TLR-mediated stimulation of APC: Distinct cytokine responses of B cells and dendritic cells

Enhancing antibody levels and T cell activity of quadrivalent influenza vaccine by combining it with CpG HP021

Influenza virus infections are a serious danger to people's health worldwide as they are responsible for seasonal flu outbreaks. There is an urgent need to improve the effectiveness and durability longevity of the immune response to influenza vaccines. We synthesized the CpG HP021 and examined the impact of it on the immune response to an influenza vaccine. In BALB/c mice, hemagglutination inhibition (HI) titers to the vaccine were increased four- to eightfold against H1N1, H3N2, BV, and BY viruses by 3 μg IIV4 + 40 μg CpG HP021 compared with those of the non-adjuvanted IIV4 group, and the CpG HP021 group had a broader HI activity. Additionally, the immune response was directed towards Type 1 T helper (Th1) cells due to the CpG HP021 adjuvant. The CpG HP021-adjuvanted IIV4 induced a higher number of T cells secreting interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), and increased the percentage of effector memory T cells in mice. In SD rats, the immune responses induced by IIV4 with CpG HP021 were similar to those in BALB/c mice. The development of CpG HP021 may expand the options for adjuvants in vaccines against infectious diseases.

Exploring the Impact of Biological Agents on Protecting Against Experimental Periodontitis: A Systematic Review of Animal-Based Studies

Aim: This systematic review was aimed at addressing the focused question: What is the protective potential of biological agents against alveolar bone resorption during the progression of experimental periodontitis (EP)? Material and Methods: The study protocol was registered in the Open Science Framework database (doi:10.17605/OSF.IO/3P2HY). A comprehensive literature search was conducted across PubMed, Web of Science, Cochrane Library, Scopus, and Embase databases up to December 2023. Inclusion criteria consisted of preclinical studies in animal models of EP that examined the effects of biological agents on preventing periodontal bone loss and reducing tissue inflammation. Studies were excluded if they (i) used non-EP animal models; (ii) focused on antimicrobial agents; (iii) centered on prebiotics or probiotics; (iv) evaluated compounds not classified as biologicals; or (v) included randomized clinical trials, clinical studies, or reviews. Eligibility was determined based on the PI/ECOs framework, and study quality was assessed using the SYRCLE risk-of-bias tool. Results: After screening an initial pool of 5236 records from databases, registries, and hand searches, 39 studies met the inclusion criteria. A total of 23 biological agents were evaluated across these studies. The majority of studies employed the ligature-induced model of EP to test the effectiveness of biologicals as preventive or therapeutic interventions. The dosage of biological agents and the duration of disease induction varied depending on the EP model. In all studies, the main outcome-alveolar bone loss, a hallmark of EP-was significantly inhibited by biological agents, which also reduced proinflammatory mediators when compared to untreated controls. A key strength of this review is the high number of studies included, most of which were classified as having low risk of bias. However, a notable limitation is the absence of a meta-analysis, the short follow-up periods in the included studies, and the heterogeneity among the compound dosages and route of administration. Conclusion: This systematic review demonstrates that biological agents are effective in reducing bone loss and mitigating inflammation during EP progression. Randomized clinical trials are needed to confirm these findings in human populations.

Plasmacytoid Dendritic Cells Mediate CpG-ODN-induced Increase in Survival in a Mouse Model of Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a devastating disease primarily found in women of reproductive age that leads to cystic destruction of the lungs. Recent work has shown that LAM causes immunosuppression and that checkpoint inhibitors can be used as LAM treatment. Toll-like receptor (TLR) agonists can also reactivate immunity, and the TLR9 agonist CpG oligodeoxynucleotide (CpG-ODN) has been effective in treating lung cancer in animal models. In this study, we investigated the use of TLR9 agonist CpG-ODN as LAM immunotherapy in combination with checkpoint inhibitor anti-PD1 and standard of care rapamycin, and determined the immune mechanisms underlying therapeutic efficacy. We used survival studies, flow cytometry, ELISA, and histology to assess immune response and survival after intranasal treatment with CpG-ODN in combination with rapamycin or anti-PD1 therapy in a mouse model of metastatic LAM. We found that local administration of CpG-ODN enhances survival in a mouse model of LAM. We found that a lower dose led to longer survival, likely because of fewer local side effects, but increased LAM nodule count and size compared with the higher dose. CpG-ODN treatment also reduced regulatory T cells and increased the number of T-helper type 17 cells as well as cytotoxic T cells. These effects appear to be mediated in part by plasmacytoid dendritic cells because depletion of plasmacytoid dendritic cells reduces survival and abrogates T-helper type 17 cell response. Finally, we found that CpG-ODN treatment is effective in early-stage and progressive disease and is additive with anti-PD1 therapy and rapamycin. In summary, we have found that TLR9 agonist CpG-ODN can be used as LAM immunotherapy and effectively synergizes with rapamycin and anti-PD1 therapy in LAM.

Human genital dendritic cell heterogeneity confers differential rapid response to HIV-1 exposure

Dendritic cells (DCs) play critical roles in HIV pathogenesis and require further investigation in the female genital tract, a main portal of entry for HIV infection. Here we characterized genital DC populations at the single cell level and how DC subsets respond to HIV immediately following exposure. We found that the genital CD11c+HLA-DR+ myeloid population contains three DC subsets (CD1c+ DC2s, CD14+ monocyte-derived DCs and CD14+CD1c+ DC3s) and two monocyte/macrophage populations with distinct functional and phenotypic properties during homeostasis. Following HIV exposure, the antiviral response was dominated by DCs' rapid secretory response, activation of non-classical inflammatory pathways and host restriction factors. Further, we uncovered subset-specific differences in anti-HIV responses. CD14+ DCs were the main population activated by HIV and mediated the secretory antimicrobial response, while CD1c+ DC2s activated inflammasome pathways and IFN responses. Identification of subset-specific responses to HIV immediately after exposure could aid targeted strategies to prevent HIV infection.

The predictive value of hematological inflammatory markers for severe oral mucositis in patients with nasopharyngeal carcinoma during intensity-modulated radiation therapy: A retrospective cohort study

BACKGROUND

This study aims to investigate the predictive value of the circulating blood cell count, including neutro-philto-lymphocyte ratio (NLR), platelet-to-lymphocyte (PLR), and thesystemic inflammation index (SII) for the development of severe oral mucositis (SOM) induced by radiation in patients undergoing radiotherapy for nasopharyngeal carcinoma (NPC).

METHODS

In this retrospective study, 142 NPC patients were screened, and based on mucositis toxicity grade, they were categorized into two groups: SOM and nonSOM. Peripheral blood cell counts were conducted prior to Intensity-Modulated Radiation Therapy (IMRT). Associations between blood cell count, NLR, PLR, SII, and SOM occurrence were examined.

RESULTS

Revealed elevated NLR and SII levels, along with reduced lymphocyte (LYM), eosinophil (EOS), and basophil (BAS) in patients with SOM. LYM, EOS, BAS, NLR, and SII were effective predictors of the severity of radiation-induced oral mucositis (RIOM) in NPC patients.

CONCLUSIONS

The occurrence of SOM was strongly linked to the hematological status at the start of Radiation Therapy (RT). Integrating BAS count and NLR into comprehensive risk prediction models could prove valuable for predicting SOM in NPC patients.

Regulation of B-cell function and expression of CD11c, T-bet, and FcRL5 in response to different activation signals

CD11c, FcRL5, or T-bet are commonly expressed by B cells expanding during inflammation, where they can make up >30% of mature B cells. However, the association between the proteins and differentiation and function in the host response remains largely unclear. We have assessed the co-expression of CD11c, T-bet, and FcRL5 in an in vitro B-cell culture system to determine how stimulation via the BCR, toll-like receptor 9 (TLR9), and different cytokines influence CD11c, T-bet, and FcRL5 expression. We observed different expression dynamics for all markers, but a largely overlapping regulation of CD11c and FcRL5 in response to BCR and TLR9 activation, while T-bet was strongly dependent on IFN-γ signaling. Investigating plasma cell differentiation and APC functions, there was no association between marker expression and antibody secretion or T-cell help. Rather the functions were associated with TLR9-signalling and B-cell-derived IL-6 production, respectively. These results suggest that the expression of CD11c, FcRL5, and T-bet and plasma cell differentiation and improved APC functions occur in parallel and are regulated by similar activation signals, but they are not interdependent.

Vaccine adjuvants for infectious disease in the clinic

Adjuvants, materials added to vaccines to enhance the resulting immune response, are important components of vaccination that are many times overlooked. While vaccines always include an antigen to tell the body what to vaccinate to, of equal importance the adjuvant provides the how, a significant factor in producing a complete response. The adjuvant space has been slow to develop with the first use of an adjuvant in a licensed vaccine occurring in the 1930s, and remaining the only adjuvant in licensed vaccines for the next 80 years. However, with vaccination at the forefront of protection against new and complex pathogens, it is important to consider all components when designing an effective vaccine. Here we summarize the adjuvant space in licensed vaccines as well as the novel adjuvant space in clinical trials with a specific focus on the materials utilized and their resulting impact on the immune response. We discuss five major categories of adjuvant materials: aluminum salts, nanoparticles, viral vectors, TLR agonists, and emulsions. For each category, we delve into the current clinical trials space, the impact of these materials on vaccination, as well as some of the ways in which they could be improved. Adjuvants present an exciting opportunity to improve vaccine responses and stability, this review will help inform about the current progress of this space.

Translational impact statement

In the aftermath of the COVID-19 pandemic, vaccines for infectious diseases have come into the spotlight. While antigens have always been an important focus of vaccine design, the adjuvant is a significant tool for enhancing the immune response to the vaccine that has been largely underdeveloped. This article provides a broad review of the history of adjuvants and, the current vaccine adjuvant space, and the progress seen in adjuvants in clinical trials. There is specific emphasis on the material landscape for adjuvants and their resulting mechanism of action. Looking ahead, while the novel vaccine adjuvant space features exciting new technologies and materials, there is still a need for more to meet the protective needs of new and complex pathogens.

Plasmacytoid dendritic cells mediate CpG-ODN induced increase in survival in a mouse model of lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a devastating disease primarily found in women of reproductive age that leads to cystic destruction of the lungs. Recent work has shown that LAM causes immunosuppression and that checkpoint inhibitors can be used as LAM treatment. Toll-like receptor (TLR) agonists can also re-activate immunity and the TLR9 agonist, CpG-ODN, has been effective in treating lung cancer in animal models. Here we investigate the use of TLR9 agonist CpG-ODN as LAM immunotherapy in combination with checkpoint inhibitor, anti-PD1, standard of care rapamycin and determine the immune mechanisms underlying therapeutic efficacy. We used survival studies, flow cytometry, ELISA, and histology to assess immune response and survival after intranasal treatment with CpG-ODN in combination with rapamycin or anti-PD1 therapy in a mouse model of metastatic LAM. We found that local administration of CpG-ODN enhances survival in a mouse model of LAM. We found that a lower dose led to longer survival likely due to fewer local side effects but increased LAM nodule count and size compared to the higher dose. CpG-ODN treatment also reduced regulatory T cells and increased the number of Th17 helper T cells as well as cytotoxic T cells. These effects appear to be mediated in part by plasmacytoid dendritic cells (pDCs), as depletion of pDCs reduces survival and abrogates Th17 T cell response. Finally, we found that CpG-ODN treatment is effective in early stage and progressive disease and is additive with anti-PD1 therapy and rapamycin. In summary, we have found that TLR9 agonist CpG-ODN can be used as LAM immunotherapy and effectively synergizes with rapamycin and anti-PD1 therapy in LAM.

Activation of Toll-like receptor 4 by thyroid hormone triggers abnormal B-cell activation

OBJECTIVE

Breakdown of tolerance and abnormal activation of B cells is an important mechanism in the pathogenesis of Graves' disease (GD). High levels of thyroid hormones (THs) play important roles in GD progression. However, the interactions between THs and abnormal activation of B cells remain elusive. This study aimed to explore the effect of high levels of THs on TLR4 expression and abnormal B cell differentiation.

MATERIALS AND METHODS

Blood samples were collected from patients with GD and healthy controls (HCs) to evaluate the frequency of B cells, their subsets, and TLR4 expression in B cells. A high-level T3 mouse model was used to study the interaction between THs and the TLR4 signalling pathway.

RESULTS

We found that the frequencies of CD19+ , CD19+ TLR4+ , CD19+ CD86+ , and CD19+ CD138+ B cells were significantly higher, as were the expression levels of MRP8/MRP14 and MRP6 and MRP8, MRP14, and MRP6 messenger RNA (mRNA) in peripheral blood mononuclear cells in patients with GD. In high-level T3 mice models, the serum MRP8/MRP14 and MRP6 levels and the TLR4 mRNA expression in PBMCs were significantly higher. TLR4 mRNA, protein expression, and cytokines downstream of TLR4, such as myeloid differentiation factor 88 (MyD88) and nuclear transcription factor-κB, were also increased in mouse spleen mononuclear cells.

CONCLUSION

The present study indicated that high levels of T3 can induce abnormal differentiation and activation of B cells by promoting TLR4 overexpression and provide novel insights into the roles of THs in the pathogenesis of GD.

Hydroxychloroquine protects against autoimmune premature ovarian insufficiency by modulating the Treg/Th17 cell ratio in BALB/c mice

AIMS

The role of hydroxychloroquine (HCQ) in premature ovarian insufficiency (POI) remains unclear. The purpose of this study was to evaluate the effect of HCQ on ovarian function in mice with POI and to clarify its potential mechanisms.

METHODS

POI was induced in mice by injection with zona pellucida 3 peptide (pZP3), and HCQ was administered intragastrically. Stages of the estrous cycle were determined using vaginal cytology. The ovarian structure was observed under a microscope after hematoxylin-eosin staining. The levels of serum hormones and anti-ZP antibody (aZPAb) were measured using enzyme-linked immunosorbent assay (ELISA). The expression levels of CD4, CD45, and ZP2, ZP3 were determined using immunofluorescence and immunohistochemistry, respectively. The T regulatory (Treg)/ T helper 17 (Th17) cell ratio was analyzed using flow cytometry analysis. Western blotting was performed to assess the expression levels of proteins, transcription factors and cytokines.

RESULTS

Administration of HCQ to mice with POI greatly restored their estrus cycle. In the treatment group compared to the POI group, estradiol (E₂ ) levels were higher, and follicle stimulating hormone (FSH) levels were lower. In addition, following pZP3, HCQ treatment increased ZP2 and ZP3 expression. Additionally, by inhibiting the activation of the TLR7 signaling pathway, HCQ attenuated the infiltration of inflammatory cells and prevented the activated naive CD4⁺ T cells from developing into Th17 cells.

CONCLUSION

Our findings showed that HCQ effectively restored ovarian function by altering the Treg/Th17 cell ratio in mice with POI, indicating that HCQ maybe a promising therapeutic method for patients with POI.

Deficiency in TLR4 impairs regulatory B cells production induced by Schistosome soluble egg antigen

Regulatory B cells (Bregs) producing IL-10 have negative regulatory function. Several studies have shown the important roles for Toll-like receptor 2 (TLR2), TLR4, and TLR9 ligation in the development of Bregs. We have reported that Schistosome soluble egg antigen (SEA) induced the production of Bregs. However, it remains unclear whether such activation is via the TLR pathway. The present study showed that IL-10 and TLR4 mRNA expression in spleen B cells of significantly increased in C57BL/10 J mice spleen B cells following SEA stimulation. The level of secreted IL-10 and IL-10⁺ B cell proportion decreased in spleen B cells derived from TLR4-deficient C57BL/10ScNJ (TLR4^-/^-) mice following SEA or LPS stimulation compared with C57BL/10 J mice. The CD1d^hiCD5⁺ B cells proportion decreased in spleen B cells of TLR4^-/^- mice following SEA stimulation compared with control mice. NF-κB, ERK, p38MAPK and JNK signal transduction inhibitors significantly suppressed IL-10 secretion in CD1d^hiCD5⁺ B cells induced by SEA or LPS. The phosphorylation levels of IκBα, p65, ERK, JNK and p38 were increased in CD1d^hiCD5⁺ B cell of C57BL/10 J mice treated with LPS or SEA. In conclusion, this study suggests that TLR4 plays a critical role in Bregs activation induced by SEA. And the TLR4-triggered NF-κB and MAPK pathways activation in CD1d^hiCD5⁺ B cells stimulated with SEA. The findings elucidated the mechanism of SEA induction of CD1d^hiCD5⁺ B cells and helped us to understand the immune regulation during Schistosoma japonicum infection.

Adjuvant effect of dendritic cells activator Imiquimod in genetic immunization with HIV-1 p55 Gag

Dendritic cells (DC) are important antigen-presenting cells that have abilities to induce and maintain T-cell immunity, or attenuate it during hyperimmunization. Additional activation of DCs may be useful for vaccination purposes. Imiquimod is known to be a specific agonist of the Toll-like receptors (TLR7), which are located mainly on DCs. To study the effect of DC stimulation on the effectiveness of an HIV-1 p55 gag DNA vaccine in a mice model, we employed 25, 50, and 100 nM of Imiquimod as an adjuvant. Subsequently, Western blot analysis was used to quantify p55 protein production after the immunization. To characterize T-cells immune response, both the frequency of IFN-γ -secreting cells and IFN-γ and IL-4 production were measured, via an ELIspot assay and ELISA, respectively. Low concentrations of Imiquimod were found to effectively stimulate Gag production and the magnitude of the T-cell immune response, whereas higher concentrations reduced vaccination effects. Our results show that the adjuvant effects of Imiquimod depend on concentration. The use of Imiquimod may be helpful to study DC to T cell communication, including possible induction of immunotolerance.

JAK inhibitors differentially modulate B cell activation, maturation and function: A comparative analysis of five JAK inhibitors in an in-vitro B cell differentiation model and in patients with rheumatoid arthritis

Background

Janus kinase (JAK) inhibitors have been approved for the treatment of several immune-mediated diseases (IMIDs) including rheumatoid arthritis (RA) and psoriatic arthritis and are in clinical trials for numerous other IMIDs. However, detailed studies investigating the effects of different JAK inhibitors on B cells are missing. Within this study, we therefore aimed to characterize the effect of JAK inhibition on the B cell compartment.

Methods

To this end, we investigated the B cell compartment under JAK inhibition and compared the specific effects of the different JAK inhibitors tofacitinib (pan-JAK), baricitinib (JAK1/2), ruxolitinib (JAK1/2), upadacitinib (JAK1/2) as well as filgotinib (selective JAK1) on in-vitro B cell activation, proliferation, and class switch recombination and involved pathways.

Results

While B cell phenotyping of RA patients showed an increase in marginal zone (MZ) B cells under JAK inhibition, comparison with healthy donors revealed that the relative frequency of MZ B cells was still lower compared to healthy controls. In an in-vitro model of T-cell-independent B cell activation we observed that JAK1/2 and selective JAK1 inhibitor treatment led to a dose-dependent decrease of total B cell numbers. We detected an altered B cell differentiation with a significant increase in MZ-like B cells and an increase in plasmablast differentiation in the first days of culture, most pronounced with the pan-JAK inhibitor tofacitinib, although there was no increase in immunoglobulin secretion in-vitro. Notably, we further observed a profound reduction of switched memory B cell formation, especially with JAK1/2 inhibition. JAK inhibitor treatment led to a dose-dependent reduction of STAT3 expression and phosphorylation as well as STAT3 target gene expression and modulated the secretion of pro- and anti-inflammatory cytokines by B cells.

Conclusion

JAK inhibition has a major effect on B cell activation and differentiation, with differential outcomes between JAK inhibitors hinting towards distinct and unique effects on B cell homeostasis.

Pattern recognition receptor ligand-induced differentiation of human transitional B cells

B cells represent a critical component of the adaptive immune response whose development and differentiation are determined by antigen-dependent and antigen-independent interactions. In this study, we explored the effects of IL-4 and pattern-recognition receptor (PRR) ligands on B cell development and differentiation by investigating their capacity to drive the in vitro maturation of human transitional B cells. In the presence of IL-4, ligands for TLR7/8, TLR9, and NOD1 were effective in driving the in vitro maturation of cord blood transitional B cells into mature, naïve B cells as measured by CD23 expression, ABCB1 transporter activation and upregulation of sIgM and sIgD. In addition, several stimulation conditions, including TLR9 ligand alone, favored an expansion of CD27⁺ IgM memory B cells. Transitional B cells stimulated with TLR7/8 ligand + IL-4 or TLR9 ligand, with or without IL-4, induced a significant subpopulation of CD23⁺CD27⁺ B cells expressing high levels of sIgM and sIgD, a minor B cell subpopulation found in human peripheral blood. These studies illustrate the heterogeneity of the B cell populations induced by cytokine and PRR ligand stimulation. A comparison of transitional and mature, naïve B cells transcriptomes to identify novel genes involved in B cell maturation revealed that mature, naïve B cells were less transcriptionally active than transitional B cells. Nevertheless, a subset of differentially expressed genes in mature, naïve B cells was identified including genes associated with the IL-4 signaling pathway, PI3K signaling in B lymphocytes, the NF-κB signaling pathway, and the TNFR superfamily. When transitional B cells were stimulated in vitro with IL-4 and PRR ligands, gene expression was found to be dependent on the nature of the stimulants, suggesting that exposure to these stimulants may alter the developmental fate of transitional B cells. The influence of IL-4 and PRR signaling on transitional B cell maturation illustrates the potential synergy that may be achieved when certain PRR ligands are incorporated as adjuvants in vaccine formulations and presented to developing B cells in the context of an inflammatory cytokine environment. These studies demonstrate the potential of the PRR ligands to drive transitional B cell differentiation in the periphery during infection or vaccination independently of antigen mediated BCR signaling.

The role of B cells in cancer development

B cells play a critical role in adaptive immune responses mainly due to antigen presentation and antibody production. Studies about the tumor-infiltrating immune cells so far demonstrated that the function of B cells in tumor immunity is quite different among various tumor types. The antigen presentation of B cells is mainly anti-tumoral, while the role of antibody production is controversial. Moreover, the immunosuppressive regulatory B cells are detrimental to anti-tumor immunity via the secretion of various anti-inflammatory cytokines. This review briefly summarizes the different roles of B cells classified by the primary function of B cells, antigen presentation, antibody production, and immunity regulation. Further, it discusses the potential therapeutic target of B cells in tumor immunity.

Interplay of Environmental, Individual and Genetic Factors in Rheumatoid Arthritis Provocation

In this review, we explore systemization of knowledge about the triggering effects of non-genetic factors in pathogenic mechanisms that contribute to the development of rheumatoid arthritis (RA). Possible mechanisms involving environmental and individual factors in RA pathogenesis were analyzed, namely, infections, mental stress, sleep deprivation ecology, age, perinatal and gender factors, eating habits, obesity and smoking. The non-genetic factors modulate basic processes in the body with the impact of these factors being non-specific, but these common challenges may be decisive for advancement of the disease in the predisposed body at risk for RA. The provocation of this particular disease is associated with the presence of congenital loci minoris resistentia. The more frequent non-genetic factors form tangles of interdependent relationships and, thereby, several interdependent external factors hit one vulnerable basic process at once, either provoking or reinforcing each other. Understanding the specific mechanisms by which environmental and individual factors impact an individual under RA risk in the preclinical stages can contribute to early disease diagnosis and, if the factor is modifiable, might be useful for the prevention or delay of its development.

Regulatory B cell repertoire defects predispose lung cancer patients to immune-related toxicity following checkpoint blockade

Checkpoint blockade with Pembrolizumab, has demonstrated durable clinical responses in advanced non-small cell lung cancer, however, treatment is offset by the development of high-grade immune related adverse events (irAEs) in some patients. Here, we show that in these patients a deficient Breg checkpoint fails to limit self-reactive T cell enhanced activity and auto-antibody formation enabled by PD-1/PD-L1 blockade, leading to severe auto-inflammatory sequelae. Principally a failure of IL-10 producing regulatory B cells as demonstrated through functional ex vivo assays and deep phenotyping mass cytometric analysis, is a major and significant finding in patients who develop high-grade irAEs when undergoing treatment with anti-PD1/PD-L1 checkpoint blockade. There is currently a lack of biomarkers to identify a priori those patients at greatest risk of developing severe auto-inflammatory syndrome. Pre-therapy B cell profiling could provide an important tool to identify lung cancer patients at high risk of developing severe irAEs on checkpoint blockade.

Molecular dynamics simulations reveal the selectivity mechanism of structurally similar agonists to TLR7 and TLR8

TLR7 and TLR8 are key members of the Toll-like receptor family, playing crucial roles in the signaling pathways of innate immunity, and thus become attractive therapeutic targets of many diseases including infections and cancer. Although TLR7 and TLR8 show a high degree of sequence homology, their biological response to small molecule binding is very different. Aiming to understand the mechanism of selective profiles of small molecule modulators against TLR7 and TLR8, we carried out molecular dynamic simulations on three imidazoquinoline derivatives bound to the receptors separately. They are Resiquimod (R), Hybrid-2 (H), and Gardiquimod (G), selective agonists of TLR7 and TLR8. Our MD trajectories indicated that in the complex of TLR7-R and TLR7-G, the two chains forming the TLR7 dimer tended to remain “open” conformation, while the rest systems maintained in the closed format. The agonists R, H, and G developed conformational deviation mainly on the aliphatic tail. Furthermore, we attempted to quantify the selectivity between TLR7 and TLR8 by binding free energies via MM-GBSA method. It showed that the three selected modulators were more favorable for TLR7 than TLR8, and the ranking from the strongest to the weakest was H, R and G, aligning well with experimental data. In the TLR7, the flexible and hydrophobic aliphatic side chain of H has stronger van der Waals interactions with V381 and F351 but only pick up interaction with one amino acid residue i.e. Y353 of TLR8. Unsurprisingly, the positively charged side chain of G has less favorable interaction with I585 of TLR7 and V573 of TLR8 explaining G is weak agonist of both TLR7 and TLR8. All three imidazoquinoline derivatives can form stable hydrogen bonds with D555 of TLR7 and the corresponding D543 of TLR8. In brief, the set of total 400ns MD studies sheds light on the potential selectivity mechanisms of agonists towards TLR7 and TLR8, indicating the van der Waals interaction as the driving force for the agonists binding, thus provides us insights for designing more potent and selective modulators to cooperate with the hydrophobic nature of the binding pocket.

Your Regulatory T Cells Are What You Eat: How Diet and Gut Microbiota Affect Regulatory T Cell Development

Modern industrial practices have transformed the human diet over the last century, increasing the consumption of processed foods. Dietary imbalance of macro- and micro-nutrients and excessive caloric intake represent significant risk factors for various inflammatory disorders. Increased ingestion of food additives, residual contaminants from agricultural practices, food processing, and packaging can also contribute deleteriously to disease development. One common hallmark of inflammatory disorders, such as autoimmunity and allergies, is the defect in anti-inflammatory regulatory T cell (Treg) development and/or function. Treg represent a highly heterogeneous population of immunosuppressive immune cells contributing to peripheral tolerance. Tregs either develop in the thymus from autoreactive thymocytes, or in the periphery, from naïve CD4⁺ T cells, in response to environmental antigens and cues. Accumulating evidence demonstrates that various dietary factors can directly regulate Treg development. These dietary factors can also indirectly modulate Treg differentiation by altering the gut microbiota composition and thus the production of bacterial metabolites. This review provides an overview of Treg ontogeny, both thymic and peripherally differentiated, and highlights how diet and gut microbiota can regulate Treg development and function.

Emerging role of RNA sensors in tumor microenvironment and immunotherapy

RNA sensors detect foreign and endogenous RNAs to protect the host by initiating innate and adaptive immune response. In tumor microenvironment (TME), activation of RNA sensors induces tumor-inhibitory cytotoxic T lymphocyte responses and inhibits the activity of immunosuppressive cells though stimulating type I IFN signaling pathway. These characteristics allow RNA sensors to be prospective targets in tumor immunotherapy. Therefore, a comprehensive understanding of the roles of RNA sensors in TME could provide new insight into the antitumor immunotherapy. Moreover, RNA sensors could be prominent triggering targets to synergize with immunotherapies. In this review, we highlight the diverse mechanisms of RNA sensors in cancer immunity and their emerging contributions in cancer immunotherapy, including monotherapy with RNA sensor agonists, as well as combination with chemotherapy, radiotherapy, immune checkpoint blockade or cancer vaccine.

Characterization of Definitive Regulatory B Cell Subsets by Cell Surface Phenotype, Function and Context

Regulatory B cell or “Breg” is a broad term that represents the anti-inflammatory activity of B cells, but does not describe their individual phenotypes, specific mechanisms of regulation or relevant disease contexts. Thus, given the variety of B cell regulatory mechanisms reported in human disease and their animal models, a more thorough and comprehensive identification strategy is needed for tracking and comparing B cell subsets between research groups and in clinical settings. This review summarizes the discovery process and mechanism of action for well-defined regulatory B cell subsets with an emphasis on the mouse model of multiple sclerosis experimental autoimmune encephalomyelitis. We discuss the importance of conducting thorough B cell phenotyping along with mechanistic studies prior to defining a particular subset of B cells as Breg. Since virtually all B cell subsets can exert regulatory activity, it is timely for their definitive identification across studies.

Mesenchymal Stem Cell-Derived Exosomes Attenuate TLR7-Mediated Mast Cell Activation

BACKGROUND

Mast cells are immune sentinels in the skin that respond to a wide range of pathological and environmental stimuli; they owe their function to the expression of Toll-like receptors (TLRs). We previously found that tonsil-derived mesenchymal stem cells (T-MSCs) were able to effectively attenuate TLR7-mediated skin inflammation in mice, which was accompanied by an increase in mast cell number. The present study investigated whether T-MSC extracellular vesicles, such as exosomes, are able to regulate mast cell activation in response to TLR7 stimulation.

METHODS

The HMC-1 human mast cell line was treated with a TLR7 agonist in the presence or absence of T-MSC exosomes, and the levels of expressed inflammatory cytokines were assessed. Additionally, mice were repeatedly injected with a TLR7 agonist with or without interval treatments with T-MSC exosomes and assessed dermal distribution of mast cells and related immune cells.

RESULTS

We showed that T-MSC exosomes containing microRNAs that target inflammatory cytokines significantly reduced the expression of inflammatory cytokines in TLR7 agonist-treated HMC-1 cells. In addition, T-MSC exosomes inhibited the increase in the number of both dermal mast cells and CD14-positive cells in TLR7 agonist-treated mice.

CONCLUSION

Our data suggest that T-MSC exosomes have regulatory effects on mast cell activation under inflammatory conditions, including TLR7 stimulation.

B cells imprint adoptively transferred CD8+ T cells with enhanced tumor immunity

BACKGROUND

Adoptive T cell transfer (ACT) therapy improves outcomes in patients with advanced malignancies, yet many individuals relapse due to the infusion of T cells with poor function or persistence. Toll-like receptor (TLR) agonists can invigorate antitumor T cell responses when administered directly to patients, but these responses often coincide with toxicities. We posited that TLR agonists could be repurposed ex vivo to condition T cells with remarkable potency in vivo, circumventing TLR-related toxicity.

METHODS

In this study we investigated how tumor-specific murine CD8+ T cells and human tumor infiltrating lymphocytes (TILs) are impacted when expanded ex vivo with the TLR9 agonist CpG.

RESULTS

Herein we reveal a new way to reverse the tolerant state of adoptively transferred CD8+ T cells against tumors using TLR-activated B cells. We repurposed the TLR9 agonist, CpG, commonly used in the clinic, to bolster T cell-B cell interactions during expansion for ACT. T cells expanded ex vivo from a CpG-treated culture demonstrated potent antitumor efficacy and prolonged persistence in vivo. This antitumor efficacy was accomplished without in vivo administration of TLR agonists or other adjuvants of high-dose interleukin (IL)-2 or vaccination, which are classically required for effective ACT therapy. CpG-conditioned CD8+ T cells acquired a unique proteomic signature hallmarked by an IL-2RαhighICOShighCD39low phenotype and an altered metabolic profile, all reliant on B cells transiently present in the culture. Likewise, human TILs benefitted from expansion with CpG ex vivo, as they also possessed the IL-2RαhighICOShighCD39low phenotype. CpG fostered the expansion of potent CD8+ T cells with the signature phenotype and antitumor ability via empowering a direct B-T cell interaction. Isolated B cells also imparted T cells with the CpG-associated phenotype and improved tumor immunity without the aid of additional antigen-presenting cells or other immune cells in the culture.

CONCLUSIONS

Our results demonstrate a novel way to use TLR agonists to improve immunotherapy and reveal a vital role for B cells in the generation of potent CD8+ T cell-based therapies. Our findings have immediate implications in the clinical treatment of advanced solid tumors.

Immunological Perspective: Helicobacter pylori Infection and Gastritis

Helicobacter pylori is a spiral-shaped gram-negative bacterium. Its infection is mainly transmitted via oral-oral and fecal-oral routes usually during early childhood. It can achieve persistent colonization by manipulating the host immune responses, which also causes mucosal damage and inflammation. H. pylori gastritis is an infectious disease and results in chronic gastritis of different severity in near all patients with infection. It may develop from acute/chronic inflammation, chronic atrophic gastritis, intestinal metaplasia, dysplasia, and intraepithelial neoplasia, eventually to gastric cancer. This review attempts to cover recent studies which provide important insights into how H. pylori causes chronic inflammation and what the characteristic is, which will immunologically explain H. pylori gastritis.

Role of toll-like receptor 7/8 pathways in regulation of interferon response and inflammatory mediators during SARS-CoV2 infection and potential therapeutic options

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) is the causative agent of Corona Virus Disease 2019 (COVID-19). Lower production of type I and III interferons and higher levels of inflammatory mediators upon SARS-CoV2 infection contribute to COVID-19 pathogenesis. Optimal interferon production and controlled inflammation are essential to limit COVID-19 pathogenesis. However, the aggravated inflammatory response observed in COVID-19 patients causes severe damage to the host and frequently advances to acute respiratory distress syndrome (ARDS). Toll-like receptor 7 and 8 (TLR7/8) signaling pathways play a central role in regulating induction of interferons (IFNs) and inflammatory mediators in dendritic cells. Controlled inflammation is possible through regulation of TLR mediated response without influencing interferon production to reduce COVID-19 pathogenesis. This review focuses on inflammatory mediators that contribute to pathogenic effects and the role of TLR pathways in the induction of interferon and inflammatory mediators and their contribution to COVID-19 pathogenesis. We conclude that potential TLR7/8 agonists inducing antiviral interferon response and controlling inflammation are important therapeutic options to effectively eliminate SARS-CoV2 induced pathogenesis. Ongoing and future studies may provide additional evidence on their safety and efficacy to treat COVID-19 pathogenesis.

Physiologically relevant aspirin concentrations trigger immunostimulatory cytokine production by human leukocytes

Acetylsalicylic acid is a globally used non-steroidal anti-inflammatory drug (NSAID) with diverse pharmacological properties, although its mechanism of immune regulation during inflammation (especially at in vivo relevant doses) remains largely speculative. Given the increase in clinical perspective of Acetylsalicylic acid in various diseases and cancer prevention, this study aimed to investigate the immunomodulatory role of physiological Acetylsalicylic acid concentrations (0.005, 0.02 and 0.2 mg/ml) in a human whole blood of infection-induced inflammation. We describe a simple, highly reliable whole blood assay using an array of toll-like receptor (TLR) ligands 1–9 in order to systematically explore the immunomodulatory activity of Acetylsalicylic acid plasma concentrations in physiologically relevant conditions. Release of inflammatory cytokines and production of prostaglandin E₂ (PGE₂) were determined directly in plasma supernatant. Experiments demonstrate for the first time that plasma concentrations of Acetylsalicylic acid significantly increased TLR ligand-triggered IL-1β, IL-10, and IL-6 production in a dose-dependent manner. In contrast, indomethacin did not exhibit this capacity, whereas cyclooxygenase (COX)-2 selective NSAID, celecoxib, induced a similar pattern like Acetylsalicylic acid, suggesting a possible relevance of COX-2. Accordingly, we found that exogenous addition of COX downstream product, PGE₂, attenuates the TLR ligand-mediated cytokine secretion by augmenting production of anti-inflammatory cytokines and inhibiting release of pro-inflammatory cytokines. Low PGE₂ levels were at least involved in the enhanced IL-1β production by Acetylsalicylic acid.

Microbiota-Driven Activation of Intrahepatic B Cells Aggravates NASH Through Innate and Adaptive Signaling

BACKGROUND AND AIMS

Nonalcoholic steatohepatitis is rapidly becoming the leading cause of liver failure and indication for liver transplantation. Hepatic inflammation is a key feature of NASH but the immune pathways involved in this process are poorly understood. B lymphocytes are cells of the adaptive immune system that are critical regulators of immune responses. However, the role of B cells in the pathogenesis of NASH and the potential mechanisms leading to their activation in the liver are unclear.

APPROACH AND RESULTS

In this study, we report that NASH livers accumulate B cells with elevated pro-inflammatory cytokine secretion and antigen-presentation ability. Single-cell and bulk RNA sequencing of intrahepatic B cells from mice with NASH unveiled a transcriptional landscape that reflects their pro-inflammatory function. Accordingly, B-cell deficiency ameliorated NASH progression, and adoptively transferring B cells from NASH livers recapitulates the disease. Mechanistically, B-cell activation during NASH involves signaling through the innate adaptor myeloid differentiation primary response protein 88 (MyD88) as B cell-specific deletion of MyD88 reduced hepatic T cell-mediated inflammation and fibrosis, but not steatosis. In addition, activation of intrahepatic B cells implicates B cell-receptor signaling, delineating a synergy between innate and adaptive mechanisms of antigen recognition. Furthermore, fecal microbiota transplantation of human NAFLD gut microbiotas into recipient mice promoted the progression of NASH by increasing the accumulation and activation of intrahepatic B cells, suggesting that gut microbial factors drive the pathogenic function of B cells during NASH.

CONCLUSION

Our findings reveal that a gut microbiota-driven activation of intrahepatic B cells leads to hepatic inflammation and fibrosis during the progression of NASH through innate and adaptive immune mechanisms.

Feeding olive flounder (Paralichthys olivaceus) with Lactococcus lactis BFE920 expressing the fusion antigen of Vibrio OmpK and FlaB provides protection against multiple Vibrio pathogens: A universal vaccine effect

Vibriosis, an illness caused by the Vibrio bacteria species, results in significant economic loss in olive flounder farms. Here we present a novel anti-Vibrio feed vaccine protecting multiple strains of Vibrio pathogens, a universal vaccine effect. The vaccine was generated by engineering Lactococcus lactis BFE920 to express the fusion antigens of Vibrio outer membrane protein K (OmpK) and flagellin B subunit (FlaB). These antigen genes are highly conserved among Vibrio species. Olive flounder (7.1 ± 0.8 g and 140 ± 10 g) were fed the vaccine adsorbed to a regular feed (1 × 10⁷ CFU/g) for one week with a 1-week interval, repeating three times (a triple boost). The vaccinated fish increased the significant levels of antigen-specific antibodies, T cell numbers (CD4-1, CD4-2, and CD8α), cytokine production (T-bet and IFN-γ), and innate immune responses (TLR5M, IL-1β, and IL-12p40). Also, the survival rates of adult and juvenile fish fed the vaccine were significantly elevated when challenged with V. anguillarum, V. alginolyticus, and V. harveyi. In addition, weight gain rate and feed conversion ratio were improved in vaccinated fish. The feed vaccine protected multiple Vibrio pathogens, a universal vaccine effect, by activating innate and adaptive immune responses. This oral vaccine may be developed as an anti-Vibrio vaccine to protect against a broad spectrum of Vibrio pathogens.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Gut-derived acetate promotes B10 cells with antiinflammatory effects

Autoimmune diseases are characterized by a breakdown of immune tolerance partly due to environmental factors. The short-chain fatty acid acetate, derived mostly from gut microbial fermentation of dietary fiber, promotes antiinflammatory Tregs and protects mice from type 1 diabetes, colitis, and allergies. Here, we show that the effects of acetate extend to another important immune subset involved in tolerance, the IL-10-producing regulatory B cells (B10 cells). Acetate directly promoted B10 cell differentiation from mouse B1a cells both in vivo and in vitro. These effects were linked to metabolic changes through the increased production of acetyl-coenzyme A, which fueled the TCA cycle and promoted posttranslational lysine acetylation. Acetate also promoted B10 cells from human blood cells through similar mechanisms. Finally, we identified that dietary fiber supplementation in healthy individuals was associated with increased blood-derived B10 cells. Direct delivery of acetate or indirect delivery via diets or bacteria that produce acetate might be a promising approach to restore B10 cells in noncommunicable diseases.

If small molecules immunotherapy comes, can the prime be far behind?

Anti-cancer immunotherapy, which includes cellular immunotherapy, immune checkpoint inhibitors and cancer vaccines, has transformed the treatment strategies of several malignancies in the past decades. Immune checkpoints blockade (ICB) is the most commonly tested therapy and has the potential to induce a durable immune response in different types of cancers. However, all approved immune checkpoint inhibitors (ICIs) are monoclonal antibodies (mAbs), which are fraught with disadvantages including lack of oral bioavailability, prolonged tissue retention and poor membrane permeability. Therefore, the research focus has shifted to developing small molecule inhibitors to obviate the limitations of mAbs. Given the complexity of the tumor micro-environment (TME), the combination of ICIs with various small molecule agonists/inhibitors are currently being tested in clinical trials to improve treatment outcomes and prevent tumor recurrence. In this review, we have summarized the mechanisms and therapeutic potential of several molecular targets, along with the current status of small molecule inhibitors.

Marginal zone B cells: From housekeeping function to autoimmunity?

Marginal zone (MZ) B cells comprise a subset of innate-like B cells found predominantly in the spleen, but also in lymph nodes and blood. Their principal functions are participation in quick responses to blood-borne pathogens and secretion of natural antibodies. The latter is important for housekeeping functions such as clearance of apoptotic cell debris. MZ B cells have B cell receptors with low poly-/self-reactivity, but they are not pathogenic at steady state. However, if simultaneously stimulated with self-antigen and pathogen- and/or damage-associated molecular patterns (PAMPs/DAMPs), MZ B cells may participate in the initial steps towards breakage of immunological tolerance. This review summarizes what is known about the role of MZ B cells in autoimmunity, both in mouse models and human disease. We cover factors important for shaping the MZ B cell compartment, how the functional properties of MZ B cells may contribute to breaking tolerance, and how MZ B cells are being regulated.

Invariant natural killer T cells balance B cell immunity

Invariant natural killer T (iNKT) cells mediate rapid immune responses which bridge the gap between innate and adaptive responses to pathogens while also providing key regulation to maintain immune homeostasis. Both types of important iNKT immune responses are mediated through interactions with innate and adaptive B cells. As such, iNKT cells sit at the decision-making fulcrum between regulating inflammatory or autoreactive B cells and supporting protective or regulatory B cell populations. iNKT cells interpret the signals in their environment to set the tone for subsequent adaptive responses, with outcomes ranging from getting licensed to maintain homeostasis as an iNKT regulatory cell (iNKT_reg ) or being activated to become an iNKT follicular helper (iNKT_FH ) cell supporting pathogen-specific effector B cells. Here we review iNKT and B cell cooperation across the spectrum of immune outcomes, including during allergy and autoimmune disease, tumor surveillance and immunotherapy, or pathogen defense and vaccine responses. Because of their key role as influencers, iNKT cells provide a valuable target for therapeutic interventions. Understanding the nature of the interactions between iNKT and B cells will enable the development of clinical interventions to strategically target regulatory iNKT and B cell populations or inflammatory ones, depending on the circumstance.

Use of Toll-Like Receptor (TLR) Ligation to Characterize Human Regulatory B-Cells Subsets

Toll-like receptors (TLRs) are pattern recognition receptors (PRRs), which constitute key components in the recognition of pathogens, thereby initiating innate immune responses and promoting adaptive immune responses. In B cells, TLR ligation is important for their activation and, together with CD40, for their differentiation. TLR ligands are also strong promoters of regulatory B (Breg)-cell development, by enhancing the production of IL-10 and their capacity to induce tolerance. In inflammatory diseases, such as autoimmunity or allergies, Breg-cell function is often impaired, while in chronic infections, such as with helminths, or cancer, Breg-cell function is boosted. Following pathogen exposure, B cells can respond directly by producing cytokines and/or IgM (innate response) and develop into various memory B (Bmem)-cell subsets with class-switched immunoglobulin receptors. Depending on the disease state or chronic infection conditions, various Breg subsets can be recognized as well. Currently, a large array of surface markers is known to distinguish between these large range of B-cell subsets. In recent years, the development of mass cytometers and spectral flow cytometry has allowed for high-dimensional detection of up to 48 markers, including both surface and intracellular/intranuclear markers. Therefore, this novel technology is highly suitable to provide a comprehensive overview of Bmem/Breg-cell subsets in different disease states and/or in clinical intervention trials. Here, we provide detailed instructions of the steps necessary to obtain high-quality data for high-dimensional analysis of multiple human Breg-cell subsets using various TLR ligands.

Reading the room: iNKT cells influence B cell responses

Rapid immune responses regulated by invariant Natural Killer T (iNKT) cells bridge the gap between innate and adaptive responses to pathogens, while also providing key regulation to maintain immune homeostasis. iNKT immune protection and immune regulation are both mediated through interactions with innate and adaptive B cell populations that express CD1d. Recent studies have expanded our understanding of the position of iNKT cells at the fulcrum between regulating inflammatory and autoreactive B cells. Environmental signals influence iNKT cells to set the tone for subsequent adaptive responses, ranging from maintaining homeostasis as an iNKT regulatory cell (iNKT_reg) or supporting pathogen-specific effector B cells as an iNKT follicular helper (iNKT_FH). Here we review recent advances in iNKT and B cell cooperation during autoimmunity and sterile inflammation. Understanding the nature of the interactions between iNKT and B cells will enable the development of clinical interventions to strategically target regulatory iNKT and B cell populations or inflammatory ones, across a range of indications.

Endothelin receptors promote schistosomiasis-induced hepatic fibrosis via splenic B cells

Endothelin receptors (ETRs) are activated by vasoactive peptide endothelins and involved in the pathogenesis of hepatic fibrosis. However, less is known about the role of ETRs in Schistosoma (S.) japonicum-induced hepatic fibrosis. Here, we show that the expression of ETRs is markedly enhanced in the liver and spleen tissues of patients with schistosome-induced fibrosis, as well as in murine models. Additional analyses have indicated that the expression levels of ETRs in schistosomiasis patients are highly correlated with the portal vein and spleen thickness diameter, both of which represent the severity of fibrosis. Splenomegaly is a characteristic symptom of schistosome infection, and splenic abnormality may promote the progression of hepatic fibrosis. We further demonstrate that elevated levels of ETRs are predominantly expressed on splenic B cells in spleen tissues during infection. Importantly, using a well-studied model of human schistosomiasis, we demonstrate that endothelin receptor antagonists can partially reverse schistosome-induced hepatic fibrosis by suppressing the activation of splenic B cells characterized by interleukin-10 (IL-10) secretion and regulatory T (Treg) cell-inducing capacity. Our study provides insights into the mechanisms by which ETRs regulate schistosomiasis hepatic fibrosis and highlights the potential of endothelin receptor antagonist as a therapeutic intervention for fibrotic diseases.

Schistosomiasis is a serious but neglected tropical infectious disease. which can lead to hepatic fibrosis and death. To date, there are still no approved antifibrotic therapies. Hepatic fibrosis results in portal hypertension and variceal bleeding, and it is the primary cause of mortality from schistosomiasis. Splenomegaly and hypersplenism can manifest following the development of portal hypertension. Accumulating evidence suggests that the spleen plays a critical role in the development of hepatic fibrosis. In this study, using Schistosoma (S.) japonicum in both humans and mice, we show that progressive hepatic schistosomiasis caused elevation of endothelin receptors (ETRs) both in liver and spleen tissues, and the endothelin receptor-producing cells are mainly located in splenic B cells. More importantly, we demonstrate that endothelin receptor antagonists can partially reverse schistosome-induced hepatic fibrosis by suppressing the activation of splenic B cells during infection. Thus, our study highlights the potential of endothelin receptor antagonist as a therapeutic intervention for schistosomiasis and other fibrotic diseases.

Harnessing the Complete Repertoire of Conventional Dendritic Cell Functions for Cancer Immunotherapy

The onset of checkpoint inhibition revolutionized the treatment of cancer. However, studies from the last decade suggested that the sole enhancement of T cell functionality might not suffice to fight malignancies in all individuals. Dendritic cells (DCs) are not only part of the innate immune system, but also generals of adaptive immunity and they orchestrate the de novo induction of tolerogenic and immunogenic T cell responses. Thus, combinatorial approaches addressing DCs and T cells in parallel represent an attractive strategy to achieve higher response rates across patients. However, this requires profound knowledge about the dynamic interplay of DCs, T cells, other immune and tumor cells. Here, we summarize the DC subsets present in mice and men and highlight conserved and divergent characteristics between different subsets and species. Thereby, we supply a resource of the molecular players involved in key functional features of DCs ranging from their sentinel function, the translation of the sensed environment at the DC:T cell interface to the resulting specialized T cell effector modules, as well as the influence of the tumor microenvironment on the DC function. As of today, mostly monocyte derived dendritic cells (moDCs) are used in autologous cell therapies after tumor antigen loading. While showing encouraging results in a fraction of patients, the overall clinical response rate is still not optimal. By disentangling the general aspects of DC biology, we provide rationales for the design of next generation DC vaccines enabling to exploit and manipulate the described pathways for the purpose of cancer immunotherapy in vivo. Finally, we discuss how DC-based vaccines might synergize with checkpoint inhibition in the treatment of malignant diseases.

Discovery and Function of B-Cell IgD Low (BDL) B Cells in Immune Tolerance

It is now appreciated that in addition to their role in humoral immunity, B cells also exert regulatory mechanisms that lead to attenuation of inflammatory responses. The concept of B-cell regulation became well recognized when mice deficient in B cells due to genetic disruption were shown to be refractory to recovery from the signs of experimental autoimmune encephalomyelitis (EAE), the mouse model of multiple sclerosis. This seminal study spurred the search for B-cell regulatory phenotypes and mechanisms of action. Our approach was to utilize differential B-cell depletion with anti-CD20 to retain B cells whose presence were required to achieve EAE recovery. Utilizing flow cytometry, adoptive cell therapy and genetic approaches, we discovered a new B-cell subset that, upon adoptive transfer into B cell-deficient mice, was sufficient to promote EAE recovery. This B-cell subset is IgM⁺, but due to low/negative IgD cell surface expression, it was named B-cell IgD low (BD_L). Mechanistically, we found that in the absence of BD_L, the absolute cell number of CD4⁺Foxp3⁺ T regulatory cells (Treg), essential for immune tolerance, was significantly reduced. Furthermore, we found that BD_L expression of glucocorticoid-induced tumor necrosis factor ligand (GITRL) was essential for induction of Treg proliferation and maintenance of their homeostasis. Thus, we have identified a new B-cell subset that is critical for immunological tolerance through interactions with Treg.

Antibody Production in Murine Polymicrobial Sepsis-Kinetics and Key Players

Although antigen-specific priming of antibody responses is impaired during sepsis, there is nevertheless a strong increase in IgM and IgG serum concentrations. Using colon ascendens stent peritonitis (CASP), a mouse model of polymicrobial abdominal sepsis, we observed substantial increases in IgM as well as IgG of all subclasses, starting at day 3 and peaking 2 weeks after sepsis induction. The dominant source of antibody-secreting cells was by far the spleen, with a minor contribution of the mesenteric lymph nodes. Remarkably, sepsis induction in splenectomized mice did not change the dynamics of the serum IgM/IgG reaction, indicating that the marginal zone B cells, which almost exclusively reside in the spleen, are dispensable in such a setting. Hence, in systemic bacterial infection, the function of the spleen as dominant niche of antibody-producing cells can be compensated by extra-splenic B cell populations as well as other lymphoid organs. Depletion of CD4+ T cells did not affect the IgM response, while it impaired IgG generation of all subclasses with the exception of IgG3. Taken together, our data demonstrate that the robust class-switched antibody response in sepsis encompasses both T cell-dependent and -independent components.

P53: A Guardian of Immunity Becomes Its Saboteur through Mutation

Awareness of the importance of immunity in controlling cancer development triggered research into the impact of its key oncogenic drivers on the immune response, as well as their value as targets for immunotherapy. At the heart of tumour suppression is p53, which was discovered in the context of viral infection and now emerges as a significant player in normal and cancer immunity. Wild-type p53 (wt p53) plays fundamental roles in cancer immunity and inflammation. Mutations in p53 not only cripple wt p53 immune functions but also sinisterly subvert the immune function through its neomorphic gain-of-functions (GOFs). The prevalence of mutant p53 across different types of human cancers, which are associated with inflammatory and immune dysfunction, further implicates mutant p53 in modulating cancer immunity, thereby promoting tumorigenesis, metastasis and invasion. In this review, we discuss several mutant p53 immune GOFs in the context of the established roles of wt p53 in regulating and responding to tumour-associated inflammation, and regulating innate and adaptive immunity. We discuss the capacity of mutant p53 to alter the tumour milieu to support immune dysfunction, modulate toll-like receptor (TLR) signalling pathways to disrupt innate immunity and subvert cell-mediated immunity in favour of immune privilege and survival. Furthermore, we expose the potential and challenges associated with mutant p53 as a cancer immunotherapy target and underscore existing therapies that may benefit from inquiry into cancer p53 status.

Toll-Like Receptor Signaling and Immune Regulatory Lymphocytes in Periodontal Disease

Periodontitis is known to be initiated by periodontal microbiota derived from biofilm formation. The microbial dysbiotic changes in the biofilm trigger the host immune and inflammatory responses that can be both beneficial for the protection of the host from infection, and detrimental to the host, causing tissue destruction. During this process, recognition of Pathogen-Associated Molecular Patterns (PAMPs) by the host Pattern Recognition Receptors (PRRs) such as Toll-like receptors (TLRs) play an essential role in the host–microbe interaction and the subsequent innate as well as adaptive responses. If persistent, the adverse interaction triggered by the host immune response to the microorganisms associated with periodontal biofilms is a direct cause of periodontal inflammation and bone loss. A large number of T and B lymphocytes are infiltrated in the diseased gingival tissues, which can secrete inflammatory mediators and activate the osteolytic pathways, promoting periodontal inflammation and bone resorption. On the other hand, there is evidence showing that immune regulatory T and B cells are present in the diseased tissue and can be induced for the enhancement of their anti-inflammatory effects. Changes and distribution of the T/B lymphocytes phenotype seem to be a key determinant of the periodontal disease outcome, as the functional activities of these cells not only shape up the overall immune response pattern, but may directly regulate the osteoimmunological balance. Therefore, interventional strategies targeting TLR signaling and immune regulatory T/B cells may be a promising approach to rebalance the immune response and alleviate bone loss in periodontal disease. In this review, we will examine the etiological role of TLR signaling and immune cell osteoclastogenic activity in the pathogenesis of periodontitis. More importantly, the protective effects of immune regulatory lymphocytes, particularly the activation and functional role of IL-10 expressing regulatory B cells, will be discussed.

Targeted Knockout of MDA5 and TLR3 in the DF-1 Chicken Fibroblast Cell Line Impairs Innate Immune Response Against RNA Ligands

The innate immune system, which senses invading pathogens, plays a critical role as the first line of host defense. After recognition of foreign RNA ligands (e.g., RNA viruses), host cells generate an innate immune or antiviral response via the interferon-mediated signaling pathway. Retinoic acid-inducible gene I (RIG-1) acts as a major sensor that recognizes a broad range of RNA ligands in mammals; however, chickens lack a RIG-1 homolog, meaning that RNA ligands should be recognized by other cellular sensors such as melanoma differentiation-associated protein 5 (MDA5) and toll-like receptors (TLRs). However, it is unclear which of these cellular sensors compensates for the loss of RIG-1 to act as the major sensor for RNA ligands. Here, we show that chicken MDA5 (cMDA5), rather than chicken TLRs (cTLRs), plays a pivotal role in the recognition of RNA ligands, including poly I:C and influenza virus. First, we used a knockdown approach to show that both cMDA5 and cTLR3 play roles in inducing interferon-mediated innate immune responses against RNA ligands in chicken DF-1 cells. Furthermore, targeted knockout of cMDA5 or cTLR3 in chicken DF-1 cells revealed that loss of cMDA5 impaired the innate immune responses against RNA ligands; however, the responses against RNA ligands were retained after loss of cTLR3. In addition, double knockout of cMDA5 and cTLR3 in chicken DF-1 cells abolished the innate immune responses against RNA ligands, suggesting that cMDA5 is the major sensor whereas cTLR3 is a secondary sensor. Taken together, these findings provide an understanding of the functional role of cMDA5 in the recognition of RNA ligands in chicken DF-1 cells and may facilitate the development of an innate immune-deficient cell line or chicken model.

Agonist and antagonist ligands of toll-like receptors 7 and 8: Ingenious tools for therapeutic purposes

The discovery of the TLRs family and more precisely its functions opened a variety of gates to modulate immunological host responses. TLRs 7/8 are located in the endosomal compartment and activate a specific signaling pathway in a MyD88-dependant manner. According to their involvement into various autoimmune, inflammatory and malignant diseases, researchers have designed diverse TLRs 7/8 ligands able to boost or block the inherent signal transduction. These modulators are often small synthetic compounds and most act as agonists and to a much lesser extent as antagonists. Some of them have reached preclinical and clinical trials, and only one has been approved by the FDA and EMA, imiquimod. The key to the success of these modulators probably lies in their combination with other therapies as recently demonstrated. We gather in this review more than 360 scientific publications, reviews and patents, relating the extensive work carried out by researchers on the design of TLRs 7/8 modulators, which are classified firstly by their biological activities (agonist or antagonist) and then by their chemical structures, which total syntheses are not discussed here. This review also reports about 90 clinical cases, thereby showing the biological interest of these modulators in multiple pathologies.

Monophosphoryl-Lipid A (MPLA) is an Efficacious Adjuvant for Inactivated Rabies Vaccines

Rabies, as one of the most threatening zoonoses in the world, causes a fatal central nervous system (CNS) disease. So far, vaccination with rabies vaccines has been the most effective measure to prevent and control this disease. At present, inactivated rabies vaccines are widely used in humans and domestic animals. However, humoral immune responses induced by inactivated rabies vaccines are relatively low and multiple shots are required to achieve protective immunity. Supplementation with an adjuvant is a practical way to improve the immunogenicity of inactivated rabies vaccines. In this study, we found that monophosphoryl-lipid A (MPLA), a well-known TLR4 agonist, could significantly promote the maturation of bone marrow-derived dendritic cells (BMDC) through a TLR4-dependent pathway in vitro and the maturation of conventional DCs (cDCs) in vivo. We also found that MPLA, serving as an adjuvant for inactivated rabies vaccines, could significantly facilitate the generation of T follicular helper (Tfh) cells, germinal center (GC) B cells, and plasma cells (PCs), consequently enhancing the production of RABV-specific total-IgG, IgG2a, IgG2b, and the virus-neutralizing antibodies (VNAs). Furthermore, MPLA could increase the survival ratio of mice challenged with virulent RABV. In conclusion, our results demonstrate that MPLA serving as an adjuvant enhances the intensity of humoral immune responses by activating the cDC-Tfh-GC B axis. Our findings will contribute to the improvement of the efficiency of traditional rabies vaccines.

IL-10-Producing Potential Treg Precursor in Placenta

The maternal immune system needs to be tolerant of allogeneic fetal tissue for reproductive success. The regulatory immune cell network plays an essential role in maintaining maternal tolerance to the fetus. We herein demonstrate in a green fluorescent protein (GFP)/IL-10 reporter mouse system that unique IL-10-expressing cells exist presumably in chorionic villi within the placenta. Flow cytometric analysis revealed that these IL-10- expressing cells exhibit a unique CD19 negative, CD3 negative, and B220 positive phenotype. Interestingly, these cells were enriched during in vitro culture, but well-known stimuli for T cells and B cells failed to enhance their growth, suggesting that the CD19^- CD3^- B220⁺ cells were self renewing. Unexpectedly, in an adoptive cell trans fer experiment, IL-10 production was detected in Sca-1⁺ CD4⁺ CD25⁺ regulatory T cells (Treg). To our knowledge, this is the first report to identify IL-10-producing CD19^- CD3^- B220⁺ cells in the fetus. These cells may rep resent a potential progenitor of Sca-1⁺ Treg or pluripotent precursor cells for immune tolerance.

Synergistic effects triggered by simultaneous Toll-like receptor-2 and -3 activation in human periodontal ligament stem cells

Background

Although periodontitis is associated with disruption of the host‐microbial homeostasis, viruses are currently discussed to influence disease progression. Viral pathogens are recognized by Toll‐like receptor (TLR)‐3, which engages a different signaling pathway than other TLRs. This study aimed to investigate the effect of TLR‐3 agonist polyinosinic:polycytidylic acid (Poly I:C) on the expression of inflammatory markers and bone metabolism proteins by human periodontal ligament stem cells (hPDLSCs) compared with TLR‐2 agonist Pam3CSK4, which mimics the effect of bacterial lipoproteins. To assess potential combined effects of bacterial and viral infections, hPDLSCs response to simultaneous TLR‐2 and TLR‐3 activation was investigated.

Methods

HPDLSCs were stimulated with Poly I:C (0.0001‐1 µg/mL), Pam3CSK4 (1 µg/mL), and their combinations for 24 hours. Gene expression and protein levels of interleukin (IL)‐6, IL‐8, monocyte chemoattractant protein (MCP)‐1, and osteoprotegerin (OPG) were measured with qPCR and ELISA.

Results

Production of IL‐6, IL‐8, MCP‐1, and OPG was significantly increased by Poly I:C or Pam3CSK4 to a similar extent. The levels of all inflammatory mediators induced by simultaneous stimulation with Poly I:C and Pam3CSK4 were significantly higher compared with single stimuli as well as to their summed response. Gene expression and protein levels of OPG were enhanced by Poly I:C, but by lesser extent than by Pam3CSK4. OPG levels upon simultaneous stimulation with Pam3CSK4 and Poly I:C were significantly lower compared with Pam3CSK4 stimulation alone.

Conclusions

Simultaneous TLR‐2 and TLR‐3 activation synergistically triggers IL‐6, IL‐8, and MCP‐1 production, which was not observed for OPG. These findings suggest that TLR‐3 activation by viral infections might promote periodontitis progression.

Expression of Toll-like receptors and costimulatory molecules in splenic B cells in a normal and abortion-prone murine pregnancy model

PROBLEM

The regulatory role of B lymphocytes in the pregnancy-induced maternal immune response is not well recognized. B lymphocytes function as antigen-presenting cells (APCs) and regulate Toll-like receptors and costimulatory molecule expression in response to intrinsic and extrinsic signals. Therefore, the aim of this study was to determine the expression of TLR2, TLR4, TLR9, and MHC class II and the costimulatory molecules CD80, CD86, and CD40 in splenic B cells in a normal and abortion-prone murine pregnancy model.

METHODS OF STUDY

The expression level of these molecules on female splenic B cells was investigated using real-time PCR and flow cytometry. The analysis was performed on the 3rd and 14th day of normal (CBA/JxBALB/c) and abortion-prone (CBA/JxDBA/2J) murine pregnancy.

RESULTS

The expression of Tlr9, Cd86, and H2-Ab1 in splenic B cells on the 3rd day after mating was upregulated, whereas Tlr2 was downregulated in abortion-prone females. On day 14, we observed lower expression levels of Tlr4 and Cd80 and higher expression levels of Cd86 in CBA/J females mated with DBA/2J males. At the protein level, the differences were observed only on day 3 of pregnancy. TLR4 and CD40 molecules were upregulated in splenic B cells, while TLR9 and CD86 were downregulated in abortion-prone mice.

CONCLUSION

Differential expression of TLRs and costimulatory molecules in splenic B cells in abortion-prone and normal pregnancies suggests the involvement of these cells in the regulation of the immune response at the periphery in pregnant females.

TIR-TLR7 as a Molecular Adjuvant: Simultaneous Enhancing Humoral and Cell-Mediated Immune Responses Against Inactivated Infectious Bursal Disease Virus

Despite the robust induction of humoral immune responses, a limitation of many adjuvants is their weak stimulation of cellular immunity. The development of synthetic gene-encoding adjuvants for simultaneous induction of both humoral and cell-mediated immune responses is under study. In this study, we examined the impact of toll/interleukin-1 receptor (TIR) domain of toll-like receptor 7 (TLR7) as molecular adjuvants on potency of inactivated infectious bursal disease (IBD) vaccines. A total of 60 specific pathogen-free week-old chicks were randomized grouped to receive either TIR-TLR7-adjuvanted IBD-inactivated vaccine or inactivated IBD antigen along with an unvaccinated control. Serum antibody titers were measured to estimate the humoral immunity, as well as lymphocyte proliferation activity for cellular immune responses. The protection was estimated after challenge with a very virulent IBD virus (IBDV) strain at 4 weeks postvaccination. The results indicated that one dose of IBD/TIR-TLR7 vaccine induced specific antibody responses, whereas a lower response after administration of inactivated IBD antigen was observed. The stimulation of splenocytes results indicated that the TIR-TLR7 adjuvanted IBD vaccine is capable of modulating cell-mediated immune response in treated chickens. A full protection against IBDV infection was achieved by injection of one dose IBD/TIR-TLR7 vaccine in the challenge trial. This study demonstrated that codelivery of TIR-TLR7 with inactivated IBD antigen resulted in simultaneous enhancing immune responses against IBD.

IL-10-producing B cells are characterized by a specific methylation signature

Among the family of regulatory B cells, the subset able to produce interleukin-10 (IL-10) is the most studied, yet its biology is still a matter of investigation. The DNA methylation profiling of the il-10 gene locus revealed a novel epigenetic signature characterizing murine B cells ready to respond through IL-10 synthesis: a demethylated region located 4.5 kb from the transcription starting site (TSS), that we named early IL10 regulatory region (eIL10rr). This feature allows to distinguish B cells that are immediately prone and developmentally committed to IL-10 production from those that require a persistent stimulation to exert an IL-10-mediated regulatory function. These late IL-10 producers are instead characterized by a delayed IL10 regulatory region (dIL10rr), a partially demethylated DNA portion located 9 kb upstream from the TSS. A demethylated region was also found in human IL-10-producing B cells and, very interestingly, in some B-cell malignancies, such as chronic lymphocytic leukemia and mantle cell lymphoma, characterized by an immunosuppressive microenvironment. Our findings define murine and human regulatory B cells as an epigenetically controlled functional state of mature B cell subsets and open a new perspective on IL-10 regulation in B cells in homeostasis and disease.

Non-Antibody-Secreting Functions of B Cells and Their Contribution to Autoimmune Disease

B cells play multiple important roles in the pathophysiology of autoimmune disease. Beyond producing pathogenic autoantibodies, B cells can act as antigen-presenting cells and producers of cytokines, including both proinflammatory and anti-inflammatory cytokines. Here we review our current understanding of the non-antibody-secreting roles that B cells may play during development of autoimmunity, as learned primarily from reductionist preclinical models. Attention is also given to concepts emerging from clinical studies using B cell depletion therapy, which shed light on the roles of these mechanisms in human autoimmune disease.