A Herpes saimiri oncogene causing peripheral T-cell lymphoma in transgenic mice.

Herpesvirus saimiri is an oncogenic virus causing rapid T-cell lymphomas in New World primates and rabbits. Deletion analysis of one strain of H saimiri has indicated an open reading frame, StpA, necessary for oncongenicity in monkeys. We have investigated the function of StpA in tumor induction by the generation of transgenic mice. Expression of two different constructs caused the development of peripheral lymphomas. The infiltrating cells were of T-cell origin, expressing mainly the CD4 phenotype and restricted sets of V beta chains. Thus, StpA is not only necessary for the oncogenicity of Herpesvirus saimiri, but is also sufficient for the induction of peripheral pleomorphic T-cell lymphomas.

Activation of HIV transcription by human foamy virus in transgenic mice.

BACKGROUND: Although infection by HIV-1 is the primary cause of AIDS, cofactorial agents of an infectious nature may be involved in the pathogenesis of the disease. The present work addresses the cofactorial potential of human foamy virus (HFV) in AIDS. It has been suggested that HFV seroprevalence reaches 5% in East Africa, and HFV seroprevalence in East African patients suffering from AIDS and AIDS-related complex may be as high as 20%. Although the pathogenic potential of HFV in humans has not yet been investigated in detail, HFV transgenic mice develop an encephalopathy reminiscent of some of the features of HIV-associated brain diseases. EXPERIMENTAL DESIGN: We set out to investigate the possibility that the regulatory genes of HFV may act as transcriptional cofactors of HIV. To study the effects of bel1, the transcriptional activator of HFV, on the HIV-1 LTR, we generated double transgenic mice for bel1 and for the HIV-1 LTR linked to a lacZ reporter gene. Moreover, to identify the cis-acting elements mediating bel1 action on the HIV LTR, we analyzed the consequences of deletions in the negative regulatory element or in the NF-kappa B binding sites. RESULTS: We demonstrate that bel1 is capable of activating the transcription of HIV-1 LTR in vivo. Such transactivational activity, however, was observed exclusively in a subset of hippocampal neurons, whereas cortical neurons expressing bel1 did not show transactivation. Transactivation was completely abolished by the deletion of the NF-kappa B binding sites. In contrast, deletion of the negative regulatory element region seems to enhance transactivation of bel1 on HIV-1 LTR over a prolonged period of time. CONCLUSIONS: Our study indicates that transcriptional transactivation of HIV-1 by HFV can be accomplished in vivo and is dependent on NF-kappa B binding sequences. Therefore, transcriptional transactivation is a potential mechanism of cooperation between HFV and HIV. It is conceivable that this phenomenon attains clinical significance in a situation of coinfection with both viruses.

Epithelial tumours induced by a herpesvirus oncogene in transgenic mice.

To investigate the role of herpesviral genes in tumourigenesis, transgenic mice were generated expressing STP-C, a transformation associated protein of the lymphoma inducing herpesvirus saimiri. Epithelial tumours developed in the salivary gland, pancreas, thymus and liver of transgenic mice within the first weeks of life. Thus, the target cells for tumour formation in the transgenic mice were surprisingly different from those of the herpesvirus from which the oncogene was derived. Our results identify STP-C as a herpesvirus oncogene sufficient for tumour induction without the cooperation of other viral gene products. Furthermore, the results demonstrate pleiotropic transforming capabilities of the STP-C oncogene and suggest that the specificity of lymphoma induction by the virus is determined by factors other than the oncogene itself.

[Classification and virus expression of primary cerebral lymphomas]. / Klassifikation und Virusexpression primär zerebraler Lymphome.

Fourty-three primary cerebral lymphomas (PCL) were histologically classified and examined for genome expression of Epstein Barr Virus (EBV) and human herpes virus 6 (HHV6) using dot blotting, polymerase chain reaction, and Southern blotting. Only 20 tumors (16 high grade and 4 low grade lymphomas) could be suitably placed into a category of the Updated Kiel Classification, whereas the non-classified 23 tumors were highly malignant B-lymphomas and referred to as small-cell (SC) or large-cell (LC) blastic PCL. Most of the LC PCL showed a tumor-like infiltration pattern with high cellular density and little remaining parenchyma, whereas the SC PCL more often showed an inflammation-like pattern characterized by loose arrangement of tumor cells and marked astrocytic, microglial and T-lymphocytic reaction. EBV genome was found in 3/3 AIDS cases, but in none of 40 immunocompetent cases, while HHV6 was detected in 2 tumors of immunocompetent patients. We conclude that (1) the Updated Kiel Classification is not applicable to a majority of PCL, and (2) EBV and HHV6 do not appear to play a major role in the pathogenesis of PCL in immunocompetent subjects.

Tumor necrosis factor alpha and lymphotoxin production in Hodgkin's disease.

It is likely that the characteristic histologic features of Hodgkin's disease reflect cytokine production by the tumor cell population. Tumor necrosis factor alpha (TNF-alpha) and lymphotoxin (tumor necrosis factor beta [TNF-beta]) are important inflammatory mediators with wide-ranging effects within the lymphoreticular system. The aim of the present study was to investigate TNF-alpha and lymphotoxin production in the Hodgkin's disease-derived cell lines L428 and L540. At the product level, both cytokines could be demonstrated by immunostaining with specific monoclonal antibodies. TNF-alpha could be demonstrated by means of an enzyme-linked immunosorbent assay in culture supernatants from both cell lines as well as in cell lysates of L428 and L540 cells. Cytotoxic activity could be achieved only in L428 supernatants. This cytotoxic activity could not be blocked by the addition of a polyclonal antibody against TNF-alpha, but was partially inhibited with the monoclonal antibody against lymphotoxin. Synthesis of TNF-alpha and lymphotoxin in both L428 and L540 was confirmed by demonstrating the intracellular-specific messenger RNA (mRNA) using specific cDNA clones in Northern blot analysis. In situ hybridization studies with the TNF-alpha cDNA probe gave positive hybridization signals in L428 and in L540. These results demonstrate the transcription, translation, and export of TNF-alpha and lymphotoxin in cultured Hodgkin's disease-derived cell lines. In addition, results of preliminary experiments are presented in which we demonstrate Reed-Sternberg cells positive for TNF-alpha protein and mRNA in different Hodgkin's disease tissue biopsies, indicating that, at least for TNF-alpha, our cell line data are relevant to the neoplastic population present in Hodgkin's disease tissue.

Immunoenzymatic assessment of interferon-gamma in Hodgkin and Sternberg-Reed cells.

The typical histological picture seen in Hodgkin's disease is consistent with the release of cytokines and other active mediators by the malignant cells, i.e., Hodgkin and Sternberg-Reed cells. Since interferon-gamma is regarded as an important regulator of the cytokine cascade, we have undertaken an immunohistological assessment of this mediator in Hodgkin's disease tissue biopsies. In approximately 50% of the cases investigated we found Hodgkin and Sternberg-Reed cells to be positive with antibodies against interferon-gamma. These in situ findings were substantiated by immunostaining of Hodgkin's disease-derived cell lines L428 and L540. L540 was consistently positive, whereas L428 was negative. It is noteworthy that L428 exhibit a B-cell pheno- and genotype, whereas L540 is of T-cell origin. These data are consistent with theories that propose that cytokine production by tumour cells is central to the pathogenesis of Hodgkin's lymphoma.