Cytomegalovirus infection after orthotopic liver transplantation is restricted by a pre-existing antiviral immune response of the recipient

The Human Cytomegalovirus, from Oncomodulation to Oncogenesis

Besides its well-described impact in immunosuppressed patients, the role of human cytomegalovirus (HCMV) in the pathogenesis of cancer has been more recently investigated. In cancer, HCMV could favor the progression and the spread of the tumor, a paradigm named oncomodulation. Although oncomodulation could account for part of the protumoral effect of HCMV, it might not explain the whole impact of HCMV infection on the tumor and the tumoral microenvironment. On the contrary cases have been reported where HCMV infection slows down the progression and the spread of the tumor. In addition, HCMV proteins have oncogenic properties per se, HCMV activates pro-oncogenic pathways in infected cells, and recently the direct transformation of cells following HCMV infection has been described, which gave rise to tumors when injected in mice. Thus, beyond the oncomodulation model, this review will assess the direct transforming role of HMCV-infected cells and the potential classification of HCMV as an oncovirus.

Transient residence of a seropositive organ is sufficient to transfer human cytomegalovirus to a seronegative recipient

Many aspects of the pathogenesis of human cytomegalovirus (HCMV) infection in liver transplantation remain unclear. This study examined the transfer of HCMV from the transient residence of a seropositive organ in seronegative recipients. All subjects receiving >1 orthotopic liver transplant (LT) were identified from an LT database. The patients of interest were HCMV-seronegative LT recipients who received their first organ from a seropositive donor, and subsequently a second LT from a seronegative donor within 30 days. Of 98 patients identified, 6 met these criteria and 4 developed viremia; in 2 cases, after the seropositive organ was in situ for 28 and 109 h. We can therefore conclude that 28 h is sufficient to allow HCMV to transmit, but the minimum time has not yet been defined.

Role of vascular endothelial growth factor in protection of intrahepatic cholangiocytes mediated by hypoxic preconditioning after liver transplantation in rats

OBJECTIVE

To investigate the effect on intrahepatic cholangiocytes mediated by hypoxic preconditioning (HP) after liver transplantation and the role of vascular endothelial growth factor (VEGF).

MATERIALS AND METHODS

This experiment was based on a model of rat orthotopic liver autotransplantation. Sprague-Dawley rats were randomly divided into 3 groups: normal control, autotransplantation (AT), and HP. The HP group was subjected to 8% oxygen atmosphere for 90 minutes before surgery. At 6, 12, 24, and 48 hours after autotransplantation, the rats were killed for testing .Serum total bilirubin, direct bilirubin, and alkaline phosphatase concentrations were determined. The microstructure of cholangiocytes and the ultramicrostructure of cholangioles were determined. Immunohistochemistry was used to detect the expression of VEGF and the proliferation rate of cholangiocytes.

RESULTS

Total bilirubin, direct bilirubin, and alkaline phosphatase concentrations in the AT group increased considerably more than in the HP group during the entire interval (P < .05). Light microscopy demonstrated that the microstructure of cholangiocytes in the AT group was damaged more seriously than in the HP group. At transmission electron microscopy, the ultramicrostructure of cholangioles was changed more obviously than in the HP group. The expression of VEGF on cholangiocytes and the proliferation rate of cholangiocytes were higher in the HP group than in the AT group over the entire experiment (P < .05).

CONCLUSION

Hypoxic preconditioning has a protective effect on cholangiocytes after liver autotransplantation. The mechanism may be related to HP-induced overexpression of VEGF on cholangiocytes.

Cytomegalovirus cell tropism

The human cytomegalovirus (HCMV) can infect a remarkably broad cell range within its host, including parenchymal cells and connective tissue cells of virtually any organ and various hematopoietic cell types. Epithelial cells, endothelial cells, fibroblasts and smooth muscle cells are the predominant targets for virus replication. The pathogenesis of acute HCMV infections is greatly influenced by this broad target cell range. Infection of epithelial cells presumably contributes to inter-host transmission. Infection of endothelial cells and hematopoietic cells facilitates systemic spread within the host. Infection of ubiquitous cell types such as fibroblasts and smooth muscle cells provides the platform for efficient proliferation of the virus. The tropism for endothelial cells, macrophages and dendritic cells varies greatly among different HCMV strains, mostly dependent on alterations within the UL128-131 gene locus. In line with the classification of the respective proteins as structural components of the viral envelope, interstrain differences concerning the infectivity in endothelial cells and macrophages are regulated on the level of viral entry.

Visualization and microscopic quantification of HCMV-peptide-specific cytotoxic T lymphocytes using tetramer binding

To monitor the frequencies of virus-specific cytotoxic T lymphocytes (CTLs), FACS analyses were performed detecting lymphocyte-specific surface molecules and tetramer binding, as marker for peptide-specificity. Aim of this investigation was to establish an alternative protocol for the quantification of virus-specific CTLs using tetramer binding and microscopic analyzing. The frequencies of HCMV-pp65-peptide-specific CTLs in the blood of eight different HLA-A*0201-positive, HCMV-IgG antibody-positive donors were analyzed with both methods. Using FACS analyses, a median of 0.8% and, using the microscopic analyses, a median of 3.0% was detected in the CD3+CD8+ cells. After enrichment of HCMV-pp65-peptide-specific CTLs using the interferon-gamma secretion assay followed by expansion in cell culture, a median of 90.6% using FACS analyses and a median of 87.1% using the microscopic analyses was detected. Thus, the staining protocol presented in this investigation is an alternative approach to detect and to quantify virus-specific CTLs in low as well as in high frequencies.

Epidemiology, pathogenesis and prevention of congenital cytomegalovirus infection

Cytomegalovirus is the most common cause of congenital infection. Congenital cytomegalovirus infection can follow both primary and recurrent maternal infections. It is associated with a significant burden of disease and death. The determinants of mother-to-child transmission and the pathogenesis of symptomatic fetal infection remain poorly understood. For a long time, congenital cytomegalovirus infection has been a neglected disease. Recently, the Institute of Medicine has recognized that the development of a vaccine against congenital cytomegalovirus infection is a public health priority, which should stimulate research in this area. The development of antiviral therapies to prevent symptoms in infected newborns also represents an important area of research.