Effect of killer immunoglobulin-like receptors in the response to combined treatment in patients with chronic hepatitis C virus infection

IL-10 indirectly modulates functional activity of CD4+CD28null T-lymphocytes through LFA-3 and HLA class II inhibition

Expansion of CD4+CD28null T-lymphocytes is common in chronic heart failure (CHF) patients. Its ability to produce high levels of proinflammatory cytokines is probably the key role of these cells in CHF. IL-10 is a candidate for limiting CD4+CD28null T-lymphocyte responses, whereas tumour necrosis factor (TNF) is the cytokine most closely involved in the loss of CD28 expression. Serum levels of TNF and IL-10 were measured in 65 CHF patients (mean age, 65.2 ± 13.84 years). Patients with an IL-10/TNF ratio ≥1 had significantly lower levels of CD4+CD28null T-lymphocytes than those with a ratio <1. In vitro, IL-10 reduced the frequency of proliferative CD4+CD28null T-lymphocytes stimulated with anti-CD3. Pre-treatment with IL-10 before anti-CD3 stimulation was required for the cytokine to inhibit TNF production by CD4+CD28null T-lymphocytes. In addition to the previously described effect of IL-10 on HLA-DR and ICAM-1 expression, LFA-3 protein and mRNA levels were reduced in the presence of the cytokine in monocytes. IL-10 inhibition on CD4+CD28null T-lymphocytes may be mediated by a reduction in HLA class II and LFA-3 expression because blocking interactions with these costimulators has similar effects to those of IL-10 treatment. Moreover, costimulation through CD2/LFA-3 interaction is enough to induce proliferation and cytokine production in CD4+CD28null T-lymphocytes.

Unveiling the Significance of HLA and KIR Diversity in Underrepresented Populations

Human leukocyte antigen (HLA) molecules and their relationships with natural killer (NK) cells, specifically through their interaction with killer-cell immunoglobulin-like receptors (KIRs), exhibit robust associations with the outcomes of diverse diseases. Moreover, genetic variations in HLA and KIR immune system genes offer limitless depths of complexity. In recent years, a surge of high-powered genome-wide association studies (GWASs) utilizing single nucleotide polymorphism (SNP) arrays has occurred, significantly advancing our understanding of disease pathogenesis. Additionally, advances in HLA reference panels have enabled higher resolution and more reliable imputation, allowing for finer-grained evaluation of the association between sequence variations and disease risk. However, it is essential to note that the majority of these GWASs have focused primarily on populations of Caucasian and Asian origins, neglecting underrepresented populations in Latin America and Africa. This omission not only leads to disparities in health care access but also restricts our knowledge of novel genetic variants involved in disease pathogenesis within these overlooked populations. Since the KIR and HLA haplotypes prevalent in each population are clearly modelled by the specific environment, the aim of this review is to encourage studies investigating HLA/KIR involvement in infection and autoimmune diseases, reproduction, and transplantation in underrepresented populations.

Immunological Aspects of Infertility-The Role of KIR Receptors and HLA-C Antigen

The mechanisms of immune tolerance of a mother against an antigenically foreign fetus without a concomitant loss of defense capabilities against pathogens are the factors underlying the success of a pregnancy. A significant role in human defense is played by killer immunoglobulin-like receptor (KIR) receptors, which regulate the function of the natural killer (NK) cells capable of destroying antigenically foreign cells, virus-infected cells, or tumor-lesioned cells. A special subpopulation of NK cells called uterine NK cells (uNK) is found in the uterus. Disruption of the tolerance process or overactivity of immune-competent cells can lead to immune infertility, a situation in which a woman's immune system attacks her own reproductive cells, making it impossible to conceive or maintain a pregnancy. Since the prominent role of the inflammatory response in infertility, including KIR receptors and NK cells, has been postulated, the process of antigen presentation involving major histocompatibility complex (MHC) molecules (HLA) appears to be crucial for a successful pregnancy. Proper interactions between KIR receptors on female uNK cells and HLA class I molecules, with a predominant role for HLA-C, found on the surface of germ cells, are strategically important during embryo implantation. In addition, maintaining a functional balance between activating and inhibitory KIR receptors is essential for proper placenta formation and embryo implantation in the uterus. A disruption of this balance can lead to complications during pregnancy. The discovery of links between KIR and HLA-C has provided valuable information about the complexity of maternal-fetal immune interactions that determine the success of a pregnancy. The great diversity of maternal KIR and fetal HLA-C ligands is associated with the occurrence of KIR/HLA-C combinations that are more or less favorable for reproductive success.

The New Kid on the Block: HLA-C, a Key Regulator of Natural Killer Cells in Viral Immunity

The human leukocyte antigen system (HLA) is a cluster of highly polymorphic genes essential for the proper function of the immune system, and it has been associated with a wide range of diseases. HLA class I molecules present intracellular host- and pathogen-derived peptides to effector cells of the immune system, inducing immune tolerance in healthy conditions or triggering effective immune responses in pathological situations. HLA-C is the most recently evolved HLA class I molecule, only present in humans and great apes. Differentiating from its older siblings, HLA-A and HLA-B, HLA-C exhibits distinctive features in its expression and interaction partners. HLA-C serves as a natural ligand for multiple members of the killer-cell immunoglobulin-like receptor (KIR) family, which are predominately expressed by natural killer (NK) cells. NK cells are crucial for the early control of viral infections and accumulating evidence indicates that interactions between HLA-C and its respective KIR receptors determine the outcome and progression of viral infections. In this review, we focus on the unique role of HLA-C in regulating NK cell functions and its consequences in the setting of viral infections.

Investigation of the Effect of KIR-HLA Pairs on Hepatocellular Carcinoma in Hepatitis C Virus Cirrhotic Patients

Simple Summary

Natural killer (NK) cells normally respond to tumor cells and virally infected cells by killing them via the innate immune system. However, the functional impairment of NK cells has been observed in hepatocellular carcinoma. The NK-cell phenotype is partially mediated through the binding of killer cell immunoglobulin-like receptors (KIR) with human leukocyte antigen (HLA) class I ligands. This study evaluated the involvement of KIR–HLA pairs in hepatocellular carcinoma development in 211 patients with hepatitis C virus-associated cirrhosis. HLA-Bw4 and the KIR3DL1+HLA-Bw4 pair were significantly associated with hepatocellular carcinoma onset during a median follow-up of 6.6 years, which suggested that functional interactions between KIR and HLA or HLA-Bw4 may influence the risk of cancer development.

Abstract

Natural killer cells are partially mediated through the binding of killer cell immunoglobulin-like receptors (KIR) with human leukocyte antigen (HLA) class I ligands. This investigation examined the risk of hepatocellular carcinoma (HCC) in relation to KIR–HLA pairs in patients with compensated hepatitis C virus (HCV)-associated cirrhosis. A total of 211 Japanese compensated HCV cirrhotic cases were retrospectively enrolled. After KIR, HLA-A, HLA-Bw, and HLA-C typing, associations between HLA, KIR, and KIR–HLA combinations and HCC development were evaluated using the Cox proportional hazards model with the stepwise method. During a median follow-up period of 6.6 years, 69.7% of patients exhibited HCC. The proportions of HLA-Bw4 and the KIR3DL1 + HLA-Bw4 pair were significantly higher in patients with HCC than in those without (78.9% vs. 64.1%; odds ratio (OR)—2.10, 95% confidence interval (CI)—1.10–4.01; p = 0.023 and 76.2% vs. 60.9%, odds ratio—2.05, p = 0.024, respectively). Multivariate analysis revealed the factors of male gender (hazard ratio (HR)—1.56, 95% CI—1.12–2.17; p = 0.009), α-fetoprotein > 5.6 ng/mL (HR—1.56, 95% CI—1.10–2.10; p = 0.011), and KIR3DL1 + HLA-Bw4 (HR—1.69, 95% CI—1.15–2.48; p = 0.007) as independent risk factors for developing HCC. Furthermore, the cumulative incidence of HCC was significantly higher in patients with KIR3DL1 + HLA-Bw4 than in those without (log-rank test; p = 0.013). The above findings suggest KIR3DL1 + HLA-Bw4, in addition to HLA-Bw4, as a novel KIR–HLA pair possibly associated with HCC development in HCV cirrhosis. HCV-associated cirrhotic patients with the risk factors of male gender, α-fetoprotein > 5.6 ng/mL, and KIR3DL1 + HLA-Bw4 may require careful surveillance for HCC onset.

Unconventional Peptide Presentation by Classical MHC Class I and Implications for T and NK Cell Activation

T cell-mediated immune recognition of peptides is initiated upon binding of the antigen receptor on T cells (TCR) to the peptide-MHC complex. TCRs are typically restricted by a particular MHC allele, while polymorphism within the MHC molecule can affect the spectrum of peptides that are bound and presented to the TCR. Classical MHC Class I molecules have a confined binding groove that restricts the length of the presented peptides to typically 8-11 amino acids. Both N- and C-termini of the peptide are bound within binding pockets, allowing the TCR to dock in a diagonal orientation above the MHC-peptide complex. Longer peptides have been observed to bind either in a bulged or zig-zag orientation within the binding groove. More recently, unconventional peptide presentation has been reported for different MHC I molecules. Here, either N- or C-terminal amino acid additions to conventionally presented peptides induced a structural change either within the MHC I molecule that opened the confined binding groove or within the peptide itself, allowing the peptide ends to protrude into the solvent. Since both TCRs on T cells and killer immunoglobulin receptors on Natural Killer (NK) cells contact the MHC I molecule above or at the periphery of the peptide binding groove, unconventionally presented peptides could modulate both T cell and NK cell responses. We will highlight recent advances in our understanding of the functional consequences of unconventional peptide presentation in cellular immunity.

Clinical and histopathological changes in different KIR gene profiles in chronic HCV Romanian patients

Hepatitis C virus (HCV)-infected individuals may have a faster progression of liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC) development when influenced by host, viral and environmental factors. Hepatitis C virus disease progression is also associated with genetic variants of specific killer cell immunoglobulin-like receptors (KIRs) and genes of the major histocompatibility complex (MHC). The aim of the present study was to correlate clinical, virologic and biochemical parameters and to evaluate the possible influence of KIR genes and their HLA class I ligands in patients infected with hepatitis C virus. The present study analysed a total of 127 chronic HCV-infected patients for various biochemical and genetics factors that can influence disease progression and prognosis. Liver function parameters such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), direct bilirubin (DB), alpha-fetoprotein (AFP), HCV RNA levels and fibrosis indices were analysed using well-established biochemical methods. At the same time, KIR and HLA genotyping was performed using a polymerase chain reaction sequence-specific primer technique. Analysis of HLA class I and HLA ligands revealed that HLA-C*12:02 and HLA-A3 and HLA-A11 were positively associated with the F3-F4 fibrosis group (p = .026; OR = 8.717, CI = 1.040-73.077; respectively, p = .047; OR = 2.187; 95% CI = 1.066-4.486). KIR2DL2-positive patients had high median levels of AST after treatment and direct bilirubin levels when compared to KIR2DL2-negative patients (p = .013, respectively, p = .028). KIR2DL2/KIR2DL2-C1C1 genotype was associated with increased AST, ALT and GGT levels. A higher GGT level was also observed in KIR2DS2-C1-positive patients when compared to KIR2DS2-C1-negative patients. The present research demonstrates several links between specific clinical, virologic and biochemical parameters and the expression of KIR genes and their HLA ligands in HCV-infected patients. These connections should be taken into account when considering disease development and treatment.

Genetic contribution of endoplasmic reticulum aminopeptidase 1 polymorphisms to liver fibrosis progression in patients with HCV infection

The endoplasmic reticulum aminopeptidase ERAP1 regulates innate and adaptive immune responses, trimming peptides and loading onto HLA class I molecules. Coding single nucleotide polymorphisms within ERAP1 are associated with autoimmune diseases, viral infections, and cancer development. Our purpose was to analyze the influence of ERAP1 variants on fibrogenesis in hepatitis C virus (HCV)-infected patients. A range of ERAP1 polymorphisms were genotyped in 722 unrelated Caucasian patients diagnosed with chronic HCV from two Spanish cohorts. Patients were classified according to their fibrosis stage. Paraffin-embedded tissue microarrays were constructed to assess ERAP1 expression (HCV = 38; alcoholic = 20) by immunohistochemistry. A statistical algorithm was applied to derive a fibrogenesis prediction model. The ERAP1 variants rs30187/T (K528, p_c < 0.001) and rs27044/G (Q730, p_c < 0.001) were related with severe fibrosis. These results were validated in the two independent cohorts. Furthermore, patients with the rs30187/T allele had stronger ERAP1 protein expression than those with the rs30187/C (p < 0.05). The statistical model showed that patients with rs30187 C/T and T/T genotypes took 15.58 years (median) to develop advanced fibrosis, but this value was 32.08 years in patients carrying C/C genotype (p < 0.005). ERAP1 variants may influence the clinical course of fibrogenesis in HCV-infected patients. These polymorphisms could be exploited as constitutive new markers of fibrosis evolution. The results highlight the possibility of using modulators of ERAP1 to generate a protective immune response against chronic HCV infection. KEY MESSAGES: What is known Several ERAP1 polymorphisms are associated with autoimmune diseases and cancer. ERAP1 trims peptides to HLA class I presentation. What is new here ERAP1 polymorphisms are associated with fibrogenesis. The ERAP1 polymorphisms genotype could help us in clinical management of patients. Potential translational impact The use of modulators of ERAP1 could generate a protective response depending on SNPs.

Immunomodulation of the Natural Killer Cell Phenotype and Response during HCV Infection

Hepatitis C virus (HCV) infection develops into chronic hepatitis in over two-thirds of acute infections. While current treatments with direct-acting antivirals (DAAs) achieve HCV eradication in >95% of cases, no vaccine is available and re-infection can readily occur. Natural killer (NK) cells represent a key cellular component of the innate immune system, participating in early defence against infectious diseases, viruses, and cancers. When acute infection becomes chronic, however, NK cell function is altered. This has been well studied in the context of HCV, where changes in frequency and distribution of NK cell populations have been reported. While activating receptors are downregulated on NK cells in both acute and chronic infection, NK cell inhibiting receptors are upregulated in chronic HCV infection, leading to altered NK cell responsiveness. Furthermore, chronic activation of NK cells following HCV infection contributes to liver inflammation and disease progression through enhanced cytotoxicity. Consequently, the NK immune response is a double-edged sword that is a significant component of the innate immune antiviral response, but persistent activation can drive tissue damage during chronic infection. This review will summarise the role of NK cells in HCV infection, and the changes that occur during HCV therapy.

Presence of donor-encoded centromeric KIR B content increases the risk of infectious mortality in recipients of myeloablative, T-cell deplete, HLA-matched HCT to treat AML

The reported influence of donor Killer-cell Immunoglobulin-like Receptor (KIR) genes on the outcomes of haematopoietic cell transplantation (HCT) are contradictory, in part due to diversity of disease, donor sources, era and conditioning regimens within and between different studies. Here, we describe the results of a retrospective clinical analysis establishing the effect of donor KIR motifs on the outcomes of 119 HLA-matched, unrelated donor HCT for adult acute myeloid leukaemia (AML) using myeloablative conditioning (MAC) in a predominantly T-cell deplete (TCD) cohort. We observed that HCT involving donors with at least one KIR B haplotype were more likely to result in non-relapse mortality (NRM) than HCT involving donors with two KIR A haplotypes (p = 0.019). Upon separation of KIR haplotypes into their centromeric (Cen) and telomeric (Tel) motif structures, we demonstrated that the Cen-B motif was largely responsible for this effect (p = 0.001). When the cause of NRM was investigated further, infection was the dominant cause of death (p = 0.006). No evidence correlating donor KIR B haplotype with relapse risk was observed. The results from this analysis confirm previous findings in the unrelated, TCD, MAC transplant setting and imply a protective role for donor-encoded Cen-A motifs against infection in allogeneic HCT recipients.

The Evolutionary Arms Race between Virus and NK Cells: Diversity Enables Population-Level Virus Control

Viruses and natural killer (NK) cells have a long co-evolutionary history, evidenced by patterns of specific NK gene frequencies in those susceptible or resistant to infections. The killer immunoglobulin-like receptors (KIR) and their human leukocyte antigen (HLA) ligands together form the most polymorphic receptor-ligand partnership in the human genome and govern the process of NK cell education. The KIR and HLA genes segregate independently, thus creating an array of reactive potentials within and between the NK cell repertoires of individuals. In this review, we discuss the interplay between NK cell education and adaptation with virus infection, with a special focus on three viruses for which the NK cell response is often studied: human immunodeficiency virus (HIV), hepatitis C virus (HCV) and human cytomegalovirus (HCMV). Through this lens, we highlight the complex co-evolution of viruses and NK cells, and their impact on viral control.

Genetic Factors That Affect Spontaneous Clearance of Hepatitis C or B Virus, Response to Treatment, and Disease Progression

Hepatitis C virus (HCV) and hepatitis B virus (HBV) infections can lead to cirrhosis, end-stage liver disease, and hepatocellular carcinoma. Over the past decade, studies of individuals infected with these viruses have established genetic associations with the probability of developing a chronic infection, risk of disease progression, and likelihood of treatment response. We review genetic and genomic methods that have been used to study risk of HBV and HCV infection and patient outcomes. For example, genome-wide association studies have linked a region containing the interferon lambda genes to spontaneous and treatment-induced clearance of HCV. We review the genetic variants associated with HCV and HBV infection, and how these variants affect specific expression or activities of their products. Further studies of these variants could provide insights into risk factors for and mechanisms of chronic infection and disease progression, as well as new strategies for treatment.

NK cells in liver homeostasis and viral hepatitis

As an important member of the innate immune system, natural killer (NK) cells are well known for their rapid and efficient immune responses against infectious agents and tumors. NK cells are widely distributed throughout the body and are particularly enriched within the liver, where they display unique phenotypic and functional properties, playing important roles in various liver diseases. Herein, we present an overview of liver NK cell properties with regard to phenotype, function, and subset composition at steady state, and we also summarize the complex reciprocal interactions between liver NK cells and other cell types within the local environment of the liver. We also provide an overview of recent advances demonstrating the roles of NK cells in viral hepatitis, including a discussion of NK cell altered states and their beneficial versus harmful effects during hepatitis B virus and hepatitis C virus infection.

Pharmacogenetics and the treatment of HIV-/HCV-coinfected patients

This review will summarize the role of pharmacogenetics in the natural history of hepatitis C, particularly in patients with HIV/HCV and will take the perspective of pharmacogenetics and its influence on the response to antiviral therapy and the susceptibility to develop adverse effects. This review will also devote a section to host genetics in other clinical situations, such as disease progression and acute HCV infection, which may determine whether treatment of HIV-/HCV-coinfected patients is implemented or deferred.

KIR2DL2 combined with HLA-C1 confers risk of hepatitis C virus-related hepatocellular carcinoma in younger patients

Killer cell immunoglobulin-like receptors (KIRs) are involved in the activation and inhibition of natural killer cells. Although combinations of KIRs and HLA have been associated with spontaneous and treatment-induced clearance of hepatitis C virus (HCV) infection, their roles are not fully understood in the context of hepatocellular carcinoma (HCC) development. We enrolled 787 consecutive patients with chronic HCV infection, which included 174 cases of HCC, and 325 healthy subjects to clarify the involvement of HLA-Bw and C, KIRs, and major histocompatibility complex class I chain-related gene A (MICA) gene polymorphisms (rs2596542 and rs1051792) in chronic HCV infection and HCV-related HCC. We observed a significant association with chronic hepatitis C susceptibility for HLA-Bw4 (P = 0.00012; odds ratio [OR] = 1.66) and significant protective associations for HLA-C2 and KIR2DL1-HLA-C2 (both P = 0.00099; OR = 0.57). When HCC patients were stratified into younger (<65 years) and older (≥65 years) groups, the frequencies of KIR2DL2-HLA-C1 and KIR2DS2-HLA-C1 (P = 0.008; OR = 2.89 and P = 0.015; OR = 2.79, respectively) as well as rs2596542 and rs1051792 (P = 0.020; OR = 2.17 and P = 0.038; OR = 2.01, respectively) were significantly higher in younger patients. KIR2DL2-HLA-C1 (OR = 2.75; 95% confidence interval: 1.21-6.21, P = 0.015) and rs1051792 (OR = 2.48; 95% confidence interval: 1.23-4.98, P = 0.011) were independently associated with HCC development in younger patients. These results suggest that KIR2DL2-HLA-C1 and rs1051792 may represent molecular biomarkers to identify early onset HCV-related HCC.

Association of killer cell immunoglobulin-like receptors with spontaneous clearance of hepatitis C virus in the Chinese population

BACKGROUND

Natural killer (NK) cells are critical components in innate immune response to viral infection. Killer cell immunoglobulin-like receptors (KIRs) are involved in regulating the balance of activation or inhibitory function of NK cells. However, the association of KIRs with the spontaneous clearance of hepatitis C virus (HCV) remains unclear in the Chinese population.

STUDY DESIGN AND METHODS

A total of 407 HCV-seropositive voluntary blood donors were recruited, including 203 with spontaneous viral clearance and 204 with chronic infection. The presence of KIR genes was detected individually by polymerase chain reaction with sequence-specific primers. Data of HLA and interleukin-28B (IL28B) genotypes were extracted from our previous study.

RESULTS

Our results showed that KIR2DL2, 2DS2, 2DL2/2DL3, and 2DL5A-/2DL5B+ were more frequent in subjects with HCV clearance than those with chronic infection (odds ratio [OR], 1.640, p = 0.034; OR, 1.664, p = 0.032; OR, 1.636, p = 0.040; and OR, 2.601, p = 0.012, respectively). Multivariate logistic regression analysis showed that KIR2DL5A-/2DL5B+ associated with HCV clearance (OR, 2.448, p = 0.027), independent of sex, IL28B, and other KIRs. In contrast, KIR2DL3/2DL3 (OR, 0.610, p = 0.034) as well as 2DL3/2DL3+HLA-C1 or C1C1 (OR, 0.580, p = 0.017; and OR, 0.639, p = 0.025, respectively) was found associated with chronic HCV infection. The presence of the homozygous KIR2DL3 with or without its HLA ligand increased the OR of developing chronic HCV infection in the context of IL28B.

CONCLUSIONS

In this study we identified KIR2DL5A-/2DL5B+ associated with HCV spontaneous clearance, while KIR2DL3/2DL3, 2DL3/2DL3+HLA-C1, or C1C1 associated with chronic infection. Our study highlighted the fact that the roles of KIR and KIR-HLA contributed to the control of HCV infection by innate immune responses.

IL-12 and IL-15 induce the expression of CXCR6 and CD49a on peripheral natural killer cells

INTRODUCTION

Murine hepatic NK cells exhibit adaptive features, with liver-specific adhesion molecules CXCR6 and CD49a acting as surface markers.

METHODS

We investigated human liver-resident CXCR6+ and CD49a+ NK cells using RNA sequencing, flow cytometry, and functional analysis. We further assessed the role of cytokines in generating NK cells with these phenotypes from the peripheral blood.

RESULTS

Hepatic CD49a+ NK cells could be induced using cytokines and produce high quantities of IFNγ and TNFα, in contrast to hepatic CXCR6+ NK cells. RNA sequencing of liver-resident CXCR6+ NK cells confirmed a tolerant immature phenotype with reduced expression of markers associated with maturity and cytotoxicity. Liver-resident double-positive CXCR6 + CD49a+ hepatic NK cells are immature but maintain high expression of Th1 cytokines as observed for single-positive CD49a+ NK cells. We show that stimulation with activating cytokines can readily induce upregulation of both CD49a and CXCR6 on NK cells in the peripheral blood. In particular, IL-12 and IL-15 can generate CXCR6 + CD49a+ NK cells in vitro from NK cells isolated from the peripheral blood, with comparable phenotypic and functional features to liver-resident CD49a+ NK cells, including enhanced IFNγ and NKG2C expression.

CONCLUSION

IL-12 and IL-15 may be key for generating NK cells with a tissue-homing phenotype and strong Th1 cytokine profile in the blood, and links peripheral activation of NK cells with tissue-homing. These findings may have important therapeutic implications for immunotherapy of chronic liver disease.

Higher expression of inhibitory CD158b and CD158e NK cell receptor and age predicts treatment response in children with chronic hepatitis C

Treatment with pegylated interferon-α and ribavirin (PEG-IFN/RBV) is the only choice for chronic hepatitis C (CHC) in children. Natural killer (NK) cells were described to play a vital role in CHC. The aim of this study was to analyze the expression of peripheral blood NK cell receptors in their relation to PEG-IFN/RBV treatment response. Study included 26 children with CHC-13 boys, age range 13.42 ± 3.28 years. Blood for biochemical, virological and cytometric testing was taken for evaluation prior to the antiviral treatment. NK cell receptors were detected by flow cytometry and the results were presented as proportion of cells and mean fluorescence intensity (MFI). Therapy consisted of PEG-IFNα-2b (60 μg/m² s.c 1×/week) and RBV (15 mg/kg p.o. daily). Treatment duration was response-related and varied from 12 to 72 weeks. Rapid virological response (RVR) was evaluated in the 4th week and sustained virological response (SVR) 6 months after completion of the therapy. RVR children were younger (11.67 ± 3.74 vs 15.35 ± 2.42; p = 0.001) and displayed higher CD158b (3.58 ± 0.16 vs 3.45 ± 0.13; p = 0.038) and CD158e expression (4.33 ± 0.21 vs 4.03 ± 0.16; p = 0.039). Density of CD158b (logMFI = 3.68 ± 0.22 vs 3.36 ± 0.16; p = 0.036) and CD158e expression was significantly higher (4.37 ± 0.14 vs 4.12 ± 0.21; p = 0.046) and NKG2D expression significantly lower (97.50 ± 3.46 vs 94.92 ± 5.93; p = 0.049) in SVR children. SVR children were also significantly younger (12.40 ± 3.66 vs 15.13 ± 2.83; p = 0.003). Significance of the age of patients, and expression of CD158b and CD158e were confirmed in univariate and multivariate analysis. Age of patients is negatively related to RVR and SVR. NK cell phenotype with higher expression density of CD158b and CD158e receptor was a positive predictor of SVR.

IL-28B Genetic Variants Determine the Extent of Monocyte-Induced Activation of NK Cells in Hepatitis C

BACKGROUND

Immuno-genetic studies suggest a functional link between NK cells and λ-IFNs. We recently showed that NK cells are negative for the IFN-λ receptor IFN-λR1 and do not respond to IFN-λ, suggesting a rather indirect association between IL-28B genotype and NK cell activity.

METHODS

A total of 75 HCV(+) patients and 67 healthy controls were enrolled into this study. IL-28B (rs12979860) and IFNL-4 (rs368234815) genotypes were determined by rtPCR. Total PBMC, monocytes, and NK cells were stimulated with IL-29, the TLR-7/8 agonist R848, or a combination of both. NK cell IFN-γ response was analysed by FACS. IL-12 and IL-18 secretion of monocytes was studied by ELISA. In blocking experiments anti-IL-12/anti-IL-18 were used.

RESULTS

Following stimulation of total PBMCs with R848 we found NK cell IFN- γ responses to vary with the IL-28B genotype, with carriers of a T/T genotype displaying the lowest frequency of IFN-γ(+)NK cells. When isolated NK cells were studied no such associations were observed, indicating an indirect association between IL-28B genotype and NK cell activity. Accordingly, we found R848-stimulated monocytes of patients with a T/T genotype to be significantly less effective in triggering NK cell IFN- γ production than monocytes from carriers of a non-T/T genotype. In line with these findings we observed monocytes from T/T patients to secrete significantly lower concentrations of IL-12 than monocytes from non-T/T individuals.

CONCLUSIONS

Our data indicate that monocytes from carriers of an IL-28B T/T genotype display a reduced ability to stimulate NK cell activity and, thus, provide a link between IL-28B genotype and NK functions.

Significant association of the KIR2DL3/HLA-C1 genotype with susceptibility to Crohn's disease

We aimed to analyze the possible association of KIR/HLA-C genotypes with the susceptibility to Crohn's disease (CD) in a Spanish population. A total of 125 patients with CD and 339 healthy controls were selected for this study. KIR and HLA-C typing were developed by sequence-specific oligonucleotide probing. We found that the centromeric A/A genotype and HLA-C1 combination was significantly increased in CD patients (P<10(-3)). The KIR2DL3/2DL3 genotype was significantly increased in CD patients (P<0.0005). Moreover, we also observed a highly significant increase of KIR2DL3-HLA-C1 homozygosis in CD patients (P<0.0005). Our results confirm the relevance of the KIR2DL2/KIR2DL3 genes and their interaction with HLA-C to CD. We show that the contribution of the KIR genes to CD susceptibility extends beyond the association with individual KIRs, with an imbalance between activating and inhibitory KIR genes seeming to influence the susceptibility to CD.

The effect of KIR2D-HLA-C receptor-ligand interactions on clinical outcome in a HIV-1 CRF01_AE-infected Thai population

OBJECTIVE

Class I human leukocyte antigen (HLA) alleles interact with both cytotoxic T lymphocytes through their T-cell receptors, and natural killer cells through their killer immunoglobulin-like receptors (KIRs). Compared with the reported protective effect of KIR3DL1/S1-HLA-Bw4 interactions in HIV-infected patients, the effect of KIR2D-HLA-C combinations on HIV control remains unclear. Here, we investigate the effect of KIR2D-HLA-C combinations on HIV disease progression.

DESIGN

We performed a cross-sectional and longitudinal analysis of a Thai HIV cohort.

METHODS

Two hundred and nine HIV-1 CRF01_AE-infected, treatment-naive Thai patients (CD4 T-cell counts of >200/μl) and 104 exposed seronegatives were studied. The effect of KIR-HLA receptor-ligand combinations on viral transmission and survival rate was statistically analyzed.

RESULTS

We found the following results: higher frequency of patients expressing both KIR2DL3 and HLA-C1 among infected patients compared with exposed seronegative (odds ratio 4.8, P = 0.004), higher viral load in patients expressing HLA-C1 with KIR2DL3 compared with those without this receptor-ligand combination (median 4.8 vs. 4.2 log copies/ml, P = 0.033), higher numbers of KIR2DL3-HLA-C1 interactions was associated with a higher viral load (β = 0.13, P = 0.039 by linear regression model), and higher mortality rate in carriers of the KIR2DL3-HLA-C1 combination (adjusted hazard ratio 1.9, P = 0.012 by Cox hazard model).

CONCLUSION

We have identified a deleterious effect of the KIR2DL3-HLA-C1 receptor-ligand combination on HIV clinical outcomes in a Thai cohort. Further investigation into mechanisms underlying this susceptibility may aid the understanding of the role of natural killer cells in HIV disease control and pathogenesis.

Innate and adaptive genetic pathways in HCV infection

Infection with hepatitis C virus (HCV) leads to a wide spectrum of clinical manifestations. This heterogeneity is underpinned by the host immune response and the genetic factors that govern it. Polymorphisms affecting both the innate and adaptive immunity determine the outcome of exposure. However the innate immune system appears to play a greater role in determining treatment-associated responses. Overall the effects of IFNL3/4 appear dominant over other polymorphic genes. Understanding how host genetics determines the disease phenotype has not been as intensively studied. This review summarizes our current understanding of innate and adaptive immunogenetic factors in the outcome of HCV infection. It focuses on how they relate to resolution and the progression of HCV-related liver disease, in the context of current and future treatment regimes.

Inherent transcriptional signatures of NK cells are associated with response to IFNα + rivabirin therapy in patients with Hepatitis C Virus

BACKGROUND

Differences in the expression of Natural Killer cell receptors have been reported to reflect divergent clinical courses in patients with chronic infections or tumors. However, extensive molecular characterization at the transcriptional level to support this view is lacking. The aim of this work was to characterize baseline differences in purified NK cell transcriptional activity stratified by response to treatment with PEG-IFNα/RBV in patients chronically infected with HCV.

METHODS

To this end we here studied by flow cytometer and gene expression profile, phenotypic and transcriptional characteristics of purified NK cells in patients chronically infected with HCV genotype-1 virus who were subsequently treated with PEG-IFNα/RBV. Results were further correlated with divergent clinical response obtained after treatment.

RESULTS

The pre-treatment transcriptional patterns of purified NK cells from patients subsequently undergoing a sustained virologic response (SVR) clearly segregated from those of non-responder (NR) patients. A set of 476 transcripts, including molecules involved in RNA processing, ubiquitination pathways as well as HLA class II signalling were differently expressed among divergent patients. In addition, treatment outcome was associated with differences in surface expression of NKp30 and NKG2D. A complex relationship was observed that suggested for extensive post-transcriptional editing. Only a small number of the NK cell transcripts identified were correlated with chronic HCV infection/replication indicating that inherent transcriptional activity prevails over environment effects such as viral infection.

CONCLUSIONS

Collectively, inherent/genetic modulation of NK cell transcription is involved in setting the path to divergent treatment outcomes and could become useful to therapeutic advantage.

Killer cell immunoglobulin-like receptor (KIR) gene diversity in a population naturally exposed to malaria in Porto Velho, Northern Brazil

Killer cell immunoglobulin-like receptors (KIR) are expressed mainly in natural killer cells and specifically recognize human leukocyte antigen (HLA) class I molecules. The repertoire of KIR genes and KIR-HLA pairs is known to play a key role in the susceptibilities to and the outcomes of several diseases, including malaria. The aim of this study was to investigate the distribution of KIR genes, KIR genotypes and KIR-HLA pair combinations in a population naturally exposed to malaria from Brazilian Amazon. All 16 KIR genes investigated were present in the studied population. Overall, 46 KIR genotypes were defined. The two most common genotypes in the Porto Velho communities, genotypes 1 and 2, were present at similar frequencies as in the Americas. Principal component analysis based on the frequencies of the KIR genes placed the Porto Velho population closer to the Venezuela Mestizos, USA California hispanic and Brazil Paraná Mixed in terms of KIR gene frequencies. This analysis highlights the multi-ethnic profile of the Porto Velho population. Most of the individuals were found to have at least one inhibitory KIR-HLA pair. Seventy-five KIR-HLA pair combinations were identified. The KIR-2DL2/3_HLA-C1, KIR3DL1_HLA-Bw4 and KIR2DL1_HLA-C2 pairs were the most common. There was no association between KIR genes, KIR genotypes or KIR-HLA pair combinations and malaria susceptibility in the studied population. This is the first report on the distribution of KIR and known HLA ligands in the Porto Velho population. Taken together, these results should provide baseline information that will be relevant to population evolutionary history, malaria and other diseases studies in populations of the Brazilian Amazon.

Contribution of genes for killer cell immunoglobulin-like receptors (KIR) to the susceptibility to chronic hepatitis C virus infection and to viremia

BACKGROUND

Natural killer (NK) cells are an important element of innate immunity against viruses, although their numbers decrease in the liver during chronic HCV infection. NK cells express a large panel of inhibitory and activating receptors. The most polymorphic of these are killer cell immunoglobulin-like receptors (KIRs) which are encoded by multiple genes that may be present or absent in given individuals depending on their genotype. This variability results in differential susceptibility to viral infections and diseases, including HCV infection and its consequences.

AIMS AND METHODS

The aim of this study was to test whether chronical infection with HCV and the viremia levels are associated with any KIR gene in the Polish population. We typed 301 chronically HCV-infected patients and 425 non-infected healthy individuals for the presence or absence of KIR genes and their ligands, HLA-C C1 and C2 groups as well as HLA-B and HLA-A Bw4-positive alleles.

RESULTS

We found that males, but not females, possessing KIR2DS2 and KIR2DL2 genes had a 1.7 higher probability to become chronically HCV-infected than males negative for these genes (p=0.0213). In accord with this, centromeric B region, containing KIR2DS2 and KIR2DL2 genes, was also associated with chronic HCV infection in males. In addition, patients of both genders possessing KIR2DS3 but not KIR2DS5 gene exhibited, on average, 2.6 lower level of viremia than HCV-infected individuals with other genotypes (p=0.00282). This was evident in those infected at a young age. KIR2DS3-positive patients also had lower mean levels of bilirubin than KIR2DS3-negative ones (p=0.02862).

CONCLUSION

Our results suggest a contribution of the KIR2DS2 and KIR2DL2 genes (cenB haplotype) to the susceptibility to chronic HCV infection, and an association of the KIR2DS3 gene in the absence of KIR2DS5 with low viremia levels.

Peptide selectivity discriminates NK cells from KIR2DL2- and KIR2DL3-positive individuals

Natural killer cells are controlled by peptide selective inhibitory receptors for MHC class I, including the killer cell immunoglobulin‐like receptors (KIRs). Despite having similar ligands, KIR2DL2 and KIR2DL3 confer different levels of protection to infectious disease. To investigate how changes in peptide repertoire may differentially affect NK cell reactivity, NK cells from KIR2DL2 and KIR2DL3 homozygous donors were tested for activity against different combinations of strong inhibitory (VAPWNSFAL), weak inhibitory (VAPWNSRAL), and antagonist peptide (VAPWNSDAL). KIR2DL3‐positive NK cells were more sensitive to changes in the peptide content of MHC class I than KIR2DL2‐positive NK cells. These differences were observed for the weakly inhibitory peptide VAPWNSRAL in single peptide and double peptide experiments (p < 0.01 and p < 0.03, respectively). More significant differences were observed in experiments using all three peptides (p < 0.0001). Mathematical modeling of the experimental data demonstrated that VAPWNSRAL was dominant over VAPWNSFAL in distinguishing KIR2DL3‐ from KIR2DL2‐positive donors. Donors with different KIR genotypes have different responses to changes in the peptide bound by MHC class I. Differences in the response to the peptide content of MHC class I may be one mechanism underlying the protective effects of different KIR genes against infectious disease.

Exploration of genetically determined resistance against hepatitis C infection in high-risk injecting drug users

Genetic resistance to specific infections is well recognized. In hepatitis C virus (HCV) infection, genetic polymorphisms in IL-28B and the killer cell immunoglobulin-like receptors (KIR) and their HLA class I ligands have been shown to affect clearance of the virus following infection. There are limited data regarding resistance to established HCV infection. Reliable quantification of repeated exposure in high-risk populations, such as injecting drug users (IDU), is a key limitation of previous studies of resistance. Behavioural data and DNA from IDU (n = 210) in the Hepatitis C Incidence and Transmission Study in prisons (HITS-p) cohort were genotyped for polymorphisms in: IL-28B, peptidyl-prolyl isomerase A (PPIA), HLA-C and KIR2. To quantify risk, a composite risk index based on factors predictive of incident HCV infection was derived. Logistic regression analysis revealed the risk index was strongly associated with incident HCV infection (P < 0.0001). The upper tertile of the uninfected individuals had risk indices comparable to the incident cases, but remained uninfected. There were no significant differences in the frequencies of IL-28B or PPIA polymorphisms between these exposed-uninfected cases, or in the frequencies of KIR2-DL3, HLA-C1, or their combination. A framework for the investigation of genetic determinants of resistance to HCV infection has been developed. Several candidate gene associations were investigated and excluded. Further investigation of genetic determinants of resistance to HCV infection is warranted.

KIR3DL1-HLA-Bw4 combination and IL28B polymorphism predict response to Peg-IFN and ribavirin with and without telaprevir in chronic hepatitis C

Natural killer cells play a key role in the immune control of viral infections. Killer immunoglobulin-like receptors (KIRs) regulate natural killer cell activation and inhibition through the recognition of their cognate HLA class I ligands. We assessed the predictive factors of a sustained virological response (SVR) in 200 Japanese patients with chronic genotype 1b hepatitis C who were treated with telaprevir (TVR), pegylated-interferon-α2b (PEG-IFN), and ribavirin (RBV) triple therapy (92 patients) or PEG-IFN/RBV therapy alone (108 patients). Sixteen KIR genotypes, HLA-A, -B and -C ligands, and an interleukin (IL) 28B polymorphism (rs8099917) were analyzed. We observed that triple therapy, white blood cell count, hemoglobin value, hepatitis C viral load, a rapid virological response (RVR), IL28B TT genotype, and KIR3DL1-HLA-Bw4 genotype were associated with an SVR. In multivariate regression analysis, we identified an RVR (P < 0.000001; odds ratio [OR] = 20.95), the IL28B TT genotype (P = 0.00014; OR = 5.53), and KIR3DL1-HLA-Bw4 (P = 0.004, OR = 3.42) as significant independent predictive factors of an SVR. In conclusion, IL28B and KIR3DL1/HLA-Bw4 are independent predictors of an SVR in Japanese patients infected with genotype 1b HCV receiving TVR/PEG-IFN/RBV or PEG-IFN/RBV therapy.

Diversity of killer cell immunoglobulin-like receptor (KIR) genotypes and KIR2DL2/3 variants in HCV treatment outcome

The aim of this study was to analyse the distribution of KIR haplotypes and the KIR2DL2/3 alleles in chronic HCV-infected patients in order to establish the influence on the response to pegylated interferon plus ribavirin classical treatment. The alleles study of previously associated KIR2DL2/3 showed that KIR2DL2*001 was more frequent in non-SVR (NSVR) (42.2% vs. 27.5%, p<0.05) and KIR2DL3*001 was associated with sustained viral response (SVR) (41.6% vs. 61.2%, p<0.005). The KIR2DL3*001-HLA-C1 association was also significant (24.5% vs. 45.7%, p<0.001). From the frequencies of KIR obtained, 35 genotypes were assigned on the basis of previous studies. The centromeric A/A genotype was more frequent in SVR (44.1% vs. 34.5%, p<0.005) and the centromeric B/B genotype was found to be significantly more frequent in NSVR (20.9% vs. 11.2%, p<0.001). The logic regression model showed the importance of KIR genes in predicting the response to combined treatment, since the positive predictive value (PPV) was improved (from 55.9% to 75.3%) when the analysis of KIR was included in addition to the IFNL3 rs12979860 polymorphism. The study of KIR receptors may be a powerful tool for predicting the combined treatment response in patients with chronic HCV infection in association with the determination of IFNL3 polymorphism.

Natural cytotoxicity receptor-dependent natural killer cytolytic activity directed at hepatitis C Virus (HCV) is associated with liver inflammation, African American race, IL28B genotype, and response to pegylated interferon/ribavirin therapy in chronic HCV infection

BACKGROUND

Natural killer (NK) cells are implicated in the pathogenesis of hepatitis C virus (HCV) infection and outcome of interferon (IFN)-α based therapy, although mechanisms remain unclear.

METHODS

To evaluate NK ability to control HCV infection, we analyzed healthy donor and HCV-infected donor NK-cell cytolytic activity directed at HCV-infected target cells.

RESULTS

HCV-infected subjects' natural cytotoxicity receptor (NCR)-dependent NK-cell cytolytic activity directed at HCV-infected and uninfected Huh7.5 target cells was greater than that of cells from healthy donors, and this localized to the African American subset. However, IFN-α-enhanced NK cytolytic function was lower in HCV-infected subjects, again localized mainly to the African American subset. Additionally, whereas HCV-infected Huh7.5 cells were more readily targeted than uninfected cells, the selectivity of cytolytic activity for infected targets was lower during HCV infection and after IFN-α stimulation, and lower selectivity was in part attributable to greater NKp46 expression. Furthermore, cytolytic activity was associated with higher serum aspartate aminotransferase, rs12979860 IL28B genotype, and in vivo response to pegylated IFN/ribavirin therapy.

CONCLUSIONS

These data indicate that during chronic HCV infection, race-associated increase in NCR expression and IL28B-associated cytolytic activity may participate in host response to IFN-α-containing HCV therapy.

Long-term effect on natural killer cells by interferon-α therapy on the outcomes of HCV infection

Natural killer (NK) cells act as innate immune cells against hepatitis C virus (HCV) infection. Interferon-α (IFN-α) and ribavirin are the standard treatments for patients with HCV infection. This study is aimed at investigating the dynamic changes in the frequency of different subsets of NK cells following treatment in xx chronic hepatitis C (CHC) patients. CHC patients were treated with peg-IFN or IFN-α, and followed up for 72 weeks. The frequency of different subsets of NK in CHC patients was determined longitudinally by flow cytometry. Treatment with the standard therapy increased the percentages of NKp30(+), NKp46(+), and CD107a(+) NK cells, which were positively correlated with the declining of serum HCV-RNA, but not IFN-γ(+) NK cells. NKG2A(+) and KIR2DL3(+) NK cells were associated with an early virological response in CHC patients. Treatment with IFN-α adjusts the balance of activated receptors and inhibitory receptors and enhances the cytotoxic activity of NK cells. Therefore, measuring NK subsets may be valuable for therapeutic responses in CHC patients.

Individualization of chronic hepatitis C treatment according to the host characteristics

Hepatitis C virus (HCV) infection is a global health problem that affects more than 170 million people worldwide. It is a major cause of cirrhosis and hepatocellular carcinoma, making the virus the most common cause of liver failure and transplantation. The standard-of-care treatment for chronic hepatitis C (CHC) has been changed during the last decade and direct acting antiviral drugs have already been used. Besides, understanding of the pathogenesis of CHC has evolved rapidly during the last years and now several host factors are known to affect the natural history and response to treatment. Recent genome-wide association studies have shown the important role of interleukin-28B and inosine triphosphatase in HCV infection. The present review article attempts to summarize the current knowledge on the role of host factors towards individualization of HCV treatment.

HTLV-1/-2 and HIV-1 co-infections: retroviral interference on host immune status

The human retroviruses HIV-1 and HTLV-1/HTLV-2 share similar routes of transmission but cause significantly different diseases. In this review we have outlined the immune mediated mechanisms by which HTLVs affect HIV-1 disease in co-infected hosts. During co-infection with HIV-1, HTLV-2 modulates the cellular microenvironment favoring its own viability and inhibiting HIV-1 progression. This is achieved when the HTLV-2 proviral load is higher than that of HIV-1, and thanks to the ability of HTLV-2 to: (i) up-regulate viral suppressive CCL3L1 chemokine expression; (ii) overcome HIV-1 capacity to activate the JAK/STAT pathway; (iii) reduce the activation of T and NK cells; (iv) modulate the host miRNA profiles. These alterations of immune functions have been mainly attributed to the effects of the HTLV-2 regulatory protein Tax and suggest that HTLV-2 exerts a protective role against HIV-1 infection. Contrary to HIV-1/HTLV-2, the effect of HIV-1/HTLV-1 co-infection on immunological and pathological conditions is still controversial. There is evidence that indicates a worsening of HIV-1 infection, while other evidence does not show clinically relevant effects in HIV-positive people. Possible differences on innate immune mechanisms and a particularly impact on NK cells are becoming evident. The differences between the two HIV-1/HTLV-1 and HIV-1/HTLV-2 co-infections are highlighted and further discussed.

KIR, HLA, and IL28B variant predict response to antiviral therapy in genotype 1 chronic hepatitis C patients in Japan

Natural killer cell responses play a crucial role in virus clearance by the innate immune system. Although the killer immunoglobulin-like receptor (KIR) in combination with its cognate human leukocyte antigen (HLA) ligand, especially KIR2DL3-HLA-C1, is associated with both treatment-induced and spontaneous clearance of hepatitis C virus (HCV) infection in Caucasians, these innate immunity genes have not been fully clarified in Japanese patients. We therefore investigated 16 KIR genotypes along with HLA-B and -C ligands and a genetic variant of interleukin (IL) 28B (rs8099917) in 115 chronic hepatitis C genotype 1 patients who underwent pegylated-interferon-α2b (PEG-IFN) and ribavirin therapy. HLA-Bw4 was significantly associated with a sustained virological response (SVR) to treatment (P = 0.017; odds ratio [OR] = 2.50, ), as was the centromeric A/A haplotype of KIR (P = 0.015; OR 3.37). In contrast, SVR rates were significantly decreased in patients with KIR2DL2 or KIR2DS2 (P = 0.015; OR = 0.30, and P = 0.025; OR = 0.32, respectively). Multivariate logistic regression analysis subsequently identified the IL28B TT genotype (P = 0.00009; OR = 6.87, 95% confidence interval [CI] = 2.62 - 18.01), KIR2DL2/HLA-C1 (P = 0.014; OR = 0.24, 95% CI = 0.08 - 0.75), KIR3DL1/HLA-Bw4 (P = 0.008, OR = 3.32, 95% CI = 1.37 - 8.05), and white blood cell count at baseline (P = 0.009; OR = 3.32, 95% CI = 1.35 - 8.16) as independent predictive factors of an SVR. We observed a significant association between the combination of IL28B TT genotype and KIR3DL1-HLA-Bw4 in responders (P = 0.0019), whereas IL28B TT along with KIR2DL2-HLA-C1 was related to a non-response (P = 0.0067). In conclusion, combinations of KIR3DL1/HLA-Bw4, KIR2DL2/HLA-C1, and a genetic variant of the IL28B gene are predictive of the response to PEG-IFN and ribavirin therapy in Japanese patients infected with genotype 1b HCV.

HLA and killer immunoglobulin-like receptor genes as outcome predictors of hepatitis C virus-related hepatocellular carcinoma

PURPOSE

We evaluated the impact of the killer immunoglobulin-like receptors (KIR) of natural killer (NK) cells and of their HLA ligands over the clinical outcome of hepatitis C virus (HCV)-related hepatocellular carcinoma after curative treatment by either surgical resection or radiofrequency thermal ablation (RTA).

EXPERIMENTAL DESIGN

Sixty-one consecutive patients with HCV-related hepatocellular carcinoma underwent KIR genotyping and HLA typing. A phenotypic/functional characterization of NK cells was carried out in patients with different KIR/KIR-ligand genotype.

RESULTS

Activating KIR2DS5 was associated with significantly longer time to recurrence (TTR) and overall survival (OS; P < 0.03 each). Homozygous HLA-C1 (P < 0.02) and HLA-Bw4I80 (P < 0.05) were expressed by patients with significantly better OS, whereas HLA-C2 (P < 0.02) and HLA-Bw4T80 (P < 0.01) were associated with a worse OS. Multivariate analysis identified as parameters independently related to TTR the type of treatment (surgical resection vs. RTA; P < 0.03) and HLA-C1 (P < 0.03), whereas only KIR2DS5 was an independent predictor of longer OS (P < 0.05). Compound KIR2DL2-C1 and KIR3DS1-Bw4T80 genotypes were associated with better TTR (P < 0.03) and worse OS (P = 0.02), respectively. A prevalent cytotoxic (CD56(dim)) NK phenotype was detected in patients with both longer TTR and OS. Cytotoxic capacity measured by upregulation of CD107a was significantly higher in subjects with HLA-C1 alone or combined with KIR2DL2/KIR2DL3.

CONCLUSIONS

These results support a central role of NK cells in the immune response against hepatocellular carcinoma, providing a strong rationale for therapeutic strategies enhancing NK response and for individualized posttreatment monitoring schemes.

Absence of activating killer immunoglobulin-like receptor genes combined with hepatitis C viral genotype is predictive of hepatocellular carcinoma

Killer immunoglobulin-like receptors and their human leukocyte antigen class I ligands have a critical role in natural killer cell response to viral pathogens and tumors. To investigate whether killer immunoglobulin-like receptor genes could influence the chronic course of hepatitis C virus infection and/or progression to hepatocellular carcinoma we retrospectively analyzed a cohort of 228 patients transplanted for hepatitis C virus-induced cirrhotic end stage liver disease, combined or not with hepatocellular carcinoma. We found that patients completely lacking activating killer immunoglobulin-like receptor genes had a high risk of developing hepatocellular carcinoma. Hepatitis C viral genotype and viral load are other risk factors that can influence the course of chronic hepatitis C virus infection. In our study, the risk conferred by hepatitis C viral genotypes was enhanced in patients lacking activating killer immunoglobulin-like receptors. These results point to an important role for activating killer immunoglobulin-like receptors in the control of hepatitis C virus infection and progression to hepatocellular carcinoma. In clinical practice, assessment of killer immunoglobulin-like receptor and hepatitis C viral genotype combinations should allow for more accurate monitoring of patients with chronic hepatitis C virus infection.

KIR gene mismatching and KIR/C ligands in liver transplantation: consequences for short-term liver allograft injury

BACKGROUND

Killer immunoglobulin-like receptors (KIRs) bind human leukocyte antigen (HLA) class-I (HLA-I) ligands and regulate functions of natural killer cells and subsets of T cells. KIR/HLA-I interactions allow predicting natural killer cell alloreactivity in hematopoietic stem cell transplantation and in HLA-compatible kidney transplants, but its meaning in liver transplantation remains controversial.

METHODS

KIR and HLA genotypes were studied in 402 liver transplants, using sequence-specific oligonucleotides and primer methods. Recipients and donor KIRs, HLA-C genotypes, KIR gene mismatches (MMs) between recipient-donor pairs, and KIR/HLA-ligand combinations were analyzed in overall transplantations, in the acute rejection (AR; n=110) and non-AR (n=292) groups.

RESULTS

KIR gene MMs between recipients and donors, mainly in activating KIRs, and KIR2DL3 and KIR2DS1 of recipients in the presence of donor C2 ligands, significantly enhanced early AR rate (P<0.05), with KIR2DL3 and KIR2DS1 exhibiting a synergic effect in dependence of the donor C2 ligand number (χ2=7.662, P=0.022). KIR2DL3, KIR2DS1, and also KIR2DS4 significantly influenced short-term graft survival, with a benefit for transplantations combining KIR2DL3 recipients and donors having C1 ligands (log rank, P<0.019 at 1 year; hazards ratio [HR], 0.321; 95% confidence interval [CI], 0.107-0.962; P=0.042), whereas KIR2DS1 and KIR2DS4 recipients combined with donors lacking C1 ligands (C2/C2) exhibited a worse graft survival (log rank, P=0.035 at 6 months; HR, 7.713; 95% CI, 2.156-27.369; P=0.002 for KIR2DS1; and log rank, P=0.006 at 1 year; HR, 3.794; 95% CI, 1.267-11.365; P=0.017 for KIR2DS4).

CONCLUSIONS

This study shows that KIR gene-gene MMs increase AR and that KIRs/C ligands associated to AR and KIR2DS4/C ligands also influence short-term graft survival.

Natural killer cells in hepatitis C virus infection

Hepatitis C virus (HCV) infection induces the long-term risk of liver cirrhosis or hepatocellular carcinoma and in adults represents the most common cause of liver transplantation. Natural killer (NK) cells participate in innate immune responses with efficient direct antitumor and antiviral defense. Over the years, their complex interaction with downstream adaptive responses and with the regulation of immune responses has been increasingly recognized. Considerable advances have been made particularly in understanding the role of NK cells in the pathophysiology of HCV infection and their possible use as biological markers for clinical purposes. This review summarizes the available data on the role of NK cells in the natural history of HCV infection and their role in the outcome of treatment. The main objective of this review is to summarize recent advancements in the basic understanding of NK cell function highlighting their possible translational use in clinical practice. An integrated practical view on the possible use of currently available predictive immunogenetic and NK cell functional tests is provided, to support clinical management choices for optimal treatment of patients with both standard and new drug regimens.

Natural killer KIR3DS1 is closely associated with HCV viral clearance and sustained virological response in HIV/HCV patients

Aim

To evaluate the influence of the presence of the killer cell immunoglobulin-like receptor (KIR) 3DS1 on HCV treatment response in HIV/HCV genotype 1 co-infected patients

Methods

HIV/HCV co-infected patients were included. KIR3DS1, their specific HLA-B ligands and IL28B gene were genotyped. Reductions of plasma HCV RNA levels between baseline and week 1, week 2 and week 4 were analyzed for IL28B genotype and KIR3DS1 (HLA Bw4 or Bw6). Rapid and sustained virological response (RVR and SVR) rates were also analyzed.

Results

Sixty HIV/HCV genotype 1 co-infected patients were included. Patients with KIR3DS1 and Bw4 had higher rates of HCV viral decline than those who were not carriers of KIR3DS1 (week1: p = 0.01; week2: p = 0.038; week 4: p = 0.03). Patients carrying KIR3DS1/Bw4 had higher rates of RVR and SVR than those who did not carry KIR3DS1 (RVR: 46.15% versus 17.02%, p = 0.012; SVR: 63.6% versus 13 26.5%, p = 0.031). With respect to patients carrying the IL28B-CC genotype, those with KIR3DS1/Bw4 had greater rates of HCV viral clearance (week1: p<0.001; week2: p = 0.01; week 4: p = 0.02), RVR (p = 0.015) and SVR (p = 0.029) than those not carrying KIR3DS1.

Conclusion

Our results show that the KIR3DS1 genotype has a positive effect on HCV viral clearance during the first weeks of Peg-IFN/RBV treatment in HCV/HCV co-infected patients bearing genotype 1, and higher RVR and SVR rates.

The role of natural killer cells in hepatitis C infection

HCV infection is an exponentially growing health burden worldwide, with an estimated 170 million people infected. Although therapies for HCV are continually improving, there remain a considerable proportion of patients who do not achieve viral eradication and develop liver disease. Natural killer (NK) cells are crucial for T-cell activation and are one of the first-line sentinel cell responders to viral infection. A recent explosion in studies exploring the role of NK cells in HCV infection has yielded important mechanistic information and intriguing potential therapeutic options for HCV infection. This review provides a general overview of normal NK cell function and outlines some of the important mechanisms characterizing the immune interplay between NK cells and HCV infection.

Association of killer cell immunoglobulin-like receptor polymorphisms with chronic hepatitis C and responses to therapy in Brazil

Soroprevalence for Hepatitis C virus is reported as 2.12% in Northern Brazil, with about 50% of the patients exhibiting a sustained virological response (SVR). Aiming to associate polymorphisms in Killer Cell Immunoglobulin-like Receptors (KIR) with chronic hepatitis C and therapy responses we investigated 125 chronic patients and 345 controls. Additionally, 48 ancestry markers were genotyped to control for population stratification. The frequency of the KIR2DL2 and KIR2DL2+HLA-C^Asp80 gene and ligand was higher in chronic infected patients than in controls (p < 0.0009, OR = 3.4; p = 0.001, OR = 3.45). In fact, KIR2DL3 is a weaker inhibitor of NK activity than KIR2DL2, which could explain the association of KIR2DL2 with chronic infection. Moreover, KIR2DS2 and KIR2DS2+HLA-C^Asp80 (p < 0.0001, OR = 2.51; p = 0.0084, OR = 2.62) and KIR2DS3 (p < 0.0001; OR = 2.57) were associated with chronic infection, independently from KIR2DL2. No differences in ancestry composition were observed between control and patients, even with respect to therapy response groups. The allelic profile KIR2DL2/KIR2DS2/KIR2DS3 was associated with the chronic hepatitis C (p < 0.0001; OR = 3). Furthermore, the patients also showed a higher mean number of activating genes and a lower frequency of the homozygous AA profile, which is likely secondary to the association with non-AA and/or activating genes. In addition, the KIR2DS5 allele was associated with SVR (p = 0.0261; OR = 0.184).The ancestry analysis of samples ruled out any effects of population substructuring and did not evidence interethnic differences in therapy response, as suggested in previous studies.

Control of human viral infections by natural killer cells

Natural killer (NK) cells are effector cells of the innate immune system and are important in the control of viral infections. Their relevance is reflected by the multiple mechanisms evolved by viruses to evade NK cell-mediated immune responses. Over recent years, our understanding of the interplay between NK cell immunity and viral pathogenesis has improved significantly. Here, we review the role of NK cells in the control of four important viral infections in humans: cytomegalovirus, influenza virus, HIV-1, and hepatitis C virus.

Natural killer cell responses during viral infections: flexibility and conditioning of innate immunity by experience

Natural killer (NK) cells mediate innate defense against viral infections, but the mechanisms in place to access their functions as needed during diverse challenges while limiting collateral damage are poorly understood. Recent molecular characterization of effects mediated through infection-induced inhibitory/activating NK receptor-ligand pairs and cytokines are providing new insights into pathways regulating their responses and revealing unexpected consequences for NK cell subset effects, maintenance, proliferation and function through times overlapping with adaptive and long-lived immunity. The observations define flexible pathways for experience-induced 'conditioning' and challenge narrowly defined roles for NK cells and innate immunity as first responders with prescribed functions. They suggest that individual experiences as well as genes influence the innate immune resources available to fight off an infection.

Genomics and HCV infection: progression of fibrosis and treatment response

HCV infection is a global health problem that affects 170 million people worldwide. The severity of the disease varies from asymptomatic chronic infection to cirrhosis and hepatocellular carcinoma (HCC). Recently, the standard of care for genotype 1 patients has greatly improved with the addition of protease inhibitors (telaprevir or boceprevir) to pegylated interferon (PegIFN) and ribavirin (RBV). The prediction of fibrosis progression and the response to antiviral treatment are two major issues in the management of patients with chronic hepatitis C. Differential expression of mRNAs was first analyzed for both progression of fibrosis and treatment response. Specific polymorphisms, associated with either fibrosis or viral response, were identified thanks to major improvements in genome scanning technologies. Since 2009, several independent genome wide association studies (GWAS) have reported an association between genetic polymorphisms within the IL-28B promoter and both natural and treatment-induced clearance in genotype 1 infected patients. These different studies showed the strong association and the importance of IL-28B polymorphisms in the treatment response. Combining the different genetic factors could improve their predictive value and help identify patients at a high risk of progression of fibrosis as well as those with a lower chance of responding to treatment. The aim of this review was to discuss the genomic factors (mRNAs, miRNAs, and SNPs) and HCV infection with clinical implications for either progression of fibrosis or treatment response. Recent findings on the IL-28B polymorphism and its application in clinical practice will also be discussed.

Hepatitis C virus-mediated modulation of cellular immunity

The hepatitis C virus (HCV) is a major cause of chronic liver disease globally. A chronic infection can result in liver fibrosis, liver cirrhosis, hepatocellular carcinoma and liver failure in a significant ratio of the patients. About 170 million people are currently infected with HCV. Since 80 % of the infected patients develop a chronic infection, HCV has evolved sophisticated escape strategies to evade both the innate and the adaptive immune system. Thus, chronic hepatitis C is characterized by perturbations in the number, subset composition and/or functionality of natural killer cells, natural killer T cells, dendritic cells, macrophages and T cells. The balance between HCV-induced immune evasion and the antiviral immune response results in chronic liver inflammation and consequent immune-mediated liver injury. This review summarizes our current understanding of the HCV-mediated interference with cellular immunity and of the factors resulting in HCV persistence. A profound knowledge about the intrinsic properties of HCV and its effects on intrahepatic immunity is essential to be able to design effective immunotherapies against HCV such as therapeutic HCV vaccines.