Interleukin-12 p40- and Fas Ligand-Dependent Apoptotic Pathways Involving STAT-1 Phosphorylation Are Triggered during Infection with a Virulent Strain of Toxoplasma gondii

Toxoplasma gondii is an opportunistic intracellular parasite. Infection with the high-virulence T. gondii strain RH induces inflammatory cytokine overproduction and uncontrolled apoptosis in lymphoid organs. Here, we show by fluorescent terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay and binding of fluorescein isothiocyanate-conjugated VAD-FMK, an irreversible pan-caspase inhibitor, that parasite-triggered apoptosis occurs among CD4(+), CD8(+), B220(+), Gr-1(+), and NK1.1(+) splenic populations. Caspases 8 and 9 were activated during infection, implicating cell surface death receptors and mitochondria in apoptosis. Induction of apoptosis was absent among all cell populations in both interleukin-12 (IL-12) p40- and Fas ligand (FasL)-negative mice. STAT-1 phosphorylation correlated with onset of apoptosis during infection, but in the absence of IL-12 p40 and functional FasL, activation of this transcription factor failed to occur. The results demonstrate T. gondii-induced activation of multiple apoptotic pathways, dependent upon both IL-12 p40 and FasL, that may play a role in the lethal pathology of infection

Production of Replication-Defective Retrovirus by Transient Transfection of 293T cells

Our lab studies human myeloproliferative diseases induced by such oncogenes as Bcr-Abl or growth factor receptor-derived oncogenes (ZNF198-FGFR1, Bcr-PDGFRα, etc.). We are able to model and study a human-like disease in our mouse model, by transplanting bone marrow cells previously infected with a retrovirus expressing the oncogene of interest. Replication-defective retrovirus encoding a human oncogene and a marker (GFP, RFP, antibiotic resistance gene, etc.) is produced by a transient transfection protocol using 293T cells, a human renal epithelial cell line transformed by the adenovirus E1A gene product. 293 cells have the unusual property of being highly transfectable by calcium phosphate (CaPO(4)), with up to 50-80% transfection efficiency readily attainable. Here, we co-transfect 293 cells with a retroviral vector expressing the oncogene of interest and a plasmid that expresses the gag-pol-env packaging functions, such as the single-genome packaging constructs kat or pCL, in this case the EcoPak plasmid. The initial transfection is further improved by use of chloroquine. Stocks of ecotropic virus, collected as culture supernatant 48 hrs. post-transfection, can be stored at -80°C and used for infection of cell-lines in view of transformation and in vitro studies, or primary cells such as mouse bone marrow cells, that can then be used for transplant in our mouse model

Murine retroviral bone marrow transplantation models for the study of human myeloproliferative disorders.

Human myeloproliferative diseases are common hematologic disorders characterized by clonal overproduction of maturing myeloid or erythroid cells, often caused by expression of a mutant, dysregulated tyrosine kinase (TK). These diseases can be accurately modeled in laboratory mice by the retroviral transfer of a mutant TK gene into murine hematopoietic stem and progenitor cells, followed by transplantation of these cells into irradiated recipient mice. This yields a model system for analyzing the molecular pathophysiology of these conditions and provides a platform for testing therapies, particularly molecularly targeted new chemical entities (NCEs). The Basic Protocol in this unit describes the preparation of mouse bone marrow cells to express the relevant human oncogene before transplanting them into irradiated recipient mice. An alternate protocol describes a similar technique that allows specific induction of lymphoproliferative disease by some TKs. Support protocols for generating and titering retroviral stocks are also included