The study of human hematopoietic cells and the human immune system is hampered by the lack of a suitable experimental model. Experimental data are presented showing that human fetal liver hematopoietic cells, human fetal thymus, and human fetal lymph node support the differentiation of mature human T cells and B cells after engraftment into mice with genetically determined severe combined immunodeficiency. The resultant SCID-hu mice are found to have a transient wave of human CD4+ and CD8+ T cells and human IgG (immunoglobulin G) in the peripheral circulation. The functional status of the human immune system within this mouse model is not yet known.

Objectives Glucose metabolism plays a fundamental role in supporting the growth, proliferation and effector functions of T cells. We investigated the impact of HIV infection on key processes that regulate glucose uptake and metabolism in primary CD4+ and CD8+ T cells. Design and methods Thirty-eight HIV-infected treatment-naive, 35 HIV+/combination antiretroviral therapy, seven HIV+ long-term nonprogressors and 25 HIV control individuals were studied. Basal markers of glycolysis [e.g. glucose transporter-1 (Glut1) expression, glucose uptake, intracellular glucose-6-phosphate, and L-lactate] were measured in T cells. The cellular markers of immune activation, CD38 and HLA-DR, were measured by flow cytometry. Results The surface expression of the Glut1 is up-regulated in CD4+ T cells in HIV-infected patients compared with uninfected controls. The percentage of circulating CD4+Glut1+ T cells was significantly increased in HIV-infected patients and was not restored to normal levels following combination antiretroviral therapy. Basal markers of glycolysis were significantly higher in CD4+Glut1+ T cells compared to CD4+Glut1− T cells. The proportion of CD4+Glut1+ T cells correlated positively with the expression of the cellular activation marker, HLA-DR, on total CD4+ T cells, but inversely with the absolute CD4+ T-cell count irrespective of HIV treatment status. Conclusion Our data suggest that Glut1 is a potentially novel and functional marker of CD4+ T-cell activation during HIV infection. In addition, Glut1 expression on CD4+ T cells may be exploited as a prognostic marker for CD4+ T-cell loss during HIV disease progression.

SCID-hu mice with human fetal thymic or lymph node implants were inoculated with the cloned human immunodeficiency virus-1 isolate, HIV-1JR-CSF. In a time- and dose-dependent fashion, viral replication spread within the human lymphoid organs. Combination immunohistochemistry and in situ hybridization revealed only viral RNA transcripts in most infected cells, but some cells had both detectable viral transcripts and viral protein. Infected cells were always more apparent in the medulla than in the cortex of the thymus. These studies demonstrate that an acute infection of human lymphoid organs with HIV-1 can be followed in the SCID-hu mouse.

The study of human hematopoietic cells and the human immune system is hampered by the lack of a suitable experimental model. Experimental data are presented showing that human fetal liver hematopoietic cells, human fetal thymus, and human fetal lymph node support the differentiation of mature human T cells and B cells after engraftment into mice with genetically determined severe combined immunodeficiency. The resultant SCID-hu mice are found to have a transient wave of human CD4+ and CD8+ T cells and human IgG (immunoglobulin G) in the peripheral circulation. The functional status of the human immune system within this mouse model is not yet known.

Human fetal bone fragments implanted in the immunodeficient C.B-17 scid/scid (SCID) mouse were shown to sustain active human hematopoiesis in vivo. Human progenitor cell activity was maintained for as long as 20 weeks after implantation and was associated with multilineage differentiation in the engrafted bone. Thus, the bone implants provided stem cells as well as the microenvironment requisite for their long- term maintenance and multilineage differentiation. Administration of human erythropoietin (Epo) stimulated human erythropoiesis in human bone implants. This animal model may facilitate direct analysis of a wide variety of physiologic and pathologic conditions of human bone marrow (BM) in vivo.