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O Turriziani

Publications and source records attributed to O Turriziani.

35 records · Page 2Linked to original sources
PubMed1997

Induction of the multidrug-transporter P-glycoprotein by 3'-azido-3'-deoxythymidine (AZT) treatment in tumor cell lines.

A major form of multidrug resistance, which represents a serious obstacle to the success of chemotherapy, is caused by the over-expression of MDR-1 gene encoded P-glycoprotein. The present investigation was aimed to determine whether AZT, a cytostatic agent that interferes with the human immunodeficiency virus replication, is able to induce MDR-1 expression in tumor cells. After a short term exposure of human lymphoblastoid cells to AZT MDR-1 P-glycoprotein was found in the treated cells. This ATP-dependent drug-efflux pump interferred with cytotoxic efficacy of anticancer drugs such as vinblastine. This phenomenon should be carefully considered during anti-viral and anti-tumoral combined chemotherapies in AIDS patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Further study of the mechanism underlying the cellular resistance to AZT.

It has previously been shown that the lymphoblastoid cell line CEM, when propagated in the presence of increasing concentrations of 3'-azido-3'-deoxythymidine, became defective in thymidine kinase activity and resistant to the cytostatic and antiviral activities of AZT. Here we describe the characterization of this cell line (CEMAZT), which revealed that: (i) the defect in TK activity is stable; (ii) TK specific mRNA levels are lower than in the parental line; (iii) the defect of TK activity may be sufficient to produce a lower amount of AZTDP, independently of the activity of thymidylate kinase which does not seem to be defective. Taken together these findings indicate that in CEMAZT the lack of inhibition by AZT may depend only on the defect of TK activity. Also, in preliminary studies of lymphocytes from AZT-treated and untreated patients we observed a metabolic behaviour comparable to that described for CEMAZT and CEM cells.

Anti-HIV Agents↗
PubMed1996

Long-term exposure to zidovudine affects in vitro and in vivo the efficiency of phosphorylation of thymidine kinase.

The purpose of this study was to investigate the mechanism of acquired cellular resistance to AZT, a mechanism that has been described as a potential source of drug resistance in addition to viral mutations. To study this phenomenon the kinetics parameters of thymidine kinase (TK) activity have been defined in CEMazt, a cell line previously selected for resistance to AZT, in comparison with the parental AZT-sensitive CEM cells. The results revealed that the value of the maximum velocity (Vmax) of TK activity for deoxythymidine (dThd) phosphorylation is decreased in CEMazt as compared to the wild-type cell line (Vmax: CEM = 105.3 +/- 17.6 nmol/hr/mg of protein; CEMazt = 0.3 +/- 0.02 nmol/hr/mg of protein; p < 0.001). Furthermore, the enzyme affinity versus dThd is lower in CEMazt as compared to CEM (Km: CEM = 0.9 +/- 0.2 microM; CEMazt = 1.6 +/- 0.2 microM; p < 0.01). Consequently phosphorylation efficiency, expressed as the ratio between Vmax and Km, is also reduced in CEMazt (p < 0.001). To evaluate whether such a phenomenon may also occur in patients, ex vivo experiments were carried out by using PBMCs from HIV-infected patients, treated or not treated with AZT. The results (mean values from 10 patients for each group) indicate that a prolonged treatment (> 6 months) with AZT may modify the enzymatic kinetics of TK, leading to a significant reduction in the phosphorylation efficiency of the enzyme (4.07 +/- 1.7 in treated patients versus 13.5 +/- 1.7 in untreated patients; p < 0.001). These results indicate that AZT treatment can also induce a defect in TK activity in patients.

Cell Line↗
PubMed1995

Treatment with natural IFN of hepatitis C patients with or without antibodies to recombinant IFN.

The purpose of this study was to evaluate if a retreatment with natural human interferon alpha could lead to a recovery of the therapeutic responsiveness in non-responder patients with chronic hepatitis C who did (9 cases) or did not (14 cases) develop anti-interferon neutralizing antibodies while on treatment with recombinant interferon alpha2a. During retreatment, no patient developed detectable levels of neutralizing antibodies to natural interferon. At the end of retreatment, 6/9 positive patients showed a complete response to natural interferon therapy, while only 1/14 negative patients had a partial response. These data suggest that a second course of treatment with the natural preparation may be useful in patients who failed to respond to an earlier course of recombinant interferon, particularly the anti-interferon positive patients who showed hepatitis reactivation after an initial response concomitantly with antibody appearance. Conversely, a second course of natural interferon therapy might be useless in cases in which the lack of response is not associated to antibody development.

Antibodies↗
PubMed1994

Zidovudine induces the expression of cellular resistance affecting its antiviral activity.

We have previously shown that multidrug-resistant cells expressing the multidrug transporter P-glycoprotein are less sensitive to the antiviral activity of AZT. Subsequently, we addressed the question whether AZT itself is able to induce cellular resistance to the drug. Indeed, CEM cells propagated in the presence of increasing concentrations of AZT become resistant to the antigrowth and antiviral activity of AZT but do not express detectable level of P-glycoprotein. Sensitivity of these cells to other compounds, such as vinblastine, vincristine, ddI, and ddC remained unchanged, indicating that, in contrast to P-glycoprotein-positive cells, AZT-induced resistance is specific for AZT. Interestingly, in AZT-induced resistant cells the intracellular accumulation of AZT and exogenous deoxythymidine, as well as thymidine kinase activity, are significantly reduced when compared with the parental cell line. Our findings show that AZT itself may directly induce the expression of cellular mechanisms leading to the acquisition of specific cellular resistance that can affect its antiviral activity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Identification of an amino acid substitution involved in the reduction of sensitivity of HIV-1 to an inhibitor of viral proteinase.

Clones derived from HIV variants previously characterized as resistant to Ro31-8959, an inhibitor of viral proteinase (PR), were sequenced. Substitution of glycine by valine at position 48 of the PR protein was found. None of the 20 clones derived from wild type HTLV-IIIB contain this mutation. Since such a position is located in a conserved region of PR, it is possible that the substitution can affect the interaction of the enzyme with the inhibitor.

Base Sequence↗
PubMed1992

In vitro selection of human immunodeficiency virus type 1 resistant to 3'-azido-3'-deoxythymidine.

3'-Azido-3'-deoxythymidine (AZT)-resistant human immunodeficiency virus type 1 (HIV-1) was obtained by growing HTLV-IIIB in C8166 cell cultures in the presence of inhibitory concentrations of AZT. The AZT-resistant HIV-1 was capable of replicating, as measured by infectious virus yield, and inducing cytopathic effect in the presence of AZT concentrations able to completely suppress the replication of parental HTLV-IIIB. Cloning of the AZT-resistant HIV-1 revealed that a number of different variants of HIV-1 with various degrees of sensitivity to AZT emerged during propagation of HTLV-IIIB in C8166 cells in the presence of the drug. PCR experiments performed on DNA extracted from C8166 cells infected with a resistant strain revealed that viral DNA was produced in the presence of inhibitory concentrations of AZT, while viral DNA in C8166 cells infected with the parental virus was drastically inhibited. Reverse transcriptase isolated from the AZT-resistant HIV-1 variant failed to show resistance to AZT 5'-triphosphate.

Antiviral Agents↗
PubMed1992

Resistance of HIV-1 to AZT might also involve the cellular expression of multidrug resistance P-glycoprotein.

Resistance of tumor cells to the antigrowth activity of several cytotoxic compounds has been associated with the expression of the so-called multidrug resistance protein or P-glycoprotein. This article addresses the question whether the expression of such protein could also affect the sensitivity of HIV to AZT. Our data indicate that this possibility does exist. In fact, multidrug-resistant CEM VBL100 cells, which express high levels of P-glycoprotein, are less sensitive to both the antiproliferative activity and the antiviral action of AZT. Additionally, our data suggest that this phenomenon is specifically mediated by P-glycoprotein since trifluoroperazine, which is known to circumvent multidrug resistance due to the action on P-glycoprotein, increases the intracellular accumulation of AZT and affects the sensitivity of HIV to AZT. Although the biological and clinical significance of these observations has still to be established, this study suggests that cellular factors, other than virus itself, should be taken into account to address the phenomenon of drug resistance of HIV.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

[Acquired immunodeficiency virus (HIV-1). Biological aspects and virological diagnosis].

The etiologic agent of the acquired immunodeficiency syndrome is a retrovirus included in the subclass of lentiviruses in view of certain characteristics common to these viruses. Their similarity is mainly represented by the extreme slowness of disease manifestation and by the fact that HIV, like other lentiviruses, spreads within the organism in spite of an immune reaction. The mechanism of replication is not dissimilar to that of other retroviruses except for the expression of a particularly large number of regulating genes the most important of which are called tat, rev, and nef. Further genes with a probable regulating function are nef, vpr, and vpx. In the field of diagnostic virology, together with normal isolation tests, a technique that has become particularly important is PCR (polymerase chain reaction) which allows to obtain a relevant amount of specific viral DNA sequences by the use of a DNA polymerase and specific primers.

AIDS Serodiagnosis↗
PubMed1991

Neutralizing antibodies to interferon-alpha: relative frequency in patients treated with different interferon preparations.

The frequencies of antibody development so far reported in patients treated with different interferons (IFNs) are not readily comparable because of differences in treatment regimens and assay methods. Thus the frequency of neutralizing antibody development was analyzed in a large sample of sera derived from a relatively homogeneous group of patients treated with different IFN-alpha preparations. The frequency of developing neutralizing antibody to IFN varied according to the IFN given. Particularly, the seroconversion frequency was significantly higher in patients treated with recombinant IFN-alpha 2a (20.2%) than in patients treated with either recombinant IFN-alpha 2b (6.9%) or IFN-alpha N1 (1.2%), a lymphoblastoid IFN-alpha. Furthermore, sera obtained from patients treated with either recombinant IFN neutralized both types of recombinant IFNs but failed to neutralize IFN-alpha N1.

Antibodies↗
PubMed1991

Prostaglandin A inhibits replication of human immunodeficiency virus during acute infection.

An antiviral effect of prostaglandins (PGs) of the A series on the replication of human immunodeficiency virus (HIV) has been determined. In the T cell line C8166 under single growth cycle conditions, PGA1 reduced the number of infectious progeny 1000-fold in the absence of cytotoxicity. Thus, inhibition of HIV replication by PGA1 represents a true antiviral phenomenon. The number and size of virus-induced syncytia, and the amount of viral antigen were also drastically reduced. The effect was specific for PGAs because PGA2 was also inhibitory, whereas PGB1, PGE1 and PGE2 were inactive. Virus adsorption and penetration do not appear to be targets of antiviral action because PGA1 substantially reduced virus replication, even when added 5 h post-infection. PGA1 did not inhibit viral reverse transcriptase, as determined by in vitro assays, suggesting that its antiviral action is not the consequence of a direct inhibitory effect on this enzyme. PGA1 also inhibited the replication of HIV-1 in CEM x 174 cells, but with less potency. Previously, intravenous infusion of PGA1 into human volunteers has shown no significant deleterious side-effects and thus these observations suggest that PGAs might have potential as antiviral agents in humans.

Antiviral Agents↗
PubMedDate not supplied

Significant reduction in HIV-1 plasma viral load but not in proviral infected cells during sub-optimal antiretroviral therapy.

Attempts to eradicate HIV infection through highly active antiretroviral therapy (HAART) in the very early stages of the infection have failed due to the resumption of viral replication from unknown reservoirs. It has been postulated that antiretroviral therapy capable of suppressing viral replication, as shown by reduction of HIV-RNA copies in plasma and lymph nodes, should have less effect on the number of HIV-DNA carrying cells in the same districts. To test this hypothesis, plasma viremia and the proportion of provirally infected cells in peripheral blood and in lymph nodes were measured in patients at 3 and 6 months of treatment with zidovudine plus lamivudine. All patients showed a significant decrease in plasma viremia at 3 months that was maintained at 6 months (mean values of 1.6 +/- 0.6 log10 from baseline). Conversely the proportion of HIV-DNA carrying cells slightly declined at 3 months but remained substantially stable thereafter both in peripheral blood and in lymph nodes. Taken together these data suggest that this therapeutic regimen, although sub-optimal, is effective in significantly reducing the virus production by productively infected cells but does not seem to substantially affect the load of provirally infected cells.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Mechanism of production of interferon-gamma: role of arachidonic acid metabolites.

The effects of arachidonic acid metabolites on mitogen-induced interferon (IFN)-gamma production by human peripheral blood mononuclear cells (PBMC) were examined. Both prostaglandins E2 (PGE2) and leukotrienes B4 (LTB4) were produced after macrophage activation stimulated by galactose oxidase (GO) and Staphylococcal enterotoxin B (SEB), two well known inducers of IFN-gamma. To test the involvement of PGE2 and LTB4 in IFN-gamma production, GO- and SEB-activated PBMC were treated with two inhibitors of cyclooxygenase (aspirin and indomethacin) and with an inhibitor of lipoxygenase [nordihydroguaiaretic acid (NDGA)]. The results of these experiments showed that aspirin and indomethacin cause a marked increase of IFN-gamma production by GO- and SEB-activated PBMC. On the contrary, NDGA treatment reduced IFN-gamma production induced by the same agents. Moreover, whereas the addition of exogenous PGE2 reduces IFN gamma production, the addition of exogenous LTB4 does not affect IFN-gamma production. Taken together these findings indicate that arachidonic acid metabolites, produced during mitogenic activation, are involved in the regulation of IFN-gamma production and suggest that, in our system, LTB4 exerts a positive modulating signal while PGE2 represents a negative signal.

5,8,11,14-Eicosatetraynoic Acid↗
PubMedDate not supplied

[A micromethod for assaying HIV reverse transcriptase].

A micromethod for assaying HIV reverse transcriptase was developed. Accuracy, and sensitivity of the micromethod were comparable to those of the traditional macromethod. The micromethod is easy to perform and can be used in non specialised laboratories.

AIDS Serodiagnosis↗
PubMedDate not supplied

[Acid-labile alpha interferon produced by peripheral blood mononuclear cells stimulated by cells infected by HIV].

Acquired immunodeficiency syndrome (AIDS) is caused by infection with T-cell tropic retrovirus HIV. The disease is characterized by a profound defect in cell-mediated immunity and a number of serologic abnormalities. Among the serologic abnormalities, the presence of an unusual acid-labile interferon (IFN) has been repeatedly found, and it is considered to be a marker of infection HIV evolving toward illness. Because little is known about the relationships existing between the etiologic agent of AIDS (i.e. HIV) and acid-labile IFN alpha, we approached this problem by testing whether acid-labile IFN alpha is induced in vitro by this virus. In this paper we compared the IFN-inducing activity of free, infectious HIV to that of HIV-infected cells. A number of other enveloped viruses and virus-infected cells were used as controls. Interferon inducing activity by virions as compared to virus-infected cells was determined by incubating human PBMC either with VSV, HSV, and HIV or with cells infected with the same viruses. In this case cells were fixed with glutaraldehyde to prevent virus shedding. While VSV and HSV induced production of acid-stable IFN both as free virions and as virus-infected cells, HIV induced acid-stable IFN when applied as a viral suspension, but it did produce acid-labile IFN when virus-infected cells were used as the inducer. In fact the IFN produced under these circumstances lost more than 80% of its activity when treated to pH2, no matter whether H9/HIV or HIV infected PBMC were used as the inducer. Because acid-lability is a peculiar property of IFN gamma, whereas both native and cloned IFN alpha are completely stable under acid conditions, we compared the IFNs induced by either HIV and HIV-infected cells to standard IFN alpha and gamma preparations with respect to (i) acid stability (ii) neutralization with specific antisera (iii) apparent molecular weight estimated by gel filtration. Results indicate that HIV-induced IFN behaves exactly as standard IFN alpha, as it was completely stable at pH2, totally inactivated by anti-IFN alpha and not by anti-IFN gamma serum, and had apparent molecular weight of 20,000; conversely IFN induced by HIV-infected cells, both H9/HIV and PBMC/HIV, although sharing with IFN alpha both molecular weight and antigenic properties, was inactivated by acid treatment by more than 80%.(ABSTRACT TRUNCATED AT 400 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Alteration of thymidine kinase activity in cells treated with an antiviral agent.

A lymphoblastoid cell line, CEM, was rendered resistant to zidovudine (AZT) in vitro by exposure to low but gradually increasing concentrations of the drug. This type of cellular resistance seems to be due to a defect of thymidine kinase (TK) activity that is acquired by cells grown in the presence of AZT. In fact, enzymatic studies with extracts from AZT-resistant cells (CEMazt), have shown that the value of the maximum velocity (Vmax) of TK activity measured with AZT and for deoxythymidine (dThd) is decreased as compared to sensitive CEM cells. Furthermore, the enzyme affinity for AZT and dThd is reduced in CEMazt. Further experiments have shown that such cells do not show resistance to other nucleoside analogs, such as ddI, ddC, AraT and D4T, suggesting that the phosphorylation pathways different from those involving TK are unaltered. Ex vivo experiments performed by using peripheral blood mononuclear cells (PBMC) from HIV infected individuals revealed that a prolonged treatment with AZT may modify the affinity of TK for dThd, thus suggesting that the aforementioned phenomenon may occur also in vivo.

Anti-HIV Agents↗