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Biomedical subjects

C Crumpacker

Publications and source records attributed to C Crumpacker.

At least 19 recordsLinked to original sources
PubMed2005

Silencing p21(Waf1/Cip1/Sdi1) expression increases gene transduction efficiency in primitive human hematopoietic cells.

Adult hematopoietic and other tissue stem cells have highly constrained cell cycling that limits their susceptibility to standard gene therapy vectors, which depend upon chromosomal integration. Using cytokine cocktails to increase transduction efficiency often compromises subsequent stem cell function in vivo. We previously showed that p21(Waf1/Cip1/Sdi1) (p21) mediates stem cell quiescence in vivo and decreasing its expression ex vivo leads to an expansion of stem cell pool in vivo. Here, we report that application of p21 specific siRNA increased the gene transduction efficiency in hematopoietic stem cells while preserving cell multipotentiality. Both types of siRNA, synthesized siRNA and transcribed shRNA, reduced p21 expression in target cells by 85-98%. The effect of RNAi in these cells was transient and the level of p21 mRNA returned to base line 14-28 days after siRNA treatment. This brief interval of reduction, however, was sufficient to increase transduction efficiency to two- to four-fold in cell cultures, and followed by a seven- to eight-fold increase in mice. The RNAi treated, lentivector-transduced CD34+ cells retained multipotentiality as assessed in vitro by colony formation assay and in vivo by NOD/SCID mouse transplantation assay. Reduction of p21 resulted in an increased chromosomal integration of lentivector into target cellular DNA. Taken together, both synthesized and transcribed siRNA knocked down p21 expression in human CD34+ hematopoietic stem/progenitor cells. Silencing p21 expression increased gene transduction efficiency and vector integration while retaining stem cell multipotentiality. Thus, RNAi targeting of p21 is a useful strategy to increase stem cell gene transfer efficiency. Decreasing p21 expression transiently while increasing gene-transfer vector integration may ultimately facilitate clinical applications of gene therapy.

Adult↗
PubMed2001

Comparison of quantitative and qualitative PCR assays for cytomegalovirus DNA in plasma.

We analyzed the performance characteristics of the qualitative AMPLICOR CMV Test (Roche Molecular Systems, Pleasanton, Calif.) and quantitative COBAS AMPLICOR CMV MONITOR Test (Roche Molecular Systems) assays and compared the performance of the AMPLICOR quantitative assay with an in-house-developed cytomegalovirus (CMV) DNA PCR assay. The quantitative AMPLICOR assay was found to be more sensitive than the qualitative AMPLICOR assay. The quantitative AMPLICOR assay has a lower limit of sensitivity of 400 CMV DNA copies/ml of plasma and is linear to 50,000 CMV DNA copies/ml of plasma. Compared to the in-house PCR assay, the AMPLICOR quantitative assay gave lower viral load values at all concentrations tested, but the difference between the two assays was not consistent across the entire dynamic range of the AMPLICOR quantitative assay. At the lower end of the assay, the viral load values obtained with the in-house PCR assay were three- to fivefold (0.5 to 0.7 log units) higher than those measured with the AMPLICOR assay. At higher input concentrations, the differences between the two assays approached 10-fold. This direct comparison of the in-house assay and the quantitative AMPLICOR assay provides the ability to compare previously published in-house data with an assay widely available for future research and clinical monitoring of patients with CMV infections.

Cytomegalovirus↗
PubMed2000

Characterization of an acyclovir-resistant herpes simplex virus type 2 strain isolated from a premature neonate.

Acyclovir resistance is not a recognized problem among neonates with perinatal herpes simplex virus (HSV) infection. A premature newborn with neurocutaneous HSV infection was treated for 21 days with acyclovir. Disseminated disease recurred 8 days later. A recurrent isolate was resistant to acyclovir and lacked thymidine kinase activity on the basis of a frameshift mutation in the thymidine kinase (tk) gene. Compared with the sensitive isolate obtained during primary infection, replication of the resistant isolate was reduced on primary and permanent cells and even further impaired on cells deleted for cellular tk. The resistant isolate lacked virulence in a murine model of genital infection. Acyclovir-resistant HSV-2 mutants can develop rapidly in neonatal infection and cause clinically significant disease, despite decreased replication in vitro and attenuated virulence in an animal model.

Acyclovir↗
PubMed2000

A standardized plaque reduction assay for determination of drug susceptibilities of cytomegalovirus clinical isolates.

Twelve laboratories collaborated in formulating and testing a standardized plaque reduction assay for cytomegalovirus (CMV) cell-associated clinical isolates. Four characterized and plaque-purified CMV strains, as well as six coded clinical isolates obtained after antiviral therapy, were distributed and tested. Good agreement was obtained for four of the clinical isolates, but a broad distribution of results was obtained for two isolates. Analysis of these results indicates the problems associated with clinical isolates, including the large genetic variability and the highly cell-associated phenotype. This collaborative effort, by addressing these problems, represents a significant step toward the development of a standardized assay.

Antiviral Agents↗
PubMed1999

Phase I studies of hypericin, the active compound in St. John's Wort, as an antiretroviral agent in HIV-infected adults. AIDS Clinical Trials Group Protocols 150 and 258.

BACKGROUND: Hypericin, the active compound in St. John's Wort, has antiretroviral activity in vitro. Many HIV-infected persons use St. John's wort. OBJECTIVE: To evaluate the safety and antiretroviral activity of hypericin in HIV-infected patients. DESIGN: Phase I study. SETTING: Four clinical research units. PATIENTS: 30 HIV-infected patients with CD4 counts less than 350 cells/mm3. INTERVENTION: Intravenous hypericin, 0.25 or 0.5 mg/kg of body weight twice weekly or 0.25 mg/kg three times weekly, or oral hypericin, 0.5 mg/kg daily. MEASUREMENTS: Safety was assessed at weekly visits. Antiretroviral activity was assessed by changes in HIV p24 antigen level, HIV titer, HIV RNA copies, and CD4 cell counts. RESULTS: Of the 30 patients who were enrolled, 16 discontinued treatment early because of toxic effects. Severe cutaneous phototoxicity was observed in 11 of 23 (48% [95% CI, 27% to 69%]) evaluable patients, and dose escalation could not be completed. Virologic markers and CD4 cell count did not significantly change. CONCLUSIONS: Hypericin caused significant phototoxicity and had no antiretroviral activity in the limited number of patients studied.

Administration, Oral↗
PubMed1998

Flow cytometric determination of ganciclovir susceptibilities of human cytomegalovirus clinical isolates.

A flow cytometric assay has been developed for the measurement of susceptibilities to ganciclovir of laboratory strains and clinical isolates of human cytomegalovirus (HCMV). The assay uses fluorochrome-labeled monoclonal antibodies to HCMV immediate-early and late antigens to identify HCMV-infected cells and flow cytometry to detect and quantitate the number of antigen-positive cells. By this assay, the 50 and 90% inhibitory concentrations (IC50 and IC90, respectively) of ganciclovir for the AD169 strain of HCMV were 1.7 and 9.2 microM, respectively, and the IC50 for the ganciclovir-resistant D6/3/1 derivative of the AD169 strain was greater than 12 microM. The ganciclovir susceptibilities of 17 HCMV clinical isolates were also determined by flow cytometric analysis of the effect of ganciclovir on late-antigen synthesis in HCMV-infected cells. The average IC50 of ganciclovir for drug-sensitive HCMV clinical isolates was 3.79 microM (+/-2.60). The plaque-reduction assay for these clinical isolates yielded an average IC50 of 2.80 microM (+/-1.46). Comparison of the results of the flow cytometry assays with those obtained from the plaque-reduction assays demonstrated acceptable bias and precision. Flow cytometric and plaque-reduction analysis of cells infected with ganciclovir-resistant clinical isolates failed to show a reduction in the percentage of late-antigen-positive cells or PFU, even at 96 microM ganciclovir. The flow cytometric assay for determining ganciclovir susceptibility of HCMV is quantitative, and objective, and potentially automatable, and its results are reproducible among laboratories.

Antigens, Viral↗
PubMed1996

The pharmacological profile of famciclovir.

Famciclovir is the well-absorbed oral form of penciclovir, a potent and selective antiviral agent, with activity against members of the herpesvirus family, including varicella-zoster virus (VZV), and herpes simplex virus-1 (HSV-1) and HSV-2. Famciclovir is rapidly absorbed and converted to penciclovir. Penciclovir has excellent bioavailability (77%) after oral administration of 500 mg of famciclovir. Similar to acyclovir, famciclovir is converted by phosphorylation to its active metabolite, penciclovir-triphosphate. Penciclovir-triphosphate has a prolonged in vitro intracellular half-life of 10 to 20 hours in HSV-1-and HSV-2-infected cells, respectively, and 9 to 14 hours in VZV-infected cells. In contrast, the in vitro intracellular half-life of acyclovir is substantially shorter at 0.7 and 1 hours in HSV-1- and HSV-2-infected cells, respectively, and 0.8 hours in VZV-infected cells. Famciclovir is eliminated primarily via the kidneys. Dosage adjustment is not required for famciclovir in elderly patients with normal or mildly impaired renal function, and the extent of penciclovir availability is not affected by food. The excellent bioavailability ensures that adequate drug reaches virus-infected cells, and the prolonged intracellular half-life of the active form of famciclovir results in persistent antiviral activity.

2-Aminopurine↗
PubMed1995

Oral ganciclovir as maintenance treatment for cytomegalovirus retinitis in patients with AIDS. Syntex Cooperative Oral Ganciclovir Study Group.

BACKGROUND: Cytomegalovirus retinitis, a sight-threatening infection associated with the acquired immunodeficiency syndrome (AIDS), currently requires lifelong intravenous treatment. An effective oral treatment would be an important advance. METHODS: We compared oral with intravenous ganciclovir in an open-label, randomized study in patients with AIDS and newly diagnosed, stable cytomegalovirus retinitis (the disease was stabilized by three weeks of treatment with intravenous ganciclovir). Sixty subjects were randomly assigned to maintenance therapy with intravenous ganciclovir at a dose of 5 mg per kilogram of body weight daily, and 63 to maintenance therapy with oral ganciclovir at a dose of 3000 mg daily. The subjects were followed for up to 20 weeks, with photography of the fundi conducted every other week. The photographs were evaluated at the completion of the study by an experienced grader who was unaware of the subjects' treatment assignments. RESULTS: Efficacy could be evaluated in 117 subjects; photographs were ungradable for 2 of the 117. On the basis of the masked assessment of photographs from 115 subjects, the mean time to the progression of retinitis was 62 days in those given intravenous ganciclovir and 57 days in those given oral ganciclovir (P = 0.63; relative risk [oral vs. intravenous], 1.08; 95 percent confidence interval for the difference in means, -22 to +12 days). On the basis of funduscopy by ophthalmologists who were aware of the subjects' treatment assignments, the mean time to progression was 96 days in subjects given intravenous ganciclovir and 68 days in subjects given oral ganciclovir (P = 0.03; relative risk [oral vs. intravenous], 1.68; 95 percent confidence interval for the difference in means, -45 to -11 days). Survival, changes in visual acuity, the incidence of viral shedding, and the incidence of adverse gastrointestinal events were similar in the two groups. Neutropenia, anemia, intravenous-catheter-related adverse events, and sepsis were more common in the group given intravenous ganciclovir. CONCLUSIONS: Oral ganciclovir is safe and effective as maintenance therapy for cytomegalovirus retinitis and is more convenient for patients to take than intravenous ganciclovir.

AIDS-Related Opportunistic Infections↗
PubMed1994

Combination of ganciclovir and granulocyte-macrophage colony-stimulating factor in the treatment of cytomegalovirus retinitis in AIDS patients. The ACTG 073 Team.

The efficacy and safety of a combination of ganciclovir plus GM-CSF was evaluated in AIDS patients with cytomegalovirus retinitis. In phase A, patients were randomized to receive ganciclovir, 5 mg/kg every 12 h for 14 days followed by 5 mg/kg daily, with (n = 24) or without (n = 29) GM-CSF (1-8 micrograms/kg daily subcutaneously) to maintain absolute neutrophil counts between 2500 and 5000 cells/microliters. In phase B, after 16 weeks zidovudine was added to the regimen of 16 patients receiving ganciclovir plus GM-CSF and 20 receiving ganciclovir alone. At this stage, GM-CSF was added to the treatment protocol of any patient receiving ganciclovir plus zidovudine who became neutropenic. In phase A, patients in the ganciclovir plus GM-CSF group had significantly higher neutrophil counts than ganciclovir-alone patients (p = 0.0001). Overall, 12.5% of patients treated with GM-CSF developed neutropenia (absolute neutrophil counts < 500/microliters phase A and < 750/microliters phase B) compared with 45% of patients treated without GM-CSF. GM-CSF patients missed 10 of a possible 4705 scheduled doses of ganciclovir compared with 34 missed doses of a possible 6584 in the ganciclovir-alone group (p = 0.011). There was a trend, although not statistically significant, for patients in the GM-CSF group to experience delayed progression of their retinitis.(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS-Related Opportunistic Infections↗
PubMed1993

Ganciclovir treatment of cytomegalovirus colitis in AIDS: a randomized, double-blind, placebo-controlled multicenter study.

The efficacy and safety of ganciclovir therapy for cytomegalovirus (CMV) colitis in patients with AIDS was examined in a double-blind, placebo-controlled study. Sixty-two patients at four university medical centers were enrolled. All had biopsy-proven CMV colitis with diarrhea, fever, and weight loss. Other pathogens were excluded. Ganciclovir (5 mg/kg) or placebo was administered every 12 h for 14 days. A significant reduction in CMV-positive colonic and urine cultures was seen with ganciclovir (P = .034 and P < .001, respectively) compared with placebo. Colonoscopy scores were improved significantly more with ganciclovir than with placebo (P = .042). New extracolonic CMV disease developed in 7 (23%) of 30 placebo patients and in 3 (9%) of 32 ganciclovir patients in only 14 days (P = .026). Ganciclovir-treated patients maintained body weight, while placebo patients had a mean loss of 1.5 kg. Overall, ganciclovir appears of some benefit in treating CMV colitis in patients with AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1992

Inhibition of HIV-1 RNA production by the diphtheria toxin-related IL-2 fusion proteins DAB486IL-2 and DAB389IL-2.

Productive infection of cells by human immunodeficiency virus type 1 (HIV-1) is associated with the activation state of the cell and its obligatory expression of the interleukin-2 receptor (IL-2R), the latter providing a new target for antiviral therapy. A quantitative RNA-RNA hybridization assay is employed to detect production of HIV-1 RNA and to show that two IL-2 diphtheria toxin-related fusion proteins (DAB486IL-2 and its more potent, truncated form DAB389IL-2) inhibit HIV-1 RNA production in infected cells. A mutant form of DAB486IL-2 containing a single point mutation that inactivates the adenosine diphosphate ribosyltransferase activity of the toxin does not inhibit HIV RNA production, even though the molecule binds to the IL-2R. The active fusion proteins inhibit viral RNA replication in cells infected with HIV-1 clinical isolates as well as with a ZDV-resistant strain of HIV-1. These results indicate that IL-2 receptor-targeted fusion proteins can be utilized to inhibit HIV-1 replication effectively in infected human lymphocytes.

Antiviral Agents↗
PubMed1991

A controlled trial comparing foscarnet with vidarabine for acyclovir-resistant mucocutaneous herpes simplex in the acquired immunodeficiency syndrome. The AIDS Clinical Trials Group.

BACKGROUND AND METHODS: Most strains of herpes simplex virus that are resistant to acyclovir are susceptible in vitro to both foscarnet and vidarabine. We conducted a randomized trial to compare foscarnet with vidarabine in 14 patients with the acquired immunodeficiency syndrome (AIDS) and mucocutaneous herpetic lesions that had been unresponsive to intravenous therapy with acyclovir for a minimum of 10 days. The patients were randomly assigned to receive either foscarnet (40 mg per kilogram of body weight intravenously every 8 hours) or vidarabine (15 mg per kilogram per day intravenously) for 10 to 42 days. In the isolates of herpes simplex virus we documented in vitro resistance to acyclovir and susceptibility to foscarnet and vidarabine. RESULTS: The lesions in all eight patients assigned to foscarnet healed completely after 10 to 24 days of therapy. In contrast, vidarabine was discontinued because of failure in all six patients assigned to receive it. The time to complete healing (P = 0.01), time to 50 percent reductions in the size of the lesions (P = 0.01) and the pain score (P = 0.004), and time to the end of viral shedding (P = 0.006) were all significantly shorter in the patients assigned to foscarnet. Three patients had new neurologic abnormalities while receiving vidarabine. No patient discontinued foscarnet because of toxicity. Although initial recurrences of herpes simplex infection after the index lesion had healed tended to be susceptible to acyclovir, acyclovir-resistant infection eventually recurred in every healed patient, a median of 42.5 days (range, 14 to 191) after foscarnet was discontinued. CONCLUSIONS: For the treatment of acyclovir-resistant herpes simplex infection in patients with AIDS, foscarnet has superior efficacy and less frequent serious toxicity than vidarabine. Once the treatment is stopped, however; there is a high frequency of relapse.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Prolonged continuous acyclovir treatment of normal adults with frequently recurring genital herpes simplex virus infection. The Acyclovir Study Group.

In this 3-year study of suppressive acyclovir for recurrent genital herpes, patients with more than six recurrences per year were randomized initially to 400 mg of acyclovir or placebo orally two times per day, with recurrences treated with 200 mg of acyclovir five times per day for 5 days. In the second year of the study, all patients received acyclovir as a daily suppressive or intermittent acute therapy; in the third year, all received daily acyclovir. Among 525 patients completing 3 study years, 289 received 3 years of suppressive therapy and 236 received 1 year of acute therapy followed by 2 years of suppressive therapy. Of those who completed the third year, 61% were recurrence free that year; 25% of the suppressive therapy-only group were recurrence free for all 3 years. The annual recurrence rate dropped from more than 12 recurrences per year at baseline to 1.0 (suppressive therapy) and 1.4 (acute and suppressive therapy) recurrences during the third year. No significant toxic effects were detected. Daily suppressive acyclovir therapy was effective and well tolerated.

Acyclovir↗
PubMed1991

Inhibition of immune functions by antiviral drugs.

Immune functions were evaluated in vitro for PBMC isolated from healthy donors and cultured with the antiviral agents, 3'-azido-3'-deoxythymidine (AZT), ribavirin, ganciclovir, 2'3'-dideoxyinosine (ddI), or acyclovir. To identify methods for assessing the effects of antiviral drugs on immune cells, the PBMC response to mitogens, Con A, or phytohemagglutinin was evaluated from measurements of [3H]thymidine and [14C]-leucine incorporation, cell growth, cellular RNA, DNA, and protein levels, and the PBMC proliferative cycle (i.e., progression from G0----G1----S----G2 + M). At clinically relevant concentrations, AZT, ribavirin, or ganciclovir diminished PBMC responsiveness to mitogen. The numbers of proliferating cells in G1, S, and G2 + M phases of the cell cycle, DNA content, and [3H]thymidine uptake were decreased in cultures treated with AZT, ribavirin, or ganciclovir. AZT or ribavirin but not ganciclovir reduced RNA and protein in the cultures and inhibited cell growth. Whereas AZT, ribavirin, or ganciclovir were antiproliferative, ddI or acyclovir had little, if any, effect on PBMC mitogenesis. The inhibitory effects of antivirals on immune cells may contribute to the immune deterioration observed in patients following prolonged use of the drugs.

Acyclovir↗
PubMed1989

Recombinant human gamma interferon enhances in vitro activation of lymphocytes isolated from patients with acquired immunodeficiency syndrome.

Decreased responses to antigens and lectins are a characteristic feature of peripheral blood lymphocytes isolated from patients with the acquired immunodeficiency syndrome (AIDS). The in vitro addition of recombinant gamma interferon (IFN-gamma) to cultures of peripheral blood lymphocytes obtained from patients with AIDS resulted in an augmented proliferative response [( 3H]thymidine uptake) to phytohemagglutinin (PHA) and an enrichment in CD4+ and CD8+ T lymphocytes. In AIDS cultures stimulated with PHA, IFN-gamma increased the release of T-cell growth factors and enhanced the expression of interleukin-2 receptors on activated lymphocytes. Responsiveness to PHA was augmented, albeit to a lesser extent, by IFN-gamma in cultures derived from normal donors. Proliferation to microbial antigens including herpes simplex virus, cytomegalo virus, and Candida albicans was increased by IFN-gamma in cultures established from a group of AIDS patients with Kaposi's sarcoma who had no history of opportunistic infection.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Ribavirin antagonizes the effect of azidothymidine on HIV replication.

Azidothymidine and ribavirin both inhibit replication of human immunodeficiency virus in vitro and show promise of clinical utility in patients infected with this virus. In this study, the possible interactions of these drugs were examined in vitro, and a reproducible antagonism between azidothymidine and ribavirin was found to occur under a variety of experimental conditions. The mechanism responsible for this antagonism appeared to be inhibition of azidothymidine phosphorylation by ribavirin. Because similar effects may occur in vivo, clinical trials of these two drugs in combination must be performed only under carefully controlled conditions.

Cell Line↗