Selection of anionic exchange resins for removal of natural organic matter (NOM) fractions.

Early elimination of natural organic matter (NOM) by ion exchange (IEX) in water treatment is expected to improve subsequent water treatment processes and the final drinking water quality. Nine anionic exchange resins were investigated to remove NOM and specific NOM fractions determined by liquid chromatography in combination with organic carbon detection (LC-OCD) and fluorescence excitation-emission matrices (EEM). Breakthrough of NOM was predicted by model calculations using Freundlich isotherms and IEX rate experiments. The time to breakthrough varied from 4 to 38 days. Removal of specific NOM fractions proved to vary considerably for the different types of IEX resins, ranging from 1% to almost 60%. The removal of NOM fractions, specifically humic substances, increased with an increase in water content of the investigated IEX resins and with a decrease in resin size. The best-performing IEX resins consisted of the smallest resins and/or those with the highest water content. The worst-performing IEX resins reflected the highest exchanging capacities and the lowest water contents.

Tissue macrophages are infected by human cytomegalovirus in vivo.

On the basis of in vitro experiments, it has been suggested that cells of hematopoietic origin play a major role in the pathogenesis and latency of human cytomegalovirus (HCMV). To elucidate the in vivo importance of hematopoietic cells in acute HCMV infection, tissue sections from various infected organs were investigated by immunohistochemical double-labeling analyses. Monoclonal antibodies directed against distinct viral and cellular antigens were used to identify infected macrophages, polymorphonuclear cells, and lymphocytes. Macrophages and polymorphonuclear cells were targets for HCMV infection in different tissues. Viral proteins representing all stages of permissive HCMV infection were detected in macrophages, suggesting that these cells support the complete viral replication cycle. In polymorphonuclear cells, viral gene expression was restricted to the immediate early phase, indicating that these cells are abortively infected. These findings suggest that macrophages play an important role in the hematogenous spread of HCMV into solid organs.

Fibroblasts, epithelial cells, endothelial cells and smooth muscle cells are major targets of human cytomegalovirus infection in lung and gastrointestinal tissues.

High titre replication of human cytomegalovirus (HCMV) in cell culture is restricted to primary human fibroblasts. During acute infection in vivo, HCMV nucleic acids and antigens have been found in various organs. Using only morphological criteria, inconsistent data have been reported about the cell types that can be infected by HCMV. In particular, the role of fibroblasts in organ infections has remained unclear. To define accurately the target cells of HCMV in vivo, tissue sections from lung and gastrointestinal tract of patients suffering from acute HCMV infection were investigated using immunohistochemical double-labelling analyses. Monoclonal antibodies with defined specificity against immediate early (IE), early (E) and late (L) viral antigens and antibodies directed against cell marker proteins were employed to identify infected cells. The results demonstrated that a broad spectrum of cells was infected by HCMV in vivo. Consistent with their susceptibility in culture, fibroblasts formed a major population of HCMV-infected cells. In contrast, haemopoietic cells were only infrequently stained with virus-specific antibodies. Fibroblasts, epithelial cells, endothelial cells, smooth muscle cells and macrophages appeared to be permissive for HCMV replication. Contrary to this, polymorphonuclear cells showed only IE gene expression, indicating that these cells were abortively infected. The analysis of the distribution of infected cells in tissue supported the hypothesis that endothelial cells and monocytes/macrophages may play a crucial role in the haematogenous spread of HCMV; in contrast, fibroblasts, smooth muscle cells and epithelial cells may form the cell populations important for the multiplication and spread of the virus in infected tissues.

Presence of human cytomegalovirus (HCMV) immediate early mRNA but not ppUL83 (lower matrix protein pp65) mRNA in polymorphonuclear and mononuclear leukocytes during active HCMV infection.

During an active human cytomegalovirus (HCMV) infection, leukocytes, harbouring the HCMV lower matrix protein pp65 (ppUL83) are present in the peripheral blood and can be detected with the HCMV antigenaemia assay. In the present study, it was investigated whether the presence of pp65 in these cells was due to transcription of the virus genome or might be the result of uptake of this viral protein. Peripheral blood leukocytes of transplant recipients and AIDS patients with an active HCMV infection were investigated for the presence of HCMV immediate early (IE) antigen and pp65 using well characterized monoclonal antibodies, and for the presence of the corresponding mRNAs using non-radioactive in situ hybridization. Both mononuclear and polymorphonuclear cells were found to contain IE antigen and pp65. However, only mRNAs encoding IE antigen were found in these cells, whereas mRNAs encoding pp65 were not detected. In contrast, both IE antigen and pp65, as well as their corresponding mRNAs, were detected in the circulating late-stage HCMV-infected endothelial cells that were also present in the leukocyte fractions. These findings demonstrate that a restricted viral gene expression (transcription of IE genes) does occur in mononuclear and polymorphonuclear leukocytes. However, the abundant presence of the early antigen pp65 without detectable presence of the corresponding mRNA in these cells strongly indicates uptake of this protein by the phagocytic leukocytes, rather than de novo synthesis.

Ultrastructural analysis of circulating cytomegalic cells in patients with active cytomegalovirus infection: evidence for virus production and endothelial origin.

The presence of cytomegalic inclusion cells in the peripheral blood of patients with an active cytomegalovirus infection has recently been demonstrated. Immunologic staining showed that these cells were of endothelial origin. Study of circulating cytomegalic cells by transmission electron microscopy showed the cells to be productively infected with cytomegalovirus. Viral capsids were present in the nucleus and virus particles and dense bodies were found in the cytoplasm. The results indicate that these circulating cytomegalic cells could disseminate cytomegalovirus throughout the body. In addition, the finding of a cluster of cytomegalic cells in the peripheral blood linked together by zonula adherens type cell junctions is further evidence that these cells are of endothelial origin and suggests that the endothelial damage may be extensive.

Circulating cytomegalovirus (CMV)-infected endothelial cells in patients with an active CMV infection.

In 10 of 14 patients with an active cytomegalovirus (CMV) infection, distinctive large cells (35-45 microns in diameter) were present in the peripheral blood. Morphologically these cells closely resembled the classic cytomegalic inclusion cells, generally regarded as a diagnostic hallmark of CMV infection. Moreover, these cells were shown to express CMV antigens belonging to all three stages of the viral replication cycle, indicating a productive CMV infection. In addition, immunologic staining with monoclonal antibodies directed against cell differentiation and marker proteins showed that these circulating cytomegalic cells were of endothelial origin. The presence of CMV-infected endothelial cells in the peripheral blood of patients with an active CMV infection indicates that such an infection might be accompanied by widespread occult vascular damage.