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Biomedical subjects

A Nicosia

Publications and source records attributed to A Nicosia.

At least 37 records · Page 2Linked to original sources
PubMed2000

Binding of hepatitis C virus E2 glycoprotein to CD81 does not correlate with species permissiveness to infection.

Hepatitis C virus (HCV) glycoprotein E2 binds to human cells by interacting with the CD81 molecule, which has been proposed to be the viral receptor. A correlation between binding to CD81 and species permissiveness to HCV infection has also been reported. We have determined the sequence of CD81 from the tamarin, a primate species known to be refractory to HCV infection. Tamarin CD81 (t-CD81) differs from the human molecule at 5 amino acid positions (155, 163, 169, 180, and 196) within the large extracellular loop (LEL), where the binding site for E2 has been located. Soluble recombinant forms of human CD81 (h-CD81), t-CD81, and African green monkey CD81 (agm-CD81) LEL molecules were analyzed by enzyme-linked immunosorbent assay for binding to E2 glycoprotein. Both h-CD81 and t-CD81 molecules were able to bind E2. Competition experiments showed that the two receptors cross-compete and that the t-CD81 binds with stronger affinity than the human molecule. Recently, h-CD81 residue 186 has been characterized as the critical residue involved in the interaction with E2. Recombinant CD81 mutant proteins were expressed to test whether human and tamarin receptors interacted with E2 in a comparable manner. Mutation of residue 186 (F186L) dramatically reduced the binding capability of t-CD81, a result that has already been demonstrated for the human receptor, whereas the opposite mutation (L186F) in agm-CD81 resulted in a neat gain of binding activity. Finally, the in vitro data were confirmed by detection of E2 binding to cotton-top tamarin (Saguinus oedipus) cell line B95-8 expressing endogenous CD81. These results indicate that the binding of E2 to CD81 is not predictive of an infection-producing interaction between HCV and host cells.

Amino Acid Sequence↗
PubMed2000

Enhancing B- and T-cell immune response to a hepatitis C virus E2 DNA vaccine by intramuscular electrical gene transfer.

We describe an improved genetic immunization strategy for eliciting a full spectrum of anti-hepatitis C virus (HCV) envelope 2 (E2) glycoprotein responses in mammals through electrical gene transfer (EGT) of plasmid DNA into muscle fibers. Intramuscular injection of a plasmid encoding a cross-reactive hypervariable region 1 (HVR1) peptide mimic fused at the N terminus of the E2 ectodomain, followed by electrical stimulation treatment in the form of high-frequency, low-voltage electric pulses, induced more than 10-fold-higher expression levels in the transfected mouse tissue. As a result of this substantial increment of in vivo antigen production, the humoral response induced in mice, rats, and rabbits ranged from 10- to 30-fold higher than that induced by conventional naked DNA immunization. Consequently, immune sera from EGT-treated mice displayed a broader cross-reactivity against HVR1 variants from natural isolates than sera from injected animals that were not subjected to electrical stimulation. Cellular response against E2 epitopes specific for helper and cytotoxic T cells was significantly improved by EGT. The EGT-mediated enhancement of humoral and cellular immunity is antigen independent, since comparable increases in antibody response against ciliary neurotrophic factor or in specific anti-human immunodeficiency virus type 1 gag CD8(+) T cells were obtained in rats and mice. Thus, the method described potentially provides a safe, low-cost treatment that may be scaled up to humans and may hold the key for future development of prophylactic or therapeutic vaccines against HCV and other infectious diseases.

Adenovirus E2 Proteins↗
PubMed2000

Identification of amino acid residues in CD81 critical for interaction with hepatitis C virus envelope glycoprotein E2.

Human CD81 has been previously identified as the putative receptor for the hepatitis C virus envelope glycoprotein E2. The large extracellular loop (LEL) of human CD81 differs in four amino acid residues from that of the African green monkey (AGM), which does not bind E2. We mutated each of the four positions in human CD81 to the corresponding AGM residues and expressed them as soluble fusion LEL proteins in bacteria or as complete membrane proteins in mammalian cells. We found human amino acid 186 to be critical for the interaction with the viral envelope glycoprotein. This residue was also important for binding of certain anti-CD81 monoclonal antibodies. Mutating residues 188 and 196 did not affect E2 or antibody binding. Interestingly, mutation of residue 163 increased both E2 and antibody binding, suggesting that this amino acid contributes to the tertiary structure of CD81 and its ligand-binding ability. These observations have implications for the design of soluble high-affinity molecules that could target the CD81-E2 interaction site(s).

Amino Acid Sequence↗
PubMed1999

Hypervariable region 1 variants act as TCR antagonists for hepatitis C virus-specific CD4+ T cells.

In various human viral infections, the appearance of mutated epitopes displaying TCR antagonistic activity has been correlated with the severity and persistence of infection. In hepatitis C virus (HCV) infection, where the virus persistence has been associated with the rapid and substantial Ag modifications occurring during replication, TCR antagonism has been evidenced in CD8+ T cell responses. However, CD4+ T cell antagonism may be another important strategy by which HCV eludes a protective response, because sustained Th responses directed against several HCV Ags are associated with a self-limited course of infection. The data reported here represent the first evidence that variants of the hypervariable region (HVR1) of the putative Envelope 2 protein of HCV can act as powerful TCR antagonists for HVR1-specific CD4+ T cells isolated from HCV-infected individuals. Using classical antagonism assays, we observed strong inhibition of cellular proliferation and cytokine production when the agonist and the antagonist ligands were simultaneously presented by the same APCs. The presence in HVR1 of conserved residues, critical for binding to HLA-DR molecules, supports the function of HVR1 variants as TCR antagonists. In conclusion, our data evidence an antagonism phenomenon, which was achieved by naturally occurring class II-restricted T cell epitopes whose mechanism was addressed in terms of the antagonist capacity to inhibit agonist-mediated TCR down-regulation and early signal transduction.

Amino Acid Sequence↗
PubMed1999

A randomized comparison of trapidil (triazolopyrimidine), a platelet-derived growth factor antagonist, versus aspirin in prevention of angiographic restenosis after coronary artery Palmaz-Schatz stent implantation.

The aim of the study is to assess the safety of trapidil in the setting of coronary stenting and to evaluate its efficacy in reducing angiographic in-stent restenosis. One hundred eighteen patients undergoing Palmaz-Schatz stent implantation were randomly assigned to receive antiplatelet therapy using either aspirin (325 mg/d) or trapidil (400 mg/d), in combination with ticlopidine (500 mg) for the first month. At entry, both groups were comparable with regard to clinical, angiographic, and procedural characteristics. At 6-month angiographic follow-up, >50% restenosis occurred in 15 of 52 lesions (28.8%) of the aspirin group and in 14 of 47 lesions (29.8%) of the trapidil group (P=not significant, NS). At 6-month clinical follow-up, there was no difference in the two groups in the rate of adverse events (2.0% vs. 2.1%, P=NS), medication side effects (4.0% vs. 4.2%, P=NS), and peripheral vascular complications (4.0% vs. 4.2%, P=NS). In conclusion, treatment with trapidil seems to be associated with a similar incidence of stent restenosis and adverse cardiac events as compared to aspirin and could be a valuable alternative to aspirin in the setting of coronary stenting.

Aged↗
PubMed1999

Antibody responses to hepatitis C virus hypervariable region 1: evidence for cross-reactivity and immune-mediated sequence variation.

Sequence heterogeneity of hepatitis C virus (HCV) is unevenly distributed along the genome, and maximal variation is confined to a short sequence of the HCV second envelope glycoprotein (E2), designated hypervariable region 1 (HVR1), whose biological function is still undefined. We prospectively studied serological responses to synthetic oligopeptides derived from HVR1 sequences of patients with acute and chronic HCV infection obtained at baseline and after a defined follow-up period. Extensive serological cross-reactivity for unrelated HVR1 peptides was observed in the majority of the patients. Antibody response was restricted to the IgG1 isotype and was focused on the carboxyterminal end of the HVR1 region. Cross-reactive antibodies could be readily elicited following immunization of mice with multiple antigenic peptides carrying HVR1 sequences derived from our patients. The vigor and heterogeneity of cross-reactive antibody responses were significantly higher in patients with chronic hepatitis compared with those with acute hepatitis and in patients infected with HCV type 2 compared with patients infected with other viral genotypes (predominantly type 1), which suggest that higher time-related HVR1 sequence diversification previously described for type 2 may result from immune selection. The finding of a statistically significant correlation between HVR1 sequence variation, and intensity, and cross-reactivity of humoral immune responses provided stronger evidence in support of the contention that HCV variant selection is driven by the host's immune pressure.

Adolescent↗
PubMed1999

Usefulness of platelet glycoprotein IIb/IIIa inhibitors in coronary stenting for reconstruction of complex lesions: procedural and 30 day outcome.

BACKGROUND: Intracoronary stent implantation during percutaneous transluminal coronary angioplasty (PTCA) has shown favorable results, reducing acute complications associated with PTCA, such as coronary artery dissection and abrupt or threatened vessel closure. However, treatment of lesions with a complex morphology and diffuse disease, requiring long or multiple coronary stents, is still associated with a poorer outcome. We investigated the hypothesis that abciximab might lead to a different outcome in patients with complex coronary lesions, which require long or multiple stent implantation. METHODS: One hundred and six patients were randomized to receive either a combination of abciximab (bolus and 12 hour infusion) and weight-adjusted low-dose heparin or weight-adjusted heparin alone and followed up to 30 days. RESULTS: The procedural success rate was 100% in both groups of patients. In the control group a composite rate of major adverse events such as any death irrespective of cause, Q wave or non-Q wave myocardial infarction, acute or subacute stent thrombosis and urgent revascularization of 15.3% was shown at 30-day follow-up. The use of abciximab reduced the composite adverse event rate to 3.7% (76% absolute reduction, p < 0.05). CONCLUSIONS: The use of abciximab during high risk stenting is safe and reduces the risk of cardiac events at 30-day follow-up as compared to standard treatment with heparin. A longer follow-up period is warranted to confirm the beneficial effects observed at 30 days with abciximab in this setting.

Abciximab↗
PubMed1998

Efficient display of an HCV cDNA expression library as C-terminal fusion to the capsid protein D of bacteriophage lambda.

We describe the construction and characterization of a hepatitis C virus (HCV) cDNA expression library displayed as a fusion to the carboxy terminus of the capsid protein D of bacteriophage lambda. cDNA inserts were obtained by tagged random-priming of the HCV genome and cloned into a lambda vector from which chimeric phage bearing both wild-type D protein and D fusion products on the capsid surface were produced. The resulting library was affinity-selected with anti-HCV human monoclonal antibodies recognizing linear or conformational epitopes, and human sera from HCV-infected patients. Selection was monitored by immuno-screening experiments, ELISA, and sequence analysis of positive clones. The performance of this library was compared with two additional HCV cDNA display libraries generated as N-terminal fusions to the III and VIII capsid proteins of filamentous phage M13. The results obtained demonstrate the great potential of the lambda display system for constructing complex cDNA libraries for natural ligand discovery.

Antibodies, Monoclonal↗
PubMed1998

Towards a solution for hepatitis C virus hypervariability: mimotopes of the hypervariable region 1 can induce antibodies cross-reacting with a large number of viral variants.

The hypervariable region 1 (HVR1) of the putative envelope protein E2 of hepatitis C virus (HCV) is the most variable antigenic fragment in the whole viral genome and is mainly responsible for the large inter-and intra-individual heterogeneity of the infecting virus. It contains a principal neutralization epitope and has been proposed as the major player in the mechanism of escape from host immune response. Since anti-HVR1 antibodies are the only species shown to possess protective activity up to date, developing an effective prevention therapy is a very difficult task. We have approached the problem of HVR1 variability by deriving a consensus profile from >200 HVR1 sequences from different viral isolates and used it as a template to generate a vast repertoire of synthetic HVR1 surrogates displayed on M13 bacteriophage. This library was affinity selected using many different sera from infected patients. Phages were identified which react very frequently with patients' sera and bind serum antibodies that cross-react with a large panel of HVR1 peptides derived from natural HCV variants. When injected into experimental animals, the 'mimotopes' with the highest cross-reactivity induced antibodies which recognized the same panel of natural HVR1 variants. In these mimotopes we identified a sequence pattern responsible for the observed cross-reactivity. These data may hold the key for future development of a prophylactic vaccine against HCV.

Amino Acid Sequence↗
PubMed1998

Identification of peptides binding to IgG in the CSF of multiple sclerosis patients.

Phage displayed random peptide libraries were screened in order to identify phagotopes reacting with the IgG present in the cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients. Six families of phagotopes each composed of different isolates were identified. These phagotopes were used as reagents, to characterise IgG present in the CSF of MS patients. The following results were obtained: (a) CSF antibodies from different patients display different specificities; (b) anti-phagotope antibodies are also present in the serum of MS patients; (c) Anti-phagotope antibodies are equally frequent in the serum of MS patients and of healthy individuals; (d) some of the anti-phagotope antibodies are enriched in the CSF of MS patients. These data show that the natural antigen(s) recognised by CSF antibodies is rather common in the general population. By using the selected phagotopes as immunogens in rabbits, we have derived large quantities of anti-phagotope antisera which can provide for useful tools toward the identification of the natural antigen(s) recognised by MS CSF antibodies.

Adult↗
PubMed1998

CSF-enriched antibodies do not share specificities among MS patients.

The specificity of the oligoclonal immunoglobulins found in MS CSF is unknown. We have previously shown that random peptide libraries displayed on phage can be used to identify specific ligands for CSF antibodies. Here we describe the use of this tool in the attempt to identify MS-specific CSF-enriched antibody reactivities with potential pathogenic, diagnostic or prognostic value. Applying different experimental strategies, several ligands reacting with CSF-enriched antibodies were identified. When tested against a panel of 55 MS patients, none of the ligands found were recognized by antibodies shared by any two patients. We used the selected peptides to demonstrate the stability in time of CSF-enriched antibodies notwithstanding disease progression.

Adult↗
PubMed1998

[Dissolution of acute stent thrombosis by abciximab bolus].

Abciximab, REOPRO, a potent inhibitor of platelet aggregation via glycoprotein IIb/IIIa inhibition, has shown to be effective in the prevention of short and long-term complications of percutaneous coronary interventions. Very few reports on the role of this drug in the setting of acute stent thrombosis have been published. We report 1 case of the effectiveness of REOPRO in the complete lysis of stent thrombus with reperfusion of the coronary vessel and its collaterals. This case suggests an important role of platelets in the setting of acute stent thrombosis and a thrombolytic effect of REOPRO.

Abciximab↗
PubMed1998

[Safety, feasibility and efficacy of a new single-wire stent in the treatment of complex coronary lesions: the angiostent].

The angiostent is a single wire, flexible, highly radiopaque, balloon expandable stent. To evaluate the feasibility and safety of the deployment of this new stent, we report the clinical and procedural results of 70 procedures performed in 51 native coronary arteries of 48 patients, with objective evidence of ischemia. The target lesion was located in the left anterior descending artery in 18 (36%) cases, in the circumflex artery in 16 (31%) cases and in the right coronary artery in 17 (33%) cases. Mean reference vessel diameter was 3.2 +/- 0.4 mm and the minimal luminal diameter was 0.4 +/- 0.3 mm, with a mean diameter stenosis of 86 +/- 10%. Type B2 and C lesions were encountered in 56% of the cases. More than one angiostent was implanted in 14 vessels and multiple stenting was accomplished with the use of different stents in 8 coronary arteries. No major complications were reported. The post-procedural minimal luminal diameter was 3.2 +/- 0.4 mm with a mean diameter stenosis of 1.4 +/- 3.7%. In 25 cases (49%) major side branches raised from the stented segment and in all but one remained patent. In conclusion, the implantation of the angiostent is safe, feasible and effective, as it can be easily deployed at the lesion site, used for the treatment of complex lesions and preserves the patency of jailed side-branches.

Anticoagulants↗
PubMed1998

[Endothelin-1 variation in the coronary circulation during angioplasty with a stent implant].

Endothelin-1 (ET-1) is an endothelium-derived mediator with vasoconstrictive and mitogenic activity which stimulates vascular smooth muscle cell proliferation. The aim of this study was to evaluate ET-1 production during percutaneous transluminal coronary angioplasty (PTCA) and elective stent implantation. We hypothesized that the additional vessel wall trauma induced by stent deployment might be associated with a greater production of ET-1. To this end, ET-1 levels were measured in 18 patients undergoing PTCA and stenting (12 with left anterior descending coronary artery stenosis and 6 with circumflex artery lesion). The sampling sites were the coronary ostium and coronary sinus in basal conditions (before the procedure), during first balloon inflation, and 5, 20, 60 min after the end of first balloon inflation. At baseline, ET-1 levels were higher in the coronary sinus than in coronary ostium (1.58 +/- 0.22 vs 1.29 +/- 0.20 pg/ml, p < 0.001). During first balloon inflation, ET-1 coronary sinus levels significantly diminished with respect to the basal levels (1.08 +/- 0.32 vs 1.58 +/- 0.22 pg/ml, p < 0.001). Further significant variations of ET-1 levels were not detected neither following the first balloon inflation nor after stent deployment. In conclusion, the culprit lesion seems to produce most of ET-1 circulating in the coronary tree. This is demonstrated by higher ET-1 levels in the coronary sinus compared to coronary ostium at baseline, and even more by the significant ET-1 reduction in the coronary sinus during first balloon inflation. Despite our expectations, we did not detect any significant ET-1 increase during stent deployment.

Aged↗