Inclusion bodies containing virus-like particles in acute lymphocytic leukaemia of childhood

Viral-like characteristics of particle aggregates in a lymphoblastic cell line

A lymphoblastic cell line (K45) established from a child with acute lymphoblastic leukemia (ALL) is characterized by a profusion of intracytoplasmic particle aggregates (PA) similar in morphology to those occurring in fresh childhood ALL cells. The PA in K45 cells were examined for morphology and capacity for nucleic acid synthesis to test the hypothesis that they are identical to those in fresh ALL cells, and also to identify characteristics which might distinguish PA from cell organelles and which might determine if they are viral-like. In contrast to cell organelles, the PA in both K45 and ALL cells were found to be characterized by a localized thickening of the particle wall. Furthermore, autoradiography of K45 cells showed uptake by PA of 3H uridine rather than 3H thymidine indicating an RNA composition. The presence of PA in profusion was associated with, but preceded necrotic death of K45 cells. These combined features suggest that the PA in K45 and in ALL cells are identical, that they are distinct from cell organelles, are not formed as a consequence of the initiation of cell death and that, while their exact nature remains unknown, a viral origin cannot be excluded.

Cytoplasmic inclusions and virus-like particles in blast cells in acute lymphoblastic leukemia

Cytoplasmic inclusions and virus-like particles are described in blast cells of peripheral blood from a 16-year-old female with acute lymphoblastic leukemia. Three kinds of inclusions were identified on electron microscopy. The first type of inclusion was single membrane-bounded vacuoles, some of which contained virus-like particles, the second was lysosome-like structures, and the third appeared to be of mitochondrial origin. Virus-like particles were round in shape and had a diameter of 26 to 58 nm. They consisted of an electron-dense outer membrane and an electron-lucent core. At the present time the exact nature and significance of these virus-like particles still remain unclear.

Acute lymphoblastic leukemia in children: current status, controversies, and future perspective

Disease-free survival (DFS) in childhood ALL is 60%, and survival in good, average, and poor prognostic groups defined by initial WBC and age is 90, 60, and 45%, respectively. Additional immunological, morphological, biochemical, cytokinetic, and cytogenetic factors have been identified, illustrating the heterogeneity of ALL and its derivation from malignant clones at various stages of differentiation and with varying rates of proliferation. Of biologic importance, these factors may refine further the characteristic features of clinically-determined prognostic groups. Multivariate analysis of large prospective trials with homogeneous therapy will be required to determine the independent prognostic importance of these factors. Current treatment strategies in ALL include (1) tailoring therapy and its intensity to prognostic groups; (2) multiple-drug combinations in induction; (3) early use of intrathecal (IT) methotrexate (MTX); (4) CNS prophylaxis with IT MTX alone in good prognosis patients and combined cranial radiation (CXRT), 1800 rads plus IT MTX, in average and poor prognosis patients. Current studies show a CNS relapse rate of 5% in all prognostic groups. Late neuropsychological defects caused by cranial XRT and IT MTX have prompted programs designed to reduce the potential late toxicity of CNS prophylaxis. More pronounced in younger children, these abnormalities include decreased IQ, visual-motor incoordination, poor performance in mathematics, and memory dysfunction. Until 1980, more intensive induction, consolidation, and maintenance therapy had failed to prolong DFS in children with a poor prognosis. In West Germany (Berlin-Frankfurt-Muenster protocol) a 70 to 75% DFS is seen in all patients regardless of initial WBC, suggesting that effective therapy will override prognostic factors. Ultra-high-dose MTX, without cranial radiation, is also showing promise in poor prognosis patients. Other issues include the optimal duration of therapy, the role of testicular biopsies, and prophylactic testicular radiation. Recent studies suggest that prognostic factors lose their significance after 2 years of continuous complete remission and that 2 years of maintenance therapy is adequate. Bilateral open-wedge testicular biopsies have identified occult testicular disease in 8 to 10% of males. A unified approach to children with leukemia/lymphoma, a group with a particularly poor prognosis, utilizing NHL-type therapy may be more effective than conventional ALL therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Characteristics of a cell line established from a child with familial acute myeloid leukaemia

The properties of an unusual new cell line from a child with acute myeloid leukaemia (AML) is described. The patient, his mother and grandmother all died within 2 years of AML. Karyotypic analysis suggests that the cells which grow in vitro represent a proliferation of the child's leukaemic cells. The presence of myeloid alkaline phosphatase in these cells suggests that they represent a proliferation of malignant myeloblasts. During the first year in culture a significant percentage of the cells formed E-rosettes, but the cells failed to react with monoclonal anti-T-cell antibodies. The cells are SmIg, Fc, C3 and EBNA negative. Ultrastructural examination of the cells revealed cytoplasmic inclusion bodies which contained virus-like particles. These inclusion bodies and particles were similar to those observed by us in two other human leukaemic cell lines and not unlike those in fresh human leukaemic cells, as reported by others.

Phenotypic characterization of a virus producing line established from a patient with leukaemia/lymphoma: comparison with T-lymphoblastic and myeloblastic lines

The properties have been studied of a haemic cell line established from a patient with longstanding non-Hodgkin's lymphoma after transformation to acute leukaemia. The cells are EBNA, Fc, C3 and SmIg and Ia-like antigen negative. The continuous in vitro proliferation and karyotype abnormalities suggest malignancy. The cells contain only the lymphoid type of alkaline phosphatase and a high level of terminal deoxynucleotidyl transferase and as they formed E-rosettes during the first year in culture they may be of T-cell lineage. Since the patients' leukaemic cells have not been studied it is impossible to know whether the cultured cells represent an in vitro proliferation of the patient's malignant cells or an outgrowth of a subpopulation of cells. In the cytoplasm of many cells inclusion bodies containing virus-like particles, similar to those observed in fresh human leukaemia cells, were often seen. As this new virus is biologically active, infection of the cells by virus may explain their continuous proliferation in vitro.

Transformation of normal bone-marrow cells by a leukaemic cell line associated with a presumptive new human virus

Intracytoplasmic leukovirus-like bodies were found in the cells and culture medium of a T-cell lymphoblast line established from a leukaemic patient. When the cells were lethally irradiated and added to normal bone-marrow cells the latter were transformed into continuous replication and produced the same types of virus-like particle.