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Dive into the research topics where Aristotelis Tsiakalos is active.

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Featured researches published by Aristotelis Tsiakalos.


Liver International | 2009

Acute-phase proteins as indicators of bacterial infection in patients with cirrhosis.

Aristotelis Tsiakalos; Aggelos Karatzaferis; Panayiotis D. Ziakas; Gregorios Hatzis

Background: Cirrhosis is associated with elevated levels of acute‐phase proteins (APP), irrespective of the presence of infection. This condition limits the clinical application of APP determination in cirrhotic patients with bacterial infections.


The Journal of Clinical Endocrinology and Metabolism | 2010

Pituitary Insufficiency after Infectious Meningitis: A Prospective Study

Aristotelis Tsiakalos; Ioannis D. Xynos; Nikolaos V. Sipsas; Gregory Kaltsas

CONTEXT Data from previous retrospective studies and case reports have suggested that infectious diseases of the central nervous system could cause pituitary deficiency. OBJECTIVE The aim of this prospective study was to investigate pituitary function in patients admitted with infectious meningitis during the acute phase and after 12 months. DESIGN Sixteen patients were studied. Basal pituitary function was assessed within 24 h of admission. Twelve of these patients underwent both basal and stimulated (insulin tolerance test) pituitary testing after 12 months. RESULTS During the acute phase, five patients (31.25%) showed apparent pituitary hormone deficiencies: two patients with gonadotropic and three patients with somatotropic deficiency. The exact status of corticosteroid sufficiency could not be defined in four patients, because no dynamic test was performed in the acute phase. In addition, seven patients (44%) had probable low T(3) syndrome. At 12 months, five patients (31.25%), two with viral and three with bacterial meningitis, had at least one anterior pituitary hormone deficiency. Two patients had isolated corticotropic and one isolated somatotropic deficiency. Combined corticotropic and somatotropic deficiencies were detected in two patients. New-onset deficiencies accounted for four of those five patients, whereas one patient demonstrated persisting somatotropic deficiency. All cases of low T(3) syndrome resolved at 12 months. CONCLUSIONS Isolated or combined pituitary deficiencies, which could present at the acute phase and/or occur at a later stage, can develop in a considerable proportion of patients after acute infectious meningitis.


The Journal of Infectious Diseases | 2011

Fine Epitope Specificity of Anti-erythropoietin Antibodies Reveals Molecular Mimicry With HIV-1 p17 Protein: A Pathogenetic Mechanism for HIV-1–Related Anemia

Aristotelis Tsiakalos; John G. Routsias; Theodore Kordossis; Haralampos M. Moutsopoulos; Athanasios G. Tzioufas; Nikolaos V. Sipsas

BACKGROUND Circulating autoantibodies to endogenous erythropoietin (anti-Epo) are detected in human immunodeficiency virus type 1 (HIV-1)-infected patients and represent a risk factor for anemia. The aim of this study was to map the B-cell epitopes on the Epo molecule. METHODS Serum samples from HIV-1-positive patients and healthy individuals were tested against overlapping peptides covering the entire sequence of Epo. RESULTS Serum samples from anti-Epo-positive patients exhibited significant binding to Epo epitopes spanning the following sequences: amino acids 1-20 (Ep1), amino acids 54-72 (Ep5), and amino acids 147-166 (Ep12). Structural analysis of erythropoietin revealed that the immunodominant epitopes, Ep1 and Ep12, comprise the interaction interface with Epo receptor (EpoR). Autoantibodies binding to this specific region are anticipated to inhibit the Epo-EpoR interaction, resulting in blunted erythropoiesis; this phenomenon is indicated by the significantly higher Epo levels and lower hemoglobin levels of anti-Ep1-positive patients compared with anti-Ep1-negative individuals. The region corresponding to the Ep1 epitope exhibited a 63% sequence homology with the ³⁴LVCASRELERFAVNPGLLE⁵² fragment of the HIV-1 p17 matrix protein. CONCLUSIONS These results suggest that the main body of anti-Epo is directed against a functional domain of Epo, and that the presence of anti-Epo can be considered to be a result of a molecular mimicry mechanism, which is caused by the similarity between the Ep1 region and the p17 protein.


Hepatobiliary & Pancreatic Diseases International | 2011

Portopulmonary hypertension and serum endothelin levels in hospitalized patients with cirrhosis

Aristotelis Tsiakalos; Gregorios Hatzis; Ioannis Moyssakis; Aggelos Karatzaferis; Panayiotis D. Ziakas; George E. Tzelepis

BACKGROUND Cirrhosis is associated with several extrahepatic manifestations including portopulmonary hypertension (PPHT). Recent data suggest that endothelins (ETs) are related to the pathophysiology of PPHT. The study aimed to measure serum ET levels in hospitalized cirrhotic patients and to determine their association with PPHT and patient outcome. METHODS Fifty-seven cirrhotic patients [43 males; median age 58 (28-87) years] underwent Doppler echocardiography. Patients with systolic pulmonary arterial pressure ≥40 mmHg and pulmonary acceleration time <100 ms were deemed to have PPHT. ET-1, 2, and 3 serum levels were measured with an ELISA assay. All-cause mortality was recorded over a median period of 24 months. RESULTS Nine out of 57 patients (15.8%) had PPHT. Among various clinical variables, only autoimmune hepatitis was associated with PPHT (OR=11.5; 95% CI, 1.58-83.4; P=0.01). ET-1 levels [9.1 (1.6-20.7) vs 2.5 (1.4-9.2) pg/mL, P=0.02] and the ET-1/ET-3 ratio [4.73 (0.9-22.4) vs 1.6 (0.3-10.7), P=0.02] were significantly higher in patients with PPHT than in those without. ET-2 and ET-3 levels did not differ between the two groups. There was no difference in survival between the two groups, although ET-1 levels were associated with an adverse outcome in Cox regression analysis (HR=1.11; 95% CI, 1.02-1.22; P=0.02 per unit increase in ET-1). CONCLUSION Our data suggest that ET-1 and the ET-1/ET-3 ratio are elevated in patients with PPHT and that ET-1 is associated with a poor outcome irrespective of PPHT.


Diagnostic Microbiology and Infectious Disease | 2012

Successful salvage therapy of refractory HIV-related cryptococcal meningitis with the combination of liposomal amphotericin B, voriconazole, and recombinant interferon-γ

Maria N. Gamaletsou; Nikolaos V. Sipsas; Dimitrios P. Kontoyiannis; Aristotelis Tsiakalos; Athanasios Kontos; Ioanna Stefanou; Theodore Kordossis

We present 2 cases of HIV-related cryptococcal meningitis, persisting after 3 and 9 months, respectively, of standard treatment. Both patients were treated successfully with a salvage regimen consisting of the combination of liposomal amphotericin B (3 mg/kg), intravenous voriconazole, and subcutaneous recombinant interferon γ-1b (200 μg thrice weekly). Voriconazole was administered at an increased dose (5 mg/kg, twice daily) to overcome interactions with co-administered ritonavir. In both patients, resolution of clinical signs and symptoms, as well as sterilization of cerebrospinal fluid cultures occurred after 10 weeks of salvage therapy. No major side effects were encountered. At the end of treatment, both patients were placed on maintenance therapy with oral fluconazole; no recurrence has been observed after 4 years of follow-up.


Journal of Infection | 2010

Circulating antibodies to endogenous erythropoietin and risk for HIV-1-related anemia

Aristotelis Tsiakalos; Theodore Kordossis; Panayiotis D. Ziakas; Athanasios Kontos; Despina Kyriaki; Nikolaos V. Sipsas

OBJECTIVES In a previous retrospective study we have shown that circulating antibodies to endogenous erythropoietin (anti-EPO) are associated with HIV-1-related anemia. The present longitudinal cohort study was conducted to examine the effect of anti-EPO on the risk of developing anemia over time. METHODS The study population consisted of 113 HIV-1 seropositive patients, who were screened for the presence of anti-EPO, with a mean+/-SD follow up of 105+/-40 months, for a total of 2190 visits. Anti-EPO were detected with an ELISA assay. RESULTS Anti-EPO were detected in 41% (46/113) at enrollment and 29% (320/1094) for all visits, and were associated with higher EPO levels for all visits (45.7+/-60.4 vs. 31.8+/-31.7 IU/ml, p<0.001). After adjusting for other significant confounders, anti-EPO has been associated with increased risk of anemia both at enrollment (odds ratio [OR], 5.07; 95% confidence interval [CI], 1.25-20.49) as well as for all visits ([OR], 2.15; 95% [CI]: 1.29-3.56). During follow up, a decline in prevalence of both anti-EPO and anemia was observed as the percentage of patients receiving HAART was increasing. CONCLUSIONS Anti-EPO are an independent risk factor for anemia in HIV-1-infected patients. HAART seems to reduce both anti-EPO and anemia prevalence.


Biologics: Targets & Therapy | 2008

Rituximab therapy in Greek patients with rheumatoid arthritis

Aristotelis Tsiakalos; Nestor K Avgoustidis; Haralampos M. Moutsopoulos

Objective: An open-label, prospective, uncontrolled study created to investigate clinical response, serological changes and side effects in Greek patients with rheumatoid arthritis (RA), after B-cell depletion with rituximab. Methods: Patients with high disease activity (disease activity score [DAS]-28 > 5.1) were selected for treatment with rituximab and received two infusions, 1 gr each, 2 weeks apart. Different disease parameters (visual analog scale, DAS-28, C-reactive protein [CRP], erythrocyte sedimentation rate, health assessment questionnaire, complement (C3), C4, rheumatoid factor [RF], anti-cyclic citrullinated peptide antibody [anti-CCP], swollen joint count, tender joint count, immunoglobulin M [IgM], IgG, IgA) were performed at base line, 2, 4, and 6 months post-treatment. Response was defined according to the American College of Rheumatology (ACR) criteria. Results: Seventeen patients received therapy. Treatment led to a reduction in various disease parameters. ACR20 was achieved in 41.11% of patients by week 8, 52.94% by week 16, and 82.35% by week 24. ACR50 was achieved in 5.88% by week 8, 41.17% by week 16, and 64.7% by week 24. ACR70 was achieved only by week 24 in 23.52% of patients. Statistical analysis has shown no differences in clinical response, between RF positive/negative patients, and anti-CCP-positive/negative patients, while decline of RF was better correlated with reduction of DAS-28 than with anti-CCP. Conclusions: Rituximab is a well tolerated and effective treatment in RA. Response was not correlated to RF or anti-CCP positivity. Decline of RF was associated with clinical response and reduction of DAS-28 and CRP.


Hepatobiliary & Pancreatic Diseases International | 2017

Circulating autoantibodies to endogenous erythropoietin are associated with chronic hepatitis C virus infection-related anemia

Aristotelis Tsiakalos; Theoharis Voumvas; Alexandros Psarris; Christina K Oikonomou; Dimitrios C. Ziogas; Ioannis Ketikoglou; Grigorios Hatzis; Nikolaos V. Sipsas

BACKGROUND Chronic hepatitis C virus (HCV) infection is associated with autoimmune phenomena and is often complicated by anemia. Circulating autoantibodies to endogenous erythropoietin (anti-EPO) have been detected in patients with chronic viral infections and were correlated to anemia. The present study aimed to determine anti-EPO prevalence in patients with chronic HCV infection and investigate its possible association with anemia. METHODS Ninety-three consecutive patients (62 males and 31 females) with chronic HCV infection, who had never received antiviral therapy or recombinant EPO, were enrolled in the study. Circulating anti-EPO were detected in the serum by using an ELISA assay. Quantitative determination of serum EPO levels was done by radioimmunoassay. HCV RNA viral load measurement and genotype sequencing were also performed. RESULTS Circulating anti-EPO were detected in 10.8% of HCV-infected patients and the prevalence of anti-EPO was significantly higher in patients with anemia (19.4% vs 5.3%, P=0.040) compared to that in those without anemia. Compared to anti-EPO negative cases, anti-EPO positive patients had higher frequency of anemia (70.0% vs 34.9%, P=0.030), lower EPO concentrations (median 16.35 vs 30.65 mU/mL, P=0.005), and higher HCV RNA viral load (median 891.5X103 vs 367.5X103 IU/mL, P=0.016). In multivariate regression analysis the presence of anti-EPO remained an independent predictor of anemia (adjusted OR: 14.303, 95% CI: 1.417-36.580, P=0.024). EPO response to anemia was less prominent among anti-EPO positive patients (P=0.001). CONCLUSIONS Circulating anti-EPO are detected in a significant proportion of treatment-naive HCV-infected patients and are independently associated with anemia, suggesting a further implication of autoimmunity in the pathophysiology of HCV-related anemia.


Thyroid | 2008

Antithyroid Drug-Induced Aplastic Anemia

Dimitrios Thomas; Anestis Moisidis; Aristotelis Tsiakalos; Krystallenia Alexandraki; Vassiliki Syriou; Gregory Kaltsas


European Journal of Orthopaedic Surgery and Traumatology | 2012

Seroprevalence of HIV, HBV and HCV in orthopaedic patients at a tertiary hospital in Greece

Spyros G. Pneumaticos; Christiana Savvidou; Aristotelis Tsiakalos; Nikolaos V. Sipsas

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Nikolaos V. Sipsas

National and Kapodistrian University of Athens

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Theodore Kordossis

National and Kapodistrian University of Athens

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Aggelos Karatzaferis

National and Kapodistrian University of Athens

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Athanasios G. Tzioufas

National and Kapodistrian University of Athens

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Athanasios Kontos

National and Kapodistrian University of Athens

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Gregorios Hatzis

National and Kapodistrian University of Athens

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Gregory Kaltsas

National and Kapodistrian University of Athens

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Haralampos M. Moutsopoulos

National and Kapodistrian University of Athens

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Alexandros Psarris

National and Kapodistrian University of Athens

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