CD8+ T-Cell Exhaustion Phenotype in Chronic Hepatitis C Virus Infection Is Associated With Epitope Sequence Variation

Deciphering T-cell exhaustion in the tumor microenvironment: paving the way for innovative solid tumor therapies

In solid tumors, the tumor microenvironment (TME) is a complex mix of tumor, immune, stromal cells, fibroblasts, and the extracellular matrix. Cytotoxic T lymphocytes (CTLs) constitute a fraction of immune cells that may infiltrate into the TME. The primary function of these T-cells is to detect and eliminate tumor cells. However, due to the immunosuppressive factors present in the TME primarily mediated by Myeloid-Derived Suppressor Cells (MDSCs), Tumor associated macrophages (TAMs), Cancer Associated Fibroblasts (CAFs) as well as the tumor cells themselves, T-cells fail to differentiate into effector cells or become dysfunctional and are unable to eliminate the tumor. In addition, chronic antigen stimulation within the TME also leads to a phenomenon, first identified in chronic lymphocytic choriomeningitis virus (LCMV) infection in mice, where the T-cells become exhausted and lose their effector functions. Exhausted T-cells (Tex) are characterized by the presence of remarkably conserved inhibitory receptors, transcription and signaling factors and the downregulation of key effector molecules. Tex cells have been identified in various malignancies, including melanoma, colorectal and hepatocellular cancers. Recent studies have indicated novel strategies to reverse T-cell exhaustion. These include checkpoint inhibitor blockade targeting programmed cell death protein 1 (PD-1), T-cell immunoglobulin and mucin-domain containing-3 (Tim-3), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), or combinations of different immune checkpoint therapies (ICTs) or combination of ICTs with cytokine co-stimulation. In this review, we discuss aspects of T-cell dysfunction within the TME with a focus on T-cell exhaustion. We believe that gaining insight into the mechanisms of T-cell exhaustion within the TME of human solid tumors will pave the way for developing therapeutic strategies to target and potentially re-invigorate exhausted T-cells in cancer.

Alterations in the hepatic microenvironment following direct-acting antiviral therapy for chronic hepatitis C

Background and aims. The first direct-acting antivirals (DAAs) to treat the viral hepatitis C (HCV) became available in 2011. Despite numerous clinical studies of patient outcomes after treatment, few have evaluated changes in the liver microenvironment. Despite achieving sustained virologic response (SVR), patients may still experience adverse outcomes like cirrhosis and hepatocellular carcinoma. By comparing gene and protein expression in liver biopsies collected before and after treatment, we sought to determine whether specific signatures correlated with disease progression and adverse clinical outcomes. Methods. Biopsies were collected from 22 patients before and after DAA treatment. We measured ∼770 genes and used multispectral imaging with custom machine learning algorithms to analyze phenotypes of intrahepatic macrophages (CD68, CD14, CD16, MAC387, CD163) and T cells (CD3, CD4, CD8, CD45, FoxP3). Results. Before DAA treatment, patients showed two distinct gene expression patterns: one with high pro-inflammatory and antiviral gene expression and another with weaker expression. Patients with adverse outcomes exhibited significantly (p<0.05) more inflammatory activity and had more advanced fibrosis stages in their baseline biopsies than those with liver disease resolution. Patients who achieved SVR had significantly decreased liver enzymes, reduced inflammatory scores, and restored type 1 interferon pathways similar to controls. However, after DAA treatment, patients with persistently high gene expression (67%, pre-hot) still had significantly worse outcomes (p<0.049) despite achieving SVR. A persistent lymphocytic infiltrate was observed in a subset of these patients (76.5%). After therapy, anti-inflammatory macrophages (CD16+, CD16+CD163+, CD16+CD68+) increased, and T cell heterogeneity was more pronounced, showing a predominance of helper and memory T cells (CD3+CD45RO+, CD4+CD45RO+, CD3+CD4+CD45RO+). Conclusions. Patients who have more inflamed livers and more advanced fibrosis before DAA treatment should be closely followed for the development of adverse outcomes, even after achieving SVR. We can enhance patient risk stratification by integrating gene and protein expression profiles with clinical data. This could identify those who may benefit from more intensive monitoring or alternative therapeutic approaches, inspiring a new era of personalized patient care.

Lay Summary

Direct-acting antiviral (DAA) therapy has dramatically improved the treatment of chronic HCV, making it curable for most people. This study determined gene and protein expression differences in the liver before and after treatment of HCV. These results will lead to a deeper understanding of the changes in the hepatic immune microenvironment with and without the virus present in the liver in hopes of improving patient surveillance, prognosis, and outcome in the future.

In silico analysis of the effect of HCV genotype-specific polymorphisms in Core, NS3, NS5A, and NS5B proteins on T-cell epitope processing and presentation

Background

HCV genotypes are 30-35% polymorphic at the nucleotide level, while subtypes within the same genotype differ by nearly 20%. Although previous studies have shown the immune escape potential of several mutations within the HCV proteins, little is known about the effect of genotype/subtype-specific gene polymorphism on T-cell immunity. Therefore, this study employed several in silico methods to examine the impact of genotype/subtype-specific polymorphisms in Core, NS3, NS5A, and NS5B sequences on T cell epitope processing and HLA-epitope interactions.

Methods

For this study, 8,942, 17,700, 14,645, and 3,277 HCV Core, NS3, NS5A, and NS5B sequences, respectively, from eight genotypes and 21 subtypes were retrieved from the Los Alamos HCV Database. Next, the NetCTL tool was employed to predict Cytotoxic T Lymphocyte (CTL) epitopes based on combined proteasomal cleavage, TAP efficacy, and HLA class I receptor binding scores. PEP-FOLD was used to model selected epitopes, followed by peptide-HLA docking using HPEPDOCK. Finally, molecular dynamics simulations were conducted for 200 ns using Desmond software to analyze differences in HLA-epitope (from different HCV genotypes) interaction kinetics and dynamics.

Results

A total of 3,410, 8,054, 6,532, and 14,015 CTL epitopes were observed in the HCV Core, NS3, NS5A, and NS5B sequences, respectively. Significant genotype/subtype-specific variations in CTL values and docking scores were observed among NS3, NS5A, and NS5B proteins. In silico results reveal that epitopes from genotype 6b (NS3), 6d/r (NS5B), 6o and 6 k (NS5A) exhibit higher immunogenicity than other genotypes, forming more energetically stable complexes with host receptors. These epitopes, compared to those from the same positions but different genotypes, showed binding energies of -144.24 kcal/mol, -85.30 kcal/mol, and - 43 kcal/mol, respectively. Over a 200 ns MD simulation, GT 6b and 6d/r epitopes displayed up to a 40% stronger binding energy with the HLA receptor. These findings suggest that patients infected with GT 6 may experience enhanced T cell responsiveness and broader immunogenicity.

Conclusion

Our study suggests that genotype/subtype-specific polymorphism in HCV may result in altered immune responses by modulating T-cell epitope processing and interaction with HLA receptors. Further experimental studies can be performed to confirm the effect of genotype/subtype-specific polymorphisms on T cell-mediated immune response.

Development of a Multiple-Epitope-Based Vaccine for Hepatitis C Virus Genotypes 1a and 1b: an in-silico reverse vaccinology approach

The Hepatitis C virus (HCV) is a blood-transmitted virus responsible for persistent inflammation, presenting a substantial worldwide health challenge. HCV, characterized by a positive-stranded ribonucleic acid genome, possesses an intricate genetic makeup encoding both structural and non-structural proteins, crucial for sustaining its life cycle. The Direct Acting Antivirals have revolutionized the treatment landscape of HCV promoting higher Sustained Virological Response rates. Despite significant advancements in treatment, no vaccines are currently available against HCV. The development of effective HCV vaccines becomes challenging as the genetic diversity of HCV virus and its complex nature of the immune response required for protection. In this work, the immunoinformatics methods were utilized to develop a multiple-epitope-based vaccine towards an effective treatment against the viral HCV polyprotein. The vaccine was constructed by T-cell epitopes extracted from the viral polyprotein of HCV genotypes 1a and 1b. The vaccine was highly antigenic, non-toxic, and non-allergenic. Effective binding of the designed vaccine construct was studied by forming complexes with the human immune Toll-Like Receptors; TLR3 and TLR8. The MD simulation of these receptor-vaccine complexes were performed for 50ns and the immunological simulation of modeled vaccine in presence of receptors for 365 days timeline validated the stability of the constructed vaccine. The in-silico vaccine construct developed from this work might be beneficial as prophylactic measures against the HCV variants, if explored further in in vivo and in vitro methods. Consequently, this research outcome is presumed to have implications in the development of safer and more efficient vaccines for lethal diseases.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00275-4.

T-Cell Exhaustion in HIV-1/Hepatitis C Virus Coinfection Is Reduced After Successful Treatment of Chronic Hepatitis C

Background

T-cell responses during chronic viral infections become exhausted, which is reflected by upregulation of inhibitory receptors (iRs) and increased interleukin 10 (IL-10). We assessed 2 iRs-PD-1 (programmed cell death protein 1) and Tim-3 (T-cell immunoglobulin and mucin domain-containing protein 3)-and IL-10 mRNAs in peripheral blood mononuclear cells (PBMCs) and their soluble analogs (sPD-1, sTim-3, and IL-10) in plasma in chronic HIV-1/hepatitis C virus (HCV) coinfection and explored the effect of HCV treatment on these markers. We also aimed to establish whether iR expression may be determined by the HCV CD8+ T-cell immunodominant epitope sequence.

Methods

Plasma and PBMCs from 31 persons with chronic HIV-1/HCV coinfection from the Swiss HIV Cohort Study were collected before and after HCV treatment. As controls, 45 persons who were HIV-1 negative with chronic HCV infection were recruited. Exhaustion markers were assessed by enzyme-linked immunosorbent assay in plasma and by quantitative reverse transcription polymerase chain reaction in PBMCs. Analysis of an HCV epitope sequence was conducted by next-generation sequencing: HLA-A*02-restricted NS31073-1081 and NS31406-1415 and HLA-A*01-restricted NS31436-1444.

Results

The study revealed higher plasma sPD-1 (P = .0235) and IL-10 (P = .002) levels and higher IL-10 mRNA in PBMCs (P = .0149) in HIV-1/HCV coinfection. A decrease in plasma sPD-1 (P = .0006), sTim-3 (P = .0136), and IL-10 (P = .0003) and Tim-3 mRNA in PBMCs (P = .0210) was observed following successful HCV treatment. Infection with the HLA-A*01-restricted NS31436-1444 ATDALMTGY prototype variant was related to higher sTim-3 levels than infection with the ATDALMTGF escape variant (P = .0326).

Conclusions

The results underscore the synergistic effect of coinfection on expression of exhaustion markers, their reduction following successful HCV treatment and imply that iR levels may operate on an epitope-specific manner.

Double Positive CD4+CD8+ (DP) T-Cells Display Distinct Exhaustion Phenotype in Chronic Hepatitis C

In chronic hepatitis C (CHC), characterized by exhaustion of T-cell function, increased frequencies of double-positive (DP) (CD4⁺CD8⁺) cells are present in peripheral blood. We compared the exhaustion phenotype between DP and single positive (SP) T-cells, including HCV-specific cells, and assessed the effect of successful HCV treatment on inhibitory receptors expression. Blood samples from 97 CHC patients were collected before and six months post-treatment. PD-1 (programmed cell death protein 1) and Tim-3 (T-cell immunoglobulin and mucin domain-containing molecule-3) expression was assessed by flow cytometry. DP T-cells displayed significantly higher PD-1 expression, lower Tim-3 expression than CD8⁺ SP T-cells and lower percentages of PD-1^-Tim-3^- cells than CD4⁺ SP T-cells, both before and after treatment. PD-1⁺Tim-3⁺ DP T-cells decreased following treatment. HCV-specific cells were more frequent among DP than SP T-cells, both before and after treatment. HCV-specific DP T-cells were characterized by lower PD-1 expression, higher PD-1 and Tim-3 co-expression, and lower percentages of PD-1^-Tim-3^- cells (both before and after treatment) and higher post-treatment Tim-3 than HCV-specific SP T-cells. Their percentages decreased following treatment, but the exhaustion phenotype remained unchanged. DP T-cells in CHC exhibit a distinct exhaustion phenotype from SP T-cells, and these changes mostly persist following successful treatment.

Studying T Cell Responses to Hepatotropic Viruses in the Liver Microenvironment

T cells play an important role in the clearance of hepatotropic viruses but may also cause liver injury and contribute to disease progression in chronic hepatitis B and C virus infections which affect millions of people worldwide. The liver provides a unique microenvironment of immunological tolerance and hepatic immune regulation can modulate the functional properties of T cell subsets and influence the outcome of a virus infection. Extensive research over the last years has advanced our understanding of hepatic conventional CD4+ and CD8+ T cells and unconventional T cell subsets and their functions in the liver environment during acute and chronic viral infections. The recent development of new small animal models and technological advances should further increase our knowledge of hepatic immunological mechanisms. Here we provide an overview of the existing models to study hepatic T cells and review the current knowledge about the distinct roles of heterogeneous T cell populations during acute and chronic viral hepatitis.

T-Cell Receptor Repertoire Sequencing and Its Applications: Focus on Infectious Diseases and Cancer

The immune system is a dynamic feature of each individual and a footprint of our unique internal and external exposures. Indeed, the type and level of exposure to physical and biological agents shape the development and behavior of this complex and diffuse system. Many pathological conditions depend on how our immune system responds or does not respond to a pathogen or a disease or on how the regulation of immunity is altered by the disease itself. T-cells are important players in adaptive immunity and, together with B-cells, define specificity and monitor the internal and external signals that our organism perceives through its specific receptors, TCRs and BCRs, respectively. Today, high-throughput sequencing (HTS) applied to the TCR repertoire has opened a window of opportunity to disclose T-cell repertoire development and behavior down to the clonal level. Although TCR repertoire sequencing is easily accessible today, it is important to deeply understand the available technologies for choosing the best fit for the specific experimental needs and questions. Here, we provide an updated overview of TCR repertoire sequencing strategies, providers and applications to infectious diseases and cancer to guide researchers’ choice through the multitude of available options. The possibility of extending the TCR repertoire to HLA characterization will be of pivotal importance in the near future to understand how specific HLA genes shape T-cell responses in different pathological contexts and will add a level of comprehension that was unthinkable just a few years ago.