Activation of HTLV-I long terminal repeat by stress-inducing agents and protection of HTLV-I-infected T-cells from apoptosis by the viral tax protein.

HTLV-I is etiologically implicated with tropical spastic paraparesis/HTLV-I associated myelopathy, adult T-cell leukemia and certain other diseases. However, after infection the virus enters into a dormant state, whereas the characteristics of the HTLV-I related diseases indicate that their genesis requires activation of the dormant virus by a Tax-independent mechanism. In the present study we demonstrate that a variety of stress-inducing agents (TPA, cisplatin, etoposide, taxol, and 3-methylcholanthrene) are capable of Tax-independent activation of HTLV-I LTR and that this activation is detected mainly in cells that are undergoing through the apoptotic process. Furthermore, it is demonstrated that both apoptosis induction and HTLV-I LTR activation are inhibited by Bcl-2 and by PKC, indicating that these two processes are mechanistically cross-linked. In addition, using an HTLV-I producing human T-cell line which permanently express the negatively transdominant tax mutant, Delta58tax, under the Tet-Off control system, we prove that the virally encoded Tax protein protects the host cells from apoptosis. Together, these data suggest that activation of the dormant virus in the carriers' infected T-cells by certain stress-inducing conditions and protecting these cells from the consequent apoptotic death by the viral Tax protein emerging after this activation, might be the basis for switching the virus from latency to a pathogenic phase.

Peripheral blood stem cells as a source for hemopoietic recovery following autologous bone marrow transplantation in childhood malignancy.

In an attempt to improve hemopoietic recovery after autologous bone marrow transplantation (ABMT), a project of peripheral blood stem cells (PBSC) harvest was initiated. Thirty-six children awaiting ABMT underwent 126 PBSC harvests primed by a conventional scheduled chemotherapy course and rGMCSF 5 micrograms/kg per day/s.c. Ages ranged from 12 months to 19 years and weight from 9 to 84 kg. PBSC harvest was carried out using the Fenwall CS 3000 Plus with the small volume collection chamber at a maximum whole blood flow rate of 15-45 ml/min; total volume processed was 1,700-10,000 ml. Total nucleated cells per collection was 0.35-5.62 x 10(8) cells per kg, and the number of CD34+ cells, 0.23-1.1 x 10(6)/kg. The number of colony forming units-granulocyte macrophages (CFU-GM) varied in these heavily pretreated patients from 0 to 5.3 CFU-GM x 10(4)/kg per collection. Immunophenotyping of the cells collected was performed by double staining for CD34, CD33, CD15, CD71, Ia and CD56. Most of the CD34+ cells were found to be CD38+; some were CD33+ and some CD33-. Low coexpression of CD34+ CD71+ cells may correlate with the low proliferating capacity of PBSC as compared to the BM cells. To date 22 children have undergone transplantation using combined autologous PBSC and bone marrow. We conclude that PBSC harvest is a feasible and safe procedure even in small children, and can be successfully performed following scheduled chemotherapy and administration of growth factors, resulting in substantial yield, also in heavily pretreated patients. This procedure is recommended in responding high risk patients at the stage of minimal residual disease and may replace ABMT in the future.

Heterogeneity of childhood acute lymphoblastic leukemia (ALL): monoclonal antibodies phenotyping and induction of differentiation in vitro.

Fifty-eight pediatric patients with non-T acute lymphoblastic leukemia (ALL) were diagnosed and evaluated at the Sambur Center of Pediatric Hematology Oncology. At least six subtypes of non-T ALLs were identified, corresponding to the various stages of B-cell differentiation, by utilizing an extensive panel of monoclonal antibodies directed against T- B- and myeloid-cell differentiation antigens. Moreover, leukemic cells expressing the phenotype of early B cells could be driven to differentiate along the B- cell lineage to express CALLA and BL antigens and cytoplasmic and/or surface immunoglobulins (IgM). A unique phenotype of non-T ALL was also identified. These leukemic cells expressed B cell antigen exclusively, i.e., HLA/DR and B4 (CD19). Myeloid-cell antigens, however, were expressed on these cells spontaneously after a 24-hour incubation in culture medium in vitro. In addition, leukemic cells of four patients with a phenotype of HLA/DR, CD19, and CD10 expressed antigens of the T-cell lineage: CD7 (3AI) and CD2 (leu 5), and/or of the myeloid cell lineage (My7). These results provide confirming evidence for the wide scope of the heterogeneity of ALL. It stresses the validity of accurate classification of leukemia to identify biologically and clinically unique subtypes of ALL, which bears specific prognostic parameters; and designates therapeutic protocols.