Abstract
Introduction: T cell Immunoglobulin Mucin-3 (TIM-3) TIM-3 acts as a negative regulator of (T helper-1)Th1/ (T Cytotoxic-1)Tc1 cell function by triggering cell death upon interaction with its ligand Galectin-9, a feature observed in chronic viral diseases. Objective: To demonstrate the level of expression of TIM-3 on Peripheral Blood Mononuclear cells (PBCs) in cases of chronic HCV as a number of emerging molecules and pathways have been implicated in mediating the Tcell exhaustion characteristic of chronic viral infection. Patients and Methods: This study included 90 subjects, divided up as follows: Group 1 (35 patients) included HCV antibody positive with normal liver functions (Compensated), Group 2 (35 patients) comprised HCV antibody positive patients with abnormal liver functions (decompensated), and controls (Group 3) involved 20 apparently healthy persons (HCV antibody negative persons). The following laboratory investigations were performed for all participants in the 3 groups: Complete Blood Count (CBC), Blood Chemistry (liver functions), Special investigations (Flowcytometric study, and PCR for HCV RNA). Results: Comparing the control, compensated and decompensated groups regarding lymphocytic counts, ratios of TIM-3 positive cells within CD4, CD8, CD14 and CD56 cells in the three groups. Ratio of CD4 cells was higher in the compensated and control groups, than in the decompensated group, with non-significant difference. CD8 cells were maximum in the decompensated groups and minimum in the compensated group, with a significant p value. CD14 cells were maximum in the compensated group, followed by decompensated and minimum in the control group, again with a significant difference. CD56 showed non-significant differences between the three groups. A steady increase in the percentage of TIM +ve CD4, CD8, CD14 and CD 56 cells, with maximum percentages among the decompensated liver disease group, and least percentage among the control group was seen. The differences were significant regarding CD8 and CD56 and highly significant regarding CD4 and CD14 cells. Conclusions: Accumulation of TIM-3+ T cells is associated with functional impairment, and consequently with development of persistent HCV. The present study provides a basis for improving current therapies by simultaneous blockade of multiple inhibitory pathways that could result in additive efficacy without excessive toxicity. These findings have implications for the development of novel immunotherapeutic approaches to this common viral infection.
Keywords
TIM-3; Lymphocytes; Hepatitis C virus
Introduction
Hepatitis C virus (HCV) is a major causative agent of chronic hepatitis, affecting approximately 200 million people throughout the world. There is a broad array of functional impairments of virusspecific T cells including decreased antiviral cytokineproduction and cytotoxicity; with impaired proliferative capacity and arrested stages of differentiation [1-3].
In liver infections, CD81 T cells may show features of cells that did not receive sufficient help. Thus, in chronic lymphocytic choriomeningitis virus in mice, failure to eliminate the virus is associated with �exhausted� T cells that persist, but do not function. [4] These cells express a characteristic surface phenotype, including the markers programmed cell death 1 (PD- 1), T-cell 3 immunoglobulin and mucin domain containing protein 3 (TIM-3), and lymphocyte activation gene 3 (Lag-3) [5,6] which are also expressed on human exhausted T cells [7]. In chronic hepatitis C virus (HCV) infection, the lack of a detectable CD41 T-cell response is one of the clearest correlates of failure to eliminate the virus [8,9]. HCV-infected individuals also harbor exhausted or �stunned� CD81 T cells, defined both functionally as cells that cannot make effector cytokines [10,11], and phenotypically as cells that express PD-1 and TIM-3 [12]. Based on these data, one plausible model for liver tolerance is that, when CD81 T cells are primed in the liver, appropriate CD41 T-cell help may not always be available. The consequence is dysfunctional, exhausted CD81 T cells and thus failure to eliminate the pathogen. However, many other factors complicate this satisfyingly simple. model, in particular, the prevalence of liver antigen presenting cells (APCs) that express coinhibitory ligands, such as programmed death ligand 1 (PDL1), and which stimulate regulatory T (Treg) cells. All of these factors may contribute to immune failure through parallel mechanisms and also The T-cell immunoglobulin mucin-3 (TIM-3) receptor was recently shown to inhibit cytotoxic and cytokine responses of NK cells upon interaction with galectin-9 (Gal-9) or phosphatidylserine (PtdSer) on target cells [13�16].
TIM-3 which was first identified as a molecule specifically expressed on IFN-gamma-secreting T helper 1 and T cytotoxic 1 cells in both mice and humans, acts as a negative regulator of Th1/Tc1 cell function by triggering cell death upon interaction with its ligand, Galectin-9. This negative regulatory function of TIM-3 has now been expanded to include its involvement in establishing and/or maintaining a state of T cell dysfunction or "exhaustion" observed in chronic viral diseases. Given that an increasing body of data support an important role for TIM-3 in both autoimmune and chronic inflammatory diseases in humans [17-19]. A recent analysis of human immunodeficiency virus (HIV) infection demonstrates that TIM-3 is upregulated on both CD4 and CD8 T cells from patients with chronic infection relative to uninfected individuals and that virus-specific cells expressing high levels of TIM-3 secrete less IFN- than do TIM-3-negative cells [20]. In light of these findings, this study assessed the expression of TIM-3 in chronic HCV infection. We found a higher frequency of TIM-3- expressing CD4 and CD8 T cells in chronic HCV infection. These findings have implications for the development of novel immunotherapeuticapproaches to this common disease.
Aim of the study
To demonstrate the level of expression of TIM-3 on Peripheral Blood Mononuclear cells (PBCs) in cases of chronic HCV during different stages and to clarify its possible role in the pathology of the disease.
Patients and Methods
This study included 90 subjects, divided as follows: Patients group was split into two groups: Group 1 (35 patients) included HCV antibody positive/ HCV RT- PCR positive patients with normal liver functions (Compensated), Group 2 (35 patients) comprised HCV antibody positive/HCV RT-PCR positive patients with abnormal liver functions (decompensated), and controls (Group 3) involved 20 apparently healthy persons (HCV antibody negative individuals).