Congenital hip dysplasia: The importance of early screening and treatment.

Congenital Hip Dysplasia (CHD) is characterized by a hip joint dislocation between the femoral head and the acetabulum, with a multifactorial etiology. This disorder can be an isolated condition or the manifestation of a syndromic condition, and it has been estimated with higher rates than registered, with a predominance in female sex and left side; risk factors are now defined. In Italy, the incidence rate is 3-4%, with significant regional differences: higher in Lombardy and lower in Sicily. Because clinical examination alone is insufficient to diagnose CHD, it is supplemented with ultrasonography and X-ray if necessary. Surveillance, static or dynamic splints, or osteotomies are the only treatment options. The goal of this study was to evaluate our experience in terms of management and conservative treatment of all newborns from January 2018 to May 2022: female sex and left hip were major involved, risk factors were not significant in our case, but results from early diagnosis and treatments, in terms of better outcome, were interesting. After a strict 6-month follow-up period, 89.13% of the patients were classified as grade Ia or Ib according to the Graf classification system. Finally, we emphasize the importance of early universal screening and subsequent diagnosis to allow for early treatment of the disorder, at an age when conservative treatments can yield good results.

A comparative analysis of unintegrated HIV-1 DNA measurement as a potential biomarker of the cellular reservoir in the blood of patients controlling and non-controlling viral replication.

BACKGROUND: The persistence of HIV-1 in reservoir cells is one of the major obstacles to eradicating the virus in infected individuals receiving combination antiretroviral therapy (ART). HIV-1 persists in infected cells as a stable integrated genome and more labile unintegrated DNA (uDNA), which includes linear, 1-LTR and 2-LTR circular DNA. 2-LTR circle DNA, although less abundant, is considered a surrogate marker of recent infection events and is currently used instead of the other unintegrated species as a diagnostic tool. This pilot study aimed to investigate how to best achieve the measurement of uDNA. METHODS: A comparative analysis of two qPCR-based methods (U-assay and 2-LTR assay) was performed on the blood of 12 ART-naïve, 14 viremic and 29 aviremic On-ART patients and 20 untreated spontaneous controllers (HIC), sampled at a single time point. RESULTS: The U-assay, which quantified all unintegrated DNA species, showed greater sensitivity than the 2-LTR assay (up to 75%, p < 0.0001), especially in viremic subjects, in whom other forms, in addition to 2-LTR circles, may also accumulate due to active viral replication. Indeed, in aviremic On-ART samples, the U-assay unexpectedly measured uDNA in a higher proportion of samples (76%, 22/29) than the 2-LTR assay (41%, 12/29), (p = 0.0164). A trend towards lower uDNA levels was observed in aviremic vs viremic On-ART patients, reaching significance when we combined aviremic On-ART and HIC (controllers) vs Off-ART and viremic On-ART subjects (non-controllers) (p = 0.0003), whereas 2-LTR circle levels remained constant (p ≥ 0.2174). These data were supported by the high correlation found between uDNA and total DNA (r = 0.69, p < 0.001). CONCLUSIONS: The great advantage of the U-assay is that, unlike the 2-LTR assay, it allows the accurate evaluation of the totality of uDNA that can still be measured even during successful ART when plasma viremia is below the cut-off of common clinical tests (< 50 copies/mL) and 2-LTR circles are more likely to be under the quantification limit. UDNA measurement in blood cells may be used as a biomarker to reveal a so far hidden or underestimated viral reservoir. The potential clinical relevance of uDNA quantification may lead to improvements in diagnostic methods to support clinical strategies.

Control of the HIV-1 DNA Reservoir Is Associated In Vivo and In Vitro with NKp46/NKp30 (CD335 CD337) Inducibility and Interferon Gamma Production by Transcriptionally Unique NK Cells.

The size of lentiviral DNA reservoirs reflects the effectiveness of immune responses against lentiviruses. So far, abundant information has been gathered on the control of HIV-1 replication. Understanding the innate mechanisms contributing to containment of the HIV DNA reservoir, however, are only partly clarified and are relevant to guiding interventions for reservoir containment or eradication. We studied the contribution of natural killer (NK) cell functional features in HIV patients controlling replication either spontaneously (HIV controllers [HIC]) or after progression and antiretroviral treatment (progressor patients [PP]). An inverse correlation between HIV DNA copy numbers (either total or integrated) in circulating CD4+ cells and NK cell function was observed. Induced interferon gamma (IFN-γ) production and NKp46/NKp30 activating receptor-induced expression correlated inversely with reservoir size. The correlation was present not only for a homogeneous cohort of HIC patients but also when PP were included in the analysis. Adaptive (NKG2C+ CD57+) NK cell features were not associated with reservoir size. However, a distinct set of 370 differentially expressed transcripts was found to underlie functional differences in NK cells controlling HIV DNA reservoir size. In proof-of-principle in vitro experiments of CD4+ cell infection with HIV-1, purified NK cells with the above-mentioned functional/transcriptional features displayed 10- and 30-fold higher abilities to control HIV replication and DNA burdens in vitro, respectively, than those of other NK cells. Thus, NK cells with a specific functional and transcriptional signature contribute to control of the HIV reservoir in CD4+ cells. Their selection, expansion, and/or adoptive transfer may support strategies to eradicate HIV-1 infection or to safely deescalate antiretroviral treatment.IMPORTANCE The most relevant feature of HIV-1 infection is represented by its DNA reservoir size in the body, which guarantees lifelong infection and resumption of virus replication after antiretroviral treatment interruption. So far, there has been little success in the identification of factors contributing to HIV-1 reservoir containment. In this study, by studying quantitative total and integrated HIV-1 DNA levels and NK cells in HIV-1 patients with either progressive or nonprogressive disease, we observed that inducible IFN-γ and natural cytotoxicity receptor (NCR) expression in a specific subset of NK cells with a characteristic transcriptional signature represents a correlate for HIV-1 reservoir control. This represents an advance in our understanding of the mechanism(s) that controls the lentivirus reservoir. Monitoring, selection, expansion, and adoptive transfer of these NK cells may allow monitoring of treatment efficacy and the likelihood of reservoir control and may support protocols for HIV-1 eradication.

Natural Killer Cell Development and Maturation Revisited: Possible Implications of a Novel Distinct Lin-CD34+DNAM-1brightCXCR4+ Cell Progenitor.

Since the first description of natural killer (NK) cells, the view on their role in innate immunity has evolved considerably. In addition to first-line defense against transformed and pathogen-infected autologous cells, NK cells contribute to modulate adaptive immune responses and in some cases acquire specialized functions, including exhausted, adaptive, and decidual NK cells. NK cells derive from CD34+ progenitors, in vivo and in vitro; however, it is unclear whether the high phenotype diversity in vivo may be generated from these precursors alone. The recent characterization of a novel CD34+DNAM-1brightCXCR4+ precursor giving rise to apparently licensed and functional maturing NK cells may suggest the possibility for a higher than expected common lymphocyte precursor diversity and a consequently higher peripheral NK cell phenotype variability. Here, we review the evidences on NK cell central and peripheral development from CD34+ precursors and propose a possible updated reading frame based on the characterization of CD34+DNAM-1brightCXCR4+ cell progenies, which favors the possibility of concurrent NK cell maturation from different CD34+ precursors.

Analysis of NK Cell Function and Receptor Expression During HTLV-1 and HTLV-2 Infection.

Cytofluorimetric analysis is a typical method in immunology to evaluate phenotype and function of Natural Killer (NK) cells derived from HTLV-1/2 infected patients and healthy donors. Here, we described protocols to NK cells phenotypical and cytotoxicity assay, performed by flow cytometry on fresh and immune-magnetically or flow cytometry sorted NK cells. A new developed protocol able to evaluate IFNγ production has been included.

Activating Killer Immunoglobulin Receptors and HLA-C: a successful combination providing HIV-1 control.

Several studies demonstrated a relevant role of polymorphisms located within the HLA-B and -C loci and the Killer Immunoglobulin Receptors (KIRs) 3DL1 and 3DS1 in controlling HIV-1 replication. KIRs are regulatory receptors expressed at the surface of NK and CD8+ T-cells that specifically bind HLA-A and -B alleles belonging to the Bw4 supratype and all the -C alleles expressing the C1 or C2 supratype. We here disclose a novel signature associated with the Elite Controller but not with the long-term nonprogressor status concerning 2DS activating KIRs and HLA-C2 alleles insensitive to miRNA148a regulation. Overall, our findings support a crucial role of NK cells in the control of HIV-1 viremia.

The role of drugs in bone pain.

Painful symptomatology in the skeletal system can be found in various pathological conditions and can be either localised or diffused. Bone tenderness is common in those who are of an elderly age. TREATMENT STRATEGY: Patients should be informed of the possible causes of their pain and the different therapies that could alleviate it; furthermore they should be encouraged to have an active role in their therapy. It is necessary to prevent the onset of the pain (by the clock) by considering the biological half-life, the bioavailability and the duration of action of the therapy. According to the World Health Organization (WHO), pain treatment is based on a three-step ladder. ADJUVANT THERAPIES: Adjuvant therapies are often associated with the drugs in the WHO three step ladder. This heterogeneous group of non-analgesic drugs is used in the treatment of bone pain by bettering the analgesia or reducing the side effects brought on by analgesics. CONCLUSION: In the daily struggle that doctors face to treat their patients, pain management should not be disregarded. Among the various types of pain, bone pain, must not be underestimated but be fought against by using all means available. Patients need to be treated depending on the severity of their pain, NSAIDs should be the preferred choice of treatment for acute pain but not for that of chronic pain. In the case of chronic pain opioids should be used in their most recent fomulations as they can guarantee fewer side effects. Patients should also be prescribed adjuvant drugs as well as being given psychological support in order to ensure successful treatment.

'Emergency exit' of bone-marrow-resident CD34(+)DNAM-1(bright)CXCR4(+)-committed lymphoid precursors during chronic infection and inflammation.

During chronic inflammatory disorders, a persistent natural killer (NK) cell derangement is observed. While increased cell turnover is expected, little is known about whether and how NK-cell homeostatic balance is maintained. Here, flow cytometric analysis of peripheral blood mononuclear cells in chronic inflammatory disorders, both infectious and non-infectious, reveals the presence of a CD34(+)CD226(DNAM-1)(bright)CXCR4(+) cell population displaying transcriptional signatures typical of common lymphocyte precursors and giving rise to NK-cell progenies with high expression of activating receptors and mature function and even to α/ß T lymphocytes. CD34(+)CD226(bright)CXCR4(+) cells reside in bone marrow, hardly circulate in healthy donors and are absent in cord blood. Their proportion correlates with the degree of inflammation, reflecting lymphoid cell turnover/reconstitution during chronic inflammation. These findings provide insight on intermediate stages of NK-cell development, a view of emergency recruitment of cell precursors, and upgrade our understanding and monitoring of chronic inflammatory conditions.

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.

Relationship between innate immunity, soluble markers and metabolic-clinical parameters in HIV+ patients ART treated with HIV-RNA<50 cp/mL.

INTRODUCTION: The persistence of immune activation and inflammation in HIV patients with HIV-RNA (VL) undetectable causes many co-morbidities [1-3]. The aim of this study is to correlate monocytes (m) and NK cell activation levels, soluble markers and oxidative stress with clinical, biochemical and metabolic data in HIV-1 infected patients with VL≤50 copies (cp)/mL on antiretroviral therapy. MATERIALS AND METHODS: Multicentre, cross-sectional study in patients with VL≤50 cp/mL and on antiretroviral therapy by at least six months. We studied: activation/homing markers (CD38, HLA-DR, CCR-2, PDL-1) on inflammatory, intermediate, proinflammatory m; activatory receptors NKp30, NKp46 and HLA-DR on NK cells; soluble inflammatory (sCD14, adiponectina, MCP-1) and stress oxidative markers (dRoms, antiRoms). Univariate analyses are performed with non-parametric and Pearson tests. The significant correlations were adjusted for possible known confounding factors (smoking, Cytomegalovirus IgG serology, Raltegravir, Protease Inhibitor [PI] therapy and HCV-RNA) with multivariate analysis. RESULTS: In the 68 patients the positive correlation between age and antiRoms was significant also after adjustment for PI use (p=0.05). The% CD8+T was associated with% proinflammatory m (p=0.043) and with their expression of CCR2 mean fluorescence intensity (MFI) (p=0.012). The% NKp46+ was positively correlated with CD4+T count (p=0.001). The fibrinogen was positively associated with dRoms (p=0.052) and the positive correlation between triglycerides and antiRoms has been confirmed (p<0.001); the impact of antiRoms on HDL/triglycerides ratio (p=0.006) was observed after adjustment for PI use. The BMI was associated with smoking (p=0.011). Only the maraviroc-treated patients showed minimal arterial pressure, fibrinogen and antiRoms lower (p=0.001, 0.004 e 0.006) and sCD14 values higher (p=0.029). CONCLUSIONS: Patients with long history of HIV infection and stable immunological and virological status showed interactions between acquired and innate immunity activation; moreover, the levels of some metabolic and inflammatory parameters correlate with oxidative stress values and innate immunity activation. The age, BMI and smoking impact metabolic and immunological parameters. The correlations between antiretroviral drugs and clinical-immunological parameters need further confirmations.

Baseline and Dynamic Expression of Activating NK Cell Receptors in the Control of Chronic Viral Infections: The Paradigm of HIV-1 and HCV.

Natural killer (NK) cell function is regulated by a balance between the triggering of activating and inhibitory receptors expressed on their surface. A relevant effort has been focused so far on the study of KIR carriage/expression setting the basis for NK cell education and self-tolerance. Focus on the evolution and regulation of activating NK receptors has lagged behind so far. Our understanding of activating receptor expression and regulation has recently improved by evidences derived from in vitro and in vivo studies. Virus infection - either acute or chronic - determines preferential expansion of NK cells with specific phenotype, activating receptors, and with recall-like functional activity. Studies on patients with viral infection (HIV and HCV) and specific diverging clinical courses confirm that inter-individual differences may exist in baseline expression of natural cytotoxicity receptors (NKp46 and NKp30). The findings that patients with divergent clinical courses have different kinetics of activating receptor density expression upon NK cell activation in vitro provide an additional, time-dependent, functional parameter. Kinetic changes in receptor expression thus represent an additional parameter to basal receptor density expression. Different expression and inducibilities of activating receptors on NK cells contribute to the high diversity of NK cell populations and may help our understanding of the inter-individual differences in innate responses that underlie divergent disease courses.

Immunology of tuberculosis.

MTB ranks as the first worldwide pathogen latently infecting one third of the population and the second leading cause of death from a single infectious agent, after the human immunodeficiency virus (HIV). The development of vigorous and apparently appropriate immune response upon infection with M. tuberculosis in humans and experimental animals conflict with failure to eradicate the pathogen itself and with its ability to undergo clinical latency from which it may exit. From a clinical standpoint, our views on MTB infection may take advantage from updating the overall perspective, that has quite changed over the last decade, following remarkable advances in our understanding of the manipulation of the immune system by M. tuberculosis and of the role of innate components of the immune response, including macrophages, neutrophils, dendritic cells and NK cells in the initial spread of MTB and its exit from latency. Scope of this review is to highlight the major mechanisms of MTB escape from immune control and to provide a supplementary translational perspective for the interpretation of innate immune mechanisms with particular impact on clinical aspects.

Sports-related changes of the synovial membrane.

PURPOSE: the aim of this study is to differentiate the behavior of the synovial membrane in the presence of various stimuli in patients who practice sports. METHODS: fifty one patients (30 males and 21 females, mean age 48 years, range 31-59 years) who actively practiced non-competitive sports underwent a biopsy of the synovial membrane during arthroscopic surgery performed for joint effusion secondary to meniscal lesion (24 cases), anterior cruciate ligament injury (ACL) (17 cases), postoperative knee joint stiffness (2 cases), aseptic loosening or dislocation of the polyethylene component of uni-compartmental knee arthroplasty (5 cases), and anterior fibrous impingement of the ankle (3 cases). Synovial tissue samples were obtained during surgery from all the patients and processed for light microscopy, transmission electron microscopy and scanning electron microscopy observation. RESULTS: circulatory phenomena were observed in acute inflammatory processes, characterized by hyperemia and vasodilation. Exudative and infiltrative phenomena were observed in the presence of foreign bodies and were characterized by leukocytic exudation (presence of polynuclear neutrophils), accompanied by lymphomonocytic infiltration. Proliferative phenomena were observed in post-traumatic forms of synovitis (ACL and meniscal injuries), characterized by hypertrophy and proliferation of villous formations. Degenerative and regressive phenomena were observed in cases of fibrous reaction (ankle impingement and joint stiffness) and were characterized by formation of dense fibrous connective tissue with hyaline patches, evolving towards sclerosis. CONCLUSIONS: the activation of inflammatory processes in patients who expose their joints to excessive stress may lead to the formation of hyperplastic tissue. Ultramicroscopic debris is usually capable of transforming the structural organization of the synovial tissue. LEVEL OF EVIDENCE: Level IV, observational case series.

Natural killer cells in HIV controller patients express an activated effector phenotype and do not up-regulate NKp44 on IL-2 stimulation.

Control of HIV replication in elite controller (EC) and long-term nonprogressor (LTNP) patients has been associated with efficient CD8(+)cytotoxic T-lymphocyte function. However, innate immunity may play a role in HIV control. We studied the expression of natural cytotoxicity receptors (NKp46, NKp30, and NKp44) and their induction over a short time frame (2-4 d) on activation of natural killer (NK) cells in 31 HIV controller patients (15 ECs, 16 LTNPs). In EC/LTNP, induction of NKp46 expression was normal but short (2 d), and NKp30 was induced to lower levels vs. healthy donors. Notably, in antiretroviral-treated aviremic progressor patients (TAPPs), no induction of NKp46 or NKp30 expression occurred. More importantly, EC/LTNP failed to induce expression of NKp44, a receptor efficiently induced in activated NK cells in TAPPs. The specific lack of NKp44 expression resulted in sharply decreased capability of killing target cells by NKp44, whereas TAPPs had conserved NKp44-mediated lysis. Importantly, conserved NK cell responses, accompanied by a selective defect in the NKp44-activating pathway, may result in lack of killing of uninfected CD4(+)NKp44Ligand(+) cells when induced by HIVgp41 peptide-S3, representing a relevant mechanism of CD4(+) depletion. In addition, peripheral NK cells from EC/LTNP had increased NKG2D expression, significant HLA-DR up-regulation, and a mature (NKG2A-CD57(+)killer cell Ig-like receptor(+)CD85j(+)) phenotype, with cytolytic function also against immature dendritic cells. Thus, NK cells in EC/LTNP can maintain substantially unchanged functional capabilities, whereas the lack of NKp44 induction may be related to CD4 maintenance, representing a hallmark of these patients.

Successfully treated HIV-infected patients have differential expression of NK cell receptors (NKp46 and NKp30) according to AIDS status at presentation.

Differences in innate immune responses may be associated with different capabilities of controlling HIV infection, not necessarily reflected by CD4(+) T-cell counts alone. We investigated by cytofluorometry the expression of NK cell receptors and ligands in 19 treated HIV-infected patients with CD4(+)<220 ml(-1) at presentation (11 AIDS, 8 non-AIDS) and 10 healthy donors. Expression of NKp46 and NKp30 was significantly higher in non-AIDS vs. AIDS patients. Overall, the level of NKp46 expression directly correlated with the degree of NK cell cytotoxicity. As compared to healthy donors, in both groups, there was a similar increase of CD69 and HLA-DR expression in NK cells that directly correlated with the presence of activation markers (HLA-DR) on CD4(+) and CD8(+) T cells. As compared to AIDS, in non-AIDS patients in vitro activated CD4(+) showed higher expression of MIC-A (NKG2D ligand), with significantly higher Nectin-2/DNAM-1 and MIC-A/NKG2D ratios. Thus, NK cell responses in AIDS and non-AIDS patients with similar CD4(+) counts significantly differ despite similar treatment. This suggests an involvement of innate mechanisms, in preventing AIDS-defining opportunistic infections in HIV infection and further suggests, that CD4(+) absolute counts alone, may be inadequate to explain differences in the clinical outcome.

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.

Receptor modulation and functional activation of human CD34+ Lin- -derived immature NK cells in vitro by Mycobacterium bovis Bacillus Calmette-Guerin (BCG).

It is not yet clear whether immature NK (iNK) cells are bystanders to or rather participate in immune responses to pathogens that may colocalize in areas of NK-cell maturation such as bone marrow or lymph nodes. Mycobacteria, including Bacillus Calmette-Guerin (BCG), have been shown to interact with peripheral NK cells and in vivo may colocalize in areas of iNK-cell development. We studied infection with BCG of human cord blood CD34(+) Lin(-)-derived cultures containing myelomonocytes and iNK cells in vitro. Increased iNK-cell DNAM-1 expression, transient natural cytotoxicity receptor modulation, and production of IFN-γ were observed. Transcriptional receptor modulation was associated to BCG challenge, which determined increased iNK-cell cytotoxic activity against tumor cell lines and also increased killing of immature dendritic cells (iDCs). No requirement for cell contact was recorded for BCG-induced iNK-cell activation, while cytokine production including IL-18, IL-10, GM-CSF, and TGF-ß contributed to the observed effects. Thus, iNK cells are affected by mycobacteria in vitro and may contribute to shaping of adaptive mature innate responses through iDC-iNK cross-talk. In addition, iNK-cell activation by BCG may represent a novel additional mechanism contributing to the effects observed upon BCG administration in vivo.

Involvement of activating NK cell receptors and their modulation in pathogen immunity.

Natural Killer (NK) cells are endowed with cell-structure-sensing receptors providing inhibitory protection from self-destruction (inhibitory NK receptors, iNKRs, including killer inhibitory receptors and other molecules) and rapid triggering potential leading to functional cell activation by Toll-like receptors (TLRs), cytokine receptors, and activating NK cell receptors including natural cytotoxicity receptors (NCRs, i.e., NKp46, NKp46, and NKp44). NCR and NKG2D recognize ligands on infected cells which may be endogenous or may directly bind to some structures derived from invading pathogens. In this paper, we address the known direct or indirect interactions between activating receptors and pathogens and their expression during chronic HIV and HCV infections.

Activating NK cell receptor expression/function (NKp30, NKp46, DNAM-1) during chronic viraemic HCV infection is associated with the outcome of combined treatment.

Specific NK cell killer inhibitory receptor (KIR):HLA haplotype combinations have been associated with successful clearance of acute and chronic HCV infection. Whether an imbalance of activating NK cell receptors also contributes to the outcome of treatment of chronic HCV infection, however, is not known. We studied peripheral NK cell phenotype and function in 28 chronically viraemic HCV genotype I treatment-naïve patients who underwent treatment with pegylated IFN-α and ribavirin. At baseline, chronically infected patients with sustained virological response (SVR) had reduced CD56(bright) CD16(+/-) cell populations, increased CD56(dull) CD16(+) NK cell proportions, and lower expression of NKp30, DNAM-1, and CD85j. Similarly, reduced NK cell IFN-γ production but increased degranulation was observed among nonresponding (NR) patients. After treatment, CD56(bright) CD16(+/-) NK cell numbers increased in both SVR and NR patients, with a parallel significant increase in activating NKp30 molecule densities in SVR patients only. In vitro experiments using purified NK cells in the presence of rIL-2 and IFN-α confirmed upregulation of NKp30 and also of NKp46 and DNAM-1 in patients with subsequent SVR. Thus, differences in patient NK cell receptor expression and modulation during chronic HCV-1 infection are associated with subsequent outcome of standard treatment. Individual activating receptor expression/function integrates with KIR:HLA genotype carriage to determine the clearance of HCV infection upon treatment.