schlegelii were clustered together with homologous genes of other species, indicating that they were highly conserved during the evolutionary process. Collinearity analysis showed that the immunoglobulin genes and their adjacent genes were aligned with zebrafish, Atlantic salmon and tilapia, which further confirmed the conserved immunoglobulin gene of teleost. Expression analysis of healthy tissues showed that the expression levels of sIgM, sIgT and mIgT were the highest in the skin, while mIgM was the highest in spleen. After different bacterial infection, IgM and IgT were significantly expressed in skin and gill, which may be because skin and gill are the first line of defense against the infection pathogens. Subcellular localization showed that the mIgT protein was expressed in both the cell membrane and cytoplasm. Meanwhile, recombinant protein of mIgT was obtained in vitro, which laid a foundation for subsequent protein function studies. These results provide a theoretical basis for understanding the immunity role of immunoglobulin in S. schlegelii.

[A Case of Bing-Neel Syndrome With Repeated Long Spinal Cord Lesions]

The patient was a 45-year-old man. Since 2019, he had exhibited repeated steroid-improved dysuria and long spinal cord lesions. At the time of recurrence in June 2020, he exhibited a marked increase in serum IgM levels, suggesting hematopoietic disease. We found an MYD88 L265P mutation in cerebrospinal fluid cells, which subsequently led to the diagnosis of Bing-Neel syndrome (BNS). The patient was treated with Burton's tyrosine kinase inhibitors and his condition progressed without dysuria or worsening of the imaging findings. This case was challenging to differentiate from intractable inflammatory diseases; however, the identification of hyper-IgM helped in the diagnosis. BNS should be differentiated from central nervous system lesions through the identification of hyper-IgM.

Molecular cloning and characteristic analysis of polymeric immunoglobulin receptor-like (plgRL) in large yellow croaker (Larimichthys crocea)

In the present study, the polyimmunoglobulin receptor-like (pIgRL) of large yellow croaker (Larimichthys crocea) was first cloned and characterized. LcpIgRL's full-length cDNA was 1610 bp, encoding 377 amino acids, and the protein's predicted molecular weight was 41.9 kDa, containing two immunoglobulin-like structural domains. The transcript levels of LcpIgRL in different tissues of healthy large yellow croaker were examined by real-time fluorescence quantitative PCR, and the results showed that the gills and head kidney had the highest levels. Within 36 h of the large yellow croaker being infected with Vibrio harveyi, pIgRL mRNA first increased and then decreased in all determined tissues, with the highest expression in the skin and hindgut. Furthermore, a recombinant protein of the extracellular region of LcpIgRL was expressed in E. coli BL21, and a murine rLcpIgRL polyclonal antibody was prepared, which could react specifically with the natural LcpIgRL in skin mucus, but no natural LcpIgRL was detected in serum. Meanwhile, it was found that the rLcpIgRL could bind to the recombinant IgM and the natural IgM, indicating that LcpIgRL could mediate the transport of IgM in mucus. In addition, rLcpIgRL binds to Aeromonas hydrophila and V. harveyi, as well as lipopolysaccharide (LPS) and various saccharides, and reduced binding to bacteria was observed under LPS treatment, suggesting that LcpIgRL can bind to bacteria to prevent infection and that saccharide binding is an important mechanism of interaction between pIgRL and bacteria.

Immune function modulation during artificial ovarian maturation in Japanese eel (Anguilla japonica): A transcriptome profiling approach

The Japanese eel (Anguilla japonica) experiences dramatic internal and external environmental changes during its transoceanic reproductive migrations. Here, we assess immune function changes in the primary and secondary immune organs (head kidney and spleen) of A. japonica during artificial ovarian maturation at the previtellogenic (PV), midvitellogenic (MV), and ovulating (OV) stages by transcriptome analyses. Stress responses were also assessed by determining the serum concentrations of lysozyme, alkaline phosphatase, acid phosphatase, total antioxidant capacity, and superoxide dismutase. Our results showed that together with increased serum 17β-estrogen and testosterone, lysozyme activity and antioxidant capacity were suppressed during artificial ovarian maturation. Comparisons across these developmental stages identified 60 (head kidney) and 36 (spleen) differentially expressed genes associated with the immune system. Genes related to the key activation markers of innate immune function, such as CXCL10, CXCL11, CCL20, HSP90B, MMP9, and MMP13, were upregulated and significantly enriched in the interleukin-17 signaling pathway. Adaptive immune function-related genes (IGM and MHC1) were upregulated in the head kidney from PV to MV, and their levels increased thereafter in the spleen. Moreover, a correlation between Pax5 expression and IGM expression in the spleen of MV (IGM+/Pax5+) and OV (IGM++/Pax5-) stage suggests that adaptive immune function was enhanced during ovarian maturation. To our knowledge, the present study is the first to describe transcriptome profiling of immune organs during ovarian maturation in teleost. Our findings suggest that the interleukin-17 pathway and IgM may play important roles in spawning.

Case Report: Chronic hepatitis E in a hematopoietic stem cell transplant recipient: The first report of hepatitis E virus genotype 4 causing chronic infection in a non-solid organ recipient

Hepatitis E virus (HEV) is one of the most important public health issues around the world, and chronic HEV infection has been reported in immunosuppressed individuals. This study reported a male case, with very severe aplastic anemia (AA), who developed chronic hepatitis E after hematopoietic stem cell transplantation (HSCT). Abnormal alanine aminotransferase (ALT) appeared after HSCT and persisted for twenty-nine months. The case was seropositive for anti-HEV IgG and IgM after HSCT. Twenty-two months after HSCT, HEV RNA and antigen (Ag) testing were positive and persisted for five and seven months, respectively. Positive stains of HEV Ag were present in a liver biopsy sample. HEV Ag was present in bone marrow. The individual rapidly developed liver cirrhosis and was rescued by a regimen of oral ribavirin. These factors suggested there is a risk of HEV infection in HSCT recipients.

Reprogramming of Human B Cells from Secreting IgG to IgM by Genome Editing

B lymphocytes are activated and regulated by their interactions with T cells, a process that results in one-way class switching of immunoglobulins (ig) from IgM to IgG, IgE, or IgA. In this study, we show the application of clustered regularly interspaced short palindromic repeat-Cas9-induced nonhomologous end joining in B cells to achieve reverse-directional Ig class switching. By electroporating Cas9 and guide RNA and a Cμ encoding donor into cells, we engineered IgG-secreting human B cell lines to switch to express IgM antibody. This approach offers a new potential path for the production of IgM antibodies.

Concurrent Waldenstrom’s Macroglobulinemia and Myelodysplastic Syndrome with a Sequent t(10;13)(p13;q22) Translocation

Myelodysplastic syndromes (MDS) and Waldenstrom’s macroglobulinemia (WM) are rarely synchronous. Ineffective myelopoiesis/hematopoiesis with clonal unilineage or multilineage dysplasia and cytopenias characterize MDS. Despite a myeloid origin, MDS can sometimes lead to decreased production, abnormal apoptosis or dysmaturation of B cells, and the development of lymphoma. WM includes bone marrow involvement by lymphoplasmacytic lymphoma (LPL) secreting monoclonal immunoglobulin M (IgM) with somatic mutation (L265P) of myeloid differentiation primary response 88 gene (MYD88) in 80–90%, or various mutations of C-terminal domain of the C-X-C chemokine receptor type 4 (CXCR4) gene in 20–40% of cases. A unique, progressive case of concurrent MDS and WM with several somatic mutations (some unreported before) and a novel balanced reciprocal translocation between chromosomes 10 and 13 is presented below.

Cellular Mechanisms Underlying B Cell Abnormalities in Patients With Gain-of-Function Mutations in the PIK3CD Gene

Background

Activated phosphoinositide 3 kinase (PI3K) -delta syndrome (APDS) is an inborn error of immunity with variable clinical phenotype of immunodeficiency and immune dysregulation and caused by gain-of-function mutations in PIK3CD. The hallmark of immune phenotype is increased proportions of transitional B cells and plasmablasts (PB), progressive B cell loss, and elevated levels of serum IgM.

Objective

To explore unique B cell subsets and the pathomechanisms driving B cell dysregulation beyond the transitional B cell stage in APDS.

Methods

Clinical and immunological data was collected from 24 patients with APDS. In five cases, we performed an in-depth analysis of B cell phenotypes and cultured purified naïve B cells to evaluate their survival, activation, Ig gene class switch recombination (CSR), PB differentiation and antibody secretion. We also analyzed PB differentiation capacity of sorted CD27^-IgD^- double-negative B (DNB) cells.

Results

The patients had increased B cell sizes and higher proportions of IgM⁺ DNB cells than healthy controls (HC). Their naïve B cells exhibited increased death, impaired CSR but relatively normal PB differentiation. Upon stimulation, patient’s DNB cells secreted a similar level of IgG but a higher level of IgM than DNB cells from HC. Targeted therapy of PI3K inhibition partially restored B cell phenotypes.

Conclusions

The present study suggests additional mechanistic insight into B cell pathology of APDS: (1) decreased peripheral B cell numbers may be due to the increased death of naïve B cells; (2) larger B cell sizes and expanded DNB population suggest enhanced activation and differentiation of naïve B cells into DNB cells; (3) the impaired CSR yet normal PB differentiation can predominantly generate IgM-secreting cells, resulting in elevated IgM levels.

Mystifying Molecular Structure, Expression and Repertoire Diversity of IgM Heavy Chain Genes (Ighμ) in Clarias Catfish and Hybrids: Two Novel Transcripts in Vertebrates

Two novel immunoglobulin heavy chain (Ighμ) transcripts encoding membrane-bound forms of IgM (mIgM) were discovered in bighead catfish, Clarias macrocephalus. The first transcript contains four constant and two transmembrane domains [Cμ1-Cμ2-Cμ3-Cμ4-TM1-TM2] that have never been reported in teleosts, and the second transcript is an unusual mIgM that has never been identified in any vertebrate [Cμ1-(Cδ2-Cδ3-Cδ4-Cδ5)-Cμ2-Cμ3-TM1-TM2]. Fluorescence in situ hybridization (FISH) in bighead catfish, North African catfish (C. gariepinus) and hybrid catfish revealed a single copy of Ighμ in individual parent catfish, while two gene copies were found in diploid hybrid catfish. Intensive sequence analysis demonstrated multiple distinct structural variabilities in the VH domain in Clarias, and hybrid catfish were defined and used to generate diversity with various mechanisms. Expression analysis of Ighμ in Aeromonas hydrophila infection of the head kidney, peripheral blood leukocytes and spleen revealed significantly higher levels in North African catfish and hybrid catfish than in bighead catfish.

MYD88 Mutations: Transforming the Landscape of IgM Monoclonal Gammopathies

The MYD88 gene has a physiological role in the innate immune system. Somatic mutations in MYD88, including the most common L265P, have been associated with the development of certain types of lymphoma. MYD88L265P is present in more than 90% of patients with Waldenström's macroglobulinemia (WM) and IgM monoclonal gammopathy of undetermined significance (IgM-MGUS). The absence of MYD88 mutations in WM patients has been associated with a higher risk of transformation into aggressive lymphoma, resistance to certain therapies (BTK inhibitors), and shorter overall survival. The MyD88 signaling pathway has also been used as a target for specific therapies. In this review, we summarize the clinical applications of MYD88 testing in the diagnosis, prognosis, follow-up, and treatment of patients. Although MYD88L265P is not specific to WM, few tumors present a single causative mutation in a recurrent position. The role of the oncogene in the pathogenesis of WM is still unclear, especially considering that the mutation can be found in normal B cells of patients, as recently reported. This may have important implications for early lymphoma detection in healthy elderly individuals and for the treatment response assessment based on a MYD88L265P analysis.

Cross-sectional study of chromosomal aberrations and immunologic factors in Iraqi couples with recurrent pregnancy loss

BACKGROUND

Parental chromosomal aberrations are important causes of recurrent pregnancy loss (RPL). Some immunological factors such as antiphospholipid antibodies and interleukin-6 (IL-6) also contribute to this complication. The aim of this study was to determine the frequency of chromosomal abnormalities and to evaluate some of the immunological factors in couples with RPL from different cities in Iraq.

METHODS

This study was conducted on 25 couples (50 individuals) who had more than two first trimester abortions in the past and 25 healthy females as controls. Karyotyping was performed on peripheral blood of all participants. Anticardiolipin (IgG and IgM), antiphosopholipid (IgG and IgM), lupus anticoagulant, and IL-6 were assayed. Data were analyzed using appropriate statistical tests.

RESULTS

Chromosomal abnormalities were found in 28.0% (n = 7/25) of RPL couples. Of these five (10.0%) were female and two (4.0%) were male. The types of structural abnormalities were as follows: 45, XX, t(21; 21); 45, XX, rob (14, 15); 46, XX, add (21) (p13); 46 XY, add (21)(p13); 46, XX, 21ps+; 46, XY, per inv (9) (p11q12) and 45, XX, t(13q, 13q). No chromosomal abnormalities were found in the control group. Also, no significant differences were found in the immunological parameters of the couples with RPL and the control group.

CONCLUSION

In this study, karyotyping revealed a high number of chromosomal abnormalities associated with the RPL in Iraqi couples. Since identification of genetic causes of miscarriage is important for genetic counseling and educating couples about the risk of future pregnancies, it is recommended that conventional karyotyping be investigated in patients with RPL.

Loss of Id3 (Inhibitor of Differentiation 3) Increases the Number of IgM-Producing B-1b Cells in Ischemic Skeletal Muscle Impairing Blood Flow Recovery During Hindlimb Ischemia

OBJECTIVE

Neovascularization can maintain and even improve tissue perfusion in the setting of limb ischemia during peripheral artery disease. The molecular and cellular mechanisms mediating this process are incompletely understood. We investigate the potential role(s) for Id3 (inhibitor of differentiation 3) in regulating blood flow in a murine model of hindlimb ischemia (HLI). Approach and Results: HLI was modeled through femoral artery ligation and resection and blood flow recovery was quantified by laser Doppler perfusion imaging. Mice with global Id3 deletion had significantly impaired perfusion recovery at 14 and 21 days of HLI. Endothelial- or myeloid cell-specific deletion of Id3 revealed no effect on perfusion recovery while B-cell-specific knockout of Id3 (Id3BKO) revealed a significant attenuation of perfusion recovery. Flow cytometry revealed no differences in ischemia-induced T cells or myeloid cell numbers at 7 days of HLI, yet there was a significant increase in B-1b cells in Id3BKO. Consistent with these findings, ELISA (enzyme-linked immunoassay) demonstrated increases in skeletal muscle and plasma IgM. In vitro experiments demonstrated reduced proliferation and increased cell death when endothelial cells were treated with conditioned media from IgM-producing B-1b cells and tibialis anterior muscles in Id3BKO mice showed reduced density of total CD31+ and αSMA+CD31+ vessels.

CONCLUSIONS

This study is the first to demonstrate a role for B-cell-specific Id3 in maintaining blood flow recovery during HLI. Results suggest a role for Id3 in promoting blood flow during HLI and limiting IgM-expressing B-1b cell expansion. These findings present new mechanisms to investigate in peripheral artery disease pathogenesis.

IgM-MM is predominantly a pre-germinal center disorder and has a distinct genomic and transcriptomic signature from WM

Immunoglobulin M (IgM) multiple myeloma (MM) is a rare disease subgroup. Its differentiation from other IgM-producing gammopathies such as Waldenström macroglobulinemia (WM) has not been well characterized but is essential for proper risk assessment and treatment. In this study, we investigated genomic and transcriptomic characteristics of IgM-MM samples using whole-genome and transcriptome sequencing to identify differentiating characteristics from non-IgM-MM and WM. Our results suggest that IgM-MM shares most of its defining structural variants and gene-expression profiling with MM, but has some key characteristics, including t(11;14) translocation, chromosome 6 and 13 deletion as well as distinct molecular and transcription-factor signatures. Furthermore, IgM-MM translocations were predominantly characterized by VHDHJH recombination-induced breakpoints, as opposed to the usual class-switching region breakpoints; coupled with its lack of class switching, these data favor a pre-germinal center origin. Finally, we found elevated expression of clinically relevant targets, including CD20 and Bruton tyrosine kinase, as well as high BCL2/BCL2L1 ratio in IgM-MM, providing potential for targeted therapeutics.

Efficacy of ulvan on immune response and immuno-antioxidant gene modulation in Labeo rohita against columnaris disease

This study reports the effect of ulvan enriched diet on the influence of growth, changes in hemato-biochemical indices, improvement of antioxidant system, enhancement of innate-adaptive immunity and modification of immuno-antioxidant genes expression in Labeo rohita against Flavobacterium columnaris. The weight gain (WG) was significantly high (P > 0.05) in unchallenged normal and challenged fish fed with diets enriched with 25 and 50 mg kg^-1 ulvan; the FCR was better (P > 0.05) when fed with 50 mg kg^-1 enriched diet. In normal fish fed with or without ulvan supplementation was noted 100% survival rate (SR). In both groups, the red blood cell (RBC) and while blood cell (WBC) counts increased significantly (P > 0.05) when fed with 50 mg kg^-1 ulvan diet whereas the hemoglobin (Hb) level increased significantly on being fed with 25 and 50 mg kg^-1 ulvan diets. The SOD activity was enhanced significantly in both groups fed with any dose of ulvan diets whereas the MDA and GPx activity increased only with 25 and 50 mg kg^-1 ulvan diets. The phagocytic (PC) activity significantly increased with any enriched diet and control diet groups while the respiratory burst (RB) activity increased only with 50 mg kg^-1 ulvan diet. The alternate complement pathway (ACP), activity of lysozyme (Lyz), and immunoglobuline M (IgM) were better in both groups fed with 50 mg kg^-1 ulvan diet. The SOD and GPx antioxidant gene expression were significantly high in both groups fed with any ulvan diet while the Nrf2 gene expression was high with 50 mg kg^-1 ulvan diet. The IL-1β, TNFα, hepcidin, Lyz, and IgM cytokines or proteins mRNA expression were significant in both groups fed with all ulvan supplement diet whereas the β-2M expression was significant only with 50 mg kg^-1 ulvan diet. The present research indicates that both L. rohita groups fed with 50 mg kg^-1 ulvan diet significantly improved growth, antioxidant system, immune defense system, and immuno-antioxidant related gene expression against F. columnaris.

Developmental and comparative immunology single-cell transcriptome analysis of the B-cell repertoire reveals the usage of immunoglobulins in the gray short-tailed opossum (Monodelphis domestica)

B-cells are key to humoral immunity, are found in multiple lymphoid organs, and have the unique ability to mediate the production of antigen-specific antibodies in the presence of pathogens. The marsupial immunoglobulin (Ig) heavy (H) chain locus encodes four constant region isotypes, IgA, IgG, IgM and IgE, but no IgD, and there are two light (L) chain isotypes, lambda (Igλ) and kappa (Igκ). To gain an understanding of the marsupial humoral immune system, B-cell transcriptomes generated by single-cell RNA sequencing from gray short-tailed opossum (Monodelphis domestica) splenocytes, and peripheral blood mononuclear cells were analysed. The cells used were from a single unimmunized animal and the majority of B-cells were transcribing IgM heavy chains. The ratio of Ig light chain use was roughly 2:1, Igλ:Igκ in this individual. This was not predicted due to Igκ being the more complex of the two L chain loci. The variable (V) gene segment pairs used in individual B-cells confirm greater diversity provided by the L chain V. This study is the first to report on using single cell analysis to investigate Ig repertoires in a marsupial and confirms a number of prior hypothesis, as well as revealing some surprises.

Serum Complement Activation by C4BP-IgM Fusion Protein Can Restore Susceptibility to Antibiotics in Neisseria gonorrhoeae

Neisseria gonorrhoeae is the etiological agent of gonorrhea, the second most common bacterial sexually transmitted infection worldwide. Reproductive sequelae of gonorrhea include infertility, ectopic pregnancy and chronic pelvic pain. Most antibiotics currently in clinical use have been rendered ineffective due to the rapid spread of antimicrobial resistance among gonococci. The developmental pipeline of new antibiotics is sparse and novel therapeutic approaches are urgently needed. Previously, we utilized the ability of N. gonorrhoeae to bind the complement inhibitor C4b-binding protein (C4BP) to evade killing by human complement to design a chimeric protein that linked the two N-terminal gonococcal binding domains of C4BP with the Fc domain of IgM. The resulting molecule, C4BP-IgM, enhanced complement-mediated killing of gonococci. Here we show that C4BP-IgM induced membrane perturbation through complement deposition and membrane attack complex pore insertion facilitates the access of antibiotics to their intracellular targets. Consequently, bacteria become more susceptible to killing by antibiotics. Remarkably, C4BP-IgM restored susceptibility to azithromycin of two azithromycin-resistant clinical gonococcal strains because of overexpression of the MtrC-MtrD-MtrE efflux pump. Our data show that complement activation can potentiate activity of antibiotics and suggest a role for C4BP-IgM as an adjuvant for antibiotic treatment of drug-resistant gonorrhea.

Marginal zone B cells mediate a CD4 T-cell-dependent extrafollicular antibody response following RBC transfusion in mice

Red blood cell (RBC) transfusions can result in alloimmunization toward RBC alloantigens that can increase the probability of complications following subsequent transfusion. An improved understanding of the immune mechanisms that underlie RBC alloimmunization is critical if future strategies capable of preventing or even reducing this process are to be realized. Using the HOD (hen egg lysozyme [HEL] and ovalbumin [OVA] fused with the human RBC antigen Duffy) model system, we aimed to identify initiating immune factors that may govern early anti-HOD alloantibody formation. Our findings demonstrate that HOD RBCs continuously localize to the marginal sinus following transfusion, where they colocalize with marginal zone (MZ) B cells. Depletion of MZ B cells inhibited immunoglobulin M (IgM) and IgG anti-HOD antibody formation, whereas CD4 T-cell depletion only prevented IgG anti-HOD antibody development. HOD-specific CD4 T cells displayed similar proliferation and activation following transfusion of HOD RBCs into wild-type or MZ B-cell-deficient recipients, suggesting that IgG formation is not dependent on MZ B-cell-mediated CD4 T-cell activation. Moreover, depletion of follicular B cells failed to substantially impact the anti-HOD antibody response, and no increase in antigen-specific germinal center B cells was detected following HOD RBC transfusion, suggesting that antibody formation is not dependent on the splenic follicle. Despite this, anti-HOD antibodies persisted for several months following HOD RBC transfusion. Overall, these data suggest that MZ B cells can initiate and then contribute to RBC alloantibody formation, highlighting a unique immune pathway that can be engaged following RBC transfusion.

Single-cell immunophenotyping of the skin lesion erythema migrans identifies IgM memory B cells

The skin lesion erythema migrans (EM) is an initial sign of the Ixodes tick-transmitted Borreliella spirochetal infection known as Lyme disease. T cells and innate immune cells have previously been shown to predominate the EM lesion and promote the reaction. Despite the established importance of B cells and antibodies in preventing infection, the role of B cells in the skin immune response to Borreliella is unknown. Here, we used single-cell RNA-Seq in conjunction with B cell receptor (BCR) sequencing to immunophenotype EM lesions and their associated B cells and BCR repertoires. We found that B cells were more abundant in EM in comparison with autologous uninvolved skin; many were clonally expanded and had circulating relatives. EM-associated B cells upregulated the expression of MHC class II genes and exhibited preferential IgM isotype usage. A subset also exhibited low levels of somatic hypermutation despite a gene expression profile consistent with memory B cells. Our study demonstrates that single-cell gene expression with paired BCR sequencing can be used to interrogate the sparse B cell populations in human skin and reveals that B cells in the skin infection site in early Lyme disease expressed a phenotype consistent with local antigen presentation and antibody production.

Class switching and high-affinity immunoglobulin G production by B cells is dispensable for the development of hypertension in mice

AIMS

Elevated serum immunoglobulins have been associated with experimental and human hypertension for decades but whether immunoglobulins and B cells play a causal role in hypertension pathology is unclear. In this study, we sought to determine the role of B cells and high-affinity class-switched immunoglobulins on hypertension and hypertensive end-organ damage to determine if they might represent viable therapeutic targets for this disease.

METHODS AND RESULTS

We purified serum immunoglobulin G (IgG) from mice exposed to vehicle or angiotensin (Ang) II to induce hypertension and adoptively transferred these to wild type (WT) recipient mice receiving a subpressor dose of Ang II. We found that transfer of IgG from hypertensive animals does not affect blood pressure, endothelial function, renal inflammation, albuminuria, or T cell-derived cytokine production compared with transfer of IgG from vehicle infused animals. As an alternative approach to investigate the role of high-affinity, class-switched immunoglobulins, we studied mice with genetic deletion of activation-induced deaminase (Aicda-/-). These mice have elevated levels of IgM but virtual absence of class-switched immunoglobulins such as IgG subclasses and IgA. Neither male nor female Aicda-/- mice were protected from Ang II-induced hypertension and renal/vascular damage. To determine if IgM or non-immunoglobulin-dependent innate functions of B cells play a role in hypertension, we studied mice with severe global B-cell deficiency due to deletion of the membrane exon of the IgM heavy chain (µMT-/-). µMT-/- mice were also not protected from hypertension or end-organ damage induced by Ang II infusion or deoxycorticosterone acetate-salt treatment.

CONCLUSIONS

These results suggest that B cells and serum immunoglobulins do not play a causal role in hypertension pathology.

Complete genome analysis and characterization of neurotropic dengue virus 2 cosmopolitan genotype isolated from the cerebrospinal fluid of encephalitis patients

Dengue virus (DENV) infection remains a major public health concern in many parts of the world, including Southeast Asia and the Americas. Sri Lanka experienced its largest dengue outbreak in 2017. Neurological symptoms associated with DENV infection have increasingly been reported in both children and adults. Here, we characterize DENV type 2 (DENV-2) strains, which were isolated from cerebrospinal fluid (CSF) and/or serum of patients with dengue encephalitis. Acute serum and CSF samples from each patient were subjected to dengue-specific non-structural protein 1 (NS1) antigen test, IgM and IgG enzyme-linked immunosorbent assay (ELISA), virus isolation, conventional and real-time polymerase chain reaction (PCR), and next-generation sequencing (NGS). Among the 5 dengue encephalitis patients examined, 4 recovered and 1 died. DENV-2 strains were isolated from serum and/or CSF samples of 3 patients. The highest viral genome levels were detected in the CSF and serum of the patient who succumbed to the illness. A phylogenetic tree revealed that the DENV-2 isolates belonged to a new clade of cosmopolitan genotype and were genetically close to strains identified in China, South Korea, Singapore, Malaysia, Thailand, and the Philippines. According to the NGS analysis, greater frequencies of nonsynonymous and synonymous mutations per gene were identified in the nonstructural genes. The full genomes of serum- and CSF-derived DENV-2 from the same patient shared 99.7% similarity, indicating that the virus spread across the blood-brain barrier. This is the first report to describe neurotropic DENV-2 using whole-genome analysis and to provide the clinical, immunological, and virological characteristics of dengue encephalitis patients during a severe dengue outbreak in Sri Lanka in 2017.

Transient pentameric IgM fulfill biological function-Effect of expression host and transfection on IgM properties

Recombinant production of IgM antibodies poses a special challenge due to the complex structure of the proteins and their not yet fully elucidated interactions with the immune effector proteins, especially the complement system. In this study, we present transient expression of IgM antibodies (IgM617, IgM012 and IgM012_GL) in HEK cells and compared it to the well-established stable expression system in CHO cells. The presented workflow investigates quality attributes including productivity, polymer distribution, glycosylation, antibody structure and activation of the classical complement pathway. The HEK293E transient expression system is able to generate comparable amounts and polymer distribution as IgM stably produced in CHO. Although the glycan profile generated by HEK293E cells contained a lower degree of sialylation and a higher portion of oligomannose structures, the potency to activate the complement cascade was maintained. Electron microscopy also confirmed the structural integrity of IgM pentamers produced in HEK293E cells, since the conventional star-shaped structure is observed. From our studies, we conclude that the transient expression system provides an attractive alternative for rapid, efficient and high-throughput production of complex IgM antibodies with slightly altered post-translational modifications, but comparable structure and function.

CMTM7 plays key roles in TLR-induced plasma cell differentiation and p38 activation in murine B-1 B cells

Terminal differentiation of B cells into antibody-secreting cells is the foundation of humoral immune response. B-1 cells, which are different from B-2 cells, preferentially differentiate into plasma cells. CMTM7 is a MARVEL-domain-containing membrane protein predominantly expressed in B cells that plays an important role in B-1a cell development. The present study assessed CMTM7 function in response to antigen stimulation. Following immunization with T cell-dependent and T cell-independent antigens, Cmtm7-deficient mice exhibited decreased IgM but normal IgG responses in vivo. In vitro stimulation with LPSs induced Cmtm7^-/- B-1 cell activation, whereas proliferation was marginally reduced. Notably, Cmtm7 deficiency markedly suppressed plasma cell differentiation in response to TLR agonists, accompanied by a decrease in IgM and IL-10 production. At the molecular level, loss of Cmtm7 repressed the downregulation of Pax5 and the upregulation of Xbp1, Irf4, and Prdm1. Furthermore, p38 phosphorylation was inhibited in Cmtm7^-/- B-1 cells. Experiments using a p38 inhibitor revealed that p38 activation was essential for the terminal differentiation of B-1 cells, suggesting that Cmtm7 contributes to B-1 cell differentiation by maintaining p38 activation. Overall, the data reveal the crucial functions of CMTM7 in TLR-induced terminal differentiation and p38 activation in B-1 cells.

Integrative analysis of spontaneous CLL regression highlights genetic and microenvironmental interdependency in CLL

Spontaneous regression is a recognized phenomenon in chronic lymphocytic leukemia (CLL) but its biological basis remains unknown. We undertook a detailed investigation of the biological and clinical features of 20 spontaneous CLL regression cases incorporating phenotypic, functional, transcriptomic, and genomic studies at sequential time points. All spontaneously regressed tumors were IGHV-mutated with no restricted IGHV usage or B-cell receptor (BCR) stereotypy. They exhibited shortened telomeres similar to nonregressing CLL, indicating prior proliferation. They also displayed low Ki-67, CD49d, cell-surface immunoglobulin M (IgM) expression and IgM-signaling response but high CXCR4 expression, indicating low proliferative activity associated with poor migration to proliferation centers, with these features becoming increasingly marked during regression. Spontaneously regressed CLL displayed a transcriptome profile characterized by downregulation of metabolic processes as well as MYC and its downstream targets compared with nonregressing CLL. Moreover, spontaneous regression was associated with reversal of T-cell exhaustion features including reduced programmed cell death 1 expression and increased T-cell proliferation. Interestingly, archetypal CLL genomic aberrations including HIST1H1B and TP53 mutations and del(13q14) were found in some spontaneously regressing tumors, but genetic composition remained stable during regression. Conversely, a single case of CLL relapse following spontaneous regression was associated with increased BCR signaling, CLL proliferation, and clonal evolution. These observations indicate that spontaneously regressing CLL appear to undergo a period of proliferation before entering a more quiescent state, and that a complex interaction between genomic alterations and the microenvironment determines disease course. Together, the findings provide novel insight into the biological processes underpinning spontaneous CLL regression, with implications for CLL treatment.

Comparative transcriptome analysis of the transcriptional heterogeneity in different IgM+ cell subsets from peripheral blood of Nile tilapia (Oreochromis niloticus)

In teleost fish, IgM⁺ B cells play important roles in innate and adaptive immunity. Different IgM⁺ B cells are detected in teleost, named IgM^lo and IgM^hi B cell subsets, according to the distinct expression levels of membrane IgM (mIgM). However, the study on the heterogeneity in IgM⁺ B cell subsets remains poorly understood. In this study, the comparative transcriptomic profiles of IgM^-, IgM^lo and IgM^hi from peripheral blood of Nile tilapia (Oreochromis niloticus) were carried out by using RNA-sequencing technique. A total of 6045 and 5470 differentially expressed genes (DEGs) were detected in IgM^lo and IgM^hi cells, respectively, as compared with IgM^- lymphocytes, whereas 3835 genes were differentially expressed when IgM^lo compared to IgM^hi cells. Analysis of the KEGG database indicated that the DEGs were enriched in immune system categories and signaling transduction and interaction in IgM^- vs IgM^hi, IgM^- vs IgM^lo and IgM^lo vs IgM^hi. Comparatively, in IgM^lo vs IgM^hi, GO enrichment analysis indicated that the DEGs enriched in nucleic acid binding transcription factor activity. Analysis of crucial transcription factors for B cell differentiation indicated that IgM^lo and IgM^hi cell clusters belonged to the different B cell subsets. The data generated in this study may provide insights into understanding the heterogeneity of IgM⁺ cells in teleost, and suggest that IgM⁺ B cells play a crucial role in innate immunity.

Bacillus pumilus SE5 originated PG and LTA tuned the intestinal TLRs/MyD88 signaling and microbiota in grouper (Epinephelus coioides)

The normal microbiota plays a key role in the health of host, but little is known of how the fish immune system recognizes and responds to indigenous bacteria/probiotics. Our previous studies have showed that heat-inactivated indigenous Bacillus pumilus SE5 activate the TLR2 signaling pathways and modulate the intestinal microbiota in grouper (Epinephelus coioides), suggesting microbial-associated molecular patterns (MAMPs) involved. In this study, whole cell wall (CW) and two possible MAMPs, peptidoglycan (PG) and lipoteichoic acid (LTA) have been extracted from B. pumilus SE5 and their effects on intestinal immune related genes expression and microbiota were evaluated in a 60 days feeding trial. Significantly elevated expression of TLR1, TLR2, TLR5 and MyD88 was observed in fish fed the CW, PG and LTA containing diets, and the highest expression was observed in groups PG and LTA. At the same time, significantly upregulated expression of antimicrobial effectors, such as antimicrobial peptides (epinecidin-1, hepcidin-1 and β-defensin), C-type Lectin and IgM was observed in fish fed PG and LTA containing diets. This induced activation of intestinal immunity was consistent with the microbiota data showing that CW, PG and LTA originated from SE5 modulated the overall structure of intestinal microbiota, and the relative abundance of potentially pathogenic Vibrio decreased significantly while beneficial Lactobacillus increased significantly in fish fed PG and LTA. In conclusion, both the PG and LTA originated from B. pumilus SE5 could activate TLRs/MyD88 signaling and expression of wide-ranging antibacterial effectors, and therefore shape the intestinal microbiota in grouper.

Cloning and expressional analysis of secretory and membrane-bound IgM in rock bream (Oplegnathus fasciatus) under megalocytivirus infection and vaccination

In this study, for better understanding the humoral immunity of rock bream (Oplegnathus fasciatus), 2 transcripts of immunoglobulin M (IgM) heavy chain gene including membrane bound (m-IgM) and secretory (s-IgM) forms were sequenced and analyzed their tissue distribution and differential expression in rock bream under rock bream iridovirus (RBIV) infection and vaccination since RBIV has caused mass mortality in rock bream aquaculture in Korea. Consequently, s-IgM cDNA was 1902 bp in length encoding a leader region, a variable region, four constant regions (CH1, CH2, CH3, CH4) and a C-terminal region while m-IgM cDNA was 1689 bp in length encoding shorter three constant regions (CH1, CH2, CH3) and two transmembrane regions. The predicted s-IgM and m-IgM represent a high structural similarity to other species including human. In tissue distribution analysis in healthy fish, the highest expression of s-IgM was observed in head kidney followed by body kidney, spleen, and mid gut whereas m-IgM expression was the highest in blood followed by head kidney and spleen. In vitro, s-IgM expression was up-regulated by LPS in head kidney and spleen cells at 24 h with no change of m-IgM expression. In vivo upon vaccination, s-IgM expression was up-regulated in liver and blood but not in head kidney while m-IgM expression was only up-regulated in head kidney. After challenge with RBIV, s-IgM expression level was higher in vaccinated fish than in unvaccinated fish and m-IgM expression was up-regulated in head kidney of vaccinated group. In conclusion, differential expression of m-IgM and s-IgM may indicate their differential functions to produce the most effective IgM during adaptive immune response. Although it is not able to assess specific IgM at protein level due to a lack of antibody against rock bream IgM, the present study on s-IgM and m-IgM gene expressions upon infection and vaccination will be useful in developing efficient vaccines in the future.

Analysis of immunoglobulin and T cell receptor gene expression in ballan wrasse (Labrus bergylta) revealed an extraordinarily high IgM expression in the gut

The serum IgM concentration of ballan wrasse is relatively high, estimated to approximately 13 mg/ml in adult wild fish of 800 g. The present study revealed an unusual high abundance of IgM mRNA in the gut of ballan wrasse. Initially, transcripts encoding IgM, IgT, IgD, TCRα, TCRδ and CD3ε were quantified by RT-qPCR in several tissues of wild caught fish (approx. 800 g), indicating an elevated immune activity in hindgut and an extraordinarily high expression of IgM. Subsequently, a new RT-qPCR analysis was performed on the entire intestine, cut into four different segments, of reared fish (32-100 g). The analysis indicated immune activity along the entire intestine, but not as strong as in the hindgut. Furthermore, similar to the larger fish, the relative abundance of IgM transcripts was higher in the hindgut than in kidney and spleen, although the absolute level of IgM was in general higher in the larger fish. The secreted form of IgM was completely dominant in comparison to the membrane bound form of IgM and the other analysed genes. IgM was purified from gut mucus and external mucosal surfaces by magnetic beads coated with protein A. Mucus IgM reacted with rabbit antisera raised against serum IgM and contained subunits of the same size. Regarding the elevated immune activity in the intestine it is tempting to speculate on a possible compensatory strategy in this lineage of stomach-less fish, and that natural antibodies have an important role in the first line defence.

IgM and IgD heavy chains of yellow catfish (Pelteobagrus fulvidraco): Molecular cloning, characterization and expression analysis in response to bacterial infection

Three different immunoglobulin (Ig) isotypes, namely IgM, IgD, and IgT/IgZ have been described in most teleost, among which IgM and IgT are considered crucial in systematic and mucosal immunity, respectively. However, some teleost have no IgT/IgZ and it is unclear how other Ig isotypes interact to perform immune-protective roles in both systematic and mucosal sites. In this study, the complete cDNA sequences of IgM and IgD heavy chains were cloned and analyzed from yellow catfish (Pelteobagrus fulvidraco). The full-length cDNA of Pf-IgM and Pf-IgD heavy chains contained an open reading frame (ORF) of 1710 and 2991 bp encoding a predicted protein of 570 and 997 amino acids, respectively. Tissue-specific expression analysis indicated that both IgM and IgD were highly expressed in kidney and spleen, and higher expression levels were found at zygote and 13th day post hatching during early development. Multiple sequence alignment and phylogenetic analysis showed IgM and IgD of yellow catfish are closely related to other fish of Siluriformes. Moreover, we also constructed the infection model of yellow catfish with bacteria (Flavobacterium columnare G₄) for the first time to study the function of Pf-IgM and Pf-IgD heavy chain genes in immune response. Quantitative real-time PCR (qRT-PCR) showed that significantly up-regulated expression of Pf-IgM was not only detected in liver and spleen, but also in mucosal tissues including skin and intestine, while Pf-IgD was just significantly increased in liver and spleen, which might suggest the main immune-protecting roles of IgM in mucosal tissues of yellow catfish.

Interleukin-6 gets involved in response to bacterial infection and promotes antibody production in Nile tilapia (Oreochromis niloticus)

Interleukin 6 (IL-6), a pleiotropic cytokine, plays an important role in humoral immune response, not only inducing the differentiation of B cells into plasma cells, but also promoting antibody-secreting cells (ASCs) to produce antibodies. In this study, Nile tilapia (Oreochromis niloticus) IL-6 (OnIL-6) was identified and characterized at expression level in response to bacterial infection and promotion of antibody production. The open reading frame of OnIL-6 ORF is consisted of 663 bp encoding a polypeptide of 220 amino acids. The deduced OnIL-6 protein contained an IL-6/G-CSF family signature, two conserved cysteine, and four α-helix bundles, which was highly homologous to other species. Spatial mRNA expression analysis revealed that the highest expression of OnIL-6 was observed in the thymus. After in vivo challenges of lipopolysaccharide (LPS) and Streptococcus agalactia (S. agalactiae), OnIL-6 expressions were significantly up-regulated in head kidney and spleen. The similar up-regulation of OnIL-6 was observed in the head kidney and spleen leukocytes in vitro stimulation with LPS and S. agalactiae. In addition, inducement with the recombinant OnIL-6 ((r)OnIL-6) in vitro caused significant increases in expressions of both sIgM and mIgM. Moreover, the (r)OnIL-6 stimulation enhanced the secretion of sIgM (more especially in P50 plasma-like B cells) and the production of mIgM in P60 and P70 B cell subsets (resting B cells, activated B cells and plasmablast-like B cells) in vitro. Taken together, this study indicated that OnIL-6 might be involved in host defense against bacterial infection and promote the production of antibody in Nile tilapia.

Effect of Lead on Antioxidant Ability and Immune Responses of Crucian Carp

The aim of this study was to explore the effects of lead exposure on the antioxidant and immune responses of Crucian carp. Three hundred sixty healthy Crucian carp were randomly grouped into four groups and exposed to different doses of lead (0, 0.05, 0.5, and 1 mg/L). Fish were sampled at 30 and 60 days, respectively, and antioxidant capability, immune parameters, ALAD activity, and immune-related genes were assessed. The results showed that T-AOC and GSH activities of the liver were significantly increased in 60 days (P < 0.05); the activities of SOD, CAT, T-AOC, and GSH were significantly increased (P < 0.05) compared to the control in the kidney in 60 days. With an increase in Pb dose, the activity and expression of lysozyme and the content of immunoglobulin M were significantly decreased compared to the control. Compared with the control group, the activity of ALAD in the lead-exposed group decreased significantly (P < 0.05). The expression of the HSP70, tumor necrosis factor-α (TNF-α), interleukins (IL-10), and immunoglobulin M genes was all enhanced in lead-exposed group, whereas lysozyme gene expression was decreased. The results indicated that lead induced oxidative stress and had immunotoxic effects on Crucian carp.

ABO phenotype-protected reproduction based on human specific α1,2 L-fucosylation as explained by the Bombay type formation

The metabolic relationship between the formation of the ABO(H) blood group phenotype and human fertility is evident in the case of the (Oh) or Bombay blood type, which Charles Darwin would have interpreted as resulting from reduced male fertility in consanguinities, based on the history of his own family, the Darwin/Wedgwood Dynasty. The classic Bombay type occurs with the extremely rare, human-specific genotype (h/h; se/se), which (due to point mutations) does not encode fucosyltransferases 1(FUT1) and 2 (FUT2). These enzymes are the basis for ABO(H) phenotype formation on the cell surfaces and fucosylation of plasma proteins, involving neonatal immunoglobulin M (IgM). In the normal human blood group O(H), which is not protected by clonal selection with regard to environmental A/B immunization, the plasma contains a mixture of non-immune and adaptive anti-A/B reactive isoagglutinins, which in the O(h) Bombay type show extremely elevated levels, associated with decreased levels of fucosylation-dependent functional plasma proteins, suchs as the van Willebrand factor (vWF) and clotting factor VIII. In fact, while the involvement of adaptive immunoglobulins remains unknown, poor fucosylation may explain the polyreactivity in the Bombay type plasma, which exhibits pronounced complement-binding cross-reactive anti-A/Tn and anti-B IgM levels, with additional anti-H reactivity, acting over a wide range of temperatures, with an amplitude at 37 °C. This aggressive anti-glycan-reactive IgM molecule suggests the induction of ADCC (antibody-dependent) and/or complement-mediated cytotoxicity via overexpressed glycosidic bond sites against the embryogenic stem cell-to-germ cell transformation, which is characterized by fleeting appearances of A-like, developmental trans-species GalNAcα1-O-Ser/Thr-R glycan, also referred to as the Tn (T "nouvelle") antigen.

Efficacy of a Eudragit L30D-55 encapsulated oral vaccine containing inactivated bacteria (Lactococcus garvieae/Streptococcus iniae) in rainbow trout (Oncorhynchus mykiss)

The efficacy of a Eudragit L30D-55 encapsulated vaccine against Lactococcus garvieae and Streptococcus iniae was investigated in rainbow trout. Fish were divided into four groups and fed the different experimental feeds. Groups were: A) fish immunized by Eudragit-coated pellets containing vaccine, B) fish immunized by vaccine-coated pellets without Eudragit, C) fish fed Eudragit-coated pellets without vaccine and D) fish fed pellets without vaccine orEudragit (control group). In groups A and B, the vaccination was conducted for 14 days. Similar to groups A and B, fish of group C were fed 14 days with pellets coated with Eudragit and afterwards they were fed control diet. Serum samples were taken on day 0, 20, 40 and 60 of the experiment. After 60 days, fish were challenged with L. garvieae and S. iniae. In almost all groups, innate immunity components including alternative complement activity, lysozyme activity, bactericidal activity, IgM and total protein showed no significant changes during the 60 days that the experiment lasted. However, the blood respiratory burst activity and lysozyme activity showed a significant increase on day 20 of experiment in groups B and D respectively (P < 0.05). The relative expression of immune-related genes including IL-6 and IgM genes was higher in vaccinated fish, with the highest expression in those immunized by Eudragit-coated pellets (Group A). In addition, the relative expression of IL-6 and IgM peaked on day 20 but decreased on day 60 in vaccinated groups. The ELISA antibody titer against L. garvieae increased from day 20 and peaked on day 60 of experiment (P < 0.05). Also, the antibody titer against L. garvieae was higher in fish immunized by Eudragit-coated pellets (Group A) compared to fish of group C and control. After bacterial challenge, a survival percentages of % 85 ± 7.07% (challenged with S. iniae) and % 72.21 ± 7.8% (challenged with L. garvieae) were observed respectively in groups immunized with pellets coated with Eudragit L30D-55 (Group A), which were higher than survival percentages obtained in other experimental groups (P < 0.05). The results of the present study demonstrate that the oral administration of Eudragit L30D-55-encapsulated vaccine appropriately protects rainbow trout against Lactococcus garvieae and Streptococcus iniae.

A Comprehensive Analysis of the T and B Lymphocytes Repertoire Shaped by HIV Vaccines

The exploitation of various human immunodeficiency virus type-1 (HIV-1) vaccines has posed great challenges for the researchers in precisely evaluating the vaccine-induced immune responses, however, the understanding of vaccination response suffers from the lack of unbiased characterization of the immune landscape. The rapid development of high throughput sequencing (HTS) makes it possible to scrutinize the extremely complicated immunological responses during vaccination. In the current study, three vaccines, namely N36, N51, and 5-Helix based on the HIV-1 gp41 pre-hairpin fusion intermediate were applied in rhesus macaques. We assessed the longitudinal vaccine responses using HTS, which delineated the evolutionary features of both T cell and B cell receptor repertoires with extreme diversities. Upon vaccination, we unexpectedly found significant discrepancies in the landscapes of T-cell and B-cell repertoires, together with the detection of significant class switching and the lineage expansion of the B cell receptor or immunoglobulin heavy chain (IGH) repertoire. The vaccine-induced expansions of lineages were further evaluated for mutation rate, lineage abundance, and lineage size features in their IGH repertoires. Collectively, these findings conclude that the N51 vaccine displayed superior performance in inducing the class-switch of B cell isotypes and promoting mutations of IgM B cells. In addition, the systematic HTS analysis of the immune repertoires demonstrates its wide applicability in enhancing the understanding of immunologic changes during pathogen challenge, and will guide the development, evaluation, and exploitation of new generation of diagnostic markers, immunotherapies, and vaccine strategies.

Immunoglobulin gene analysis as a tool for investigating human immune responses

The human immunoglobulin repertoire is a hugely diverse set of sequences that are formed by processes of gene rearrangement, heavy and light chain gene assortment, class switching and somatic hypermutation. Early B cell development produces diverse IgM and IgD B cell receptors on the B cell surface, resulting in a repertoire that can bind many foreign antigens but which has had self-reactive B cells removed. Later antigen-dependent development processes adjust the antigen affinity of the receptor by somatic hypermutation. The effector mechanism of the antibody is also adjusted, by switching the class of the antibody from IgM to one of seven other classes depending on the required function. There are many instances in human biology where positive and negative selection forces can act to shape the immunoglobulin repertoire and therefore repertoire analysis can provide useful information on infection control, vaccination efficacy, autoimmune diseases, and cancer. It can also be used to identify antigen-specific sequences that may be of use in therapeutics. The juxtaposition of lymphocyte development and numerical evaluation of immune repertoires has resulted in the growth of a new sub-speciality in immunology where immunologists and computer scientists/physicists collaborate to assess immune repertoires and develop models of immune action.

Oxidation-specific epitopes restrain bone formation

Atherosclerosis and osteoporosis are epidemiologically linked and oxidation specific epitopes (OSEs), such as phosphocholine (PC) of oxidized phospholipids (PC-OxPL) and malondialdehyde (MDA), are pathogenic in both. The proatherogenic effects of OSEs are opposed by innate immune antibodies. Here we show that high-fat diet (HFD)-induced bone loss is attenuated in mice expressing a single chain variable region fragment of the IgM E06 (E06-scFv) that neutralizes PC-OxPL, by increasing osteoblast number and stimulating bone formation. Similarly, HFD-induced bone loss is attenuated in mice expressing IK17-scFv, which neutralizes MDA. Notably, E06-scFv also increases bone mass in mice fed a normal diet. Moreover, the levels of anti-PC IgM decrease in aged mice. We conclude that OSEs, whether produced chronically or increased by HFD, restrain bone formation, and that diminished defense against OSEs may contribute to age-related bone loss. Anti-OSEs, therefore, may represent a novel therapeutic approach against osteoporosis and atherosclerosis simultaneously.

Repositioning of an alternative exon sequence of mouse IgM pre-mRNA activates splicing of the preceding intron

Using a transient expression system of mouse IgM mini-gene constructs in mouse B-cell lines and in fibroblast L cell, we investigated splicing of the IgM transcript. We observed that the efficiency of splicing between exons C4 and M1 (C4-to-M1 splicing), the splicing reaction leading to the production of membrane-bound form (microns) mRNA, was drastically affected by mutations in a specific portion of the downstream exon (M2). The results show that the specific exon M2 sequence activates the C4-to-M1 splicing. This activation was not observed when splicing between exons M1 and M2 was abolished by base substitutions at the splice sites. These results indicate that positioning of the downstream exon is crucial for efficient splicing of the preceding intron.

MYD88 L265P Mutation in Lymphoid Malignancies

Next-generation sequencing has revealed cancer genomic landscapes, in which over 100 driver genes that, when altered by intragenic mutations, can promote oncogenesis. MYD88 is a driver gene found in hematologic B-cell malignancies. A missense mutation (L265P) changing leucine at position 265 to proline in MYD88 is found in ∼90% of Waldenström macroglobulinemia (WM) cases and in significant portions of activated B-cell diffuse large B-cell lymphomas and IgM monoclonal gammopathy of undetermined significance. Few cancers such as WM have a single amino acid substitution in one gene like MYD88 L265P that occurs in ∼90% of cases, making WM paradigmatic for study of a single causative mutation in oncogenesis. In this review, we summarize the frequency and cancer spectrum of MYD88 L265P and its downstream effects in lymphoid cancers. Malignant B cells with MYD88 L265P are likely transformed from IgM-producing B cells either in response to T-cell-independent antigens or in response to protein antigens before class switching. We also discuss therapeutic strategies that include targeting Bruton tyrosine kinase and other kinases, interfering with the assembly of MYD88 and its interacting partners, and MYD88 L265P-specific peptide-based immunotherapy. Cancer Res; 78(10); 2457-62. ©2018 AACR.

Accurate immune repertoire sequencing reveals malaria infection driven antibody lineage diversification in young children

Accurately measuring antibody repertoire sequence composition in a small amount of blood is challenging yet important for understanding repertoire responses to infection and vaccination. We develop molecular identifier clustering-based immune repertoire sequencing (MIDCIRS) and use it to study age-related antibody repertoire development and diversification before and during acute malaria in infants (< 12 months old) and toddlers (12-47 months old) with 4-8 ml of blood. Here, we show this accurate and high-coverage repertoire-sequencing method can use as few as 1000 naive B cells. Unexpectedly, we discover high levels of somatic hypermutation in infants as young as 3 months old. Antibody clonal lineage analysis reveals that somatic hypermutation levels are increased in both infants and toddlers upon infection, and memory B cells isolated from individuals who previously experienced malaria continue to induce somatic hypermutations upon malaria rechallenge. These results highlight the potential of antibody repertoire diversification in infants and toddlers.Somatic hypermutation of antibodies can occur in infants but are difficult to track. Here the authors present a new method called MIDCIRS for deep quantitative repertoire sequencing with few cells, and show infants as young as 3 months can expand antibody lineage complexity in response to malaria infection.

Significances of MYD88L265P and CXCR4WHIM Mutations in Waldenstrom Macroglobulinemia

Waldenstrom macroglobulinemia(WM) is a lymphoplasmacytic lymphoma characterized by serum monoclonal IgM immunoglobulin.Recently,the high mutation rates of MYD88^L265P and CXCR4^WHIM have been documented in WM.Furthermore,MYD88^L265P and CXCR4^WHIM are related to the response to target drugs.This article reviews the significances of MYD88^L265P and CXCR4^WHIM in the diagnosis and treatment of WM.

Expansion and differentiation of IgM+ B cells in the rainbow trout peritoneal cavity in response to different antigens

To date, intraperitoneal (i.p.) injection seems to be the most effective vaccination route in aquaculture, as many i.p. administered fish vaccines are capable of conferring strong and long-lasting immune responses. Despite this, how peritoneal leukocytes are regulated upon antigen encounter has only been scarcely studied in fish. Although, in the past, myeloid cells were thought to be the main responders to peritoneal inflammation, a recent study revealed that IgM⁺ B cells are one of the main cell types in the teleost peritoneal cavity in response to pathogenic bacteria. Thus, in the current work, we have focused on establishing how IgM⁺ B cells are recruited into the peritoneum in rainbow trout (Oncorhynchus mykiss) comparing different antigens: Escherichia coli as a bacterial model, E. coli-derived lipopolysaccharide (LPS) or viral hemorrhagic septicemia virus (VHSV). In addition to studying their capacity to dominate the peritoneal cavity, we have established how these IgM⁺ B cells are regulated in response to the different antigens, determining their levels of IgM secretion, surface MHC II expression, cell size and phagocytic abilities. Our results reveal that IgM⁺ B cells are one of the main cell types amplified in the peritoneum in response to either bacterial or viral antigens and that these immunogenic stimulations provoke a differentiation of some of these cells towards plasmablasts/plasma cells whereas others seem to be implicated in antigen presentation. These findings contribute to a better understanding of the immune processes that regulate peritoneal inflammation in teleost fish.

Head kidney, liver and skin histopathology and gene expression in gilthead seabream (Sparus aurata L.) exposed to highly polluted marine sediments from Portman Bay (Spain)

Biomarkers have become crucial tools in modern environmental assessment as they can help to predict magnitude of pollution. The head-kidney (HK) and liver (hematopoietic and xenobiotic metabolism organs, respectively) are the key organs in all fish toxicological studies, although the skin has received less attention in this respect. The impact of two different types of polluted sediment collected from Portman Bay (Spain) on HK, liver and skin gene expression in gilthead seabream (Sparus aurata L.) exposed for two weeks to the sediments was determined by real time-PCR. The expression levels of different antioxidant enzyme genes [superoxide dismutase (sod) glutathione reductase (gr) and catalase (cat)] and immune-related genes [interleukin -1β (il-1b), immunoglobulin M (igm), T-Cell receptor (tcr-b), cyclooxygenase-2 (cox-2), colony-stimulating factor 1-receptor (csf-1r) and hepcidin (hep)] was analysed. Expression varied depending on both the organ and gene studied: tcr-b, csf-1r and hep genes were down-regulated in HK, as were gr, tcr-b and il-1b in liver and gr and il-1b in skin, while cox-2 was up-regulated in skin after exposure to both sediments. Concomitantly, histopathological alterations were also studied in HK, liver and skin. While no significant changes were detected in skin cells of fish reared in aquaria with polluted sediments marked changes in the general morphology of HK and liver were observed, accompanied by a substantial degree of cell death and melano-macrophage centre disorganization. The present study suggests that the biomarkers studied in gilthead seabream could be useful for assessing the impact of pollution in coastal environments.