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Human bone marrow (BM) plasma cells are heterogeneous, ranging from newly arrived antibody-secreting cells (ASCs) to long-lived plasma cells (LLPCs). We provide single-cell transcriptional resolution of 17,347 BM ASCs from five healthy adults. Fifteen clusters are identified ranging from newly minted ASCs (cluster 1) expressing MKI67 and high major histocompatibility complex (MHC) class II that progress to late clusters 5-8 through intermediate clusters 2-4. Additional ASC clusters include the following: immunoglobulin (Ig) M predominant (likely of extra-follicular origin), interferon responsive, and high mitochondrial activity. Late ASCs are distinguished by G2M checkpoints, mammalian target of rapamycin (mTOR) signaling, distinct metabolic pathways, CD38 expression, utilization of tumor necrosis factor (TNF)-receptor superfamily members, and two distinct maturation pathways involving TNF signaling through nuclear factor κB (NF-κB). This study provides a single-cell atlas and molecular roadmap of LLPC maturation trajectories essential in the BM microniche. Altogether, understanding BM ASC heterogeneity in health and disease enables development of new strategies to enhance protective ASCs and to deplete pathogenic ones.

Humoral immunity depends on efficient activation of B cells and their subsequent differentiation into antibody-secreting cells (ASCs). The transcription factor NFκB cRel is critical for B cell proliferation, but incorporating its known regulatory interactions into a mathematical model of the ASC differentiation circuit prevented ASC generation in simulations. Indeed, experimental ectopic cRel expression blocked ASC differentiation by inhibiting the transcription factor Blimp1, and in wild-type (WT) cells cRel was dynamically repressed during ASC differentiation by Blimp1 binding the Rel locus. Including this bi-stable circuit of mutual cRel-Blimp1 antagonism into a multi-scale model revealed that dynamic repression of cRel controls the switch from B cell proliferation to ASC generation phases and hence the respective cell population dynamics. Our studies provide a mechanistic explanation of how dysregulation of this bi-stable circuit might result in pathologic B cell population phenotypes and thus offer new avenues for diagnostic stratification and treatment.

Abstract Background Memory B cells are an antigen-experienced B-cell population with the ability to rapidly differentiate into antibody-producing cells by recall responses. We recently found that dedicator of cytokinesis 11 (DOCK11) contributes to the expansion of antigen-specific populations among germinal center B cells upon immunization. In comparison, limited information is available on the contribution of DOCK11 to secondary humoral immune responses. Results In this study, effects of the DOCK11 deficiency in B cells were examined on secondary immune responses to protein antigen. The lack of DOCK11 in B cells resulted in the impaired induction of antibody-producing cells upon secondary immunization with protein antigen. DOCK11 was dispensable for the recall responses of antigen-experienced B cells, as demonstrated by the comparable induction of antibody-producing cells in mice given transfer of antigen-experienced B cells with no DOCK11 expression. Instead, the lack of DOCK11 in B cells resulted in the impaired secondary immune responses in a B cell-extrinsic manner, which was recovered by the adoptive transfer of cognate T cells. Conclusions We addressed that intrinsic and extrinsic effects of DOCK11 expression in B cells may contribute to secondary humoral immune responses in manner of the induction of cognate T-cell help.

We studied the seasonal variation of adaptive humoral immunity (AHI) in northern red‐backed vole (Clethrionomys rutilus Pallas, 1779, RBV) and gray‐sided vole (C. rufocanus Sundevall, 1846, GSV) in Tomsk region of Western Siberia. Immunoresponsiveness (IR) to sheep red blood cells was assessed by the number of antibody‐producing cells in the spleen. The use of a generalized linear model to analyze the effects of species, sex, year of research, and season of withdrawal of individuals from nature on IR showed a significant effect of species identity, season of animal capture, and the interaction of species with season. The RBV demonstrated higher immune responses during a year, and both species had higher IR in winter. Suppression of IR in spring was greater, started earlier, and lasted longer (March–May) in GSV. In RBV, immunosuppression was restricted to April. The significant negative within year correlations of IR with body mass and masses of reproductive organs in GSV indicated a trade‐off between AHI and growth and reproduction processes. A probable explanation for the difference between species in the seasonal variation of AHI may be related to the difference in tropho‐energetic requirements of each vole species. GSV is a predominantly herbivorous rodent and its thermoregulation seems less efficient than of RBV. The deeper spring immunosuppression in GSV may explain in part its higher mortality during the season of colds. [ABSTRACT FROM AUTHOR]

Abstract We studied the seasonal variation of adaptive humoral immunity (AHI) in northern red‐backed vole (Clethrionomys rutilus Pallas, 1779, RBV) and gray‐sided vole (C. rufocanus Sundevall, 1846, GSV) in Tomsk region of Western Siberia. Immunoresponsiveness (IR) to sheep red blood cells was assessed by the number of antibody‐producing cells in the spleen. The use of a generalized linear model to analyze the effects of species, sex, year of research, and season of withdrawal of individuals from nature on IR showed a significant effect of species identity, season of animal capture, and the interaction of species with season. The RBV demonstrated higher immune responses during a year, and both species had higher IR in winter. Suppression of IR in spring was greater, started earlier, and lasted longer (March–May) in GSV. In RBV, immunosuppression was restricted to April. The significant negative within year correlations of IR with body mass and masses of reproductive organs in GSV indicated a trade‐off between AHI and growth and reproduction processes. A probable explanation for the difference between species in the seasonal variation of AHI may be related to the difference in tropho‐energetic requirements of each vole species. GSV is a predominantly herbivorous rodent and its thermoregulation seems less efficient than of RBV. The deeper spring immunosuppression in GSV may explain in part its higher mortality during the season of colds.

Natural IgM plays a critical role in protection from pathogens and the prevention of autoimmunity. While its importance has been shown in many different settings, its origins are incompletely understood. This review focuses on the properties of the natural IgM antibody-secreting cells (ASCs), which arise mainly from the B-1 cell lineage. B-1 cells are generated in multiple waves during development, mostly in the fetal and early postfetal periods. The developmental time points can affect their repertoire: prenatal B-1 cells express a mainly germ line-encoded repertoire, while postnatally developing B-1 cells can express Ig with a greater degree of variation. Spleen and bone marrow, but not the body cavities, are primary sites of natural IgM secretion. Within these tissues heterogeneous populations of IgM ASCs can be found. While some ASCs express classical markers of B-1 lymphocytes, others express those of terminally differentiated plasma cells. A better understanding of the properties of these different natural IgM ASCs could aid their future therapeutic exploitation.

Background: Memory B cells are an antigen-experienced B-cell population with the ability to rapidly differentiate into antibody-producing cells by recall responses. We recently found that dedicator of cytokinesis 11 (DOCK11) contributes to the expansion of antigen-specific populations among germinal center B cells upon immunization. In comparison, limited information is available on the contribution of DOCK11 to secondary humoral immune responses. Results: In this study, effects of the DOCK11 deficiency in B cells were examined on secondary immune responses to protein antigen. The lack of DOCK11 in B cells resulted in the impaired induction of antibody-producing cells upon secondary immunization with protein antigen. DOCK11 was dispensable for the recall responses of antigen-experienced B cells, as demonstrated by the comparable induction of antibody-producing cells in mice given transfer of antigen-experienced B cells with no DOCK11 expression. Instead, the lack of DOCK11 in B cells resulted in the impaired secondary immune responses in a B cell-extrinsic manner, which was recovered by the adoptive transfer of cognate T cells. Conclusions: We addressed that intrinsic and extrinsic effects of DOCK11 expression in B cells may contribute to secondary humoral immune responses in manner of the induction of cognate T-cell help. [ABSTRACT FROM AUTHOR]

UnlabelledThe serologic hallmark of primary biliary cirrhosis (PBC), the antimitochondrial response to the E2 component of the pyruvate dehydrogenase complex (PDC-E2), has unique features, including continuous high titers of immunoglobulin M (IgM) and IgG reactivity throughout all stages of disease, capable not only of target enzyme inhibition, but also crossreactive with chemical xenobiotics that share molecular homology with the inner lipoyl domain of PDC-E2; such chemicals have been proposed as potential etiological agents. We used flow cytometry and enzyme-linked immunospot assay (ELISPOT) to examine B-cell subsets in 59 subjects, including 28 with PBC, 13 with primary sclerosing cholangitis (PSC), and 18 healthy controls. Strikingly, in PBC, although there were no significant differences in B-cell phenotype subpopulations, 10% of the total IgG and IgA plasmablast population and 23% of the IgM plasmablast population were uniquely reactive with PDC-E2, detected in the CXCR7+ CCR10low plasmablast population. In contrast, plasmablast reactivity to a control antigen, tetanus toxoid, was minimal and similar in all groups. Additionally, we isolated plasmablast-derived polyclonal antibodies and compared reactivity with plasma-derived antibodies and noted a distinct noncirculating tissue source of xenobiotic crossreacting antibodies. The high levels of autoantigen specific peripheral plasmablasts indicate recent activation of naive or memory B cells and a continuous and robust activation. The presence of CXCR7+ CCR10low PDC-E2-specific ASCs suggests a mechanistic basis for the migration of circulating antigen specific plasmablasts to the mucosal epithelial ligands CXCL12 and CCL28.ConclusionOur findings suggest a sustained rigorous B-cell response in PBC, likely activated and perpetuated by cognate autoantigen.

While cellular metabolism was proposed to be a driving factor of the activation and differentiation of B cells and the function of the resulting antibody-secreting cells (ASCs), the study of correlations between cellular metabolism and functionalities has been difficult due to the absence of technologies enabling the parallel measurement. Herein, we performed single-cell transcriptomics and introduced a direct concurrent functional and metabolic flux quantitation of individual murine B cells. Our transcriptomic data identified lactate metabolism as dynamic in ASCs, but antibody secretion did not correlate with lactate secretion rates (LSRs). Instead, our study of all splenic B cells during an immune response linked increased lactate metabolism with acidic intracellular pH and the upregulation of apoptosis. T cell-dependent responses increased LSRs, and added TLR4 agonists affected the magnitude and boosted LSR high B cells in vivo, while resulting in only a few immunoglobulin-G secreting cells (IgG-SCs). Therefore, our observations indicated that LSR high cells were not differentiating into IgG-SCs, and were rather removed due to apoptosis., (© 2024. The Author(s).)

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple autoantibody types, some of which are produced by long-lived plasma cells (LLPC). Active SLE generates increased circulating antibody-secreting cells (ASC). Here, we examine the phenotypic, molecular, structural, and functional features of ASC in SLE. Relative to post-vaccination ASC in healthy controls, circulating blood ASC from patients with active SLE are enriched with newly generated mature CD19 - CD138 + ASC, similar to bone marrow LLPC. ASC from patients with SLE displayed morphological features of premature maturation and a transcriptome epigenetically initiated in SLE B cells. ASC from patients with SLE exhibited elevated protein levels of CXCR4, CXCR3 and CD138, along with molecular programs that promote survival. Furthermore, they demonstrate autocrine production of APRIL and IL-10, which contributed to their prolonged in vitro survival. Our work provides insight into the mechanisms of generation, expansion, maturation and survival of SLE ASC., (© 2024. The Author(s).)

The contribution of B cells to the pathology of Omenn syndrome and leaky severe combined immunodeficiency (SCID) has not been previously investigated. We have studied a mut/mut mouse model of leaky SCID with a homozygous Rag1 S723C mutation that impairs, but does not abrogate, V(D)J recombination activity. In spite of a severe block at the pro-B cell stage and profound B cell lymphopenia, significant serum levels of immunoglobulin (Ig) G, IgM, IgA, and IgE and a high proportion of Ig-secreting cells were detected in mut/mut mice. Antibody responses to trinitrophenyl (TNP)-Ficoll and production of high-affinity antibodies to TNP-keyhole limpet hemocyanin were severely impaired, even after adoptive transfer of wild-type CD4(+) T cells. Mut/mut mice produced high amounts of low-affinity self-reactive antibodies and showed significant lymphocytic infiltrates in peripheral tissues. Autoantibody production was associated with impaired receptor editing and increased serum B cell-activating factor (BAFF) concentrations. Autoantibodies and elevated BAFF levels were also identified in patients with Omenn syndrome and leaky SCID as a result of hypomorphic RAG mutations. These data indicate that the stochastic generation of an autoreactive B cell repertoire, which is associated with defects in central and peripheral checkpoints of B cell tolerance, is an important, previously unrecognized, aspect of immunodeficiencies associated with hypomorphic RAG mutations.

After induction in secondary lymphoid organs, a subset of antibody-secreting cells (ASCs) homes to the bone marrow (BM) and contributes to long-term antibody production. The factors determining secondary lymphoid organ residence versus BM tropism have been unclear. Here we demonstrate that in mice treated with FTY720 or that lack sphingosine-1-phosphate (S1P) receptor-1 (S1P1) in B cells, IgG ASCs are induced and localize normally in secondary lymphoid organs but they are reduced in numbers in blood and BM. Many IgG ASCs home to BM on day 3 of the secondary response and day 3 splenic ASCs exhibit S1P responsiveness, whereas the cells remaining at day 5 are unable to respond. S1P1 mRNA abundance is higher in ASCs isolated from blood compared to spleen, whereas CXCR4 expression is lower. Blood ASCs also express higher amounts of Kruppel-like factor (KLF)2, a regulator of S1P1 gene expression. These findings establish an essential role for S1P1 in IgG plasma cell homing and they suggest that differential regulation of S1P1 expression in differentiating plasma cells may determine whether they remain in secondary lymphoid organs or home to BM.

Protective immune responses to many pathogens depend on the development of high-affinity antibody-producing plasma cells (PC) in germinal centers (GCs). Transgenic models suggest that there is a stringent affinity-based barrier to PC development. Whether a similar high-affinity barrier regulates PC development under physiologic circumstances and the nature of the PC fate decision has not been defined precisely. Here, we use a fate-mapping approach to examine the relationship between GC B cells selected to undergo additional rounds of affinity maturation, GC pre-PC, and PC. The data show that initial PC selection overlaps with GC B cell selection, but that the PC compartment accumulates a less diverse and higher affinity collection of antibodies over time. Thus, whereas the GC continues to diversify over time, affinity-based pre-PC selection sieves the GC to enable the accumulation of a more restricted group of high-affinity antibody-secreting PC., (© 2023 ElTanbouly et al.)

The Epstein-Barr virus (EBV) induces B-cell proliferation with high efficiency through expression of latent proteins and microRNAs. This process takes place in vivo soon after infection, presumably to expand the virus reservoir, but can also induce pathologies, e.g. an infectious mononucleosis (IM) syndrome after primary infection or a B-cell lymphoproliferation in immunosuppressed individuals. In this paper, we investigated the growth characteristics of EBV-infected B-cells isolated from transplant recipients or patients with IM. We found that these cells grew and withstood apoptosis at highly variable rates, suggesting that the expansion rate of the infected B-cells widely varies between individuals, thereby influencing the size of the B-cell reservoir and the ability to form tumors in infected individuals. All viruses investigated were type 1 and genetically close to western strains. EBV-infected B-cells expressed the transforming EBV latent genes and microRNAs (miRNAs) at variable levels. We found that the B-cell growth rates positively correlated with the BHRF1 miRNA levels. Comparative studies showed that infected B-cells derived from transplant recipients with iEBVL on average expressed higher levels of EBV miR-BHRF1 miRNAs and grew more rapidly than B-cells from IM patients, suggesting infection by more transforming viruses. Altogether, these findings suggest that EBV infection has a highly variable impact on the B-cell compartment that probably reflects the genetic diversity of both the virus and the host. It also demonstrates the unexpected finding that B-cells from different individuals can grow at different speed under the influence of the same virus infection. [ABSTRACT FROM AUTHOR]

Immunotherapy shows a promise for treating glioblastoma (GBM), the most malignant and immunosuppressive glioma. The mesenchymal phenotype of cancer cells was frequently reported to be associated with their induction of immunosuppression within the cancer microenvironment. Overexpressed insulin-like growth factor binding protein 2 (IGFBP2) promotes GBM cell migration and invasion, and contributes to glioma progression and cancer recurrence and poor survival in GBM. However, whether IGFBP2 can induce immunosuppression in GBM was not reported yet. Thus, the study applied a syngeneic mouse GBM model, human GBM samples, and cancer-immune cell co-culture experiments to investigate the effect of IGFBP2 on GBM exposed immune cells and its association with the mesenchymal induction. We found that IGFBP2 promoted the mesenchymal feature of GBM cells. The inhibition of IGFBP2 relieved immunosuppression by increasing CD8+ T and CD19+ B cells and decreasing CD163+ M2 macrophages. Further, the IGFBP2-promoted immunosuppression was associated with its induction of the mesenchymal feature of GBM cells and the inhibitory phosphorylated FcγRIIB of GBM exposed immune cells. Blocking IGFBP2 suppressed tumor growth and improved survival of tumor bearing mice in the mouse GBM model. These findings support the notion that targeting the IGFBP2 may present an effective immunotherapeutic strategy for mesenchymal GBMs. [ABSTRACT FROM AUTHOR]

Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling is critical to multiple cellular processes, including survival, differentiation, and proliferation. JAK-STAT signaling dysregulation has been noted in inflammatory disorders, and aberrant JAK2 pathway activation has been implicated in myelofibrosis and polycythemia vera. Moreover, 4 therapeutic JAK2 inhibitors (ruxolitinib, fedratinib, momelotinib, and pacritinib) have either been approved or are in advanced clinical development for myelofibrosis. Although all inhibit JAK2, reports indicate that they also inhibit other kinases. Profiling based solely on in vitro potencies is insufficient to predict the observed clinical effects. To provide further translational insights into clinical outcomes, we compared phenotypic biomarker profiles of ruxolitinib, fedratinib, momelotinib, and pacritinib in the BioMAP® Diversity PLUS panel of 12 human primary cell systems designed to recapitulate key aspects of tissue and disease states. Biomarker activity profiles that represent mechanistic signatures for each agent were compared with each other and a database of reference benchmark profiles. At clinically relevant concentrations, these agents had distinct biomarker impacts indicating diverse mechanistic signatures, suggesting divergent clinical effects for each agent. They disparately modulated inflammatory cytokine production and immune function. At clinically relevant concentrations, ruxolitinib had the broadest scope of activities across all 12 cellular systems, whereas pacritinib was more specific for the BT system (modelling T cell-dependent B cell activation) and exhibited the strongest inhibition of sIL-17A, sIL-2, and sIL-6. All 4 agents were antiproliferative to B cells, but ruxolitinib and momelotinib were also antiproliferative to T cells. These differential activities likely reflect distinct secondary pharmacology for these agents known primarily as JAK2 inhibitors. The phenotypic analysis reported herein represents key data on distinct modes-of-action that may provide insights on clinical outcomes reported for these agents. Such translational findings may also inform the development of next-generation molecules with improved efficacy and safety. [ABSTRACT FROM AUTHOR]

Introduction: HLA-incompatible (HLAi) and ABO-incompatible (ABOi) kidney transplantation (KT) has been on the increase over the last decade. However, there are wide variations in outcomes from these procedures. In this study we evaluated the graft and patient outcomes in incompatible KT and non-sensitized KT. Methods: Patients who underwent KT between January 2012 and April 2018 were enrolled and reviewed. We divided kidney transplant recipients (KTRs) into five groups as follows: HLAi (n = 50); ABOi (n = 65); HLAi+ABOi (n = 5); control (n = 428); and living-donor control (LD control, n = 218). We compared the risk of rejection, graft function, graft survival, and patient survival between incompatible KTRs and control/LD control KTRs. Results: Although the incidence of active antibody-mediated rejection in HLAi group tends to be higher than in control and LD control groups (6.0% vs. 2.8%, P = 0.20; 6.0% vs. 3.7%, P = 0.44, respectively), the rejection-free survival, graft survival, and patient survival were not significantly different from those of the control and LD control groups in all three incompatible KT groups (all P>0.05). Graft function during the study period was also not different between incompatible KTRs and control/LD control groups (both P>0.05). Using Cox regression analysis, neither HLAi nor ABOi were risk factors for graft failure. Some infectious diseases such as urinary tract infection and cytomegalovirus infection were more common in the HLAi group than in the control/LD control group (both P<0.05), but only one infection-related death occurred in HLAi KTRs. Infection risks were similar in the ABOi and HLAi+ABOi groups compared to controls. Conclusion: Our results showed favorable outcomes for incompatible KT after desensitization. Although desensitization therapy for incompatible KT has improved access to transplantation for KT candidates with high immunological risk, more clinical data are clearly needed. [ABSTRACT FROM AUTHOR]

Plasmodium relapses are attributed to the activation of dormant liver-stage parasites and are responsible for a significant number of recurring malaria blood-stage infections. While characteristic of human infections caused by P. vivax and P. ovale, their relative contribution to malaria disease burden and transmission remains poorly understood. This is largely because it is difficult to identify ‘bona fide’ relapse infections due to ongoing transmission in most endemic areas. Here, we use the P. cynomolgi–rhesus macaque model of relapsing malaria to demonstrate that clinical immunity can form after a single sporozoite-initiated blood-stage infection and prevent illness during relapses and homologous reinfections. By integrating data from whole blood RNA-sequencing, flow cytometry, P. cynomolgi-specific ELISAs, and opsonic phagocytosis assays, we demonstrate that this immunity is associated with a rapid recall response by memory B cells that expand and produce anti-parasite IgG1 that can mediate parasite clearance of relapsing parasites. The reduction in parasitemia during relapses was mirrored by a reduction in the total number of circulating gametocytes, but importantly, the cumulative proportion of gametocytes increased during relapses. Overall, this study reveals that P. cynomolgi relapse infections can be clinically silent in macaques due to rapid memory B cell responses that help to clear asexual-stage parasites but still carry gametocytes. [ABSTRACT FROM AUTHOR]

Epstein-Barr virus (EBV) causes infectious mononucleosis and is associated with multiple human malignancies. EBV drives B-cell proliferation, which contributes to the pathogenesis of multiple lymphomas. Yet, knowledge of how EBV subverts host biosynthetic pathways to transform resting lymphocytes into activated lymphoblasts remains incomplete. Using a temporal proteomic dataset of EBV primary human B-cell infection, we identified that cholesterol and fatty acid biosynthetic pathways were amongst the most highly EBV induced. Epstein-Barr nuclear antigen 2 (EBNA2), sterol response element binding protein (SREBP) and MYC each had important roles in cholesterol and fatty acid pathway induction. Unexpectedly, HMG-CoA reductase inhibitor chemical epistasis experiments revealed that mevalonate pathway production of geranylgeranyl pyrophosphate (GGPP), rather than cholesterol, was necessary for EBV-driven B-cell outgrowth, perhaps because EBV upregulated the low-density lipoprotein receptor in newly infected cells for cholesterol uptake. Chemical and CRISPR genetic analyses highlighted downstream GGPP roles in EBV-infected cell small G protein Rab activation. Rab13 was highly EBV-induced in an EBNA3-dependent manner and served as a chaperone critical for latent membrane protein (LMP) 1 and 2A trafficking and target gene activation in newly infected and in lymphoblastoid B-cells. Collectively, these studies identify highlight multiple potential therapeutic targets for prevention of EBV-transformed B-cell growth and survival. [ABSTRACT FROM AUTHOR]

Previous studies in rodents have indicated that only a minor fraction of the immunoglobulin heavy chain variable region (IGHV-Cμ) transcripts carry somatic mutations and are considered memory B cells. This is in marked contrast to humans where nearly all marginal zone B (MZ-B) cells are mutated. Here we show in rats that the proportion of mutated IgM+ MZ-B cells varies significantly between the various IGHV genes analyzed, ranging from 27% mutated IGHV5 transcripts to 65% mutated IGHV4 transcripts. The observed data on mutated sequences in clonally-related B cells with a MZ-B cell or follicular B (FO-B) cell phenotype indicate that mutated IgM+ MZ-B and FO-B cells have a common origin. To further investigate the origin of mutated IgM+ MZ-B cells we determined whether mutations occurred in rearranged IGHV-Cμ transcripts using IGHV4 and IGHV5 genes from neonatal rat MZ-B cells and FO-B cells. We were not able to detect mutations in any of the IGHV4 and IGHV5 genes expressed by MZ-B cells or FO-B cells obtained from neonatal rat spleens. Germinal centres (GCs) are absent from neonatal rat spleen in the first few weeks of their life, and no mutations were found in any of the neonatal sequences, not even in the IGHV4 gene family which accumulates the highest number of mutated sequences (66%) in the adult rat. Therefore, these data do not support the notion that MZ-B cells in rats mutate their IGHV genes as part of their developmental program, but are consistent with the notion that mutated rat MZ-B cells require GCs for their generation. Our findings support that the splenic MZ of rats harbors a significant number of memory type IgM+ MZ-B cells with mutated IGHV genes and propose that these memory MZ-B cells are probably generated as a result of an antigen driven immune response in GCs, which still remains to be proven. [ABSTRACT FROM AUTHOR]

Although the efforts to develop vaccine against Toxoplasma gondii infection were made for decades, there is currently no licensed vaccine available for humans. Upon discovering a number of T or B cell epitope regions from T. gondii IMC, ROP18 and MIC8, multi-antigen VLPs or combination VLPs were generated. Mice immunized with multi-antigen VLPs or combination VLPs were challenge infected with T. gondii (ME49). T. gondii-specific IgG, IgG isotypes and IgA antibody responses, memory T and B cell responses and protection were evaluated. All the mice survived upon T. gondii challenge infection by multi-antigen VLPs vaccination. Vaccinated mice elicited higher levels of parasite-specific IgG and IgG2a antibody responses in sera, IgA antibody responses in feces, CD4+ and CD8+ T cell responses, and cytokines (IFN-γ, IL-10) responses compared to combination VLPs. In particular, the multi-antigen VLPs vaccination showed significantly higher levels of antibody secreting cell (ASC) responses, CD4+ and CD8+ effector memory T cells, and memory B cells than combination VLPs. Multi-antigen VLPs vaccination showed significant reduction of brain cyst counts and size, and all mice survived. Prediction and analysis of epitopes have indicated that IMC, ROP18 and MIC8 showed partially overlapping epitopes for T and B cells. Our results indicated that antibody responses, memory T and B cells induced by multi-antigen VLPs vaccination might contribute to the complete protection upon T. gondii (ME49) challenge infection. [ABSTRACT FROM AUTHOR]

Enhancer of zeste homolog 2 (EZH2) tri-methylates histone 3 at position lysine 27 (H3K27me3). Overexpression and gain-of-function mutations in EZH2 are regarded as oncogenic drivers in lymphoma and other malignancies due to the silencing of tumor suppressors and differentiation genes. EZH2 inhibition is sought to represent a good strategy for tumor therapy. In this study, we treated Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL) cell lines with 3-deazaneplanocin—A (DZNep), an indirect EZH2 inhibitor which possesses anticancer properties both in-vitro and in-vivo. We aimed to address the impact of the lymphoma type, EZH2 mutation status, as well as MYC, BCL2 and BCL6 translocations on the sensitivity of the lymphoma cell lines to DZNep-mediated apoptosis. We show that DZNep inhibits proliferation and induces apoptosis of these cell lines independent of the type of lymphoma, the EZH2 mutation status and the MYC, BCL2 and BCL6 rearrangement status. Furthermore, DZNep induced a much stronger apoptosis in majority of these cell lines at a lower concentration, and within a shorter period when compared with EPZ-6438, a direct EZH2 inhibitor currently in phase II clinical trials. Apoptosis induction by DZNep was both concentration-dependent and time-dependent, and was associated with the inhibition of EZH2 and subsequent downregulation of H3K27me3 in DZNep-sensitive cell lines. Although EZH2, MYC, BCL2 and BCL6 are important prognostic biomarkers for lymphomas, our study shows that they poorly influence the sensitivity of lymphoma cell lines to DZNep-mediated apoptosis. [ABSTRACT FROM AUTHOR]

Gammaherpesviruses, including the human pathogens Epstein-Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV), establish lifelong latent infection in B cells and are associated with a variety of tumors. In addition to protein coding genes, these viruses encode numerous microRNAs (miRNAs) within their genomes. While putative host targets of EBV and KSHV miRNAs have been previously identified, the specific functions of these miRNAs during in vivo infection are largely unknown. Murine gammaherpesvirus 68 (MHV68) is a natural pathogen of rodents that is genetically related to both EBV and KSHV, and thus serves as an excellent model for the study of EBV and KSHV genetic elements such as miRNAs in the context of infection and disease. However, the specific targets of MHV68 miRNAs remain completely unknown. Using a technique known as qCLASH (quick crosslinking, ligation, and sequencing of hybrids), we have now identified thousands of Ago-associated, direct miRNA-mRNA interactions during lytic infection, latent infection and reactivation from latency. Validating this approach, detailed molecular analyses of specific interactions demonstrated repression of numerous host mRNA targets of MHV68 miRNAs, including Arid1a, Ctsl, Ifitm3 and Phc3. Notably, of the 1,505 MHV68 miRNA-host mRNA targets identified in B cells, 86% were shared with either EBV or KSHV, and 64% were shared among all three viruses, demonstrating significant conservation of gammaherpesvirus miRNA targeting. Pathway analysis of MHV68 miRNA targets further revealed enrichment of cellular pathways involved in protein synthesis and protein modification, including eIF2 Signaling, mTOR signaling and protein ubiquitination, pathways also enriched for targets of EBV and KSHV miRNAs. These findings provide substantial new information about specific targets of MHV68 miRNAs and shed important light on likely conserved functions of gammaherpesvirus miRNAs. [ABSTRACT FROM AUTHOR]

Introduction: One of the main problems involved in heart transplantation (HT) is antibody-mediated rejection (AMR). Many aspects of AMR are still unresolved, including its etiology, diagnosis and treatment. In this project, we hypothesize that variants in genes involved in B-cell biology in HT patients can yield diagnostic and prognostic information about AMR. Methods: Genetic variants in 61 genes related to B-cell biology were analyzed by next generation sequencing in 46 HT patients, 23 with and 23 without AMR. Results: We identified 3 single nucleotide polymorphisms in ITGA4 gene (c.1845G>A, c.2633A>G, and c.2883C>T) that conformed the haplotype AGT-ITGA4. This haplotype is associated with the development of AMR. Moreover, AMR patients with the haplotype AGT-ITGA4 present lower levels of integrin α-4 in serum samples compared to the reference GAC haplotype in control patients. Conclusion: We can conclude that polymorphisms in genes related to the biology of B-cells could have an important role in the development of AMR. In fact, the AGT haplotype in ITGA4 gene could potentially increase the risk of AMR. [ABSTRACT FROM AUTHOR]

The success of staphylococci as pathogens has been attributed, in part, to their ability to evade their hosts’ immune systems. Although the proteins involved in evasion have been extensively studied in staphylococci affecting humans little characterization has been done with Staphylococcus pseudintermedius, an important cause of pyoderma in dogs. Staphylococcus aureus binder of immunoglobulin (Sbi) interferes with innate immune recognition by interacting with multiple host proteins. In this study, a S. pseudintermedius gene that shares 38% similarity to S. aureus Sbi was cloned from S. pseudintermedius strains representative of major clonal lineages bearing two paralogs of the protein. Binding of immunoglobulins and Fab and Fc fragments as well as interaction with complement was measured. S. pseudintermedius Sbi protein bound IgG from multiple species and canine complement C3, neutralized complement activity and bound to canine IgM and B cells. Evidence from this work suggests Sbi may play an important role in S. pseudintermedius immune evasion. [ABSTRACT FROM AUTHOR]

Thy28, also known as ThyN1, is a highly conserved nuclear protein. We previously showed that in a chicken mature B cell line, Thy28 binds to the promoter of the gene encoding Pax5, a transcription factor essential for B cell development, and positively regulates its expression. Here, we generated a Thy28-deficient mouse line to analyze its potential role in B cell development in mice. Thy28-deficient mice showed normal development of B cells, and the expression of Pax5 was comparable between wild-type and Thy28-deficient primary B cells. Thus, species-specific mechanisms regulate Pax5 expression and B cell development. [ABSTRACT FROM AUTHOR]

In chronically infected HCV patients emergence and evolution of fibrosis, as a consequence of virus persistence, can be considered as an indicator of disease advancement. Therefore the aim of this study was to correlate alterations of immune response in chronic HCV patients with liver histopathology. Sera cytokine levels and frequency of circulating and liver infiltrating cells were evaluated using 13plex Kit Flow Cytomix, flow cytometry and immunohistochemistry. We found that the number of circulating T lymphocytes (including CD4+, CD8+ and Treg) and B lymphocytes, as well as DCs, was higher in patients with no fibrosis than in healthy subjects. In patients with fibrosis frequency of these cells decreased, and contrarily, in the liver, number of T and B lymphocytes gradually increased with fibrosis. Importantly, in patients with advanced fibrosis, liver infiltrating regulatory T cells and DC-SIGN+ mononuclear cells with immunosuppressive and wound-healing effector functions were abundantly present. Cytokine profiling showed predominance of proinflammatory cytokines in patients with no fibrosis and a tendency of decline in level of all cytokines with severity of liver injury. Lower but sustained IL-4 production refers to Th2 predominance in higher stages of fibrosis. Altogether, our results reveal graduall alterations of immunological parameters during fibrosis evolution and illustrate the course of immunological events through disease progression. [ABSTRACT FROM AUTHOR]

We have previously described a native human monoclonal antibody, TRL1068, that disrupts bacterial biofilms by extracting from the biofilm matrix key scaffolding proteins in the DNABII family, which are present in both gram positive and gram negative bacterial species. The antibiotic resistant sessile bacteria released from the biofilm then revert to the antibiotic sensitive planktonic state. Qualitative resensitization to antibiotics has been demonstrated in three rodent models of acute infections. We report here the surprising discovery that antibodies against the target family were found in all twenty healthy humans surveyed, albeit at a low level requiring a sensitive single B-cell assay for detection. We have cloned 21 such antibodies. Aside from TRL1068, only one (TRL1330) has all the biochemical properties believed necessary for pharmacological efficacy (broad spectrum epitope specificity and high affinity). We suggest that the other anti-DNABII antibodies, while not necessarily curative, reflect an immune response at some point in the donor’s history to these components of biofilms. Such an immune response could reflect exposure to bacterial reservoirs that have been previously described in chronic non-healing wounds, periodontal disease, chronic obstructive pulmonary disease, colorectal cancer, rheumatoid arthritis, and atherosclerotic artery explants. The detection of anti-DNABII antibodies in all twenty surveyed donors with no active infection suggests that bacterial biofilm reservoirs may be present periodically in most healthy individuals. Biofilms routinely shed bacteria, creating a continuous low level inflammatory stimulus. Since chronic subclinical inflammation is thought to contribute to most aging-related diseases, suppression of bacterial biofilm has potential value in delaying age-related pathology. [ABSTRACT FROM AUTHOR]

The subset of pro-inflammatory B cells, called late memory, tissue-like or double negative (DN), accumulates in the blood of elderly individuals. Here we show that DN B cells do not proliferate and do not make antibodies to influenza antigens, but they secrete antibodies with autoimmune reactivity, in agreement with their membrane phenotype (CD95+CD21-CD11c+) and their spontaneous expression of the transcription factor T-bet. These cells also increase in the blood of individuals with obesity and autoimmune diseases, but causative mechanisms and signaling pathways involved are known only in part. In the present paper we compare frequencies and metabolic requirements of these cells in the blood of healthy individuals of different ages and in the blood and the subcutaneous adipose tissue (SAT) of individuals with obesity. Results show that DN B cells from young individuals have minimal metabolic requirements, DN B cells from elderly and obese individuals utilize higher amounts of glucose to perform autoimmune antibody production and enroll in aerobic glycolysis to support their function. DN B cells from the SAT have the highest metabolic requirements as they activate oxidative phosphorylation, aerobic glycolysis and fatty acid oxidation. DN B cells from the SAT also show the highest levels of ROS and the highest levels of phosphorylated AMPK (5’-AMP activated kinase) and Sestrin 1, both able to mitigate stress and cell death. This metabolic advantage drives DN B cell survival and function (secretion of autoimmune antibodies). [ABSTRACT FROM AUTHOR]

Natural variation separates Epstein-Barr virus (EBV) into type 1 and type 2 strains. Type 2 EBV is less transforming in vitro due to sequence differences in the EBV transcription factor EBNA2. This correlates with reduced activation of the EBV oncogene LMP1 and some cell genes. Transcriptional activation by type 1 EBNA2 can be suppressed through the binding of two PXLXP motifs in its transactivation domain (TAD) to the dimeric coiled-coil MYND domain (CC-MYND) of the BS69 repressor protein (ZMYND11). We identified a third conserved PXLXP motif in type 2 EBNA2. We found that type 2 EBNA2 peptides containing this motif bound BS69CC-MYND efficiently and that the type 2 EBNA2TAD bound an additional BS69CC-MYND molecule. Full-length type 2 EBNA2 also bound BS69 more efficiently in pull-down assays. Molecular weight analysis and low-resolution structures obtained using small-angle X-ray scattering showed that three BS69CC-MYND dimers bound two molecules of type 2 EBNA2TAD, in line with the dimeric state of full-length EBNA2 in vivo. Importantly, mutation of the third BS69 binding motif in type 2 EBNA2 improved B-cell growth maintenance and the transcriptional activation of the LMP1 and CXCR7 genes. Our data indicate that increased association with BS69 restricts the function of type 2 EBNA2 as a transcriptional activator and driver of B cell growth and may contribute to reduced B-cell transformation by type 2 EBV. [ABSTRACT FROM AUTHOR]

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder characterized by skin rash (poikiloderma), skeletal dysplasia, small stature, juvenile cataracts, sparse or absent hair, and predisposition to specific malignancies such as osteosarcoma and hematological neoplasms. RTS is caused by germ-line mutations in RECQL4, a RecQ helicase family member. In vitro studies have identified functions for the ATP-dependent helicase of RECQL4. However, its specific role in vivo remains unclear. To determine the physiological requirement and the biological functions of Recql4 helicase activity, we generated mice with an ATP-binding-deficient knock-in mutation (Recql4K525A). Recql4K525A/K525A mice were strikingly normal in terms of embryonic development, body weight, hematopoiesis, B and T cell development, and physiological DNA damage repair. However, mice bearing two distinct truncating mutations Recql4G522Efs and Recql4R347*, that abolished not only the helicase but also the C-terminal domain, developed a profound bone marrow failure and decrease in survival similar to a Recql4 null allele. These results demonstrate that the ATP-dependent helicase activity of Recql4 is not essential for its physiological functions and that other domains might contribute to this phenotype. Future studies need to be performed to elucidate the complex interactions of RECQL4 domains and its contribution to the development of RTS. [ABSTRACT FROM AUTHOR]

Antigen presenting cells (APCs) in the thymus play an essential role in the establishment of central tolerance, i.e. the generation of a repertoire of functional and self-tolerant T cells to prevent autoimmunity. In this study, we have compared the transcriptomes of four primary APCs from human thymus (mTECs, CD19+ B cells, CD141+ and CD123+ DCs). We investigated a set of genes including the HLA genes, genes encoding transcriptional regulators and finally, tissue-enriched genes, i.e, genes with a five-fold higher expression in a particular human tissue. We show that thymic CD141+ DCs express the highest levels of all classical HLA genes and 67% (14/21) of the HLA class I and II pathway genes investigated in this study. CD141+ DCs also expressed the highest levels of the transcriptional regulator DEAF1, whereas AIRE and FEZF2 expression were mainly found in primary human mTECs. We found expression of “tissue enriched genes” from the Human Protein Atlas (HPA) in all four APC types, but the mTECs were clearly dominating in the number of uniquely expressed tissue enriched genes (20% in mTECs, 7% in CD19+ B cells, 4% in CD123+ DCs and 2% in CD141+ DCs). The tissue enriched genes also overlapped with reported human autoantigens. This is, to our knowledge, the first study that performs RNA sequencing of mTECs, CD19+ B cells, CD141+ and CD123+ DCs isolated from the same individuals and provides insight into the transcriptomes of these human thymic APCs. [ABSTRACT FROM AUTHOR]

Mitochondrial antiviral signaling protein (MAVS) is a critical innate immune signaling protein that directs the actions of the RIG-I-like receptor (RLR) signaling pathway of RNA virus recognition and initiation of anti-viral immunity against West Nile virus (WNV). In the absence of MAVS, mice die more rapidly after infection with the pathogenic WNV-Texas (TX) strain, but also produce elevated WNV-specific IgG concomitant with increased viral burden. Here we investigated whether there was a B cell intrinsic role for MAVS during the development of protective humoral immunity following WNV infection. MAVS-/- mice survived infection from the non-pathogenic WNV-Madagascar (MAD) strain, with limited signs of disease. Compared to wildtype (WT) controls, WNV-MAD-infected MAVS-/- mice had elevated serum neutralizing antibodies, splenic germinal center B cells, plasma cells and effector T cells. We found that when rechallenged with the normally lethal WNV-TX, MAVS-/- mice previously infected with WNV-MAD were protected from disease. Thus, protective humoral and cellular immune responses can be generated in absence of MAVS. Mice with a conditional deletion of MAVS only in CD11c+ dendritic cells phenocopied MAVS whole body knockout mice in their humoral responses to WNV-MAD, displaying elevated virus titers and neutralizing antibodies. Conversely, a B cell-specific deletion of MAVS had no effect on immune responses to WNV-MAD compared to WT controls. Thus, MAVS in dendritic cells is required to control WNV replication and thereby regulate downstream humoral immune responses. [ABSTRACT FROM AUTHOR]

Size and composition of γδ T cell populations change dramatically with tissue location, during development, and in disease. Given the functional differentiation of γδ T cell subsets, such shifts might alter the impact of γδ T cells on the immune system. To test this concept, and to determine if γδ T cells can affect other immune cells prior to an immune response, we examined non-immunized mice derived from strains with different genetically induced deficiencies in γδ T cells, for secondary changes in their immune system. We previously saw extensive changes in pre-immune antibodies and B cell populations. Here, we report effects on αβ T cells. Similarly to the B cells, αβ T cells evidently experience the influence of γδ T cells at late stages of their pre-immune differentiation, as single-positive heat stable antigen-low thymocytes. Changes in these and in mature αβ T cells were most prominent with memory-phenotype cells, including both CD8+ and CD4+ populations. As previously observed with B cells, most of the effects on αβ T cells were dependent on IL-4. Unexpectedly, IL-4 seemed to be produced mainly by αβ T cells in the non-immunized mice, albeit strongly regulated by γδ T cells. Similarly to our findings with B cells, changes of αβ T cells were less pronounced in mice lacking all γδ T cells than in mice lacking only some, suggesting that the composition of the γδ T cell population determines the nature of the γδ-influence on the other pre-immune lymphocytes. [ABSTRACT FROM AUTHOR]

Epstein–Barr virus (EBV) is a ubiquitous oncogenic virus that induces many cancers. N6-Methyladenosine (m6A) modification regulates many cellular processes. We explored the role of m6A in EBV gene regulation and associated cancers. We have comprehensively defined m6A modification of EBV latent and lytic transcripts. Furthermore, m6A modification demonstrated a functional role in regulation of the stability of viral transcripts. The methyltransferase METTL14 was induced at the transcript and protein levels, and knock-down of METTL14 led to decreased expression of latent EBV transcripts. METTL14 was also significantly induced in EBV-positive tumors, promoted growth of EBV-transformed cells and tumors in Xenograft animal models. Mechanistically, the viral-encoded latent oncoprotein EBNA3C activated transcription of METTL14, and directly interacted with METTL14 to promote its stability. This demonstrated that EBV hijacks METTL14 to drive EBV-mediated tumorigenesis. METTL14 is now a new target for development of therapeutics for treatment of EBV-associated cancers. [ABSTRACT FROM AUTHOR]

Peptide immunogens provide an approach to focus antibody responses to specific neutralizing sites on the HIV envelope protein (Env) trimer or on other pathogens. However, the physical characteristics of peptide immunogens can limit their pharmacokinetic and immunological properties. Here, we have designed synthetic “star” nanoparticles based on biocompatible N-[(2-hydroxypropyl)methacrylamide] (HPMA)-based polymer arms extending from a poly(amidoamine) (PAMAM) dendrimer core. In mice, these star nanoparticles trafficked to lymph nodes (LNs) by 4 hours following vaccination, where they were taken up by subcapsular macrophages and then resident dendritic cells (DCs). Immunogenicity optimization studies revealed a correlation of immunogen density with antibody titers. Furthermore, the co-delivery of Env variable loop 3 (V3) and T-helper peptides induced titers that were 2 logs higher than if the peptides were given in separate nanoparticles. Finally, we performed a nonhuman primate (NHP) study using a V3 glycopeptide minimal immunogen that was structurally optimized to be recognized by Env V3/glycan broadly neutralizing antibodies (bnAbs). When administered with a potent Toll-like receptor (TLR) 7/8 agonist adjuvant, these nanoparticles elicited high antibody binding titers to the V3 site. Similar to human V3/glycan bnAbs, certain monoclonal antibodies (mAbs) elicited by this vaccine were glycan dependent or targeted the GDIR peptide motif. To improve affinity to native Env trimer affinity, nonhuman primates (NHPs) were boosted with various SOSIP Env proteins; however, significant neutralization was not observed. Taken together, this study provides a new vaccine platform for administration of glycopeptide immunogens for focusing immune responses to specific bnAb epitopes. [ABSTRACT FROM AUTHOR]

B-cell activation yields abundant cell death in parallel to clonal amplification and remodeling of immunoglobulin (Ig) genes by activation-induced deaminase (AID). AID promotes affinity maturation of Ig variable regions and class switch recombination (CSR) in mature B lymphocytes. In the IgH locus, these processes are under control of the 3’ regulatory region (3’RR) super-enhancer, a region demonstrated in the mouse to be both transcribed and itself targeted by AID-mediated recombination. Alternatively to CSR, IgH deletions joining Sμ to “like-switch” DNA repeats that flank the 3’ super-enhancer can thus accomplish so-called “locus suicide recombination” (LSR) in mouse B-cells. Using an optimized LSR-seq high throughput method, we now show that AID-mediated LSR is evolutionarily conserved and also actively occurs in humans, providing an activation-induced cell death pathway in multiple conditions of B-cell activation. LSR either focuses on the functional IgH allele or is bi-allelic, and its signature is mainly detected when LSR is ongoing while it vanishes from fully differentiated plasma cells or from “resting” blood memory B-cells. Highly diversified breakpoints are distributed either within the upstream (3’RR1) or downstream (3’RR2) copies of the IgH 3’ super-enhancer and all conditions activating CSR in vitro also seem to trigger LSR although TLR ligation appeared the most efficient. Molecular analysis of breakpoints and junctions confirms that LSR is AID-dependent and reveals junctional sequences somehow similar to CSR junctions but with increased usage of microhomologies. [ABSTRACT FROM AUTHOR]

During Schistosoma infection, lack of B cells results in more severe granulomas, inflammation, and fibrosis in the liver, but the mechanisms underlying this pathology remain unclear. This study was to clarify the mechanisms underpinning the immunomodulation of B cells in mice infected with Schistosoma japonicum (S. japonicum). We found that B cell deficiency led to aggravated liver pathology, as demonstrated by increases in the size of the egg-associated granulomas, alanine transaminase levels, and collagen deposition. Compared with infected wild-type (WT) mice, infected B cell-deficient (μMT) mice showed increased infiltration of Ly6Chi monocytes and higher levels of proinflammatory cytokines and chemokines. Furthermore, B1 cells were increased significantly in the liver of WT mice following S. japonicum infection. Adoptively transferring B1 cells, but not B2 cells, to μMT mice significantly reduced liver pathology and liver infiltration of Ly6Chi monocytes. Additionally, secretion of IL-10 from hepatic B cells increased significantly in infected WT mice and this IL-10 was mainly derived from B1 cells. Adoptively transferring B1 cells purified from WT mice, but not from IL-10-deficient mice, to μMT mice significantly reduced liver pathology and liver infiltration of Ly6Chi monocytes. These reductions were accompanied by decreases in the expression levels of chemokines and inflammatory cytokines. Taken together, these data indicated that after S. japonicum infection, an increased number of hepatic B1 cells secrete IL-10, which inhibits the expression of chemokines and cytokines and suppresses the infiltration of Ly6Chi monocytes into the liver thereby alleviating liver early inflammation and late fibrosis. [ABSTRACT FROM AUTHOR]

The signaling lymphocytic activation molecule (SLAM) family is comprised of nine distinct receptors that are expressed exclusively on hematopoietic cells. Most of these transmembrane receptors are homotypic by nature and downstream signaling occurs when cells that express the same SLAM receptor interact. Previous studies have determined that anti-SLAMF6 antibodies can have a therapeutic effect in autoimmunity and cancer. However, little is known about the role of SLAMF6 in the adaptive immune responses and in order to utilize SLAMF6 interventional approaches, a better understanding of the biology of this receptor in T cell is warranted. Accordingly, the objective of our study was to investigate both functionally and structurally the role of SLAMF6 in T cell receptor (TCR) mediated responses. Biochemical and genetic experiments revealed that SLAMF6 was required for productive TCR downstream signaling. Interestingly, SLAMF6 ectodomain was required for its function, but not for its recruitment to the immunological synapse. Flow-cytometry analysis demonstrated that tyrosine 308 of the tail of SLAMF6 was crucial for its ability to enhance T cell function. Imaging studies revealed that SLAMF6 clustering, specifically with the TCR, resulted in dramatic increase in downstream signaling. Mechanistically, we showed that SLAMF6 enhanced T cell function by increasing T cell adhesiveness through activation of the small GTPase Rap1. Taken together SLAMF6 is an important regulator of T cell activation where both its ectodomain and its endodomain contribute differentially to T cell functions. Additional studies are underway to better evaluate the role of anti-SLAMF6 approaches in specific human diseases. [ABSTRACT FROM AUTHOR]

Antibodies are important for immunity and exist in several classes (IgM, IgD, IgA, IgG, IgE). They are composed of symmetric dimeric molecules with two antigen binding regions (Fab) and a constant part (Fc), usually depicted as Y-shaped molecules. Rheumatoid factors found in patients with rheumatoid arthritis are autoantibodies binding to IgG and paradoxically appear to circulate in blood alongside with their antigen (IgG) without reacting with it. Here, it is shown that rheumatoid factors do not react with native IgG in solution, and that their epitopes only become accessible upon certain physico-chemical treatments (e.g. heat treatment at 57 °C), by physical adsorption on a hydrophobic surface or by antigen binding. Moreover, chemical cross-linking in combination with mass spectrometry showed that the native state of IgG is a compact (closed) form and that the Fab parts of IgG shield the Fc region and thereby control access of rheumatoid factors and presumably also some effector functions. It can be inferred that antibody binding to pathogen surfaces induces a conformational change, which exposes the Fc part with its effector sites and rheumatoid factor epitopes. This has strong implications for understanding antibody structure and physiology and necessitates a conceptual reformulation of IgG models. [ABSTRACT FROM AUTHOR]

Coxiella burnetii, the agent causing Q fever, has been associated with B-cell non-Hodgkin lymphoma (NHL). To better clarify this link, we analysed the genetic transcriptomic profile of peripheral blood leukocytes from patients with C. burnetii infection to identify possible links to lymphoma. Microarray analyses revealed that 1189 genes were expressed differently (p <.001 and fold change ≥4) in whole blood of patients with C. burnetii infection compared to controls. In addition, 95 genes expressed in patients with non-Hodgkin lymphoma (NHL) and in patients with C. burnetii persistent infection have allowed us to establish the ‘C. burnetii-associated NHL signature’. Among these, 33 genes previously found modulated in C. burnetii-associated -NHL by the microarray analysis were selected and their mRNA expression levels were measured in distinct C. burnetii-induced pathologies, namely, acute Q fever, focalized persistent infection, lymphadenitis and C.burnetii-associated NHL. Specific genes involved in anti-apoptotic process were found highly expressed in leukocytes from patients with C. burnetii associated-NHL: MIR17HG, REL and SP100. This signature differed from that found for NHL-control group. Patients with C. burnetii lymphadenitis presented significant elevated levels of BCL2 and ETS1 mRNAs. Altogether, we identified a specific transcriptionnal signature for NHL during C. burnetii infection reflecting the up-regulation of anti-apoptotic processes and the fact that lymphadenitis might constitute a critical step towards lymphomagenesis. [ABSTRACT FROM AUTHOR]

The ability to appropriately mimic human disease is critical for using animal models as a tool for understanding virus pathogenesis. In the case of Nipah virus (NiV), infection of humans appears to occur either through inhalation, contact with or consumption of infected material. In two of these circumstances, respiratory or sinusoidal exposure represents a likely route of infection. In this study, intermediate-size aerosol particles (~7 μm) of NiV-Malaysia were used to mimic potential routes of exposure by focusing viral deposition in the upper respiratory tract. Our previous report showed this route of exposure extended the disease course and a single animal survived the infection. Here, analysis of the peripheral immune response found minimal evidence of systemic inflammation and depletion of B cells during acute disease. However, the animal that survived infection developed an early IgM response with rapid development of neutralizing antibodies that likely afforded protection. The increase in NiV-specific antibodies correlated with an expansion of the B cell population in the survivor. Cell-mediated immunity was not clearly apparent in animals that succumbed during the acute phase of disease. However, CD4+ and CD8+ effector memory cells increased in the survivor with correlating increases in cytokines and chemokines associated with cell-mediated immunity. Interestingly, kinetic changes of the CD4+ and CD8bright T cell populations over the course of acute disease were opposite from animals that succumbed to infection. In addition, increases in NK cells and basophils during convalescence of the surviving animal were also evident, with viral antigen found in NK cells. These data suggest that a systemic inflammatory response and “cytokine storm” are not major contributors to NiV-Malaysia pathogenesis in the AGM model using this exposure route. Further, these data demonstrate that regulation of cell-mediated immunity, in addition to rapid production of NiV specific antibodies, may be critical for surviving NiV infection. [ABSTRACT FROM AUTHOR]

Virus-host interactions are frequently studied in bulk cell populations, obscuring cell-to-cell variation. Here we investigate endogenous herpesvirus gene expression at the single-cell level, combining a sensitive and robust fluorescent in situ hybridization platform with multiparameter flow cytometry, to study the expression of gammaherpesvirus non-coding RNAs (ncRNAs) during lytic replication, latent infection and reactivation in vitro. This method allowed robust detection of viral ncRNAs of murine gammaherpesvirus 68 (γHV68), Kaposi’s sarcoma associated herpesvirus and Epstein-Barr virus, revealing variable expression at the single-cell level. By quantifying the inter-relationship of viral ncRNA, viral mRNA, viral protein and host mRNA regulation during γHV68 infection, we find heterogeneous and asynchronous gene expression during latency and reactivation, with reactivation from latency identified by a distinct gene expression profile within rare cells. Further, during lytic replication with γHV68, we find many cells have limited viral gene expression, with only a fraction of cells showing robust gene expression, dynamic RNA localization, and progressive infection. Lytic viral gene expression was enhanced in primary fibroblasts and by conditions associated with enhanced viral replication, with multiple subpopulations of cells present in even highly permissive infection conditions. These findings, powered by single-cell analysis integrated with automated clustering algorithms, suggest inefficient or abortive γHV infection in many cells, and identify substantial heterogeneity in viral gene expression at the single-cell level. [ABSTRACT FROM AUTHOR]

BLyS/BAFF is recognized for its role in B-cell ontogenesis, as well as cell fate decision towards the first-line/innate marginal zone (MZ) B-cell pool. Excess BLyS/BAFF is associated with hyperglobulinemia and increased frequencies of activated precursor-like MZ B-cells. Herein, we show that HIV highly-exposed seronegative (HESN) commercial sex workers (CSWs) had lower soluble BLyS/BAFF levels and relative frequencies of BLyS/BAFF expressing cells in their genital mucosa when compared to those from HIV-infected CSWs and HIV-uninfected non-CSWs. Furthermore, we identified genital innate and/or marginal zone (MZ)-like CD1c+ B-cells that naturally bind to fully glycosylated gp120, which frequencies were lower in HESNs when compared to HIV-infected CSWs and HIV-uninfected non-CSWs. Although genital levels of total IgA were similar between groups, HESNs had lower levels of total IgG1 and IgG3. Interestingly, HIV-gp41 reactive IgG1 were found in some HESNs. Low genital levels of BLyS/BAFF observed in HESNs may allow for controlled first-line responses, contributing to natural immunity to HIV. [ABSTRACT FROM AUTHOR]