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K Seidel

Publications and source records attributed to K Seidel.

At least 19 recordsLinked to original sources
PubMed1996

Bone marrow transplantation for severe aplastic anemia from genotypically HLA-nonidentical relatives. An update of the Seattle experience.

This report updates the results of marrow transplantation at the Fred Hutchinson Cancer Research Center for patients with severe aplastic anemia whose donors were HLA-nonidentical relatives. Between 1970 and 1993, 40 patients received transplants for severe aplastic anemia from related donors other than HLA genotypically matched siblings. Nine patients (group 1) were conditioned with cyclophosphamide (Cy) at 50 mg/kg for 4 doses and received marrow from phenotypically HLA-matched relatives. With the exception of one accidental death, all patients are alive and disease free 3-18 years after transplantation. Thirty-one patients received marrow from HLA-mismatched relatives who differed by one or more loci. Fifteen of these patients (group 2) received Cy at 50 mg/kg for 4 doses without total body irradiation (TBI) and none survived. Because of failure to sustain engraftment in 9 of 14 evaluable patients in group 2, the regimen for HLA-mismatched patients was changed in 1984 to include Cy at 60 mg/kg for 2 doses and TBI was added at 1200 cGy to increase immunosuppression (group 3). Sixteen patients in group 3 received marrow grafts after failure to respond to immunosuppressive therapy. Eight of the 16 patients in group 3 remain alive without disease between 1.5 and 11.3 years after transplantation. In conclusion, transplants from phenotypically HLA-identical related donors can be carried after Cy alone and results are comparable to those observed with genotypically HLA-identical siblings. Transplants from related donors mismatched for one or more HLA loci require a more intensive conditioning regimen, for example, one containing TBI, to achieve sustained engraftment.

Adolescent↗
PubMed1996

The varicella-zoster virus ORF66 protein induces kinase activity and is dispensable for viral replication.

Varicella-zoster virus (VZV) open reading frames (ORFs) 47 and 66 encode proteins that are homologous to a family of eukaryotic serine-threonine kinases. Prior studies showed that the VZV ORF47 protein has kinase activity in vitro and is dispensable for replication in cultured cells. To examine the role of the ORF66 protein during infection, we constructed VZV recombinants that are unable to express either the ORF66 protein (ROka 66S) or both the ORF47 and ORF66 proteins (ROka 47S/66S). VZV unable to express ORF66 grew to titers similar to those of the parental VZV (ROka) in vitro; however, VZV lacking both ORF66 and ORF47 grew to titers lower than those of ROka. Nuclear extracts from ROka 66S- or ROka 47S-infected cells showed a 48-kDa phosphoprotein(s); a phosphoprotein with a similar size was not present in nuclear extracts from ROka 47S/66S-infected cells. To determine the role of the ORF66 protein in the phosphorylation of specific VZV-encoded proteins, we immunoprecipitated known VZV phosphoproteins (ORF4, ORF62, ORF63, and ORF68 proteins) from nuclear extracts of phosphate-labeled cells infected with ROka, ROka 66S, or ROka 47S/66S. Each of the VZV phosphoproteins was phosphorylated to a similar extent in the presence or absence of either the ORF66 protein or both the ORF66 and ORF47 proteins. From these studies we conclude (i) neither ORF66 alone nor ORF66 and ORF47 in combination are essential for VZV growth in cultured cells, (ii) ORF66 either is a protein kinase or induces protein kinase activity during infection, and (iii) the VZV phosphoproteins encoded by ORF4, ORF62, ORF63, and ORF68 do not require either ORF66 alone or ORF66 and ORF47 for phosphorylation in vitro.

Base Sequence↗
PubMed1996

Tacrolimus (FK506) and methotrexate regimens to prevent graft-versus-host disease after unrelated dog leukocyte antigen (DLA) nonidentical marrow transplantation.

We previously reported an synergism between methotrexate and tacrolimus (FK506) in preventing graft-versus-host disease (GVHD) in dogs given DLA-nonidentical unrelated marrow grafts after 9.2 Gy of total body irradiation (TBI). Methotrexate was given at 0.4 mg/kg i.v. on days 1, 3, 6 and 11 and FK506 at 0.15 mg/kg/day i.m. on days 0-8 and 0.5 mg/kg/day orally on days 9-90. Half of the dogs became long-term survivors. A major toxicity was gastrointestinal, and 25% of dogs died with intussusception. The current study addresses the problem of intussusception by making changes in drug doses used. In one group of dogs, FK506 was reduced to 0.075 mg/kg i.m. on days 1-8, while methotrexate was administered per original schedule. In a second group, methotrexate was reduced to a single dose on day 7, while FK506 was either administered per the original or reduced-dose schedule. None of the 17 current dogs developed intussusception, however, all but two dogs died with GVHD (n = 12) or graft failure (n = 3). Only two dogs survived after transient GVHD. Results show that there is little room for maneuvering FK506 or methotrexate doses, and hopes of reducing gastrointestinal toxicity by dose modifications while retaining the ability to prevent GVHD were not fulfilled.

Animals↗
PubMed1995

DLA-identical bone marrow grafts after low-dose total body irradiation: effects of high-dose corticosteroids and cyclosporine on engraftment.

Previous studies found that marrow allografts from DLA-identical littermates resulted in survival of 60% of recipient dogs after an otherwise lethal dose of 450 cGy of total body irradiation (TBI), either because of successful allografts or autologous recovery after rejection of the allografts. Forty percent of dogs died with marrow aplasia after allograft rejection. The current study asked whether allogeneic engraftment could be enhanced and survival improved by treating allograft recipients with high doses of corticosteroids or with cyclosporine (CSP), administered either before or after transplantation. Five dogs in group 1 received corticosteroids beginning on day -5 and ending on day 32 after transplant. The starting dose was 12.5 mg of prednisone per kilogram orally twice daily. All five dogs rejected their allografts; three died early with marrow aplasia and two showed endogenous marrow recovery. Nine dogs received CSP from day -6 to day -1 before transplantation at a dose of 20 mg/kg/d intravenously administered in divided doses. All nine dogs rejected the marrow allograft; six died with marrow aplasia and three survived with endogenous marrow recovery. Seven dogs received CSP after transplantation at a dose of 30 mg/kg/d orally from day -1 to day 35. All seven had sustained allografts (two mixed chimeras and five complete donor-type chimeras) and became healthy long-term survivors without graft-versus-host disease. These results extend previous observations and confirm that grafts of marrow from DLA-identical littermates improved survival of dogs exposed to low but otherwise lethal doses of TBI. Additional therapy with high-dose corticosteroids administered peritransplantation and posttransplantation or CSP administered before transplantation neither enhanced the rate of allogeneic engraftment nor improved survival; however, CSP administered after transplantation resulted in successful allografts and event-free survival in all cases.

Adrenal Cortex Hormones↗
PubMed1995

Myelosuppressive conditioning improves autologous engraftment of genetically marked hematopoietic repopulating cells in dogs.

We have studied the role of different conditioning regimens for engraftment of genetically marked hematopoietic repopulating cells in dogs. Peripheral blood (PB) and/or marrow cells collected after treatment with recombinant canine stem cell factor (rcSCF) or cyclophosphamide were transduced in a vector-containing long-term culture system. Three different vector-producing cell lines with similar viral titers were used. In two of them, the neo-containing LN vector was packaged either in the PA317 cell line with an amphotropic murine retrovirus envelope or the PG13 cell line with the gibbon ape leukemia virus (GALV) envelope. The MFG/GC vector produced in PA317 cells contained the human glucocerebrosidase gene. Nineteen dogs received either no conditioning (group A, n = 5), irradiation to both humeri with 1,000 cGy (group B, n = 5), a sublethal dose of cyclophosphamide 40 mg/kg (group C, n = 4), a sublethal dose of 200 or 300 cGy total body irradiation (TBI) (group D, n = 3), or an otherwise lethal dose of 920 cGy TBI (group E, n = 3) before intravenous (groups A, C, D, E) or intramedullary (group B) infusion of the transduced autologous hematopoietic cells. Transduction efficiency of hematopoietic cells at the time of infusion into the animals was similar among the different conditioning groups. Dogs were observed for at least 6 months. PB granulocytes were obtained at least every 3 weeks after transplant and analyzed by polymerase chain reaction for the presence of the transduced genes. The percentages of positive results in dogs more than 4 weeks after transplantation were 0% without conditioning, 5% with local irradiation, 18% with sublethal cyclophosphamide, 33% with sublethal TBI, and 17% with otherwise lethal TBI. Analyzing the influence of conditioning regimens by a generalized estimating equation (GEE) technique, which considered the use of different retrovirus vectors and the number of mononuclear cells infused as potential confounding variables, we found that engraftment of genetically marked repopulating cells was significantly improved (P < .001) in dogs receiving systemic conditioning with either otherwise lethal TBI, sublethal TBI, or sublethal cyclophosphamide compared to dogs with local irradiation only or no conditioning. Within the limitation of the experimental design, these data suggest that myeloablative or myelosuppressive conditioning improves engraftment of genetically marked hematopoietic repopulating cells.

Animals↗
PubMed1995

Cellular events in the evolution of experimental diabetic nephropathy.

In several models of progressive glomerular disease, mesangial cell proliferation, phenotypic change and increased growth factor expression precede up-regulation of genes for extracellular matrix components (ECM) and mesangial expansion. To examine these events in diabetic nephropathy (DN) we conducted sequential studies of glomeruli in rats with streptozotocin induced DN. We found prominent mesangial cell proliferation at three days (4.34 +/- 2.24 PCNA + cells/glom vs. 1.6 +/- 0.74 in controls, P < 0.001) associated with increased alpha-actin expression. PDGF B-chain mRNA was slightly increased at day one, and PDGF B-chain immunostaining was slightly increased at days one and six. Staining for bFGF was significantly increased at three days (2.2 +/- 0.6 vs. 1.2 +/- 0.1 in controls, P < 0.01). There was also an early increase in platelets in glomeruli of diabetic animals, and platelet depletion significantly inhibited the early phase of proliferation. In addition to mesangial cell proliferation, a prominent glomerular macrophage infiltration began at day three and peaked at day 30 (3.94 +/- 1.47 vs. 2.08 +/- 1.13 in controls, P < 0.01). TGF-beta mRNA increased at days 14 and 30. Insulin treatment prevented mesangial cell proliferation, actin expression, and macrophage infiltration, and normalized TGF-beta expression at 14 and 30 days. These multiple cellular events preceded any detectable increases in glomerular gene expression or deposition of collagen I, IV or laminin.

Animals↗
PubMed1995

Impact of patient weight on non-relapse mortality after marrow transplantation.

We hypothesized that severely overweight patients were at an increased risk of transplant-related toxicity and that this might be reflected in increased mortality soon after transplant. All patients transplanted between January 1985 and January 1992 were included in the analysis; data were complete for 2238 (1662 adults, 576 children ( > 18 years). Since we were interested primarily in acute post-transplant toxicity, survival through day 150 was the primary end-point analyzed. Children and adults were analyzed separately since the decision to transplant or not to transplant may differ between the two populations. Log rank statistics and multivariable Cox regression analyses showed that adults at 95% to > 145% of ideal body weight (BW) experienced comparable non-relapse mortality and survival. In contrast, survival among patients at 85-95% or < 85% of ideal BM was significantly worse (P = 0.004 and P = 0.0001, respectively) than in the 95-145% weight category. Results in children were similar except that the differences were less prominent (comparisons of < 85%, 85-95% and > 145% categories vs. 95-145% category showed P values of 0.22, < 0.01 and 0.66, respectively). The observed weight effect was not explainable in terms of the composition of the lower weight categories in regards to nine other known or suspected risk factors. In addition to weight, patient age, diagnosis, type of transplant, year of transplant, graft-versus-host disease (GVHD) prophylaxis and GVHD grades II-IV were also significantly associated with outcome. Thus, the present analysis shows that underweight patients are at an increased risk of death in the early period after transplant.

Adolescent↗
PubMed1995

Effects of rhIL-11 on normal dogs and after sublethal radiation.

The effects of recombinant human interleukin-11 (rhIL-11) were studied in normal dogs and dogs given otherwise sublethal total-body irradiation (TBI) without marrow transplantation. Ten normal dogs were given rhIL-11 subcutaneously, twice daily for 14 days at varying doses, two dogs at 30 micrograms/kg/day, four dogs at 60 micrograms/kg/day, two dogs at 120 micrograms/kg/day, and two dogs at 240 micrograms/kg/day. Peripheral blood platelet counts increased in all dogs. The increase in platelet counts ranged from 1.4 to 3.1 times the pre-treatment level. The greater increases of platelets were associated with higher doses (p = 0.01). No change in platelet size was evident except at the dose of 240 micrograms/kg/day. There were no changes in the total white blood cell (WBC) count or differential. A higher proportion of megakaryocytes with a DNA content of 32N/64N was observed in dogs treated with rhIL-11 at day 7 (n = 6) than for control dogs that did not receive rhIL-11 (n = 7; p = 0.01). In both peripheral blood and marrow, significantly increased hematopoietic progenitors (i.e, colony-forming unit granulocyte/macrophage [CFU-GM]) were present 7 and 14 days after the start of treatment. Concentrations of serum fibrinogen increased by a median of 155 mg/dL at day 7 of rhIL-11 (p < 0.01). Cholesterol also increased by a median of 52 mg/dL at day 14 (p < 0.01). There was a single death of a non-irradiated dog from pneumonitis on day 15 after the start of rhIL-11 administration at a dose of 120 micrograms/kg/day. All other non-irradiated dogs tolerated rhIL-11 without any significant adverse effects. Five dogs were given 200 cGy TBI without marrow grafting, followed by 240 micrograms/kg/day rhIL-11 subcutaneously in two divided doses for 28 days starting within 2 hours of TBI. The results in this group were compared with 10 dogs that had previously or concurrently been given 200 cGy without marrow grafting or hematopoietic growth factors. Two of the five treatment dogs died of pneumonitis on day 13 compared to one death among 10 control dogs on day 24. Among dogs that survived to hematologic recovery, the rhIL-11 dogs had decreased platelet counts (< 150,000) for a median of 24 days (range = 24 to 41) compared to a median of 28 days (range = 21-40) for the control group. Treatment with rhIL-11 increased platelet counts, platelet size, ploidy number of megakaryocytes, and marrow and peripheral blood CFU-GM in normal dogs.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Aplastic anemia: analysis of stromal cell function in long-term marrow cultures.

Marrow samples from 89 patients with aplastic anemia (AA) were evaluated for their ability to grow stromal layers in standard long-term marrow cultures (LTMCs). Results were highly variable: 6.8% failed to grow any stromal cells (group I); 42.5% either failed to grow to confluency or appeared to have a decreased number of adipocytes and/or macrophages (group II); and 52.8% appeared as normal confluent cultures with fibroblasts, adipocytes, and macrophages (group III). Analyses of patient data suggested that group I patients had a longer disease duration and poorer survival (P = .07). Enzyme-linked immunosorbent assay analysis of cytokine production was performed on 20 of the normal-appearing AA LTMCs and 12 LTMCs established from normal donors. Significant differences between the AA and control groups were apparent for macrophage inflammatory protein-1 alpha (MIP-1 alpha), interleukin-1 receptor antagonist (IL-1ra), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), and leukemia-inhibitory factor (LIF). The most dramatic differences observed were elevated levels of MIP-1 alpha and GM-CSF and decreased levels of IL-1ra, particularly after IL-1 alpha stimulation. In contrast, IL-1 alpha stimulation of AA LTMCs produced levels of IL-6, LIF, and G-CSF comparable with those of controls. These data suggest that defects exist within the microenvironment of some AA marrows. Whether the majority of these defects are the cause or consequence of aplasia is not clear. However, we speculate that some of these abnormalities may contribute to the maintenance of the hypoplastic state and, in extreme cases, prevent engraftment of donor marrow.

Adipose Tissue↗
PubMed1994

Fractionated versus single-dose total body irradiation at low and high dose rates to condition canine littermates for DLA-identical marrow grafts.

We explored in dogs the immunosuppressive properties of 450 cGy total body irradiation (TBI) delivered from two opposing 60Co sources, as assessed by the criterion of successful engraftment of allogeneic genotypically DLA-identical littermate marrow. Two questions were asked in this study. Firstly, does dose rate affect the immunosuppressive effect of TBI when administered in a single dose? Secondly, does fractionation alter the immunosuppression of TBI when delivered at a very fast dose rate? Dose rates studied included 7 and 70 cGy/min, and fractionation involved four fractions of 112.5 cGy each, with 6-hour minimum interfraction intervals. Six of 7 dogs receiving 450 cGy single-dose TBI at 70 cGy/min showed sustained engraftment of the allogeneic marrow, compared with 1 of 7 dogs receiving single-dose TBI at 7 cGy/min (P = .01). Fractionated TBI at 70 cGy/min resulted in sustained allogeneic engraftment in 3 of 10 dogs, a result that was statistically significantly worse than that with single-dose TBI at 70 cGy/min (P = .03) and not statistically different (P = .24) from that with fractionated TBI delivered at 7 cGy/min (0 of 5 dogs engrafted). A single dose of 450 cGy of TBI delivered at a rate of 70 cGy/min is significantly more immunosuppressive than the same total dose delivered at 7 cGy/min. Fractionated TBI at 70 cGy/min is significantly less immunosuppressive than single-dose TBI at 70 cGy/min and not significantly different from fractionated TBI administered at 7 cGy/min. Results are consistent with the notion that significant DNA repair in lymphoid cells is possible during interfraction intervals at the relatively high dose rate of 70 cGy/min.

Animals↗
PubMed1994

Effect of recombinant canine granulocyte-macrophage colony-stimulating factor on hematopoietic recovery after otherwise lethal total body irradiation.

Recombinant canine granulocyte-macrophage colony-stimulating factor (rcGM-CSF) was studied in normal dogs and in dogs receiving otherwise lethal total body irradiation (TBI) without marrow transplant. Five normal dogs receiving 25 micrograms/kg of rcGM-CSF by subcutaneous (SC) injection twice daily (BID) for 14 days showed increases in peripheral blood neutrophil counts of three to five times the baseline. Platelet counts decreased during administration of rcGM-CSF to a mean nadir of 52,800. Ten dogs received 400 cGy TBI at 10 cGy/min from two opposing 60Co sources and no marrow graft. Within 2 hours of TBI, rcGM-CSF was begun at a dose of 50 micrograms/kg SC BID for 5 doses and then continued at 25 micrograms/kg SC BID for 21 days. Only 1 of the 10 dogs receiving rcGM-CSF survived with complete and sustained recovery of hematopoiesis. One of 13 historical control dogs survived after 400 cGy with no hematopoietic growth factor or marrow infusion. Results with rcGM-CSF were compared with previous and concurrent data with G-CSF studied in the same model. Of 10 dogs receiving G-CSF, 8 survived with complete and sustained hematopoietic recovery, a significantly better survival than that seen with rcGM-CSF (P = .006). Neutrophil counts were sustained at higher levels after TBI for the first 18 days in the G-CSF group (P < .016) and the neutrophil nadirs were higher. No differences in neutrophil nadirs were noted between the rcGM-CSF and control groups. Dogs treated with rcGM-CSF experienced a more rapid decline of platelet counts than G-CSF-treated or control dogs over the first 18 days (P < .001). The nadir of the platelet count was higher in the control group than in either the G-CSF or rcGM-CSF group and no significant difference was observed between the G-CSF and rcGM-CSF groups. After otherwise lethal TBI (400 cGy) in dogs, rcGM-CSF was not effective in promoting hematopoietic recovery or improving survival.

Animals↗
PubMed1994

Varicella-zoster virus (VZV) open reading frame 10 protein, the homolog of the essential herpes simplex virus protein VP16, is dispensable for VZV replication in vitro.

Varicella-zoster virus (VZV) open reading frame 10 (ORF10) protein in the homolog of the herpes simplex virus type 1 (HSV-1) protein VP16. VZV ORF10 transactivates the VZV IE62 gene and is a tegument protein present in the virion. HSV-1 VP16, a potent transactivator of HSV-1 immediate-early genes and tegument protein, is essential for HSV-1 replication in vitro. To determine whether VZV ORF10 is required for viral replication in vitro, we constructed two VZV mutants which were unable to express ORF10. One mutant had a stop codon after the 61st codon of the ORF10 gene, and the other mutant was deleted for all but the last five codons of the gene. Both VZV mutants grew in cell culture to titers similar to that of the parental virus. To determine whether HSV-1 VP16 alters the growth of VZV, we constructed a VZV mutant in which VP16 was inserted in place of ORF10. Using immune electron microscopy, we found that HSV-1 VP16 was present in the tegument of the recombinant VZV virions. The VZV VP16 substitution mutant produced smaller plaques and grew to a lower titer than parental virus. Thus, VZV ORF10 is not required for growth of the virus in vitro, and substitution of HSV-1 VP16 for VZV ORF10 impairs the growth of VZV.

Base Sequence↗
PubMed1994

[Reduction of bacteria and viruses in purification plant discharges using microfiltration in a model plant].

Microfiltration through a membrane matrix of a nominal pore size of 0.2 microns has been applied for advanced treatment of mechanically and biologically treated wastewater. Elimination of bacteria and coliphages as well as the decrease in some chemical constituents were studied at a flow rate of 80 l/h. Microfiltration resulted in a reduction of E. coli, coliform bacteria, fecal streptococci and of coliphages by more than 4 logs in the filtrate. Thus, the quality requirements of EC Directives for bathing water (EC, 76/160) could be maintained. As a result of microfiltration, a 43 +/- 13% removing of the total phosphorous compounds (Pt) in the pre-filtered secondary effluent from 11 +/- 2 mmol/m3 (0.34 +/- 0.06 mg/l) to 6 +/- 2 mmol/m3 (0.19 +/- 0.06 mg/l) was measured. The dosage of FeCl3 (between 30 and 150 mmol/m3) as coagulant before microfiltration improved the reduction of Pt to result in an average value of 75 +/- 16%. After adding FeCl3, orthophosphates (PO4-P) could be efficiently reduced by microfiltration. Thus, PO4-P concentrations in effluent samples were, in most cases, below the detection limit (0.01 mmol/m3).

Bacteria↗
PubMed1993

The transcriptional activation domain of varicella-zoster virus open reading frame 62 protein is not conserved with its herpes simplex virus homolog.

Varicella-zoster virus (VZV) open reading frame 62 (ORF62) encodes an immediate-early protein that transactivates expression of VZV, herpes simplex virus (HSV), and cellular genes in transient expression assays. VZV ORF62 is homologous to HSV ICP4 and pseudorabies virus immediate-early (IE180) proteins. All three viral proteins have conserved DNA binding domains that recognize similar sites in their corresponding promoters. Here, we show that the transcriptional activation domain of ORF62 is located near the amino terminus of the protein and is not conserved with the activation domain of ICP4. A 161-amino-acid activation domain of ORF62 activates transcription to a level comparable to that of the potent HSV VP16 activation domain; much of the activity is contained in the first 90 amino acids of ORF62. Deletion of the activation domain from full-length ORF62 markedly reduced transactivating activity. These experiments indicate that while VZV ORF62 and HSV ICP4 have conserved amino acid sequences, including their DNA binding domains, the transcriptional activation domains are poorly conserved.

Animals↗
PubMed1993

[Inactivation of bacteria and coliphages in surface water highly polluted by secondary effluent and purified by flocculation and filtration by means of UV irradiation at a pilot plant scale].

The water of a channel in Berlin which is highly polluted by municipal sewage effluent is treated at the phosphate elimination plant (PEP) Tegel by flocculation and filtration in order to reduce eutrophication in the following Lake Tegel. The elimination of bacteria and coliphages in the effluent of the PEP was investigated in a scale pilot UV irradiation reactor installed at the outlet of the PEP Tegel. The influence of technical parameters such as flow rate and the arrangement of 23 UV lamps in the reactor on the inactivation was tested. The UV irradiation dose was calculated 119 mJ/cm2 and 49 mJ/cm2 at a flow rate of 50 m3/h and 120 m3/h, respectively and for an irradiation zone of 97.5 cm. The colony count of bacteria and concentrations of coliform organisms, E. coli, and feacal streptococci as well as the plaque forming units of coliphages in the influent of the UV reactor were reduced 2-3 lg units by an irradiation dose of 119 mJ/cm2. These elimination was found being only one lg unit at a UV irradiation dose of 49 mJ/cm2. The concentration of E. faecalis and Coliphages f2 seeded into the influent of the UV reactor decreased after UV irradiation by 119 mJ/cm2 by 2-4 lg units and 1-2 power of magnitude, respectively. A UV dose of 49 mJ/cm2 caused only a 90% elimination of E. faecalis and a 75% inactivation of Coliphages f2. Due to heterogenous distribution and the different retention period of the inflowing water in the irradiation zone, the inactivation of E. faecalis and Coliphages f2 was unequal. Both test organisms decreased in the middle of the reactor up to 2 lg units more than at the sides of the reactor. The hygienic-microbiological quality of a secondary effluent from sewage treatment plants can be improved by a combination of flocculation-filtration and UV irradiation due to their additive elimination effect. However, this UV reactor, which was tested under field conditions can only ensure the inactivation of bacteria and coliphages in the pretreated effluent, if more homogenous distribution of the inflowing water can be achieved. Further, the water must be irradiated by a higher UV dose.

Coliphages↗