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P Bedford

Publications and source records attributed to P Bedford.

At least 19 recordsLinked to original sources
PubMed2005

Comparison of the antibody in lymphocyte supernatant (ALS) and ELISPOT assays for detection of mucosal immune responses to antigens of enterotoxigenic Escherichia coli in challenged and vaccinated volunteers.

In the present study we compared the ELISPOT and antibody in lymphocyte supernatants (ALS) assays as surrogate measures of mucosal immunity. In separate studies, 20 inpatient volunteers received oral doses of 6 x 10(8) or 4 x 10(9)cfu of ETEC strain E24377A (LT+, ST+, CS1+, CS3+) and 20 subjects received 1 (n = 9) or 2 (n = 11) oral doses of the attenuated ETEC vaccine, PTL-003 expressing CFA/II (CS1+ and CS3+) (2 x 10(9)cfu/dose). Peripheral blood mononuclear cells (PBMCs) from all subjects were assayed for anti-colonization factor or toxin-specific IgA antibody responses using the ALS and ELISPOT procedures. ALS responses were measured using a standard ELISA, as well as by time-resolved fluorescence (TRF). Following challenge with E24377A, significant anti-CS3, CS1 and LT ALS responses were detected in the lymphocyte supernatants of 75-95% of the subjects. A similar proportion (75%) of subjects mounted an ALS response to CFA/II antigen after vaccination with the PTL-003 vaccine. Inter-assay comparisons between ALS and ELISPOT methods also revealed a high degree of correlation in both immunization groups. ALS sensitivity versus the ELISPOT assay for LT, CS3 and CS1-specific responses following challenge were 95%, 94% and 78%, respectively and 83% for the ALS response to CFA/II antigen after vaccination with PTL-003. Correlation coefficients for the LT and CS3 antigens were 0.94 (p<0.001) and 0.82 (p<0.001), respectively after challenge and 0.78 (p<0.001) after vaccination. The association between ALS and ELISPOT for the CS1 antigen was however, significant only when ALS supernatants were tested by TRF (r = 0.91, p<0.001). These results demonstrate the value and flexibility of the ALS assay as an alternative to ELISPOT for the measurement of mucosal immune responses to ETEC antigens, particularly when the complexities of ELISPOT may make it impractical to perform.

Adult↗
PubMed2000

Phase 2 clinical trial of attenuated Salmonella enterica serovar typhi oral live vector vaccine CVD 908-htrA in U.S. volunteers.

Salmonella enterica serovar Typhi strain CVD 908-htrA is a live attenuated strain which may be useful as an improved oral typhoid vaccine and as a vector for cloned genes of other pathogens. We conducted a phase 2 trial in which 80 healthy adults received one of two dosage levels of CVD 908-htrA in a double-blind, placebo-controlled, crossover study. There were no differences in the rates of side effects among volunteers who received high-dose vaccine (4.5 x 10(8) CFU), lower-dose vaccine (5 x 10(7) CFU), or placebo in the 21 days after vaccination, although recipients of high-dose vaccine (8%) had more frequent diarrhea than placebo recipients (0%) in the first 7 days. Seventy-seven percent and 46% of recipients of high- and lower-dose vaccines, respectively, briefly excreted vaccine organisms in their stools. All blood cultures were negative. Antibody-secreting cells producing antilipopolysaccharide (LPS) immunoglobulin A (IgA) were detected in 100 and 92% of recipients of high- and lower-dose vaccines, respectively. Almost half the volunteers developed serum anti-LPS IgG. Lymphocyte proliferation and gamma interferon production against serovar Typhi antigens occurred in a significant proportion of vaccinees. This phase 2 study supports the further development of CVD 908-htrA as a single-dose vaccine against typhoid fever and as a possible live vector for oral delivery of other vaccine antigens.

Administration, Oral↗
PubMed1999

MHC class II molecules transferred between allogeneic dendritic cells stimulate primary mixed leukocyte reactions.

Presentation of antigen to T cells is generally restricted by MHC type but the mixed leukocyte reaction (MLR) was thought to involve direct stimulation by dendritic cells (DC) of allogeneic T cells. However, here we showed that DC bearing allogeneic MHC class II acted synergistically with responder-type DC. Removal of residual DC from 'purified' responder T cell populations was achieved using treatment with DC-specific antibody and complement. These DC-depleted cells showed a significantly reduced response to allogeneic DC which was restored by addition of DC syngeneic with responder T cells. The studies support the concept that a major component of the MLR is the secondary presentation of alloantigens acquired from stimulator DC by DC of responder type. To investigate the reasons why DC and not other cells stimulate an MLR, synergy between DC and other cell types was investigated. Synergy was found exclusively between DC; macrophages, B cells or L cells transfected with MHC class II molecules did not contribute. When allogeneic DC were mixed in culture, transfer of MHC molecules between DC was observed as assessed by flow cytometry. Freshly obtained cell-free supernatants from cultured DC contained MHC class II and stimulated primary allogeneic MLR. DC of responder type acquired allogeneic MHC molecules from the supernatants and stimulated proliferation in syngeneic T cells. The capacity of DC both to shed and to acquire MHC molecules may contribute to their potency in stimulating primary responses, and could explain why passenger DC within allografts provide a potent stimulus for graft rejection.

Animals↗
PubMed1997

Human blood dendritic cells: binding to vascular endothelium and expression of adhesion molecules.

To investigate the binding properties of dendritic cells (DC) to vascular endothelium, a comparative analysis was undertaken of DC, monocytes and lymphocytes isolated from the blood of 25 healthy subjects using monolayers of human umbilical vein endothelial cells as the adherence substrate. More blood DC (mean 24% adherence) were adherent to endothelial monolayers than monocytes (mean 18%; P < 0.001) and lymphocytes (mean 12%; P < 0.001). When the monolayers were pretreated with tumour necrosis factor-alpha (TNF-alpha) all leucocyte populations exhibited an increased attachment, but there was still greater binding of DC (mean 37% adherence) in comparison with monocytes (mean 23%; P < 0.001) and lymphocytes (mean 18%; P < 0.001). Flow cytometric analysis revealed that in relation to monocytes and lymphocytes the DC had a higher surface expression of the adhesion molecules CD11a (P < 0.05), CD11c (P < 0.005) and CD54 (P < 0.005) but a lower prevalence of cells bearing CD49d (mean 38%; P < 0.05) and the homing receptor CD62L (mean 14%; P < 0.001). CD1a was present on 22% of DC and virtually absent from the surface of monocytes and lymphocytes. The intensity of expression of the beta1-integrins, CD49c, CD49d and CD49e was greater on DC than lymphocytes and monocytes (P < 0.05). Antibody blocking studies demonstrated that DC binding to untreated and TNF-alpha-treated endothelium was dependent upon the expression of CD11a, CD18 and CD49d, and the simultaneous application of anti-CD18 and anti-CD49d antibodies produced an approximate 70% inhibition of adhesion (P < 0.001). Thus, the expression of both beta1- and beta2-integrins contributes to the adhesive interaction between DC and endothelium.

Cell Adhesion↗
PubMed1995

A phase II study of oral piritrexim in recurrent high-grade (III, IV) glioma.

Piritrexim is a lipid-soluble drug which is as effective an inhibitor of dihydrofolate reductase as methotrexate. Phase I and II studies have indicated activity in some tumour types. Because of its lipophilicity we have conducted a phase II study in recurrent high-grade malignant glioma (grades III and IV). Twenty-seven patients were treated with 25 mg p.o. three times daily for five consecutive days, repeated weekly, with provision for dose escalation or reduction according to toxicity. Five patients received less than 4 weeks' treatment because of disease progression or death. Twenty-two patients were evaluable for response. One complete and one partial response was seen (duration 262+ and 241+ weeks) and 13 patients had static disease for a median duration of 13 weeks (range 7-35). The major toxicity was myelosuppression. This response rate of 9% of evaluable patients is much lower than that seen for some conventionally used drugs and we conclude that piritrexim is unlikely to be of value in the management of high-grade gliomas.

Administration, Oral↗
PubMed1995

CD4 expression on dendritic cells and their infection by human immunodeficiency virus.

Infection of dendritic cells (DC) by human immunodeficiency virus (HIV) has been disputed. Employing a fluorescence-activated cell sorter, DC, identified by the absence of membrane markers for T, B, natural killer (NK) and monocytic cells and by high levels of MHC class II DR antigen, were shown to express low levels of CD4. Immunomagnetic beads were used to separate blood low density cells, which are enriched for DC, into CD4-positive and -negative populations. Examination of these cells by electron microscopy showed an increase in the percentage of cells with DC morphology in the CD4-positive fraction and a reduction in the CD4-negative fraction. Electron microscopy of semi-purified DC preparations infected in vitro for 5 days with HIV-1 revealed morphologically distinct veiled DC with mature virions on the cell surface and virus budding through the cell membrane. Further evidence for the growth of HIV in DC was provided by experiments in which DC were extensively depleted of contaminating lymphocytes and monocytes prior to infection. Estimation of provirus load by a nested PCR indicated that after 5 days an infection level of one provirus copy per five cells could be achieved. After 7 days the provirus copy number could exceed the cellular genome copy number, suggesting that some cells had more than one provirus. Infectious virus could not be demonstrated in these cultures after 24 h but was detected after 5 or 7 days. Infection of DC in the presence of antibodies against CD4 was inhibited and suggests infection occurs via a CD4-dependent pathway. These results confirm that DC are susceptible to HIV infection in vitro. The immunological consequences of DC infection in vivo may be significant in the pathogenesis of AIDS.

Base Sequence↗
PubMed1993

Dendritic cells are potent antigen-presenting cells for microbial superantigen.

Dendritic cells (DC) were found to be more efficient than macrophages (MO) in activating T cell responses to Staphylococcal enterotoxin B (SEB) using the hanging drop techniques and DC as antigen presenting cells (APC). When superantigen was presented via DC, the activation of T cells was not dependent on antigen processing and MHC class II molecules IA and IE were involved.

Animals↗
PubMed1992

Phase I study of BW12C in combination with mitomycin C in patients with advanced gastrointestinal cancer.

The effect of combining the oxyhemoglobin-modifying drug BW12C with mitomycin C was investigated in a Phase I study of 18 patients with advanced gastrointestinal cancer. The dose of BW12C was increased from 20 mg/kg to 50 mg/kg to modify the hemoglobin-oxygen saturation curve by up to 48%. The period of maximum modification was then prolonged for up to 3 hr by a maintenance infusion of 4-6 mg/kg/hr. Pharmacokinetics of BW12C and mitomycin C were performed in all patients. Peak levels of BW12C increased from 139 micrograms/ml to 378 micrograms/ml. Plasma half life was independent of dose, with an average of 3.3 hr. BW12C was well tolerated with no severe side effects. Three patients had objective tumour responses.

Adenocarcinoma↗
PubMed1991

Morphology and phenotype of dendritic cells from peripheral blood and their productive and non-productive infection with human immunodeficiency virus type 1.

Immununoelectron microscopy of human peripheral blood mononuclear cells enriched for the presence of antigen-presenting dendritic cells (DC) has revealed two morphologically distinct cell types both expressing DR and DQ major histocompatibility complex (MHC) class II antigens but lacking T, B, natural killer (NK) and monocyte/macrophage markers. The first (type 1) has an irregular surface with numerous projections and shows cytoplasmic vacuoles. The second (type 2) has a paler nucleus showing only a thin rim of dense heterochromatin, large expanses of cytoplasm devoid of organelles, fewer vacuoles and a smooth cell boundary with few processes. In addition a few cells with a morphology similar to veiled cells of the afferent lymphatics (type 3 DC) were observed. Cells with a morphology intermediate between these three types were observed, suggesting that they may represent stages of the veiled cell differentiation pathway. Type 2 and 3 DC were shown by electron microscopy to be susceptible to productive infection with human immunodeficiency virus (HIV), whilst type 1 DC did not support virus growth. Examination of infected DC preparations by in situ hybridization revealed a higher number of DC positive for viral DNA and RNA than for RNA alone. Thus, in addition to productively infected DC, there may be some that are latently infected, contain defective virus genome or replicate virus at a very low level.

Acquired Immunodeficiency Syndrome↗
PubMed1990

An evaluation of the role of glutathione and its associated enzymes in the expression of differential sensitivities to antitumour agents shown by a range of human tumour cell lines.

Glutathione and its associated enzyme activities have been quantitated in a series of human tumour continuous cell lines expressing a range of in vitro sensitivities to certain antitumour agents. Fourteen different parental lines and 15 various drug- and X-ray-selected resistant sublines have been studied. Quantitative relationships between total glutathione levels and related enzyme activities and sensitivities to six clinically-useful antitumour drugs or X-rays, as judged by colony forming assays, have been determined by linear regression analysis. A positive correlation has been identified between glutathione levels and sensitivities to cisplatin. Adriamycin, or to X-rays. In addition, positive correlations were noted between cisplatin sensitivities and glutathione peroxidase and reductase activities and for Adriamycin responses with respect to glutathione peroxidase activity, using cumene hydroperoxide as substrate. However, no positive correlations were noted for glutathione levels or these enzyme activities with differential methotrexate, etoposide, vincristine or 5-fluorouracil cytotoxicities. Furthermore, no direct relationship was apparent between total glutathione S-transferase activities and any of these drug or X-ray sensitivities in this series of cell lines. These data appear to provide further evidence linking altered glutathione metabolism with differential cytotoxicities of certain clinically-useful antitumour agents.

Antineoplastic Agents↗
PubMed1990

Differential expression of drug resistance following in vitro exposure of human tumour cell lines to fractionated X-irradiation.

We have established that drug resistance can be expressed following in vitro exposure of tumour cells not only to antitumor drugs but also to fractionated X-irradiation. These data therefore suggest a biological basis for the clinical problem of drug resistance that can occur in patients with previously irradiated tumors. These observations, if confirmed, have clinical implications for the combined modality approach and need to be considered when attempting to identify resistant tumour cells in clinical specimens with the aim of monitoring or identifying effective drug regimens.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Enhanced DNA repair and tolerance of DNA damage associated with resistance to cis-diammine-dichloroplatinum (II) after in vitro exposure of a human teratoma cell line to fractionated X-irradiation.

In vitro exposure of a human testicular teratoma continuous cell line to fractionated X-irradiation resulted in the expression of resistance to cisplatin. In two independently-derived sublines, designated SUSA-DXR13 and SUSA-DXR10 resulting from treatment with either 13 fractions of 1.5 Gy (dose required to reduce survival by 1 log) or 10 fractions of 3 Gy (dose required to reduce survival by 2 logs) respectively, the IC50 values for cisplatin were 2- and 3.1-fold higher than that of the parental cell line. These sublines were cross-resistant to carboplatin (approximately 2-fold) but not to adriamycin and they showed unaltered radiosensitivities. The SUSA-DXR10 subline expressed some cross-resistance to mitomycin C and melphalan but none to Carmustine (BCNU). Total glutathione content was significantly reduced in both SUSA-DXR10 and SUSA-DXR13 cells, but the activities of associated enzymes, including the glutathione S-transferases, peroxidase and reductase were not modified significantly in the resistant sublines. Resistance in the SUSA-DXR10 subline was associated with significantly decreased 195mcisplatin uptake (p less than 0.01), but this was not reflected in a reduced level of drug bound to the DNA. The formation and removal of four platinum-DNA adducts were immunochemically quantitated. Immediately following drug treatment there was a higher level of total platination of the DNA in the resistant subline indicative of increased tolerance to DNA damage. After an 18 hr post treatment incubation, there was an indication of some repair capacity in this SUSA-DXR10 cell line, which was not apparent in the parental cells. Neither the parental nor the SUSA-DXR10 cell line was proficient in the repair of the major adduct Pt-GG, whereas both lines repaired the monofunctional adduct and the adduct Pt(GMP)2. SUSA-DXR10 cells were also able to repair the intrastrand adduct Pt-AG and interstrand crosslinks, unlike the repair deficient parental cells. Higher levels of interstrand crosslinks were characteristic of the SUSA-DXR10 subline. These observations therefore implicate both enhanced repair and increased tolerance of DNA damage as mechanisms of resistance to cisplatin resulting from in vitro exposure of a human teratoma cell line to fractionated X-irradiation.

Cisplatin↗