Resistance of human cytomegalovirus to benzimidazole ribonucleosides maps to two open reading frames: UL89 and UL56

2,5,6-Trichloro-1-beta-D-ribofuranosyl benzimidazole (TCRB) is a potent and selective inhibitor of human cytomegalovirus (HCMV) replication. TCRB acts via a novel mechanism involving inhibition of viral DNA processing and packaging. Resistance to the 2-bromo analog (BDCRB) has been mapped to the UL89 open reading frame (ORF), and this gene product was proposed as the viral target of the benzimidazole nucleosides. In this study, we report the independent isolation of virus that is 20- to 30-fold resistant to TCRB (isolate C4) and the characterization of the virus. The six ORFs known to be essential for viral DNA cleavage and packaging (UL51, UL52, UL56, UL77, UL89, and UL104) were sequenced from wild-type HCMV, strain Towne, and from isolate C4. Mutations were identified in UL89 (D344E) and in UL56 (Q204R). The mutation in UL89 was identical to that previously reported for virus resistant to BDCRB, but the mutation in UL56 is novel. Marker transfer analysis demonstrated that each of these mutations individually caused approximately 10-fold resistance to the benzimidazoles and that the combination of both mutations caused approximately 30-fold resistance. The rate and extent of replication of the mutants was the same as for wild-type virus, but the viruses were less sensitive to inhibition of DNA cleavage by TCRB. Mapping of resistance to UL56 supports and extends recent work showing that UL56 codes for a packaging motif binding protein which also has specific nuclease activity (E. Bogner et al., J. Virol. 72:2259-2264, 1998). Resistance which maps to two different genes suggests that their putative proteins interact and/or that either or both have a benzimidazole ribonucleoside binding site. The results also suggest that the gene products of UL89 and UL56 may be antiviral drug targets.     

Ein neues integrales Verfahren zur Quantifizierung der Grundwasserimmission, Teil I: Beschreibung der Grundlagen

A new investigation method was developed for a highly reliable assessment of groundwater contamination at waste sites or industrial locations. The method is based on an integral estimation of contaminant mass fluxes downstream of a pollutant source zone, employing an inversion of contaminant concentration time series measured within the discharge of pumping wells. Depending on the setup, the application of the method yields the total mass flux, as well as the contaminant concentration distribution over a control plane within a contaminant plume (see Ptak et al. 2000). Since there is no need to interpolate point scale concentration measurements, site assessment at a high level of certainty is obtained. The method was tested within a demonstration project and applied under conditions of practice for site assessment within a large (urban) industrialized area in the city of Stuttgart.     

Testfeld Süd: Einrichtung der Testfeldinfrastruktur und Erkundung hydraulisch-hydrogeochemischer Parameter des Grundwasserleiters

A former gasification plant with a variety of organic contaminants within the aquifer serves as a field test site. Both contaminants in phase (contamination source) and dissolved (contaminant plume) can be detected. After extending the test site infrastructure various methods for the investigation of groundwater flow and transport have been applied and compared. The geometry of the aquifer is variable and a pronounced heterogeneity of the hydraulic conductivity can be observed. The influence of the sedimentary setting on the structure of the aquifer is shown. A relation between discrete grain size distributions and the petrographical composition of the aquifer material is established. Using this relation, the sorption properties of the aquifer can be derived. Following the first measurements, the observed differential spreading of pollutants within the contaminant plume is influenced by microbial degradation. Further field tests to investigate the biodegradation rates are proposed.     

Cross-talk between gammadelta T lymphocytes and immune cells in humoral response

The role of gamma delta T cells in immunoregulation is largely unknown. In the current study we noted that gamma delta T cells play a positive role in the humoral response. These positively acting gamma delta T cells are required for the successful adoptive cell transfer of the humoral response, as well as for in vitro generation of plaque-forming cells (PFC). The presented results show that gammadelta T cells cause an increase in interleukin-10 (IL-10) production, which partly elucidates the mechanism of action of these cells. However, experiments with cell culture inserts strongly suggest that direct cell-cell contact between immune and gamma delta H-2-compatible regulatory T cells is critical to the exertion of the positive immunoregulatory function of gamma delta cells. The mechanism of cross-talk between these two cell populations is still not clear but we regard as most likely that the positively acting gamma delta T cells may interact with a complex of heat-shock protein-non-polymorphic MHC (IB) on the surface of T helper type 2 and/or B cells. This could provide, by direct cell-cell contact, the cognate recognition between gamma delta T-cell receptors and heat-shock protein-MHC that leads to positive internal signalling in the immune cells.     

Ein neues integrales Verfahren zur Quantifizierung der Grundwasserimmission, Teil II: Numerische Lösung und Anwendung in Eppelheim

A new investigation method for the integral assessment of the contaminant mass flux downstream of a waste site was presented in the first paper ( Teutsch et al. 2000). This second paper presents the first practical application of the new investigationmethod at an abandoned landfill site. The focus was on the extended, differential measuring approach, which yields, besides the total contaminant mass fluxes and mean concentrations, also the contaminant concentration distibution over a control plane perpendicular to the groundwater flow. In addition to testing of the technical and interpretation approaches it was an aim to demonstrage that the new investigation method is applicable also at low levels of contamination. Furthermore the maximum spatial resolution of the concentration distribution was to be determined.