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

Dynamic changes in TIGIT expression on the T-cell surface and TIGIT-mediated T-cell dysfunction in the brains of mice with chronic Toxoplasma gondii infection

The immunosuppressive receptor TIGIT plays a vital role in the regulation of the immune system's response to pathogens. However, the expression pattern of this receptor in mouse brains during infection with Toxoplasma gondii cysts is not known. Here, we provide evidence of immunological changes and TIGIT expression in infected mouse brains through flow cytometry and QPCR. The obtained results show that TIGIT expression on brain T cells rose considerably after infection. T. gondii infection triggered the conversion of TIGIT+ TCM cells to TIGIT+ TEM cells and reduced their cytotoxicity. During the whole period of T. gondii infection, high intensity and persistent expression of IFN-γ and TNF-α in brain and serum of mice. This study shows that chronic T. gondii infection increases TIGIT expression on brain T cells and affects their immune function.

Contribution of the TIM-3/Gal-9 immune checkpoint to tropical parasitic diseases

Neglected tropical parasitic diseases (NTD) are prevalent in many countries and cost-effective treatments remain urgently needed. Novel approaches have been proposed to address these diseases through an action on immune co-inhibitory checkpoints which are exploited by parasites to evade the immune system. Among these checkpoints, TIM-3 has been shown to play a key role in antiparasitic immunity via a repression and functional attenuation of CD4⁺ and/or CD8⁺ T-cells. The present review discusses the role of the TIM-3/galectin-9 checkpoint in seven major NTD: Chagas disease, leishmaniasis and malaria (3 trypanosomatid infections), schistosomiasis, toxoplasmosis, echinococcosis and filariasis (4 helminth infections). In each case, the role of the checkpoint has been analyzed and the use of anti-TIM-3 antibodies evaluated as a potential therapeutic approach. In general, the parasitic infection is coupled with an upregulation of TIM-3 expressed on T cells, but not necessarily with an exhaustion of those T cells. In several cases, the use of anti-TIM-3 antibodies represent a possible strategy to reinforce the clearance and to reduce the parasite load. Promising data have been reported in cases of leishmaniasis, malaria and schistosomiasis, whereas a similar approach proved much less efficient (if not deleterious) in cases of echinococcosis and the Chagas disease. Nevertheless, the TIM-3 checkpoint warrants further consideration as a potential immune target to combat these pathologies, using antibodies or drugs capable of reducing directly or indirectly the expression and function of the checkpoint, to restore an immune control.

Negative regulation of glial Tim-3 inhibits the secretion of inflammatory factors and modulates microglia to antiinflammatory phenotype after experimental intracerebral hemorrhage in rats

AIMS

To investigate the critical role of Tim-3 in the polarization of microglia in intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI).

METHODS

An in vivo ICH model was established by autologous whole blood injection into the right basal ganglia in rats. The primary cultured microglia were treated with oxygen-hemoglobin (OxyHb) to mimic ICH in vitro. In this experiment, specific siRNA for Tim-3 and recombinant human TIM-3 were exploited both in vivo and in vitro.

RESULTS

Tim-3 was increased in the brain after ICH, which mainly distributed in microglia, but not neurons and astrocytes. However, the blockade of Tim-3 by siRNA markedly reduced secretion of inflammatory factors, neuronal degeneration, neuronal cell death, and brain edema. Meanwhile, downregulation of Tim-3 promoted the transformation of microglia phenotype from M1 to M2 after ICH. Furthermore, upregulation of Tim-3 can increase the interaction between Tim-3 and Galectin-9 (Gal-9) and activate Toll-like receptor 4 (TLR-4) pathway after ICH. Increasing the expression of Tim-3 may be related to the activation of HIF-1α.

CONCLUSION

Tim-3 may be an important link between neuroinflammation and microglia polarization through Tim-3/Gal-9 and TLR-4 signaling pathways which induced SBI after ICH.

Toxoplasma gondii Genotype Determines Tim-3 Expression Levels in Splenic and Circulatory T Cells in Mice

Toxoplasma gondii is an obligatory intracellular parasite that causes a common infection in many warm-blooded animals. During infection, the host’s immune system plays an important role in confining the dissemination of the parasites in the hosts. T cell immunoglobulin- and mucin domain–containing molecule 3 (Tim-3) has been characterized as an important regulator in cell-mediated immune responses in various infections. Here, we compared Tim-3 expression on splenic and circulatory T, B cells and a few cytokines in the sera of mice infected with the more virulent type I (RH) vs. the low virulent type II (ME49) strain. Tim-3 expression on the splenic and circulatory T cells of mice infected with T. gondii (RH strain) was higher than that in mice infected with T. gondii (ME49 strain). T. gondii infection reduced the proportion of splenic helper T cells (Th) and cytotoxic T cells (Tc) and increased Tim-3 expression. Further, serum levels of interleukin (IL)-2, interferon γ, tumor necrosis factor (TNF)-α, IL-12p70, IL-22, IL-17A, and IL-5 increased significantly after infection. Mice infected with T. gondii (ME49 strain) showed higher levels of TNF-α, IL-17A, IL-12p70, and IL-22 than that infected by the RH strain. Our study revealed that T. gondii strains may have their inherent ability in triggering different host immune responses, which may explain the clinical variation in diseases severity after infection.

Upregulated Tim-3/galectin-9 expressions in acute lung injury in a murine malarial model

Malaria is the most relevant parasitic disease worldwide, and severe malaria is characterized by cerebral edema, acute lung injury (ALI), and multiple organ dysfunctions; however, the mechanisms of lung damage need to be better clarified. In this study, we used Kunming outbred mice infected with Plasmodium berghei ANKA (PbANKA) to elucidate the profiles of T cell immunoglobulin and mucin domain-3 (Tim-3) and its ligand galecin-9 (Gal-9) in the development of ALI. Mice were injected intraperitoneally with 10⁶PbANKA-infected red blood cells. The lungs and mediastinal lymph nodes (MLNs) were harvested at days 5, 10, 15, and 20 post infections (p.i.). The grade of lung injury was histopathologically evaluated. Tim-3- and Gal-9-positive cells in the lungs and MLNs were stained by immunohistochemistry, and the messenger RNA (mRNA) expressions of Tim-3, Gal-9, and related cytokines were assessed using quantitative real-time polymerase chain reaction (qRT-PCR). Bronchoalveolar lavage fluid (BALF) analyses were performed from days 18 to 20 p.i. The results showed that the pathological severities in the lungs were increased with times and the total protein level in the BALFs was significantly elevated in PbANKA-infected mice. The numbers of Gal-9⁺ and Tim-3⁺ cells in the lungs were significantly increased, and the mRNA levels of both Gal-9 and Tim-3 in the lungs and MLNs were over-expressed in PbANKA-infected mice. In conclusion, our data suggested that Tim-3/Gal-9 may play a role in PbANKA-induced ALI.

Identification of GLA/SE as an effective adjuvant for the induction of robust humoral and cell-mediated immune responses to EBV-gp350 in mice and rabbits

Childhood infection with Epstein-Barr virus (EBV) is often asymptomatic and may result in mild flu-like symptoms, but exposure during adolescence and young adulthood can lead to acute infectious mononucleosis (AIM) with a pathology characterized by swollen lymph nodes, sore throat, and severe fatigue lasting weeks or months. A vaccine targeting the envelope glycoprotein gp350 adjuvanted with aluminum hydroxide complexed with the TLR4 agonist monophosphoryl lipid A (MPLA) achieved a 78% reduction in AIM incidence in a small phase II trial of college-age individuals, but development of this vaccine was halted by the manufacturer. Here, we report the evaluation in mice and rabbits of an EBV-gp350 vaccine combined with an adjuvant composed of the synthetic TLR4 agonist glucopyranosyl lipid A (GLA) integrated into stable emulsion (SE). In mice, GLA/SE-adjuvanted gp350 generated high IgG titers (both IgG1 and IgG2a/c subtypes), elevated EBV-neutralizing antibody titers, and robust poly-functional anti-gp350 CD4(+) T cell responses. In addition, GLA/SE routinely demonstrated superior performance over aluminum hydroxide in all immunological readouts, including induction of durable neutralizing antibody titers out to at least 1 year post-vaccination. Both components of the GLA/SE adjuvant were found to be required to get optimal responses in both arms of the immune response: specifically, SE for neutralizing antibodies and GLA for induction of T cell responses. Furthermore, this vaccine also elicited high neutralizing antibody titers in a second species, rabbit. These promising results suggest that clinical development of a vaccine comprised of EBV-gp350 plus GLA/SE has the potential to prevent AIM in post-adolescents.

Transcriptomic analysis of global changes in cytokine expression in mouse spleens following acute Toxoplasma gondii infection

Toxoplasma gondii is a global pathogen that infects a wide range of animals and humans. During T. gondii infection, the spleen plays an important role in coordinating the adaptive and innate immune responses. However, there is little information regarding the changes in global gene expression within the spleen following T. gondii infection. To address this gap in knowledge, we examined the transcriptome of the mouse spleen following T. gondii infection. We observed differential expression of 2310 transcripts under these conditions. Analysis of KEGG and GO enrichment indicated that T. gondii alters multiple immune signaling cascades. Most of differentially expressed GO terms and pathways were downregulated, while immune-related GO terms and pathways were upregulated with response to T. gondii infection in mouse spleen. Most cytokines were upregulated in infected spleens, and all differentially expressed chemokines were upregulated which enhanced the immune cells chemotaxis to promote recruitment of immune cells, such as neutrophils, eosinophils, monocytes, dendritic cells, macrophages, NK cells, basophils, B cells, and T cells. Although IFN-γ-induced IDO (Ido1) was upregulated in the present study, it may not contribute a lot to the control of T. gondii because most differentially expressed genes involved in tryptophan metabolism pathway were downregulated. Innate immunity pathways, including cytosolic nucleic acid sensing pathway and C-type lectins-Syk-Card9 signaling pathways, were upregulated. We believe our study is the first comprehensive attempt to define the host transcriptional response to T. gondii infection in the mouse spleen.

The correlation of Tim-3 and IFN-γ expressions in mice infected with Toxoplasma gondii during gestation

The immunoinhibitory receptor T cell immunoglobulin domain and mucin domain-1 (Tim-1) and Tim-3 participate in the regulation of Th immune response as well as innate immunity. However, there is no report about the expression of Tim genes in Toxoplasma gondii-infected experimental models during pregnancy. In this study, Kunming outbred pregnant mice were infected with RH strain of T. gondii through vagina at days 10 to 16 of gestation, and the mRNA expressions of Tim-1, Tim-3, interleukin (IL)-4, and interferon (IFN)-γ in the placentas, uteri, and draining lumber aortic lymph nodes (LALNs) at day 18 of gestation were analyzed using quantitative real-time PCR (qRT-PCR). Compared with uninfected pregnant controls, significantly increased levels of IFN-γ and Tim-3 were detected in the placentas (P < 0.001), uteri (P = 0.003 and P = 0.017, respectively), and LALNs (P = 0.003 and P = 0.025, respectively) of T. gondii-infected mice; there were positive and significant correlations between Tim-3 and IFN-γ mRNA expression levels in the placentas (R(2) = 0.6331, P = 0.0011), uteri (R(2) = 0.5658, P = 0.003), and LALNs (R(2) = 0.5583, P = 0.0033) of infected mice. Tim-1 (P = 0.002) and IL-4 (P = 0.003) expressions were significantly increased in the placentas, but Tim-1 were significantly decreased in the uteri (P = 0.013) and LALNs (P < 0.001) of infected pregnant mice in comparison of uninfected pregnant controls. Our data suggested that Tim-3 may play a regulatory role in T. gondii-infected pregnant mouse model.