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Biomedical subjects

J T Stapleton

Publications and source records attributed to J T Stapleton.

At least 19 recordsLinked to original sources
PubMed2007

Risk factors for hepatitis C fibrosis: a prospective study of United States veterans compared with nonveterans.

Chronic hepatitis C virus (HCV) infection causes cirrhosis in many infected patients; however, a better understanding of the risk factors for fibrosis progression in high HCV prevalence groups such as US veterans is needed. We wished to compare the demographic, clinical characteristics, and independent variables that influence fibrosis in US veterans vs nonveterans with chronic HCV. HCV-seropositive US veterans (n = 459) and nonveterans (n = 395) prospectively completed a detailed medical, social and occupational questionnaire. Clinical factors for progressive liver disease were compared between veterans and nonveterans and fibrosis stage assessed on liver biopsies (168 veterans and 208 nonveterans). Using polychotomous logistic regression, fibrosis was analysed as both a progressive and categorical outcome to determine independent risk factors for both patient groups. Although veterans were significantly older and had higher lifetime alcohol consumption than nonveterans, their median fibrosis scores did not differ from nonveterans. By univariate analysis, alanine aminotransferase, necroinflammatory activity (NIA), and cryoglobulin positivity were associated with fibrosis in veterans and nonveterans (P < 0.05, all comparisons), whereas steatosis was associated with fibrosis only in nonveterans (P < 0.0001). By multivariate analysis, NIA was an independent risk factor for fibrosis in both groups (P < 0.01). However, fibrosis in nonveterans was also independently associated with steatosis, significant alcohol consumption and age (P < 0.04, all comparisons). Independent risk factors for fibrosis vary among high HCV prevalence groups such as veterans when compared with nonveterans. Understanding specific patient cohort effects is important for determining independent risk factors for disease progression in chronic HCV infection.

Adult↗
PubMed2006

Effect of GB virus C on response to antiretroviral therapy in HIV-infected Brazilians.

OBJECTIVES: GB virus C (GBV-C) infection is associated with delayed mortality in HIV-infected people in most, but not all, studies. Previous investigations of the effect of GBV-C viraemia on response to antiretroviral therapy (ART) were inconclusive. To determine the effect of GBV-C on ART, we retrospectively analysed plasma samples taken from patients in a prospective randomized clinical trial of ART in HIV-positive Brazilians. METHODS: GBV-C viraemia was characterized by testing stored serum samples from 175 participants by reverse transcriptase-polymerase chain reaction (RT-PCR). Subjects were randomized to receive indinavir (n=59), zidovudine and lamivudine (n=58), or zidovudine, lamivudine and indinavir (n=58). The effect of GBV-C viraemia on the average change in HIV viral load and CD4 count following initiation of therapy was evaluated in a multiple regression analysis. RESULTS: The prevalence of GBV-C viraemia was similar to that observed in previous studies (24%). HIV viral load decreased following ART to a significantly greater extent in patients with GBV-C viraemia (by 0.48 log(10) HIV-1 RNA copies/mL, P=0.009, adjusting for age, ART group, and baseline CD4 count). Although there was no significant difference in change in CD4 count between individuals with and without GBV-C viraemia overall, CD4 counts were higher following 48 weeks of therapy in GBV-C viraemic individuals receiving the least potent ART regimen (zidovudine and lamivudine) compared with those without GBV-C infection. CONCLUSIONS: GBV-C viraemia is associated with an enhanced reduction of HIV viral load in response to ART. In this study of treatment-naive individuals during 48 weeks of follow up, patients with GBV-C viraemia had reductions in HIV viral load that were approximately 0.5 log copies/mL greater than those found in patients without GBV-C viraemia. This is similar to reductions observed with nucleoside reverse transcriptase inhibitors.

Adult↗
PubMed2006

Effect of early and late GB virus C viraemia on survival of HIV-infected individuals: a meta-analysis.

OBJECTIVES: To conduct a meta-analysis to synthesize the evidence regarding the effect of co-infection with GB virus C (GBV-C) on survival of HIV-infected individuals, and to estimate the effect. METHODS: A Bayesian meta-analysis was conducted to synthesize evidence from eligible studies. Prospective survival studies of HIV-1-infected individuals, with outcome defined as time from baseline to all-cause death, were included and classified by whether GBV-C status was determined in early or late HIV disease. The primary measure was the hazard ratio (HR) of death for HIV-infected individuals with GBV-C infection versus those without GBV-C infection. RESULTS: Eleven studies from eight publications met the inclusion criteria. For studies with GBV-C status measured 2 years or less after HIV seroconversion (912 subjects), the combined HR was 0.88 [95% credible interval (CI) 0.30, 1.50]. For studies with GBV-C status measured more than 2 years after HIV seroconversion (1294 subjects), the combined HR was 0.41 (95% CI 0.23, 0.69). CONCLUSIONS: No conclusive evidence was found of an association between survival and GBV-C infection early in HIV disease. However, when GBV-C infection was present later in HIV disease, a significant reduction in the hazard for mortality was observed for those with co-infection. Potential explanations for this difference include a non-proportional benefit of GBV-C over time, possibly related to clearance of GBV-C infection early in HIV disease. The timing of GBV-C infection appears to account for the contradictory results of studies on the effect of GBV-C coinfection on survival of HIV-infected people.

Adult↗
PubMed2006

Effect of primer selection on estimates of GB virus C (GBV-C) prevalence and response to antiretroviral therapy for optimal testing for GBV-C viremia.

GB virus C (GBV-C; also called hepatitis G virus) is a common cause of infection associated with prolonged survival among HIV-infected individuals. The prevalences of GBV-C viremia vary widely in different studies, and there has been poor agreement among different laboratories performing GBV-C RNA detection in quality control studies. To determine the optimal method of measuring GBV-C RNA in clinical samples, samples obtained from 939 HIV-infected subjects were studied using reverse transcription (RT)-PCR methods amplifying four separate regions of the GBV-C genome. Primers amplifying the E2 coding region were 100% specific; however, their sensitivity was only 76.6%. In contrast, primers amplifying three additional conserved regions of the GBV-C genome (the 5' nontranslated region and the nonstructural protein-coding regions 3 and 5A) were more sensitive but produced higher rates of false-positive results. Using low-specificity primer sets influenced the significance of association between GBV-C viremia and response to antiretroviral therapy. Using a quantitative GBV-C RNA method, the GBV-C RNA concentration did not correlate with baseline or set point HIV RNA levels; however, a correlation between negative, low, and high GBV-C RNA levels and increasing reduction in HIV RNA following antiretroviral therapy was observed. Subjects with both GBV-C E2 antibody and viremia had significantly lower GBV-C RNA levels than did viremic subjects without E2 antibody. These studies demonstrate that accurate detection of GBV-C RNA by nested RT-PCR requires the use of primers representing multiple genome regions. Analyses based on testing with single primers do not lead to reliable conclusions about the association between GBV-C infection and clinical outcomes.

Anti-HIV Agents↗
PubMed2004

Association of hypocholesterolaemia with hepatitis C virus infection in HIV-infected people.

OBJECTIVE: To study the impact of hepatitis C virus (HCV) status on serum cholesterol levels in HIV-infected patients. METHODS: We retrospectively analysed data from the 881 participants of the Veterans Ageing Cohort 3 Site Study. Four different models were constructed using total cholesterol, low-density lipid (LDL) cholesterol, high-density lipid (HDL) cholesterol and triglycerides as dependent variables. The relevant covariates included HCV antibody status, HIV medication class, CD4 count, HIV viral load, glucose level, lipid-lowering drug use, gender, race, age, liver function test results, ethanol use, drug use, and HIV exposure category. Variables excluded from the final model included niacin use, gender, race, age, current ethanol use, and HIV exposure category. RESULTS: Of the 881 HIV-positive patients enrolled in the study, 700 (79%) were screened for HCV antibody, with 300 (42.8%) HCV antibody positive and 400 (57.2%) HCV antibody negative. A positive HCV antibody status was independently associated with lower total cholesterol levels (P=0.001) and LDL cholesterol levels (P<0.001) but not with lower HDL cholesterol or triglyceride levels. HCV-positive patients had predicted LDL levels 19 mg/dL lower than those of HCV-negative subjects. HCV infection was also associated with a decreased use of lipid-lowering medication, and protease inhibitor use was associated with increased LDL and total cholesterol levels. CONCLUSIONS: HCV infection has been associated with lower cholesterol levels in HIV-negative individuals, and the same appears to be true with HIV-infected patients. This is an interesting finding given that HCV particles bind to LDL receptors in vitro and also because HCV-lipid interactions appear to be important in the HCV replication cycle.

Antiretroviral Therapy, Highly Active↗
PubMed2001

Effect of coinfection with GB virus C on survival among patients with HIV infection.

BACKGROUND: Previous studies have suggested that people with human immunodeficiency virus (HIV) infection who are coinfected with GB virus C (GBV-C, or hepatitis G virus) have delayed progression of HIV disease. GBV-C is related to hepatitis C virus but does not appear to cause liver disease. METHODS: We examined the effect of coinfection with GBV-C on the survival of patients with HIV infection. We also evaluated cultures of peripheral-blood mononuclear cells infected with both viruses to determine whether GBV-C infection alters replication in vitro. RESULTS: Of 362 HIV-infected patients, 144 (39.8 percent) had GBV-C viremia in two tests. Forty-one of the patients with GBV-C viremia (28.5 percent) died during the follow-up period, as compared with 123 of the 218 patients who tested negative for GBV-C RNA (56.4 percent; P<0.001). The mean duration of follow-up for the entire cohort was 4.1 years. In a Cox regression analysis adjusted for HIV treatment, baseline CD4+ T-cell count, age, sex, race, and mode of transmission of HIV, the mortality rate among the 218 HIV-infected patients without GBV-C coinfection was significantly higher than that among the 144 patients with GBV-C coinfection (relative risk, 3.7; 95 percent confidence interval, 2.5 to 5.4). HIV replication, as measured by the detection of p24 antigen in culture supernatants, was reproducibly inhibited in cultures of peripheral-blood mononuclear cells by GBV-C coinfection. Coinfection did not alter the surface expression of HIV cellular receptors on peripheral-blood mononuclear cells, as determined by flow cytometry. CONCLUSIONS: GBV-C infection is common in people with HIV infection and is associated with significantly improved survival.

Adult↗
PubMed2000

Hepatitis C virus (HCV) infection and cryoglobulinemia: analysis of whole blood and plasma HCV-RNA concentrations and correlation with liver histology.

The influence of cryoprecipitate (CP) on liver histology and peripheral titers of hepatitis C virus (HCV) RNA was evaluated for 115 patients with chronic hepatitis. Fifty-four patients had measurable CP levels whereas 61 did not. Assessment of liver biopsies for grade of fibrosis revealed that patients with CP had increased fibrosis (P <.001) and incidence of cirrhosis (P =.001) compared with those without CP. In contrast, there was not a significant difference in the inflammatory activity score between the 2 groups. HCV RNA in whole blood (WB) and plasma (Pl) was evaluated in patients with or without CP by end-point-limiting dilution titer. Among patients with CP, WB titers were significantly higher than Pl titers (P <.001); however, there was no difference in WB or Pl titers in patients without CP (P =.068). Histological activity and fibrosis scores of patients from either group were compared with peripheral viral titers of WB and Pl, percentage of CP, rheumatoid factor (RF) titer, and serum alanine transaminase (ALT). There were significant correlations between the amount of fibrosis and the percentage of CP and rheumatoid factor titer, yet neither of the latter parameters was correlated with inflammatory activity. These data suggest that patients with CP and chronic hepatitis owing to HCV are more likely to have progressive disease than patients without CP. Furthermore, the presence of CP in patients infected with HCV appears to influence the amount of virus detected in patient Pl, suggesting that WB assays may be more reliable for HCV-RNA quantitation in patients with CP.

Adult↗
PubMed2000

Elevated phenotypic switching and drug resistance of Candida albicans from human immunodeficiency virus-positive individuals prior to first thrush episode.

Strains of Candida albicans obtained from human immunodeficiency virus (HIV)-positive individuals prior to their first episode of oral thrush were already in a high-frequency mode of switching and were far more resistant to a number of antifungal drugs than commensal isolates from healthy individuals. Switching in these isolates also had profound effects both on susceptibility to antifungal drugs and on the levels of secreted proteinase activity. These results suggest that commensal strains colonizing HIV-positive individuals either undergo phenotypic alterations or are replaced prior to the first episode of oral thrush. They also support the suggestion that high-frequency phenotypic switching functions as a higher-order virulence trait, spontaneously generating in colonizing populations variants with alterations in a variety of specific virulence traits.

AIDS-Related Opportunistic Infections↗
PubMed2000

Fluorescence-based quantitative methods for detecting human immunodeficiency virus type 1-induced syncytia.

Cell fusion induced by human immunodeficiency virus type 1 (HIV-1) is usually assessed by counting multinucleated giant cells (syncytia) visualized by light microscopy. Currently used methods do not allow quantification of syncytia, nor do they estimate the number of cells involved in cell fusion. We describe two fluorescence-based methods for the detection and quantification of HIV-1-induced in vitro syncytium formation. The lymphoblastoid cell lines MT-2 and SupT1 were infected with syncytium-inducing (SI) HIV-1 isolates. Syncytia were detected by DNA staining with propidium iodide using flow cytometry to determine cell size or by two-color cytoplasmic staining of infected cell populations by using fluorescence microscopy. Both methods were able to detect and quantify HIV-induced syncytia. The methods could distinguish between SI and non-SI HIV isolates and could be used with at least two separate types of CD4(+) T-cell lines. Small syncytia can be readily identified by the two-color cytoplasmic staining method. Both methods were also shown to be useful for evaluating antiretroviral compounds, as demonstrated by the accurate assessment of HIV inhibition by azidothymidine (zidovudine), dideoxycytidine (zalcytibine), and hydroxyurea. These fluorescence-based assays allow a rapid and practical method for measuring HIV replication and anti-HIV activity of potential inhibitory compounds.

DNA, Viral↗
PubMed2000

Full-length GB virus C (Hepatitis G virus) RNA transcripts are infectious in primary CD4-positive T cells.

GB virus C (GBV-C or hepatitis G virus) is a recently described flavivirus which frequently leads to chronic viremia in humans. Although GBV-C is associated with acute posttransfusion hepatitis, it is not clear if the virus is pathogenic for humans. We constructed a full-length cDNA from the plasma of a person with chronic GBV-C viremia. Peripheral blood mononuclear cells (PBMCs) transfected with full-length RNA transcripts from this GBV-C clone resulted in viral replication. This was demonstrated by serial passage of virus from cell culture supernatants, detection of increasing concentrations of positive- and negative-sense GBV-C RNA over time, and the detection of the GBV-C E2 antigen by confocal microscopy. In addition, two types of GBV-C particles were identified in cell lysates; these particles had buoyant densities of 1.06 and 1.12 to 1.17 g/ml in sucrose gradients. PBMCs sorted for expression of CD4 contained 100-fold-more GBV-C RNA than CD4-negative cells. Taken together, these data demonstrate that RNA transcripts from GBV-C full-length cDNA are infectious in primary CD4-positive T cells. In contrast, RNA transcripts from an infectious hepatitis C virus clone did not replicate in the same cell culture system. Infectious RNA transcripts from GBV-C cDNA should prove useful for studying viral replication and may allow identification of differences between GBV-C and hepatitis C virus cultivation in vitro.

CD4-Positive T-Lymphocytes↗
PubMed2000

Characterization of hepatitis C virus (HCV) and HCV E2 interactions with CD81 and the low-density lipoprotein receptor.

Hepatitis C virus (HCV) or HCV-low-density lipoprotein (LDL) complexes interact with the LDL receptor (LDLr) and the HCV envelope glycoprotein E2 interacts with CD81 in vitro. However, E2 interactions with LDLr and HCV interactions with CD81 have not been clearly described. Using sucrose gradient-purified low-density particles (1.03 to 1.07 g/cm(3)), intermediate-density particles (1. 12 to 1.18 g/cm(3)), recombinant E2 protein, or control proteins, we assessed binding to MOLT-4 cells, foreskin fibroblasts, or LDLr-deficient foreskin fibroblasts at 4 degrees C by flow cytometry and confocal microscopy. Viral entry was determined by measuring the coentry of alpha-sarcin, a protein synthesis inhibitor. We found that low-density HCV particles, but not intermediate-density HCV or controls bound to MOLT-4 cells and fibroblasts expressing the LDLr. Binding correlated with the extent of cellular LDLr expression and was inhibited by LDL but not by soluble CD81. In contrast, E2 binding was independent of LDLr expression and was inhibited by human soluble CD81 but not mouse soluble CD81 or LDL. Based on confocal microscopy, we found that low-density HCV particles and LDL colocalized on the cell surface. The addition of low-density HCV but not intermediate-density HCV particles to MOLT-4 cells allowed coentry of alpha-sarcin, indicating viral entry. The amount of viral entry also correlated with LDLr expression and was independent of the CD81 expression. Using a solid-phase immunoassay, recombinant E2 protein did not interact with LDL. Our data indicate that E2 binds CD81; however, virus particles utilize LDLr for binding and entry. The specific mechanism by which HCV particles interact with LDL or the LDLr remains unclear.

Animals↗
PubMed1999

Hepatitis A virus-specific humoral and cellular immune responses following immunization with a formalin-inactivated hepatitis A vaccine.

To evaluate proliferative T cell responses elicited by a formalin-inactivated HAV vaccine, we immunized 10 subjects with an inactivated HAV vaccine, and measured HAV antibody titers and HAV-specific T cell proliferation. gamma-Interferon production by PBMC's was evaluated in selected subjects. By week 30, seroconversion (geometric mean titer=2299 mIU/ml), and HAV-specific proliferation was detected in all subjects. HAV also induced gamma-interferon in the three subjects studied. These data indicate that the inactivated HAV vaccine induces proliferative T cell responses in addition to HAV antibody. This may be important for protection against hepatitis A, and suggests that recall memory for HAV antigen is elicited by the vaccine.

Adult↗
PubMed1999

Visualization and characterization of GB virus-C particles: evidence for a nucleocapsid.

GB virus type C (GBV-C) is a member of the hepacivirus genus within the Flaviviradae. Persistent GBV-C infection is common in humans, yet it remains unclear if GBV-C causes any disease. Although GBV-C infection has been associated with acute non-A to non-E post-transfusion hepatitis, it does not appear to cause chronic hepatitis. GBV-C is closely related to hepatitis C virus (HCV), but indirect evidence suggests that it does not encode a core protein at the amino terminus of the open reading frame (ORF). This has led to speculation that GBV-C does not have a nucleocapsid. We evaluated the buoyant density of GBV-C, and found very low density particles consistent with virions, and intermediate density particles consistent with nucleocapsids in GBV-C-infected people. In addition, electron microscopy demonstrated an apparent nucleocapsid within an enveloped particle. Although these biophysical data strongly suggest that GBV-C utilizes a nucleocapsid, they do not indicate the origin of the protein content of this particle. To assess this, we evaluated patient plasma for reactivity with a synthetic oligopeptide representing a conserved region near the amino terminus of the predicted ORF. Specific antibody was detected in some individuals, similar to data of Feucht et al. who identified antibody against a recombinant core protein in GBV-C-infected people. These data indicate that GBV-C particles contain nucleocapsids. At least in some patients, the region upstream of the GBV-C E1 protein coding region appears to be expressed, and this region may represent the structural protein of the nucleocapsid.

Amino Acid Sequence↗
PubMed1999

Prospective comparison of whole-blood- and plasma-based hepatitis C virus RNA detection systems: improved detection using whole blood as the source of viral RNA.

We previously demonstrated that whole blood contains significantly more hepatitis C virus (HCV) RNA than plasma. To validate the whole-blood-based HCV RNA detection method, a prospective comparison of HCV RNA detection in whole blood and plasma from 50 patients with chronic liver disease was undertaken. Whole-blood and plasma aliquots were independently tested for HCV RNA by reverse transcriptase (RT) PCR assay, and plasma was tested by the Roche Amplicor assay. HCV RNA was detected in 35 of 50 (70%) whole-blood samples by RT-PCR but in only 26 of 50 (52%) plasma samples tested by the Amplicor assay (P < 0.01). HCV RNA was detected in 85% of HCV antibody-positive patients by the whole-blood method compared with 74% of plasma samples by the Amplicor method. The five HCV antibody-positive subjects who were negative by whole-blood-based RT-PCR assay were all receiving interferon therapy and had normal transaminases at the time of testing. HCV RNA was detected in 38% of HCV antibody-negative subjects by the whole-blood-based RT-PCR assay compared with 6.25% of these patients by the Amplicor assay (P < 0. 05). There were nine samples in which HCV RNA was detected in whole blood but the Amplicor test was negative. Eight of the nine RNAs prepared from these whole-blood samples tested positive in the Amplicor assay, thus confirming the specificity of our results. This study demonstrates that whole-blood-based HCV RNA detection is more sensitive than currently available commercial tests and that whole-blood RNA is suitable for use in commercial assays.

Cloning, Molecular↗
PubMed1999

Comparison of a neural network approach with five traditional methods for predicting creatinine clearance in patients with human immunodeficiency virus infection.

STUDY OBJECTIVE: To compare the results of an artificial neural network approach with those of five published creatinine clearance (Cl(cr)) prediction equations and with the measured (true) Cl(cr) in patients infected with the human immunodeficiency virus (HIV). DESIGN: Six-month prospective study. SETTINGS: Two university medical centers. PATIENTS: Sixty-five HIV-infected patients: 18 relatively healthy outpatients and 47 inpatients. INTERVENTIONS: All subjects had urine collected for 24 hours to determine Cl(cr). MEASUREMENTS AND MAIN RESULTS: The 16 input variables were age, ideal body weight, actual body weight, body surface area, height, and the following blood chemistries: sodium, potassium, aspartate aminotransferase, alanine aminotransferase, red blood cell count, platelet count, white blood cell count, glucose, serum creatinine, blood urea nitrogen, and albumin. The only output variable was Cl(cr). A training set of 55 subjects was used to develop the relationship between input variables and the output variable. The trained neural network was then used to predict Cl(cr) of a validation set of 10 subjects. Mean differences between predicted Cl(cr) and actual Cl(cr) (bias) were 4.1, 28.7, 29.4, 26.0, 31.8, and 55.8 ml/min/1.73 m2 for the artificial neural network, Cockcroft and Gault, Jelliffe 1, Jelliffe 2, Mawer et al, and Hull et al methods, respectively. CONCLUSION: The accuracy of predicting Cl(cr) in subjects with HIV infection by the artificial neural network is superior to that of the five equations that are currently used in clinical settings.

Adult↗
PubMed1998

Effect of interferon therapy on hepatitis C virus RNA in whole blood, plasma, and peripheral blood mononuclear cells.

Fifty-two patients with chronic hepatitis C virus (HCV) infection were treated with standard doses of interferon alfa-2b. During treatment, HCV RNA detection was studied in samples of whole blood (WB), plasma (Pl), and peripheral blood mononuclear cells (PBMCs). Individuals were classified as sustained responders (SRs), complete responders with relapse (CRs), partial responders (PRs), or nonresponders (NRs) according to normalization of serum alanine transaminase (ALT) during treatment and follow-up. Before treatment, 100% of WB samples and more than 95% of Pl and PBMC samples were positive for HCV RNA. During treatment, there was progressive clearance of HCV RNA from Pl and PBMCs in SRs and CRs, but CRs had significantly more positive WB samples during and following treatment (P <.0001). At 6 months, only 10% of CR patients were positive by Pl assay, but 50% were positive by WB assay (P <.01). In the PR group, all WB samples remained positive throughout treatment, although 25% to 40% of PBMC and Pl samples became negative for HCV RNA during the first 2 months of therapy (WB > Pl or PBMC; P < .001). However, at later times during treatment most Pl and PBMC samples in the PR group were positive. Samples from the NR group showed no clearance of HCV RNA from WB, Pl, or PBMC fractions. These data document the increased sensitivity of WB assays for detecting HCV RNA in the peripheral blood of patients during interferon therapy. Furthermore, our findings suggest that WB analysis of HCV RNA may be a useful parameter to monitor in determining the end point of interferon therapy.

Adult↗