Tim-3 expression defines a novel population of dysfunctional T cells with highly elevated frequencies in progressive HIV-1 infection

MHC-mismatched chimerism is required for induction of transplantation tolerance in autoimmune nonobese diabetic recipients

In nonautoimmune recipients, induction of mixed and complete chimerism with hematopoietic progenitor cells from MHC (HLA)-matched or -mismatched donors are effective approaches for induction of organ transplantation immune tolerance in both animal models and patients. But it is still unclear whether this is the case in autoimmune recipients. With the autoimmune diabetic NOD mouse model, we report that, although mixed and complete MHC-mismatched chimerism provide immune tolerance to donor-type islet and skin transplants, neither mixed nor complete MHC-matched chimerism does. The MHC-mismatched chimerism not only tolerizes the de novo developed, but also the residual pre-existing host-type T cells in a mismatched MHC class II-dependent manner. In the MHC-mismatched chimeras, the residual host-type peripheral T cells appear to be anergic with upregulation of PD-1 and downregulation of IL-7Rα. Conversely, in the MHC-matched chimeras, the residual host-type peripheral T cells manifest both alloreactivity and autoreactivity; they not only mediate insulitis and sialitis in the recipient, but also reject allogeneic donor-type islet and skin grafts. Interestingly, transgenic autoreactive BDC2.5 T cells from Rag1(+/+), but not from Rag1(-/-), NOD mice show alloreactivity and mediate both insulitis and rejection of allografts. Taken together, MHC-mismatched, but not MHC-matched, chimerism can effectively provide transplantation immune tolerance in autoimmune recipients.

Galectin-9 is rapidly released during acute HIV-1 infection and remains sustained at high levels despite viral suppression even in elite controllers

Galectin-9 (Gal-9) is a β-galactosidase-binding lectin that promotes apoptosis, tissue inflammation, and T cell immune exhaustion, and alters HIV infection in part through engagement with the T cell immunoglobulin mucin domain-3 (Tim-3) receptor and protein disulfide isomerases (PDI). Gal-9 was initially thought to be an eosinophil attractant, but is now known to mediate multiple complex signaling events that affect T cells in both an immunosuppressive and inflammatory manner. To understand the kinetics of circulating Gal-9 levels during HIV infection we measured Gal-9 in plasma during HIV acquisition, in subjects with chronic HIV infection with differing virus control, and in uninfected individuals. During acute HIV infection, circulating Gal-9 was detected as early as 5 days after quantifiable HIV RNA and tracked plasma levels of interleukin (IL)-10, tumor necrosis factor (TNF)-α, and IL-1β. In chronic HIV infection, Gal-9 levels positively correlated with plasma HIV RNA levels (r=0.29; p=0.023), and remained significantly elevated during suppressive antiretroviral therapy (median: 225.3 pg/ml) and in elite controllers (263.3 pg/ml) compared to age-matched HIV-uninfected controls (54 pg/ml). Our findings identify Gal-9 as a novel component of the first wave of the cytokine storm in acute HIV infection that is sustained at elevated levels in virally suppressed subjects and suggest that Gal-9:Tim-3 crosstalk remains active in elite controllers and antiretroviral (ARV)-suppressed subjects, potentially contributing to ongoing inflammation and persistent T cell dysfunction.

The role of T cell immunoglobulin and mucin domain-3 in immune thrombocytopenia

T cell immunoglobulin and mucin domain-3 (TIM-3), originally identified as a T helper (Th) 1-specific type I membrane protein, plays a vital role in Th1 immunity and tolerance induction through interaction with its ligand, galectin-9. The binding of TIM-3 by galectin-9 serves to downregulate Th1 responses. Moreover, the regulatory function of TIM-3 has been extended to other cells, such as Th17 cells, CD4(+) CD25(+) regulatory T cells (Tregs), CD8(+) T cells and certain innate immune cells. Previous studies have acknowledged that the TIM-3 pathway is involved in the pathogenesis of several human autoimmune diseases, such as systemic lupus erythematous, rheumatoid arthritis and aplastic anaemia. Moreover, genetic data suggest a role for TIM-3 in human autoimmune diseases. However, in immune thrombocytopenia (ITP), a common Th1- and possibly Th17-biased autoimmune disorder, the role of TIM-3 has not been explored. Recently, our data have demonstrated that TIM-3 expression is reduced in ITP patients, and we have found a potential link between ITP and the TIM-3 pathway. In this article, we discuss and speculate on the role of the TIM-3 pathway in ITP.

Type I interferon protects antiviral CD8+ T cells from NK cell cytotoxicity

Despite development of new antiviral drugs, viral infections are still a major health problem. The most potent antiviral defense mechanism is the innate production of type I interferon (IFN-I), which not only limits virus replication but also promotes antiviral T cell immunity through mechanisms, which remain insufficiently studied. Using the murine lymphocytic choriomeningitis virus model system, we show here that IFN-I signaling on T cells prevented their rapid elimination in vivo. Microarray analyses uncovered that IFN-I triggered the expression of selected inhibitory NK-cell-receptor ligands. Consequently, T cell immunity of IFN-I receptor (IFNAR)-deficient T cells could be restored by NK cell depletion or in NK-cell-deficient hosts (Nfil3(-/-)). The elimination of Ifnar1(-/-) T cells was dependent on NK-cell-mediated perforin expression. In summary, we identified IFN-I as a key player regulating the protection of T cells against regulatory NK cell function.

Association of T-cell immunoglobulin and mucin domain-containing molecule 3 (Tim-3) polymorphisms with susceptibility and disease progression of HBV infection

PURPOSE

T-cell immunoglobulin and mucin domain-containing molecule 3 (Tim-3) plays an important role in regulating T cells in hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). However, few researches have reported the association of Tim-3 genetic variants with susceptibility and progression of HBV infection. In this study, we focused on the association of Tim-3 polymorphisms with HBV infection, HBsAg seroclearance and hepatocellular carcinoma.

METHODS

A total of 800 subjects were involved in this study. Four groups were studied here, including HBV, HBsAg seroclearance, HBV-associated HCC and healthy controls. Three single-nucleotide polymorphisms (SNPs) of Tim-3, rs246871, rs25855 and rs31223 were genotyped to analyze the association of Tim-3 polymorphisms with susceptibility and disease progression of HBV infection.

RESULTS

Our study found that rs31223 and rs246871 were associated with disease progression of HBV infection, while none of the three SNPs was relevant to HBV susceptibility. The minor allele "C" of rs31223 was found to be associated with an increased probability of HBsAg seroclearance (P = 0.033) and genotype "CC" of rs246871 to be associated with an increased probability of HBV-associated HCC (P = 0.007). In accordance, haplotypic analysis of the three polymorphisms also showed that the haplotype block CGC* and TGC* were significantly associated with HBsAg seroclearance (P<0.05) while haplotype block CAT*, CGT*, TAC* and TGT* were significantly associated with HBV-associated HCC (all P<0.05).

CONCLUSIONS

Genetic variants of Tim-3 have an important impact on disease progression of HBV infection. With specific Tim-3 polymorphisms, patients infected with HBV could be potential candidates of HCC and HBsAg seroclearance.

Patients with tuberculosis disease have Mycobacterium tuberculosis-specific CD8 T cells with a pro-apoptotic phenotype and impaired proliferative capacity, which is not restored following treatment

CD8 T cells play a critical role in control of chronic viral infections; however, the role of these cells in containing persistent bacterial infections, such as those caused by Mycobacterium tuberculosis (Mtb), is less clear. We assessed the phenotype and functional capacity of CD8 T cells specific for the immunodominant Mtb antigens CFP-10 and ESAT-6, in patients with pulmonary tuberculosis (TB) disease, before and after treatment, and in healthy persons with latent Mtb infection (LTBI). In patients with TB disease, CFP-10/ESAT-6-specific IFN-γ+ CD8 T cells had an activated, pro-apoptotic phenotype, with lower Bcl-2 and CD127 expression, and higher Ki67, CD57, and CD95 expression, than in LTBI. When CFP-10/ESAT-6-specific IFN-γ+ CD8 T cells were detectable, expression of distinct combinations of these markers was highly sensitive and specific for differentiating TB disease from LTBI. Successful treatment of disease resulted in changes of these markers, but not in restoration of CFP-10/ESAT-6-specific CD8 or CD4 memory T cell proliferative capacity. These data suggest that high mycobacterial load in active TB disease is associated with activated, short-lived CFP-10/ESAT-6-specific CD8 T cells with impaired functional capacity that is not restored following treatment. By contrast, LTBI is associated with preservation of long-lived CFP-10/ESAT-6-specific memory CD8 T cells that maintain high Bcl-2 expression and which may readily proliferate.

Overexpression of herpes simplex virus glycoprotein K (gK) alters expression of HSV receptors in ocularly-infected mice

PURPOSE

We have shown previously that HSV-1 glycoprotein K (gK) exacerbates corneal scarring (CS) in mice and rabbits. Here, we investigated the relative impact of gK overexpression on host responses during primary corneal infection and latency in trigeminal ganglia (TG) of infected mice.

METHODS

Mice were infected ocularly with HSV-gK(3) (expressing two extra copies of gK replacing latency associated transcript [LAT]), HSV-gK(3) revertant (HSV-gK(3)R), or wild-type HSV-1 strain McKrae. Individual corneas on day 5 post infection (PI) and TG on day 28 PI were isolated and used for detection of gB DNA in the TG, HSV-1 receptors in the cornea and TG, and inflammatory infiltrates in TG.

RESULTS

During primary HSV-1 infection, gK overexpression resulted in altered expression of herpesvirus entry mediator (HVEM), 3-O-sulfated heparin sulfate (3-OS-HS), paired immunoglobulin-like type 2 receptor-α (PILR-α), nectin-1, and nectin-2 in cornea of BALB/c, but not C57BL/6 mice. However, gK overexpression did have an effect on 3-OS-HS, PILR-α, nectin-1, and nectin-2 expression (but not HVEM expression) in TG of C57BL/6 mice during latency. These differences did not affect the level of latency, but instead were correlated with the presence of CS. The presence of LAT increased HVEM expression and this effect was enhanced further by the presence of CS in latently-infected mice. Finally, the presence of LAT, but not overexpression of gK, affected CD4, CD8, TNF-α, Tim-3, PD-1, IL-21, IL-2, and IFN-γ expression in TG.

CONCLUSIONS

We demonstrate a novel link between gK exacerbation of CS and HSV-1 receptors, suggesting a gK-induced molecular route for the pathogenesis as well as selective advantage of these entry routes for the pathogen during latency-reactivation cycle.

Immune derangement occurs in patients with H7N9 avian influenza

INTRODUCTION

Currently, little is known about the immunological characteristics of patients with avian influenza A (H7N9) virus infection.

METHODS

The numbers and percentages of peripheral blood immune cells were measured in 27 patients with laboratory-confirmed H7N9 virus infection and 30 healthy controls (HCs). The functional phenotypes of T cells and monocytes, as well as serum cytokine levels, were analyzed by flow cytometry.

RESULTS

There were 19 patients (70.4%) with acute respiratory distress syndrome, 13 (48.1%) with secondary respiratory infection, 20 (74%) with systemic inflammatory response syndrome (SIRS; defined as having at least two concurrent SIRS components), 18 (66.7%) with lymphocytopenia and 11 (40.7%) with reduced numbers of monocytes. In comparison with levels in the HCs, the levels of serum interleukin 6 (IL-6), IL-8 and IL-10 and the percentages of CD38+ or Tim-3+ T cells were significantly increased. However, the percentages of human leukocyte antigen-DR + and Tim-3+ monocytes were significantly decreased in patients compared with HCs.

CONCLUSIONS

Patients with avian H7N9 virus infection display profound SIRS concomitantly with an anti-inflammatory response, which may be associated with the rapid progression of and high mortality associated with this novel viral disease.

T-cell immunoglobulin- and mucin-domain-containing molecule 3 genetic variants and HIV+ non-Hodgkin lymphomas

T cell immunoglobulin- and mucin-domain-containing molecule 3 (TIM-3) has been established as a negative regulatory molecule and plays a critical role in inflammatory diseases such as rheumatoid arthritis, hepatitis B and C, and human immunodeficiency virus (HIV)-related inflammation. Recent studies have shown that chronic inflammation may greatly affect the pathogenesis of non-Hodgkin lymphomas (NHL). The aim of this study was to investigate whether polymorphisms in the TIM-3 gene were associated with susceptibility to non-NHL and HIV-related NHL. Three polymorphisms in TIM-3 gene (-1516G/T, -574G/T, and +4259T/G) were identified by polymerase chain reaction-restriction fragment length polymorphism in 434 NHL patients, 62 HIV-related NHL cases, and 512 healthy controls. Results showed that the prevalence of -574GT genotype and +4259TG genotype were significantly increased in the NHL cases than in controls (odds ratio (OR) = 2.72, 95% confidence interval (CI) = 1.50-4.92, p = 0.0006 and OR = 2.59, 95% CI = 1.49-4.49, p = 0.0005, respectively). The -1516G/T polymorphism did not reveal significant difference between patients and healthy controls. When analyzing the TIM-3 polymorphisms in HIV-related NHL patients, data showed that HIV+ NHL patients had higher prevalence of -574GT or +4259TG genotypes than those cases without HIV infection (OR = 3.48, 95% CI = 1.67-7.28, p = 0.0005 and OR = 2.92, 95% CI = 1.42-6.01, p = 0.0026, respectively). These results suggested polymorphisms in TIM-3 gene could be new risk factors for NHL as well as HIV-related NHL and suggested a possible role of the inflammatory factor in these diseases.

Fallen angels or risen apes? A tale of the intricate complexities of imbalanced immune responses in the pathogenesis and progression of immune-mediated and viral cancers

Excessive immune responses directed against foreign pathogens, self-antigens, or commensal microflora can cause cancer establishment and progression if the execution of tight immuno-regulatory mechanisms fails. On the other hand, induction of potent tumor antigen-specific immune responses together with stimulation of the innate immune system is a pre-requisite for effective anti-tumor immunity, and if suppressed by the strong immuno-regulatory mechanisms can lead to cancer progression. Therefore, it is crucial that the inevitable co-existence of these fundamental, yet conflicting roles of immune-regulatory cells is carefully streamlined as imbalances can be detrimental to the host. Infection with chronic persistent viruses is characterized by severe immune dysfunction resulting in T cell exhaustion and sometimes deletion of antigen-specific T cells. More often, this is due to increased immuno-regulatory processes, which are triggered to down-regulate immune responses and limit immunopathology. However, such heightened levels of immune disruption cause a concomitant loss of tumor immune-surveillance and create a permissive microenvironment for cancer establishment and progression, as demonstrated by increased incidences of cancer in immunosuppressed hosts. Paradoxically, while some cancers arise as a consequence of increased immuno-regulatory mechanisms that inhibit protective immune responses and impinge on tumor surveillance, other cancers arise due to impaired immuno-regulatory mechanisms and failure to limit pathogenic inflammatory responses. This intricate complexity, where immuno-regulatory cells can be beneficial in certain immune settings but detrimental in other settings underscores the need for carefully formulated interventions to equilibrate the balance between immuno-stimulatory and immuno-regulatory processes.

Tim-3 directly enhances CD8 T cell responses to acute Listeria monocytogenes infection

T cell Ig and mucin domain (Tim) 3 is a surface molecule expressed throughout the immune system that can mediate both stimulatory and inhibitory effects. Previous studies have provided evidence that Tim-3 functions to enforce CD8 T cell exhaustion, a dysfunctional state associated with chronic stimulation. In contrast, the role of Tim-3 in the regulation of CD8 T cell responses to acute and transient stimulation remains undefined. To address this knowledge gap, we examined how Tim-3 affects CD8 T cell responses to acute Listeria monocytogenes infection. Analysis of wild-type (WT) mice infected with L. monocytogenes revealed that Tim-3 was transiently expressed by activated CD8 T cells and was associated primarily with acquisition of an effector phenotype. Comparison of responses to L. monocytogenes by WT and Tim-3 knockout (KO) mice showed that the absence of Tim-3 significantly reduced the magnitudes of both primary and secondary CD8 T cell responses, which correlated with decreased IFN-γ production and degranulation by Tim-3 KO cells stimulated with peptide Ag ex vivo. To address the T cell-intrinsic role of Tim-3, we analyzed responses to L. monocytogenes infection by WT and Tim-3 KO TCR-transgenic CD8 T cells following adoptive transfer into a shared WT host. In this setting, the accumulation of CD8 T cells and the generation of cytokine-producing cells were significantly reduced by the lack of Tim-3, demonstrating that this molecule has a direct effect on CD8 T cell function. Combined, our results suggest that Tim-3 can mediate a stimulatory effect on CD8 T cell responses to an acute infection.

Expression of TIM-3 on CD4+ and CD8+ T cells in the peripheral blood and synovial fluid of rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by a chronic inflammatory process that targets the synovial lining of diarthrodial joints. TIM-3 plays a key role in the negative regulation of the immune response. In this study, we investigated the expression of TIM-3 on CD4+ and CD8+ T cells from systemic (peripheral blood) and local (synovial fluid) perspectives of RA. Level of TIM-3+ cells from peripheral blood and synovial fluid of patients as well as peripheral blood of healthy controls was measured by flow cytometry. Results showed that TIM-3 expression was significantly increased in both CD4+ and CD8+ T cells in the peripheral blood of RA (p < 0.001 and p < 0.001, respectively). Furthermore, patients revealed even higher expression of TIM-3 in CD4+ and CD8+ T cells in synovial fluid than in peripheral blood. When comparing TIM-3 level with the severity of RA, we identified that the percentage of TIM-3 on both peripheral CD4+ and peripheral CD8+ T cells was negatively correlated with disease activity score 28 (DAS28) of the patients. Similarly, TIM-3 on synovial fluid CD4+ and CD8+ T cells also revealed inverse correlation with DAS28 of the cases. Our data demonstrate a negative correlation between TIM-3 and the disease progression of RA.

IL-10-producing B cells are induced early in HIV-1 infection and suppress HIV-1-specific T cell responses

A rare subset of IL-10-producing B cells, named regulatory B cells (Bregs), suppresses adaptive immune responses and inflammation in mice. In this study, we examined the role of IL-10-producing B cells in HIV-1 infection. Compared to uninfected controls, IL-10-producing B cell frequencies were elevated in both blood and sigmoid colon during the early and chronic phase of untreated HIV-1 infection. Ex vivo IL-10-producing B cell frequency in early HIV-1 infection directly correlated with viral load. IL-10-producing B cells from HIV-1 infected individuals were enriched in CD19(+)TIM-1(+) B cells and were enriched for specificity to trimeric HIV-1 envelope protein. Anti-retroviral therapy was associated with reduced IL-10-producing B cell frequencies. Treatment of B cells from healthy donors with microbial metabolites and Toll-like receptor (TLR) agonists could induce an IL-10 producing phenotype, suggesting that the elevated bacterial translocation characteristic of HIV-1 infection may promote IL-10-producing B cell development. Similar to regulatory B cells found in mice, IL-10-producing B cells from HIV-1-infected individuals suppressed HIV-1-specific T cell responses in vitro, and this suppression is IL-10-dependent. Also, ex vivo IL-10-producing B cell frequency inversely correlated with contemporaneous ex vivo HIV-1-specific T cell responses. Our findings show that IL-10-producing B cells are induced early in HIV-1 infection, can be HIV-1 specific, and are able to inhibit effective anti-HIV-1 T cell responses. HIV-1 may dysregulate B cells toward Bregs as an immune evasion strategy.

Tim-3 signaling pathway as a novel negative mediator in lipopolysaccharide-induced endotoxic shock

Sepsis is a complex clinical condition caused by a dysregulated immune response to an infection. However, the mechanism by which our immune system controls this amplified inflammation is largely unknown. In this study, we investigated whether Tim-3 pathway could serve as a negative mediator in lipopolysaccharide (LPS)-induced endotoxic shock. Our results showed that Tim-3 was expressed on CD4(+) T cells, CD8(+) T cells, and NK cells, and was significantly increased in the peritoneal cavity of septic mice. Tim-3 acted as a marker of immune exhaustion and Tim-3-positive T cells and NK cells had a lower interferon (IFN)-γ production. Furthermore, blockade of Tim-3 pathway significantly accelerated mortality in septic mice, while activation of this pathway prolonged survival time. In vitro administration of Tim-3 blocking antibody restored the release of IFN-γ from splenocytes and decreased splenocyte apoptosis, and increased levels of IFN-γ and tumor necrosis factor (TNF)-α were also detected in septic mice at 24h post in vivo administration of the antibody. In contrast, activation of Tim-3 pathway prevented cell proliferation. Thus, Tim-3 signaling pathway acts as a novel negative mediator in LPS-induced endotoxic shock and could be a potential therapeutic target for the treatment of sepsis.

Levels of CD56+TIM-3- effector CD8 T cells distinguish HIV natural virus suppressors from patients receiving antiretroviral therapy

Prolonged antiretroviral therapy (ART) with effective HIV suppression and reconstitution of CD4 T cells, fails to restore CD8 T cell lytic effector function that is needed to eradicate the viral reservoir. Better understanding of the phenotype and function of circulating CD8 cells in HIV patients will contribute to new targeted therapies directed at increasing CD8 T cell lytic effector function and destruction of the viral reservoir. We show that CD8 T cells from ART treated patients had sharply reduced expression of CD56 (neural cell adhesion molecule-1), a marker associated with cytolytic function whereas elite patients who control HIV in the absence of ART had CD56+ CD8 T cell levels similar to uninfected controls. The CD56+ CD8 T cells had higher perforin upregulation as well as degranulation following stimulation with HIV gag peptides compared with CD56 negative CD8 T cells. Elite patients had the highest frequencies of perforin producing CD56+ CD8 T cells among all HIV+ groups. In patients receiving ART we noted high levels of the exhaustion marker TIM-3 on CD56+ CD8 T cells, implying that defective effector function was related to immune exhaustion. CD56+ CD8 T cells from elite or treated HIV patients responded to PMA plus ionomycin stimulation, and expressed transcription factors T-bet and EOMES at levels similar to uninfected controls. Consequently, the lytic effector defect in chronic HIV disease is due to immune exhaustion and quantitative loss of CD56+ CD8 T cells and this defect is not repaired in patients where viremia is suppressed and CD4 T cells are recovered after ART.

Reconstituting the cytotoxic CD56+ subset of CD8+ T cells through new interventions might improve the lytic effector capacity and contribute to reducing the viral reservoir. Our initial studies indicate that IL-15 treatment partly reverses the CD56 defect, implying that myeloid cell defects could be targeted for immune therapy during chronic HIV disease.

Multiparametric bioinformatics distinguish the CD4/CD8 ratio as a suitable laboratory predictor of combined T cell pathogenesis in HIV infection

HIV disease progression is characterized by numerous pathological changes of the cellular immune system. Still, the CD4 cell count and viral load represent the laboratory parameters that are most commonly used in the clinic to determine the disease progression. In this study, we conducted an interdisciplinary investigation to determine which laboratory parameters (viral load, CD4 count, CD8 count, CD4 %, CD8 %, CD4/CD8) are most strongly associated with pathological changes of the immune system. Multiparametric flow cytometry was used to assess markers of CD4(+) and CD8(+) T cell activation (CD38, HLA-DR), exhaustion (PD-1, Tim-3), senescence (CD28, CD57), and memory differentiation (CD45RO, CD27) in a cohort of 47 untreated HIV-infected individuals. Using bioinformatical methods, we identified 139 unique populations, representing the "combined T cell pathogenesis," which significantly differed between the HIV-infected individuals and healthy control subjects. CD38, HLA-DR, and PD-1 were particularly expressed within these unique T cell populations. The CD4/CD8 ratio was correlated with more pathological T cell populations (n = 10) and had a significantly higher average correlation coefficient than any other laboratory parameters. We also reduced the dimensionalities of the 139-unique populations by Z-transformations and principal component analysis, which still identified the CD4/CD8 ratio as the preeminent surrogate of combined T cell pathogenesis. Importantly, the CD4/CD8 ratio at baseline was shown to be significantly associated with CD4 recovery 2 y after therapy initiation. These results indicate that the CD4/CD8 ratio would be a suitable laboratory predictor in future clinical and therapeutic settings to monitor pathological T cell events in HIV infection.

Comparison of dynamic expressions of Tim-3 and PD-1 in the brains between toxoplasmic encephalitis-resistant BALB/c and -susceptible C57BL/6 mice

T cells and IFN-γ are essential for controlling the reactivation of toxoplasmic encephalitis (TE), regardless of whether mice are susceptible or resistant to TE. It has been demonstrated that CD8(+) T cells exhausted in chronic Toxoplasma gondii infection result in TE reactivation in C57BL/6 mice. However, this phenomenon had not been reported in genetically TE-resistant BALB/c mice. To explore the immune mechanism of TE in different backgrounds of mice, the dynamic expressions of Tim-3, programmed cell death 1 (PD-1), and their ligands (galectin-9, PD-L1, PD-L2) in brain tissues were compared between TE-resistant BALB/c and -susceptible C57BL/6 mice infected with Prugniaud (Pru, a type II strain) of T. gondii in this study. Compared with infected BALB/c mice, there were remarkable pathological changes with significantly higher histological scores in the brains of C57BL/6 mice at 14, 35, 50, and 70 days postinfection (p.i., P < 0.01); significantly increased mRNA expressions of Tim-3 at 35 (P < 0.05) and 70 (P < 0.01) days p.i.; and significantly increased PD-1 at all the times p.i. (P < 0.01) in the brains of infected C57BL/6 mice. Furthermore, there were significantly increased mRNA expressions of PD-L1 in the brain of C57BL/6 mice than that in BALB/c mice at all the times p.i. (P < 0.01). Although the mRNA expressions of galectin-9 (ligand of Tim-3) were increased in the brains of both lineages of mice at all the times p.i., it showed no differences between the two lineages of mice. Our data suggest that the differences of Tim-3 and PD-1/PD-L1 expressions may contribute to the different immune responses between TE-resistant BALB/c and -susceptible C57BL/6 mice infected with Pru strain of T. gondii.

Insights into B cells and HIV-specific B-cell responses in HIV-infected individuals

Human immunodeficiency virus (HIV) disease is associated with dysregulation and dysfunction involving all major lymphocyte populations, including B cells. Such perturbations occur early in the course of infection and are driven in large part by immune activation resulting from ongoing HIV replication leading to bystander effects on B cells. While most of the knowledge regarding immune cell abnormalities in HIV-infected individuals has been gained from studies conducted on the peripheral blood, it is clear that the virus is most active and most damaging in lymphoid tissues. Here, we discuss B-cell perturbations in HIV-infected individuals, focusing on the skewing of B-cell subsets that circulate in the peripheral blood and their counterparts that reside in lymphoid tissues. This review also highlights recent advances in evaluating HIV-specific B-cell responses both in the memory B-cell compartment, as well as in circulating antibody-secreting plasmablasts and the more differentiated plasma cells residing in tissues. Finally, we consider how knowledge gained by investigating B cells in HIV-infected individuals may help inform the development of an effective antibody-based HIV vaccine.

The phenotype and activation status of regulatory T cells during Friend retrovirus infection

The suppressive capacity of regulatory T cells (Tregs) has been extensively studied and is well established for many diseases. The expansion, accumulation, and activation of Tregs in viral infections are of major interest in order to find ways to alter Treg functions for therapeutic benefit. Tregs are able to dampen effector T cell responses to viral infections and thereby contribute to the establishment of a chronic infection. In the Friend retrovirus (FV) mouse model, Tregs are known to expand in all infected organs. To better understand the characteristics of these Treg populations, their phenotype was analyzed in detail. During acute FV-infection, Tregs became activated in the spleen and bone marrow, as indicated by various T cell activation markers, such as CD43 and CD103. Interestingly, Tregs in the bone marrow, which contains the highest viral loads during acute infection, displayed greater levels of activation than Tregs from the spleen. Treg expansion was driven by proliferation but no FV-specific Tregs could be detected. Activated Tregs in FV-infection did not produce Granzyme B (GzmB) or tumor necrosis factor α (TNFα), which are thought to be a potential mechanism for their suppressive activity. Furthermore, Tregs expressed inhibitory markers, such as TIM3, PD-1 and PD-L1. Blocking TIM3 and PD-L1 with antibodies during chronic FV-infection increased the numbers of activated Tregs. These data may have important implications for the understanding of Treg functions during chronic viral infections.

The impact of the TIM gene family on tumor immunity and immunosuppression

Tumor immunoevasion is an advanced phase of cancer immunosurveillance in which tumor cells acquire the ability to circumvent host immune systems and exploit protumorigenic inflammation. T-cell immunoglobulin mucin (TIM) gene family members have emerged as critical checkpoint proteins that regulate multiple immune response phases and maintain immune homeostasis. Accumulating evidence demonstrates that tumor cells exploit TIM gene family members to evade immunosurveillance, whereas TIM gene family members facilitate the prevention of inflammation-related tumor progression. Thus, a comprehensive analysis to clarify the relative contributions of TIM gene family members in tumor progression may elucidate immunosurveillance systems in cancer patients.

Networking at the level of host immunity: immune cell interactions during persistent viral infections

Persistent viral infections are the result of a series of connected events that culminate in diminished immunity and the inability to eliminate infection. By building our understanding of how distinct components of the immune system function both individually and collectively in productive versus abortive responses, new potential therapeutic targets can be developed to overcome immune dysfunction and thus fight persistent infections. Using lymphocytic choriomeningitis virus (LCMV) as a model of a persistent virus infection and drawing parallels to persistent human viral infections such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV), we describe the cellular relationships and interactions that determine the outcome of initial infection and highlight immune targets for therapeutic intervention to prevent or treat persistent infections. Ultimately, these findings will further our understanding of the immunologic basis of persistent viral infection and likely lead to strategies to treat human viral infections.

B cell responses to HIV antigen are a potent correlate of viremia in HIV-1 infection and improve with PD-1 blockade

Infection with Human Immunodeficiency Virus Type 1 (HIV-1) induces defects of both cellular and humoral immune responses. Impaired CD4+ T cell help and B cell dysfunction may partially explain the low frequency of broadly neutralizing antibodies in HIV-infected individuals. To understand the extent of B cell dysfunction during HIV infection, we assessed the level of B cell activation at baseline and after stimulation with a variety of antigens. Increased levels of viremia were associated with higher baseline expression of the activation marker CD86 on B cells and with decreased ability of B cells to increase expression of CD86 after in vitro stimulation with inactivated HIV-1. In a series of cell isolation experiments B cell responses to antigen were enhanced in the presence of autologous CD4+ T cells. HIV infected individuals had a higher frequency of PD-1 expression on B cells compared to HIV- subjects and PD-1 blockade improved B cell responsiveness to HIV antigen, suggesting that inhibitory molecule expression during HIV-1 infection may contribute to some of the observed B cell defects. Our findings demonstrate that during chronic HIV infection, B cells are activated and lose full capacity to respond to antigen, but suppression of inhibitory pressures as well as a robust CD4+ T cell response may help preserve B cell function.

T cell Ig and mucin domain-containing protein 3 is recruited to the immune synapse, disrupts stable synapse formation, and associates with receptor phosphatases

CD8(+) CTLs are adept at killing virally infected cells and cancer cells and releasing cytokines (e.g., IFN-γ) to aid this response. However, during cancer and chronic viral infections, such as with HIV, this CTL response is progressively impaired due to a process called T cell exhaustion. Previous work has shown that the glycoprotein T cell Ig and mucin domain-containing protein 3 (Tim-3) plays a functional role in establishing T cell exhaustion. Tim-3 is highly upregulated on virus and tumor Ag-specific CD8(+) T cells, and antagonizing Tim-3 helps restore function of CD8(+) T cells. However, very little is known of how Tim-3 signals in CTLs. In this study, we assessed the role of Tim-3 at the immunological synapse as well as its interaction with proximal TCR signaling molecules in primary human CD8(+) T cells. Tim-3 was found within CD8(+) T cell lipid rafts at the immunological synapse. Blocking Tim-3 resulted in a significantly greater number of stable synapses being formed between Tim-3(hi)CD8(+) T cells and target cells, suggesting that Tim-3 plays a functional role in synapse formation. Further, we confirmed that Tim-3 interacts with Lck, but not the phospho-active form of Lck. Finally, Tim-3 colocalizes with receptor phosphatases CD45 and CD148, an interaction that is enhanced in the presence of the Tim-3 ligand, galectin-9. Thus, Tim-3 interacts with multiple signaling molecules at the immunological synapse, and characterizing these interactions could aid in the development of therapeutics to restore Tim-3-mediated immune dysfunction.

Enhancement of SIV-specific cell mediated immune responses by co-administration of soluble PD-1 and Tim-3 as molecular adjuvants in mice

The development of an effective T cell based HIV vaccine would need to elicit cell mediated immune responses with superior magnitude, breadth, and quality. Since blocking the interactions between inhibitory receptors with their associated ligands using soluble PD-1 (sPD-1) and soluble Tim-3 (sTim-3) have been shown to reverse T cell exhaustion and enhance cell mediated immune responses, we tested if co-administration of sPD-1 and sTim-3 with an adenovirus vectored SIV vaccine (rAd5-SIV) can enhance cell mediated immune responses. The frequency of SIV antigen specific IFN-γ spot-forming cells and the secretion of IFN-γ and TNF-α by splenocytes from rAd5-SIV immunized mice was significantly increased when stimulated ex vivo with SIV peptides in the presence of sPD-1 or sTim-3 or both sPD-1 and sTim-3. The magnitude of cell mediated immune responses elicited by rAd5-SIV was enhanced by co-administration of sPD-1 and sTim-3. Co-administration of both sPD-1 and sTim-3 induced higher frequency of SIV antigen specific IFN-γ(+) spot-forming cells to poorly immunogenic Vif and Tat. The percentage of cell mediated responses for each SIV antigen became more balanced, with reduction to Gag but induction to non-structural proteins. Furthermore, co-injection of rAd5-sPD1 and rAd5-sTim3 with rAd5-SIV in mice enhanced T cell proliferation capability and generated more antigen specific IFN-γ(+) CD4(+) and CD8(+) T cells. Our study provided a new approach to enhance vaccine induced cell mediated immune responses, which may be applicable to improve the efficacy of vaccines against SIV/HIV.

Decreased galectin-9 and increased Tim-3 expression are related to poor prognosis in gastric cancer

Introduction

Galectin-9 (Gal-9) induces adhesion and aggregation of certain cell types and inhibits the metastasis of tumor cells. T-cell immunoglobulin–and mucin domain-3–containing molecule 3 (TIM-3) plays a pivotal role in immune regulation. The aim of this study is to investigate Gal-9 and TIM-3 alterations in gastric cancer and their prognostic values.

Methods

Gal-9 and Tim-3 expression was evaluated using a tissue microarray immunohistochemistry method in 305 gastric cancers, of which 84 had paired adjacent normal samples. Cell lines SGC-7901, BGC-823, MGC-803, MKN45 and GES-1 were also stained. Correlations were analyzed between expression levels of Gal-9 and Tim-3 protein and tumor parameters or clinical outcomes.

Results

Gal-9 and Tim-3 stained positive on tumor cells in 86.2% (263/305), and 60.0% (183/305) patients with gastric cancer, respectively. Gal-9 expression was significantly higher in cancer than in normal mucosa (P<0.001). Reduced Gal-9 expression was associated with lymph-vascular invasion, lymph node metastasis, distant metastasis and worse TNM staging (P = 0.034, P = 0.009, P = 0.002 and P = 0.043, respectively). In contrast, Tim-3 expression was significantly lower in cancer than in control mucosa (P<0.001). Patients with lymph-vascular invasion had higher expression levels of Tim-3 (P<0.001). Moreover, multivariate analysis shows that both high Gal-9 expression and low Tim-3 expression were significantly associated with long overall survival (P = 0.002, P = 0.010, respectively); the combination of Gal-9 and Tim-3 expression was an independent prognostic predictor for patients with gastric cancer (RR: 0.43; 95%CI: 0.20–0.93). H.pylori infection status was not associated with Gal-9 and Tim-3 expression (P = 0.102, P = 0.565).

Conclusion

The results suggest that expression of Gal-9 and Tim-3 in tumor cells may be a potential, independent prognostic factor for patients with gastric cancer. Gal-9 and TIM-3 may play an important part in the gastric carcinogenesis.

Combining regulatory T cell depletion and inhibitory receptor blockade improves reactivation of exhausted virus-specific CD8+ T cells and efficiently reduces chronic retroviral loads

Chronic infections with human viruses, such as HIV and HCV, or mouse viruses, such as LCMV or Friend Virus (FV), result in functional exhaustion of CD8⁺ T cells. Two main mechanisms have been described that mediate this exhaustion: expression of inhibitory receptors on CD8⁺ T cells and expansion of regulatory T cells (Tregs) that suppress CD8⁺ T cell activity. Several studies show that blockage of one of these pathways results in reactivation of CD8⁺ T cells and partial reduction in chronic viral loads. Using blocking antibodies against PD-1 ligand and Tim-3 and transgenic mice in which Tregs can be selectively ablated, we compared these two treatment strategies and combined them for the first time in a model of chronic retrovirus infection. Blocking inhibitory receptors was more efficient than transient depletion of Tregs in reactivating exhausted CD8⁺ T cells and reducing viral set points. However, a combination therapy was superior to any single treatment and further augmented CD8⁺ T cell responses and resulted in a sustained reduction in chronic viral loads. These results demonstrate that Tregs and inhibitory receptors are non-overlapping factors in the maintenance of chronic viral infections and that immunotherapies targeting both pathways may be a promising strategy to treat chronic infectious diseases.

A loss of function, the so-called ‘exhaustion’ of CD8⁺ T cells, is a hallmark of many chronic infections. The T cell exhaustion is mediated by two main mechanisms, the expression of inhibitory receptors on CD8⁺ T cells and virus-induced expansion of regulatory T cells (Tregs), which suppress CD8⁺ T cell activity. Several mouse studies revealed a reactivation of CD8⁺ T cells and reduction in chronic viral loads after blockage of one of these pathways. These results initiated a number of clinical studies mainly with cancer patients, in which blocking antibodies were used to interfere with inhibitory receptor signaling or drugs that deplete Tregs. For the first time we combined the two therapeutic approaches by using transgenic mice in which Tregs can be selectively ablated and injection of blocking antibodies in a chronic retroviral infection. The results indicate that the combination therapy was superior to any single treatment in further augmenting CD8⁺ T cell responses and reducing chronic viral loads. Our findings demonstrate that Tregs and inhibitory receptors are non-overlapping factors in the maintenance of chronic viral infections and that immunotherapies targeting both pathways may be a promising new strategy to treat chronic infectious diseases.

Characteristics of splenic CD8+ T cell exhaustion in patients with hepatitis C

There is increasing interest in the role of T cell exhaustion and it is well known that the natural history of chronic hepatitis C virus infection (HCV) is modulated by CD8(+) T cell immunobiology. There are many pathways that alter the presence of exhaustive T cells and, in particular, they are functionally impaired by inhibitory receptors, such as programmed death-1 (PD-1) and T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3). We obtained spleen, liver and peripheral blood (before and after splenectomy) lymphoid cells from 25 patients with HCV-related cirrhosis undergoing liver transplantation for end-stage disease or splenectomy for portal hypertension. In all samples we performed an extensive phenotypic study of exhaustion markers [PD-1, Tim-3, interferon (IFN)-γ) and their ligands (PD-L1, PD-L2, galectin-9] in CD8(+) T cell subpopulations (both total and HCV-specific) and in antigen-presenting cells (APC; monocytes and dendritic cells). In the spleen, total and HCV-specific CD8(+) T cells demonstrated enhanced markers of exhaustion, predominantly in the effector memory subpopulation. Similarly, splenic APC over-expressed inhibitory receptor ligands when compared to peripheral blood. Finally, when peripheral blood CD8(+) T cells were compared before and after splenectomy, markers of exhaustion were reduced in splenic CD8(+) T cells and APC. Our data in HCV-related cirrhosis suggest that CD8(+) T cells in the spleen manifest a significantly higher exhaustion compared to peripheral blood and may thus contribute to the failure to control HCV. Counteracting this process may contribute to inducing an effective immune response to HCV.

In vivo blockade of the programmed cell death-1 pathway using soluble recombinant PD-1-Fc enhances CD4+ and CD8+ T cell responses but has limited clinical benefit

The programmed cell death-1 (PD-1)/programmed cell death ligand-1 pathway has been shown to limit cell-mediated effector functions during chronic viral infections impeding clearance of pathogens. As a strategy to reverse this exhaustion and increase T cell polyfunctionality, PD-1 ligands were blocked in vivo using a recombinant macaque PD-1 fused to a macaque Ig-Fc (rPD-1-Fc) in SIVmac239-infected rhesus macaques during the early chronic phase of infection, either alone or in combination with antiretroviral therapy. In vitro blockade showed improvement of Ag-specific CD4(+) and CD8(+) T cells from monkeys chronically infected with SIV. Of note, a prolonged 5-d blockade in culture was beneficial for both gag-specific CD4(+) and CD8(+) T cells based on proliferation and dual cytokine production. Although the in vivo administration of rPD-1-Fc induced enhanced SIV-specific CD4 and CD8 T cell proliferation both in the blood and gut, it failed to alter plasma viremia. However, rPD-1-Fc administration in the context of antiretroviral therapy interruption induced a significant delay of viral load rebound. In addition, rPD-1-Fc administration in MamuA*001(+) monkeys led to both an increase in the frequencies and Ki67 expression of GagCM9(+) CD8(+) T cells in the blood and rectal mucosa and polyfunctionality of GagCM9(+) CD8(+) T cells in blood. In conclusion, however, our data suggest that PD-1/programmed cell death ligand-1 blockade using soluble rPD-1-Fc instead of anti-PD-1 mAb, although effective in rescuing the effector function of SIV-specific CD4(+) and CD8(+) T cells during the early chronic phase of infection, has limited clinical benefit.

Towards an HIV cure: science and debate from the International AIDS Society 2013 symposium

The International AIDS Society convened the multi-stakeholder “Towards an HIV Cure” symposium in Kuala Lumpur, Malaysia in 2013 to address the significant research challenges posed by the search for a cure for HIV infection. Current antiretroviral regimens select for a small reservoir of cells that harbour latent HIV provirus, produce few or no HIV virions, and resist detection or clearance by host immunity. The symposium examined basic molecular science and animal model data, and emerging and ongoing clinical trial results to prioritise strategies and determine the viral and immune responses that could lead to HIV remission without ART. Here we review the presentations that scrutinized the molecular mechanisms controlling virus expression from proviral DNA, and the intrinsic cellular restriction and immune mechanisms preventing viral production. Insights from the basic science have translated into new therapeutic strategies seeking HIV remission without ongoing therapy, and much interest was focused on these ongoing trials. We also summarise the emerging ethical issues and patient expectations as concepts move into the clinic.

The enduring tale of T cells in HIV immunopathogenesis

HIV continues to be a major health problem worldwide even today. Owing to the intricate nature of its interactions with the immune system, HIV has remained an enigma that cleverly utilizes the host machinery to survive. Its ability to evade the host immune system, at both levels, innate and adaptive, allows the pathogen to replicate and transmit from one host to another. It has been shown that HIV has multipronged effects especially on the adaptive immunity, with CD4+ T cells being the worst affected T cell populations. Various analyses have revealed that the exposure to HIV results in clonal expansion and excessive activation of the immune system. Also, an abnormal process of differentiation has been observed suggestive of an alteration and blocks in the maturation of various T cell subsets. Additionally, HIV has shown to accelerate immunosenescence and exhaustion of the overtly activated T cells. Apart from causing phenotypic changes, HIV has adverse effects on the functional aspect of the immune system, with evidences implicating it in the loss of the capacity of T cells to secrete various antiviral cytokines and chemokines. However, there continues to be many aspects of the immunopathogenesis of HIV that are still unknown and thus require further research to convert the malaise of HIV into a manageable epidemic.

Costimulation-adhesion blockade is superior to cyclosporine A and prednisone immunosuppressive therapy for preventing rejection of differentiated human embryonic stem cells following transplantation

RATIONALE

Human embryonic stem cell (hESC) derivatives are attractive candidates for therapeutic use. The engraftment and survival of hESC derivatives as xenografts or allografts require effective immunosuppression to prevent immune cell infiltration and graft destruction.

OBJECTIVE

To test the hypothesis that a short-course, dual-agent regimen of two costimulation-adhesion blockade agents can induce better engraftment of hESC derivatives compared to current immunosuppressive agents.

METHODS AND RESULTS

We transduced hESCs with a double fusion reporter gene construct expressing firefly luciferase (Fluc) and enhanced green fluorescent protein, and differentiated these cells to endothelial cells (hESC-ECs). Reporter gene expression enabled longitudinal assessment of cell engraftment by bioluminescence imaging. Costimulation-adhesion therapy resulted in superior hESC-EC and mouse EC engraftment compared to cyclosporine therapy in a hind limb model. Costimulation-adhesion therapy also promoted robust hESC-EC and hESC-derived cardiomyocyte survival in an ischemic myocardial injury model. Improved hESC-EC engraftment had a cardioprotective effect after myocardial injury, as assessed by magnetic resonance imaging. Mechanistically, costimulation-adhesion therapy is associated with systemic and intragraft upregulation of T-cell immunoglobulin and mucin domain 3 (TIM3) and a reduced proinflammatory cytokine profile.

CONCLUSIONS

Costimulation-adhesion therapy is a superior alternative to current clinical immunosuppressive strategies for preventing the post-transplant rejection of hESC derivatives. By extending the window for cellular engraftment, costimulation-adhesion therapy enhances functional preservation following ischemic injury. This regimen may function through a TIM3-dependent mechanism.

Activation associated ERK1/2 signaling impairments in CD8+ T cells co-localize with blunted polyclonal and HIV-1 specific effector functions in early untreated HIV-1 infection

We recently observed that a large proportion of activated (CD38(+)HLA-DR(+)) CD8(+) T cells from recently HIV-1-infected adults are refractory to phosphorylation of ERK1/2 kinases (p-ERK1/2-refractory). Given that the ERK1/2 pathway mediates intracellular signaling critical for multiple T cell functions, including key effector functions, the loss of ERK1/2 responsiveness may have broad consequences for CD8(+) T cell function. In the current study, we hypothesized that the p-ERK1/2-refractory population, localized largely within the activated CD38(+)HLA-DR(+) CD8(+) T cell population, would display impairments in CD8(+) T cell effector functions, such as cytokine production and degranulation, compared to CD8(+) p-ERK1/2-responsive cells. We further hypothesized that the p-ERK1/2-refractory phenotype is persistent over time during untreated infection, and would correlate with poorer virologic control, in a manner independent of CD8(+) T cell activation level. We performed single-cell resolution, flow cytometric assays of phospho-kinase responses paired to intracellular cytokine staining in one assay to examine IFN-γ, perforin and CD107α responses in CD8(+) T cells by ERK1/2 signaling profile. On a per cell basis, p-ERK1/2-refractory cells, which fall predominantly within the activated CD8(+) T cell compartment, produced less IFN-γ in response to polyclonal or HIV-1 antigen-specific stimulation, and expressed lower levels of perforin and CD107α. The p-ERK1/2 refractory cell population displayed minimal overlap with the PD-1 and Tim-3 inhibitory exhaustion markers and predicted high viral load independent of activation, suggesting that ERK1/2 may be a unique marker and point of intervention for improving CD8(+) T cell function. Blunted effector functions, secondary to ERK1/2 signaling deficits concentrated within activated CD8(+) T cells, may contribute to immunodeficiency and underlie the predictive capacity of CD8(+) T cell activation on HIV-1 disease progression. (270/300).

A disintegrin and metalloprotease (ADAM) 10 and ADAM17 are major sheddases of T cell immunoglobulin and mucin domain 3 (Tim-3)

T cell immunoglobulin and mucin domain 3 (Tim-3) dampens the response of CD4(+) and CD8(+) effector T cells via induction of cell death and/or T cell exhaustion and enhances the ability of macrophages to clear pathogens via binding to galectin 9. Here we provide evidence that human Tim-3 is a target of A disintegrin and metalloprotease (ADAM)-mediated ectodomain shedding resulting in a soluble form of Tim-3. We identified ADAM10 and ADAM17 as major sheddases of Tim-3 as shown by ADAM-specific inhibitors and the ADAM10 pro-domain in HEK293 cells and ADAM10/ADAM17-deficient murine embryonic fibroblasts. PMA-induced shedding of Tim-3 was abrogated by deletion of amino acids Glu(181)-Asp(190) of the stalk region and Tim-3 lacking the intracellular domain was not efficiently cleaved after PMA stimulation. Surprisingly, a single lysine residue within the intracellular domain rescues shedding of Tim-3. Shedding of endogenous Tim-3 was found in primary human CD14(+) monocytes after PMA and ionomycin stimulation. Importantly, the recently described down-regulation of Tim-3 from Toll-like receptor-activated CD14(+) monocytes was caused by ADAM10- and ADAM17-mediated shedding. Inhibition of Tim-3 shedding from lipopolysaccharide-induced monocytes did not influence lipopolysaccharide-induced TNFα and IL-6 but increases IL-12 expression. In summary, we describe Tim-3 as novel target for ADAM-mediated ectodomain shedding and suggest a role of Tim-3 shedding in TLR-mediated immune responses of CD14(+) monocytes.

Tim-3 is differently expressed in genetically susceptible C57BL/6 and resistant BALB/c mice during oral infection with Toxoplasma gondii

Tim-3 has opposing roles in innate and adaptive immunities. It not only dampens CD4+ and CD8+ T cells responses but also enhances the ability of macrophages to eliminate intracellular pathogens. After peroral infection with 100 cysts of Toxoplasma gondii genetically susceptible C57BL/6 mice develop an unchecked Th1 response associated with the development of small intestinal immunopathology. Here we report that upon infection with T. gondii, both susceptible C57BL/6 and resistant BALB/c mice exhibit increased frequencies of Tim-3+ cells in spleens and mesenteric lymph nodes. The number of Tim-3+ cells was significantly higher in C57BL/6 than in BALB/c mice. Tim-3 was expressed by macrophages, dendritic, natural killer, as well as CD4+ and CD8+ T cells. Highest frequencies of Tim-3+ cells were observed at the peak of Th1 responses (day 7 post infection) concurrent with the development of ileal immunopathology. Infected Tim-3-deficient BALB/c mice did not develop ileal immunopathology nor did their parasite loads differ from those in wildtype BALB/c mice. Thus, although Tim-3 is markedly upregulated upon infection and differentially regulated in susceptible and resistant mice upon infection with T. gondii, the absence of Tim-3 is not sufficient to overcome the genetic resistance of BALB/c mice to the development of Th1-driven small intestinal immunopathology.

TIM-3 as a novel therapeutic target for eradicating acute myelogenous leukemia stem cells

Acute myelogenous leukemia (AML) originates from self-renewing leukemic stem cells (LSCs), which represent the ultimate therapeutic target for AML. Recent studies have identified several AML LSC-specific surface antigens as candidate targets of therapeutic molecules. T cell immunoglobulin mucin-3 (TIM-3) is expressed on LSCs in most types of AML, with the exception of acute promyelocytic leukemia, but not on normal hematopoietic stem cells (HSCs). In xenograft models reconstituted with human AML LSCs or HSCs, an anti-human TIM-3 mouse IgG2a antibody with cytotoxic activities eradicates AML LSCs in vivo, but does not affect normal human hematopoiesis. Thus, TIM-3 is a promising therapeutic target for the eradication of AML LSCs.

Immune evasion in acute myeloid leukemia: current concepts and future directions

Immune responses generated against malignant cells have the potential to inhibit tumor growth, or even eliminate transformed cells before a tumor forms. However, immune tolerance mechanisms that normally protect healthy tissues from autoimmune damage pose a formidable barrier to the development of effective anti-tumor immunity. Because malignant cells are derived from self-tissues, the majority of defined tumor antigens are either shared or aberrantly expressed self-proteins. Eliciting productive T cell responses against such proteins is challenging, as most high-affinity, self-reactive T cells are purged during thymic selection. Some T cells capable of tumor antigen recognition escape thymic deletion, but are functionally inhibited by peripheral tolerance mechanisms which limit their ability to attack a developing malignancy. Alternatively, some tumors express antigens derived from mutated self-proteins, viral proteins or self proteins expressed only during embryonic development. These antigens are recognized by the immune system as foreign and could be recognized by a relatively large number of peripheral T cells. Even in this scenario, tumors evade otherwise effective T cell responses by employing potent immunosuppressive mechanisms within their local environment. In the setting for solid malignancies, such as melanoma, a growing number of putative immune evasion mechanisms have been characterized. However, acute myeloid leukemia (AML) is a systemic disease, and the pathways it exploits to subvert the host immune response may be quite different than those of a solid tumor. Much remains unknown regarding the immune escape mechanisms promoted by AML, and whether efforts to thwart tolerance may influence the progression of this disease. Here, we review current concepts of immune evasion in AML, and speculate how potentially effective immunotherapeutic strategies might be developed to reverse immune tolerance in leukemia patients in the future.

Cis association of galectin-9 with Tim-3 differentially regulates IL-12/IL-23 expressions in monocytes via TLR signaling

Human monocytes/macrophages (M/M_Ф) of the innate immunity sense and respond to microbial products via specific receptor coupling with stimulatory (such as TLR) and inhibitory (such as Tim-3) receptors. Current models imply that Tim-3 expression on M/M_Ø can deliver negative signaling to TLR-mediated IL-12 expression through trans association with its ligand Galectin-9 (Gal-9) presented by other cells. However, Gal-9 is also expressed within M/M_Ø, and the effect of intracellular Gal-9 on Tim-3 activities and inflammatory responses in the same M/M_Ø remains unknown. In this study, our data suggest that Tim-3 and IL-12/IL-23 gene transcriptions are regulated by enhanced or silenced Gal-9 expression within monocytes through synergizing with TLR signaling. Additionally, TLR activation facilitates Gal-9/Tim-3 cis association within the same M/M_Ø to differentially regulate IL-12/IL-23 expressions through STAT-3 phosphorylation. These results reveal a ligand (Gal-9) compartment-dependent regulatory effect on receptor (Tim-3) activities and inflammatory responses via TLR pathways—a novel mechanism underlying cellular responses to external or internal cues.

Role of Tim-3 in pathogenesis of inflammatory diseases of the digestive system

T cell immunoglobulin mucin domain-containing molecules (Tim)-3 is a type I cell membrane glycoprotein that is expressed on the surface of cells involved in innate and adaptive immunity. As the first discovered member of Tim family, Tim-3 participates in T cell-induced immune responses. By interacting with its ligands galectin-9 or PtdSer, Tim-3 induces cell apoptosis and clearance of apoptotic cells in autoimmune disorders, allergic diseases and virus infection-associated diseases. Tim-3 can act as a negative regulator of Th1/Th17 immune responses. Current research has shown that Tim-3 is involved in the pathogenesis of inflammatory diseases of the digestive system. Here we will review the progress in understanding the role of Tim-3 in the pathogenesis of inflammatory diseases of the digestive system.

Merkel polyomavirus-specific T cells fluctuate with merkel cell carcinoma burden and express therapeutically targetable PD-1 and Tim-3 exhaustion markers

PURPOSE

The persistent expression of Merkel cell polyomavirus (MCPyV) oncoproteins in Merkel cell carcinoma (MCC) provides a unique opportunity to characterize immune evasion mechanisms in human cancer. We isolated MCPyV-specific T cells and determined their frequency and functional status.

EXPERIMENTAL DESIGN

Multiparameter flow cytometry panels and HLA/peptide tetramers were used to identify and characterize T cells from tumors (n = 7) and blood (n = 18) of patients with MCC and control subjects (n = 10). PD-1 ligand (PD-L1) and CD8 expression within tumors were determined using mRNA profiling (n = 35) and immunohistochemistry (n = 13).

RESULTS

MCPyV-specific CD8 T cells were detected directly ex vivo from the blood samples of 7 out of 11 (64%) patients with MCPyV-positive tumors. In contrast, 0 of 10 control subjects had detectable levels of these cells in their blood (P < 0.01). MCPyV-specific T cells in serial blood specimens increased with MCC disease progression and decreased with effective therapy. MCPyV-specific CD8 T cells and MCC-infiltrating lymphocytes expressed higher levels of therapeutically targetable PD-1 and Tim-3 inhibitory receptors compared with T cells specific to other human viruses (P < 0.01). PD-L1 was present in 9 of 13 (69%) MCCs and its expression was correlated with CD8-lymphocyte infiltration.

CONCLUSIONS

MCC-targeting T cells expand with tumor burden and express high levels of immune checkpoint receptors PD-1 and Tim-3. Reversal of these inhibitory pathways is therefore a promising therapeutic approach for this virus-driven cancer.

Involvement of Galectin-9/TIM-3 pathway in the systemic inflammatory response in early-onset preeclampsia

BACKGROUND

Preeclampsia is a common obstetrical disease affecting 3-5% of pregnancies and representing one of the leading causes of both maternal and fetal mortality. Maternal symptoms occur as an excessive systemic inflammatory reaction in response to the placental factors released by the oxidatively stressed and functional impaired placenta. The T-cell immunoglobulin domain and mucin domain (TIM) family is a relatively newly described group of molecules with a conserved structure and important immunological functions. Identification of Galectin-9 as a ligand for TIM-3 has established the Galectin-9/TIM-3 pathway as an important regulator of Th1 immunity and tolerance induction.

METHODS

The aim of our study was to investigate the expression and function of Galectin-9 and TIM-3 molecules by peripheral blood mononuclear cells and the possible role of Galectin-9/TIM-3 pathway in the immunoregulation of healthy pregnancy and early-onset preeclampsia. We determined TIM-3 and Gal-9 expression and cytotoxicicty of peripheral lymphocytes of early-onset preeclamptic women and healthy pregnant woman using flow cytometry.

RESULTS

Investigating peripheral lymphocytes of women with early-onset preeclampsia, our results showed a decreased TIM-3 expression by T cells, cytotoxic T cells, NK cells and CD56(dim) NK cells compared to healthy pregnant women. Interestingly, we found a notably increased frequency of Galectin-9 positive cells in each investigated lymphocyte population in the case of early-onset preeclamptic patients. We further demonstrated increased cytotoxic activity by cytotoxic T and CD56(dim) NK cells in women with early-onset preeclampsia. Our findings showed that the strongest cellular cytotoxic response of lymphocytes occurred in the TIM-3 positive subpopulations of different lymphocytes subsets in early-onset preeclampsia.

CONCLUSION

These data suggest that Gal-9/TIM-3 pathway could play an important role in the immune regulation during pregnancy and the altered Galectin-9 and TIM-3 expression could result an enhanced systemic inflammatory response including the activation of Th1 lymphocytes in preeclampsia.

Dysregulated Tim-3 expression on natural killer cells is associated with increased Galectin-9 levels in HIV-1 infection

Background

Natural killer (NK) cells constitutively express high levels of Tim-3, an immunoregulatory molecule recently proposed to be a marker for mature and functional NK cells. Whether HIV-1 infection modulates the expression of Tim-3 on NK cells, or the levels of its ligand Galectin-9 (Gal-9), and how signaling through these molecules affects the NK cell response to HIV-1 remains inadequately understood.

Results

We analyzed Tim-3 and Gal-9 expression in a cohort of 85 individuals with early and chronic HIV-1 infection, and in 13 HIV-1 seronegative control subjects. HIV-1 infection was associated with reduced expression of Tim-3 on NK cells, which was normalized by HAART. Plasma concentrations of Gal-9 were higher in HIV-1-infected individuals than in healthy individuals. Interestingly, Gal-9 expression in immune cells was significantly elevated in early infection, with monocytes and dendritic cells displaying the highest expression levels, which correlated with HIV-1 viral loads. In vitro, Gal-9 triggered Tim-3 downregulation on NK cells as well as NK cell activation.

Conclusions

Our data suggest that high expression levels of Gal-9 during early HIV-1 infection can lead to enhanced NK cell activity, possibly allowing for improved early control of HIV-1. In contrast, persistent Gal-9 production might impair Tim-3 activity and contribute to NK cell dysfunction in chronic HIV-1 infection.

Using EAE to better understand principles of immune function and autoimmune pathology

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) in which myelin becomes the target of attack by autoreactive T cells. The immune components of the disease are recapitulated in mice using the experimental autoimmune encephalomyelitis (EAE) model. EAE is classically induced by the immunization of mice with encephalitogenic antigens derived from CNS proteins such as proteolipid protein (PLP), myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG). Immunization of susceptible mouse strains with these antigens will induce autoreactive inflammatory T cell infiltration of the CNS. More recently, the advent of clonal T cell receptor transgenic mice has led to the development of adoptive transfer protocols in which myelin-specific T cells may induce disease upon transfer into naïve recipient animals. When used in concert with gene knockout strains, these protocols are powerful tools by which to dissect the molecular pathways that promote inflammatory T cells responses in the central nervous system (CNS). Further, myelin-antigen-specific transgenic T cells may be cultured in vitro under a variety of conditions prior to adoptive transfer, allowing one to study the effects of soluble factors or pharmacologic compounds on T cell pathogenicity. In this review, we describe many of the existing models of EAE, and discuss the contributions that use of these models has made in understanding both T helper cell differentiation and the function of inhibitory T cell receptors. We focus on the  step-by-step elucidation of the network of signals required for T helper 17 (Th17) cell differentiation, as well as the molecular dissection of the Tim-3 negative regulatory signaling pathway in Th1 cells.

HIV infection deregulates Tim-3 expression on innate cells: combination antiretroviral therapy results in partial restoration

BACKGROUND

The Tim-3 receptor has been implicated as a negative regulator of adaptive immune responses and has been linked to T-cell dysfunction in chronic viral infections, such as HIV. Blocking Tim-3 has been proposed as a potential therapeutic intervention in HIV infection. However, a more detailed characterization of Tim-3 expression in the presence of HIV is required before such strategies can be considered.

METHODS

In this study, we investigate Tim-3 expression on innate immune cell subsets in chronic HIV-infected individuals pretherapy and posttherapy.

RESULTS

We report that, pretherapy, HIV infection is associated with elevated levels of Tim-3 on resting innate lymphocytes (NK, NKT, and γδ T cells), but not resting monocytes. In the absence of HIV infection, stimulation with an inflammatory stimulus resulted in decreased Tim-3 on monocytes and increased Tim-3 on NK, NKT, and γδ T cells. However, innate cells from HIV-infected donors were significantly less responsive to stimulation. Six months of combination antiretroviral therapy (cART) restored Tim-3 levels on resting NK cells but not NKT or γδ T cells. The responses of all subsets to inflammatory stimuli were restored to some extent with cART but only reached HIV-negative control levels in monocytes and NK cells.

DISCUSSION

These results demonstrate that, during HIV infection, Tim-3 expression on innate cells is dysregulated and that this dysregulation is only partially restored after 6 months of cART. Our findings suggest that Tim-3 is differentially regulated on innate immune effector cells, and have direct implications for strategies designed to block Tim-3-ligand interactions.

Taming dendritic cells with TIM-3: another immunosuppressive strategy used by tumors

Evaluation of: Chiba S, Baghdadi M, Akiba H et al. Tumor-infiltrating DCs suppress nucleic acid-mediated innate immune responses through interactions between the receptor TIM-3 and the alarmin HMGB1. Nat. Immunol. 13, 832-842 (2012). The identification of TIM-3 expression on tumor-associated dendritic cells (TADCs) provides insight into another aspect of tumor-mediated immunosuppression. The role of TIM-3 has been well characterized on tumor-infiltrating T cells; however, its role on TADCs was not previously known. The current paper demonstrated that TIM-3 was predominantly expressed by TADCs and its interaction with the nuclear protein HMGB1 suppressed nucleic acid-mediated activation of an effective antitumor immune response. The authors were able to show that TIM-3 interaction with HMGB1 prevented the localization of nucleic acids into endosomal vesicles. Furthermore, chemotherapy was found to be more effective in anti-TIM-3 monoclonal antibody-treated mice or mice depleted of all DCs, which indicated that a significant role is played by TADCs in inhibiting tumor regression. Taken together, these findings identify TIM-3 as a potential target for inducing antitumor immunity in conjunction with DNA vaccines and/or immunogenic chemotherapy in clinical settings.

Immune exhaustion and immune senescence: two distinct pathways for HBV vaccine failure during HCV and/or HIV infection

Given the shared risk factors for transmission, co-infection of hepatitis B virus (HBV) with hepatitis C virus (HCV) and/or human immunodeficiency virus (HIV) is quite common, and may lead to increases in morbidity and mortality. As such, HBV vaccine is recommended as the primary means to prevent HBV super-infection in HCV- and/or HIV-infected individuals. However, vaccine response (sero-conversion with a hepatitis B surface antibody titer >10 IU/L) in this setting is often blunted, with poor response rates to standard HBV vaccinations in virally infected individuals when compared with the healthy subjects. This phenomenon also occurs to other vaccines in adults, such as pneumococcal and influenza vaccines, in other immunocompromised hosts who are really at risk for opportunistic infections, such as individuals with hemodialysis, transplant, and malignancy. In this review, we summarize the underlying mechanisms involving vaccine failure in these conditions, focusing on immune exhaustion and immune senescence--two distinct signaling pathways regulating cell function and fate. We raise the possibility that blocking these negative signaling pathways might improve success rates of immunizations in the setting of chronic viral infection.

Expression of T-cell Immunoglobulin- and Mucin-domain-containing Molecule-3 on Lymphocytes from Henoch-Schoenlein Purpura Patients

OBJECTIVE

To investigate T-cell immunoglobulin domain and mucin domain-containing molecule-3 (Tim-3) and its ligand galectin-9 mRNA expression in peripheral blood mononuclear cells (PBMCs) from Henoch-Schoenlein Purpura (HSP) patients.

METHODS

Quantitative real-time reverse transcription-polymerase chain reaction (PCR) was used to examine the mRNA expression of Tim-3 and its ligand galectin-9 in PBMCs from HSP patients. ELISA methods were used to examine the levels of serum IFN-γ and immunoglobulin A1 (IgA1). The Spearman rank test was used for correlation analysis between Tim-3, galectin-9 mRNA expression and serum IFN-γ and IgA1 levels, respectively.

FINDINGS

The results showed that Tim-3 and galectin-9 mRNA expression was obviously higher in patients, which was closely correlated with serum IFN-γ and IgA1, respectively.

CONCLUSION

The results suggested that Tim-3/Tim-3L may be related to the pathogenesis of HSP.

IL-21 restricts virus-driven Treg cell expansion in chronic LCMV infection

Foxp3⁺ regulatory T (Treg) cells are essential for the maintenance of immune homeostasis and tolerance. During viral infections, Treg cells can limit the immunopathology resulting from excessive inflammation, yet potentially inhibit effective antiviral T cell responses and promote virus persistence. We report here that the fast-replicating LCMV strain Docile triggers a massive expansion of the Treg population that directly correlates with the size of the virus inoculum and its tendency to establish a chronic, persistent infection. This Treg cell proliferation was greatly enhanced in IL-21R^−/− mice and depletion of Treg cells partially rescued defective CD8⁺ T cell cytokine responses and improved viral clearance in some but not all organs. Notably, IL-21 inhibited Treg cell expansion in a cell intrinsic manner. Moreover, experimental augmentation of Treg cells driven by injection of IL-2/anti-IL-2 immune complexes drastically impaired the functionality of the antiviral T cell response and impeded virus clearance. As a consequence, mice became highly susceptible to chronic infection following exposure to low virus doses. These findings reveal virus-driven Treg cell proliferation as potential evasion strategy that facilitates T cell exhaustion and virus persistence. Furthermore, they suggest that besides its primary function as a direct survival signal for antiviral CD8⁺ T cells during chronic infections, IL-21 may also indirectly promote CD8⁺ T cell poly-functionality by restricting the suppressive activity of infection-induced Treg cells.

T cell exhaustion represents a state of T cell dysfunction associated with clinically relevant diseases, such as persistent viral infections or cancer. Although the molecular signature of exhausted T cells has been characterized in detail at the functional and transcriptional level, the immunological mechanisms that lead to T cell exhaustion during chronic infections remain poorly understood. Our present study reports two major findings that illustrate a pathway that contributes to T cell exhaustion during viral infection, and indicate its modulation by both, the pathogen and the host. First, we show that a persistence-inducing virus triggers the massive proliferation of Foxp3⁺ regulatory T (Treg) cells and demonstrate the potential of Treg cells to promote T cell exhaustion and chronic infection. Second, we identify IL-21 as a crucial host factor that antagonizes this virus-driven expansion of the Treg population in a cell intrinsic manner independent of IL-2. Thus, in addition to its known pre-dominant direct positive effects on antiviral T cells, IL-21 can also alleviate the suppressive activity of Treg cells. Together, these results suggest enhanced Treg cell responses as a mechanism of immune evasion that could be therapeutically targeted with IL-21.

Involvement of CD244 in regulating CD4+ T cell immunity in patients with active tuberculosis

CD244 (2B4) is a member of the signaling lymphocyte activation molecule (SLAM) family of immune cell receptors and it plays an important role in modulating NK cell and CD8⁺ T cell immunity. In this study, we investigated the expression and function of CD244/2B4 on CD4⁺ T cells from active TB patients and latent infection individuals. Active TB patients had significantly elevated CD244/2B4 expression on M. tuberculosis antigen-specific CD4⁺ T cells compared with latent infection individuals. The frequencies of CD244/2B4-expressing antigen-specific CD4⁺ T cells were significantly higher in retreatment active TB patients than in new active TB patients. Compared with CD244/2B4-dull and -middle CD4⁺ T cells, CD244/2B4-bright CD4⁺ T cell subset had significantly reduced expression of IFN-γ, suggesting that CD244/2B4 expression may modulate IFN-γ production in M. tuberculosis antigen-responsive CD4⁺ T cells. Activation of CD244/2B4 signaling by cross-linking led to significantly decreased production of IFN-γ. Blockage of CD244/2B4 signaling pathway of T cells from patients with active TB resulted in significantly increased production of IFN-γ, compared with isotype antibody control. In conclusion, CD244/2B4 signaling pathway has an inhibitory role on M. tuberculosis antigen-specific CD4⁺ T cell function.