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

Adenosine-related small molecules show utility of recall antigen assay to screen compounds for off-target effects on memory T cells

Extracellular adenosine suppresses T cell immunity in the tumor microenvironment and in vitro treatment of memory T cells with adenosine can suppress antigen-mediated memory T cell expansion. We describe utilizing the recall antigen assay platform to screen small molecule drug off-target effects on memory T cell expansion/function using a dosing regimen based on adenosine treatment. As a proof of principle, we show low dose GS-5734, a monophosphoramidate prodrug of an adenosine analog, does not alter memory T cell recall at lower doses whereas toxicity observed at high dose favors antigen-specific memory T cell survival/proliferation over non-specific CD8⁺ T cells. Conversely, parent nucleoside GS-441524 at high dosage does not result in cellular toxicity and reduces antigen-specific T cell recall in most donors. Despite similar chemical structure, these drugs displayed opposing effects on memory T cell expansion and viability highlighting the sensitivity of this assay setup in screening compounds for off-target effects.

Immunophenotypic characterization of TCR γδ T cells and MAIT cells in HIV-infected individuals developing Hodgkin's lymphoma

Background

Despite successful combined antiretroviral therapy (cART), the risk of non-AIDS defining cancers (NADCs) remains higher for HIV-infected individuals than the general population. The reason for this increase is highly disputed. Here, we hypothesized that T-cell receptor (TCR) γδ cells and/or mucosal-associated invariant T (MAIT) cells might be associated with the increased risk of NADCs. γδ T cells and MAIT cells both serve as a link between the adaptive and the innate immune system, and also to exert direct anti-viral and anti-tumor activity.

Methods

We performed a longitudinal phenotypic characterization of TCR γδ cells and MAIT cells in HIV-infected individuals developing Hodgkin’s lymphoma (HL), the most common type of NADCs. Cryopreserved PBMCs of HIV-infected individuals developing HL, matched HIV-infected controls without (w/o) HL and healthy controls were used for immunophenotyping by polychromatic flow cytometry, including markers for activation, exhaustion and chemokine receptors.

Results

We identified significant differences in the CD4⁺ T cell count between HIV-infected individuals developing HL and HIV-infected matched controls within 1 year before cancer diagnosis. We observed substantial differences in the cellular phenotype mainly between healthy controls and HIV infection irrespective of HL. A number of markers tended to be different in Vδ1 and MAIT cells in HIV⁺HL⁺ patients vs. HIV⁺ w/o HL patients; notably, we observed significant differences for the expression of CCR5, CCR6 and CD16 between these two groups of HIV⁺ patients.

Conclusion

TCR Vδ1 and MAIT cells in HIV-infected individuals developing HL show subtle phenotypical differences as compared to the ones in HIV-infected controls, which may go along with functional impairment and thereby may be less efficient in detecting and eliminating malignant cells. Further, our results support the potential of longitudinal CD4⁺ T cell count analysis for the identification of patients at higher risk to develop HL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13027-021-00365-4.

Disease Progression in Children with Perinatal HIV Correlates with Increased PD-1+ CD8 T Cells that Coexpress Multiple Immune Checkpoints

BACKGROUND

PD-1 marks exhausted T cells, with weak effector functions. Adults living with HIV have increased levels of PD-1+ CD8 T cells that correlate with HIV disease progression, yet little is known about the role of PD-1+ CD8 T cells in children with perinatal HIV.

METHODS

We enrolled 76 Kenyan children with perinatal HIV and 43 children who were HIV unexposed and quantified PD-1 levels on CD8 T cells, their coexpression with immune checkpoints (IC) 2B4, CD160 and TIM3, correlates with immune activation and HIV disease progression and HIV-specific and non-specific proliferative responses.

RESULTS

PD-1+ CD8 T cell frequencies are elevated in children with perinatal HIV and associated with disease progression. The majority of PD-1+ CD8 T cells coexpress additional ICs. ART initiation lowers total PD-1 levels and coexpression of multiple ICs. The frequency of PD-1 + 2B4+CD160+TIM3- in PD-1+ CD8 T cells, predicts weaker HIV-specific proliferative responses, suggesting this subset is functionally exhausted.

CONCLUSION

Children with perinatal HIV have high PD-1+ CD8 T cells that are a heterogeneous population differentially coexpressing multiple ICs. Understanding the complex interplay of ICs is essential to guide the development of PD-1 directed immunotherapies for pediatric HIV remission and cure.

TIM-3 drives temporal differences in restimulation-induced cell death sensitivity in effector CD8+ T cells in conjunction with CEACAM1

Immune homeostasis depends upon effective clearance of pathogens while simultaneously preventing autoimmunity and immunopathology in the host. Restimulation-induced cell death (RICD) is one such mechanism where by activated T cells receive subsequent antigenic stimulation, reach a critical signal threshold through the T cell receptor (TCR), and commit to apoptosis. Many details of this process remain unclear, including the role of co-stimulatory and co-inhibitory proteins that influence the TCR signaling cascade. Here we characterize the role of T cell immunoglobulin and mucin domain containing 3 (TIM-3) in RICD regulation. TIM-3 protected newly activated CD8+ effector T cells from premature RICD during clonal expansion. Surprisingly, however, we found that TIM-3 potentiated RICD in late-stage effector T cells. The presence of TIM-3 increased proximal TCR signaling and proapoptotic protein expression in late-stage effector T cells, with no consistent signaling effects noted in newly activated cells with or without TIM-3. To better explain these differences in TIM-3 function as T cells aged, we characterized the temporal pattern of TIM-3 expression in effector T cells. We found that TIM-3 was expressed on the surface of newly activated effector T cells, but remained largely intracellular in late-stage effector cells. Consistent with this, TIM-3 required a ligand to prevent early RICD, whereas ligand manipulation had no effects at later stages. Of the known TIM-3 ligands, carcinoembryonic antigen-related cell adhesion molecule (CEACAM1) showed the greatest difference in surface expression over time and also protected newly activated cells from premature RICD, with no measurable effects in late-stage effectors. Indeed, CEACAM1 enabled TIM-3 surface expression on T cells, implying a co-dependency for these proteins in protecting expanding T cells from premature RICD. Our findings suggest that co-signaling proteins like TIM-3 and CEACAM1 can alter RICD sensitivity at different stages of the effector T cell response, with important implications for checkpoint blockade therapy.

High levels of Tim-3+Foxp3+Treg cells in the tumor microenvironment is a prognostic indicator of poor survival of diffuse large B cell lymphoma patients

Foxp3⁺Treg cells display phenotypic and functional heterogeneity, which express high levels of T cell immunoglobulin and mucin-domain containing-3 (Tim-3) in the tumor microenvironment (TME) of colorectal and lung cancer. High abundance of Tim-3⁺Foxp3⁺Treg (TFT) cells are associated with poor prognosis in these patients. However, the expression patterns and roles of TFT cells in TME of diffuse large B cell lymphoma (DLBCL) remain to be established. Double immunofluorescence and flow cytometry analyses were employed to investigate TFT cell enrichment in paraffin-embedded fresh tumor tissues from patients with DLBCL. Spearman's or Pearson's correlation and Kaplan-Meier survival analyses were further applied to decide the prognostic value of TFT cell levels in DLBCL. The IL-10-secreting function of TFT cells in vitro was examined via flow cytometry and ELISA. Our results showed for the first time that TFT cells are highly enriched in TME of DLBCL patients and associated with predictions of poor prognoses. TFT cell-induced secretion of IL-10 in the TME was suppressed by an anti-Tim-3 antibody in vitro. In conclusion, high abundance of TFT cells in the TME is predictive of poor outcomes of DLBCL. TFT cells promote DLBCL development partly by secreting IL-10 in the TME. Anti-Tim-3 antibodies (that block IL-10 secretion) may present an effective therapeutic agent for DLBCL.

The inhibitory receptor Tim-3 fails to suppress IFN-γ production via the NFAT pathway in NK-cell, unlike that in CD4+ T cells

Background

T cell immunoglobulin and mucin domain-containing-3 (Tim-3) is a negative regulator expressed on T cells, and is also expressed on natural killer (NK) cells. The function of Tim-3 chiefly restricts IFNγ-production in T cells, however, the impact of Tim-3 on NK cell function has not been clearly elucidated.

Results

In this study, we demonstrated down-regulation of Tim-3 expression on NK cells while Tim-3 is upregulated on CD4⁺ T cells during HIV infection. Functional assays indicated that Tim-3 mediates suppression of CD107a degranulation in NK cells and CD4⁺ T cells, while it fails to inhibit the production of IFN-γ by NK cells. Analyses of downstream pathways using an antibody to block Tim-3 function demonstrated that Tim-3 can inhibit ERK and NFκB p65 signaling; however, it failed to suppress the NFAT pathway. Further, we found that the NFAT activity in NK cells was much higher than that in CD4⁺ T cells, indicating that NFAT pathway is important for promotion of IFN-γ production by NK cells.

Conclusions

Thus, our data show that the expression of Tim-3 on NK cells is insufficient to inhibit IFN-γ production. Collectively, our findings demonstrate a potential mechanism of Tim-3 regulation of NK cells and a target for HIV infection immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00417-9.

Blood Levels of Galectin-9, an Immuno-Regulating Molecule, Reflect the Severity for the Acute and Chronic Infectious Diseases

Galectin-9 (Gal-9) is a β-galactoside-binding lectin capable of promoting or suppressing the progression of infectious diseases. This protein is susceptible to cleavage of its linker-peptides by several proteases, and the resulting cleaved forms, N-terminal carbohydrate recognition domain (CRD) and C-terminal CRD, bind to various glycans. It has been suggested that full-length (FL)-Gal-9 and the truncated (Tr)-Gal-9s could exert different functions from one another via their different glycan-binding activities. We propose that FL-Gal-9 regulates the pathogenesis of infectious diseases, including human immunodeficiency virus (HIV) infection, HIV co-infected with opportunistic infection (HIV/OI), dengue, malaria, leptospirosis, and tuberculosis (TB). We also suggest that the blood levels of FL-Gal-9 reflect the severity of dengue, malaria, and HIV/OI, and those of Tr-Gal-9 markedly reflect the severity of HIV/OI. Recently, matrix metallopeptidase-9 (MMP-9) was suggested to be an indicator of respiratory failure from coronavirus disease 2019 (COVID-19) as well as useful for differentiating pulmonary from extrapulmonary TB. The protease cleavage of FL-Gal-9 may lead to uncontrolled hyper-immune activation, including a cytokine storm. In summary, Gal-9 has potential to reflect the disease severity for the acute and chronic infectious diseases.

Soluble TIM3 and Its Ligands Galectin-9 and CEACAM1 Are in Disequilibrium During Alcohol-Related Liver Disease and Promote Impairment of Anti-bacterial Immunity

BACKGROUND AND AIMS

Immunoregulatory checkpoint receptors (CR) contribute to the profound immunoparesis observed in alcohol-related liver disease (ALD) and in vitro neutralization of inhibitory-CRs TIM3/PD1 on anti-bacterial T-cells can rescue innate and adaptive anti-bacterial immunity. Recently described soluble-CR forms can modulate immunity in inflammatory conditions, but the contributions of soluble-TIM3 and soluble-PD1 and other soluble-CRs to immune derangements in ALD remain unclear.

METHODS

In Alcoholic Hepatitis (AH; n = 19), alcohol-related cirrhosis (ARC; n = 53) and healthy control (HC; n = 27) subjects, we measured by Luminex technology (i) plasma levels of 16 soluble-CRs, 12 pro/anti-inflammatory cytokines and markers of gut bacterial translocation; (ii) pre-hepatic, post-hepatic and non-hepatic soluble-CR plasma levels in ARC patients undergoing TIPS; (iii) soluble-CRs production from ethanol-treated immunocompetent precision cut human liver slices (PCLS); (iv) whole-blood soluble-CR expression upon bacterial challenge. By FACS, we assessed the relationship between soluble-TIM3 and membrane-TIM3 and rescue of immunity in bacterial-challenged PBMCs.

RESULTS

Soluble-TIM3 was the dominant plasma soluble-CR in ALD vs. HC (p = 0.00002) and multivariate analysis identified it as the main driver of differences between groups. Soluble-CRs were strongly correlated with pro-inflammatory cytokines, gut bacterial translocation markers and clinical indices of disease severity. Ethanol exposure or bacterial challenge did not induce soluble-TIM3 production from PCLS nor from whole-blood. Bacterial challenge prompted membrane-TIM3 hyperexpression on PBMCs from ALD patient's vs. HC (p < 0.002) and was inversely correlated with plasma soluble-TIM3 levels in matched patients. TIM3 ligands soluble-Galectin-9 and soluble-CEACAM1 were elevated in ALD plasma (AH > ARC; p < 0.002). In vitro neutralization of Galectin-9 and soluble-CEACAM1 improved the defective anti-bacterial and anti-inflammatory cytokine production from E. coli-challenged PBMCs in ALD patients.

CONCLUSIONS

Alcohol-related liver disease patients exhibit supra-physiological plasma levels of soluble-TIM3, particularly those with greater disease severity. This is also associated with increased levels of soluble TIM3-ligands and membrane-TIM3 expression on immune cells. Soluble-TIM3 can block the TIM3-ligand synapse and improve anti-bacterial immunity; however, the increased levels of soluble TIM3-binding ligands in patients with ALD negate any potential immunostimulatory effects. We believe that anti-TIM3 neutralizing antibodies currently in Phase I clinical trials or soluble-TIM3 should be investigated further for their ability to enhance anti-bacterial immunity. These agents could potentially represent an innovative immune-based supportive approach to rescue anti-bacterial defenses in ALD patients.

Beyond PD-1: The Next Frontier for Immunotherapy in Melanoma

The advent of first and second-generation immune checkpoint blockade (ICI) has resulted in improved survival of patients with metastatic melanoma over the past decade. However, the majority of patients ultimately progress despite these treatments, which has served as an impetus to consider a range of subsequent therapies. Many of the next generation of immunotherapeutic agents focus on modifying the immune system to overcome resistance to checkpoint blockade. ICI resistance can be understood as primary, or acquired-where the latter is the most common scenario. While there are several postulated mechanisms by which resistance, particularly acquired resistance, occurs, the predominant escape mechanisms include T cell exhaustion, upregulation of alternative inhibitory checkpoint receptors, and alteration of the tumor microenvironment (TME) into a more suppressive, anti-inflammatory state. Therapeutic agents in development are designed to work by combating one or more of these resistance mechanisms. These strategies face the added challenge of minimizing immune-related toxicities, while improving antitumor efficacy. This review focuses upon the following categories of novel therapeutics: 1) alternative inhibitory receptor pathways; 2) damage- or pathogen-associated molecular patterns (DAMPs/PAMPs); and 3) immune cell signaling mediators. We present the current state of these therapies, including preclinical and clinical data available for these targets under development.

Immunomodulation by Inflammation during Liver and Gastrointestinal Tumorigenesis and Aging

Chronic inflammation is thought to promote tumorigenesis and metastasis by several mechanisms, such as affecting tumor cells directly, establishing a tumor-supporting microenvironment, enhancing tumor angiogenesis, and suppressing antitumor immunity. In this review, we discuss the recent advances in our understanding of how inflammation induces the immunosuppressive tumor microenvironment, such as increasing the level of pro-inflammatory cytokines, chemokines, and immunosuppressive molecules, inducing immune checkpoint molecules and cytotoxic T-cell exhaustion, and accumulating regulatory T (Treg) cells and myeloid-derived suppressor cells (MDSCs). The suppression of antitumor immunity by inflammation is especially examined in the liver and colorectal cancer. In addition, chronic inflammation is induced during aging and causes age-related diseases, including cancer, by affecting immunity. Therefore, we also discuss the age-related diseases regulated by inflammation, especially in the liver and colon.

Role of Soluble T-Cell Immunoglobulin Mucin Domain-3 in Differentiating Nontuberculous Mycobacterial Lung Disease from Pulmonary Colonization

BACKGROUND

Differentiating between nontuberculous mycobacterial lung disease (NTM-LD) and pulmonary NTM colonization (NTM-Col) is difficult. Compared with healthy controls, patients with NTM-LD generally present immune tolerance along with increased expressions of T-cell immunoglobulin mucin domain-3 (TIM-3) and programmed cell death-1 (PD-1) on T lymphocytes. However, the role of soluble TIM-3 (sTIM-3) and soluble PD-1 (sPD-1) in differentiating NTM-LD from NTM colonization (NTM-Col) remains unclear.

METHODS

Patients with NTM-positive respiratory samples and controls were enrolled from 2016 to 2019. Patients were classified into NTM-Col and NTM-LD groups. Levels of sTIM-3, sPD-1, soluble PD-ligand-1 (sPD-L1), and TIM-3 expression were measured. Factors associated with NTM-LD were analyzed by logistical regression.

RESULTS

TIM-3 expression on CD4+ and CD8+ T lymphocytes were highest in NTM-LD group, followed by NTM-Col, and control (P=.017 and P=.011 for trend). sTIM-3 elevated in the NTM-Col group compared with the NTM-LD and control groups (856.3±518.7 vs. 595.3±352.6pg/mL, P=.009; vs. 437.0±267.4pg/mL, P<.001). Levels of sPD-1 and sPD-L1 were similar among groups. Among the 79 NTM-positive patients, sTIM-3 was associated with NTM-LD (100-pg/mL increase, adjusted odds ratio (aOR) 0.658 [95% CI, 0.502-0.864], P=.003). Patients with ≥2 risk factors (sTIM-3≤530pg/mL, BMI≤22.5, and radiographic score ≥5) were 13 times more likely to exhibit NTM-LD than those without (aOR 13.234 [2.983-58.709], P=.001).

CONCLUSIONS

sTIM-3 was an independent factor for differentiating NTM-LD from NTM-Col, suggesting the immunologic role of sTIM-3 in NTM-LD pathogenesis. By assessing sTIM-3 levels and other risk factors, physicians may be able to identify NTM-LD cases in a simplified manner.

A Matter of Life or Death: Productively Infected and Bystander CD4 T Cells in Early HIV Infection

CD4 T cell death or survival following initial HIV infection is crucial for the development of viral reservoirs and latent infection, making its evaluation critical in devising strategies for HIV cure. Here we infected primary CD4 T cells with a wild-type HIV-1 and investigated the death and survival mechanisms in productively infected and bystander cells during early HIV infection. We found that HIV-infected cells exhibited increased programmed cell death, such as apoptosis, pyroptosis, and ferroptosis, than uninfected cells. However, productively infected (p24⁺) cells and bystander (p24^-) cells displayed different patterns of cell death due to differential expression of pro-/anti-apoptotic proteins and signaling molecules. Cell death was triggered by an aberrant DNA damage response (DDR), as evidenced by increases in γH2AX levels, which inversely correlated with telomere length and telomerase levels during HIV infection. Mechanistically, HIV-infected cells exhibited a gradual shortening of telomeres following infection. Notably, p24⁺ cells had longer telomeres compared to p24^- cells, and telomere length positively correlated with the telomerase, pAKT, and pATM expressions in HIV-infected CD4 T cells. Importantly, blockade of viral entry attenuated the HIV-induced inhibition of telomerase, pAKT, and pATM as well as the associated telomere erosion and cell death. Moreover, ATM inhibition promoted survival of HIV-infected CD4 T cells, especially p24⁺ cells, and rescued telomerase and AKT activities by inhibiting cell activation, HIV infection, and DDR. These results indicate that productively infected and bystander CD4 T cells employ different mechanisms for their survival and death, suggesting a possible pro-survival, pro-reservoir mechanism during early HIV infection.

Effect of the use of Galectin-9 and blockade of TIM-3 receptor in the latent cellular reservoir of HIV-1

Reactivation of latent HIV-1 is a necessary step for the purging of the viral reservoir, although it does not seem to be enough. The stimulation of HIV-1 specific cytotoxic T lymphocytes (CTL) may be just as essential for this purpose. In this study, we aimed to show the effect of galectin-9 (Gal-9), known to revert HIV-1 latency, in combination with the blockade of TIM-3, a natural receptor for Gal-9 and an exhaustion marker. We confirmed the ability of Gal-9 to reactivate latent HIV-1 in Jurkat-LAT-GFP cells, as well as in an IL-7-based cellular model. This reactivation was not mediated via the TIM-3 receptor, but rather by the recognition of the Gal-9 of a specific oligosaccharide pattern of resting memory CD4⁺ T cells' surfaces. The potency of Gal-9 in inducing transcription of latent HIV-1 was equal to or greater than that of other latency-reversing agents (LRA). Furthermore, the combination of Gal-9 with other LRA did not show synergistic effects in the reactivation of the latent virus. To evaluate the impact of TIM-3 inhibition on the CTL-response, different co-culture experiments with CD4⁺T, CD8⁺ T, and NK cells were performed. Our data showed that blocking TIM-3 was associated with control of viral replication in both in vitro and ex vivo models in cells from PLWH on antiretroviral therapy. A joint strategy of the use of Gal-9 to reactivate latent HIV-1 and the inhibition of TIM-3 to enhance the HIV-1 CTL specific-response was associated with control of the replication of the virus that was being reactivated, thus potentially contributing to the elimination of the viral reservoir. Our results place this strategy as a promising approach to be tested in future studies. Reactivation of latent-HIV-1 by Gal-9 and reinvigoration of CD8⁺ T cells by TIM-3 blockade could be used separately or in combination.ImportanceHIV-1 infection is a health problem of enormous importance that still causes significant mortality. Antiretroviral treatment (ART) has demonstrated efficacy in the control of HIV-1 replication, decreasing the morbidity and mortality of the infection, but it cannot eradicate the virus. In our work, we tested a protein, galectin-9 (Gal-9), an HIV-1 latency-reversing agent, using an in vitro cellular model of latency and in cells from people living with HIV-1 (PLWH) on antiretroviral therapy. Our results confirmed the potential role of Gal-9 as a molecule with a potent HIV-1 reactivation capacity. More importantly, using a monoclonal antibody against T cell immunoglobulin and the mucin domain-containing molecule 3 (TIM-3) receptor we were able to enhance the HIV-1 cytotoxic T lymphocytes (CTL) specific response to eliminate the CD4⁺ T cells in which the virus had been reactivated. When used together, i.e., Gal-9 and TIM-3 blockade, control of the replication of HIV-1 was observed, suggesting a decrease in the cellular reservoir.

Pronounce expression of Tim-3 and CD39 but not PD1 defines CD8 T cells in critical Covid-19 patients

Background

During viral infection, inhibitory receptors play a key role in regulating CD8 T-cell activity. The objective of this research was to investigate programmed cell death protein 1 (PD-1), T-cell immunoglobulin and mucin domain-containing protein-3 (TIM-3), and CD39 exhaustion markers in CD8 T cells of new coronavirus disease-2019 (COVID-19) patients.

Methods

A total of 44 patients with COVID-19 (17 subjects in a critical group and 27 patients in a non-critical group) and 14 healthy controls, who were admitted to Hospitals in Babol, were recruited to the study. In subjects' peripheral blood mononuclear cells (PBMCs), we compared the phenotype of CD8 T lymphocytes, expressing PD-1, TIM-3, or CD39, both alone and in various combinations.

Results

The findings showed that the percentage of CD8⁺ cells was significantly lower in patients. Critical and non-critical patients were more likely than healthy controls to have an escalated frequency of CD8⁺ TIM-3⁺, CD8⁺ CD39⁺, and CD8⁺ TIM-3⁺ CD39⁺ cells. No significant differences were observed between all groups in the CD8⁺ PD-1⁺ cell counts. There was also no difference between three groups regarding the counts of CD8⁺ TIM-3⁺ PD-1⁺, CD8⁺ PD-1⁺ CD39⁺, and CD8⁺ TIM-3⁺ PD-1⁺ CD39⁺ cells. The counts of non-exhausted cells were significantly lower in critical and non-critical individuals compared to the healthy individuals’ value.

Conclusion

Patients, infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), altered exhausted CD8 T lymphocytes with CD39 and TIM-3 exhaustion markers, which may account the dysregulated immune response found in COVID-19.

TIM-3 pathway dysregulation and targeting in cancer

INTRODUCTION

Dysfunction of the immune system is a hallmark of cancer. Through increased understanding of the complex interactions between immunity and cancer, immunotherapy has emerged as a treatment modality for different types of cancer. Promising activity with immunotherapy has been reported in numerous malignancies, but challenges such as limited response rates and treatment resistance remain. Furthermore, outcomes with this therapeutic approach in hematologic malignancies are even more limited than in solid tumors. T-cell immunoglobulin domain and mucin domain 3 (TIM-3) has emerged as a potential immune checkpoint target in both solid tumors and hematologic malignancies. TIM-3 has been shown to promote immune tolerance, and overexpression of TIM-3 is associated with more aggressive or advanced disease and poor prognosis.

AREAS COVERED

This review examines what is currently known regarding the biology of TIM-3 and clinical implications of targeting TIM-3 in cancer. Particular focus is given to myeloid malignancies.

EXPERT OPINION

The targeting of TIM-3 is a promising therapeutic approach in cancers, including hematologic cancers such as myeloid malignancies which have not benefited much from current immunotherapeutic treatment approaches. We anticipate that with further clinical evaluation, TIM-3 blockade will emerge as an important treatment strategy in myeloid malignancies.

Galectin-9 as a biomarker of disease severity

Galectin-9 (Gal-9) is a β-galactoside binding lectin known for its immunomodulatory role in various microbial infections. Gal-9 is expressed in all organ systems and localized in the nucleus, cell surface, cytoplasm and the extracellular matrix. It mediates host-pathogen interactions and regulates cell signalling via binding to its receptors. Gal-9 is involved in many physiological functions such as cell growth, differentiation, adhesion, communication and death. However, recent studies have emphasized on the elevated levels of Gal-9 in autoimmune disorders, viral infections, parasitic invasion, cancer, acute liver failure, atopic dermatitis, chronic kidney disease, type-2 diabetes, coronary artery disease, atherosclerosis and benign infertility-related gynecological disorders. In this paper we have reviewed the potential of Gal-9 as a reliable, sensitive and non-invasive biomarker of disease severity. Tracking changes in Gal-9 levels and its implementation as a biomarker in clinical practice will be an important tool to monitor disease activity and facilitate personalized treatment decisions.

Levels of Human Immunodeficiency Virus DNA Are Determined Before ART Initiation and Linked to CD8 T-Cell Activation and Memory Expansion

Initiation of antiretroviral therapy (ART) in early compared with chronic human immunodeficiency virus (HIV) infection is associated with a smaller HIV reservoir. This longitudinal analysis of 60 individuals who began ART during primary HIV infection (PHI) investigates which pre- and posttherapy factors best predict HIV DNA levels (a correlate of reservoir size) after treatment initiation during PHI. The best predictor of HIV DNA at 1 year was pre-ART HIV DNA, which was in turn significantly associated with CD8 memory T-cell differentiation (effector memory, naive, and T-bet⁻Eomes⁻ subsets), CD8 T-cell activation (CD38 expression) and T-cell immunoglobulin and mucin-domain containing-3 (Tim-3) expression on memory T cells. No associations were found for any immunological variables after 1 year of ART. Levels of HIV DNA are determined around the time of ART initiation in individuals treated during PHI. CD8 T-cell activation and memory expansion are linked to HIV DNA levels, suggesting the importance of the initial host-viral interplay in eventual reservoir size.

Tim-3 associated with apoptotic NK cells and disease activity in SLE

T cell immunoglobulin and mucin domain-containing molecule-3 (Tim-3) has been found to play important roles in systemic lupus erythematosus (SLE), however, whether Tim-3 is involved in apoptosis of NK cells in SLE remains unknown. The proportion of CD3−CD56+ NK cells and the percentage of AnnexinV+ NK cells were analyzed by flow cytometry in SLE patients and healthy controls. Tim-3 expression on NK cells was also evaluated by flow cytometry. We firstly observed a decreased proportion of NK cells and an increased proportion of apoptotic NK cells in SLE patients. The proportion of apoptotic NK cells was positively correlated with anti-dsDNA and SLEDAI. Tim-3 expression on NK cells was up-regulated in SLE patients. Further analysis showed that Tim-3 expression on NK cells was negatively correlated with the proportion of apoptotic NK cells, anti-dsDNA and SLEDAI, while positively correlated with the proportion of NK cells. The present results suggest that Tim-3 might play roles in SLE by regulating the apoptosis of NK cells and Tim-3 might serve as a potential target for the treatment of SLE.

T Cells: Warriors of SARS-CoV-2 Infection

Severe infection with severe acute respiratory syndrome coronavirus (SARS-CoV)-2 is characterized by massive cytokine release and T cell loss. The exaggerated host immune response, incapable of viral clearance, instead aggravates respiratory distress, as well as cardiac, and/or damage to other organs. The mortality pattern of SARS-CoV-2 infection, higher in older versus younger adults and almost absent in children, is possibly caused by the effects of age and pre-existing comorbidities on innate and adaptive immunity. Here, we speculate that the abnormal and excessive immune response to SARS-CoV-2 infection partly depends on T cell immunological memory, which is more pronounced in adults compared with children, and may significantly contribute to immunopathology and massive collateral damage in coronavirus disease 2019 (COVID-19) patients.

Demographic and clinical factors associated with immune reconstitution in HIV/HBV co-infected and HIV mono-infected patients: a retrospective cohort study

OBJECTIVES

To describe the clinical characteristics and factors associated with CD4 T-cell count and CD4/CD8 ratio restoration in HIV mono-infected and HIV/HBV co-infected individuals, and to explore liver and renal functional changes in both groups.

METHODS

A retrospective cohort study was performed including 356 HIV/HBV co-infected and 716 HIV mono-infected participants who initiated antiretroviral therapy (ART) during 2013-2017 in Beijing Youan Hospital, China. Demographic and clinical characteristics were compared between the two groups, using χ² and Mann-Whitney non-parametric tests. Bivariate and multivariate Cox regression models were used to test their association.

RESULTS

Baseline HIV viral load and ART regimen were found to be significantly associated with CD4 T-cell restoration among HIV-infected participants, whereas baseline HIV viral load was the only significant factor associated with CD4 T-cell restoration in HIV/HBV co-infected participants. The final model showed that baseline HIV viral load and ART regimen were significantly associated with CD4/CD8 ratio restoration among HIV-infected participants, while baseline HIV viral load was the significant factor. Liver and renal functions were similar at the endpoint (P > 0.05).

CONCLUSIONS

Baseline HIV viral load count was found to be the key factor affecting immune restoration in both HIV and HIV/HBV individuals. Future multi-wave prospective studies are needed to clarify the potential biological mechanism.

Association of soluble T cell immunoglobulin domain and mucin-3 (sTIM-3) and mac-2 binding protein glycosylation isomer (M2BPGi) in patients with autoimmune hepatitis

Background

Autoimmune hepatitis (AIH) is a disorder of unknown etiology in which immune-mediated liver injury progress to cirrhosis or hepatocellular carcinoma (HCC). The aim of the present study was to determine whether circulating soluble TIM3 (sTIM3) is elevated in patients with AIH patients and whether sTIM-3 levels are associated with clinical parameters of AIH.

Methods

We enrolled 123 Japanese patients with AIH who were identified from the National Hospital Organization–AIH-liver–network database, as well as 32 patients with chronic hepatitis C (CHC), 30 patients with primary biliary cholangitis (PBC) and healthy control subjects. Serum sTIM-3 concentrations were quantified by ELISA.

Results

Serum levels of sTIM-3 were significantly higher in AIH patients (median 4865 pg/ml; [interquartile range (IQR); 3122–7471]) compared to those in CHC (1026 pg/ml [IQR: 806–1283] p<0.001), PBC (2395 pg/ml [IQR: 2012–3422] p<0.001) or healthy controls (1285 pg/ml [IQR: 1098–1812] p<0.001). In AIH group, serum sTIM-3 were correlated with alanine aminotransferase (ALT), or total bilirubin (TB) and negatively correlated with serum levels of albumin (Alb). Serum levels of sTIM-3 were also strongly correlated with Mac-2 binding protein glycosylation isomer (M2BPGi) levels, but did not correlate with the histological grade of liver fibrosis. Steroid treatment of AIH patients significantly reduced serum sTIM-3 levels (2147±623pg/ml versus 1321±378pg/ml, p<0.001).

Conclusions

Circulating sTIM-3 levels were elevated in AIH patients and are associated with AIH disease activity and AIH-related liver damage. These findings indicate that serum sTIM-3 correlated with disease status of AIH and could be useful biomarkers to detect autoimmune-mediated liver injury. Our data suggest a possible link between the TIM-3/GAL-9 pathway and AIH severity or phenotype, and further investigations of the TIM-3 pathway and AIH pathophysiology is warranted.

An atlas of immune cell exhaustion in HIV-infected individuals revealed by single-cell transcriptomics

Chronic infection with human immunodeficiency virus (HIV) can cause progressive loss of immune cell function, or exhaustion, which impairs control of virus replication. However, little is known about the development and maintenance, as well as heterogeneity of immune cell exhaustion. Here, we investigated the effects of HIV infection on immune cell exhaustion at the transcriptomic level by analyzing single-cell RNA sequencing of peripheral blood mononuclear cells from four healthy subjects (37,847 cells) and six HIV-infected donors (28,610 cells). We identified nine immune cell clusters and eight T cell subclusters, and three of these (exhausted CD4+ and CD8+ T cells and interferon-responsive CD8+ T cells) were detected only in samples from HIV-infected donors. An inhibitory receptor KLRG1 was identified in a HIV-1 specific exhausted CD8+ T cell population expressing KLRG1, TIGIT, and T-betdimEomeshi markers. Ex-vivo antibody blockade of KLRG1 restored the function of HIV-specific exhausted CD8+ T cells demonstrating the contribution of KLRG1+ population to T cell exhaustion and providing an immunotherapy target to treat HIV chronic infection. These data provide a comprehensive analysis of gene signatures associated with immune cell exhaustion during HIV infection, which could be useful in understanding exhaustion mechanisms and developing new cure therapies.

Tim-3 Promotes Listeria monocytogenes Immune Evasion by Suppressing Major Histocompatibility Complex Class I

BACKGROUND

T-cell immunoglobulin and mucin protein 3 (Tim-3) is an immune checkpoint inhibitor that has therapeutic implications for many tumors and infectious diseases. However, the mechanisms by which Tim-3 promotes immune evasion remain unclear.

METHODS

In this study, we demonstrated that Tim-3 inhibits the expression of major histocompatibility complex class I (MHC-I) in macrophages at both the messenger ribonucleic acid and protein levels by inhibiting the STAT1-NLRC5 signaling pathway.

RESULTS

As a result, MHC-I-restricted antigen presentation by macrophages was inhibited by Tim-3 both in vitro and in a Listeria monocytogenes infection model in vivo. Systemic overexpression of Tim-3 or specific knockout of Tim-3 in macrophages significantly attenuated or enhanced CD8+ T-cell activation and infection damage in L monocytogenes-infected mice, respectively.

CONCLUSIONS

Thus, we identified a new mechanism by which Tim-3 promotes L monocytogenes immune evasion. Further studies on this pathway might shed new light on the physio-pathological roles of Tim-3 and suggest new approaches for intervention.

Targeting TIM-3 in solid tumors: innovations in the preclinical and translational realm and therapeutic potential

INTRODUCTION

Immune checkpoint inhibitors (ICIs) have shown a great therapeutic efficacy in cancer patients. However, a significant proportion of cancer patients remain unresponsive or show limited response. T cell immunoglobulin and mucin-domain containing protein-3 (TIM-3) is a co-inhibitory receptor expressed on various cell types and is involved in the attenuation of immune responses. TIM-3 and its ligands are highly expressed in various solid malignancies and some studies have reported its association with worse disease outcomes. Thus, targeting TIM-3 could be a promising therapeutic approach to treat cancer patients.

AREAS COVERED

This review describes the role of TIM-3 and its ligands in regulating anti-tumor immunity and their contribution to cancer progression. Moreover, this review focuses on the preclinical models and translational data from important studies published in PubMed till October 2020, which demonstrate the therapeutic benefits of targeting TIM-3 signaling.

EXPERT OPINION

Despite the promising data obtained from targeting TIM-3 in preclinical models, precise mechanisms underlying the anti-tumor effects of TIM-3 inhibition are not fully elucidated. Therefore, mechanistic studies are required to provide better insights into the anti-tumor effects of targeting TIM-3, and clinical data are necessary to determine the safety profiles and therapeutic efficacy of TIM-3 inhibition in cancer patients.

T cell immunoglobulin and mucin domain-3 is associated with disease activity and progressive joint damage in rheumatoid arthritis patients

T cell immunoglobulin and mucin domain-3 (TIM-3) is a surface molecule expressed on immune cells which play a role in immune regulation. The aims of the present study were to determine whether circulating soluble T cell immunoglobulin domain and mucin-3 (sTIM-3) are elevated in rheumatoid arthritis (RA) patients, and investigate the relationships between sTIM-3 and clinical features of RA.The study included 116 patients with established RA and 27 healthy control subjects. Serum levels of sTIM-3 were measured via the enzyme-linked immunosorbent assays (ELISA). Correlations between serum sTIM-3 and a range of parameters including anti-citrullinated peptide antibody (ACPA) titer, erythrocyte sedimentation rate (ESR), and matrix metalloproteinase-3 (MMP-3) were assessed.Serum sTIM-3 was significantly elevated in RA patients compared with those in healthy subjects, and it was positively correlated with ACPA titer (r = 0.27 P = .005), ESR (r = 0.27, P = .004) and MMP-3 (r = 0.35, P < .001). In RA patients with high ACPA titers (≥200 U/mL), sTIM-3 was not correlated with ESR or MMP-3. Whereas, sTIM-3 was significantly correlated with ESR and MMP-3 in RA patients with low ACPA titers (<200 U/mL).Serum sTIM-3 was increased in RA patients, and it was associated with proinflammatory markers and disease activity in RA patients under a particular ACPA status. Our data suggest that circulating sTIM-3 may be a useful biomarker for the determination of disease activity in RA patients.

Significance of TIM-3 expression by CD4+ and CD8+ T lymphocytes in tumor-draining lymph nodes from patients with breast cancer

T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), which is expressed by immune and nonimmune cells, has been shown to play immunoregulatory roles in the tumor microenvironment. In this study we assessed the expression of TIM-3 by T cells from tumor draining lymph nodes (TDLNs) of patients with breast cancer and its association with disease progression. Lymphocytes were isolated from 41 TDLNs, and flow cytometry was used to determine the expression of TIM-3 on CD4⁺ and CD8⁺ T cells, along with the simultaneous expression of CD25, Foxp3 and TIM-3 in CD4⁺ T cells. The results showed that the frequency of TIM-3⁺CD8⁺ T cells was associated with higher tumor grade, and the geometric mean fluorescence intensity (gMFI) of TIM-3 in CD4⁺ and CD8⁺ T cells was significantly higher in patients with more than 9 involved lymph nodes than those with fewer involved nodes. The gMFI of TIM3 in CD4⁺ T cells also showed a direct correlation with the number of metastatic lymph nodes. Phenotypic characterization of TIM-3⁺CD4⁺ T cells showed that the majority of CD4⁺TIM3⁺ lymphocytes were Foxp3 ^̶ CD25 ^̶, and the majority of Foxp3⁺CD25⁺ regulatory T cells were TIM-3^-. Our findings showed that TIM-3 was expressed by CD4⁺, CD8⁺ and regulatory T cells in breast TDLNs, and that expression on CD4⁺ and CD8⁺ T cells was mostly associated with poor prognosticators such as a higher number of involved lymph nodes or higher tumor grade. More studies are required to confirm TIM-3 as a prognostic marker and a target for immunotherapy in breast cancer.

Decrease of T-cells exhaustion markers programmed cell death-1 and T-cell immunoglobulin and mucin domain-containing protein 3 and plasma IL-10 levels after successful treatment of chronic hepatitis C

During chronic hepatitis C virus (HCV) infection, both CD4+ and CD8+ T-cells become functionally exhausted, which is reflected by increased expression of programmed cell death-1 (PD-1) and T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3), and elevated anti-inflammatory interleukin 10 (IL-10) plasma levels. We studied 76 DAA-treated HCV-positive patients and 18 non-infected controls. Flow cytometry measured pretreatment frequencies of CD4+PD-1+, CD4+PD-1+Tim-3+ and CD8+PD-1+Tim-3+ T-cells and IL-10 levels measured by ELISA were significantly higher and CD4+PD-1-Tim-3- and CD8+PD-1-Tim-3- T-cells were significantly lower in patients than in controls. Treatment resulted in significant decrease of CD4+Tim-3+, CD8+Tim-3+, CD4+PD-1+Tim-3+ and CD8+PD-1+Tim-3+ T-cell frequencies as well as IL-10 levels and increase in CD4+PD-1-Tim-3- and CD8+PD-1-Tim-3- T-cells. There were no significant changes in the frequencies of CD4+PD-1+ T-cells, while CD8+PD-1+ T-cells increased. Patients with advanced liver fibrosis had higher PD-1 and lower Tim-3 expression on CD4+T-cells and treatment had little or no effect on the exhaustion markers. HCV-specific CD8+T-cells frequency has declined significantly after treatment, but their PD-1 and Tim-3 expression did not change. Successful treatment of chronic hepatitis C with DAA is associated with reversal of immune exhaustion phenotype, but this effect is absent in patients with advanced liver fibrosis.

Immunological approaches to HIV cure

Combination antiretroviral therapy (ART) to treat human immunodeficiency virus (HIV) infection has proven remarkably successful - for those who can access and afford it - yet HIV infection persists indefinitely in a reservoir of cells, despite effective ART and despite host antiviral immune responses. An HIV cure is therefore the next aspirational goal and challenge, though approaches differ in their objectives - with 'functional cures' aiming for durable viral control in the absence of ART, and 'sterilizing cures' aiming for the more difficult to realize objective of complete viral eradication. Mechanisms of HIV persistence, including viral latency, anatomical sequestration, suboptimal immune functioning, reservoir replenishment, target cell-intrinsic immune resistance, and, potentially, target cell distraction of immune effectors, likely need to be overcome in order to achieve a cure. A small fraction of people living with HIV (PLWH) naturally control infection via immune-mediated mechanisms, however, providing both sound rationale and optimism that an immunological approach to cure is possible. Herein we review up to date knowledge and emerging evidence on: the mechanisms contributing to HIV persistence, as well as potential strategies to overcome these barriers; promising immunological approaches to achieve viral control and elimination of reservoir-harboring cells, including harnessing adaptive immune responses to HIV and engineered therapies, as well as enhancers of their functions and of complementary innate immune functioning; and combination strategies that are most likely to succeed. Ultimately, a cure must be safe, effective, durable, and, eventually, scalable in order to be widely acceptable and available.

Persistent lentivirus infection induces early myeloid suppressor cells expansion to subvert protective memory CD8 T cell response✰,✰✰

Background

Memory CD8⁺T cell responses play an essential role in protection against persistent infection. However, HIV-1 evades vaccine-induced memory CD8⁺T cell response by mechanisms that are not fully understood.

Methods

We analyzed the temporal dynamics of CD8⁺T cell recall activity and function during EcoHIV infection in a potent PD1-based vaccine immunized immunocompetent mice.

Findings

Upon intraperitoneal EcoHIV infection, high levels of HIV-1 GAG-specific CD8⁺T lymphocytes recall response reduced EcoHIV-infected cells significantly. However, this protective effect diminished quickly after seven days, followed by a rapid reduction of GAG-specific CD8⁺T cell number and activity, and viral persistence. Mechanistically, EcoHIV activated dendritic cells (DCs) and myeloid cells. Myeloid cells were infected and rapidly expanded, exhibiting elevated PD-L1/-L2 expression and T cell suppressive function before day 7, and were resistant to CD8⁺T cell-mediated apoptosis. Depletion of myeloid-derived suppressor cells (MDSCs) reduced EcoHIV infection and boosted T cell responses.

Interpretation

This study provides an overview of the temporal interplay of persistent virus, DCs, MDSCs and antigen-specific CD8⁺T cells during acute infection. We identify MDSCs as critical gatekeepers that restrain antiviral T cell memory responses, and highlight MDSCs as an important target for developing effective vaccines against chronic human infections.

Funding

Hong Kong Research Grant Council (T11–709/18-N, HKU5/CRF/13G), General Research Fund (17122915 and 17114114), Hong Kong Health and Medical Research Fund (11100752, 14130582, 16150662), Grant RGC-ANR A-HKU709/14, the San-Ming Project of Medicine (SZSM201512029), University Development Fund of the University of Hong Kong and Li Ka Shing Faculty of Medicine Matching Fund to HKU AIDS Institute.

Immune Checkpoints in Viral Infections

As evidence has mounted that virus-infected cells, such as cancer cells, negatively regulate the function of T-cells via immune checkpoints, it has become increasingly clear that viral infections similarly exploit immune checkpoints as an immune system escape mechanism. Although immune checkpoint therapy has been successfully used in cancer treatment, numerous studies have suggested that such therapy may also be highly relevant for treating viral infection, especially chronic viral infections. However, it has not yet been applied in this manner. Here, we reviewed recent findings regarding immune checkpoints in viral infections, including COVID-19, and discussed the role of immune checkpoints in different viral infections, as well as the potential for applying immune checkpoint blockades as antiviral therapy.

Hydrogen gas activates coenzyme Q10 to restore exhausted CD8+ T cells, especially PD-1+Tim3+terminal CD8+ T cells, leading to better nivolumab outcomes in patients with lung cancer

As previously reported, hydrogen gas improves the prognosis of patients with cancer by restoring exhausted CD8⁺ T cells into active CD8⁺ T cells, possibly by activating mitochondria. As mitochondrial activators exhibit synergistic effects with nivolumab, the current study investigated whether hydrogen gas also affects the clinical outcomes of nivolumab. A total of 42 of 56 patients with lung cancer treated with nivolumab received hydrogen gas. Exhausted markers (PD-1 and Tim-3) on cell populations in the CD8⁺ T cell differentiation pathway were analyzed using flow cytometry. The concentration of coenzyme Q10 (CoQ10) was measured as a marker of mitochondrial function. The 42 patients treated with hydrogen gas and nivolumab (HGN) indicated a significantly longer overall survival (OS) compared with those treated with nivolumab only (n=14). In multivariate analysis, PD-1⁺Tim-3⁺terminal CD8⁺ T cells (PDT+) were an independent poor prognostic factor in OS, and CoQ10 showed a tendency to be associated with improved OS. The change in the rate of PDT+ and CoQ10 after vs. before HGN (PDT+ ratio and CoQ10 ratio, respectively) revealed that patients with low PDT+ ratio (<0.81) and high CoQ10 ratio (>1.175) had significantly longer OS compared with those with high PDT+ ratio and low CoQ10 ratio. Furthermore, PDT+, with a significant reverse correlation with CoQ10, was significantly lower in patients with high CoQ10 and/or CoQ10 ratio than in those low CoQ10 and/or CoQ10. Hydrogen gas has been suggested to enhance the clinical efficacy of nivolumab by increasing CoQ10 (mitochondria) to reduce PDT+, with PDT+ and CoQ10 as reliable negative and positive biomarkers of nivolumab, respectively.

Checkpoint inhibitor immunotherapy for glioblastoma: current progress, challenges and future outlook

INTRODUCTION

Despite maximal surgical resection and chemoradiation, glioblastoma (GBM) continues to be associated with significant morbidity and mortality. Novel therapeutic strategies are urgently needed. Given success in treating multiple other forms of cancer, checkpoint inhibitor immunotherapy remains foremost amongst novel therapeutic strategies that are currently under investigation.

AREAS COVERED

Through a systematic review of both published literature and the latest preliminary data available from ongoing clinical studies, we provide an up-to-date discussion on the immune system in the CNS, a detailed mechanistic evaluation of checkpoint biology in the CNS along with evidence for disruption of these pathways in GBM, and a summary of available preclinical and clinical data for checkpoint blockade in GBM. We also include a discussion of novel, emerging targets for checkpoint blockade which may play an important role in GBM immunotherapy.

EXPERT OPINION

Evidence indicates that while clinical success of checkpoint blockade for the treatment of GBM has been limited to date, through improved preclinical models, optimization in the context of standard of care therapies, assay standardization and harmonization, and combinatorial approaches which may include novel targets for checkpoint blockade, checkpoint inhibitor immunotherapy may yield a safe and effective therapeutic option for the treatment of GBM.

CD160 Plays a Protective Role During Chronic Infection by Enhancing Both Functionalities and Proliferative Capacity of CD8+ T Cells

The understanding of protective immunity during HIV infection remains elusive. Here we showed that CD160 defines a polyfunctional and proliferative CD8+ T cell subset with a protective role during chronic HIV-1 infection. CD160+ CD8+ T cells derived from HIV+ patients correlated with slow progressions both in a cross-sectional study and in a 60-month longitudinal cohort, displaying enhanced cytotoxicity and proliferative capacity in response to HIV Gag stimulation; triggering CD160 promoted their functionalities through MEK–ERK and PI3K–AKT pathways. These observations were corroborated by studying chronic lymphocytic choriomeningitis virus (LCMV) infection in mice. The genetic ablation of CD160 severely impaired LCMV-specific CD8+ T cell functionalities and thereby resulted in loss of virus control. Interestingly, transcriptional profiling showed multiple costimulatory and survival pathways likely to be involved in CD160+ T cell development. Our data demonstrated that CD160 acts as a costimulatory molecule positively regulating CD8+ T cells during chronic viral infections, thus representing a potential target for immune intervention.

Small molecules as antagonists of co-inhibitory pathways for cancer immunotherapy: a patent review (2018-2019)

INTRODUCTION

Therapeutic antibodies blocking co-inhibitory pathways do not attack tumor cells directly, but instead bind to their targeted proteins and mobilize the immune system to eradicate tumors. However, only a small fraction of patients with certain cancer types can benefit from the antibodies. Additionally, antibodies have shown serious immune-related adverse events in certain patients. Small-molecule antagonists may be a complementary and potentially synergistic approach to antibodies for patients with various cancers.

AREAS COVERED

The authors review the small molecules as antagonists of co-inhibitory pathway proteins, summarize their preliminary SARs, discuss biochemistry assays used in patents for the development of small molecules as novel antagonists.

EXPERT OPINION

The disclosed pharmacophores of small molecules as co-inhibitory pathway antagonists are represented by biphenyl derivatives, biaryl derivatives, teraryl derivatives, quateraryl derivatives, and oxadiazole/thiadiazole derivatives. However, these antagonists are still inferior to therapeutic antibodies in their inhibitory activities due to relatively flat of human co-inhibitory pathways proteins. Allosteric modulators may be an alternative approach. The more safety and efficacy evaluation trials of small-molecule antagonists targeting co-inhibitory pathways should be performed to demonstrate the proof-of-principle that small-molecule antagonists can result in sustained safety and antitumor response in the near future.

Engineered Antigen-Specific T Cells Secreting Broadly Neutralizing Antibodies: Combining Innate and Adaptive Immune Response against HIV

While antiretroviral therapy (ART) can completely suppress viremia, it is not a cure for HIV. HIV persists as a latent reservoir of infected cells, able to evade host immunity and re-seed infection following cessation of ART. Two promising immunotherapeutic strategies to eliminate both productively infected cells and reactivated cells of the reservoir are the adoptive transfer of potent HIV-specific T cells and the passive administration of HIV-specific broadly neutralizing antibodies also capable of mediating antibody-dependent cellular cytotoxicity (ADCC). The simultaneous use of both as the basis of a single therapeutic has never been explored. We therefore sought to modify HIV-specific T cells from HIV-naive donors (to allow their use in the context of allotransplant, a promising platform for sterilizing cures) so they are able to secrete a broadly neutralizing antibody (bNAb) directed against the HIV envelope to elicit ADCC. We designed an antibody construct comprising bNAb 10-1074 heavy and light chains, fused to IgG3 Fc to elicit ADCC, with truncated cluster of differentiation 19 (CD19) as a selectable marker. HIV-specific T cells were expanded from HIV-naive donors by priming with antigen-presenting cells expressing overlapping HIV antigens in the presence of cytokines. T cells retained specificity against Gag, Nef, and Pol peptides (218.55 ± 300.14 interferon γ [IFNγ] spot-forming cells [SFC]/1 × 10⁵) following transduction (38.92 ± 25.30) with the 10-1074 antibody constructs. These cells secreted 10-1074 antibodies (139.04 ± 114.42 ng/mL). The HIV-specific T cells maintained T cell function following transduction, and the secreted 10-1074 antibody bound HIV envelope (28.13% ± 19.42%) and displayed ADCC activity (10.47% ± 4.11%). Most critically, the 10-1074 antibody-secreting HIV-specific T cells displayed superior in vitro suppression of HIV replication. In summary, HIV-specific T cells can be engineered to produce antibodies mediating ADCC against HIV envelope-expressing cells. This combined innate/adaptive approach allows for synergy between the two immune arms, broadens the target range of the immune therapy, and provides further insight into what defines an effective anti-HIV response.

Mechanisms of T-Cell Exhaustion in Pancreatic Cancer

T-cell exhaustion is a phenomenon that represents the dysfunctional state of T cells in chronic infections and cancer and is closely associated with poor prognosis in many cancers. The endogenous T-cell immunity and genetically edited cell therapies (CAR-T) failed to prevent tumor immune evasion. The effector T-cell activity is perturbed by an imbalance between inhibitory and stimulatory signals causing a reprogramming in metabolism and the high levels of multiple inhibitory receptors like programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), and Lymphocyte-activation gene 3 (Lag-3). Despite the efforts to neutralize inhibitory receptors by a single agent or combinatorial immune checkpoint inhibitors to boost effector function, PDAC remains unresponsive to these therapies, suggesting that multiple molecular mechanisms play a role in stimulating the exhaustion state of tumor-infiltrating T cells. Recent studies utilizing transcriptomics, mass cytometry, and epigenomics revealed a critical role of Thymocyte selection-associated high mobility group box protein (TOX) genes and TOX-associated pathways, driving T-cell exhaustion in chronic infection and cancer. Here, we will review recently defined molecular, genetic, and cellular factors that drive T-cell exhaustion in PDAC. We will also discuss the effects of available immune checkpoint inhibitors and the latest clinical trials targeting various molecular factors mediating T-cell exhaustion in PDAC.

The Potential of Immune Modulation in Therapeutic HIV-1 Vaccination

We discuss here some of the key immunological elements that are at the crossroads and need to be combined to develop a potent therapeutic HIV-1 vaccine. Therapeutic vaccines have been commonly used to enhance and/or recall pre-existing HIV-1-specific cell-mediated immune responses aiming to suppress virus replication. The current success of immune checkpoint blockers in cancer therapy renders them very attractive to use in HIV-1 infected individuals with the objective to preserve the function of HIV-1-specific T cells from exhaustion and presumably target the persistent cellular reservoir. The major latest advances in our understanding of the mechanisms responsible for virus reactivation during therapy-suppressed individuals provide the scientific basis for future combinatorial therapeutic vaccine development.

TOX is expressed by exhausted and polyfunctional human effector memory CD8+ T cells

CD8⁺ T cell exhaustion is a hallmark of many cancers and chronic infections. In mice, T cell factor 1 (TCF-1) maintains exhausted CD8⁺ T cell responses, whereas thymocyte selection-associated HMG box (TOX) is required for the epigenetic remodeling and survival of exhausted CD8⁺ T cells. However, it has remained unclear to what extent these transcription factors play analogous roles in humans. In this study, we mapped the expression of TOX and TCF-1 as a function of differentiation and specificity in the human CD8⁺ T cell landscape. Here, we demonstrate that circulating TOX⁺ CD8⁺ T cells exist in most humans, but that TOX is not exclusively associated with exhaustion. Effector memory CD8⁺ T cells generally expressed TOX, whereas naive and early-differentiated memory CD8⁺ T cells generally expressed TCF-1. Cytolytic gene and protein expression signatures were also defined by the expression of TOX. In the context of a relentless immune challenge, exhausted HIV-specific CD8⁺ T cells commonly expressed TOX, often in clusters with various activation markers and inhibitory receptors, and expressed less TCF-1. However, polyfunctional memory CD8⁺ T cells specific for cytomegalovirus (CMV) or Epstein-Barr virus (EBV) also expressed TOX, either with or without TCF-1. A similar phenotype was observed among HIV-specific CD8⁺ T cells from individuals who maintained exceptional immune control of viral replication. Collectively, these data demonstrate that TOX is expressed by most circulating effector memory CD8⁺ T cell subsets and not exclusively linked to exhaustion.

The Role of Immunomodulatory Receptors in the Pathogenesis of HIV Infection: A Therapeutic Opportunity for HIV Cure?

Immune activation is the hallmark of HIV infection and plays a role in the pathogenesis of the disease. In the context of suppressed HIV RNA replication by combination antiretroviral therapy (cART), there remains immune activation which is associated to the HIV reservoirs. Persistent virus contributes to a sustained inflammatory environment promoting accumulation of "activated/exhausted" T cells with diminished effector function. These T cells show increased expression of immunomodulatory receptors including Programmed cell death protein (PD1), Cytotoxic T Lymphocyte Associated Protein 4 (CTLA4), Lymphocyte activation gene 3 (LAG3), T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin domain containing 3 (TIM3) among others. More importantly, recent reports had demonstrated that, HIV infected T cells express checkpoint receptors, contributing to their survival and promoting maintenance of the viral reservoir. Therapeutic strategies are focused on viral reservoir elimination and/or those to achieve sustained cART-free virologic remission. In this review, we will discuss the immunological basis and the latest advances of the use of checkpoint inhibitors to treat HIV infection.

Human cancer germline antigen-specific cytotoxic T cell-what can we learn from patient

In this review, we will highlight the importance of cancer germline antigen-specific cytotoxic CD8+ T lymphocytes (CTL) and the factors affecting antitumor CTL responses. In light of cancer immunotherapy, we will emphasis the need to further understand the features, characteristics, and actions of modulatory receptors of human cancer germline-specific CTLs, in order to determine the optimal conditions for antitumor CTL responses.

Blockade of PD-1, PD-L1, and TIM-3 Altered Distinct Immune- and Cancer-Related Signaling Pathways in the Transcriptome of Human Breast Cancer Explants

Immune checkpoint inhibitors (ICIs) are yet to have a major advantage over conventional therapies, as only a fraction of patients benefit from the currently approved ICIs and their response rates remain low. We investigated the effects of different ICIs—anti-programmed cell death protein 1 (PD-1), anti-programmed death ligand-1 (PD-L1), and anti-T cell immunoglobulin and mucin-domain containing-3 (TIM-3)—on human primary breast cancer explant cultures using RNA-Seq. Transcriptomic data revealed that PD-1, PD-L1, and TIM-3 blockade follow unique mechanisms by upregulating or downregulating distinct pathways, but they collectively enhance immune responses and suppress cancer-related pathways to exert anti-tumorigenic effects. We also found that these ICIs upregulated the expression of other IC genes, suggesting that blocking one IC can upregulate alternative ICs, potentially giving rise to compensatory mechanisms by which tumor cells evade anti-tumor immunity. Overall, the transcriptomic data revealed some unique mechanisms of the action of monoclonal antibodies (mAbs) targeting PD-1, PD-L1, and TIM-3 in human breast cancer explants. However, further investigations and functional studies are warranted to validate these findings.

Interleukin 15 upregulates the expression of PD-1 and TIM-3 on CD4+ and CD8+ T cells

Virus-specific T cell-mediated immunity is severely impaired in chronic hepatitis B virus (HBV) patients. HBV-specific T cells in chronic HBV patients show a low ability to produce cytokines and to exert their cytotoxic activity. A prominent characteristic of these exhausted T cells is overexpression of inhibitory receptor molecules which negatively regulate T cell function. In this study, we examined in vitro regulation of two inhibitory receptor expressions, programmed death 1 (PD-1) and T cell immunoglobulin mucin domain-containing molecule 3 (TIM-3). Peripheral blood mononuclear cells (PBMCs) obtained from healthy individuals were in vitro stimulated with a panel of cytokines. PD-1 and TIM-3 expression levels on CD4⁺ and CD8⁺ T cells were examined at days 2 and 7 post stimulation. We demonstrated that PD-1 and TIM-3 were induced via polyclonal (anti-CD3) and cytokine (interleukin 15 [IL-15]) stimulations. Noteworthy, there was a significantly increased induction of TIM-3 on CD8⁺ T cells as compared to CD4⁺ T cells. Our study thus contributes to further understanding the regulation of T cell exhaustion markers PD-1 and TIM-3.

Role of TH17 Responses in Increasing Herpetic Keratitis in the Eyes of Mice Infected with HSV-1

Purpose

T_H17 cells play an important role in host defense and autoimmunity yet very little is known about the role of IL17 in herpes simplex virus (HSV)-1 infectivity. To better understand the relationship between IL17 and HSV-1 infection, we assessed the relative impact of IL17A-deficiency and deficiency of its receptors on HSV-1 responses in vivo.

Methods

We generated IL17RA^−/− and IL17RA^−/−RC^−/− mice in-house and infected them along with IL17A^−/− and IL17RC^−/− mice in the eyes with 2 × 10⁵ PFU/eye of wild type (WT) HSV-1 strain McKrae. WT C57BL/6 mice were used as control. Virus replication in the eye, survival, corneal scarring (CS), angiogenesis, levels of latency-reactivation, and levels of CD8 and exhaustion markers (PD1, TIM3, LAG3, CTLA4, CD244, and CD39) in the trigeminal ganglia (TG) of infected mice were determined on day 28 postinfection.

Results

No significant differences in virus replication in the eye, survival, latency, reactivation, and exhaustion markers were detected among IL17A^−/−, IL17RA^−/−, IL17RC^−/−, IL17RA^−/−RC^−/−, and WT mice. However, mice lacking IL17 had significantly less CS and angiogenesis than WT mice. In addition, angiogenesis levels in the absence of IL17RC and irrespective of the absence of IL17RA were significantly less than in IL17A- or IL17RA-deficient mice.

Conclusions

Our results suggest that the absence of IL17 protects against HSV-1-induced eye disease, but has no role in protecting against virus replication, latency, or reactivation. In addition, our data provide rationale for blocking IL17RC function rather than IL17A or IL17RA function as a key driver of HSV-1-induced eye disease.

Programmed cell death protein 1 (PD-1) in infection

Exhausted and dysfunctional T cells triggered by infection and cancer render the immune system unable to eliminate these pathogens. Pharmacologic blockade of the surface receptors that inhibit T-cell function has shown remarkable success in patients with various malignancies. In this Review, we discuss the emerging evidence of inhibiting checkpoint pathways as a potential role in controlling or clearing infectious diseases. Though interesting tendencies, much work is still needed in order to develop safe strategies that can be translated into clinically relevant outcomes in patients with infections.

A therapeutic HIV-1 vaccine reduces markers of systemic immune activation and latent infection in patients under highly active antiretroviral therapy

HIV infection is characterized by chronic immune activation and the establishment of a pool of latently infected cells. Antiretroviral therapy (ART) can suppress viral load to undetectable levels in peripheral blood by standard measure, however immune activation/chronic inflammation and latent infection persist and affect quality of life. We have now shown that a novel therapeutic HIV vaccine consisting of replication-defective HIV (HIVAX), given in the context of viral suppression under ART, can reduce both immune activation/chronic inflammation and latent infection. Immune activation, as measured by percent of CD8 + HLA-DR + CD38 + T cells, approached levels of healthy controls at week 16 following vaccination. Reduced immune activation was accompanied by a reduction in pro-inflammatory cytokines and peripheral α4β7 + plasmacytoid DC (a marker of mucosal immune activation). Levels of both HIV-1 DNA and 2-LTR circles were reduced at week 16 following vaccination, suggesting HIVAX can impact HIV-1 latency and reduce viral replication. Surprisingly, reduced immune activation/chronic inflammation was accompanied by an increase in the percent of memory CD4 + T cells expressing markers PD-1 and TIM-3. In addition, evaluation of HIV-1 Gag-specific CD4 + T cells for expression of 96 T cell related genes pre- and post-therapy revealed increased expression of a number of genes involved in the regulation of immune activation, T cell activation, and antiviral responses. Overall this study provides evidence that vaccination with HIVAX in subjects under long term antiviral suppression can reduce immune activation/chronic inflammation and latent infection (Clinicaltrials.gov, identifier NCT01428596).

T-cell exhaustion in HIV infection

The T‐cell response is central in the adaptive immune‐mediated elimination of pathogen‐infected and/or cancer cells. This activated T‐cell response can inflict an overwhelming degree of damage to the targeted cells, which in most instances leads to the control and elimination of foreign invaders. However, in conditions of chronic infection, persistent exposure of T cells to high levels of antigen results in a severe T‐cell dysfunctional state called exhaustion. T‐cell exhaustion leads to a suboptimal immune‐mediated control of multiple viral infections including the human immunodeficiency virus (HIV). In this review, we will discuss the role of T‐cell exhaustion in HIV disease progression, the long‐term defect of T‐cell function even in aviremic patients on antiretroviral therapy (ART), the role of exhaustion‐specific markers in maintaining a reservoir of latently infected cells, and exploiting these markers in HIV cure strategies.

BCL-2 antagonism sensitizes cytotoxic T cell-resistant HIV reservoirs to elimination ex vivo

Curing HIV infection will require the elimination of a reservoir of infected CD4+ T cells that persists despite HIV-specific cytotoxic T cell (CTL) responses. Although viral latency is a critical factor in this persistence, recent evidence also suggests a role for intrinsic resistance of reservoir-harboring cells to CTL killing. This resistance may have contributed to negative outcomes of clinical trials, where pharmacologic latency reversal has thus far failed to drive reductions in HIV reservoirs. Through transcriptional profiling, we herein identified overexpression of the prosurvival factor B cell lymphoma 2 (BCL-2) as a distinguishing feature of CD4+ T cells that survived CTL killing. We show that the inducible HIV reservoir was disproportionately present in BCL-2hi subsets in ex vivo CD4+ T cells. Treatment with the BCL-2 antagonist ABT-199 was not sufficient to drive reductions in ex vivo viral reservoirs when tested either alone or with a latency-reversing agent (LRA). However, the triple combination of strong LRAs, HIV-specific T cells, and a BCL-2 antagonist uniquely enabled the depletion of ex vivo viral reservoirs. Our results provide rationale for novel therapeutic approaches targeting HIV cure and, more generally, suggest consideration of BCL-2 antagonism as a means of enhancing CTL immunotherapy in other settings, such as cancer.

TIM-3 and CEACAM1 do not interact in cis and in trans

TIM‐3 has been considered as a target in cancer immunotherapy. In T cells, inhibitory as well as activating functions have been ascribed to this molecule. Its role may therefore depend on the state of T cells and on the presence of interaction partners capable to perform functional pairing. Carcinoembryonic antigen‐related cell adhesion molecule (CEACAM1) has been proposed to bind TIM‐3 and to regulate its function. Using a T cell reporter platform we confirmed CEACAM1‐mediated inhibition, but CEACAM1 did not functionally engage TIM‐3. TIM‐3 and CEACAM1 coexpression was limited to a small subset of activated T cells. Moreover, results obtained in extensive binding studies were not in support of an interaction between TIM‐3 and CEACAM1. Cytoplasmic sequences derived from TIM‐3 induced inhibitory signaling in our human T cell reporter system.

Our results indicate that TIM‐3 functions are independent of CEACAM1 and that this receptor has the capability to promote inhibitory signaling pathways in human T cells.

Tim-3: A co-receptor with diverse roles in T cell exhaustion and tolerance

T cell inhibitory co-receptors play a crucial role in maintaining the balance between physiologic immune responses and maladaptive ones. T cell immunoglobulin and mucin domain-containing-3 (Tim-3) is a unique inhibitory co-receptor in that its expression is chiefly restricted to interferon (IFN)γ-producing CD4⁺ and CD8⁺ T cells. Early reports firmly established its importance in maintaining peripheral tolerance in transplantation and autoimmunity. However, it has become increasingly clear that Tim-3 expression on T cells, together with other check-point molecules, in chronic infections and cancers can hinder productive immune responses. In this review, we outline what is currently known about the regulation of Tim-3 expression, its ligands and signaling. We discuss both its salutary and deleterious function in immune disorders, as well as the T cell-extrinsic and -intrinsic factors that regulate its function.

Insights into CD8 T Cell Activation and Exhaustion from a Mouse Gammaherpesvirus Model

(S.R.S.) I was introduced to viral immunology while working in Peter Doherty's laboratory in the early stages of my research career, inspiring a lifelong interest in this area. During those early years under Peter's mentorship, we studied a mouse gammaherpesvirus model (murine gammaherpesvirus-68 [MHV-68]) that provided a useful small animal model for investigating the immunological control of gammaherpesvirus infection. Interestingly, while CD4 T cells were not required for acute control of MHV-68 in the lung, CD8 T cell-mediated control was progressively lost in the absence of CD4 T cell help, leading to viral recrudescence. This was one of several early studies showing that CD8 T cell control of persistent viral infections was lost in the absence of CD4 T cell help, preceding the concept of CD8 T cell exhaustion. Further studies showed that MHV-68 infection of mice offered a unique model for comparing the mechanisms of acute and long-term control of a persistent viral infection and developing strategies for reversing T cell exhaustion. Here, we provide a brief review of the literature on CD8 T cell activation and exhaustion in this model, focusing on the role of CD40 and B7 family members and including some previously unpublished data.