Type I Interferons Promote Germinal Centers Through B Cell Intrinsic Signaling and Dendritic Cell Dependent Th1 and Tfh Cell Lineages

Interferon-induced activation of dendritic cells and monocytes by yellow fever vaccination correlates with early antibody responses

Yellow fever vaccination provides long-lasting protection and is a unique model for studying the immune response to an acute RNA virus infection in humans. To elucidate the early innate immune events preceding the rapid generation of protective immunity, we performed transcriptome analysis of human blood dendritic cell (DC) and monocyte subpopulations before and 3, 7, 14, and 28 d after vaccination. We detected temporary upregulation of IFN-stimulated genes (ISG) in all DC and monocyte subsets on days 3 and 7 after vaccination as well as cell type-specific responses and response kinetics. Single-cell RNA sequencing revealed rapid appearance of activated DC and monocyte clusters dominated by ISGs, inflammatory chemokines, and genes involved in antigen processing and presentation. This was confirmed by flow cytometric analysis in a large cohort of vaccinees. We identified SIGLEC1/CD169 upregulation as a sensitive indicator of the transient IFN-induced activation state elicited in DCs and monocytes by YF17D vaccination correlating with early protective IgM antibody responses.

Different responses involving Tfh cells delay parasite-specific antibody production in Trypanosoma cruzi acute experimental models

Introduction

Chagas disease (CD), caused by the parasite Trypanosoma cruzi, affects millions globally. Despite treatment options in the acute phase, most infections progress to a chronic indeterminate form or develop severe cardiac/gastrointestinal complications. Understanding the immune response is crucial for the development of vaccines and more efficient drugs for the disease control.

Methods

This work investigates the immune response to T. cruzi H1 K68 strain infection in female BALB/c and C57BL/6 mice to characterize differences in Tfh and B cell responses that may be involved in the poor parasite-specific antibody production during acute infection. For this, mice were euthanized 14, 28, and 49 days after infection, and splenic T and B cell populations were evaluated by flow cytometry.

Results

BALB/c mice exhibited a strong Th2-biased response with a massive expansion of classic Tfh cells and GC B cells, potentially linked with polyclonal B cell activation and hypergammaglobulinemia, but not with efficient parasite clearance. C57BL/6 mice displayed a Th1-skewed response with a population of "Th1-like Tfh" cells expressing IFN-γ and CXCR5 associated with lower parasite burden and more focused antibody response, including parasitespecific IgG2c during early acute infection.

Discussion

These findings suggest that these mouse models develop different immune responses mediated by Tfh cells, which are crucial for B cell activation and antibody production. The massive expansion of Tfh cells in BALB/c mice might lead to unspecific antibody production due to excessive B cell activation. Conversely, C57BL/6 mice exhibit a "Th1-like Tfh" response lacking classic Tfh cells, potentially explaining their weak parasite-specific antibody production throughout the acute infection. Overall, this study provides for the first time insights into the complex interplay between Tfh cells and antibody production during T. cruzi infection, suggesting potential targets for therapeutic intervention in CD.

Emulsion adjuvant-induced uric acid release modulates optimal immunogenicity by targeting dendritic cells and B cells

Squalene-based emulsion (SE) adjuvants like MF59 and AS03 are used in protein subunit vaccines against influenza virus (e.g., Fluad, Pandemrix, Arepanrix) and SARS-CoV-2 (e.g., Covifenz, SKYCovione). We demonstrate the critical role of uric acid (UA), a damage-associated molecular pattern (DAMP), in triggering immunogenicity by SE adjuvants. In mice, SE adjuvants elevated DAMP levels in draining lymph nodes. Strikingly, inhibition of UA synthesis reduced vaccine-induced innate immunity, subsequently impairing optimal antibody and T cell responses. In vivo treatment with UA crystals elicited partial adjuvant effects. In vitro stimulation with UA crystals augmented the activation of dendritic cells (DCs) and B cells and altered multiple pathways in these cells, including inflammation and antigen presentation in DCs and cell proliferation in B cells. In an influenza vaccine model, UA contributed to protection against influenza viral infection. These results demonstrate the importance of DAMPs, specifically the versatile role of UA in the immunogenicity of SE adjuvants, by regulating DCs and B cells.

Inhibiting Tyrosine Kinase 2 Ameliorates Antiphospholipid Syndrome Nephropathy

Objective: Antiphospholipid antibody syndrome (APS) is an autoimmune disease characterized by the presence of β2-glycoprotein I (β2-GPI)-targeting antiphospholipid antibodies (aPLs) and vascular thrombosis or obstetrical complications. One of its severe manifestations is nephropathy. Methods: To examine the role of type I interferon (IFN) and therapeutic potential of tyrosine kinase 2 (Tyk2) inhibition, we administered BMS-986202, a novel Tyk2 inhibitor, in a mouse model of APS nephropathy. We administered BMS-986202 to BALB/c mice at a dose of 2 mg/kg. Biochemical and histological characteristics of APS nephropathy were then determined. The type I IFN signature in the kidney was also evaluated by real-time polymerase chain reaction (PCR). Results: The Tyk2 inhibitor reversed the elevation of blood urea nitrogen (BUN) and microalbuminuria in the murine model of APS nephropathy. In addition, the Tyk2 inhibitor reversed the pathological vascular changes in the kidney as judged in electron microscopy (EM), and fibrin and C3 deposition as revealed in immunohistochemistry (IHC). An increased expression levels of IFN signature (IFN regulatory factor 7 (IRF7) and Mx1) in the kidneys of APS mice were found. Tyk2 inhibition reversed such an upregulation. Conclusion: Our results demonstrated the key role of type I IFN in the pathogenesis of APS nephropathy. Furthermore, the therapeutic efficacy of Tyk2 inhibition was demonstrated in a murine model of APS nephropathy. Our results could provide a new treatment strategy for this debilitating disease.

Lipid nanoparticles as adjuvant of norovirus VLP vaccine augment cellular and humoral immune responses in a TLR9- and type I IFN-dependent pathway

Norovirus (NoV) virus-like particles (VLPs) adjuvanted with aluminum hydroxide (Alum) are common vaccine candidates in clinical studies. Alum adjuvants usually inefficiently assist recombinant proteins to induce cellular immune responses. Thus, novel adjuvants are required to develop NoV vaccines that could induce both efficient humoral and robust cellular immune responses. Lipid nanoparticles (LNPs) are well-known mRNA delivery vehicles. Increasing evidence suggests that LNPs may have intrinsic adjuvant activity and can be used as adjuvants for recombinant protein vaccines; however, the underlying mechanism remains poorly understood. In this study, we compared the adjuvant effect of LNPs and Alum for a bivalent GI.1/GII.4 NoV VLP vaccine. Compared with Alum, LNP-adjuvanted vaccines induced earlier production of binding, blocking, and neutralizing antibodies and promoted a more balanced IgG2a/IgG1 ratio. It is crucial that LNP-adjuvanted vaccines induced stronger Th1-type cytokine-producing CD4+ T cell and CD8+ T cell responses than Alum. The adjuvant activity of LNPs depended on the ionizable lipid components. Mechanistically, LNPs activated innate immune responses in a type I IFN-dependent manner and were partially dependent on Toll-like receptor (TLR) 9, thus affecting the adaptive immune responses of the vaccine. This conclusion was supported by RNA-seq analysis and in vitro cell experiments and by the deeply blunted T cell responses in IFNαR1-/- mice immunized with LNP-adjuvanted vaccines. This study not only identified LNPs as a high quality adjuvant for NoV VLP vaccines, but also clarified the underlying mechanism of LNPs as a potent immunostimulatory component for improving protein subunit vaccines.IMPORTANCEWith the rapid development of mRNA vaccines, recurrent studies show that lipid nanoparticles (LNPs) have adjuvant activity. However, the mechanism of its adjuvant effect in protein vaccines remains unknown. In this study, we found that the LNP-adjuvanted norovirus bivalent virus-like particle vaccines led to durable antibody responses as well as Th1-type cytokine-producing CD4+ T cell and CD8+ T cell responses, which exceeded the efficiency of the conventional adjuvant aluminum hydroxide. Mechanistically, LNPs activated innate immune responses in a type I IFN-dependent manner and were partially dependent on Toll-like receptor 9, thus affecting the adaptive immune responses of the vaccine. This work unveils that LNPs as a potent immunostimulatory component may be ideal for generating CD8+ T cell and B cell responses for recombinant protein vaccines.

Modulation of antigen delivery and lymph node activation in nonhuman primates by saponin adjuvant saponin/monophosphoryl lipid A nanoparticle

Saponin-based vaccine adjuvants are potent in preclinical animal models and humans, but their mechanisms of action remain poorly understood. Here, using a stabilized HIV envelope trimer immunogen, we carried out studies in nonhuman primates (NHPs) comparing the most common clinical adjuvant aluminum hydroxide (alum) with saponin/monophosphoryl lipid A nanoparticles (SMNP), an immune-stimulating complex-like adjuvant. SMNP elicited substantially stronger humoral immune responses than alum, including 7-fold higher peak antigen-specific germinal center B-cell responses, 18-fold higher autologous neutralizing antibody titers, and higher levels of antigen-specific plasma and memory B cells. Positron emission tomography and computed tomography imaging in live NHPs showed that, unlike alum, SMNP promoted rapid antigen accumulation in both proximal and distal lymph nodes (LNs). SMNP also induced strong type I interferon transcriptional signatures, expansion of innate immune cells, and increased antigen-presenting cell activation in LNs. These findings indicate that SMNP promotes multiple facets of the early immune response relevant for enhanced immunity to vaccination.

Poly I:C vaccination drives transient CXCL9 expression near B cell follicles in the lymph node through type-I and type-II interferon signaling

Subunit vaccines drive immune cell-cell interactions in the lymph node (LN), yet it remains unclear how distinct adjuvants influence the chemokines responsible for this interaction in the tissue. Here, we tested the hypothesis that classic Th1-polarizing vaccines elicit a unique chemokine signature in the LN compared to other adjuvants. Polyinosinic:polycytidylic acid (Poly I:C) vaccination resulted in dynamic upregulation of CXCL9 that was localized in the interfollicular region, a response not observed after vaccination with alum or a combination of alum and poly I:C. Experiments using in vivo mouse models and live ex vivo LN slices revealed that poly I:C vaccination resulted in a type-I IFN response in the LN that led to the secretion of IFNγ, and type-I IFN and IFNγ were required for CXCL9 expression in this context. CXCL9 expression in the LN was correlated with an IgG2c antibody polarization after vaccination; however, genetic depletion of the receptor for CXCL9 did not prevent the development of this polarization. Additionally, we measured secretion of CXCL9 from ex vivo LN slices after stimulation with a variety of adjuvants and confirmed that adjuvants that induced IFNγ responses also promoted CXCL9 expression. Taken together, these results identify a CXCL9 signature in a suite of Th1-polarizing adjuvants and determined the pathway involved in driving CXCL9 in the LN, opening avenues to target this chemokine pathway in future vaccines.

Neutralization activity in chronic HIV infection is characterized by a distinct programming of follicular helper CD4 T cells

A subset of people living with HIV (PLWH) can produce broadly neutralizing antibodies (bNAbs) against HIV, but the lymph node (LN) dynamics that promote the generation of these antibodies are poorly understood. Here, we explored LN-associated histological, immunological, and virological mechanisms of bNAb generation in a cohort of anti-retroviral therapy (ART)-naïve PLWH. We found that participants who produce bNAbs, termed neutralizers, have a superior LN-associated B cell follicle architecture compared with PLWH who do not. The latter was associated with a significantly higher in situ prevalence of Bcl-6hi follicular helper CD4 T cells (TFH), expressing a molecular program that favors their differentiation and stemness, and significantly reduced IL-10 follicular suppressor CD4 T cells. Furthermore, our data reveal possible molecular targets mediating TFH- B cell interactions in neutralizers. Together, we identify cellular and molecular mechanisms that contribute to the development of bNAbs in PLWH.

Distinct components of nucleoside-modified messenger RNA vaccines cooperate to instruct efficient germinal center responses

Nucleoside-modified mRNA vaccines elicit protective antibodies through their ability to promote T follicular helper (Tfh) cells. The lipid nanoparticle (LNP) component of mRNA vaccines possesses inherent adjuvant activity. However, to what extent the nucleoside-modified mRNA can be sensed and contribute to Tfh cell responses remains largely undefined. Herein, we deconvoluted the signals induced by LNP and mRNA that instruct dendritic cells (DCs) to promote Tfh cell differentiation. We demonstrated that the nucleoside-modified mRNA drives the production of type I interferons that act on DCs to induce their maturation and the induction of Th1-biased Tfh responses. Conversely, LNP favors the acquisition of a Tfh cell-inducing program in DCs, a stronger Th2 polarization in Tfh cells, and allows for rapid mRNA translation by DCs within the draining lymph node. Our work unravels distinct adjuvant features of mRNA and LNP necessary for the induction of Tfh cells, with implications for vaccine design.

The lipid globotriaosylceramide promotes germinal center B cell responses and antiviral immunity

Influenza viruses escape immunity owing to rapid antigenic evolution, which requires vaccination strategies that allow for broadly protective antibody responses. We found that the lipid globotriaosylceramide (Gb3) expressed on germinal center (GC) B cells is essential for the production of high-affinity antibodies. Mechanistically, Gb3 bound and disengaged CD19 from its chaperone CD81, permitting CD19 to translocate to the B cell receptor complex to trigger signaling. Moreover, Gb3 regulated major histocompatibility complex class II expression to increase diversity of T follicular helper and GC B cells reactive with subdominant epitopes. In influenza infection, elevating Gb3, either endogenously or exogenously, promoted broadly reactive antibody responses and cross-protection. These data demonstrate that Gb3 determines the affinity and breadth of B cell immunity and has potential as a vaccine adjuvant.

The crucial regulatory role of type I interferon in inflammatory diseases

Type I interferon (IFN-I) plays crucial roles in the regulation of inflammation and it is associated with various inflammatory diseases including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and periodontitis, impacting people's health and quality of life. It is well-established that IFN-Is affect immune responses and inflammatory factors by regulating some signaling. However, currently, there is no comprehensive overview of the crucial regulatory role of IFN-I in distinctive pathways as well as associated inflammatory diseases. This review aims to provide a narrative of the involvement of IFN-I in different signaling pathways, mainly mediating the related key factors with specific targets in the pathways and signaling cascades to influence the progression of inflammatory diseases. As such, we suggested that IFN-Is induce inflammatory regulation through the stimulation of certain factors in signaling pathways, which displays possible efficient treatment methods and provides a reference for the precise control of inflammatory diseases.

The lipid Gb3 promotes germinal center B cell responses and anti-viral immunity

Influenza viruses escape immunity due to rapid antigenic evolution, which requires vaccination strategies that allow for broadly protective antibody responses. Here, we demonstrate that the lipid globotriaosylceramide (Gb3) expressed on germinal center (GC) B cells is essential for the production of high-affinity antibodies. Mechanistically, Gb3 binds and disengages CD19 from its chaperone CD81 for subsequent translocation to the B cell receptor (BCR) complex to trigger signaling. Abundance of Gb3 amplifies the PI3-kinase/Akt/Foxo1 pathway to drive affinity maturation. Moreover, this lipid regulates MHC-II expression to increase diversity of T follicular helper (Tfh) and GC B cells reactive with subdominant epitopes. In influenza infection, Gb3 promotes broadly reactive antibody responses and cross-protection. Thus, we show that Gb3 determines affinity as well as breadth in B cell immunity and propose this lipid as novel vaccine adjuvant against viral infection.

One Sentence Summary

Gb3 abundance on GC B cells selects antibodies with high affinity and broad epitope reactivities, which are cross-protective against heterologous influenza infection.

Type III interferon exerts thymic stromal lymphopoietin in mediating adaptive antiviral immune response

Previously, it was believed that type III interferon (IFN-III) has functions similar to those of type I interferon (IFN-I). However, recently, emerging findings have increasingly indicated the non-redundant role of IFN-III in innate antiviral immune responses. Still, the regulatory activity of IFN-III in adaptive immune response has not been clearly reported yet due to the low expression of IFN-III receptors on most immune cells. In the present study, we reviewed the adjuvant, antiviral, antitumor, and disease-moderating activities of IFN-III in adaptive immunity; moreover, we further elucidated the mechanisms of IFN-III in mediating the adaptive antiviral immune response in a thymic stromal lymphopoietin (TSLP)-dependent manner, a pleiotropic cytokine involved in mucosal adaptive immunity. Research has shown that IFN-III can enhance the antiviral immunogenic response in mouse species by activating germinal center B (GC B) cell responses after stimulating TSLP production by microfold (M) cells, while in human species, TSLP exerts OX40L for regulating GC B cell immune responses, which may also depend on IFN-III. In conclusion, our review highlights the unique role of the IFN-III/TSLP axis in mediating host adaptive immunity, which is mechanically different from IFN-I. Therefore, the IFN-III/TSLP axis may provide novel insights for clinical immunotherapy.

Epstein-Barr virus and genetic risk variants as determinants of T-bet+ B cell-driven autoimmune diseases

B cells expressing the transcription factor T-bet are found to have a protective role in viral infections, but are also considered major players in the onset of different types of autoimmune diseases. Currently, the exact mechanisms driving such 'atypical' memory B cells to contribute to protective immunity or autoimmunity are unclear. In addition to general autoimmune-related factors including sex and age, the ways T-bet+ B cells instigate autoimmune diseases may be determined by the close interplay between genetic risk variants and Epstein-Barr virus (EBV). The impact of EBV on T-bet+ B cells likely relies on the type of risk variants associated with each autoimmune disease, which may affect their differentiation, migratory routes and effector function. In this hypothesis-driven review, we discuss the lines of evidence pointing to such genetic and/or EBV-mediated influence on T-bet+ B cells in a range of autoimmune diseases, including systemic lupus erythematosus (SLE) and multiple sclerosis (MS). We provide examples of how genetic risk variants can be linked to certain signaling pathways and are differentially affected by EBV to shape T-bet+ B-cells. Finally, we propose options to improve current treatment of B cell-related autoimmune diseases by more selective targeting of pathways that are critical for pathogenic T-bet+ B-cell formation.

A novel defined TLR3 agonist as an effective vaccine adjuvant

Synthetic double-stranded RNA analogs recognized by Toll-like receptor 3 (TLR3) are an attractive adjuvant candidate for vaccines, especially against intracellular pathogens or tumors, because of their ability to enhance T cell and antibody responses. Although poly(I:C) is a representative dsRNA with potent adjuvanticity, its clinical application has been limited due to heterogeneous molecular size, inconsistent activity, poor stability, and toxicity. To overcome these limitations, we developed a novel dsRNA-based TLR3 agonist named NexaVant (NVT) by using PCR-coupled bidirectional in vitro transcription. Agarose gel electrophoresis and reverse phase-HPLC analysis demonstrated that NVT is a single 275-kDa homogeneous molecule. NVT appears to be stable since its appearance, concentration, and molecular size were unaffected under 6 months of accelerated storage conditions. Moreover, preclinical evaluation of toxicity under good laboratory practices showed that NVT is a safe substance without any signs of serious toxicity. NVT stimulated TLR3 and increased the expression of viral nucleic acid sensors TLR3, MDA-5, and RIG-1. When intramuscularly injected into C57BL/6 mice, ovalbumin (OVA) plus NVT highly increased the migration of dendritic cells (DCs), macrophages, and neutrophils into inguinal lymph node (iLN) compared with OVA alone. In addition, NVT substantially induced the phenotypic markers of DC maturation and activation including MHC-II, CD40, CD80, and CD86 together with IFN-β production. Furthermore, NVT exhibited an appropriate adjuvanticity because it elevated OVA-specific IgG, in particular, higher levels of IgG2c (Th1-type) but lower IgG1 (Th2-type). Concomitantly, NVT increased the levels of Th1-type T cells such as IFN-γ⁺CD4⁺ and IFN-γ⁺CD8⁺ cells in response to OVA stimulation. Collectively, we suggest that NVT with appropriate safety and effectiveness is a novel and promising adjuvant for vaccines, especially those requiring T cell mediated immunity such as viral and cancer vaccines.

A Monovalent Mt10-CVB3 Vaccine Prevents CVB4-Accelerated Type 1 Diabetes in NOD Mice

Enteroviruses, which include Coxsackieviruses, are a common cause of virus infections in humans, and multiple serotypes of the group B Coxsackievirus (CVB) can induce similar diseases. No vaccines are currently available to prevent CVB infections because developing serotype-specific vaccines is not practical. Thus, developing a vaccine that induces protective immune responses for multiple serotypes is desired. In that direction, we created a live-attenuated CVB3 vaccine virus, designated mutant (Mt)10, that offers protection against myocarditis and pancreatitis induced by CVB3 and CVB4 in disease-susceptible A/J mice. Here, we report that the Mt10 vaccine protected against CVB4-triggered type 1 diabetes (T1D) in non-obese diabetic (NOD) mice but the expected subsequent development of spontaneous T1D in these genetically predisposed NOD mice was not altered. We noted that Mt10 vaccine induced significant amounts of neutralizing antibodies, predominantly of the IgG2c isotype, and the virus was not detected in vaccine-challenged animals. Furthermore, monitoring blood glucose levels-and to a lesser extent, insulin antibodies-was found to be helpful in predicting vaccine responses. Taken together, our data suggest that the monovalent Mt10 vaccine has the potential to prevent infections caused by multiple CVB serotypes, as we have demonstrated in various pre-clinical models.