Ana Romero

Interferon (IFN)–γ–Inducible Protein–10: Association with Histological Results, Viral Kinetics, and Outcome during Treatment with Pegylated IFN-α2a and Ribavirin for Chronic Hepatitis C Virus Infection

BACKGROUND We investigated associations between interferon (IFN)-gamma-inducible protein (IP)-10 and liver histological results, viral kinetic response, and treatment outcome in patients infected with hepatitis C virus (HCV) genotypes 1-4. METHODS Plasma IP-10 was monitored before, during, and after treatment with pegylated IFN- alpha 2a and ribavirin in 265 HCV-infected patients. RESULTS In univariate analyses, a low baseline IP-10 level was significantly associated with low baseline viral load, rapid viral response (RVR), a sustained viral response (SVR), body mass index <25 kg/m2, and less-pronounced fibrosis, inflammation, and steatosis (for HCV genotypes other than 3). When the results of the univariate analyses were included in multivariate analyses, a low plasma IP-10 level, low baseline viral load, and genotype 2 or 3 infection were independent predictors of an RVR and SVR. IP-10 levels decreased 6 weeks into treatment and remained low in patients with an SVR. By contrast, plasma levels of IP-10 rebounded in patients who had detectable HCV RNA after the completion of treatment. Using cutoff IP-10 levels of 150 and 600 pg/mL for predicting an SVR in patients infected with HCV genotype 1 yielded a specificity and sensitivity of 81% and 95%, respectively. CONCLUSION Baseline IP-10 levels are predictive of the response to HCV treatment.

IP-10 predicts viral response and therapeutic outcome in difficult-to-treat patients with HCV genotype 1 infection

Plasma from 173 patients with HCV genotype 1 infection was analyzed for IP‐10 levels prior to treatment with pegylated interferon‐α‐2a and ribavirin. Significantly lower IP‐10 levels were observed in patients achieving a rapid viral response (RVR) (P < .0001), even in those with body mass index (BMI) ≥ 25 kg/m2 (P = .004) and with baseline viral load ≥ 2 million IU/mL (P = .001). Similarly, significantly lower IP‐10 levels were observed in patients obtaining a sustained viral response (SVR) (P = .0002), including those having higher BMI (P < .05), higher viral load (P = .0005), and both higher BMI and viral load (P < .03). In multivariate logistic regression analyses, a low IP‐10 value was independently predictive of both RVR and SVR. A baseline cutoff IP‐10 value of 600 pg/mL yielded a negative predictive value (NPV) of 79% (19/24) for all genotype 1–infected patients, which was comparable with that observed using a reduction in HCV‐RNA by at least 2 logs after 12 weeks of therapy (NPV 86%; 19/22); by combining the two, 30 of 38 patients (NPV 79%) potentially could have been spared unnecessary therapy. In patients having both higher BMI and viral load, cut‐off levels of 150 and 600 pg/mL yielded a positive predictive value (PPV) of 71% and NPV of 100%, respectively. In conclusion, pretreatment IP‐10 levels predict RVR and SVR in patients infected with HCV genotype 1, even in those with higher BMI and viral load. A substantial proportion of the latter patients may achieve SVR in spite of unfavorable baseline characteristics if their pretreatment IP‐10 level is low. Thus, pretreatment IP‐10 analysis may prove helpful in decision‐making regarding pharmaceutical intervention. (HEPATOLOGY 2006;44:1617–1625.)

Response prediction in chronic hepatitis c by assessment of IP-10 and IL28B-related single nucleotide polymorphisms

Background High baseline levels of IP-10 predict a slower first phase decline in HCV RNA and a poor outcome following interferon/ribavirin therapy in patients with chronic hepatitis C. Several recent studies report that single nucleotide polymorphisms (SNPs) adjacent to IL28B predict spontaneous resolution of HCV infection and outcome of treatment among HCV genotype 1 infected patients. Methods and Findings In the present study, we correlated the occurrence of variants at three such SNPs (rs12979860, rs12980275, and rs8099917) with pretreatment plasma IP-10 and HCV RNA throughout therapy within a phase III treatment trial (HCV-DITTO) involving 253 Caucasian patients. The favorable SNP variants (CC, AA, and TT, respectively) were associated with lower baseline IP-10 (P = 0.02, P = 0.01, P = 0.04) and were less common among HCV genotype 1 infected patients than genotype 2/3 (P<0.0001, P<0.0001, and P = 0.01). Patients carrying favorable SNP genotypes had higher baseline viral load than those carrying unfavorable variants (P = 0.0013, P = 0.029, P = 0.0004 respectively). Among HCV genotype 1 infected carriers of the favorable C, A, or T alleles, IP-10 below 150 pg/mL significantly predicted a more pronounced reduction of HCV RNA from day 0 to 4 (first phase decline), which translated into increased rates of RVR (62%, 53%, and 39%) and SVR (85%, 76%, and 75% respectively) among homozygous carriers with baseline IP-10 below 150 pg/mL. In multivariate analyses of genotype 1-infected patients, baseline IP-10 and C genotype at rs12979860 independently predicted the first phase viral decline and RVR, which in turn independently predicted SVR. Conclusions Concomitant assessment of pretreatment IP-10 and IL28B-related SNPs augments the prediction of the first phase decline in HCV RNA, RVR, and final therapeutic outcome.

A proinflammatory peptide from Helicobacter pylori activates monocytes to induce lymphocyte dysfunction and apoptosis

Infection with Helicobacter pylori causes chronic gastritis, which is characterized by a dense mucosal infiltration by inflammatory cells such as monocytes/macrophages. H. pylori-induced inflammation is a risk factor for the development of gastric adenocarcinoma, but the mechanisms involved in H. pylori-associated carcinogenesis are poorly understood. A cecropin-like H. pylori peptide, Hp(2-20), was found to be a monocyte chemoattractant and activated the monocyte NADPH-oxidase to produce oxygen radicals. The receptors mediating monocyte activation were identified as FPRL1 and the monocyte-specific orphan receptor FPRL2. Hp(2-20)-activated monocytes inhibited lymphocytes with antitumor properties, such as CD56+ natural killer (NK) cells and CD3epsilon+ T cells. The changes observed in NK cells and T cells--a reduced antitumor cytotoxicity, downregulation of CD3zeta expression, and apoptosis--were mediated by Hp(2-20)-induced oxygen radicals. Histamine, a gastric mucosal constituent, rescued NK cells and T cells from inhibition and apoptosis by suppressing Hp(2-20)-induced oxygen radical formation. We conclude that H. pylori expression of this monocyte-activating peptide contributes to its ability to attract and activate monocytes and reduces the function and viability of antineoplastic lymphocytes. These novel mechanisms may be subject to local, histaminergic regulation in the gastric mucosa.

A hepatitis C virus-encoded, nonstructural protein (NS3) triggers dysfunction and apoptosis in lymphocytes: role of NADPH oxidase-derived oxygen radicals

The persistent infection caused by hepatitis C virus (HCV) is presumably explained by a deficient immune response to the infection, but the basis for the inefficiency of immune‐mediated virus eradication is not known in detail. This study addresses mechanisms of relevance to dysfunction of cytotoxic lymphocytes in HCV infection, with a focus on the role of phagocyte‐derived oxygen radicals. We show that NS3, a nonstructural, HCV‐encoded protein, induces a prolonged release of oxygen radicals from mononuclear and polymorphnuclear phagocytes by activating a key enzyme in radical formation, the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The NS3‐activated phagocytes, in turn, induced dysfunction and/or apoptosis in three major subsets of lymphocytes of relevance to defense against HCV infection: CD3+/56– T cells, CD3–/56+ natural killer (NK) cells, and CD3+/56+ NKT cells. Two inhibitors of the NADPH oxidase, histamine and diphenylene iodonium, suppressed the NS3‐induced oxygen radical production and efficiently protected lymphocytes against NS3‐induced apoptosis and dysfunction. In conclusion, we propose that NS3, by triggering oxygen radical formation in phagocytes, may contribute to the dysfunction of antiviral lymphocytes in HCV‐infected liver tissue and that strategies to circumvent oxidative stress may be useful in preventing HCV‐associated carcinogenesis and facilitating lymphocyte‐mediated clearance of infected cells.

NKp46 and NKG2D receptor expression in NK cells with CD56dim and CD56bright phenotype: regulation by histamine and reactive oxygen species

The cytotoxicity of natural killer (NK) cells is dependent on the interaction between target cell ligands and a series of stimulatory receptors on NK cells. Two of these triggering receptors, the NKp46 natural cytotoxicity receptor (NKp46) and the major histocompatibility complex (MHC) class I‐interactive NKG2D receptor, are deficiently expressed by NK cells recovered from patients with acute myeloid leukaemia (AML), but little is known regarding the regulation of NKp46 and NKG2D expression. Here we report that mononuclear and polymorphonuclear phagocytes downregulate the cell surface density of NKp46 and NKG2D on NK cells with CD56dim phenotype in vitro by a mechanism that is dependent on the availability of phagocyte‐derived reactive oxygen species (ROS). Histamine maintained NKp46 and NKG2D expression despite the presence of inhibitory phagocytes by targeting an H2 receptor on phagocytes. By contrast, NKp46 and NKG2D expression by the CD56bright subset of NK cells was resistant to inhibition by phagocytes. Our findings are suggestive of a novel mechanism of relevance to the regulation of NKp46/NKG2D receptor expression. Moreover, our findings suggest that the previously reported action of histamine on NK cell‐mediated killing of leukaemic cells may be related to the preservation of activatory NK‐cell receptors.

Oxygen Radicals Induce Poly(ADP-Ribose) Polymerase-Dependent Cell Death in Cytotoxic Lymphocytes

Cytotoxic T cells and NK cells will acquire features of apoptosis when exposed to oxygen radicals, but the molecular mechanisms underlying this phenomenon are incompletely understood. We have investigated the role of two enzyme systems responsible for execution of cell death, caspases and the poly(ADP-ribose) polymerase (PARP). We report that although human cytotoxic lymphocytes were only marginally protected by caspase inhibitors, PARP inhibitors completely protected lymphocytes from radical-induced apoptosis and restored their cytotoxic function. The radical-induced, PARP-dependent cell death was accompanied by nuclear accumulation of apoptosis-inducing factor and a characteristic pattern of large-fragment DNA degradation. It is concluded that the PARP/apoptosis-inducing factor axis is critically involved in oxygen radical-induced apoptosis in cytotoxic lymphocytes.

The CD16−/CD56bright Subset of NK Cells Is Resistant to Oxidant-Induced Cell Death

Phagocyte-derived reactive oxygen species (“oxygen radicals”) have been ascribed a suppressive role in immunoregulation by inducing dysfunction and apoptotic cell death in lymphocytes. Earlier studies show that human NK cells are exceptionally sensitive to oxygen radical-induced apoptosis and functional inhibition. Two subsets of human CD56+ NK cells have been identified: the highly cytotoxic CD56dim cells which constitute >90% of NK cells in peripheral blood, and the less cytotoxic but efficiently cytokine-producing CD56bright cells. In this study, we demonstrate that the CD56bright subset of NK cells, in contrast to CD56dim cells, remains viable and functionally intact after exposure to phagocyte-derived or exogenously added oxygen radicals. The resistance of CD56bright cells to oxidative stress was accompanied by a high capacity of neutralizing exogenous hydrogen peroxide, and by a high cell-surface expression of antioxidative thiols. Our results imply that CD56bright NK cells are endowed with an efficient antioxidative defense system that protects them from oxygen radical-induced inactivation.

Cutting Edge: Antioxidative Properties of Myeloid Dendritic Cells: Protection of T Cells and NK Cells from Oxygen Radical-Induced Inactivation and Apoptosis

Dendritic cells (DCs) communicate with nonadaptive and adaptive lymphocytes on multiple levels. Efficient DC-lymphocyte interactions require that lymphocytes remain viable and functional also under conditions of oxidative stress, such as in microbial infection or in the malignant microenvironment. For this study, we exposed human T and NK cells to oxidants delivered either by autologous phagocytes or in the form of exogenous hydrogen peroxide. In accordance with earlier studies, these lymphocytes became dysfunctional and subsequently apoptotic. The presence of myeloid DCs efficiently rescued T cells (CD4+ and CD8+) and NK cells from oxidant-induced inactivation and apoptosis. The mechanism of the myeloid DC-mediated lymphocyte protection was, at least in part, explained by the capacity of the myeloid DCs to neutralize extracellular oxygen radicals, which, in turn, was reversible upon coincubation with a catalase inhibitor. Our results are suggestive of a novel aspect of DC-lymphocyte interaction that may have implications for lymphocyte function in inflamed tissue.

Post‐consolidation Immunotherapy with Histamine Dihydrochloride and Interleukin‐2 in AML

The initial chemotherapy in acute myeloid leukaemia (AML) comprises a first phase of induction and a second phase of consolidation. In the majority of patients, the induction treatment leads to complete remission (CR), defined as microscopic disappearance of leukaemic disease along with the return of normal haematopoiesis. However, despite the introduction of more efficacious consolidation regimens, a worryingly large proportion of AML patients in CR will subsequently experience relapses with poor prospects of long‐term survival. A relapse is assumed to be the result of expansion of residual leukaemic cells that have escaped the initial chemotherapy. The anti‐leukaemic functions of T cells and natural killer (NK) cells has formed the background to the use of interleukin‐2 (IL‐2), a T‐ and NK cell‐activating cytokine, with the aim to eliminate residual leukaemia and hence reduce the relapse rate in AML, but the clinical trials using IL‐2 monotherapy have yielded disappointment. A recent phase III study has demonstrated that post‐consolidation treatment with the combination of histamine dihydrochloride (HDC) and IL‐2 significantly prevents relapse in AML patients. Here we account for the preclinical background to the use of HDC/IL‐2 in AML along with a review of clinical results.