Nonreversible MAIT cell‐dysfunction in chronic hepatitis C virus infection despite successful interferon‐free therapy

Mucosal-Associated Invariant T Cells in Regenerative Medicine

Although antibiotics to inhibit bacterial growth and small compounds to interfere with the productive life cycle of human immunodeficiency virus (HIV) have successfully been used to control HIV infection, the recent emergence of the drug-resistant bacteria and viruses poses a serious concern for worldwide public health. Despite intensive scrutiny in developing novel antibiotics and drugs to overcome these problems, there is a dilemma such that once novel antibiotics are launched in markets, sooner or later antibiotic-resistant strains emerge. Thus, it is imperative to develop novel methods to avoid this vicious circle. Here, we discuss the possibility of using induced pluripotent stem cell (iPSC)-derived, innate-like T cells to control infection and potential application of these cells for cancer treatment. Mucosal-associated invariant T (MAIT) cells belong to an emerging family of innate-like T cells that link innate immunity to adaptive immunity. MAIT cells exert effector functions without priming and clonal expansion like innate immune cells and relay the immune response to adaptive immune cells through production of relevant cytokines. With these characteristics, MAIT cells are implicated in a wide range of human diseases such as autoimmune, infectious, and metabolic diseases, and cancer. Circulating MAIT cells are often depleted by these diseases and often remain depleted even after appropriate remedy because MAIT cells are susceptible to activation-induced cell death and poor at proliferation in vivo, which threatens the integrity of the immune system. Because MAIT cells have a pivotal role in human immunity, supplementation of MAIT cells into immunocompromised patients suffering from severe depletion of these cells may help recapitulate or recover immunocompetence. The generation of MAIT cells from human iPSCs has made it possible to procure MAIT cells lost from disease. Such technology creates new avenues for cell therapy and regenerative medicine for difficult-to-cure infectious diseases and cancer and contributes to improvement of our welfare.

Role of MAIT cells in the immunopathogenesis of inflammatory diseases: New players in old game

Current advances in immunology have led to the identification of a population of novel innate immune T cells, called mucosa-associated invariant T (MAIT) cells. The cells in humans express an invariant TCRα chain (Vα7.2-Jα33) paired with a limited subset of TCRβ chains (Vβ2, 13 and 22), are restricted by the MHC class I (MH1)-related (MR)-1, and recognize molecules that are produced in the bacterial riboflavin (vitamin B2) biosynthetic pathway. They are present in the circulation, liver and at various mucosal sites (i.e. intestine, lungs and female reproductive tract, etc.). They kill host cells infected with bacteria and yeast, and secrete soluble mediators such as TNF-α, IFN-γ, IL-17, etc. The cells regulate immune responses and inflammation associated with a wide spectrum of acute and chronic diseases in humans. Since their discovery in 1993, significant advances have been made in understanding biology of MAIT cells and the potential role of these cells in the pathogenesis of autoimmune, inflammatory and infectious diseases as well as cancer in humans. The purpose of this review is to provide a current state of our knowledge about MAIT cell biology and delineate their role in autoimmune and inflammatory diseases (sterile or caused by infectious agents) and cancer in humans. A better understanding of the role of MAIT cells in human diseases may lead to novel ways of immunotherapies.

Intra-Hepatic Depletion of Mucosal-Associated Invariant T Cells in Hepatitis C Virus-Induced Liver Inflammation

BACKGROUND & AIMS

Chronic hepatitis affects phenotypes of innate and adaptive immune cells. Mucosal-associated invariant T (MAIT) cells are enriched in the liver as compared with the blood, respond to intra-hepatic cytokines, and (via the semi-invariant T-cell receptor) to bacteria translocated from the gut. Little is known about the role of MAIT cells in livers of patients with chronic hepatitis C virus (HCV) infection and their fate after antiviral therapy.

METHODS

We collected blood samples from 42 patients with chronic HCV infection who achieved a sustained virologic response after 12 weeks of treatment with sofosbuvir and velpatasvir. Mononuclear cells were isolated from blood before treatment, at weeks 4 and 12 during treatment, and 24 weeks after the end of treatment. Liver biopsies were collected from 37 of the patients prior to and at week 4 of treatment. Mononuclear cells from 56 blood donors and 10 livers that were not suitable for transplantation were used as controls. Liver samples were assessed histologically for inflammation and fibrosis. Mononuclear cells from liver and blood were studied by flow cytometry and analyzed for responses to cytokine and bacterial stimulation.

RESULTS

The frequency of MAIT cells among T cells was significantly lower in blood and liver samples of patients with HCV infection than of controls (median, 1.31% vs 2.32% for blood samples, P = .0048; and median, 4.34% vs 13.40% for liver samples, P = .001). There was an inverse correlation between the frequency of MAIT cells in the liver and histologically determined levels of liver inflammation (r = -.5437, P = .0006) and fibrosis (r = -.5829, P = .0002). MAIT cells from the liver had higher levels of activation and cytotoxicity than MAIT cells from blood (P < .0001). Production of interferon gamma by MAIT cells was dependent on monocyte-derived interleukin 18, and was reduced in patients with HCV infection in response to T-cell receptor-mediated but not cytokine-mediated stimulation, as compared with controls. Anti-viral therapy rapidly decreased liver inflammation and MAIT cell activation and cytotoxicity, and increased the MAIT cell frequency among intra-hepatic but not blood T cells. The MAIT cell response to T-cell receptor-mediated stimulation did not change during the 12 weeks of antiviral therapy.

CONCLUSIONS

In analyses of paired blood and liver samples from patients with chronic HCV infection before, during, and after antiviral therapy with sofosbuvir and velpatasvir, we found that intrahepatic MAIT cells are activated by monocyte-derived cytokines and depleted in HCV-induced liver inflammation.

Time course of cellular HIV-DNA and low-level HIV viremia in HIV-HCV co-infected patients whose HCV infection had been successfully treated with directly acting antivirals

This longitudinal study described cellular HIV-DNA changes and their correlation with HIV low-level plasma viremia (LLV) in HIV-HCV co-infected patients on successful antiretroviral and anti-HCV therapy by treatment with direct-acting antivirals (DAA). Thirty-nine patients were examined prior to the start of DAA (T0), after week 12 (T1) and 24 weeks (T2) of anti-HCV therapy. Cellular PBMC HIV-DNA was analysed as an absolute value and as the percentage of increase or decrease from T0 to T2. Patients were classified as having undetectable plasma HIV viraemia (UV) or LLV in the year before the start of anti-HCV treatment and within the T0-T2 study period. Thirty-five patients (89.7%) of the 39 subjects enrolled had the same plasma HIV viraemia control in the year before HCV treatment and in the T0-T2 interval. The HIV-DNA value at T0 and at T2 was higher in patients with LLV than in subjects with UV (p = 0.015 and p = 0.014, respectively). A similar proportion of patients with LLV and UV experienced an increase or decrease of HIV-DNA from T0 to T2. The percentage increase in HIV-DNA value (262.8%) from T0 to T2 was higher compared to the decrease (43.5%) in patients with UV (p = 0.012), and it was higher compared to the percentage increase in HIV-DNA value reported in subjects with LLV (262.8 versus 49%, p = 0.026). HIV-HCV co-infected patients experienced a multifaceted perturbation of cellular HIV-DNA levels within a 24-week period during anti-HCV treatment; the extent of the phenomenon was greater in subjects with UV. Fast HCV-RNA clearance seemed to have a greater influence on the cellular reservoir than on plasma HIV-RNA.

MAIT be different-persisting dysfunction after DAA-mediated clearance of chronic hepatitis C virus infection

MAIT cells are an abundant innate-like T-cell subset that is defined by the invariant T-cell receptor (iTCR) V-alpha chain Vα7.2-Jα33. Little is currently known about their frequency and function in chronic hepatitis C virus (HCV) infection and their fate after therapy-mediated HCV elimination by direct acting antivirals (DAA). In this issue of the European Journal of Immunology, Hengst et al. [Eur. J. Immunol. 2016. 46: 2204-2210] give important novel insights into the biological role of MAIT cells in a relevant human chronic viral infection by showing that first, MAIT cells are only present at low frequencies in chronic HCV infection; second, circulating MAIT cells in HCV patients also display an altered phenotype; third, they are impaired in their MR-1-dependent effector functions and finally, and maybe most importantly, MAIT-cell frequency and function was not restored after HCV elimination by DAA therapy. These results suggest that MAIT cells are severely affected by a chronic human viral infection in their frequency and function and that this impairment is not reversed after HCV elimination. This is in contrast to rapid DAA-mediated restorations of NK-cell and CD8(+) T-cell functions, and indicates a differential impact of chronic infection and clearance on different immune cell subsets.

Immune Reconstitution After HCV Clearance With Direct Antiviral Agents: Potential Consequences for Patients With HCC?

Recent introduction of all-oral direct-acting antiviral (DAA) treatment has revolutionized care of patients with chronic hepatitis C virus infection. Because patients with different liver disease stages have been treated with great success including those awaiting liver transplantation, therapy has been extended to patients with hepatocellular carcinoma as well. From observational studies among compensated cirrhotic hepatitis C patients treated with interferon-containing regimens, it would have been expected that the rate of hepatocellular carcinoma occurrence is markedly decreased after a sustained virological response. However, recently 2 studies have been published reporting markedly increased rates of tumor recurrence and occurrence after viral clearance with DAA agents. Over the last decades, it has been established that chronic antigen stimulation during persistent infection with hepatitis C virus is associated with continuous activation and impaired function of several immune cell populations, such as natural killer cells and virus-specific T cells. This review therefore focuses on recent studies evaluating the restoration of adaptive and innate immune cell populations after DAA therapy in patients with chronic hepatitis C virus infection in the context of the immune responses in hepatocarcinogenesis.

The Path to Cancer and Back: Immune Modulation During Hepatitis C Virus Infection, Progression to Fibrosis and Cancer, and Unexpected Roles of New Antivirals

Hepatitis C virus (HCV) infection affects over 130 million individuals worldwide, and it is the number 1 reason for liver transplantation in the United States. HCV infection progresses in a slow chronic fashion eliciting a strong but ineffective immune response, mainly characterized by NK cell dysfunction and T cell exhaustion. The chronic hepatic inflammation leads to liver fibrosis, cirrhosis, and cancer in a significant number of patients. In recent years, groundbreaking research has led to the discovery of new HCV-specific direct-acting antivirals (DAAs), which have an unprecedented efficacy to clear the virus, and establish a sustained virological response. Indeed, curing HCV infection with an oral medication is now reality. The effects of DAAs in mitigating the HCV-related complications of liver fibrosis and cancer are yet largely unknown. Nonetheless, recent controversial reports suggest a potential increase in liver cancer recurrence upon use of DAAs. In the current article, we review the most important immune-mediated mechanisms underlying HCV chronicity and the development of liver fibrosis and cancer. Furthermore, we discuss recent concern on use of the new agents.

Multiple layers of heterogeneity and subset diversity in human MAIT cell responses to distinct microorganisms and to innate cytokines

Mucosa-associated invariant T (MAIT) cells are a large innate-like T-cell subset in humans defined by invariant TCR Vα7.2 use and expression of CD161. MAIT cells recognize microbial riboflavin metabolites of bacterial or fungal origin presented by the monomorphic MR1 molecule. The extraordinary level of evolutionary conservation of MR1 and the limited known diversity of riboflavin metabolite antigens have suggested that MAIT cells are relatively homogeneous and uniform in responses against diverse microbes carrying the riboflavin biosynthesis pathway. The ability of MAIT cells to exhibit microbe-specific functional specialization has not been thoroughly investigated. Here, we found that MAIT cell responses against Escherichia coli and Candida albicans displayed microbe-specific polyfunctional response profiles, antigen sensitivity, and response magnitudes. MAIT cell effector responses against E. coli and C. albicans displayed differential MR1 dependency and TCR β-chain bias, consistent with possible divergent antigen subspecificities between these bacterial and fungal organisms. Finally, although the MAIT cell immunoproteome was overall relatively homogenous and consistent with an effector memory-like profile, it still revealed diversity in a set of natural killer cell-associated receptors. Among these, CD56, CD84, and CD94 defined a subset with higher expression of the transcription factors promyelocytic leukemia zinc finger (PLZF), eomesodermin, and T-bet and enhanced capacity to respond to IL-12 and IL-18 stimulation. Thus, the conserved and innate-like MAIT cells harbor multiple layers of functional heterogeneity as they respond to bacterial or fungal organisms or innate cytokines and adapt their antimicrobial response patterns in a stimulus-specific manner.

Designing an HCV vaccine: a unique convergence of prevention and therapy?

Direct acting antivirals can cure chronic hepatitis C virus (HCV) infection but whether they will reduce global liver disease burden is uncertain. Most chronic infections are undiagnosed and transmission has increased in recent years. The first trial of a preventive vaccine is now underway in humans at risk for HCV infection. It will test the novel hypothesis that T cell-mediated immunity alone can prevent persistent HCV infection. Another vaccine that elicits neutralizing antibodies is at an advanced stage of development. Attention is turning to the understudied question of whether direct acting antiviral (DAA) cure of chronic infection restores HCV immunity. If not, it will be important to determine if preventive vaccines can also act therapeutically to reverse immune dysfunction and protect from re-infection.

MAIT cells are reduced in frequency and functionally impaired in human T lymphotropic virus type 1 infection: Potential clinical implications

HTLV-1 infection is associated with several inflammatory disorders, including the neurodegenerative condition HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is unclear why a minority of infected subjects develop HAM/TSP. The cellular immune response has been implicated in the development of inflammatory alterations in these patients; however the pathogenic mechanisms for disease progression remain unclear. Furthermore, HTLV-1-infected individuals have an increase incidence of Mycobacterium tuberculosis (Mtb) infection, suggesting that immunological defect are associated with HTLV-1 infection. Evidence suggests an important role for Mucosal-associated invariant T (MAIT) cells in the early control of Mtb infection. Chronic viral infections like HIV and HCV have been associated with decreased frequency and functionality of MAIT cells. We hypothesized that HTLV-1 infection is associated with similar perturbations in MAIT cells. We investigated MAIT cell frequency, phenotype, and function by flow cytometry in a cohort of 10 asymptomatic and 10 HAM/TSP HTLV-1 infected patients. We found that MAIT cells from HTLV-1-infected subjects were reduced and showed high co-expression of the activation markers CD38 and HLA-DR but normal levels of CCR6 and CD127. MAIT cells had a lower expression of the transcription factor PLZF in HAM/TSP patients. Unlike Tax-specific CD8+T cells, which are hyperfunctional, MAIT cells from HTLV-1-infected subjects had a poor IFNγ response following antigen stimulation. MAIT cell perturbations in HTLV-1 infection were not associated with HTLV-1 proviral load and MAIT cells were not infected by HTLV-1 in vivo. Rather, MAIT cells loss was associated with immune activation. Overall, our results do not support a role for MAIT cells in HAM/TSP pathogenesis but reduced numbers of MAIT cells, together with their poor functionality, could contribute to the increased susceptibility of HTLV-1-infected individuals to other infectious agents.

Hepatitis C virus infection

Hepatitis C virus (HCV) is a hepatotropic RNA virus that causes progressive liver damage, which might result in liver cirrhosis and hepatocellular carcinoma. Globally, between 64 and 103 million people are chronically infected. Major risk factors for this blood-borne virus infection are unsafe injection drug use and unsterile medical procedures (iatrogenic infections) in countries with high HCV prevalence. Diagnostic procedures include serum HCV antibody testing, HCV RNA measurement, viral genotype and subtype determination and, lately, assessment of resistance-associated substitutions. Various direct-acting antiviral agents (DAAs) have become available, which target three proteins involved in crucial steps of the HCV life cycle: the NS3/4A protease, the NS5A protein and the RNA-dependent RNA polymerase NS5B protein. Combination of two or three of these DAAs can cure (defined as a sustained virological response 12 weeks after treatment) HCV infection in >90% of patients, including populations that have been difficult to treat in the past. As long as a prophylactic vaccine is not available, the HCV pandemic has to be controlled by treatment-as-prevention strategies, effective screening programmes and global access to treatment.

The Risk of Hepatocellular Carcinoma After Directly Acting Antivirals for Hepatitis C Virus Treatment in Liver Transplanted Patients: Is It Real?

INTRODUCTION

Since directly acting antivirals (DAAs) for treatment of hepatitis C virus (HCV) were introduced, conflicting data emerged about the risk of hepatocellular carcinoma (HCC) after interferon (IFN)-free treatments. We present a case of recurrent, extra-hepatic HCC in a liver-transplanted patient soon after successful treatment with DAAs, along with a short review of literature.

CASE PRESENTATION

In 2010, a 53-year old man, affected by chronic HCV (genotype 1) infection and decompensated cirrhosis, underwent liver resection for HCC and subsequently received orthotopic liver transplantation. Then, HCV relapsed and, in 2013, he was treated with pegylated-IFN plus ribavirin; but response was null. In 2014, he was treated with daclatasvir plus simeprevir to reach sustained virological response. At baseline and at the end of HCV treatment, computed tomography (CT) scan of abdomen excluded any lesions suspected for HCC. However, alpha-fetoprotein was 2.9 ng/mL before DAAs, increasing up to 183.1 ng/mL at week-24 of follow-up after the completion of therapy. Therefore, CT scan of abdomen was performed again, showing two splenic HCC lesions.

CONCLUSIONS

Overall, nine studies have been published about the risk of HCC after DAAs. Patients with previous HCC should be carefully investigated to confirm complete HCC remission before starting, and proactive follow-up should be performed after DAA treatment.

Ledipasvir plus sofosbuvir fixed-dose combination for 6 weeks in patients with acute hepatitis C virus genotype 1 monoinfection (HepNet Acute HCV IV): an open-label, single-arm, phase 2 study

BACKGROUND

Early treatment of acute hepatitis C virus (HCV) infection with interferon alfa is highly effective, but can be associated with frequent side-effects. We investigated the safety and efficacy of an interferon-free regimen for treatment of acute HCV infection.

METHODS

In this prospective, open-label, multicentre, single-arm pilot study, we enrolled adults (≥18 years) with acute HCV genotype 1 monoinfection from ten centres in Germany. Patients were given ledipasvir (90 mg) plus sofosbuvir (400 mg) as a fixed-dose combination tablet once daily for 6 weeks. The primary efficacy outcome was the proportion of patients with sustained virological response (defined as undetectable HCV RNA 12 weeks after the end of treatment; other primary outcomes were safety and tolerability of ledipasvir plus sofosbuvir. The primary analysis population consisted of all patients who received at least one dose of study drug. Safety was also assessed in all patients who received at least one dose of the study drug. This trial is registered with ClinicalTrials.gov, number NCT02309918.

FINDINGS

Between Nov 19, 2014, and Nov 10, 2015, we enrolled 20 patients. Median HCV RNA viral load at baseline was 4·04 log₁₀ IU/mL (1·71-7·20); 11 patients were infected with HCV genotype 1a and nine patients with genotype 1b. All patients achieved a sustained virological response 12 weeks after the end of treatment (20 [100%] of 20 patients). Treatment was well tolerated; there were no drug-related serious adverse events. Up to 12 weeks after treatment, 22 possible or probable drug-related adverse events were reported. There was one serious adverse event, which was judged unrelated to the study drug; one patient was admitted to hospital for surgery of a ruptured cruciate ligament.

INTERPRETATION

Treatment for 6 weeks with ledipasvir plus sofosbuvir was well tolerated and highly effective in patients with acute HCV genotype 1 monoinfection. Short-duration treatment of acute hepatitis C might prevent the spread of HCV in high-risk populations.

FUNDING

Gilead Sciences, HepNet Study-House/German Liver Foundation, and German Centre for Infection Research (DZIF).

The role of mucosal-associated invariant T cells in infectious diseases

Mucosal-associated invariant T (MAIT) cells are donor-unrestricted lymphocytes that are surprisingly abundant in humans, representing 1-10% of circulating T cells and further enriched in mucosal tissues. MAIT cells recognize and are activated by small molecule ligands produced by microbes and presented by MR1, a highly conserved MHC-related antigen-presenting protein that is ubiquitously expressed in human cells. Increasing evidence suggests that MAIT cells play a protective role in anti-bacterial immunity at mucosal interfaces. Some fungi are known to produce MAIT-activating ligands, but the role of MAIT cells in fungal infections has not yet been investigated. In viral infections, specifically HIV, which has received the most study, MAIT cell biology is clearly altered, but the mechanisms explaining these alterations and their clinical significance are not yet understood. Many questions remain unanswered about the potential of MAIT cells for protection or pathogenesis in infectious diseases. Because they interact with the universal, donor-unrestricted ligand-presenting MR1 molecule, MAIT cells may be attractive immunotherapy or vaccine targets. New tools, including the development of MR1-ligand tetramers and next-generation T-cell receptor sequencing, have the potential to accelerate MAIT cell research and lead to new insights into the role of this unique set of lymphocytes in infectious diseases.

Future landscape of hepatitis C research - Basic, translational and clinical perspectives

With the latest all-oral interferon- and ribavirin-free regimens based on direct acting antivirals against the hepatitis C virus (HCV), sustained virological response rates of >90% are achieved, which is equivalent to cure. This has become possible for all genotypes and all subgroups of patients, including many of the most difficult-to-treat populations so far. Since a prophylactic HCV vaccine is not yet available, control of HCV infection will for the time being have to rely on the use of effective and safe antiviral treatments as well as their accessibility and affordability. Different approaches may apply to different parts of the world, eradication of HCV representing a major long-term goal. Whether hepatitis C becomes the first chronic viral infection to be eradicated without a prophylactic vaccine remains to be shown. Here, we briefly summarize advances in the molecular virology of hepatitis C, highlight lessons of biological relevance that were learned through the study of HCV, and its translational and clinical implications. We have also listed selected unsolved challenges, emphasizing that HCV is a unique model and that advances in this direction may yield knowledge of broad biological significance, novel technologies and insights into related important human pathogens.

Direct-Acting Antiviral-Induced Hepatitis C Virus Clearance Does Not Completely Restore the Altered Cytokine and Chemokine Milieu in Patients With Chronic Hepatitis C

BACKGROUND

 Persistent infection with hepatitis C virus (HCV) causes profound alterations of the cytokine and chemokine milieu in peripheral blood. However, it is unknown to what extend these alterations affect the progression of liver disease and whether HCV clearance normalizes soluble inflammatory mediators.

METHODS

 We performed multianalyte profiling of 50 plasma proteins in 28 patients with persistent HCV infection and advanced stages of liver fibrosis or cirrhosis and 20 controls with fatty liver disease. The patients were treated for 24 weeks with sofosbuvir and ribavirin and underwent sampling longitudinally. Ten patients experienced viral relapse after treatment cessation.

RESULTS

 The cytokine and chemokine expression pattern was markedly altered in patients with chronic HCV infection as compared to healthy controls and patients with nonalcoholic steatohepatitis. Distinct soluble factors were associated with the level of fibrosis/cirrhosis, viral replication, or treatment outcome. The baseline expression level of 10 cytokines distinguished patients with a sustained viral response from those who experienced viral relapse. While the majority of upregulated analytes declined during and after successful therapy, HCV clearance did not lead to a restoration of parameters that were suppressed.

CONCLUSIONS

 Chronic HCV infection appears to disrupt the milieu of soluble inflammatory mediators even after viral clearance. Thus, HCV cure does not lead to complete immunological restitution.

MAIT cells: new guardians of the liver

The liver is an important immunological organ that remains sterile and tolerogenic in homeostasis, despite continual exposure to non-self food and microbial-derived products from the gut. However, where intestinal mucosal defenses are breached or in the presence of a systemic infection, the liver acts as a second 'firewall', because of its enrichment with innate effector cells able to rapidly respond to infections or tissue dysregulation. One of the largest populations of T cells within the human liver are mucosal-associated invariant T (MAIT) cells, a novel innate-like T-cell population that can recognize a highly conserved antigen derived from the microbial riboflavin synthesis pathway. MAIT cells are emerging as significant players in the human immune system, associated with an increasing number of clinical diseases of bacterial, viral, autoimmune and cancerous origin. As reviewed here, we are only beginning to investigate the potential role of this dominant T-cell subset in the liver, but the reactivity of MAIT cells to both inflammatory cytokines and riboflavin derivatives suggests that MAIT cells may have an important role in first line of defense as part of the liver firewall. As such, MAIT cells are promising targets for modulating the host defense and inflammation in both acute and chronic liver diseases.

Frequencies of Circulating MAIT Cells Are Diminished in Chronic HCV, HIV and HCV/HIV Co-Infection and Do Not Recover during Therapy

OBJECTIVE

Mucosal-associated invariant T (MAIT) cells comprise a subpopulation of T cells that can be activated by bacterial products and cytokines to produce IFN-γ. Since little is known on MAIT cells during HCV infection, we compared their phenotype and function in comparison to HIV and HCV/HIV co-infected patients, and determined the effect of IFN-α-based and direct-acting antiviral therapy on MAIT cells of HCV patients.

METHODS

Blood samples from patients with chronic HCV (CHCV), virologically suppressed HIV, acute HCV/HIV co-infection (AHCV/HIV) and healthy individuals were examined by flowcytometry for phenotype and function of MAIT and NK cells.

RESULTS AND CONCLUSIONS

Compared to healthy individuals, the frequency of CD161+Vα7.2+ MAIT cells was significantly decreased in patients with CHCV, HIV and AHCV/HIV co-infection. CD38 expression on MAIT cells was increased in AHCV/HIV patients. MAIT cells were responsive to IFN-α in vitro as evidenced by enhanced frequencies of IFN-γ producing cells. IFN-α-based therapy for CHCV decreased the frequency of IFN-γ+ MAIT cells, which was still observed 24 weeks after successful therapy. Importantly, even after successful IFN-α-based as well as IFN-α-free therapy for CHCV, decreased frequencies of MAIT cells persisted. We show that the frequencies of MAIT cells are reduced in blood of patients with CHCV, HIV and in AHCV/HIV co-infection compared to healthy individuals. Successful therapy for CHCV did not normalize MAIT cell frequencies at 24 weeks follow up. The impact of HIV and HCV infection on the numbers and function of MAIT cells warrant further studies on the impact of viral infections and the antimicrobial function of MAIT cells.