Dysfunction and functional restoration of HCV-specific CD8 responses in chronic hepatitis C virus infection

The role of immune regulation in HBV infection and hepatocellular carcinogenesis

Hepatitis B virus (HBV) infection is a well-documented independent risk factor for developing hepatocellular carcinoma (HCC). Consequently, extensive research has focused on elucidating the mechanisms by which HBV induces hepatocarcinogenesis. The majority of studies are dedicated to understanding how HBV DNA integration into the host genome, viral RNA expression, and the resulting protein transcripts affect cellular processes and promote the malignant transformation of hepatocytes. However, considering that most acute HBV infections are curable, immune suppression potentially contributes to the critical challenges in the treatment of chronic infections. Regulatory T cells (Tregs) are crucial in immune tolerance. Understanding the interplay of Tregs within the liver microenvironment following HBV infection could offer novel therapeutic approaches for treating HBV infections and preventing HBV-related HCC. Two viewpoints to targeting Tregs in the liver microenvironment include means of reducing their inhibitory function and decreasing Treg frequency. As these strategies may disrupt the immune balance and lead to autoimmune responses, careful and comprehensive profiling of the patient's immunological status and genetic factors is required to successfully employ this promising therapeutic approach.

Immune checkpoint inhibitors in infectious disease

Following success in cancer immunotherapy, immune checkpoint blockade is emerging as an exciting potential treatment for some infectious diseases, specifically two chronic viral infections, HIV and hepatitis B. Here, we will discuss the function of immune checkpoints, their role in infectious disease pathology, and the ability of immune checkpoint blockade to reinvigorate the immune response. We focus on blockade of programmed cell death 1 (PD-1) to induce durable immune-mediated control of HIV, given that anti-PD-1 can restore function to exhausted HIV-specific T cells and also reverse HIV latency, a long-lived form of viral infection. We highlight several key studies and future directions of research in relation to anti-PD-1 and HIV persistence from our group, including the impact of immune checkpoint blockade on the establishment (AIDS, 2018, 32, 1491), maintenance (PLoS Pathog, 2016, 12, e1005761; J Infect Dis, 2017, 215, 911; Cell Rep Med, 2022, 3, 100766) and reversal of HIV latency (Nat Commun, 2019, 10, 814; J Immunol, 2020, 204, 1242), enhancement of HIV-specific T cell function (J Immunol, 2022, 208, 54; iScience, 2023, 26, 108165), and investigating the effects of anti-PD-1 and anti-CTLA-4 in vivo in people with HIV on ART with cancer (Sci Transl Med, 2022, 14, eabl3836; AIDS, 2021, 35, 1631; Clin Infect Dis, 2021, 73, e1973). Our future work will focus on the impact of anti-PD-1 in vivo in people with HIV on ART without cancer and potential combinations of anti-PD-1 with other interventions, including therapeutic vaccines or antibodies and less toxic immune checkpoint blockers.

Blood MAIT cells phenotype in patients with Opisthorchis felineus invasion depending on the severity of liver fibrosis

Introduction. MAIT cells are a new subpopulation of T cells that protect mucous barriers against penetration of foreign substances. There are practically no studies devoted to the participation of these cells in the pathogenesis of parasitic diseases.

Aim. To study the phenotype of blood MAIT cells in patients with Opisthorchis felineus (O. felineus) invasion depending on the severity of liver fibrosis.

Materials and methods. A total of 78 patients with O. felineus invasion (42 men and 36 women) and 26 control group individuals (14 men and 12 women) were examined. Opisthorchiasis was diagnosed using coproovoscopy and duodenal contents microscopy. All patients underwent liver elastometry using Aixplorer (France) or Siemens Acuson S2000 (Germany) systems with determination of the liver fibrosis degree according to METAVIR. The phenotype composition of lymphocytes was investigated using a Navios flow cytometer (Beckman Coulter, USA). T cells, T helpers, and T cytotoxic lymphocytes were isolated and the presence of NCR Va7.2 and CD161 on the surface of these cells was assessed.

Results. The content of MAIT T-helpers was decreased in patients with O. felineus invasion compared to healthy individuals (p < 0.001). In MAIT T-cytotoxic cells, a similar pattern was not detected (p = 0.5). In patients with liver fibrosis F2 according to METAVIR compared to individuals with F0 according to METAVIR, a decrease in the total number of T-cells, T-helpers and T-cytotoxic cells, as well as MAIT T-helpers and MAIT T-cytotoxic cells was observed. Thus, the content of CD161+ NCR Va7.2+ T-helpers was 0.020% [0.004–0.042%] in patients with opisthorchiasis with F0 according to METAVIR and 0.0% [0.0–0.003%] in individuals with liver fibrosis F2 according to METAVIR (p = 0.001). For CD161+ NCR Va7.2+ T-cytotoxic cells, these indicators were, respectively, 1.47% [0.41–2.49%] and 0.12% [0.07–0.31%] (p < 0.001).

Conclusion. Further study of MAIT cells in patients with liver pathology has undoubted prospects for the creation of new therapeutic and diagnostic technologies.

Frequency of the Main Human Leukocyte Antigen A, B, DR, and DQ Loci Known to Be Associated with the Clearance or Persistence of Hepatitis C Virus Infection in a Healthy Population from the Southern Region of Morocco: A Preliminary Study

Hepatitis C Virus (HCV) infection represents a significant global health challenge, with its natural course largely influenced by the host's immune response. Human Leukocyte Antigen (HLA) molecules, particularly HLA class I and II, play a crucial role in the adaptive immune response against HCV. The polymorphism of HLA molecules contributes to the variability in immune response, affecting the outcomes of HCV infection. This study aims to investigate the frequency of HLA A, B, DR, and DQ alleles known to be associated with HCV clearance or persistence in a healthy Moroccan population. Conducted at the University Hospital Center Mohammed VI, Marrakech, this study spanned from 2015 to 2022 and included 703 healthy Moroccan individuals. HLA class I and II typing was performed using complement-dependent cytotoxicity and polymerase chain reaction-based methodologies. The results revealed the distinct patterns of HLA-A, B, DRB1, and DQB1 alleles in the Moroccan population. Notably, alleles linked to favorable HCV outcomes, such as HLA-DQB1*0301, DQB1*0501, and DRB1*1101, were more prevalent. Conversely, alleles associated with increased HCV susceptibility and persistence, such as HLA-DQB1*02 and DRB1*03, were also prominent. Gender-specific variations in allele frequencies were observed, providing insights into genetic influences on HCV infection outcomes. The findings align with global trends in HLA allele associations with HCV infection outcomes. The study emphasizes the role of host genetics in HCV infection, highlighting the need for further research in the Moroccan community, including HCV-infected individuals. The prevalence of certain HLA alleles, both protective and susceptibility-linked, underscores the potential for a national HLA data bank in Morocco.

The expression and significance of PD-L1 in condyloma acuminatum

BACKGROUND

It has been reported that programmed death-ligand 1 (PD-L1) is highly expressed in cells during viral infection, which helps the virus escape host immunity. However, the relationship between human papillomavirus (HPV) and PD-L1 in condyloma acuminatum and whether they participate in immunosuppression have not been reported. In this paper, we aimed to explore the expression and significance of PD-L1 in condyloma acuminatum.

METHODS

The expression of PD-L1 in the wart of condyloma acuminatum patients and the foreskin of healthy individuals was evaluated. Lentivirus transfection was used to introduce the HPV11-E7 gene into HaCaT cells to investigate whether HPV infection could affect the expression of PD-L1. The successfully constructed HPV11-E7 HaCaT cells were cocultured with Jurkat cells, and Jurkat cell apoptosis and proliferation as well as the Jurkat cell cycle were evaluated by flow cytometry and cell counting kit-8 (CCK-8) assays.

RESULTS

PD-L1 was highly expressed in keratinocytes of genital warts. Through the construction of a cell model, we found that HPV11-E7 could upregulate the expression of PD-L1 in HaCaT cells. Furthermore, HPV11-E7 HaCaT cells can promote the apoptosis of Jurkat cells, inhibit the proliferation of Jurkat cells and mediate the cell cycle arrest of Jurkat cells through the PD-1/PD-L1 signalling pathway.

CONCLUSIONS

HPV infection may upregulate PD-L1 expression in the keratinocytes of genital warts and participate in the inhibition of local T-cell function.

Hepatitis C Virus and the Host: A Mutual Endurance Leaving Indelible Scars in the Host's Immunity

Hepatitis C virus (HCV) has spread worldwide, and it is responsible for potentially severe chronic liver disease and primary liver cancer. Chronic infection remains for life if not spontaneously eliminated and viral persistence profoundly impairs the efficiency of the host's immunity. Attempts have been made to develop an effective vaccine, but efficacy trials have met with failure. The availability of highly efficacious direct-acting antivirals (DAA) has created hope for the progressive elimination of chronic HCV infections; however, this approach requires a monumental global effort. HCV elicits a prompt innate immune response in the host, characterized by a robust production of interferon-α (IFN-α), although interference in IFN-α signaling by HCV proteins may curb this effect. The late appearance of largely ineffective neutralizing antibodies and the progressive exhaustion of T cells, particularly CD8 T cells, result in the inability to eradicate the virus in most infected patients. Moreover, an HCV cure resulting from DAA treatment does not completely restore the normal immunologic homeostasis. Here, we discuss the main immunological features of immune responses to HCV and the epigenetic scars that chronic viral persistence leaves behind.

Subpopulation composition of blood T-killers in patients with hepatitis C with genotype 1 or 3

Introduction. Despite great attention to the pathogenesis of chronic viral hepatitis C (CVHC), many aspects of the immune response in this pathology remain unclear. Aim. To study the subpopulation composition of blood cytotoxic T cells by flow cytometry, depending on the severity of clinical and morphological manifestations of CVHC with genotype 1 or 3. Materials and methods. Clinical, laboratory examinations, determination of liver fibrosis by elastometry using the METAVIR scale and study of the subpopulation composition of cytotoxic T cells in the blood were carried out in 144 patients with CVHC, including 74 patients with genotype 1 and 70 individuals with genotype 3, and in 20 people of the control group. The study of the subpopulation composition of cytotoxic T cells in the blood was carried out on a flow cytometer Navios (Beckman Coulter, USA) with the determination of CD3, CD8, CD45R0 and CD62L markers. Results. Changes in the subpopulation composition of blood cytotoxic T cells were more associated with the severity of liver fibrosis in patients with 1 and 3 genotypes of CVHC, than with inflammatory activity and viral load. In patients with CVHC genotype 3, a marked decrease in the content of TEMRA T-cytotoxic cells (CD3+ CD8+ CD45R0–CD62L–) and effector memory T-cytotoxic cells (CD3+ CD8+ CD45R0+ CD62L–) was registered in patients with METAVIR liver fibrosis stage F3-F4 in comparison with persons with METAVIR liver fibrosis stage F0-F1 (Kruskal-Wallis test, respectively, p = 0.02 and p = 0.04 In persons with CVHC genotype 1, similar associations were expressed to a lesser extent.Conclusion. We obtained an association of deterioration in the indices of the blood cytotoxic T cells subpopulation in patients with CVHC with an increase in the severity of liver fibrosis, which had some differences in patients with genotypes 1 and 3.

Molecular characterization of immunoinhibitory factors PD-1/PD-L1 in sheep

Sheep have been used as a large animal experimental model for studying infectious diseases. However, due to a lack of staining antibodies and reagents, immunological studies on sheep have not progressed. The immunoinhibitory receptor programmed death-1 (PD-1) is expressed on T lymphocytes. The interaction of PD-1 with its ligand PD-ligand 1 (PD-L1) delivers inhibitory signals and impairs proliferation, cytokine production, and cytotoxicity of T cells. We previously reported that the PD-1/PD-L1 pathway was closely associated with T-cell exhaustion and disease progression in bovine chronic infections using anti-bovine PD-L1 monoclonal antibodies (mAbs). Furthermore, we found that blocking antibodies against PD-1 and PD-L1 restore T-cell functions and could be used in immunotherapy of cattle. However, the immunological role of the PD-1/PD-L1 pathway in chronic diseases of sheep remains unknown. In this study, we identified cDNA sequences of ovine PD-1 and PD-L1 and examined the cross-activity of anti-bovine PD-L1 mAbs against ovine PD-L1 as well as the expression of PD-L1 in ovine listeriosis. The amino acid sequences of ovine PD-1 and PD-L1 share a high degree of identity and similarity with homologs from ruminants and other mammalian species. Anti-bovine PD-L1 mAb recognized ovine PD-L1 on lymphocytes in the flow cytometric assay. Furthermore, an immunohistochemical staining confirmed the PD-L1 expression on macrophages in the brain lesions of ovine listeriosis. These findings indicated that our anti-PD-L1 mAb would be useful for analyzing the ovine PD-1/PD-L1 pathway. Further research is needed to determine the immunological role of PD-1/PD-L1 in chronic diseases such as BLV infection through experimental infection of sheep.

Lnc-AIFM2-1 promotes HBV immune escape by acting as a ceRNA for miR-330-3p to regulate CD244 expression

Chronic hepatitis B (CHB) virus infection is a major risk factor for cirrhosis and hepatocellular carcinoma (HCC). Hepatitis B virus (HBV) immune escape is regulated by the exhaustion of virus-specific CD8+ T cells, which is associated with abnormal expression of negative regulatory molecule CD244. However, the underlying mechanisms are unclear. To investigate the important roles of non-coding RNAs play in CD244 regulating HBV immune escape, we performed microarray analysis to determine the differential expression profiles of long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and mRNAs in patients with CHB and patients with spontaneous clearance of HBV. Competing endogenous RNA (ceRNA) was analyzed by bioinformatics methods and confirmed by the dual-luciferase reporter assay. Furthermore, gene silencing and overexpression experiments were used to further identify the roles of lncRNA and miRNA in HBV immune escape through CD244 regulation. The results showed that the expression of CD244 on the surface of CD8+ T cells was significantly increased in CHB patients and in the co-culture system of T cells and HBV-infected HepAD38 cells, which was accompanied by the reduction of miR-330-3p and the elevation of lnc-AIFM2-1. The down-regulated miR-330-3p induced the apoptosis of T cells by lifting the inhibition of CD244, which was reversed by miR-330-3p mimic or CD244-siRNA. Lnc-AIFM2-1 promotes the accumulation of CD244, which is mediated by decreased miR-330-3p, and then reduced the clearance ability of CD8+ T cells to HBV through regulated CD244 expression. And the injury in the ability of CD8+ T cells to clear HBV can be reversed by lnc-AIFM2-1-siRNA, miR-330-3p mimic, or CD244-siRNA. Collectively, our findings indicate that lnc-AIFM2-1 on CD244 by acting as a ceRNA of miR-330-3p contributes to HBV immune escape, which may provide novel insights into the roles of interaction networks among lncRNA, miRNA, and mRNA in HBV immune escape, highlighting potential applications of lnc-AIFM2-1 and CD244 for diagnosis and treatment in CHB.

Hepatitis C virus-specific immune responses following direct-acting antivirals administered during recent hepatitis C virus infection

Individuals who spontaneously clear hepatitis C virus (HCV) infection have demonstrated evidence of partial protective immunity, whereas treatment-induced clearance provides little or no protection against reinfection. We aimed to investigate whether treatment of acute HCV infection with direct-acting antivirals (DAA) prevents establishment of, or reverses, T-cell exhaustion, leading to a virus-specific T-cell immune profile more similar to that seen in spontaneous clearance. The magnitude and breadth of HCV-specific T-cell responses before and after DAA or interferon-based therapy in acute or chronic HCV were compared to those of participants with spontaneous clearance of infection, using Enzyme-linked Immunospot (ELISPOT). PBMCs were available for 55 patients comprising 4 groups: spontaneous clearance (n = 17), acute interferon (n = 14), acute DAA (n = 13) and chronic DAA (n = 11). After controlling for sex, the magnitude of post-treatment HCV-specific responses after acute DAA treatment was greater than after chronic DAA or acute IFN treatment and similar to those found in spontaneous clearers. However, spontaneous clearers responded to more HCV peptide pools indicating greater breadth of response. In conclusion, early treatment with DAAs may prevent or reverse some degree of immune exhaustion and result in stronger HCV-specific responses post-treatment. However, individuals with spontaneous clearance had broader HCV-specific responses.

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

Background and Aims

During chronic hepatitis C virus (HCV) infection, CD8⁺ T-cells become functionally exhausted, undergoing progressive phenotypic changes, i.e., overexpression of “inhibitory” molecules such as PD-1 (programmed cell death protein 1) and/or Tim-3 (T-cell immunoglobulin and mucin domain-containing molecule-3). The extreme intrahost genetic diversity of HCV is a major mechanism of immune system evasion, facilitating epitope escape. The aim of the present study was to determine whether T-cell exhaustion phenotype in chronic HCV infection is related to the sequence repertoire of NS3 viral immunodominant epitopes.

Methods

The study population was ninety prospective patients with chronic HCV genotype 1b infection. Populations of peripheral blood CD8⁺ T-cells expressing PD-1/Tim-3 were assessed by multiparametric flow cytometry, including HCV-specific T-cells after magnetic-based enrichment using MHC-pentamer. Autologous epitope sequences were inferred from next-generation sequencing. The correction of sequencing errors and genetic variants reconstruction was performed using Quasirecomb.

Results

There was an interplay between the analyzed epitopes sequences and exhaustion phenotype of CD8⁺ T-cells. A predominance of NS3₁₄₀₆ epitope sequence, representing neither prototype KLSGLGLNAV nor cross-reactive variants (KLSSLGLNAV, KLSGLGINAV or KLSALGLNAV), was associated with higher percentage of HCV-specific CD8⁺PD-1⁺Tim-3⁺ T-cells, P=0.0102. Variability (at least two variants) of NS3₁₄₀₆ epitope sequence was associated with increased frequencies of global CD8⁺PD-1⁺Tim-3⁺ T-cells (P=0.0197) and lower frequencies of CD8⁺PD-1⁻Tim-3⁻ T-cells (P=0.0079). In contrast, infection with NS3₁₀₇₃ dominant variant epitope (other than prototype CVNGVCWTV) was associated with lower frequency of global CD8⁺PD-1⁺Tim-3⁺ T-cells (P=0.0054).

Conclusions

Our results indicate that PD-1/Tim-3 receptor expression is largely determined by viral epitope sequence and is evident for both HCV-specific and global CD8⁺ T-cells, pointing to the importance of evaluating autologous viral epitope sequences in the investigation of CD8⁺ T-cell exhaustion in HCV infection.

Knowns and Unknowns about CAR-T Cell Dysfunction

Immunotherapy using chimeric antigen receptor (CAR) T cells is a promising option for cancer treatment. However, T cells and CAR-T cells frequently become dysfunctional in cancer, where numerous evasion mechanisms impair antitumor immunity. Cancer frequently exploits intrinsic T cell dysfunction mechanisms that evolved for the purpose of defending against autoimmunity. T cell exhaustion is the most studied type of T cell dysfunction. It is characterized by impaired proliferation and cytokine secretion and is often misdefined solely by the expression of the inhibitory receptors. Another type of dysfunction is T cell senescence, which occurs when T cells permanently arrest their cell cycle and proliferation while retaining cytotoxic capability. The first section of this review provides a broad overview of T cell dysfunctional states, including exhaustion and senescence; the second section is focused on the impact of T cell dysfunction on the CAR-T therapeutic potential. Finally, we discuss the recent efforts to mitigate CAR-T cell exhaustion, with an emphasis on epigenetic and transcriptional modulation.

Chronic Hepatitis C Pathogenesis: Immune Response in the Liver Microenvironment and Peripheral Compartment

Chronic hepatitis C (CHC) pathogenic mechanisms as well as the participation of the immune response in the generation of liver damage are still a topic of interest. Here, we evaluated immune cell populations and cytokines in the liver and peripheral blood (PB) to elucidate their role in CHC pathogenesis. B, CTL, Th, Treg, Th1, Th17, and NK cell localization and frequency were evaluated on liver biopsies by immunohistochemistry, while frequency, differentiation, and functional status on PB were evaluated by flow cytometry. TNF-α, IL-23, IFN-γ, IL-1β, IL-6, IL-8, IL-17A, IL-21, IL-10, and TGF-β expression levels were quantified in fresh liver biopsy by RT-qPCR and in plasma by CBA/ELISA. Liver CTL and Th1 at the lobular area inversely correlated with viral load (r = −0.469, p =0.003 and r = −0.384, p = 0.040). Treg correlated with CTL and Th1 at the lobular area (r = 0.784, p < 0.0001; r = 0.436, p = 0.013). Th17 correlated with hepatic IL-8 (r = 0.52, p < 0.05), and both were higher in advanced fibrosis cases (Th17 p = 0.0312, IL-8 p = 0.009). Hepatic cytokines were higher in severe hepatitis cases (IL-1β p = 0.026, IL-23 p = 0.031, IL-8 p = 0.002, TGF-β, p= 0.037). Peripheral NK (p = 0.008) and NK dim (p = 0.018) were diminished, while NK bright (p = 0.025) was elevated in patients vs. donors. Naïve Th (p = 0.011) and CTL (p = 0.0007) were decreased, while activated Th (p = 0.0007) and CTL (p = 0.0003) were increased. IFN-γ production and degranulation activity in NK and CTL were normal. Peripheral cytokines showed an altered profile vs. donors, particularly elevated IL-6 (p = 0.008) and TGF-β (p = 0.041). Total hepatic CTLs favored damage. Treg could not prevent fibrogenesis triggered by Th17 and IL-8. Peripheral T-lymphocyte differentiation stage shift, elevated cytokine levels and NK-cell count decrease would contribute to global disease.

Natural Killer Cells and T Cells in Hepatocellular Carcinoma and Viral Hepatitis: Current Status and Perspectives for Future Immunotherapeutic Approaches

Natural killer (NK) cells account for 25–50% of the total number of hepatic lymphocytes, which implicates that NK cells play an important role in liver immunity. The frequencies of both circulating and tumor infiltrating NK cells are positively correlated with survival benefit in hepatocellular cancer (HCC) and have prognostic implications, which suggests that functional impairment in NK cells and HCC progression are strongly associated. In HCC, T cell exhaustion is accompanied by the interaction between immune checkpoint ligands and their receptors on tumor cells and antigen presenting cells (APC). Immune checkpoint inhibitors (ICIs) have been shown to interfere with this interaction and have altered the therapeutic landscape of multiple cancer types including HCC. Immunotherapy with check-point inhibitors, aimed at rescuing T-cells from exhaustion, has been applied as first-line therapy for HCC. NK cells are the first line effectors in viral hepatitis and play an important role by directly eliminating virus infected cells or by activating antigen specific T cells through IFN-γ production. Furthermore, chimeric antigen receptor (CAR)-engineered NK cells and T cells offer unique opportunities to create CAR-NK with multiple specificities learning from the experience gained with CAR-T cells with potentially less adverse effects. This review focus on the abnormalities of NK cells, T cells, and their functional impairment in patients with chronic viral hepatitis, which contributes to progression to hepatic malignancy. Furthermore, we discuss and summarize recent advances in the NK cell and T cell based immunotherapeutic approaches in HCC.

Selective downregulation of natural killer activating receptors on NK cells and upregulation of PD-1 expression on T cells in children with severe and/or recurrent Herpes simplex virus infections

Severe, recurrent or atypical Herpes simplex virus (HSV) infections are still posing clinical and diagnostic problem in clinical immunology facilities. However, the molecular background of this disorder is still unclear. The aim of this study was to investigate the expression of activating receptors on NK cells (CD16, NKp46, NKG2D, NKp80, 2B4, CD48 and NTB-A) and checkpoint molecule PD-1 on T lymphocytes and NK cells, in patients with severe and/or recurrent infections with HSV and age-matched healthy control subjects. As a result, we noticed that patients with severe and/or recurrent infection with HSV had significantly lower percentage of CD16^brightCD56^dim and higher percentage of CD16^dimCD56^bright NK cell subsets, when compared to control subjects, which may be associated with abnormal NK cell maturation during chronic HSV infection. Patients had also significantly downregulated expression of CD16 receptor on CD16^bright NK cells. The expression of activating receptors was significantly reduced on patients' NK cells - either both the percentage of NK cells expressing the receptor and MFI of its expression (NKp46, NKp80 and 2B4 on CD16^brightCD56^dim cells and NKp46 on CD16^dimCD56^bright cells) or only MFI (NKG2D on both NK cell subsets). It should be noted that the reduction of receptor expression was limited to NK cells, since there was no differences in the percentage of receptor-positive cells or MFI on T cells. However, NTB-A receptor was the only one which expression was not only simultaneously changed in patients' NK and T cells, but also significantly upregulated on CD16^dimCD56^bright NK cell and CD8⁺ cell subsets. Patients had also upregulated proportion of CD4⁺ T cells expressing PD-1. Thus, we suggest that an increased percentage of PD-1⁺ cells may represent an independent indirect mechanism of downregulation of antiviral response, separate from the reduction of NK cell activating receptors expression. Altogether, our studies indicate two possible mechanisms which may promote perpetuation of HSV infection: 1) selective inhibition of activating receptors on NK cells, but not on T cells, and 2) upregulation of checkpoint molecule PD-1 on CD4⁺ T cells.

A juggernaut of innate & adaptive immune cells in chronic hepatitis C

Hepatitis C virus (HCV) is a small positive-sense, single-stranded RNA virus, the causal organism for chronic hepatitis. Chronic hepatitis leads to inflammation of liver, causing cirrhosis, fibrosis and steatosis, which may ultimately lead to liver cancer in a few cases. Innate and adaptive immune responses play an important role in the pathogenesis of HCV infection, thus acting as an important component in deciding the fate of the disease. Numerous studies have indicated that the derangement of these immune responses results in the persistence of infection leading to chronic state of the disease. Interactions between virus and host immune system generally result in the elimination of virus, but as the virus evolves with different evading mechanisms, it makes environment favourable for its survival and replication. It has been reported that HCV impairs the immune system by functional modulation of the cells of innate as well as adaptive immune responses, resulting in chronic state of the disease, influencing the response to antiviral therapy in these patients. These defects in the immune system lead to suboptimal immune responses and therefore, impaired effector functions. This review highlights the involvement or association of different immune cells such as natural killer cells, B cells, dendritic cells and T cells in HCV infection and how the virus plays a role in manipulating certain regulatory mechanisms to make these cells dysfunctional for its own persistence and survival.

Gamma-Chain Receptor Cytokines & PD-1 Manipulation to Restore HCV-Specific CD8+ T Cell Response during Chronic Hepatitis C

Hepatitis C virus (HCV)-specific CD8⁺ T cell response is essential in natural HCV infection control, but it becomes exhausted during persistent infection. Nowadays, chronic HCV infection can be resolved by direct acting anti-viral treatment, but there are still some non-responders that could benefit from CD8⁺ T cell response restoration. To become fully reactive, T cell needs the complete release of T cell receptor (TCR) signalling but, during exhaustion this is blocked by the PD-1 effect on CD28 triggering. The T cell pool sensitive to PD-1 modulation is the progenitor subset but not the terminally differentiated effector population. Nevertheless, the blockade of PD-1/PD-L1 checkpoint cannot be always enough to restore this pool. This is due to the HCV ability to impair other co-stimulatory mechanisms and metabolic pathways and to induce a pro-apoptotic state besides the TCR signalling impairment. In this sense, gamma-chain receptor cytokines involved in memory generation and maintenance, such as low-level IL-2, IL-7, IL-15, and IL-21, might carry out a positive effect on metabolic reprogramming, apoptosis blockade and restoration of co-stimulatory signalling. This review sheds light on the role of combinatory immunotherapeutic strategies to restore a reactive anti-HCV T cell response based on the mixture of PD-1 blocking plus IL-2/IL-7/IL-15/IL-21 treatment.

T cell immunity to hepatitis C virus: Lessons for a prophylactic vaccine

There is consensus that HCV-specific T cells play a central role in the outcome (clearance vs. persistence) of acute infection and that they contribute to protection against the establishment of persistence after reinfection. However, these T cells often fail and the virus can persist, largely as a result of T cell exhaustion and the emergence of viral escape mutations. Importantly, HCV cure by direct-acting antivirals does not lead to a complete reversion of T cell exhaustion and thus HCV reinfections can occur. The current lack of detailed knowledge about the immunological determinants of viral clearance, persistence and protective immunity is a major roadblock to the development of a prophylactic T cell vaccine. This minireview highlights the basic concepts of successful T cell immunity, major mechanisms of T cell failure and how our understanding of these concepts can be translated into a prophylactic vaccine.

T-Cell Immunity against the Hepatitis C Virus: A Persistent Research Priority in an Era of Highly Effective Therapy

Approximately 70% of acute hepatitis C virus (HCV) infections become chronic, indicating that the virus is exceptionally well adapted to persist in humans with otherwise normal immune function. Robust, lifelong replication of this small RNA virus does not require a generalized failure of immunity. HCV effectively subverts innate and adaptive host defenses while leaving immunity against other viruses intact. Here, the role of CD4⁺ and CD8⁺ T-cell responses in control of HCV infection and their failure to prevent virus persistence in most individuals are reviewed. Two issues of practical importance remain priorities in an era of highly effective antiviral therapy for chronic hepatitis C. First, the characteristics of successful T-cell responses that promote resolution of HCV infection are considered, as they will underpin development of vaccines that prevent HCV persistence. Second, defects in T-cell immunity that facilitate HCV persistence and whether they are reversed after antiviral cure to provide protection from reinfection are also addressed.

PDCD1 and IFNL4 genetic variants and risk of developing hepatitis C virus-related diseases

BACKGROUND

Genetic variants of IFNL4 and PDCD1 genes have been shown to influence the spontaneous clearance of hepatitis C virus (HCV) infection. We investigated the IFNL4 rs12979860 and the PDCD1 polymorphisms in 734 HCV-positive patients, including 461 cases with liver disease of varying severity and 273 patients with lymphoproliferative disorders to determine the association of these genes with patient's outcome.

METHODS

Expression levels of PDCD1 mRNA encoded by haplotypes were investigated by quantitative PCR in hepatocellular carcinoma (HCC) tissue and peripheral blood mononuclear cells. Flow cytometry was used to detect PD-1 and its ligand PD-L1.

RESULTS

The frequency of IFNL4 rs12979860 C/T or T/T genotypes was significantly higher in patients with HCV-related diseases than blood donors (P < .0001). Patients expressing the IFNλ4 variant with one amino acid change that reduces IFNλ4 secretion was found increased in frequency in HCV-related diseases compared to HCC PDCD1 mRNA levels in HCC tissue were significantly higher in cases carrying the PD-1.3 A or the PD-1.7 G allele (P = .0025 and P = .0167). Linkage disequilibrium (LD) between PD-1.3 and IFNL4 was found in patients with mixed cryoglobulinaemia (MC) only (LD = 0 in HCC; LD = 72 in MC). PBMCs of MC patients expressed low levels of PD-L1 in CD19+IgM+B cells and of PD-1 in CD4+T cells suggesting the involvement of regulatory B cell-T cell interaction to the pathogenesis of MC.

CONCLUSION

Collectively, our data indicate an important contribution of IFNλ4 expression to the development of HCV-related HCC and an epistatic contribution of IFNL4 and PDCD1 in MC.

LAY SUMMARY

Studies of IFNL4 and PDCD1 genes are helpful to better understand the role of host genetic factors and immune antigens influencing the outcome of HCV-related diseases. Our data support an association between the expression of IFNλ4, which prevents the expression of IFNλ3, with all the different HCV-related diseases studied, and besides, evidence that a higher IFNλ4 expression is associated with hepatocellular at a younger age. The expression pattern of low PD-L1 on B cells and high PD-1 on CD4+T-cells in patients with HCV-positive cryoglobulinaemia suggests a critical role of the PD-1/PD-L1 signaling in modulating B cell-T cell interaction in this lymphoproliferative disease.

Chronic genotype 1 hepatitis C along with cirrhosis drives a persistent imprint in virus-specific CD8+ T cells after direct-acting antiviral therapies

Chronic hepatitis C virus (HCV) infection impairs HCV CD8⁺ T-cell responses, while it could influence immune responses towards unrelated viruses/vaccines (e.g. cytomegalovirus, CMV, and influenza, Flu). The aim of our study was to delineate whether restoration of these virus-specific CD8⁺ T cells occurs after direct-acting antiviral (DAA) therapies and particularly in patients with cirrhosis. We performed longitudinal analysis (baseline, week 4, follow-up [FU] 12 and FU48) of virus-specific CD8⁺ T cells by multicolour flow cytometry in HCV-cirrhotic patients undergoing DAA therapy (n = 26) after in vitro expansion with immunodominant HCV, CMV and Flu epitopes restricted by HLA-A*02. HCV noncirrhotic patients (n = 9) and healthy individuals (n = 10) served as controls. We found that the proliferative capacity of HCV-specific CD8⁺ T cells increased from baseline up to FU48 in a significant proportion of cirrhotic and noncirrhotic patients. Nevertheless, these cells remained poor cytokine producers in both patient groups, regardless of the down-regulation of inhibitory co-regulatory receptors in HCV-cirrhotic patients at FU48. Likewise, high expression levels of these exhaustion markers were detected in CMV-/Flu-specific CD8⁺ T cells in HCV-cirrhotic patients at all time points, albeit without affecting their proliferative capacity or cytokine production. We conclude that DAA therapies induce restoration of the proliferative capacity of HCV-specific CD8⁺ T cells. However, these cells remain phenotypically and functionally impaired. Contrarily, the 'exhausted' phenotype in CMV-/Flu-specific CD8⁺ T cells in HCV-cirrhotic patients did not associate with their functions. Larger studier with longer follow-up may elucidate whether this complex interplay influences the outcome of cirrhotic patients.

Pathogenesis of Viral Hepatitis-Induced Chronic Liver Disease: Role of Extracellular Vesicles

Extracellular vesicles are encapsulated lipid nanoparticles secreted by a variety of cell types in living organisms. They are known to carry proteins, metabolites, nucleic acids, and lipids as their cargoes and are important mediators of intercellular communication. The role of extracellular vesicles in chronic liver disease has been reported. Chronic liver disease such as viral hepatitis accounts for a significant mortality and morbidity burden worldwide. Hepatic fibrosis has been commonly associated with the chronic form of viral hepatitis, which results in end-stage liver disease, including cirrhosis, liver failure, and carcinoma in some patients. In this review, we discuss the potential role of extracellular vesicles in mediating communication between infectious agents (hepatitis B and C viruses) and host cells, and how these complex cell-cell interactions may facilitate the development of chronic liver disease. We will further discuss how understanding their biological mechanism of action might be beneficial for developing therapeutic strategies to treat chronic liver disease.

Lymphocyte Landscape after Chronic Hepatitis C Virus (HCV) Cure: The New Normal

Chronic HCV (CHC) infection is the only chronic viral infection for which curative treatments have been discovered. These direct acting antiviral (DAA) agents target specific steps in the viral replication cycle with remarkable efficacy and result in sustained virologic response (SVR) or cure in high (>95%) proportions of patients. These treatments became available 6–7 years ago and it is estimated that their real impact on HCV related morbidity, including outcomes such as cirrhosis and hepatocellular carcinoma (HCC), will not be known for the next decade or so. The immune system of a chronically infected patient is severely dysregulated and questions remain regarding the immune system’s capacity in limiting liver pathology in a cured individual. Another important consequence of impaired immunity in patients cleared of HCV with DAA will be the inability to generate protective immunity against possible re-infection, necessitating retreatments or developing a prophylactic vaccine. Thus, the impact of viral clearance on restoring immune homeostasis is being investigated by many groups. Among the important questions that need to be answered are how much the immune system normalizes with cure, how long after viral clearance this recalibration occurs, what are the consequences of persisting immune defects for protection from re-infection in vulnerable populations, and does viral clearance reduce liver pathology and the risk of developing hepatocellular carcinoma in individuals cured with these agents. Here, we review the recent literature that describes the defects present in various lymphocyte populations in a CHC patient and their status after viral clearance using DAA treatments.

Immune Checkpoint Inhibitors versus VEGF Targeted Therapy as Second Line Regimen in Advanced Hepatocellular Carcinoma (HCC): A Retrospective Study

Several targeted agents including multi-tyrosine kinase inhibitors (mTKIs) and immunotherapy (IO) agents have been approved for use beyond the frontline setting in patients with advanced hepatocellular carcinoma (HCC). Due to lack of prospective head-to-head comparative trials, there is no standardized way for alternating those agents beyond frontline. Therefore, we performed a retrospective review of the Kansas University (KU) cancer registry to determine whether IO may be superior to non-IO therapy. Patients with advanced HCC were divided into two groups based on the second-line systemic regimen received (IO vs. non-IO). Progression-free survival (PFS) and overall survival (OS) were calculated under the Kaplan-Meier and Cox proportional hazards models. No statistically significant differences in PFS and OS were found, although a non-significant delayed separation in the survival curve favoring IO was identified (median PFS 3.9 months vs. 3 months; median OS 10 months vs. 10 months respectively for IO vs. non-IO). This retrospective analysis is one of the earliest and largest studies comparing second-line IO and non-IO therapies thus far reported. Future studies should aim to define specific biomarkers for response prediction and treatment optimization based on individual patient and tumor characteristics. Furthermore, combinatorial therapeutic strategies is an evolving approach showing early promising signal.

Reversal of T Cell Exhaustion in Chronic HCV Infection

The long-term consequences of T cell responses’ impairment in chronic HCV infection are not entirely characterized, although they may be essential in the context of the clinical course of infection, re-infection, treatment-mediated viral clearance and vaccine design. Furthermore, it is unclear whether a complete reinvigoration of HCV-specific T cell response may be feasible. In most studies, attempting to reverse the effects of compromised immune response quality by specific blockades of negative immune regulators, a restoration of functional competence of HCV-specific T cells was shown. This implies that HCV-induced immune dysfunction may be reversible. The advent of highly successful, direct-acting antiviral treatment (DAA) for chronic HCV infection instigated investigation whether the treatment-driven elimination of viral antigens restores T cell function. Most of studies demonstrated that DAA treatment may result in at least partial restoration of T cell immune function. They also suggest that a complete restoration comparable to that seen after spontaneous viral clearance may not be attained, pointing out that long-term antigenic stimulation imprints an irreversible change on the T cell compartment. Understanding the mechanisms of HCV-induced immune dysfunction and barriers to immune restoration following viral clearance is of utmost importance to diminish the possible long-term consequences of chronic HCV infection.

Fatty acid-driven modifications in T-cell profiles in non-alcoholic fatty liver disease patients

BACKGROUND

The interaction between T-cells/fatty acids involved in non-alcoholic fatty liver disease (NAFLD) and liver fibrosis progression is poorly understood. In this study, we conducted a comprehensive analysis of T-cell profiles of NAFLD patients to better understand their relationship with fatty acids and relevance to liver fibrosis.

METHODS

We analyzed the differences in T-cell profiles of peripheral blood mononuclear cells (PBMCs) between 40 NAFLD patients and 5 healthy volunteers (HVs), and their relationship with liver fibrosis stage or progression. Moreover, we analyzed the relationship between T-cell profiles and fatty acid compositions in vivo, and changes in T-cell profiles after treatment with fatty acids in vitro.

RESULTS

T-cell profiles of NAFLD patients were different from those of HVs. The CD25⁺CD45⁺CD4⁺ T-cell frequency was increased in NAFLD patients with high liver fibrosis stage and progression, and this indicated immune activation. Despite such a state of immune activation, the PD1⁺CD4⁺ T-cell frequency was decreased in the same patients group. The PD1⁺CD4⁺ T-cell frequency had a significantly negative correlation with the serum fatty acid composition ratio C16:1n7/C16:0. Moreover, the PD1⁺CD4⁺ T-cell frequency was significantly decreased by in vitro treatment with fatty acids. In addition, its rate of frequency change was significantly different between C16:0 and C16:1n7 and decreased by artificially increasing the C16:1n7/C16:0 ratio.

CONCLUSIONS

The analysis of PBMCs in NAFLD patients showed that T-cell profiles were different from those of HVs. And, it suggested that fatty acids modified T-cell profiles and were involved in liver fibrosis in NAFLD patients.

Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment

Hepatitis C virus (HCV) infection is the major risk factor for liver cirrhosis and hepatocellular carcinoma (HCC). The mechanisms of HCC initiation, growth, and metastasis appear to be highly complex due to the decade-long interactions between the virus, immune system, and overlapping bystander effects of host metabolic liver disease. The lack of a readily accessible animal model system for HCV is a significant obstacle to understand the mechanisms of viral carcinogenesis. Traditionally, the primary prevention strategy of HCC has been to eliminate infection by antiviral therapy. The success of virus elimination by antiviral treatment is determined by the SVR when the HCV is no longer detectable in serum. Interferon-alpha (IFN-α) and its analogs, pegylated IFN-α (PEG-IFN-α) alone with ribavirin (RBV), have been the primary antiviral treatment of HCV for many years with a low cure rate. The cloning and sequencing of HCV have allowed the development of cell culture models, which accelerated antiviral drug discovery. It resulted in the selection of highly effective direct-acting antiviral (DAA)-based combination therapy that now offers incredible success in curing HCV infection in more than 95% of all patients, including those with cirrhosis. However, several emerging recent publications claim that patients who have liver cirrhosis at the time of DAAs treatment face the risk of HCC occurrence and recurrence after viral cure. This remains a substantial challenge while addressing the long-term benefit of antiviral medicine. The host-related mechanisms that drive the risk of HCC in the absence of the virus are unknown. This review describes the multifaceted mechanisms that create a tumorigenic environment during chronic HCV infection. In addition to the potential oncogenic programming that drives HCC after viral clearance by DAAs, the current status of a biomarker development for early prediction of cirrhosis regression and HCC detection post viral treatment is discussed. Since DAAs treatment does not provide full protection against reinfection or viral transmission to other individuals, the recent studies for a vaccine development are also reviewed.

Targeting p53 and histone methyltransferases restores exhausted CD8+ T cells in HCV infection

Hepatitis C virus infection (HCV) represents a unique model to characterize, from early to late stages of infection, the T cell differentiation process leading to exhaustion of human CD8+ T cells. Here we show that in early HCV infection, exhaustion-committed virus-specific CD8+ T cells display a marked upregulation of transcription associated with impaired glycolytic and mitochondrial functions, that are linked to enhanced ataxia-telangiectasia mutated (ATM) and p53 signaling. After evolution to chronic infection, exhaustion of HCV-specific T cell responses is instead characterized by a broad gene downregulation associated with a wide metabolic and anti-viral function impairment, which can be rescued by histone methyltransferase inhibitors. These results have implications not only for treatment of HCV-positive patients not responding to last-generation antivirals, but also for other chronic pathologies associated with T cell dysfunction, including cancer.

Use of Mass Cytometry to Profile Human T Cell Exhaustion

Mass cytometry has become an important technique for the deep analysis of single cell protein expression required for precision systems immunology. The ability to profile more than 40 markers per cell is particularly relevant for the differentiation of cell types for which low parametric characterization has proven difficult, such as exhausted CD8⁺ T cells (T_EX). T_EX with limited effector function accumulate in many chronic infections and cancers and are subject to inhibitory signaling mediated by several immune checkpoints (e.g., PD-1). Of note, T_EX represent considerable targets for immune-stimulatory therapies and are beginning to be recognized as a major correlate of successful checkpoint blockade approaches targeting the PD-1 pathway. T_EX exhibit substantial functional, transcriptomic and epigenomic differences compared to canonical functional T cell subsets [such as naïve (T_N), effector (T_EFF) and memory T cells (T_MEM)]. However, phenotypic distinction of T_EX from T_EFF and T_MEM can often be challenging since many molecules expressed by T_EX can also be expressed by effector and memory T cell populations. Moreover, significant heterogeneity of T_EX has been described, such as subpopulations of exhausted T cells with progenitor-progeny relationships or populations with different degrees of exhaustion or homeostatic potential that may directly inform about disease progression. In addition, T_EX subsets have essential clinical implications as they differentially respond to antiviral and checkpoint therapies. The precise assessment of T_EX thus requires a high-parametric analysis that accounts for differences to canonical T cell populations as well as for T_EX subset heterogeneity. In this review, we discuss how mass cytometry can be used to reveal the role of T_EX subsets in humans by combining exhaustion-directed phenotyping with functional profiling. Mass cytometry analysis of human T_EX populations is instrumental to gain a better understanding of T_EX in chronic infections and cancer. It has important implications for immune monitoring in therapeutic settings aiming to boost T cell immunity, such as during cancer immunotherapy.

Hepatitis C Virus Affects Tuberculosis-Specific T Cells in HIV-Negative Patients

The occurrence of tuberculosis (TB) and hepatitis C virus (HCV) infections in the same patient presents a unique clinical challenge. The impact of HCV infection on the immune response to TB remains poorly investigated in TB⁺/HCV⁺ patients. This study was conducted to evaluate the impact of HCV on the T-cell-mediated immune response to TB in coinfected patients. Sixty-four patients with active TB infections were screened for coinfection with HCV. The expression of immune activation markers IFN-γ, CD38, and HLA-DR on TB-specific CD4⁺ T cells was evaluated by flow cytometry in TB-monoinfected patients, TB/HCV-coinfected patients, and healthy controls. IL-2, IL-4, IFN-γ, TNF-α, and IL-10 levels were measured using ELISA. The end-of-treatment response to anti-TB therapy was recorded for both patient groups. Significantly lower levels of CD4⁺IFN-γ⁺CD38⁺ and CD4⁺IFN-γ⁺HLA-DR⁺ T cells were detected in TB/HCV-coinfected patients compared to TB monoinfected patients and controls. TB⁺/HCV⁺-coinfected patients showed higher serum levels of IL-10. The baseline frequencies of TB-specific activated T-cell subsets did not predict the response to antituberculous therapy in TB⁺/HCV⁺ patients. We concluded that different subsets of TB-specific CD4⁺ T cells in TB/HCV-infected individuals are partially impaired in early-stage HCV infection. This was combined with increased serum IL-10 level. Such immune modulations may represent a powerful risk factor for disease progression in patients with HCV/TB coinfection.

Association between Hepatitis C Virus Viremia and the rs12979860, rs2228145 and rs1800795 SNP (CT/AC/GG) Genotype in Saudi Kidney Transplant Recipients

Background:

Hepatitis C virus (HCV) is a major health problem, particularly in high-risk groups such as kidney transplant recipients, where it can adversely affect graft survival and increase the relative risk for mortality. Recently, the role of genetic variation among HCV patients in determining the outcome of infections has been under investigation.

Objective:

To investigate the association of single-nucleotide polymorphisms (SNPs) rs12979860 (located within the interleukin-28B locus), rs2228145 (interleukin-6 receptor) and rs1800795 (interleukin-6 promoter) with HCV viremia in renal transplant patients.

Materials and Methods:

In this analytical cross-sectional study, 149 kidney transplant recipients, 82 males (median age: 41 years) and 67 females (median age: 45 years), were screened for HCV RNA in blood using real-time polymerase chain reaction and genotyped by sequencing (rs12979860) and restriction fragment length polymorphism (rs2228145 and rs1800795).

Results:

HCV RNA was detected in 17 (11.41%) of the 149 patients. There was no statistically significant association between the studied SNPs and HCV viremia. However, a combination of the CT/AC/GG genotype was significantly associated with HCV viremia (odds ratio: 5.4). The genotype AA of rs2228145 in the IL-6 receptor was associated with viremia levels of >10⁵ copies/ml (odds ratio: 5.96).

Conclusion:

To the best of the authors' knowledge, this is the first study that has shown that the CT/AC/GG genotype has an impact on HCV viremia in kidney transplant patients. Therefore, such SNP genotypes may potentially be used to identify transplant patients at risk of HCV infection.

Review article: immune checkpoint inhibitors and the liver, from therapeutic efficacy to side effects

BACKGROUND

Immune checkpoint inhibitors have revolutionised the oncological landscape in the last few years. Possible applications include the treatment of hepatocellular carcinoma and cholangiocarcinoma. Unfortunately, new immune-related adverse effects have been associated with the use of these agents and the liver is one of the organs most frequently involved.

AIMS

To provide a general overview of the potential impact of immune checkpoint inhibitors on the liver METHODS: We reviewed the literature and abstracts/presentations on immune checkpoint inhibitors at most relevant hepatology meetings over the last 5 years.

RESULTS

The role of immune checkpoint inhibitors has been investigated both for the treatment of viral hepatitis and primary liver cancer. Hepatocellular carcinoma and chronic hepatitis B show the greatest potential for treatment with these drugs in the near future. However, immune-related adverse events involving the liver are a growing concern related to their widespread use.

CONCLUSIONS

Immune checkpoint inhibitors represent an exciting new class of drugs with currently limited application in malignant and non-malignant liver disease. Caution must be exercised on the emergence of potentially severe immune adverse reactions.

Dynamic Changes in Ex Vivo T-Cell Function After Viral Clearance in Chronic HCV Infection

BACKGROUND

Direct-acting antiviral (DAA) agents can successfully treat chronic hepatitis C virus (HCV) infection. However, the ex vivo HCV-specific T-cell function following viral clearance remains unknown.

METHODS

We investigated functional alterations and phenotypic changes in ex vivo HCV-specific CD8+ T cells with a longitudinal analysis of 41 patients with chronic HCV infection who were undergoing DAA treatment.

RESULTS

A patient subset exhibited a significantly increased T-cell response (mainly CD8+ T cells) at week 4 of treatment. However, this increased T-cell response diminished in later weeks. Relative to pretreatment levels, the ex vivo HCV-specific CD8+ T-cell frequency decreased at 12 weeks after the end of treatment, along with a decreased antigen-experienced CD8+ T-cell population. DAA treatment increased the proliferative capacity of HCV-specific CD8+ T cells, but this change was not correlated with ex vivo function. Patients experiencing viral breakthrough or relapse exhibited defective restoration of T-cell function.

CONCLUSION

Our present results indicated that DAA-mediated viral clearance only transiently restored ex vivo T-cell function, suggesting a need to enhance T-cell function in DAA-treated patients.

Direct-Acting Antiviral Treatment of HCV Infection Does Not Resolve the Dysfunction of Circulating CD8+ T-Cells in Advanced Liver Disease

Chronic hepatitis C virus (HCV) infection disrupts immune functions, including that of cytotoxic CD8⁺ T-cells which are important mediators of immune response. While HCV cure aims to eliminate long term sequelae of infection, whether direct-acting antiviral (DAA) treatment results in immune reconstitution remains unclear. We and others have reported generalized CD8⁺ T-cell dysfunction in chronic HCV infection and our research suggests that the degree of liver damage is a factor in this process. Our recent research indicates that liver fibrosis is not readily reversed after DAA-mediated clearance of chronic HCV infection. We therefore examined the function of circulating CD8⁺ T-cell subsets in chronic HCV infection in the context of liver fibrosis severity, determined by ultrasound elastography and Metavir F-score system. We observed progressive shifts in CD8⁺ T-cell subset distribution in HCV-infected individuals with advanced liver fibrosis (F4) compared to minimal fibrosis (F0-1) or uninfected controls, and this remained unchanged after viral cure. Impaired CD8⁺ T-cell function was observed as a reduced proportion of CD107⁺ and perforin⁺ late effector memory cells in HCV⁺(F4) and HCV⁺(F0-1) individuals, respectively. In HCV⁺(F4) individuals, nearly all CD8⁺ T-cell subsets had an elevated proportion of perforin⁺ cells while naïve cells had increased proportions of IFN-γ⁺ and CD107⁺ cells. These exaggerated CD8⁺ T-cell activities were not resolved when evaluated 24 weeks after completion of DAA therapy and HCV clearance. This was further supported by sustained, high levels of cell proliferation and cytolytic activity. Furthermore, DAA therapy had no effect on elevated concentrations of systemic inflammatory cytokines and decreased levels of inhibitory TGF-β in the plasma of HCV⁺(F4) individuals, suggesting HCV infection and advanced liver disease result in a long-lasting immune activating microenvironment. These data demonstrate that in chronic HCV infection, liver fibrosis severity is associated with generalized hyperfunctional CD8⁺ T-cells, particularly with perforin production and cytotoxicity, and this persists after viral clearance. Whether DAA therapy will eliminate other related long-term sequelae in HCV⁺(F4) individuals remains an important research question.

Expression of programmed cell death protein 1 and T-cell immunoglobulin- and mucin-domain-containing molecule-3 on peripheral blood CD4+CD8+ double positive T cells in patients with chronic hepatitis C virus infection and in subjects who spontaneously cleared the virus

Chronic hepatitis C virus (HCV) infection is characterized by increased proportion of CD4+CD8+ double positive (DP) T cells, but their role in this infection is unclear. In chronic hepatitis C, immune responses to HCV become functionally exhausted, which manifests itself by increased expression of programmed cell death protein 1 (PD-1) and T-cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) on T cells. The aim of our study was to determine PD-1 and Tim-3 phenotype of DP T cells in subjects with naturally resolved and chronic HCV infection. Peripheral blood mononuclear cells from 16 patients with chronic infection and 14 subjects who cleared HCV in the past were stained with anti-CD3, anti-CD4, anti-CD8, anti-PD-1 and anti-Tim-3 antibodies and, in 12 HLA-A*02-positive subjects, MHC class I pentamer with HCV NS3₁₄₀₆ epitope. In chronic and past HCV infection, proportions of total DP T cells and PD-1+ DP T cells were similar but significantly higher than in healthy controls. DP T cells were more likely to be PD-1+ than either CD4+ or CD8+ single positive (SP) T cells. HCV-specific cells were present in higher proportions among DP T cells than among CD8+ SP T cells in both patient groups. Furthermore, while the majority of HCV-specific DP T cells were PD-1+, the proportion of HCV-specific CD8+ T cells which were PD-1+ was 4.9 and 1.9 times lower (chronic and past infection, respectively). PD-1 and Tim-3 were predominantly expressed on CD4^high CD8^low and CD4^low CD8^high cells, respectively, and co-expression of both markers was uncommon.

Peripheral PD-1+ T Cells Co-expressing Inhibitory Receptors Predict SVR With Ultra Short Duration DAA Therapy in HCV Infection

Direct acting antiviral (DAA) regimens of 12 weeks result in HCV clearance in vast majority of patients across genotypes. We previously demonstrated an ultra-short regimen of 4 weeks DAA cleared HCV in a subset of patients. Here, we hypothesized that individual level of antiviral immunity differentially influenced viral clearance and investigated biomarkers of a successful response. Cohorts of HCV patients treated for 4 weeks with DAA therapy who either achieved sustained virologic response (SVR) or relapsed were compared at baseline and at end of therapy (EOT) for immune cell phenotypes and HCV specific immunity. Higher levels of PD-1⁺ CD8⁺ and CD4⁺ T lymphocytes co-expressing inhibitory receptors (IR) were present at baseline and at EOT in HCV patients who eventually achieved SVR compared with those who relpased. HCV specific CD8⁺ T cells were predominantly contained within these IR expressing PD-1⁺ subsets. Patients in the SVR group had significantly higher CD8⁺ T cell degranulation in response to HCV peptides at baseline and higher levels of cytokine producing T cells at EOT time-point, relative to those who relapsed. In ex vivo cultures, PD-1⁺CD160⁺ CD8⁺ T cells had higher HCV specific degranulation and PD-1⁺2B4⁺ CD8⁺ T cells had higher cytokine expression (IFNγ⁺TNFα⁺ or IFNγ⁺CD107a⁺) compared with single or no IR expressing subsets, indicating higher virus specific functional capacity of these subsets. Receiver operating characteristics curve (ROC) for baseline circulating frequencies of PD-1⁺CD160⁺, PD-1⁺Tim-3⁺ CD8⁺ T cells and PD-1⁺CD160⁺, PD-1⁺Blimp-1⁺, PD-1^-CTLA4⁺ CD4⁺ T cells respectively, had associated C-statistics of 0.8214 and 0.9451 for discriminatin of patients who successfully cleared HCV with 4 weeks treatment. Thus, PD-1⁺ virus-specific CD8⁺ T cell subsets with cytotoxic capacity are present in a subset of chronic HCV infected individuals that associate with ability to achieve SVR, indicating role of immunity in DAA mediated viral clearance with short duration therapy.

Hepatitis C Virus Infection: Host⁻Virus Interaction and Mechanisms of Viral Persistence

Hepatitis C (HCV) is a major cause of liver disease, in which a third of individuals with chronic HCV infections may develop liver cirrhosis. In a chronic HCV infection, host immune factors along with the actions of HCV proteins that promote viral persistence and dysregulation of the immune system have an impact on immunopathogenesis of HCV-induced hepatitis. The genome of HCV encodes a single polyprotein, which is translated and processed into structural and nonstructural proteins. These HCV proteins are the target of the innate and adaptive immune system of the host. Retinoic acid-inducible gene-I (RIG-I)-like receptors and Toll-like receptors are the main pattern recognition receptors that recognize HCV pathogen-associated molecular patterns. This interaction results in a downstream cascade that generates antiviral cytokines including interferons. The cytolysis of HCV-infected hepatocytes is mediated by perforin and granzyme B secreted by cytotoxic T lymphocyte (CTL) and natural killer (NK) cells, whereas noncytolytic HCV clearance is mediated by interferon gamma (IFN-γ) secreted by CTL and NK cells. A host-HCV interaction determines whether the acute phase of an HCV infection will undergo complete resolution or progress to the development of viral persistence with a consequential progression to chronic HCV infection. Furthermore, these host-HCV interactions could pose a challenge to developing an HCV vaccine. This review will focus on the role of the innate and adaptive immunity in HCV infection, the failure of the immune response to clear an HCV infection, and the factors that promote viral persistence.

Restoration of HCV-Specific Immune Responses with Antiviral Therapy: A Case for DAA Treatment in Acute HCV Infection

Worldwide, 71 million individuals are chronically infected with Hepatitis C Virus (HCV). Chronic HCV infection can lead to potentially fatal outcomes including liver cirrhosis and hepatocellular carcinoma. HCV-specific immune responses play a major role in viral control and may explain why approximately 20% of infections are spontaneously cleared before the establishment of chronicity. Chronic infection, associated with prolonged antigen exposure, leads to immune exhaustion of HCV-specific T cells. These exhausted T cells are unable to control the viral infection. Before the introduction of direct acting antivirals (DAAs), interferon (IFN)-based therapies demonstrated successful clearance of viral infection in approximately 50% of treated patients. New effective and well-tolerated DAAs lead to a sustained virological response (SVR) in more than 95% of patients regardless of viral genotype. Researchers have investigated whether treatment, and the subsequent elimination of HCV antigen, can reverse this HCV-induced exhausted phenotype. Here we review literature exploring the restoration of HCV-specific immune responses following antiviral therapy, both IFN and DAA-based regimens. IFN treatment during acute HCV infection results in greater immune restoration than IFN treatment of chronically infected patients. Immune restoration data following DAA treatment in chronically HCV infected patients shows varied results but suggests that DAA treatment may lead to partial restoration that could be improved with earlier administration. Future research should investigate immune restoration following DAA therapies administered during acute HCV infection.

Hepatitis C Virus Genetic Variability, Human Immune Response, and Genome Polymorphisms: Which Is the Interplay?

Hepatitis C virus (HCV) infection is the main cause of chronic hepatitis, affecting an estimated 150 million people worldwide. Initial exposure to HCV is most often followed by chronic hepatitis, with only a minority of individuals spontaneously clearing the virus. The induction of sustained and broadly directed HCV-specific CD4⁺ and CD8⁺ T cell responses, together with neutralizing antibodies (nAb), and specific genetic polymorphism have been associated with spontaneous resolution of the infection. However, due to its high variability, HCV is able to overwhelm the host immune response through the rapid acquisition of mutations in the epitopes targeted by T cells and neutralizing antibodies. In this context, immune-mediated pressure represents the main force in driving HCV evolution. This review summarizes the data on HCV diversity and the current state of knowledge about the contributions of antibodies, T cells, and host genetic polymorphism in driving HCV evolution in vivo.

Clinical Significance of Polymorphisms in Immune Response Genes in Hepatitis C-Related Hepatocellular Carcinoma

Background and Aims: Polymorphisms in the immune response genes can contribute to clearance of hepatitis C virus (HCV) infection but also mediate liver inflammation and cancer pathogenesis. This study aimed to investigate the association of polymorphisms in PD-1 (PDCD1), IFNL3 (IL28B), and TLR2 immune related genes in chronic HCV patients with different hepatic and lymphoproliferative HCV-related diseases. Methods: Selected PDCD1, IFNL3, and TLR2 genes were tested by molecular approaches in 450 HCV-positive patients with increasing severity of underlying liver diseases [including chronic infection (CHC), cirrhosis and hepatocellular carcinoma (HCC)], in 238 HCV-positive patients with lymphoproliferative diseases [such as cryoglobulinemia and non-Hodgkin lymphoma (NHL)] and in 94 blood donors (BD). Results: While the rs12979860 IFNL3 T allele was found a good marker associated with HCV-outcome together with the rs111200466 TLR2 del variant, the rs10204525 PD-1.6 A allele was found to have an insignificant role in patients with HCV-related hepatic disorders. Though in Asian patients the combination of IFNL3 and PD-1.6 markers better define the HCV-related outcomes, in our series of Caucasian patients the PD-1.6 A-allele variant was observed very rarely. Conclusion: Differences in the incidence of HCV-related HCC and clinical response between Asians and Europeans may be partially due to the distribution of PD-1.6 genotype that we found divergent between these two populations. On the other hand, we confirmed in this study that the polymorphic variants within IFNL3 and TLR2 immune response genes are significantly associated with HCV-related disease progression in our cohort of Italian patients.

Acute Traumatic Brain Injury Induces CD4+ and CD8+ T Cell Functional Impairment by Upregulating the Expression of PD-1 via the Activated Sympathetic Nervous System

OBJECTIVE

Traumatic brain injury (TBI) induces immunosuppression in the acute phase, and the activation of the sympathetic nervous system (SNS) might play a role in this process, but the mechanism involved is unknown. Herein, we explored the impact of acute (a)TBI on the peripheral immune system and its correlation with the SNS and the T cell exhaustion marker, PD-1 (programmed cell death-1).

METHODS

Flow cytometry (FCM) was performed to analyze the expression of T cell markers and intracellular cytokines, interferon-γ and tumor necrosis factor-α, and the T cell exhaustion marker, PD-1, in the peripheral blood mononuclear cells (PBMCs) of TBI rats. Enzyme-linked immunosorbent assay (ELISA) was performed to analyze the concentration of norepinephrine (NE) in the serum. Propranolol was administrated to block the SNS in vivo and NE stimulation was used to imitate the activation of the SNS in vitro.

RESULTS

We found that the concentration of NE was significantly elevated after TBI, and the dysfunction of CD4+ and CD8+ T cells was reversed by the SNS blocker propranolol in vivo and imitated by the SNS neurotransmitter NE in vitro. The expression of PD-1 on CD4+ and CD8+ T cells was upregulated after aTBI, which was reversed by propranolol administration in vivo and imitated by NE stimulation in vitro. Furthermore, the PD-1 blocker reversed the dysfunction of CD4+ and CD8+T cells in vitro.

CONCLUSION

Our findings demonstrated that aTBI activated the SNS, and further upregulated the expression of PD-1 on CD4+ and CD8+ T cells, which, in turn, impaired their function and contributed to immunosuppression.

Modulation of the Immune System in Chronic Hepatitis C and During Antiviral Interferon-Free Therapy

The treatment of patients with chronic hepatitis C virus (HCV) infection has changed tremendously over the past 2 years, with an increasing variety of all-oral direct-acting antiviral (DAA) treatment regimens available for different HCV genotypes and distinct clinical settings. These treatments have significantly improved safety in patients with advanced liver disease compared with interferon (IFN)-based regimens. HCV modifies the human immune system to escape immunosurveillance via several mechanisms. One of the basic mechanisms of HCV is the ability to “switch” the immune response by reducing the activity of cells responsible for the elimination of virus-infected cells. IFN-free DAA treatment regimens provide a unique opportunity to assess the effect of HCV elimination on the immune system. Abrupt changes in the immune system can in some cases be responsible for two alarming processes: viral reactivation in patients with chronic hepatitis B and recurrence of hepatocellular carcinoma in patients with previous successful cancer treatment.

Is it possible to stop nucleos(t)ide analogue treatment in chronic hepatitis B patients?

Chronic hepatitis B (CHB) remains a challenging global health problem, with nearly one million related deaths per year. Nucleos(t)ide analogue (NA) treatment suppresses viral replication but does not provide complete cure of the hepatitis B virus (HBV) infection. The accepted endpoint for therapy is the loss of hepatitis B surface antigen (HBsAg), but this is hardly ever achieved. Therefore, indefinite treatment is usually required. Many different studies have evaluated NA therapy discontinuation after several years of NA treatment and before HBsAg loss. The results have indicated that the majority of patients can remain off therapy, with some even reaching HBsAg seroconversion. Fortunately, this strategy has proved to be safe, but it is essential to consider the risk of liver damage and other comorbidities and to ensure a close follow-up of the candidates before considering this strategy. Unanswered questions remain, namely in which patients could this strategy be effective and what is the optimal time point at which to perform it. To solve this enigma, we should keep in mind that the outcome will ultimately depend on the equilibrium between HBV and the host’s immune system. Viral parameters that have been described as good predictors of response in HBeAg(+) cases, have proven useless in HBeAg(-) ones. Since antiviral immunity plays an essential role in the control of HBV infection, we sought to review and explain potential immunological biomarkers to predict safe NA discontinuation in both groups.

Immune checkpoint receptors: homeostatic regulators of immunity

Alcoholic liver disease (ALD) is an escalating global problem accounting for more than 3 million deaths annually. Bacterial infections are diagnosed in 25-47% of hospitalized patients with cirrhosis and represent the most important trigger for acute decompensation, multi-organ failure, septic shock and death. Current guidelines recommend intensive antibiotic therapy, but this has led to the emergence of multi-drug resistant bacteria, which are associated with increased morbidity and mortality rates. As such, there is a pressing need to explore new paradigms for anti-infective therapy and host-directed immunomodulatory therapies are a promising approach. Paradoxically, cirrhotic patients are characterised by heightened immune activity and exacerbated inflammatory processes but are unable to contend with bacterial infection, demonstrating that whilst immune effector cells are primed, their antibacterial effector functions are switched-off, reflecting a skewed homeostatic balance between anti-pathogen immunity and host-induced immunopathology. Preservation of this equilibrium physiologically is maintained by multiple immune-regulatory checkpoints and these feedback receptors serve as pivotal regulators of the host immunity. Checkpoint receptor blockade is proving to be effective at rescuing deranged/exhausted immunity in pre-clinical studies for chronic viral infection and sepsis. This approach has also obtained FDA approval for restoring anti-tumor immunity, with improved response rates and good safety profiles. To date, no clinical studies have investigated checkpoint blockade in ALD, highlighting an area for development of host-targeted immunotherapeutic strategies in ALD, for which there are no current specific treatment options. This review aims at framing current knowledge on immune checkpoints and the possibility of their therapeutic utility in ALD-associated immune dysfunctions.

PD-L1-Independent Mechanisms Control the Resistance of Melanoma to CD4+ T Cell Adoptive Immunotherapy

Immunotherapy is becoming the standard of care for melanoma. However, resistance to therapy is a major problem. Previously, we showed that tumor-specific, cytotoxic CD4⁺ T cells from tyrosinase-related protein 1 transgenic mice could overcome secondary resistance to recurring melanoma when anti-programmed cell death 1 ligand (PD-L1) checkpoint blockade was combined with either anti-lymphocyte-activated gene 3 (LAG-3) Abs or depletion of tumor-specific regulatory T (T_reg) cells. In this study, we show that PD-L1 expressed by the host, not B16 melanoma, plays a major role in the early stages of exhaustion or primary resistance. We observed durable regression of melanoma in tumor-bearing PD-L1^-/-RAG^-/- mice with transfer of naive tumor-specific CD4⁺ T cells. However, exhausted tumor-specific CD4⁺ T cells, which included tumor-specific T_reg cells, failed to maintain durable regression of tumors in PD-L1^-/-RAG^-/- mice unless tumor-specific T_reg cells were eliminated, showing nonredundant pathways of resistance to immunotherapy were present. Translating these findings to a clinically relevant model of cancer immunotherapy, we unexpectedly showed that anti-PD-L1 checkpoint blockade mildly improved immunotherapy with tumor-specific CD4⁺ T cells and irradiation in wild-type mice. Instead, anti-LAG-3 checkpoint blockade, in combination with tumor-specific CD4⁺ T cells and irradiation, overcame primary resistance and treated established tumors resulting in fewer recurrences. Because LAG-3 negatively regulates effector T cell function and activates T_reg cells, LAG-3 blockade may be more beneficial in overcoming primary resistance in combination immunotherapies using adoptive cellular therapy and irradiation than blockade of PD-L1.

Interleukin-7 augments CD8+ T cells function and promotes viral clearance in chronic hepatitis C virus infection

Interleukin (IL)-7 is a potent proliferation, activation, and survival cytokine for CD8⁺ T cells to improve viral and tumor specific CD8⁺ T cell responses. However, the role of IL-7 in regulation of dysfunctional hepatitis C virus (HCV)-specific CD8⁺ T cells was not fully elucidated. Thus, a total of 53 patients with chronic hepatitis C and 24 healthy individuals were enrolled in the current study. Serum IL-7 and its receptor α chain CD127 expression was measured. The modulatory function of IL-7 to CD8⁺ T cells was investigated in both direct and indirect contact co-culture with HCVcc-infected Huh7.5 cells. Both serum IL-7 and CD127 expression on CD8⁺ T cells was significantly reduced in chronic HCV-infected patients, which was negatively correlated with HCV RNA. Stimulation of IL-7 promoted both cytotoxicity and cytokines (interferon-γ, tumor necrosis factor-α, and IL-2) production of CD8⁺ T cells from patients with chronic hepatitis C. Moreover, IL-7 increased proliferation of CD8⁺ T cells, while downregulated a critical repressor of cytokine signaling, suppressor of cytokine signaling 3 (SOCS3). The IL-7-mediated enhancement effects to CD8⁺ T cells were dependent on IL-6 production. The current data suggested that IL-7 induced both cytolytic and noncytolytic functions of CD8⁺ T cells probably via repression of SOCS3. IL-7 might be considered as one of the therapeutic candidates for treatment of chronic HCV infection.

Contradictory intrahepatic immune responses activated in high-load hepatitis C virus livers compared with low-load livers

We found a HLA class II histocompatibility antigen gene, DQ alpha 1 chain (HLA-DQA1), that was expressed more than 9-fold higher in high-load hepatitis C virus (HCV) livers than low-load HCV livers using transcriptomics of chronic HCV-infected livers. To further investigate this finding, we examined which cells were positive for HLA-DQA1 and what liver immune responses were different between HCV-high and -low livers. HLA-DQA1-positive cells were significantly increased in the HCV-high group, and most positive cells were identified as non-parenchymal sinusoid cells and lymphocytic infiltrates in the portal area. Parenchymal hepatocytes were negative for HLA-DQA1. HLA-DQA1-positive cells in the liver sinusoid were positive for CD68 (macrophages or Kupffer cells); those in the lymphocytic infiltrates were positive for CD20 (B cells) or CD3 (T cells). mRNA levels of antigen-presenting cell (APC) markers such as CD68 and CD11c were significantly upregulated in the HCV-high group and were correlated with HLA-DQA mRNA levels. CD8B mRNA (CD8⁺ T cells) was upregulated in both HCV-positive livers compared with HCV-negative livers, whereas CD154 mRNA (CD4⁺ T helper cell) was upregulated in the HCV-high group compared with the HCV-low group. The immune regulatory molecules FOXP3 mRNA (regulatory T cell, T reg) and programmed cell death ligand-1 (PD-L1) mRNA were significantly increased in the HCV-high group. HCV-high livers had two molecular immune responses: increased APC numbers and adaptive immunity and the induction of immune tolerance. The local hepatic imbalance of contradictory immune responses might be responsible for high HCV loads.

Program death-1 immune checkpoint and tumor microenvironment in malignant liver tumors

Hepatic malignancies are one of the leading causes of cancer death globally. Considering the limited efficacy of current standard treatments in management of patients with advanced liver cancers, there has been a growing interest in identifying novel therapies. Despite achieving promising results in initial clinical trials, the therapeutic benefit of immunotherapy is limited due to strong immune-tolerogenic characteristics of liver tumors. Therapeutic regimens that impede tumor immunosuppressive mechanisms or elaborate tumor-specific immunity may improve clinical outcomes of patients with liver malignancies. Programmed cell death 1 (PD-1), an inhibitory checkpoint molecule, and its ligands (PD-L1 and -L2) are the main mediators of immunosuppression within the tumor microenvironment. The expression level of PD-1/PD-L1 may act as a biomarker to predict disease progression, as well as long-term survival. Furthermore, early trials have demonstrated the efficacy and safety of targeting PD-1/PD-L1 as an emerging field in the management of patients with advanced hepatocellular carcinoma. We herein review the role of PD-1/PD-L1 in the pathogenesis of liver malignancies, as well as its potential diagnostic and therapeutic implications.

The Importance of Dendritic Cells in Maintaining Immune Tolerance

Immune tolerance is necessary to prevent the immune system from reacting against self, and thus to avoid the development of autoimmune diseases. In this review, we discuss key findings that position dendritic cells (DCs) as critical modulators of both thymic and peripheral immune tolerance. Although DCs are important for inducing both immunity and tolerance, increased autoimmunity associated with decreased DCs suggests their nonredundant role in tolerance induction. DC-mediated T cell immune tolerance is an active process that is influenced by genetic variants, environmental signals, as well as the nature of the specific DC subset presenting Ag to T cells. Answering the many open questions with regard to the role of DCs in immune tolerance could lead to the development of novel therapies for the prevention of autoimmune diseases.