AsialoGM1+CD8+ central memory-type T cells in unimmunized mice as novel immunomodulator of IFN- -dependent type 1 immunity

Poly-γ-glutamic acid nanoparticles as adjuvant and antigen carrier system for cancer vaccination

Vaccination is an innovative strategy for cancer treatment by leveraging various components of the patients' immunity to boost an anti-tumor immune response. Rationally designed nanoparticles are well suited to maximize cancer vaccination by the inclusion of immune stimulatory adjuvants. Also, nanoparticles might control the pharmacokinetics and destination of the immune potentiating compounds. Poly-γ-glutamic acid (γ-PGA) based nanoparticles (NPs), which have a natural origin, can be easily taken up by dendritic cells (DCs), which leads to the secretion of cytokines which ameliorates the stimulation capacity of T cells. The intrinsic adjuvant properties and antigen carrier properties of γ-PGA NPs have been the focus of recent investigations as they can modulate the tumor microenvironment, can contribute to systemic anti-tumor immunity and subsequently inhibit tumor growth. This review provides a comprehensive overview on the potential of γ-PGA NPs as antigen carriers and/or adjuvants for anti-cancer vaccination.

Inhibition of IL-12 heterodimers impairs TLR9-mediated prevention of early mouse plasmacytoma cell growth

Introduction

Natural prevention of cancer development depends on an efficient immunosurveillance that may be modulated by environmental factors, including infections. Innate lymphoid cytotoxic cells have been shown to play a major role in this immunosurveillance. Interleukin-12 (IL-12) has been suggested to be a key factor in the activation of innate cytotoxic cells after infection, leading to the enhancement of cancer immunosurveillance.

Methods

The aim of this work was to analyze in mouse experimental models by which mechanisms the interaction between infectious agent molecules and the early innate responses could enhance early inhibition of cancer growth and especially to assess the role of IL-12 by using novel antibodies specific for IL-12 heterodimers.

Results

Ligation of toll-like receptor (TLR)9 by CpG-protected mice against plasmacytoma TEPC.1033.C2 cell early growth. This protection mediated by innate cytolytic cells was strictly dependent on IL-12 and partly on gamma-interferon. Moreover, the protective effect of CpG stimulation, and to a lesser extent of TLR3 and TLR7/8, and the role of IL-12 in this protection were confirmed in a model of early mesothelioma AB1 cell growth.

Discussion

These results suggest that modulation of the mouse immune microenvironment by ligation of innate receptors deeply modifies the efficiency of cancer immunosurveillance through the secretion of IL-12, which may at least partly explain the inhibitory effect of previous infections on the prevalence of some cancers.

Natural killer cells and dendritic epidermal γδ T cells orchestrate type 1 conventional DC spatiotemporal repositioning toward CD8+ T cells

Successful immune responses rely on a regulated delivery of the right signals to the right cells at the right time. Here we show that natural killer (NK) and dendritic epidermal γδ T cells (DETCs) use similar mechanisms to spatiotemporally orchestrate conventional type 1 dendritic cell (cDC1) functions in the spleen, skin, and its draining lymph nodes (dLNs). Upon MCMV infection in the spleen, cDC1 clusterize with activated NK cells in marginal zones. This XCR1-dependent repositioning of cDC1 toward NK cells allows contact delivery of IL-12 and IL-15/IL-15Rα by cDC1, which is critical for NK cell responses. NK cells deliver granulocyte-macrophage colony-stimulating factor (GM-CSF) to cDC1, guiding their CCR7-dependent relocalization into the T cell zone. In MCMV-infected skin, XCL1-secreting DETCs promote cDC1 migration from the skin to the dLNs. This XCR1-dependent licensing of cDC1 both in the spleen and skin accelerates antiviral CD8⁺ T cell responses, revealing an additional mechanism through which cDC1 bridge innate and adaptive immunity.

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Upon viral infection in the spleen, NK cells clusterize with cDC1 in the marginal zone

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This XCL1/XCR1-dependent interaction allows mutual delivery of activating signals

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NK cell GM-CSF directs cDC1 migration to T cell zone boosting CD8+ T cell priming

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In the skin, DETCs contact cDC1 via XCL1/XCR1 to promote antiviral CD8+ T cell priming

Mucosal Vaccination Primes NK Cell-Dependent Development of CD8+ T Cells Against Pulmonary Brucella Infection

Past studies with the live, double-mutant B. abortus (znBAZ) strain resulted in nearly complete protection of mice against pulmonary challenge with wild-type (wt) Brucella via a dominant CD8+ T cell response. To understand the contribution innate immune cells in priming CD8+ T cell responses, mice were nasally dosed with wt B. abortus, smooth vaccine strain 19 (S19), or znBAZ, and examined for innate immune cell activation. Flow cytometric analysis revealed that znBAZ, but not wt B. abortus nor S19 infection, induces up to a 5-fold increase in the frequency of IFN-γ-producing NK cells in mouse lungs. These NK cells express increased CXCR3 and Ki67, indicating their recruitment and proliferation subsequent to znBAZ infection. Their activation status was augmented noted by the increased NKp46 and granzyme B, but decreased NKG2A expression. Further analysis demonstrated that both lung caspase-1+ inflammatory monocytes and monocyte-derived macrophages secrete chemokines and cytokines responsible for NK cell recruitment and activation. Moreover, neutralizing IL-18, an NK cell-activating cytokine, reduced the znBAZ-induced early NK cell response. NK cell depletion also significantly impaired lung dendritic cell (DC) activation and migration to the lower respiratory lymph nodes (LRLNs). Both lung DC activation and migration to LRLNs were significantly impaired in NK cell-depleted or IFN-γ-/- mice, particularly the CD11b+ and monocytic DC subsets. Furthermore, znBAZ vaccination significantly induced CD8+ T cells, and upon in vivo NK cell depletion, CD8+ T cells were reduced 3-fold compared to isotype-treated mice. In summary, these data show that znBAZ induces lung IFN-γ+ NK cells, which plays a critical role in influencing lung DC activation, migration, and promoting protective CD8+ T cell development.

Asialo GM1-positive liver-resident CD8 T cells that express CD44 and LFA-1 are essential for immune clearance of hepatitis B virus

Persistent hepatitis B virus (HBV) infection results in chronic liver diseases that may progress to chronic hepatitis, liver cirrhosis, and subsequent hepatocellular carcinoma. Previous studies demonstrated that adaptive immunity, in particular CD8 T cells, is critical in HBV elimination. Recent studies have revealed a distinct tissue-localized T cell lineage, tissue-resident memory (TRM) cells, that is crucial for protective immunity in peripheral tissues. In this study, we showed that treatment with an anti-asialo GM1 (ASGM1) antibody (Ab), which depletes NK cells, led to impairment of HBV clearance in a mouse animal model. Unexpectedly, the ability to clear HBV was not significantly impaired in NFIL3 KO mice, which are deficient in NK cells, implying that other non-NK ASGM1-positive immune cells mediate HBV clearance. We isolated intrahepatic ASGM1-positive cells from NFIL3 KO mice and analyzed the immune phenotype of these cells. Our results demonstrated a distinct population of CD44⁺ LFA-1^hi CD8 T cells that were the major intrahepatic ASGM1-positive immune cells in NFIL3 KO mice. Importantly, transcriptome analysis revealed that these ASGM1-positive CD8 T cells had distinct gene profiles and shared a similar core gene signature with TRM cells. In addition to both transcriptional and phenotypic liver residency characteristics, ASGM1-positive CD8 T cells were able to home to and be retained in the liver after adoptive transfer. Taken together, our study results indicate that these ASGM1-positive liver-resident CD8 T cells are the major effector immune cells mediating anti-HBV immunity.

Eomesodermin driven IL-10 production in effector CD8+ T cells promotes a memory phenotype

CD8⁺ T cell differentiation is controlled by the transcription factors T-bet and Eomesodermin, in concert with the cytokines IL-2, IL-10 and IL-12. Among these pathways, the mechanisms by which T-box proteins and IL-10 interact to promote a memory T cell fate remain poorly understood. Here, we show that Eomes and IL-10 drive a central memory phenotype in murine CD8⁺ T cells. Eomes expression led to increased IL-10 expression by the effector CD8⁺ T cells themselves as well as an increase in the level of the lymph node homing selectin CD62L. Furthermore, exposure of effector CD8⁺ T cells to IL-10 maintained CD62L expression levels in culture. Thus, Eomes promotes a step-wise transition of effector T cells towards a memory phenotype, synergizing with IL-10 to enhance the expression of CD62L. The early augmentation of lymph node homing markers by Eomes may facilitate the retention of effector T cells in the relatively low inflammatory milieu of the secondary lymphoid organs that promotes central memory development.

NK Cells Help Induce Anti-Hepatitis B Virus CD8+ T Cell Immunity in Mice

Although recent clinical studies demonstrate that NK cell function is impaired in hepatitis B virus (HBV)-persistent patients, whether or how NK cells play a role in anti-HBV adaptive immunity remains to be explored. Using a mouse model mimicking acute HBV infection by hydrodynamic injection of an HBV plasmid, we observed that although serum hepatitis B surface Ag and hepatitis B envelope Ag were eliminated within 3 to 4 wk, HBV might persist for >8 wk in CD8(-/-) mice and that adoptive transfer of anti-HBV CD8(+) T cells restored the ability to clear HBV in HBV-carrier Rag1(-/-) mice. These results indicate that CD8(+) T cells are critical in HBV elimination. Furthermore, NK cells increased IFN-γ production after HBV plasmid injection, and NK cell depletion led to significantly increased HBV persistence along with reduced frequency of hepatitis B core Ag-specific CD8(+) T cells. Adoptive transfer of IFN-γ-sufficient NK cells restored donor CD8(+) T cell function, indicating that NK cells positively regulated CD8(+) T cells via secreting IFN-γ. We also observed that NK cell depletion correlated with decreased effector memory CD8(+) T cell frequencies. Importantly, adoptive transfer experiments showed that NK cells were involved in anti-HBV CD8(+) T cell recall responses. Moreover, DX5(+)CD49a(-) conventional, but not DX5(-)CD49a(+) liver-resident, NK cells were involved in improving CD8(+) T cell responses against HBV. Overall, the current study reveals that NK cells, especially DX5(+)CD49a(-) conventional NK cells, promote the antiviral activity of CD8(+) T cell responses via secreting IFN-γ in a mouse model mimicking acute HBV infection.

A novel murine cytomegalovirus vaccine vector protects against Mycobacterium tuberculosis

Tuberculosis remains a global health problem so that a more effective vaccine than bacillus Calmette–Guérin is urgently needed. Cytomegaloviruses persist lifelong in vivo and induce powerful immune and increasing (“inflationary”) responses, making them attractive vaccine vectors. We have used an m1–m16-deleted recombinant murine CMV (MCMV) expressing Mycobacterium tuberculosis Ag 85A to show that infection of mice with this recombinant significantly reduces the mycobacterial load after challenge with M. tuberculosis, whereas control empty virus has a lesser effect. Both viruses induce immune responses to H-2^d–restricted epitopes of MCMV pp89 and M18 Ags characteristic of infection with other MCMVs. A low frequency of 85A-specific memory cells could be revealed by in vivo or in vitro boosting or after challenge with M. tuberculosis. Kinetic analysis of M. tuberculosis growth in the lungs of CMV-infected mice shows early inhibition of M. tuberculosis growth abolished by treatment with NK-depleting anti–asialo ganglio-N-tetraosylceramide Ab. Microarray analysis of the lungs of naive and CMV-infected mice shows increased IL-21 mRNA in infected mice, whereas in vitro NK assays indicate increased levels of NK activity. These data indicate that activation of NK cells by MCMV provides early nonspecific protection against M. tuberculosis, potentiated by a weak 85A-specific T cell response, and they reinforce the view that the innate immune system plays an important role in both natural and vaccine-induced protection against M. tuberculosis.

Plasmid vector-linked maturation of natural killer (NK) cells is coupled to antigen-dependent NK cell activation during DNA-based immunization in mice

Plasmid DNA vaccines serve in a wide array of applications ranging from prophylactic vaccines to potential therapeutic tools against infectious diseases and cancer. In this study, we analyzed the mechanisms underlying the activation of natural killer (NK) cells and their potential role in adaptive immunity during DNA-based immunization against hepatitis B virus surface antigen in mice. We observed that the mature Mac-1(+) CD27(-) NK cell subset increased in the liver of mice early after DNA injection, whereas the number of the less mature Mac-1(+) CD27(+) NK cells in the liver and spleen was significantly reduced. This effect was attributed to bacterial sequences present in the plasmid backbone rather than to the encoded antigen and was not observed in immunized MyD88-deficient mice. The activation of NK cells by plasmid-DNA injection was associated with an increase in their effector functions that depended on the expressed antigen. Maturation of NK cells was abrogated in the absence of T cells, suggesting that cross talk exists between NK cells and antigen-specific T cells. Taken together, our data unravel the mechanics of plasmid vector-induced maturation of NK cells and plasmid-encoded antigen-dependent activation of NK cells required for a crucial role of NK cells in DNA vaccine-induced immunogenicity.

Recipient lymphocyte infusion in MHC-matched bone marrow chimeras induces a limited lymphohematopoietic host-versus-graft reactivity but a significant antileukemic effect mediated by CD8+ T cells and natural killer cells

BACKGROUND

Challenge of MHC-mismatched murine bone marrow chimeras with recipient-type lymphocytes (recipient lymphocyte infusion) produces antileukemic responses in association with rejection of donor chimerism. In contrast, MHC-matched chimeras resist eradication of donor chimerism by recipient lymphocyte infusion. Here, we investigated lymphohematopoietic host-versus-graft reactivity and antileukemic responses in the MHC-matched setting, which is reminiscent of the majority of clinical transplants.

DESIGN AND METHODS

We challenged C3H→AKR radiation chimeras with AKR-type splenocytes (i.e. recipient lymphocyte infusion) and BW5147.3 leukemia cells. We studied the kinetics of chimerism using flowcytometry and the mechanisms involved in antileukemic effects using in vivo antibody-mediated depletion of CD8(+) T and NK cells, and intracellular cytokine staining.

RESULTS

Whereas control chimeras showed progressive evolution towards high-level donor T-cell chimerism, recipient lymphocyte infusion chimeras showed a limited reduction of donor chimerism with delayed onset and long-term preservation of lower-level mixed chimerism. Recipient lymphocyte infusion chimeras nevertheless showed a significant survival benefit after leukemia challenge. In vivo antibody-mediated depletion experiments showed that both CD8(+) T cells and NK cells contribute to the antileukemic effect. Consistent with a role for NK cells, the proportion of IFN-γ producing NK cells in recipient lymphocyte infusion chimeras was significantly higher than in control chimeras.

CONCLUSIONS

In the MHC-matched setting, recipient lymphocyte infusion elicits lymphohematopoietic host-versus-graft reactivity that is limited but sufficient to provide an antileukemic effect, and this is dependent on CD8(+) T cells and NK cells. The data indicate that NK cells are activated as a bystander phenomenon during lymphohematopoietic T-cell alloreactivity and thus support a novel type of NK involvement in anti-tumor responses after post-transplant adoptive cell therapy.

CD4+ and CD8+ T cells can act separately in tumour rejection after immunization with murine pneumotropic virus chimeric Her2/neu virus-like particles

Background

Immunization with murine pneumotropic virus virus-like particles carrying Her2/neu (Her2MPtVLPs) prevents tumour outgrowth in mice when given prophylactically, and therapeutically if combined with the adjuvant CpG. We investigated which components of the immune system are involved in tumour rejection, and whether long-term immunological memory can be obtained.

Methodology and Results

During the effector phase in BALB/c mice, only depletion of CD4⁺ and CD8⁺ in combination, with or without NK cells, completely abrogated tumour protection. Depletion of single CD4⁺, CD8⁺ or NK cell populations only had minor effects. During the immunization/induction phase, combined depletion of CD4⁺ and CD8⁺ cells abolished protection, while depletion of each individual subset had no or negligible effect. When tumour rejection was studied in knock-out mice with a C57Bl/6 background, protection was lost in CD4^−/−CD8^−/− and CD4^−/−, but not in CD8^−/− mice. In contrast, when normal C57Bl/6 mice were depleted of different cell types, protection was lost irrespective of whether only CD4⁺, only CD8⁺, or CD4⁺ and CD8⁺ cells in combination were eradicated. No anti-Her2/neu antibodies were detected but a Her2/neu-specific IFNγ response was seen. Studies of long-term memory showed that BALB/c mice could be protected against tumour development when immunized together with CpG as long as ten weeks before challenge.

Conclusion

Her2MPtVLP immunization is efficient in stimulating several compartments of the immune system, and induces an efficient immune response including long-term memory. In addition, when depleting mice of isolated cellular compartments, tumour protection is not as efficiently abolished as when depleting several immune compartments together.

Changes in mucosal homeostasis predispose NHE3 knockout mice to increased susceptibility to DSS-induced epithelial injury

BACKGROUND & AIMS

NHE3 is a target of inhibition by proinflammatory cytokines and pathogenic bacteria, an event contributing to diarrhea in infectious and idiopathic colitis. In mice, NHE3 deficiency leads to mild diarrhea, increased intestinal expression of interferon (IFN)-gamma, and distal colitis, suggesting its role in epithelial barrier homeostasis. Our aim was to investigate the role of NHE3 in maintaining mucosal integrity.

METHODS

Control or dextran sulfate sodium (DSS)-treated, 6- to 8-week-old wild-type (WT) and NHE3(-/-) mice were used for the experiments. Small intestines were dissected for further analysis.

RESULTS

NHE3(-/-) mice have elevated numbers of CD8alpha(+) T and natural killer cells in the intraepithelial lymphocytes and lamina propria lymphocytes compartments, representing the source of IFN-gamma. NHE3(-/-) mice display alterations in epithelial gene and protein expression patterns that predispose them to a high susceptibility to DSS, with accelerated mortality resulting from intestinal bleeding, hypovolemic shock, and sepsis, even at a very low DSS concentration. Microarray analysis and intestinal hemorrhage indicate that NHE3 deficiency predisposes mice to DSS-induced small intestinal injury, a segment never reported as affected by DSS, and demonstrate major differences in the colonic response to DSS challenge in WT and NHE3(-/-) mice. In NHE3(-/-) mice, broad-spectrum oral antibiotics or anti-asialo GM1 antibodies reduce the expression of IFN-gamma and iNOS to basal levels and delay but do not prevent severe mortality in response to DSS treatment.

CONCLUSIONS

These results suggest that NHE3 participates in mucosal responses to epithelial damage, acting as a modifier gene determining the extent of the gut inflammatory responses in the face of intestinal injury.

Essential role of Toll-like receptors for dendritic cell and NK1.1(+) cell-dependent activation of type 1 immunity by Lactobacillus pentosus strain S-PT84

Activation of type 1 immunity plays a critical role in host defense mechanisms against infectious disease and tumor. Lactic acid bacteria, existing in the gastrointestinal tract, are one of the powerful tools to induce a type-1-dominant immunity, which may improve Th2-dependent allergic diseases. In the present work, we found that an oral intake of Lactobacillus pentosus strain, S-PT84 into mice significantly enhanced NK activity of spleen cells in vivo. We further revealed that NK1.1 positive NK cells and NKT cells are responsible cells for producing IFN-gamma after stimulation with S-PT84 in vitro. S-PT84 induced IFN-gamma-producing cells through activation of IL-12 production by CD11c(+)DCs in Toll-like receptor (TLR) 2- and/or TLR4-dependent manner. Interestingly, direct interaction between DCs and NK1.1(+) cells was also essential for the IFN-gamma production in response to the S-PT84 stimulation. Therefore, we concluded that S-PT84 effectively promoted type 1 immunity through IL-12 and IFN-gamma which were produced by DCs and NK1.1(+) cells, respectively. Thus, S-PT84 would be a nice immune modulator for improving immunobalance, which plays a pivotal role for controlling allergy, infectious diseases and tumor.

TAP-1 indirectly regulates CD4+ T cell priming in Toxoplasma gondii infection by controlling NK cell IFN-gamma production

To investigate if transporter associated with antigen processing (TAP)–1 is required for CD8⁺ T cell–mediated control of Toxoplasma gondii in vivo, we compared the resistance of TAP-1^−/−, CD8^−/−, and wild-type (WT) mice to infection with the parasite. Unexpectedly, TAP-1^−/− mice displayed greater susceptibility than CD8^−/−, β₂-microglobulin^−/− (β₂m^−/−), or WT mice to infection with an avirulent parasite strain. The decreased resistance of the TAP-1^−/− mice correlated with a reduction in the frequency of activated (CD62L^low CD44^hi) and interferon (IFN)-γ–producing CD4⁺ T cells. Interestingly, infected TAP-1^−/− mice also showed reduced numbers of IFN-γ–producing natural killer (NK) cells relative to WT, CD8^−/−, or β₂m^−/− mice, and after NK cell depletion both CD8^−/− and WT mice succumbed to infection with the same kinetics as TAP-1^−/− animals and displayed impaired CD4⁺ T cell IFN-γ responses. Moreover, adoptive transfer of NK cells obtained from IFN-γ^+/+, but not IFN-γ^−/−, animals restored the CD4⁺ T cell response of infected TAP-1^−/− mice to normal levels. These results reveal a role for TAP-1 in the induction of IFN-γ–producing NK cells and demonstrate that NK cell licensing can influence host resistance to infection through its effect on cytokine production in addition to its role in cytotoxicity.

IFN-gamma prevents early perforin-granzyme-mediated destruction of kidney allografts by inducing donor class I products in the kidney

Interferon-gamma (Ifng) protects organ allografts: mouse kidney allografts lacking Ifng receptors rapidly fail with massive ischemic necrosis around days 5 to 7, reflecting microcirculation failure. We hypothesized that Ifng protects the graft by preventing perforin-granzyme-mediated cytotoxic damage to the microcirculation by inducing class Ia and/or Ib products. We transplanted kidney allografts lacking Ifng receptors into various knockout hosts. The necrosis/congestion phenotype did not require host B cells or IL-4 and IL-13 receptors, but required the T-cell alloresponse: it did not occur if the hosts were syngeneic or T-cell deficient. However, host perforin-granzyme mechanisms were required: no necrosis developed if hosts lacked either perforin or granzymes A and B. The ability of Ifng to protect the allograft required donor class I products: allografts lacking class I products due to Tap1 or beta2 microglobulin deficiency developed a similar necrosis-congestion phenotype at day 7 despite Ifng receptors being present. Thus when host cytotoxic T cells infiltrate organ allografts, Ifng prevents their perforin-granzyme mechanism from compromising the microcirculation by a mechanism requiring donor class Ia or Ib products. We propose that donor class Ia or Ib products are needed to trigger inhibitory receptors on effector T cells.