Co-expression Of Programmed Death 1 Research Articles

A Novel Epigenetic Strategy to Concurrently Block Immune Checkpoints PD-1/PD-L1 and CD155/TIGIT in Hepatocellular Carcinoma

Tumor microenvironment is an intricate web of stromal and immune cells creating an immune suppressive cordon around the tumor. In hepatocellular carcinoma (HCC), Tumor microenvironment is a formidable barrier towards novel immune therapeutic approaches recently evading the oncology field. In this study, the main aim was to identify the intricate immune evasion tactics mediated by HCC cells and to study the epigenetic modulation of the immune checkpoints; Programmed death-1 (PD-1)/ Programmed death-Ligand 1 (PD-L1) and T cell immunoreceptor with Ig and ITIM domains (TIGIT)/Cluster of Differentiation 155 (CD155) at the tumor-immune synapse. Thus, liver tissues, PBMCs and sera were collected from Hepatitis C Virus (HCV), HCC as well as healthy individuals. Screening was performed to PD-L1/PD-1 and CD155/TIGIT axes in HCC patients. PDL1, CD155, PD-1 and TIGIT were found to be significantly upregulated in liver tissues and peripheral blood mononuclear cells (PBMCs) of HCC patients. An array of long non-coding RNAs (lncRNAs) and microRNAs validated to regulate such immune checkpoints were screened. The lncRNAs; CCAT-1, H19, and MALAT-1 were all significantly upregulated in the sera, PBMCs, and tissues of HCC patients as compared to HCV patients and healthy controls. However, miR-944–5p, miR-105–5p, miR-486–5p, miR-506–5p, and miR-30a-5p were downregulated in the sera and liver tissues of HCC patients. On the tumor cell side, knocking down of lncRNAs—CCAT-1, MALAT-1, or H19—markedly repressed the co-expression of PD-L1 and CD155 and accordingly induced the cytotoxicity of co-cultured primary immune cells. On the immune side, ectopic expression of the under-expressed microRNAs; miR-486–5p, miR-506–5p, and miR-30a-5p significantly decreased the transcript levels of PD-1 in PBMCs with no effect on TIGIT. On the other hand, ectopic expression of miR-944–5p and miR-105–5p in PBMCs dramatically reduced the co-expression of PD-1 and TIGIT. Finally, all studied miRNAs enhanced the cytotoxic effects of PBMCs against Huh7 cells. However, miR-105–5p showed the highest augmentation for PBMCs cytotoxicity against HCC cells. In conclusion, this study highlights a novel co-targeting strategy using miR-105–5p mimics, MALAT-1, CCAT-1 and H19 siRNAs to efficiently hampers the immune checkpoints; PD-L1/PD-1 and CD155/TIGIT immune evasion properties in HCC.

Tumor Microenvironment (TME) Regulation of Programmed Death-1 (PD1) Receptor and Its Ligands PDL1 and PDL2 in Chronic Lymphocytic Leukemia (CLL)

The PD1 pathway is involved in the inactivation of immune effectors and is potentially reactive against neoplastic cells in the TME. T cells from CLL patients exhibit defective immunity, decreased proliferative capacity, and impaired effector function leading to T cell exhaustion. These functional defects coincide with higher CD244, CD160 and PD1 expression on T cells. In the Eμ-TCL1 transgenic CLL model, PDL1 checkpoint blockade restores immune dysfunction and impairs leukemia growth. PD1/PDL1 ligation also affects BCR signaling, and because PD1 is also expressed on CLL cells, PD1 interference might directly influence tumor growth and proliferation directly.We studied the 1) expression the PD1 receptor and its ligands and their correlation with TFTT; 2) role of the TME in controlling PD1 axis and miRNA expression; 3) role of the BCRi ibrutinib (IB) in the expression of the receptor and ligands.Early-stage CLL patients were prospectively enrolled at diagnosis (n=211, O-CLL1: clinicaltrial.govID:NCT00917540). Gene expression (GE) profiling was performed using the GeneChipVR Gene1.0 STArray (Affymetrix) and validated by qPCR (Thermofisher) and flow-cytometry (FC, BD Biosciences) in an independent subset of patients. CLL lymph node samples underwent in situ immunolocalization analyses. Autologous T-cells (AAT) were obtained by in vitro exposure of patient T-cells with anti CD3/CD28 Dynabeads (Thermofisher) and IL2 in co-culture with CLL cells. Cultures were monitored until substantial clumping was observed and tested for PD1 axis expression. HS5 stromal cells were used in co-culture experiments with B-CLL (ratio 1:100). MiR-424 expression was evaluated by qPCR using validated TaqMan® MicroRNA Assays (Thermofisher). In selected experiments IB was added to cell culture. PD1 GEP of circulating B-CLL cells was significantly higher than of ligands. No differences in GEP of PD1 or its ligands were observed stratifying cases based on CD38, ZAP-70, or FISH markers. Significantly higher PDL1 GE was detected in IGHV-M cases. GEP results were validated by qPCR on 27 independent CLL samples. The impact of GE of the PD1 axis on clinical outcomes in CLL cases (median follow-up 39 months, range 6−82 months) indicated TTFT was significantly shorter in cases with higher levels of PDL2, while no significant differences were detected based on higher or lower PD1 or PDL1 levels. Multivariate analysis indicated higher PDL2 gene expression retained an independent prognostic power (HR=1.9, 95%CI 1.1-3.4, P=.022) in predicting TTFT together with IGHV-UM status, B-lymphocytosis≥5000/mm3 (P=.020), and CD38 expression (P=.021). In situ immunolocalization of CLL tissue infiltrates showed variable expression of PD1 that characterized small lymphoid elements, while PDL1 and PDL2 (PDL2>PDL1) characterized larger medium-sized elements within proliferation centers. Co-localization studies revealed PD1 co-expression of CD20+CLL cells and in scattered CD3+ cells. Both PDL1 and PDL2 were variably expressed in CD20+CLL cells; few T-cells and macrophages showed expression of both ligands within CLL infiltrates. FC analysis of CLL cells after AAT co-culture showed a higher percentage expression of circulating PD1 axis members (n=27, PDL1>>PDL2>PD1) compared to baseline indicating that the changes in PD1 axis expression may be due to events triggered by activation of the TME. In contrast, T cell populations had higher expression of CD3+, CD4+ and CD8+ cells bearing both PD1 and PDL1, while no substantial increment for either CD3+, CD4+ or CD8+/PDL2+ cells following AAT co-culture. GE analysis also showed a similar increase in PDLs (n=15, PDL2>>PDL1>PD1) expression with respect to non-activated B-CLL cells. Interestingly, a 48h co-culture of B-CLL with HS5 stromal cells (n=6) showed a similar increase in PD1 axis GE pattern as AAT cultures. Expression of miR-424 also decreased significantly (<80%) after AAT co-cultures (n=6), indicating its potential involvement in PDL1 regulation. IB reduced PD1/PDL1 gene and protein expression on CLL B-cells; the IB inhibitory effect was also observed only on CD8+ cells.We indicate that PDL2 expression characterizes a subset of high-risk early stage CLL patients. PD1 axis expression is characteristic of the CLL TME whereby modulatory co-stimulatory signals may be counteracted by IB. Further studies will examine the role of miR-424 regulation with this cellular context. DisclosuresNo relevant conflicts of interest to declare.

Expression of cancer cell-intrinsic PD-1 associates with PD-L1 and p-S6 and predicts a good prognosis in nasopharyngeal carcinoma

Aims: Programmed cell death ligand 1 (PD-L1) is the ligand of programmed death 1 (PD-1), which is a host immunity inhibitory receptor. Expression of PD-L1 in diverse tumor types has been widely discussed, while there is little research about tumor intrinsic-PD-1. Phospho-S6 (p-S6) is an important downstream effector in the PI3K/AKT/mTOR pathway. Our study was focused on investigating expression of cancer cell-intrinsic PD-1, PD-L1 and p-S6 proteins and aimed to illustrate their relationship and clinical significances in nasopharyngeal carcinoma (NPC).Methods: The expression of PD-1, PD-L1 and p-S6 proteins in tissues of NPC, non-cancerous nasopharyngeal epithelia, primary cancer and matching metastatic lesion was detected by immunohistochemistry.Results: Expression of PD-1, PD-L1 and p-S6 proteins and co-expression of PD-1 and PD-L1 were significantly higher in NPC (all P<0.05). The expression of PD-1 and co-expression of PD-1 and PD-L1 in paired metastatic NPC were significantly increased (all P<0.01). NPC patients with positive expression of PD-L1 showed significantly higher overall survival rate (P =0.035). However, NPC patients with positive expression PD-1 and p-S6 showed significantly lower overall survival rate (P =0.031, P=0.044, respectively). Interestingly, NPC patients with co-expression of PD-1 and PD-L1 had lower overall survival rate (P=0.042). Multivariate Cox proportional hazard regression analysis confirmed that positive expression of PD-L1 and p-S6 were independent prognostic factors for NPC patients.Conclusions: Expression of cancer cell-intrinsic PD-1 associates with PD-L1 and p-S6 proteins, PD-L1 might serve as a good prognostic biomarker, while p-S6 could be an independent poor prognostic biomarker for NPC patients.

Abstract A124: Preclinical characterization of AB154, a fully humanized anti-TIGIT antibody, for use in combination therapies

Abstract TIGIT (T-cell immunoreceptor with Ig and ITIM domains) is an inhibitory receptor that is expressed on natural killer (NK) cells, CD8+ T-cells, and immunosuppressive regulatory T-cells (Treg). DNAM-1 (DNAX Accessory Molecule-1; CD226) is an activating receptor found on NK cells, monocytes and a subset of T-cells. TIGIT and DNAM-1 are paired receptors that compete for shared ligands CD155 (PVR) and CD112 (Nectin-2) expressed by tumor and antigen-presenting cells. TIGIT binding to CD155 or CD112 results in immune suppression, whereas binding of DNAM-1 to the same ligands mediates immune activation. As malignancies progress, high TIGIT expression often occurs alongside the upregulation of other immune checkpoint proteins and markers of T-cell exhaustion such as PD-1 (Programmed Death-1). We have developed AB154 to inhibit TIGIT and shift the balance in the tumor microenvironment towards a more productive anticancer response. Blockade of multiple immune checkpoint proteins can confer effective and durable responses in the treatment of cancer. Data assembled from TCGA (The Cancer Genome Atlas) identified numerous tumor types in which TIGIT is co-expressed with PD-1. In these tumors, TIGIT and PD-1 were significantly upregulated compared to normal adjacent tissue. Immunophenotyping performed on human tumor infiltrating lymphocytes demonstrated a strong correlation between TIGIT and PD-1 co-expression on specific immune cells including CD8+ T-cells and Treg cells. AB154 is a fully humanized antibody that blocks human TIGIT with sub-nanomolar affinity, as determined using a CHO.hTIGIT over-expressing cell line and primary human T-cells. Functional consequences of blocking TIGIT/CD155 interactions in combination with anti-PD-1 or anti-PD-L1 were evaluated using mixed lymphocyte reactions (MLR). Briefly, we show here that co-cultures of GM-CSF/IL-4-differentiated CD155+ PD-L1+ monocytes and TIGIT+ CD4+ T-cells, in the presence of AB154, significantly increased IFN-gamma secretion when combined with anti-PD-1 or anti-PD-L1 blocking antibodies relative to each monotherapy. Understanding pharmacokinetic (PK) and pharmacodynamic (PD) relationships enables the choice of a dosing regimen that provides adequate target coverage. To evaluate the PD effects of AB154 in clinical samples, we developed a multicolor flow cytometry-based assay that utilizes an anti-TIGIT antibody that is competitive with AB154 to determine receptor occupancy. In human whole blood, ex vivo addition of AB154 achieved complete inhibition of TIGIT. Analysis of blood mononuclear cells, including CD8+ and CD4+ T-cells, Treg and NK cells, demonstrated target engagement by AB154 suitable for clinical development. In addition, we examined TIGIT receptor occupancy of AB154 (added to whole blood ex vivo) in a small cohort of non-small cell lung cancer (NSCLC) patients treated with anti-PD-1 antibody pembrolizumab. In these samples, TIGIT receptor occupancy by AB154 was comparable to that obtained with healthy donor blood samples. The data presented here provide: 1) rationale for combining AB154 with our in-house developed anti-PD-1 antibody (AB122) in upcoming clinical trials, and 2) methodology to evaluate TIGIT receptor occupancy in the upcoming AB154 dose escalation studies. AB154 is expected to enter clinical trials in 2018. Citation Format: Amy E. Anderson, Annette Becker, FangFang Yin, Hema Singh, Xiaoning Zhao, Lisa Seitz, Rick Stanton, Nigel P.C. Walker, Joanne B.L. Tan. Preclinical characterization of AB154, a fully humanized anti-TIGIT antibody, for use in combination therapies [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A124.

Abstract A207: PD-1-functionality and CD28 molecule expression in CD8+ T-cells of cancer patients

Abstract The main objective of cancer immunotherapy is an efficacious control over tumor progression through the generation of a strong and persistent T-cell mediated immune response. T-cells constantly exposed to tumor-associated antigens experience phenotypic and functional changes, acquiring a dysfunctional state due, at least in part, to the expression of co-inhibitory receptors including Programmed Death 1 (PD-1). Nevertheless, recently it has been demonstrated that the main downstream target of PD-1-mediated signaling is CD28, opening an important implication for the immune checkpoint blockade in cancer immunotherapy. Recently we have demonstrated that CD8+ T-cell anti-tumor functional advantage induced by combined chemotherapy before peptide-vaccination is determined by tumor antigen nature, immune-checkpoint phenotype, TCR repertoire diversity and antitumor lytic capability. In particular, in accordance with several recent studies, we have observed that in Ag-specific CD8+ T-cells the co-expression of PD-1 with CD28 confers an exhausted phenotype and a defective antitumor functionality, that may be reverted by the blockade of PD-1, while a subset of Ag-specific CD8+ T-cell clones characterized by high levels of PD-1 in the absence of CD28, and the presence of ICOS, showed high proliferative capability and an AKT-dependent antitumor functionality sustained by ICOS (1-3). Herein, to better elucidate the role of PD-1 in CD8 T-cell differentiation and function, we show that, differently from functional PD1-positive/CD28-negative T-cells, Ag- specific CD8+ T-cell clones are not polyfunctional, not able to lyse tumor cells and did not possess an active AKT pathway when PD-1 and CD28 were co-expressed. This suggests that the AKT kinase was activated in these T-cells expressing PD-1 but not CD28. To clarify the complex role of PD-1 in regulating T-cell functionality on the basis of our observations obtained in tumor Ag-specific CD8+ T-cell clones, we have analyzed the phenotypic and functional distribution of CD8+ T-cells, with respect to PD-1 and CD28 expression, in patients with different types of cancer. Preliminary results indicate that functional distinct PD-1/CD28 CD8+ T-cell subsets can be found in peripheral blood of cancer patients with a pattern of functionality similar to that identified in CD8 T-cell clones. Furthermore, to identity whether the lung tumor microenvironment may influence the frequency and functionality of these T-cell populations, we have compared these subsets in the periphery and tumor site in lung cancer. These results may clarify the complex role of PD-1 in regulating T-cell functionality and may provide a significant perspective for exploiting the functional significance of T-cell subsets defined by PD-1/CD28 expression, to predict and monitor tumor responsive T-cells during immunotherapy treatments based on PD-1 blockade.§ B.P. and O.F. contributed equally to this work.

Squamous cell carcinomas escape immune surveillance via inducing co-expression of PD-1 and LAG-3 inhibitory receptors on tumor infiltrating T lymphocytes

Abstract Squamous cell carcinoma (SCC) is the second commonest type of skin cancer. About 90% of head and neck cancers are SCCs. It remains largely unknown how SCCs evade immune recognition. We recently established a mouse model by injecting tumor cells derived from primary SCCs harboring KrasG12D mutation and Smad4 deletion into wild-type (wt) or CD8−/− recipients. We found comparable tumor growth between wt and CD8−/− recipients, indicating a complete escape of CD8+ T cell-mediated anti-tumor responses by these SCCs. Mechanistically, CD8+ T cells were not defective in infiltrating tumors given their relatively increased percentage among tumor infiltrating lymphocytes (TILs). CD8+ TILs exhibited phenotypes of chronic activation and exhaustion, manifested with co-expression of programmed death 1 (PD-1) and lymphocyte activation gene-3 (LAG-3). Among CD4+ TILs, T regulatory cells (Tregs) were preferentially expanded. Contradictory to prior findings in melanoma, Treg expansion was independent of CD8+ T cells in our SCC model. Unexpectedly, CD8+ T cells were required for promoting NK cell infiltration within SCCs. Furthermore, we uncovered AKT-dependent lymphocyte-induced PD-L1 upregulation on SCCs, which was contributed greatly by combinatorial effects of CD8+ T and NK cells. Lastly, dual blockade of PD-1 and LAG-3 inhibited the tumor growth of SCCs. Thus, our findings identify novel immune evasion mechanisms of SCCs and suggest that immunosuppressive mechanisms operate in a cancer-type specific and context-dependent manner.

Higher PD-1 expression concurrent with exhausted CD8+ T cells in patients with de novo acute myeloid leukemia.

To investigate the association between the T cell inhibitory receptor programmed death 1 (PD-1) and T cell exhaustion status in T cells from patients with de novo acute myeloid leukemia (AML) and AML in complete remission (CR). Surface expression of PD-1 and the exhaustion and immunosenescence markers CD244 and CD57 on CD3+, CD4+ and CD8+ T cells from peripheral blood samples from 20 newly diagnosed, untreated AML patients and 10 cases with AML in CR was analyzed by flow cytometry. Twenty-three healthy individuals served as control. A significantly higher percentage of PD-1+ cells were found for CD3+ T cells in the de novo AML group compared with healthy controls. In addition, an increased level of PD-1+CD8+ T cells, but not PD-1+CD4+, was found for CD3+ T cells in the de novo AML and AML-CR samples. A higher percentage of CD244+CD4+, CD244+CD8+, CD57+CD4+ and CD57+CD8+ T cells was found in CD3+ T cells in samples from those with de novo AML compared with those from healthy controls. Strong increased PD-1+CD244+ and PD-1+CD57+ co-expression was found for CD4+ and CD8+ T cells in the de novo AML group compared with healthy controls. We characterized the major T cell defects, including co-expression of PD-1 and CD244, CD57-exhausted T cells in patients with de novo AML, and found a particular influence on CD8+ T cells, suggesting a poor anti-leukemia immune response in these patients.

Cooperation of PD-1 and LAG-3 Contributes to T-Cell Exhaustion in Anaplasma marginale-Infected Cattle

The CD4(+) T-cell response is central for the control of Anaplasma marginale infection in cattle. However, the infection induces a functional exhaustion of antigen-specific CD4(+) T cells in cattle immunized with A. marginale outer membrane proteins or purified outer membranes (OMs), which presumably facilitates the persistence of this rickettsia. In the present study, we hypothesize that T-cell exhaustion following infection is induced by the upregulation of immunoinhibitory receptors on T cells, such as programmed death 1 (PD-1) and lymphocyte activation gene 3 (LAG-3). OM-specific T-cell responses and the kinetics of PD-1-positive (PD-1(+)) LAG-3(+) exhausted T cells were monitored in A. marginale-challenged cattle previously immunized with OMs. Consistent with data from previous studies, OM-specific proliferation of peripheral blood mononuclear cells (PBMCs) and interferon gamma (IFN-γ) production were significantly suppressed in challenged animals by 5 weeks postinfection (wpi). In addition, bacteremia and anemia also peaked in these animals at 5 wpi. Flow cytometric analysis revealed that the percentage of PD-1(+) LAG-3(+) T cells in the CD4(+), CD8(+), and γδ T-cell populations gradually increased and also peaked at 5 wpi. A large increase in the percentage of LAG-3(+) γδ T cells was also observed. Importantly, in vitro, the combined blockade of the PD-1 and LAG-3 pathways partially restored OM-specific PBMC proliferation and IFN-γ production at 5 wpi. Taken together, these results indicate that coexpression of PD-1 and LAG-3 on T cells contributes to the rapid exhaustion of A. marginale-specific T cells following infection and that these immunoinhibitory receptors regulate T-cell responses during bovine anaplasmosis.

Programmed death-1 (PD-1), programmed death-ligand 1 (PD-L1), and EBV-encoded RNA (EBER) expression in Hodgkin lymphoma.

Programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) are new targets in cancer immunotherapy. PD-1 protein is an immune checkpoint expressed in many tumors. Epstein-Barr virus (EBV) is present in malignant Hodgkin/Reed-Sternberg (HRS) cells in approximately 40-50% of Hodgkin lymphoma (HL). The aim of this study is to evaluate the clinical and prognostic importance of PD-1 and/or PD-L1 in HL and also to determine the association between EBV-encoded RNA (EBER) and PD-1/PD-L1. Formalin-fixed, paraffin-embedded tissue samples from 87 cases with HL were analyzed in this study. Immunohistochemical staining was performed to detect the PD-1 and PD-L1 expressions. Chromogenic in situ hybridization for EBER was performed using fluorescein-labeled oligonucleotide probes. PD-1 and PD-L1 expressions were found in 20% of the cases. The EBER positivity was found in 40 cases (45%). It has been found that co-expression of PD-1 and PD-L1 was associated with shorter survival although PD-1 or PD-L1 expressions were not found to be related with survival. Overall survival (OS) and disease-free survival (DFS) in cases without PD-1 and PD-L1 expressions were 135 and 107months, respectively. OS and DFS in cases with co-expression for PD-1 and PD-L1 were 24 and 20months, respectively, and these differences were found to be statistically significant for both OS and DFS (p = 0.002 and p = 0.003, respectively). Cox regression analysis showed that co-expression of PD-1 and PD-L1 was found to be an independent risk factor for prognosis (OR 6.9, 95% CI 1.9-24.3). Targeting PD-1 and/or PD-L1 is meaningful due to the 20% expression of each in HL, and we did not find an important association between PD-1 and PD-L1 and EBER expression in HL. Very poor outcome in cases with co-expression of PD-1/PD-L1 suggests new avenues to detect the new prognostic markers and also therapeutic approaches in HL.

Expression of inhibitory receptors on CD4+ and CD8+ T cells from healthy Colombian donors

&lt;p&gt;T cell activation involves positive cellular signals that promote effector functions and negative signals that contribute to the regulation of these responses. These regulatory signals are generated upon activation of receptors on T cells that include CD160, 2B4, Programmed Death-1 and CTLA-4. &lt;strong&gt;Objective&lt;/strong&gt;. To evaluate the expression of inhibitory receptors like CD160, 2B4, Programmed Death-1 and CTLA-4 on CD4+ and CD8+ T cells from healthy Colombian donors. &lt;strong&gt;Materials and methods&lt;/strong&gt;. Peripheral blood mononuclear cells from 30 healthy donors from Bogotá (Colombia) were obtained via Ficoll-Hypaque density gradient and cells were stained with specific conjugated antibodies previously titrated. &lt;strong&gt;Results&lt;/strong&gt;. The CD160, 2B4, and Programmed Death-1 inhibitory markers were detected on CD4+ T cells&lt;br /&gt;with expression levels of 0.35%, 1.04%, and 1.35%, respectively. On CD8+ T cells, these markers were expressed at higher levels: 16%, 8.97%, and 4.3%, respectively. In contrast to the other receptors, CTLA-4 frequency of expression showed no significant difference between CD4+ (1.56%) and CD8+ (1.53%) T cells. Frequency of CD160/2B4 and CTLA-4/ Programmed Death-1 coexpression was 0.18% and 0.09% on CD4+ cells, and 4.02% and 0.2% on CD8+ T cells. &lt;strong&gt;Conclusions&lt;/strong&gt;. This is the first report showing the frequency of inhibitory receptors such as CD160, 2B4, Programmed Death-1, and CTLA-4 on CD4+ and CD8+ T cells from healthy Colombian donors. Our findings serve as a baseline for the analysis and comparison of these receptors in Colombian populations with different disease conditions.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;&lt;strong&gt;Key words&lt;/strong&gt;: inhibitory receptors, T cells&lt;/p&gt;

Expression of follicular helper T cell markers in nodal peripheral T cell lymphomas: a tissue microarray analysis of 162 cases

AimsTo evaluate the role of the follicular helper T (TFH) cell markers, CD10, BCL6, programmed death-1 (PD-1) and CXCL13, in the differential diagnosis of nodal peripheral T cell lymphomas (PTCLs)...

HCV‐specific T cells in HCV/HIV co‐infection show elevated frequencies of dual Tim‐3/PD‐1 expression that correlate with liver disease progression

Co-infection of HCV with HIV has been associated with more rapid progression of HCV-related disease. HCV-specific T-cell immune responses, which are essential for disease control, are attenuated in co-infection with HIV. T-cell exhaustion has recently been implicated in the deficient control of chronic viral infections. In the current study, we investigated the role of programmed death-1 (PD-1) and T-cell immunoglobulin and mucin domain-containing molecule-3 (Tim-3) expression in T-cell exhaustion during HCV/HIV co-infection. We show that in HCV/HIV co-infection, both total and HCV-specific T cells co-express Tim-3 and PD-1 in significantly higher frequencies, compared with HCV mono-infection. Co-expression of these two markers on HCV-specific CD8(+) T cells positively correlated with a clinical parameter of liver disease progression. HCV-specific CD8(+) T cells showed greater frequencies of Tim-3/PD-1 co-expression than HIV-specific CD8(+) T cells, which may indicate a greater degree of exhaustion in the former. Blocking Tim-3 or PD-1 pathways restored both HIV- and HCV-specific CD8(+) T-cell expansion in the blood of co-infected individuals. These data demonstrate that co-expression of Tim-3 and PD-1 may play a significant role in HCV-specific T-cell dysfunction, especially in the setting of HIV co-infection.