T cell genetic background determines default T helper phenotype development in vitro

IL-4 alters TLR7-induced B cell developmental program in lupus

TLR7 stimulation of T-bet+CD11c+IgD-CD27- double-negative 2 (DN2) B cells is crucial for autoantibody formation in systemic lupus erythematosus (SLE). Here, we show that administration of IL-4 for five weeks significantly reduced autoantibodies and T-bet+CD11c+ IgD- B cells in autoimmune BXD2 mice treated with R848, a TLR7 agonist. Single-cell transcriptomics analysis indicates that following two doses of in vivo administration, IL-4 redirected development toward follicular, CD23+ germinal center (GC), and DN4-like memory B cells compared to treatment with R848 alone. While IL-4 enhanced genes related to antigen processing and presentation, it also suppressed R848-induced Ki67+ GC B cells in vivo. In vitro stimulation of SLE patient B cells with a DN2 polarizing cocktail revealed that IL-4 reduced the expression of interferon response and DN2 signature genes, promoting a population of CD23+T-bet- DN4 B population. These findings suggest that developmental reprogramming by IL-4 counteracts TLR7-promoted DN2 and GC B cells in SLE.

Adjuvant-dependent impacts on vaccine-induced humoral responses and protection in preclinical models of nasal and genital colonization by pathogenic Neisseria

Neisseria gonorrhoeae, which causes the sexually transmitted infection gonorrhea and Neisseria meningitidis, a leading cause of bacterial meningitis and septicemia, are closely related human-restricted pathogens that inhabit distinct primary mucosal niches. While successful vaccines against invasive meningococcal disease have been available for decades, the rapid rise in antibiotic resistance has led to an urgent need to develop an effective gonococcal vaccine. Several surface antigens are shared among these two pathogens, making cross-species protection an exciting prospect. However, the type of vaccine-mediated immune response required to achieve protection against respiratory versus genital infection remains ill defined. In this study, we utilize well established mouse models of female lower genital tract colonization by N. gonorrhoeae and upper respiratory tract colonization by N. meningitidis to examine the performance of transferrin binding protein B (TbpB) vaccines formulated with immunologically distinct vaccine adjuvants. We demonstrate that vaccine-mediated protection is influenced by the choice of adjuvant, with Th1/2-balanced adjuvants performing optimally against N. gonorrhoeae, and both Th1/2-balanced and Th2-skewing adjuvants leading to a significant reduction in N. meningitidis burden. We further establish a lack of correlation between protection status and the humoral response or bactericidal titre. Combined, this work supports the feasibility for a single vaccine formulation to achieve pan-neisserial coverage.

Baseline gene expression in BALB/c and C57BL/6 peritoneal macrophages influences but does not dictate their functional phenotypes

Macrophages are effector cells of the immune system and essential modulators of immune responses. Different functional phenotypes of macrophages with specific roles in the response to stimuli have been described. The C57BL/6 and BALB/c mouse strains tend to selectively display distinct macrophage activation states in response to pathogens, namely, the M1 and M2 phenotypes, respectively. Herein we used RNA-Seq and differential expression analysis to characterize the baseline gene expression pattern of unstimulated resident peritoneal macrophages from C57BL/6 and BALB/c mice. Our aim is to determine if there is a possible predisposition of these mouse strains to any activation phenotype and how this may affect the interpretation of results in studies concerning their interaction with pathogens. We found differences in basal gene expression patterns of BALB/c and C57BL/6 mice, which were further confirmed using RT-PCR for a subset of relevant genes. Despite these differences, our data suggest that baseline gene expression patterns of both mouse strains do not appear to determine by itself a specific macrophage phenotype.

Influence of Th1 versus Th2 immune bias on viral, pathological, and immunological dynamics in SARS-CoV-2 variant-infected human ACE2 knock-in mice

BACKGROUND

Mouse models that recapitulate key features of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection are important tools for understanding complex interactions between host genetics, immune responses, and SARS-CoV-2 pathogenesis. Little is known about how predominantly cellular (Th1 type) versus humoral (Th2 type) immune responses influence SARS-CoV-2 dynamics, including infectivity and disease course.

METHODS

We generated knock-in (KI) mice expressing human ACE2 (hACE2) and/or human TMPRSS2 (hTMPRSS2) on Th1-biased (C57BL/6; B6) and Th2-biased (BALB/c) genetic backgrounds. Mice were infected intranasally with SARS-CoV-2 Delta (B.1.617.2) or Omicron BA.1 (B.1.1.529) variants, followed by assessment of disease course, respiratory tract infection, lung histopathology, and humoral and cellular immune responses.

FINDINGS

In both B6 and BALB/c mice, hACE2 expression was required for infection of the lungs with Delta, but not Omicron BA.1. Disease severity was greater in Omicron BA.1-infected hTMPRSS2-KI and double-KI BALB/c mice compared with B6 mice, and in Delta-infected double-KI B6 and BALB/c mice compared with hACE2-KI mice. hACE2-KI B6 mice developed more severe lung pathology and more robust SARS-CoV-2-specific splenic CD8 T cell responses compared with hACE2-KI BALB/c mice. There were no notable differences between the two genetic backgrounds in plasma cell, germinal center B cell, or antibody responses to SARS-CoV-2.

INTERPRETATION

SARS-CoV-2 Delta and Omicron BA.1 infection, disease course, and CD8 T cell response are influenced by the host genetic background. These humanized mice hold promise as important tools for investigating the mechanisms underlying the heterogeneity of SARS-CoV-2-induced pathogenesis and immune response.

FUNDING

This work was funded by NIH U19 AI142790-02S1, the GHR Foundation, the Arvin Gottleib Foundation, and the Overton family (to SS and EOS); Prebys Foundation (to SS); NIH R44 AI157900 (to KJ); and by an American Association of Immunologists Career Reentry Fellowship (FASB).

Immune mechanisms in the pathophysiology of hypertension

Hypertension is a leading risk factor for morbidity and mortality worldwide. Despite current anti-hypertensive therapies, most individuals with hypertension fail to achieve adequate blood pressure control. Moreover, even with adequate control, a residual risk of cardiovascular events and associated organ damage remains. These findings suggest that current treatment modalities are not addressing a key element of the underlying pathology. Emerging evidence implicates immune cells as key mediators in the development and progression of hypertension. In this Review, we discuss our current understanding of the diverse roles of innate and adaptive immune cells in hypertension, highlighting key findings from human and rodent studies. We explore mechanisms by which these immune cells promote hypertensive pathophysiology, shedding light on their multifaceted involvement. In addition, we highlight advances in our understanding of autoimmunity, HIV and immune checkpoints that provide valuable insight into mechanisms of chronic and dysregulated inflammation in hypertension.

VLPs generated by the fusion of RSV-F or hMPV-F glycoprotein to HIV-Gag show improved immunogenicity and neutralizing response in mice

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) vaccines have been long overdue. Structure-based vaccine design created a new momentum in the last decade, and the first RSV vaccines have finally been approved in older adults and pregnant individuals. These vaccines are based on recombinant stabilized pre-fusion F glycoproteins administered as soluble proteins. Multimeric antigenic display could markedly improve immunogenicity and should be evaluated in the next generations of vaccines. Here we tested a new virus like particles-based vaccine platform which utilizes the direct fusion of an immunogen of interest to the structural human immunodeficient virus (HIV) protein Gag to increase its surface density and immunogenicity. We compared, in mice, the immunogenicity of RSV-F or hMPV-F based immunogens delivered either as soluble proteins or displayed on the surface of our VLPs. VLP associated F-proteins showed better immunogenicity and induced superior neutralizing responses. Moreover, when combining both VLP associated and soluble immunogens in a heterologous regimen, VLP-associated immunogens provided added benefits when administered as the prime immunization.

Preclinical dose response study shows NR2E3 can attenuate retinal degeneration in the retinitis pigmentosa mouse model RhoP23H+/. Gene Ther 2024;31:255-262. [PMID: 38273095 PMCID: PMC11090815 DOI: 10.1038/s41434-024-00440-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Retinitis pigmentosa (RP) is a heterogeneous disease and the main cause of vision loss within the group of inherited retinal diseases (IRDs). IRDs are a group of rare disorders caused by mutations in one or more of over 280 genes which ultimately result in blindness. Modifier genes play a key role in modulating disease phenotypes, and mutations in them can affect disease outcomes, rate of progression, and severity. Our previous studies have demonstrated that the nuclear hormone receptor 2 family e, member 3 (Nr2e3) gene reduced disease progression and loss of photoreceptor cell layers in RhoP23H-/- mice. This follow up, pharmacology study evaluates a longitudinal NR2E3 dose response in the clinically relevant heterozygous RhoP23H mouse. Reduced retinal degeneration and improved retinal morphology was observed 6 months following treatment evaluating three different NR2E3 doses. Histological and immunohistochemical analysis revealed regions of photoreceptor rescue in the treated retinas of RhoP23H+/- mice. Functional assessment by electroretinogram (ERG) showed attenuated photoreceptor degeneration with all doses. This study demonstrates the effectiveness of different doses of NR2E3 at reducing retinal degeneration and informs dose selection for clinical trials of RhoP23H-associated RP.

Site-specific regulation of Th2 differentiation within lymph node microenvironments

T helper 2 (Th2) responses protect against pathogens while also driving allergic inflammation, yet how large-scale Th2 responses are generated in tissue context remains unclear. Here, we used quantitative imaging to investigate early Th2 differentiation within lymph nodes (LNs) following cutaneous allergen administration. Contrary to current models, we observed extensive activation and "macro-clustering" of early Th2 cells with migratory type-2 dendritic cells (cDC2s), generating specialized Th2-promoting microenvironments. Macro-clustering was integrin-mediated and promoted localized cytokine exchange among T cells to reinforce differentiation, which contrasted the behavior during Th1 responses. Unexpectedly, formation of Th2 macro-clusters was dependent on the site of skin sensitization. Differences between sites were driven by divergent activation states of migratory cDC2 from different dermal tissues, with enhanced costimulatory molecule expression by cDC2 in Th2-generating LNs promoting prolonged T cell activation, macro-clustering, and cytokine sensing. Thus, the generation of dedicated Th2 priming microenvironments through enhanced costimulatory molecule signaling initiates Th2 responses in vivo and occurs in a skin site-specific manner.

Toxoplasma type II effector GRA15 has limited influence in vivo

Toxoplasma gondii is an intracellular parasite that establishes a long-term infection in the brain of many warm-blooded hosts, including humans and rodents. Like all obligate intracellular microbes, Toxoplasma uses many effector proteins to manipulate the host cell to ensure parasite survival. While some of these effector proteins are universal to all Toxoplasma strains, some are polymorphic between Toxoplasma strains. One such polymorphic effector is GRA15. The gra15 allele carried by type II strains activates host NF-κB signaling, leading to the release of cytokines such as IL-12, TNF, and IL-1β from immune cells infected with type II parasites. Prior work also suggested that GRA15 promotes early host control of parasites in vivo, but the effect of GRA15 on parasite persistence in the brain and the peripheral immune response has not been well defined. For this reason, we sought to address this gap by generating a new IIΔgra15 strain and comparing outcomes at 3 weeks post infection between WT and IIΔgra15 infected mice. We found that the brain parasite burden and the number of macrophages/microglia and T cells in the brain did not differ between WT and IIΔgra15 infected mice. In addition, while IIΔgra15 infected mice had a lower number and frequency of splenic M1-like macrophages and frequency of PD-1+ CTLA-4+ CD4+ T cells and NK cells compared to WT infected mice, the IFN-γ+ CD4 and CD8 T cell populations were equivalent. In summary, our results suggest that in vivo GRA15 may have a subtle effect on the peripheral immune response, but this effect is not strong enough to alter brain parasite burden or parenchymal immune cell number at 3 weeks post infection.

The immunobiology of SARS-CoV-2 infection and vaccine responses: potential influences of cross-reactive memory responses and aging on efficacy and off-target effects

Immune responses to both SARS-CoV-2 infection and its associated vaccines have been highly variable within the general population. The increasing evidence of long-lasting symptoms after resolution of infection, called post-acute sequelae of COVID-19 (PASC) or "Long COVID," suggests that immune-mediated mechanisms are at play. Closely related endemic common human coronaviruses (hCoV) can induce pre-existing and potentially cross-reactive immunity, which can then affect primary SARS-CoV-2 infection, as well as vaccination responses. The influence of pre-existing immunity from these hCoVs, as well as responses generated from original CoV2 strains or vaccines on the development of new high-affinity responses to CoV2 antigenic viral variants, needs to be better understood given the need for continuous vaccine adaptation and application in the population. Due in part to thymic involution, normal aging is associated with reduced naïve T cell compartments and impaired primary antigen responsiveness, resulting in a reliance on the pre-existing cross-reactive memory cell pool which may be of lower affinity, restricted in diversity, or of shorter duration. These effects can also be mediated by the presence of down-regulatory anti-idiotype responses which also increase in aging. Given the tremendous heterogeneity of clinical data, utilization of preclinical models offers the greatest ability to assess immune responses under a controlled setting. These models should now involve prior antigen/viral exposure combined with incorporation of modifying factors such as age on immune responses and effects. This will also allow for mechanistic dissection and understanding of the different immune pathways involved in both SARS-CoV-2 pathogen and potential vaccine responses over time and how pre-existing memory responses, including potential anti-idiotype responses, can affect efficacy as well as potential off-target effects in different tissues as well as modeling PASC.

Blockade of CD80/CD86-CD28 co-stimulation augments the inhibitory function of peptide antigen-specific regulatory T cells

Mixed lymphocyte culture under the blockade of CD80/CD86-CD28 co-stimulation induces anergic (completely hyporesponsive) T cells with immune suppressive function (inducible suppressing T cells: iTS cells). Previously, iTS cell therapy has demonstrated outstanding benefits in clinical trials for organ transplantation. Here, we examined whether peptide antigen-specific iTS cells are inducible. DO 11.10 iTS cells were obtained from splenocytes of BALB/c DO 11.10 mice by stimulation with OVA peptide and antagonistic anti-CD80/CD86 mAbs. When DO 11.10 iTS or Foxp3- DO 11.10 iTS cells were stimulated with OVA, these cells produced IL-13, but not IL-4. DO 11.10 iTS cells decreased IL-4 and increased IL-13 production from OVA-stimulated naïve DO 11.10 splenocytes. When Foxp3+ DO 11.10 iTS cells were prepared, these cells significantly inhibited the production of IL-4 and IL-13 compared with freshly isolated Foxp3+ DO 11.10 T cells. Moreover, an increase in the population expressing OX40, ICOS, and 4-1BB suggested activation of Foxp3+ DO 11.10 iTS cells. Thus, blockade of CD80/CD86-CD28 co-stimulation during peptide antigen stimulation augments the inhibitory function of Foxp3+ regulatory T cells, and does not induce anergic Foxp3- conventional T cells. Peptide-specific Foxp3+ regulatory iTS cells could be useful for the treatment of allergic and autoimmune diseases without adverse effects.

TLR2, TLR3, TLR4, TLR9 and TLR11 expression on effector CD4+ T-cell subsets in Leishmania donovani infection

T-cells play a central role in cell-mediated immunity. While activation of T-cells is major histocompatibility-restricted, the Toll-like receptors (TLRs)- a family of proteins that recognize conserved molecular patterns present on the pathogens-are not well-studied for their expression and function in T-cells. As any association of TLR expression profiles with an effector T-cell subset is unknown, we analyze BALB/c mice-derived CD4+ and CD8+ T-cells' TLR expression profiles. We report: CD4+t-bet+ T-cells are frequent in TLR2LowTLR3HighTLR4Low subpopulation, CD4+GATA3+ T-cells are frequent within the cells with intermediate expression of TLR2, TLR3, TLR4 and TLR11, CD4+FoxP3+ T-cells in TLR2HighTLR3High cells whereas CD4+RORγt + T-cells are frequent in TLR2LowTLR3LowTLR4LowTLR11Low cells. CD4+ effector T-cell subsets may therefore show association with TLRs- TLR3, in particular-expression. In Leishmania donovani infection in BALB/c mice, TLR3 expression on both CD4+ and CD8+ T-cells is reduced. Poly-I:C, a TLR3 ligand, do not have any distinctive effects on the CD4+ effector T-cell subsets. These data suggest that TLRs on T-cells may not function as a primary receptor that controls T-cell function but their distinctive expression profiles on different T-cell subsets suggest plausible immunomodulatory role.

Tissue-resident B cells orchestrate macrophage polarisation and function

B cells play a central role in humoral immunity but also have antibody-independent functions. Studies to date have focused on B cells in blood and secondary lymphoid organs but whether B cells reside in non-lymphoid organs (NLO) in homeostasis is unknown. Here we identify, using intravenous labeling and parabiosis, a bona-fide tissue-resident B cell population in lung, liver, kidney and urinary bladder, a substantial proportion of which are B-1a cells. Tissue-resident B cells are present in neonatal tissues and also in germ-free mice NLOs, albeit in lower numbers than in specific pathogen-free mice and following co-housing with 'pet-store' mice. They spatially co-localise with macrophages and regulate their polarization and function, promoting an anti-inflammatory phenotype, in-part via interleukin-10 production, with effects on bacterial clearance during urinary tract infection. Thus, our data reveal a critical role for tissue-resident B cells in determining the homeostatic 'inflammatory set-point' of myeloid cells, with important consequences for tissue immunity.

Prolonged T cell - DC macro-clustering within lymph node microenvironments initiates Th2 cell differentiation in a site-specific manner

Formation of T helper 2 (Th2) responses has been attributed to low-grade T cell stimulation, yet how large-scale polyclonal Th2 responses are generated in vivo remains unclear. Here, we used quantitative imaging to investigate early Th2 differentiation within lymph nodes (LNs) following cutaneous allergen administration. Contrary to current models, Th2 differentiation was associated with enhanced T cell activation and extensive integrin-dependent 'macro-clustering' at the T-B border, which also contrasted clustering behavior seen during Th1 differentiation. Unexpectedly, formation of Th2 macro-clusters within LNs was highly dependent on the site of skin sensitization. Differences between sites were driven by divergent activation states of migratory cDC2 from different dermal tissues, with enhanced costimulatory molecule expression by cDC2 in Th2-generating LNs promoting T cell macro-clustering and cytokine sensing. Thus, generation of dedicated priming micro-environments through enhanced costimulatory molecule signaling initiates the generation of Th2 responses in vivo and occurs in a skin site-specific manner.

Genetic mapping reveals Pou2af2/OCA-T1-dependent tuning of tuft cell differentiation and intestinal type 2 immunity

Chemosensory epithelial tuft cells contribute to innate immunity at barrier surfaces, but their differentiation from epithelial progenitors is not well understood. Here, we exploited differences between inbred mouse strains to identify an epithelium-intrinsic mechanism that regulates tuft cell differentiation and tunes innate type 2 immunity in the small intestine. Balb/cJ (Balb) mice had fewer intestinal tuft cells than C57BL/6J (B6) mice and failed to respond to the tuft cell ligand succinate. Most of this differential succinate response was determined by the 50- to 67-Mb interval of chromosome 9 (Chr9), such that congenic Balb mice carrying the B6 Chr9 interval had elevated baseline numbers of tuft cells and responded to succinate. The Chr9 locus includes Pou2af2, which encodes the protein OCA-T1, a transcriptional cofactor essential for tuft cell development. Epithelial crypts expressed a previously unannotated short isoform of Pou2af2 predicted to use a distinct transcriptional start site and encode a nonfunctional protein. Low tuft cell numbers and the resulting lack of succinate response in Balb mice were explained by a preferential expression of the short isoform and could be rescued by expression of full-length Pou2af2. Physiologically, Pou2af2 isoform usage tuned innate type 2 immunity in the small intestine. Balb mice maintained responsiveness to helminth pathogens while ignoring commensal Tritrichomonas protists and reducing norovirus burdens.

CTLA-4 inhibition facilitates follicular T and B cell interaction and the production of tumor-specific antibodies

Immune checkpoint inhibitors (ICIs) induce activation and expansion of cytotoxic T cells. To depict a comprehensive immune cell landscape reshaped by the CTLA-4 checkpoint inhibitor, we performed single-cell RNA sequencing in a mouse syngeneic tumor transplant model. After CTLA-4 inhibition, tumor regression was accompanied by massive immune cell expansion, especially in T and B cells. We found that B cells in tumor transplant represented follicular, germinal center and plasma B cells, some of which shared identical B cell receptor clonotypes and possessed tumor reactivity. Furthermore, the posttreatment tumor contained a tertiary lymphoid-like structure with intermingled T and B cells. These data suggest germinal center formation within the tumor mass and in situ differentiation of tumor-specific plasma cells. Taken together, our data provide a panoramic view of the immune microenvironment after CTLA-4 inhibition and suggest a role for tumor-specific B cells in antitumor immunity.

B lymphocytes deficiency results in altered immune response and increased susceptibility to Mycobacterium leprae in a murine leprosy model

Leprosy is a chronic and infectious disease that primarily affects the skin and peripheral nervous system, presenting a wide spectrum of clinical forms with different degrees of severity. The distinct host immune response patters developed in the response to the bacillus Mycobacterium leprae, the leprosy etiologic agent, are associated with the spectral clinical forms and outcome of the disease. In this context, B cells are allegedly involved in the disease immunopathogenesis, usually as antibody-producing cells, but also as potential effector or regulatory elements. In order to determine the regulatory B cells role in experimental leprosy, this study evaluated the outcome of M. leprae infection in B cell deficient mice (BKO) and WT C57Bl/6 control, by means of microbiological/bacilloscopic, immunohistochemical and molecular analysis, performed 8 months after M. leprae inoculation. The results demonstrated that infected BKO showed a higher bacilli number when compared with WT animals, demonstrating the importance of these cells in experimental leprosy. The molecular analysis demonstrates that the expression of IL-4, IL-10 and TGF-β was significantly higher in the BKO footpads when compared to WT group. Conversely, there was no difference in IFN-γ, TNF-α and IL-17 expression levels in BKO and WT groups. IL-17 expression was significantly higher in the lymph nodes of WT group. The immunohistochemical analysis revealed that M1 (CD80⁺) cells counts were significantly lower in the BKO group, while no significant difference was observed to M2 (CD206⁺) counts, resulting a skewed M1/M2 balance. These results demonstrated that the absence of B lymphocytes contribute to the persistence and multiplication of M. leprae, probably due to the increased expression of the IL-4, IL-10 and TGF-β cytokines, as well as a decrease in the number of M1 macrophages in the inflammatory site.

The classical pathway triggers pathogenic complement activation in membranous nephropathy

Membranous nephropathy (MN) is an antibody-mediated autoimmune disease characterized by glomerular immune complexes containing complement components. However, both the initiation pathways and the pathogenic significance of complement activation in MN are poorly understood. Here, we show that components from all three complement pathways (alternative, classical and lectin) are found in renal biopsies from patients with MN. Proximity ligation assays to directly visualize complement assembly in the tissue reveal dominant activation via the classical pathway, with a close correlation to the degree of glomerular C1q-binding IgG subclasses. In an antigen-specific autoimmune mouse model of MN, glomerular damage and proteinuria are reduced in complement-deficient mice compared with wild-type littermates. Severe disease with progressive ascites, accompanied by extensive loss of the integral podocyte slit diaphragm proteins, nephrin and neph1, only occur in wild-type animals. Finally, targeted silencing of C3 using RNA interference after the onset of proteinuria significantly attenuates disease. Our study shows that, in MN, complement is primarily activated via the classical pathway and targeting complement components such as C3 may represent a promising therapeutic strategy.

Effects of Regulatory T Cell Depletion in BALB/c Mice Infected with Low Doses of Borrelia burgdorferi

We previously demonstrated that a depletion of regulatory T (Treg) cells in Lyme arthritis-resistant C57BL/6 mice leads to pathological changes in the tibiotarsal joints following infection with Borrelia burgdorferi. Here, we assessed the effects of Treg cells on the response to B. burgdorferi infection in BALB/c mice, which exhibit infection-dose-dependent disease and a different sequence of immune events than C57BL/6 mice. The depletion of Treg cells prior to infection with 1 × 102, but not 5 × 103, organisms led to increased swelling of the tibiotarsal joints. However, Treg cell depletion did not significantly affect the development of histopathology at these low doses of infection. BALB/c mice depleted of Treg cells before infection with 1 × 103 spirochetes harbored a higher borrelial load in the hearts and exhibited higher levels of serum interleukin-10 five weeks later. These results indicate that Treg cells regulate certain aspects of the response to B. burgdorferi in a mouse strain that may display a range of disease severities. As the presentation of Lyme disease may vary among humans, it is necessary to consider multiple animal models to obtain a complete picture of the various means by which Treg cells affect the host response to B. burgdorferi.

Parenteral Exposure of Mice to Ricin Toxin Induces Fatal Hypoglycemia by Cytokine-Mediated Suppression of Hepatic Glucose-6-Phosphatase Expression

Ricin toxin is an agent of biodefense concern and we have been developing countermeasures for ricin threats. In doing so, we sought biomarkers of ricin toxicosis and found that in mice parenteral injection of ricin toxin causes profound hypoglycemia, in the absence of other clinical laboratory abnormalities. We now seek to identify the mechanisms underlying this hypoglycemia. Within the first hours following injection, while still normoglycemic, lymphopenia and pro-inflammatory cytokine secretion were observed, particularly tumor necrosis factor (TNF)-α. The cytokine response evolved over the next day into a complex storm of both pro- and anti-inflammatory cytokines. Evaluation of pancreatic function and histology demonstrated marked islet hypertrophy involving predominantly β-cells, but only mildly elevated levels of insulin secretion, and diminished hepatic insulin signaling. Drops in blood glucose were observed even after destruction of β-cells with streptozotocin. In the liver, we observed a rapid and persistent decrease in the expression of glucose-6-phosphatase (G6Pase) RNA and protein levels, accompanied by a drop in glucose-6-phosphate and increase in glycogen. TNF-α has previously been reported to suppress G6Pase expression. In humans, a genetic deficiency of G6Pase results in glycogen storage disease, type-I (GSD-1), a hallmark of which is potentially fatal hypoglycemia.

Ketone body augmentation decreases methacholine hyperresponsiveness in mouse models of allergic asthma

Background

Individuals with allergic asthma exhibit lung inflammation and remodeling accompanied by methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility, and they can present with a range of mild-to-severe disease amenable or resistant to therapeutic intervention, respectively. There remains a need for alternatives or complements to existing treatments that could control the physiologic manifestations of allergic asthma.

Objectives

Our aim was to examine the hypothesis that because ketone bodies elicit anti-inflammatory activity and are effective in mitigating the methacholine hyperresponsiveness associated with obese asthma, increasing systemic concentrations of ketone bodies would diminish pathologic outcomes in asthma-relevant cell types and in mouse models of allergic asthma.

Methods

We explored the effects of ketone bodies on allergic asthma-relevant cell types (macrophages, airway epithelial cells, CD4 T cells, and bronchial smooth muscle cells) in vitro as well as in vivo by using preclinical models representative of several endotypes of allergic asthma to determine whether promotion of ketosis through feeding a ketogenic diet or providing a ketone precursor or a ketone ester dietary supplement could affect immune and inflammatory parameters as well as methacholine hyperresponsiveness.

Results

In a dose-dependent manner, the ketone bodies acetoacetate and β-hydroxybutyrate (BHB) decreased proinflammatory cytokine secretion from mouse macrophages and airway epithelial cells, decreased house dust mite (HDM) extract-induced IL-8 secretion from human airway epithelial cells, and decreased cytokine production from polyclonally and HDM-activated T cells. Feeding a ketogenic diet, providing a ketone body precursor, or supplementing the diet with a ketone ester increased serum BHB concentrations and decreased methacholine hyperresponsiveness in several acute HDM sensitization and challenge models of allergic asthma. A ketogenic diet or ketone ester supplementation decreased methacholine hyperresponsiveness in an HDM rechallenge model of chronic allergic asthma. Ketone ester supplementation synergized with corticosteroid treatment to decrease methacholine hyperresponsiveness in an HDM-driven model of mixed-granulocytic severe asthma. HDM-induced morphologic changes in bronchial smooth muscle cells were inhibited in a dose-dependent manner by BHB, as was HDM protease activity.

Conclusions

Increasing systemic BHB concentrations through dietary interventions could provide symptom relief for several endotypes of allergic asthmatic individuals through effects on multiple asthma-relevant cells.

FVB/N mouse strain regulatory T cells differ in phenotype and function from the C57BL/6 and BALB/C strains

Regulatory T cells (Treg) are vital to the maintenance of immune homeostasis. The genetic background of an inbred mouse strain can have a profound effect on the immune response in the animal, including Treg responses. Most Treg studies focus on animals created on the C57BL/6 or BALB/c background. Recent studies have demonstrated a difference in the phenotype and behavior of C57BL/6 and BALB/c Tregs. In this study, we have investigated the function of FVB/N Tregs compared to C57BL/6 and BALB/c. We observed that while FVB/N Tregs appear to suppress normally in a cell contact-dependent system, FVB/N Tregs are less capable of suppressing when regulation depends on the secretion of a soluble factor. FVB/N Tregs produce IL-10; however, TGF-β was not detected in any culture from C57BL/6 or FVB/N. C57BL/6 Foxp3+ Tregs expressed more of the TGF-β-related proteins glycoprotein-A repetitions predominant (GARP) and latency-associated peptide (LAP) on the cell surface than both FVB/N and BALB/c, but C57BL/6 Tregs expressed significantly less Ctse (Cathepsin E) mRNA. Each strain displayed different abilities of thymic Tregs (tTreg) to maintain Foxp3 expression and had a varying generation of induced Tregs (iTregs). In vitro generated FVB/N iTregs expressed significantly less GARP and LAP. These results suggest Tregs of different strains have varying phenotypes and dominant mechanisms of action for the suppression of an immune response. This information should be taken into consideration when Tregs are examined in future studies, particularly for therapeutic purposes in a genetically diverse population.

Stable Recombinant Invasion Plasmid Antigen C (IpaC)-Based Single Dose Nanovaccine for Shigellosis

Shigellosis, caused by the bacteria Shigella, is the leading cause of bacterial diarrhea and the second leading cause of diarrheal death among children under the age of five. Unfortunately, Shigella strains have acquired resistance to antibiotics, and a commercial vaccine is yet to be available. We have previously demonstrated that Shigella dysenteriae serotype 1 (Sd1)-based recombinant, stabilized, "invasion plasmid antigen C" (IpaC; 42 kDa) protein can induce robust immune responses in BALB/c mice against a challenge of a high dose of heterologous Shigella when immunized via three intranasal doses of IpaC without an adjuvant. In this work, in order to reduce the frequency of dosing and increase possible patient compliance, based on our previous screening, the minimum protective dose of stabilized IpaC (20 μg) was encapsulated in biodegradable polymeric poly(lactide-co-glycolide) nanoparticles (∼370 nm) and intranasally administered in BALB/c mice in a single dose. Interestingly, a single intranasal dose of the developed vaccine particles encapsulating only 20 μg of Sd1 IpaC led to a temporal increase in the antibody production with an improved cytokine response compared to free IpaC administered three times as described in our previous report. Upon intraperitoneal challenge with a high dose of heterologous Shigella flexneri 2a (common in circulation), the immunized animals were protected from diarrhea, lethargy, and weight loss with ∼67% survival, while all the control animals died by 36 h of the challenge. Overall, the developed nanovaccine could be explored as a potential noninvasive, cross-protective, single-dose, single-antigen Shigella vaccine amenable for scale-up and eventual mass immunization.

Islet Lymphocytes Maintain a Stable Regulatory Phenotype Under Homeostatic Conditions and Metabolic Stress

T cells and B cells have been identified in human and murine islets, but the phenotype and role of islet lymphocytes is unknown. Resident immune populations set the stage for responses to inflammation in the islets during homeostasis and diabetes. Thus, we sought to identify the phenotype and effector function of islet lymphocytes to better understand their role in normal islets and in islets under metabolic stress. Lymphocytes were located in the islet parenchyma, and were comprised of a mix of naïve, activated, and memory T cell and B cell subsets, with an enrichment for regulatory B cell subsets. Use of a Nur77 reporter indicated that CD8 T cells and B cells both received local antigen stimulus, indicating that they responded to antigens present in the islets. Analysis of effector function showed that islet T cells and B cells produced the regulatory cytokine IL-10. The regulatory phenotype of islet T cells and B cells and their response to local antigenic stimuli remained stable under conditions of metabolic stress in the diet induced obesity (DIO) model. T cells present in human islets retained a similar activated and memory phenotype in non-diabetic and T2D donors. Under steady-state conditions, islet T cells and B cells have a regulatory phenotype, and thus may play a protective role in maintaining tissue homeostasis.

Gammaherpesvirus Alters Alveolar Macrophages According to the Host Genetic Background and Promotes Beneficial Inflammatory Control over Pneumovirus Infection

Human respiratory syncytial virus (hRSV) infection brings a wide spectrum of clinical outcomes, from a mild cold to severe bronchiolitis or even acute interstitial pneumonia. Among the known factors influencing this clinical diversity, genetic background has often been mentioned. In parallel, recent evidence has also pointed out that an early infectious experience affects heterologous infections severity. Here, we analyzed the importance of these two host-related factors in shaping the immune response in pneumoviral disease. We show that a prior gammaherpesvirus infection improves, in a genetic background-dependent manner, the immune system response against a subsequent lethal dose of pneumovirus primary infection notably by inducing a systematic expansion of the CD8+ bystander cell pool and by modifying the resident alveolar macrophages (AMs) phenotype to induce immediate cyto/chemokinic responses upon pneumovirus exposure, thereby drastically attenuating the host inflammatory response without affecting viral replication. Moreover, we show that these AMs present similar rapid and increased production of neutrophil chemokines both in front of pneumoviral or bacterial challenge, confirming recent studies attributing a critical antibacterial role of primed AMs. These results corroborate other recent studies suggesting that the innate immunity cells are themselves capable of memory, a capacity hitherto reserved for acquired immunity.

Age-dependent rise in IFN-γ competence undermines effective type 2 responses to nematode infection

The efficient induction of type 2 immune responses is central to the control of helminth infections. Previous studies demonstrated that strong Th1 responses driven by intracellular pathogens as well as a bias for type 1 activity in senescent mice impedes the generation of Th2 responses and the control of intestinal nematode infections. Here, we show that the spontaneous differentiation of Th1 cells and their expansion with age restrains type 2 immunity to infection with the small intestinal nematode H. polygyrus much earlier in life than previously anticipated. This includes the more extensive induction of IFN-γ competent, nematode-specific Th2/1 hybrid cells in BALB/c mice older than three months compared to younger animals. In C57BL/6 mice, Th1 cells accumulate more rapidly at steady state, translating to elevated Th2/1 differentiation and poor control of parasite fitness in primary infections experienced at a young age. Blocking of early IFN-γ and IL-12 signals during the first week of nematode infection leads to sharply decreased Th2/1 differentiation and promotes resistance in both mouse lines. Together, these data suggest that IFN-γ competent, type 1 like effector cells spontaneously accumulating in the vertebrate host progressively curtail the effectiveness of anti-nematode type 2 responses with rising host age.

How Does Mucorales Benefit from the Dysregulated Iron Homeostasis During SARS-CoV-2 Infection?

Mucorales is the cause of mucormycosis, an emerging opportunistic infection in the era of coronavirus disease 2019 (COVID-19) pandemic. Condition of hyperglycemia, diabetes mellitus, and acidosis; dysregulated iron homeostasis in the form of hyperferritinemic syndrome, and high concentration of iron in circulation; and endothelial injury related to abundance glucose regulated protein 78 (GRP78), which are present in severe COVID-19, could favor Mucorales infection. In this short communication, we summarized how the dysregulated iron homeostasis in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection benefits Mucorales.

Animal models for SARS-Cov2/Covid19 research-A commentary

INTRODUCTION

There is an urgent need for new animal models of SARS CoV-2 infection to improve research and drug development. This brief commentary examines the deficits of current models and proposes several improved alternates. The existing single transgene mouse models poorly mimic the clinical features of COVID-19; those strains get a milder disease than human COVID-19 disease. Many of the current transgenic models utilize random integration of several copies of single ACE2 transgenes, resulting in unnatural gene expression and exhibit rapid lethality. We suggest preparing precision knock-in of selected human mini genes at the mouse initiation codon and knock-out of the mouse homolog as a better option. Three genes critical for infection are suggested targets, ACE2 (the viral cellular receptor), its co-infection protease TMRPSS2, and the primary antibody clearance receptor FcγRT. To offer the best platform for COVID 19 research, preparation of single, double, and triple humanized combinations offers the researcher the opportunity to better understand the contributions of these receptors, coreceptors to therapeutic efficacy. In addition, we propose to create the humanized strains in the C57BL/6J and BALB/c backgrounds. These two backgrounds are Th1 responders and Th2 responders, respectively, and allow modeling of the variability seen in human pathology including lung pathology and late sequelae of COVID-19 disease (BALB/c). We suggest the need to do a thorough characterization of both the short-term and long-term effects of SAR-CoV-2 infection at the clinical, virologic, histopathologic, hematologic, and immunologic levels. We expect the multiply humanized strains will be superior to the single-gene and multiple-gene-copy transgenic models available to date. These mouse models will represent state-of-the-art tools for investigating mechanisms of COVID-19 pathogenesis and immunity and developing vaccines and drugs.

Tenascin-C in Heart Diseases-The Role of Inflammation

Tenascin-C (TNC) is a large extracellular matrix (ECM) glycoprotein and an original member of the matricellular protein family. TNC is transiently expressed in the heart during embryonic development, but is rarely detected in normal adults; however, its expression is strongly up-regulated with inflammation. Although neither TNC-knockout nor -overexpressing mice show a distinct phenotype, disease models using genetically engineered mice combined with in vitro experiments have revealed multiple significant roles for TNC in responses to injury and myocardial repair, particularly in the regulation of inflammation. In most cases, TNC appears to deteriorate adverse ventricular remodeling by aggravating inflammation/fibrosis. Furthermore, accumulating clinical evidence has shown that high TNC levels predict adverse ventricular remodeling and a poor prognosis in patients with various heart diseases. Since the importance of inflammation has attracted attention in the pathophysiology of heart diseases, this review will focus on the roles of TNC in various types of inflammatory reactions, such as myocardial infarction, hypertensive fibrosis, myocarditis caused by viral infection or autoimmunity, and dilated cardiomyopathy. The utility of TNC as a biomarker for the stratification of myocardial disease conditions and the selection of appropriate therapies will also be discussed from a clinical viewpoint.

Nr2e3 is a genetic modifier that rescues retinal degeneration and promotes homeostasis in multiple models of retinitis pigmentosa

Recent advances in viral vector engineering, as well as an increased understanding of the cellular and molecular mechanism of retinal diseases, have led to the development of novel gene therapy approaches. Furthermore, ease of accessibility and ocular immune privilege makes the retina an ideal target for gene therapies. In this study, the nuclear hormone receptor gene Nr2e3 was evaluated for efficacy as broad-spectrum therapy to attenuate early to intermediate stages of retinal degeneration in five unique mouse models of retinitis pigmentosa (RP). RP is a group of heterogenic inherited retinal diseases associated with over 150 gene mutations, affecting over 1.5 million individuals worldwide. RP varies in age of onset, severity, and rate of progression. In addition, ~40% of RP patients cannot be genetically diagnosed, confounding the ability to develop personalized RP therapies. Remarkably, Nr2e3 administered therapy resulted in reduced retinal degeneration as observed by increase in photoreceptor cells, improved electroretinogram, and a dramatic molecular reset of key transcription factors and associated gene networks. These therapeutic effects improved retinal homeostasis in diseased tissue. Results of this study provide evidence that Nr2e3 can serve as a broad-spectrum therapy to treat multiple forms of RP.

Lung CD103+ Dendritic cells of mice infected with Paracoccidioides brasiliensis contribute to Treg differentiation

The DC subsets that express αE integrin (CD103) have been described to exert antagonistic functions, driving T cells towards either an inflammatory (Th1/Th17) or immunosuppressive phenotype (regulatory T cells - Treg). These functions depend on the tissue they reside and microenvironment factors or stimuli that this Antigen-presenting cell (APC) subpopulation receive. In this regard, immunoregulatory phenotype has been described in small subsets of CD103⁺ DCs from lung and intestinal mucosa. The function of this APC subpopulation in pulmonary Paracoccidioides brasiliensis infection is poorly described. Here, we showed that lung CD103⁺ DCs contribute to Treg differentiation in a pulmonary P. brasiliensis infection model, which was attributed to downregulation of costimulatory molecules analyzed in these APC subtypes 21 days post-infection. Overall, this data suggests that P. brasiliensis infection caused an immunosuppression that has also been observed in patients with the most severe form of Paracoccidioidomycosis (PCM) - a sickness caused by this fungus genus. Furthermore, these results open new perspectives for knowledge of the mechanisms that underlie the higher percentage of Treg cells found in peripheral blood of PCM patients.

The cationic liposome CCS/C adjuvant induces immunity to influenza independently of the adaptor protein MyD88

Traditional non-living vaccines are often least effective in the populations that need them most, such as neonates and elderly adults. Vaccine adjuvants are one approach to boost the immunogenicity of antigens in populations with reduced immunity. Ideally, vaccine adjuvants will increase the seroconversion rates across the population, lead to stronger immune responses, and enable the administration of fewer vaccine doses. We previously demonstrated that a cationic liposomal formulation of the commercial influenza split virus vaccine (CCS/C-HA) enhanced cellular and humoral immunity to the virus, increased seroconversion rates, and improved survival after live virus challenge in a preclinical model, as compared to the commercial vaccine as is (F-HA). We now evaluated vaccine efficacy in different strains and sexes of mice and determined the role of innate immunity in the mechanism of action of the CCS/C adjuvant by testing the response of mice deficient in Toll-like receptors or the TLR/IL-1 adaptor protein MyD88 following immunization with CCS/C-HA vs. F-HA. Although TLR2- and TLR4-deficient mice responded to F-HA immunization, F-HA immunization failed to engender a significant immune response in the absence of MyD88. In contrast, immunization with the CCS/C-HA vaccine overcame the requirement for MyD88 in the response to the commercial vaccine and improved the immune responses and seroconversion rates in all strains of mice tested, including those deficient in TLR2 and TLR4.

Vaccination against cocaine using a modifiable dendrimer nanoparticle platform

Pharmacological therapies for the treatment of cocaine addiction have had disappointing efficacy, and the lack of recent developments in the clinical care of cocaine-addicted patients indicates a need for novel treatment strategies. Recent studies have shown that vaccination against cocaine to elicit production of antibodies that reduce concentrations of free drug in the blood is a promising method to protect against the effects of cocaine and reduce rates of relapse. However, the poorly immunogenic nature of cocaine remains a major hurdle to active immunization. Therefore, we hypothesized that strategies to increase targeted exposure of cocaine to the immune system may produce a more effective vaccine. To specifically direct an immune response against cocaine, in the present study we have conjugated a cocaine analog to a dendrimer-based nanoparticle carrier with MHC II-binding moieties that previously has been shown to activate antigen-presenting cells necessary for antibody production. This strategy produced a rapid, prolonged, and high affinity anti-cocaine antibody response without the need for an adjuvant. Surprisingly, additional evaluation using multiple adjuvant formulations in two strains of inbred mice found adjuvants were either functionally redundant or deleterious in the vaccination against cocaine using this platform. The use of conditioned place preference in rats after administration of this vaccine provided proof of concept for the ability of this vaccine to diminish cocaine reward. Together these data demonstrate the intrinsic efficacy of an immune-targeting dendrimer-based cocaine vaccine, with a vast potential for design of future vaccines against other poorly immunogenic antigens by substitution of the conjugated cargo.

An Immunomodulatory Gallotanin-Rich Fraction From Caesalpinia spinosa Enhances the Therapeutic Effect of Anti-PD-L1 in Melanoma

PD-1/PD-L1 pathway plays a role in inhibiting immune response. Therapeutic antibodies aimed at blocking the PD-1/PD-L1 interaction have entered clinical development and have been approved for a variety of cancers. However, the clinical benefits are reduced to a group of patients. The research in combined therapies, which allow for a greater response, is strongly encouraging. We previously characterized a polyphenol-rich extract from Caesalpinia spinosa (P2Et) with antitumor activity in both melanoma and breast carcinoma, as well as immunomodulatory activity. We hypothesize that the combined treatment with P2Et and anti-PD-L1 can improve the antitumor response through an additive antitumor effect. We investigated the antitumor and immunomodulatory activity of P2Et and anti-PD-L1 combined therapy in B16-F10 melanoma and 4T1 breast carcinoma. We analyzed tumor growth, hematologic parameters, T cell counts, cytokine expression, and T cell cytotoxicity. In the melanoma model, combined P2Et and anti-PD-L1 therapy has the following effects: decrease in tumor size; increase in the number of activated CD4⁺ and CD8⁺ T cells; decrease in the number of suppressor myeloid cells; increase in PD-L1 expression; decrease in the frequency of CD8⁺ T cell expressing PD-1; improvement in the cytotoxic activity of T cells; and increase in the IFN γ secretion. In the breast cancer model, P2Et and PD-L1 alone or in combination show antitumor effect with no clear additive effect. This study shows that combined therapy of P2Et and anti-PD-L1 can improve antitumor response in a melanoma model by activating the immune response and neutralizing immunosuppressive mechanisms.

Towards middle-up analysis of polyclonal antibodies: subclass-specific N-glycosylation profiling of murine immunoglobulin G (IgG) by means of HPLC-MS

In recent years, advanced HPLC-MS strategies based on intact protein (“top-down”) or protein subunit (“middle-up/middle-down”) analysis have been implemented for the characterization of therapeutic monoclonal antibodies. Here, we assess feasibility of middle-up/middle-down analysis for polyclonal IgGs exhibiting extensive sequence variability. Specifically, we addressed IgGs from mouse, representing an important model system in immunological investigations. To obtain Fc/2 portions as conserved subunits of IgGs, we made use of the bacterial protease SpeB. For this purpose, we initially determined SpeB cleavage sites in murine IgGs. The resulting Fc/2 portions characteristic of different subclasses were subsequently analysed by ion-pair reversed-phase HPLC hyphenated to high-resolution mass spectrometry. This enabled simultaneous relative quantification of IgG subclasses and their N-glycosylation variants, both of which influence IgG effector functions. To assess method capabilities in an immunological context, we applied the analytical workflow to polyclonal antibodies obtained from BALB/c mice immunized with the grass pollen allergen Phl p 6. The study revealed a shift in IgG subclasses and Fc-glycosylation patterns in total and antigen-specific IgGs from different mouse cohorts, respectively. Eventually, Fc/2 characterization may reveal other protein modifications including oxidation, amino acid exchanges, and C-terminal lysine, and may thus be implemented for quality control of functional antibodies.

Influence of the Host and Parasite Strain on the Immune Response During Toxoplasma Infection

Toxoplasma gondii is an exceptionally successful parasite that infects a very broad host range, including humans, across the globe. The outcome of infection differs remarkably between hosts, ranging from acute death to sterile infection. These differential disease patterns are strongly influenced by both host- and parasite-specific genetic factors. In this review, we discuss how the clinical outcome of toxoplasmosis varies between hosts and the role of different immune genes and parasite virulence factors, with a special emphasis on Toxoplasma-induced ileitis and encephalitis.

ILC2-driven innate immune checkpoint mechanism antagonizes NK cell antimetastatic function in the lung

Metastasis constitutes the primary cause of cancer-related deaths, with the lung being a commonly affected organ. We found that activation of lung-resident group 2 innate lymphoid cells (ILC2s) orchestrated suppression of natural killer (NK) cell-mediated innate antitumor immunity, leading to increased lung metastases and mortality. Using multiple models of lung metastasis, we show that interleukin (IL)-33-dependent ILC2 activation in the lung is involved centrally in promoting tumor burden. ILC2-driven innate type 2 inflammation is accompanied by profound local suppression of interferon-γ production and cytotoxic function of lung NK cells. ILC2-dependent suppression of NK cells is elaborated via an innate regulatory mechanism, which is reliant on IL-5-induced lung eosinophilia, ultimately limiting the metabolic fitness of NK cells. Therapeutic targeting of IL-33 or IL-5 reversed NK cell suppression and alleviated cancer burden. Thus, we reveal an important function of IL-33 and ILC2s in promoting tumor metastasis via their capacity to suppress innate type 1 immunity.

Potential lung attack and lethality generated by EpCAM-specific CAR-T cells in immunocompetent mouse models

The tumoricidal efficiency of human CAR-T cells is generally evaluated using immune-deficient mouse models; however, due to their immune-incompetency and the species-specific reactivity of a target antigen, these models are problematic to imitate CAR-T-induced adverse effects in the clinic. Epithelial cell adhesion molecule (EpCAM) is a tumor-associated antigen overtly presented on the cell surface of various carcinomas, making it an attractive target for CAR-T therapy. Here, we developed an anti-mouse EpCAM CAR to evaluate its safety and efficacy in immunocompetent mouse models. As previously reported for their human equivalents, murine EpCAM CAR-T cells exhibit promising anti-tumor efficacy in vitro and in vivo. However, after CAR-T infusion, various dose-depended toxicities including body weight loss, cytokine-release syndrome (CRS), and death were observed in both tumor-bearing and tumor-free mice. Pathological examination revealed unexpected and severe pulmonary immunopathology due to basal EpCAM expression in normal lung. While our study validates EpCAM CAR-T's potent anti-tumor efficacy, it also reveals that EpCAM CAR-T cells used for the treatment of solid tumors may cause lethal toxicity and should, therefore, be evaluated in patients with caution.

Diversity Outbred Mice Reveal the Quantitative Trait Locus and Regulatory Cells of HER2 Immunity

The genetic basis and mechanisms of disparate antitumor immune response was investigated in Diversity Outbred (DO) F1 mice that express human HER2. DO mouse stock samples nearly the entire genetic repertoire of the species. We crossed DO mice with syngeneic HER2 transgenic mice to study the genetics of an anti-self HER2 response in a healthy outbred population. Anti-HER2 IgG was induced by Ad/E2TM or naked pE2TM, both encoding HER2 extracellular and transmembrane domains. The response of DO F1 HER2 transgenic mice was remarkably variable. Still, immune sera inhibited HER2+ SKBR3 cell survival in a dose-dependent fashion. Using DO quantitative trait locus (QTL) analysis, we mapped the QTL that influences both total IgG and IgG2(a/b/c) Ab response to either Ad/E2TM or pE2TM. QTL from these four datasets identified a region in chromosome 17 that was responsible for regulating the response. A/J and NOD segments of genes in this region drove elevated HER2 Ig levels. This region is rich in MHC-IB genes, several of which interact with inhibitory receptors of NK cells. (B6xA/J)F1 and (B6xNOD)F1 HER2 transgenic mice received Ad/E2TM after NK cell depletion, and they produced less HER2 IgG, demonstrating positive regulatory function of NK cells. Depletion of regulatory T cells enhanced response. Using DO QTL analysis, we show that MHC-IB reactive NK cells exert positive influence on the immunity, countering negative regulation by regulatory T cells. This new, to our knowledge, DO F1 platform is a powerful tool for revealing novel immune regulatory mechanisms and for testing new interventional strategies.

CD4+CD25+ T Cells are Essential for Behavioral Effects of Lactobacillus rhamnosus JB-1 in Male BALB/c mice

Over the past decade there has been increasing interest in the involvement of the microbiota-gut-brain axis in mental health. However, there are major gaps in our knowledge regarding the complex signaling systems through which gut microbes modulate the CNS. The immune system is a recognized mediator in the bidirectional communication continuously occurring between gut and brain. We previously demonstrated that Lactobacillus rhamnosus JB-1 (JB-1), a bacterial strain that has anxiolytic- and antidepressant-like effects in mice, modulates the immune system through induction of immunosuppressive T regulatory cells. Here we examined a potential causal relationship between JB-1 induced regulatory T cells and the observed effects on behaviour. We found that depletion of regulatory T cells, via treatment with monoclonal antibody against CD25, inhibited the antidepressant- and anxiolytic-like effects induced by 4-week oral administration of JB-1 in mice. Ly6C^hi monocytes were found to be decreased in JB-1 fed mice with intact regulatory T cells, but not in JB-1 fed mice following depletion. Furthermore, adoptive transfer of CD4⁺CD25⁺ cells, from JB-1 treated donor mice, but not from controls, induced antidepressant- and anxiolytic-like effects in recipient mice. Ly6C^hi monocytes were also significantly decreased in mice receiving CD4⁺CD25⁺ cells from JB1 fed donors. This study identifies cells within the CD4⁺CD25⁺ population, most likely regulatory T cells, as both necessary and sufficient in JB-1-induced antidepressant- and anxiolytic-like effects in mice, providing novel mechanistic insight into microbiota-gut-brain communication in addition to highlighting the potential for immunotherapy in psychiatric disorders.

Mite Burden and Immunophenotypic Response to Demodex musculi in Swiss Webster, BALB/c, C57BL/6, and NSG Mice

Detection methods for Demodex musculi were historically unreliable, and testing was rarely performed because its prevalence in laboratory mice was underestimated. Although infestations are unapparent in most mouse strains, D. musculi burdens are higher and clinical signs detected in various immunodeficient strains. The parasite's influence on the immune system of immunocompetent mice is unknown. We characterized mite burden (immunocompetent and immunodeficient strains) and immunologic changes (immunocompetent strains only) in naïve Swiss Webster (SW; outbred), C57BL/6NCrl (B6; Th1 responder), BALB/cAnNCrl (BALB/c; Th2 responder) and NOD. Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG; immunodeficient) mice after exposure to Demodex-infested NSG mice. Infested and uninfested age-matched mice of each strain (n = 5) were euthanized 14, 28, 56, and 112 d after exposure. Mite burden was determined through PCR analysis and skin histopathology; B-cell and CD4+ and CD8+ T-cell counts and activation states (CD25 and CD69) were evaluated by using flow cytometry; CBC counts were performed; and serum IgE levels were measured by ELISA. Mite burden and PCR copy number correlated in NSG mice, which had the highest mite burden, but not in immunocompetent strains. Infested immunocompetent animals developed diffuse alopecia by day 112, and both BALB/c and C57BL/6 mice had significantly increased IgE levels. These findings aligned with the skewed Th1 or Th2 immunophenotype of each strain. BALB/c mice mounted the most effective host response, resulting in the lowest mite burden of all immunocompetent strains at 112 d after infestation without treatment. Clinically significant hematologic abnormalities were absent and immunophenotype was unaltered in immunocompetent animals. Topical treat- ment with imidacloprid-moxidectin (weekly for 8 wk) was effective at eradicating mites by early as 7 d after treatment. IgE levels decreased substantially in infested BALB/c mice after treatment. These findings demonstrate a need for D. musculi surveillance in mouse colonies, because the infestation may influence the use of infested mice in select studies.

Regulating T-cell differentiation through the polyamine spermidine

BACKGROUND

The cross-talk between the host and its microbiota plays a key role in the promotion of health. The production of metabolites such as polyamines by intestinal-resident bacteria is part of this symbiosis shaping host immunity. The polyamines putrescine, spermine, and spermidine are abundant within the gastrointestinal tract and might substantially contribute to gut immunity.

OBJECTIVE

We aimed to characterize the polyamine spermidine as a modulator of T-cell differentiation and function.

METHODS

Naive T cells were isolated from wild-type mice or cord blood from healthy donors and submitted to polarizing cytokines, with and without spermidine treatment, to evaluate CD4⁺ T-cell differentiation in vitro. Moreover, mice were subjected to oral supplementation of spermidine, or its precursor l-arginine, to assess the frequency and total numbers of regulatory T (Treg) cells in vivo.

RESULTS

Spermidine modulates CD4⁺ T-cell differentiation in vitro, preferentially committing naive T cells to a regulatory phenotype. After spermidine treatment, activated T cells lacking the autophagy gene Atg5 fail to upregulate Foxp3 to the same extent as wild-type cells. These results indicate that spermidine's polarizing effect requires an intact autophagic machinery. Furthermore, dietary supplementation with spermidine promotes homeostatic differentiation of Treg cells within the gut and reduces pathology in a model of T-cell transfer-induced colitis.

CONCLUSION

Altogether, our results highlight the beneficial effects of spermidine, or l-arginine, on gut immunity by promoting Treg cell development.

Immunomodulatory effects of pevonedistat, a NEDD8-activating enzyme inhibitor, in chronic lymphocytic leukemia-derived T cells

Novel targeted agents used in therapy of lymphoid malignancies, such as inhibitors of B-cell receptor-associated kinases, are recognized to have complex immune-mediated effects. NEDD8-activating enzyme (NAE) has been identified as a tractable target in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma. We and others have shown that pevonedistat (TAK-924), a small-molecule inhibitor of NAE, abrogates NF-κB signaling in malignant B cells. However, NF-κB pathway activity is indispensable in immune response, and T-cell function is altered in patients with CLL. Using T cells derived from patients with CLL, we demonstrate that although targeting NAE results in markedly differential expression of NF-κB-regulated genes and downregulation of interleukin (IL)-2 signaling during T-cell activation, T cells evade apoptosis. Meanwhile, NAE inhibition favorably modulates polarization of T cells in vitro, with decreased T_reg differentiation and a shift toward T_H1 phenotype, accompanied by increased interferon-γ production. These findings were recapitulated in vivo in immunocompetent mouse models. T cells exposed to pevonedistat in washout experiments, informed by its human pharmacokinetic profile, recover NAE activity, and maintain their response to T-cell receptor stimulation and cytotoxic potential. Our data shed light on the potential immune implications of targeting neddylation in CLL and lymphoid malignancies.

Leptin Elicits In Vivo Eosinophil Migration and Activation: Key Role of Mast Cell-Derived PGD2

Eosinophils are key regulators of adipose tissue homeostasis, thus characterization of adipose tissue-related molecular factors capable of regulating eosinophil activity is of great interest. Leptin is known to directly activate eosinophils in vitro, but leptin ability of inducing in vivo eosinophilic inflammatory response remains elusive. Here, we show that leptin elicits eosinophil influx as well as its activation, characterized by increased lipid body biogenesis and LTC₄ synthesis. Such leptin-triggered eosinophilic inflammatory response was shown to be dependent on activation of the mTOR signaling pathway, since it was (i) inhibited by rapamycin pre-treatment and (ii) reduced in PI3K-deficient mice. Local infiltration of activated eosinophils within leptin-driven inflammatory site was preceded by increased levels of classical mast cell-derived molecules, including TNFα, CCL5 (RANTES), and PGD₂. Thus, mice were pre-treated with a mast cell degranulating agent compound 48/80 which was capable to impair leptin-induced PGD₂ release, as well as eosinophil recruitment and activation. In agreement with an indirect mast cell-driven phenomenon, eosinophil accumulation induced by leptin was abolished in TNFR-1 deficient and also in HQL-79-pretreated mice, but not in mice pretreated with neutralizing antibodies against CCL5, indicating that both typical mast cell-driven signals TNFα and PGD₂, but not CCL5, contribute to leptin-induced eosinophil influx. Distinctly, leptin-induced eosinophil lipid body (lipid droplet) assembly and LTC₄ synthesis appears to depend on both PGD₂ and CCL5, since both HQL-79 and anti-CCL5 treatments were able to inhibit these eosinophil activation markers. Altogether, our data show that leptin triggers eosinophilic inflammation in vivo via an indirect mechanism dependent on activation of resident mast cell secretory activity and mediation by TNFα, CCL5, and specially PGD₂.

Genetic Variation in the Magnitude and Longevity of the IgG Subclass Response to a Diphtheria-Tetanus-Acellular Pertussis (DTaP) Vaccine in Mice

The type of IgG subclasses induced by vaccination is an important determinant of vaccine efficacy because the IgG subclasses vary in their biological function. The goal of this study was to determine the influence of the genetic background on the production and duration of vaccine-induced IgG subclasses. IgG1, IgG2b, and IgG3 titers against diphtheria toxoid (DT), pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (Prn) were measured in mice from 28 different inbred and wild-derived strains vaccinated with an aluminum hydroxide-adjuvanted DTaP vaccine. The titers and duration of vaccine-specific IgG subclass responses were different among mouse strains, indicating that genetic factors contribute to this variation. Statistical associations were used to identify potential mechanisms that contribute to antibody production and longevity. This analysis showed that the mechanisms guiding the magnitude of antibody production were antigen-dependent for IgG1 but antigen-independent for IgG2b and IgG3. However, the mechanisms driving the longevity of antibody titers were antigen-independent for IgG1, IgG2b, and IgG3. The ratio of IgG1 and IgG3 titers identified Th1 and Th2-prone mouse strains. TLR4-deficient C3H/HeJ mice had an enhanced IgG1 response compared with C3H/HeOuJ mice with intact TLR4. This work demonstrates that the genetic background contributes significantly to the magnitude and longevity of vaccine-induced IgG1, IgG2b, and IgG3 titers in mice.

Disruption of sialic acid metabolism drives tumor growth by augmenting CD8+ T cell apoptosis

Sialylated glycan structures are known for their immunomodulatory capacities and their contribution to tumor immune evasion. However, the role of aberrant sialylation in colorectal cancer and the consequences of complete tumor desialylation on anti-tumor immunity remain unstudied. Here, we report that CRISPR/Cas9-mediated knock out of the CMAS gene, encoding a key enzyme in the sialylation pathway, in the mouse colorectal cancer MC38 cell line completely abrogated cell surface expression of sialic acids (MC38-Sia^null ) and, unexpectedly, significantly increased in vivo tumor growth compared to the control MC38-MOCK cells. This enhanced tumor growth of MC38-Sia^null cells could be attributed to decreased CD8⁺ T cell frequencies in the tumor microenvironment only, as immune cell frequencies in tumor-draining lymph nodes remained unaffected. In addition, MC38-Sia^null cells were able to induce CD8⁺ T cell apoptosis in an antigen-independent manner. Moreover, low CMAS gene expression correlated with reduced recurrence-free survival in a human colorectal cancer cohort, supporting the clinical relevance of our work. Together, these results demonstrate for the first time a detrimental effect of complete tumor desialylation on colorectal cancer tumor growth, which greatly impacts the design of novel cancer therapeutics aimed at altering the tumor glycosylation profile.

Allergic Asthma Favors Brucella Growth in the Lungs of Infected Mice

Allergic asthma is a chronic Th2 inflammatory disease of the lower airways affecting a growing number of people worldwide. The impact of infections and microbiota composition on allergic asthma has been investigated frequently. Until now, however, there have been few attempts to investigate the impact of asthma on the control of infectious microorganisms and the underlying mechanisms. In this work, we characterize the consequences of allergic asthma on intranasal (i.n.) infection by Brucella bacteria in mice. We observed that i.n. sensitization with extracts of the house dust mite Dermatophagoides farinae or the mold Alternaria alternata (Alt) significantly increased the number of Brucella melitensis, Brucella suis, and Brucella abortus in the lungs of infected mice. Microscopic analysis showed dense aggregates of infected cells composed mainly of alveolar macrophages (CD11c+ F4/80+ MHCII+) surrounded by neutrophils (Ly-6G+). Asthma-induced Brucella susceptibility appears to be dependent on CD4+ T cells, the IL-4/STAT6 signaling pathway and IL-10, and is maintained in IL-12- and IFN-γR-deficient mice. The effects of the Alt sensitization protocol were also tested on Streptococcus pneumoniae and Mycobacterium tuberculosis pulmonary infections. Surprisingly, we observed that Alt sensitization strongly increases the survival of S. pneumoniae infected mice by a T cell and STAT6 independent signaling pathway. In contrast, the course of M. tuberculosis infection is not affected in the lungs of sensitized mice. Our work demonstrates that the impact of the same allergic sensitization protocol can be neutral, negative, or positive with regard to the resistance of mice to bacterial infection, depending on the bacterial species.

Invariant Natural Killer T Cell Subsets-More Than Just Developmental Intermediates

Invariant natural killer T (iNKT) cells are a CD1d-restricted T cell population that can respond to lipid antigenic stimulation within minutes by secreting a wide variety of cytokines. This broad functional scope has placed iNKT cells at the frontlines of many kinds of immune responses. Although the diverse functional capacities of iNKT cells have long been acknowledged, only recently have distinct iNKT cell subsets, each with a marked functional predisposition, been appreciated. Furthermore, the subsets can frequently occupy distinct niches in different tissues and sometimes establish long-term tissue residency where they can impact homeostasis and respond quickly when they sense perturbations. In this review, we discuss the developmental origins of the iNKT cell subsets, their localization patterns, and detail what is known about how different subsets specifically influence their surroundings in conditions of steady and diseased states.