Evidence for viruses in acute leukemia and Burkitt's tumor

Viruses, cancer and non-self recognition

Virus-host interactions form an essential part of every aspect of life, and this review is aimed at looking at the balance between the host and persistent viruses with a focus on the immune system. The virus-host interaction is like a cat-and-mouse game and viruses have developed ingenious mechanisms to manipulate cellular pathways, most notably the major histocompatibility (MHC) class I pathway, to reside within infected cell while evading detection and destruction by the immune system. However, some of the signals sensing and responding to viral infection are derived from viruses and the fact that certain viruses can prevent the infection of others, highlights a more complex coexistence between the host and the viral microbiota. Viral immune evasion strategies also illustrate that processes whereby cells detect and present non-self genetic material to the immune system are interlinked with other cellular pathways. Immune evasion is a target also for cancer cells and a more detailed look at the interfaces between viral factors and components of the MHC class I peptide-loading complex indicates that these interfaces are also targets for cancer mutations. In terms of the immune checkpoint, however, viral and cancer strategies appear different.

Epstein-Barr virus reprograms human B lymphocytes immediately in the prelatent phase of infection

Epstein-Barr virus (EBV) is a human tumor virus and a model of herpesviral latency. The virus efficiently infects resting human B lymphocytes and induces their continuous proliferation in vitro, which mimics certain aspects of EBV's oncogenic potential in vivo. How lymphoblastoid cell lines (LCLs) evolve from the infected lymphocytes is uncertain. We conducted a systematic time-resolved longitudinal study of cellular functions and transcriptional profiles of newly infected naïve primary B lymphocytes. EBV reprograms the cells comprehensively and globally. Rapid and extensive transcriptional changes occur within 24 h and precede any metabolic and phenotypic changes. Within 72 h, the virus activates the cells, changes their phenotypes with respect to cell size, RNA, and protein content, and induces metabolic pathways to cope with the increased demand for energy, supporting an efficient cell cycle entry on day 3 postinfection. The transcriptional program that EBV initiates consists of 3 waves of clearly discernable clusters of cellular genes that peak on day 2, 3, or 4 and regulate RNA synthesis, metabolic pathways, and cell division, respectively. Upon onset of cell doublings on day 4, the cellular transcriptome appears to be completely reprogrammed to support the proliferating cells, but 3 additional clusters of EBV-regulated genes fine-tune cell signaling, migration, and immune response pathways, eventually. Our study reveals that more than 11,000 genes are regulated upon EBV infection as naïve B cells exit quiescence to enter a germinal center-like differentiation program, which culminates in immortalized, proliferating cells that partially resemble plasmablasts and early plasma cells.

Viral Causes of Lymphoma: The History of Epstein-Barr Virus and Human T-Lymphotropic Virus 1

In 1964, Epstein, Barr, and Achong published a report outlining their discovery of viral particles in lymphoblasts isolated from a patient with Burkitt lymphoma. The Epstein-Barr virus (EBV) was the first human cancer virus to be described, and its discovery paved the way for further investigations into the oncogenic potential of viruses. In the decades following the discovery of EBV, multinational research efforts led to the discovery of further viral causes of various human cancers. Lymphomas are perhaps the cancer type that is most closely associated with oncogenic viruses: infection with EBV, human T-lymphotropic virus 1 (HTLV-1), human immunodeficiency virus (HIV), Kaposi sarcoma-associated herpesvirus/human herpesvirus 8, and hepatitis C virus have all been associated with lymphomagenesis. Lymphomas have also played an important role in the history of oncoviruses, as both the first human oncovirus (EBV) and the first human retrovirus (HTLV-1) were discovered through isolates taken from patients with unique lymphoma syndromes. The history of the discovery of these 2 key oncoviruses is presented here, and their impact on further medical research, using the specific example of HIV research, is briefly discussed.

Epstein-Barr virus infection negatively impacts the CXCR4-dependent migration of tonsillar B cells

The primary Epstein-Barr virus (EBV) infection occurs in the oropharynx, where the virus infects B cells and subsequently establishes latency in the memory B-cell compartment. EBV has previously been shown to induce changes in the cell surface expression of several chemokine receptors in cell lines and the transfection of EBNA2 or LMP1 into a B-cell-lymphoma-derived cell line decreased the expression of CXCR4. We show that in vitro EBV infection reduces the expression of CXCR4 on primary tonsil B cells already 43 hr after infection. Furthermore, EBV infection affects the chemotactic response to stromal cell-derived factor (SDF-1)alpha/CXCL12, the ligand for CXCR4, with a reduction of SDF-1alpha-induced migration. To clarify whether this reduced migration is EBV-specific or a consequence of cell activation, tonsillar B cells were either infected with EBV, activated with anti-CD40 and interleukin-4 (IL-4) or kept in medium. Activation by anti-CD40 and IL-4 decreased the CXCR4 expression but the CD40 + IL-4-stimulated cells showed no reduction of chemotactic efficacy. Our finding suggests that changing the SDF-1alpha response of the EBV-infected B cells may serve the viral strategy by directing the infected cells into the extrafollicular areas, rather than retaining them in the lymphoepithelium.

History and classification of human leukemia-lymphoma cell lines

Continuous human leukemia-lymphoma cell lines have become indispensable tools in hematological research since the establishment of the first human lymphoma cell line Raji in 1963. We summarize here historical landmarks in the establishment of unique leukemia-lymphoma-derived cell lines from the various cell lineages; their special importance in hematopoietic research is emphasized. The first cell lines were derived from African Burkitt lymphomas and were found to integrate the Epstein-Barr virus in their genome leading to the discovery and isolation of this virus. However, it was later recognized that not every cell line derived from a patient with leukemia-lymphoma represents a malignant cell line as residual normal B-lymphocytes can also be immortalized by EBV infection. During the following 20-30 years many other types of hematopoietic cell lines, commonly derived from hematopoietic neoplasms, were established. These panels of cell lines now span almost the whole spectrum of hematopoietic cell lineages (except for dendritric cells) and the various distinct stages of differentiation along the respective cell axes. From early on, cell lines became important tools for basic and clinical hematological research, initially mainly in the field of immunology, but later expanding to other areas also. It became apparent that leukemia-lymphoma cell lines are of monoclonal origin, are arrested at a discrete maturational stage during differentiation in each lineage, and show sustained and growth factor-independent or -dependent unlimited proliferation. Categorization of cell lines might best be based on the physiological stages of hematopoietic differentiation in the various cell lineages. For an adequate classification, detailed characterizations of both the cell lines and the primary cells from which the cell lines originated are absolutely mandatory. In summary, the availability of large numbers of continuous leukemia-lymphoma cell lines has greatly facilitated clinical and immunobiological studies of normal and malignant hematopoiesis. Human leukemia-lymphoma cell lines will continue to provide exquisite model systems for many biomedical disciplines.

The nephrotic syndrome associated with neoplasia: an unusual paraneoplastic syndrome. Report of a case and review of the literature

The nephrotic syndrome complicating malignancy in the absence of renal vein thrombosis, amyloid or neoplastic infiltration of the kidney is an unusual occurrence. A case of diffuse, well differentiated, lymphocytic lymphoma and lipoid nephrosis documented by light microscopy, electron microscopy and immunofluorescent studies is reported. A review of the literature revealed 76 case reports in which the nephrotic syndrome was associated with neoplasia. The most frequently associated neoplasms are Hodgkin's disease, various carcinomas, nonHodgkin's lymphoma and leukemia in descending order. The most frequent renal lesion in patients with the nephrotic syndrome associated with various carcinomas is membranous glomerulonephritis (81 per cent) as opposed to patients with lymphomas or leukemias who have predominantly lipoid nephrosis (60 per cent). The evidence is reviewed suggesting that the lesions in membranous nephropathy are immunologically mediated by tumor or viral antigen-antibody complexes and in lipoid nephrosis perhaps by a defect in t-lymphocyte function.

Cytogenetic studies on human lymphoblastoid cell lines from Burkitt's lymphomas and other sources

The occurrence and incidence of a characteristic banding abnormality in a No. 14 chromosome has been studied in Burkitt-lymphoma-derived and certain other EB virus-associated lymphoblastoid cell lines. The abnormality was readily detected in 7 out of 7 Burkitt lines, and when present could be seen in 100% of cells with recognizable No. 14 chromosomes. In contrast, the abnormality was not observed in 775 cells from 31 infectious mononucleosis-derived lines nor in 450 cells from 18 lines obtained from cord blood lymphocytes experimentally transformed by EB virus in vitro. The significance of the abnormality as an indication of cells transformed by the virus in vivo is discussed, and the importance of this considered in relation to a possible oncogenic role for EB virus in man.

EB virus and the treatment of lymphomas

The high incidence of EB virus infections (and possibly of other viruses) in patients with African lymphoma and, to a lesser extent, in patients with lymphosarcoma in the temperate zones, is thought to be due to its being a passenger virus which persists in the human body and, since it is lymphotropic, presents an opportunistic infection of proliferating lymphoid cells. The thesis is put forward that by entering the cell nucleus, the virus renders malignant lymphoid cells more vulnerable to cytotoxic drugs. Hence a deliberate policy of EB virus inoculation before starting chemotherapy might achieve a more rapid response and longer remissions in indigenous lymphomas of the temperate zones, and might possibly render drug-resistant cases once more drug-sensitive.

Ultrastructural Study of Burkitt Lymphoma Cell Lines (EB-2 and EB-3) Growing in Infant Rats

Newborn rats were inoculated with cell suspension of EB-2 or EB-3 Burkitt lines by Southam of the Sloan Kettering Institute, New York. The kidney tumors of the inoculated animals were studied at the electron microscope showing ultra-structural features similar to the original Burkitt tumor and to the several African lymphoma cell lines established in vitro. Two types of cells were described: type I closely resembles the Burkitt lymphoblasts, type II has the morphology of undifferentiated blasts. This cellular variability and the similarity of the II cell type to phytohaemagglutinin transformed lymphocytes are discussed. The absence of herpes-like particles in this material might be related to the lack of cell degeneration.

Electron microscopic localization of herpesvirus-type particles in Marek's disease

Upon cultivation of chicken lymphoid tumors induced by Georgia isolate of Marek's disease, clusters of refractile rounded cells appeared consistently in the cell cultures. Intranuclear mature, immature, enveloped, and empty herpesvirus-type particles, usually associated with smaller particles, were observed in all rounded cells in the affected areas. Cytoplasmic inclusions containing mature enveloped virus particles were also seen in the rounded cells. Often fibroblasts growing in the vicinity of the cytopathic effect area contained a few herpesvirus-type particles. The original tumors prior to cultivation did not reveal any virus particles, and the virus in infected cultures was always cell-associated. Control cell cultures neither developed the rounded cells nor demonstrated the presence of any type of virus particles.