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Modulation of adhesion molecules by cytokines in vivo using human/severe combined immunodeficient (SCID) mouse chimeras.

Endothelial cell-leukocyte interactions involve multiple cell adhesion molecules acting in a programmed and sequential manner to create a leukocyte-endothelial cell adhesion cascade. To understand this process fully, in vivo models are needed. To accomplish this, we have transplanted pieces of normal human tissues onto immunodeficient mice to create chimeric animals. In one model, human skin is grafted and closely resembles normal skin histologically. The grafts retain their human vasculature and show low baseline expression of E-selectin, vascular cell adhesion molecule-1, and intercellular cell adhesion molecule-1. After intradermal injection of human cytokines, these cell adhesion molecules are markedly upregulated and an active inflammatory reaction ensues, with migration of murine leukocytes. Intravenous injection of an anti-human E-selectin antibody completely inhibits leukocyte accumulation induced by tumor necrosis factor-alpha but only partially inhibits leukotriene B4-induced inflammation. In a second model, human bronchus was successfully transplanted heterotopically into severe combined immunodeficient mice. Injection of tumor necrosis factor induced upregulation of E-selectin, intercellular cell adhesion molecule-1, and vascular cell adhesion molecule-1 in the submucosal microvessels, with slightly different kinetics than in the skin. In conclusion, human-severe combined immunodeficient chimeric mice represent a useful model system to study the regulation and function of human cell adhesion molecules in an in vivo setting.

Animals↗

Intramyocardial delivery of human CD133+ cells in a SCID mouse cryoinjury model: Bone marrow vs. cord blood-derived cells.

OBJECTIVE: The regenerative potential of endothelial and hematopoietic progenitor cells in the heart may vary according to their origin. This study was designed to compare the functional effects of CD133+ cells from human cord blood and bone marrow in a mouse model of myocardial injury. METHODS: 5 x 10(5) CD133+ cells from bone marrow (BM(CD133)) or cord blood (UCB(CD133)) were injected in the necrosis border zone of NOD/SCID (non-obese diabetic/severe combined immunodeficiency) mice with left ventricular cryoinjury (CI+). Transplanted cells were tracked by immunostaining for hNuclear antigen and by PCR for hDNA. Echocardiography was used to measure contractility. Scar size, capillary density, and cardiomyocyte apoptosis were evaluated by histology. In addition, the myogenic and endothelial differentiation capacity of BM(CD133) and UCB(CD133) was compared in vitro. RESULTS: DNA was detected 4 weeks after cell injection by PCR, but hNuc+ cells were found by immunostaining only after 48 h. Capillary density in both BM(CD133) and UCB(CD133) cell-treated CI+ mice was higher than in control CI+ mice, but not different between BM(CD133) and UCB(CD133) cell-treated hearts. There were no differences in scar size and myocardial mass among BM(CD133), UCB(CD133) and control CI+ mice, but cardiomyocyte apoptosis was reduced by both BM(CD133) and UCB(CD133) cells. The post-injury deterioration of shortening fraction (46.2+/-1% in sham-operated mice and 41.3+/-0.8% in control CI+ mice) was prevented by BM(CD133) cells (45.4+/-0.9%), but not by UCB(CD133) cells (40.8+/-0.7%). On the other hand, both BM(CD133) and UCB(CD133) cells abolished post-injury mortality. In vitro, neither cultivated BM(CD133) or UCB(CD133) cells developed into myocytes, but both readily differentiated towards an endothelial cell phenotype. CONCLUSIONS: While both cord blood and marrow CD133+ cells have some beneficial effects on post-injury angiogenesis and survival, only marrow cells appear to improve myocardial contractility.

AC133 Antigen↗

Molecular genotyping of the mouse scid allele.

Severe combined immunodeficiency (SCID) mice, which lack mature B- and T-cells, provide an important system for studies on immunity and disease. However, since the scid mutation is a single T-to-A transversion, genotypic analysis can be problematic. We have developed a rapid and simple sequence-based analysis that provides identification of both the scid and the wild-type (+) allele. This allows unequivocal identification of scid/scid, scid/+ and +/+ individuals. The method is of greatest utility for discerning scid/+ from +/+ animals during genetic complementation studies, but may be of value for routine SCID colony control as well.

Alleles↗

The SCID-hu mouse: an in-vivo model for HIV-1 pathogenesis and stem cell gene therapy for AIDS.

Animal models are critical to the investigation of human immunodeficiency virus type 1 (HIV-1) pathogenesis. However, normal animal models are either uninfectable with HIV-1, or if infected, do not display HIV-1 induced pathology. Here, we describe how the severe combined immunodeficient mouse (SCID), implanted with human fetal thymus and liver, has been used to model HIV-1 pathogenesis and anti-retroviral gene therapy. Unable to reject the human tissue, these chimeric mice provide the investigator with a human hematolymphoid organ which, following infection by HIV-1, may more closely mimic the situation seen in humans than standard in-vitro culture systems.

Acquired Immunodeficiency Syndrome↗

Attenuation of the vaccine Oka strain of varicella-zoster virus and role of glycoprotein C in alphaherpesvirus virulence demonstrated in the SCID-hu mouse.

The SCID-hu mouse implanted with human fetal tissue is a novel model for investigating human viral pathogenesis. Infection of human skin implants was used to investigate the basis for the clinical attenuation of the varicella-zoster virus (VZV) strain, V-Oka, from which the newly licensed vaccine is made. The pathogenicity of V-Oka was compared with that of its parent, P-Oka, another low-passage clinical isolate, strain Schenke (VZV-S), and VZV-Ellen, a standard laboratory strain. The role of glycoprotein C (gC) in infectivity for human skin was assessed by using gC-negative mutants of V-Oka and VZV-Ellen. Whereas all of these VZV strains replicated well in tissue culture, only low-passage clinical isolates were fully virulent in skin, as shown by infectious virus yields and analysis of implant tissues for VZV DNA and viral protein synthesis. The infectivity of V-Oka in skin was impaired compared to that of P-Oka, providing the first evidence of a virologic basis for the clinical attenuation of V-Oka. The infectivity of V-Oka was further diminished in the absence of gC expression. All strains except gC-Ellen retained some capacity to replicate in human skin, but cell-free virus was recovered only from implants infected with P-Oka or VZV-S. Although VZV is closely related to herpes simplex virus type 1 (HSV-1) genetically, experiments in the SCID-hu model revealed differences in tropism for human cells that correlated with differences in VZV and HSV-1 disease. VZV caused extensive infection of epidermal and dermal skin cells, while HSV-1 produced small, superficial lesions restricted to the epidermis. As in VZV, gC expression was a determinant for viral replication in skin. VZV infects human CD4+ and CD8+ T cells in thymus/liver implants, but HSV-1 was detected only in epithelial cells, with no evidence of lymphotropism. These SCID-hu mouse experiments show that the clinical attenuation of the varicella vaccine can be attributed to decreased replication of V-Oka in skin and that tissue culture passage alone reduces the ability of VZV to infect human skin in vivo. Furthermore, gC, which is dispensable for replication in tissue culture, plays a critical role in the virulence of the human alphaherpesviruses VZV and HSV-1 for human skin.

Animals↗

Human immunodeficiency virus infection of human lymph nodes in the SCID-hu mouse.

The SCID-hu mouse is a small animal in which human hematolymphoid organs can be engrafted and maintained in vivo. In this study, parameters are described for reproducible infection of SCID-hu mice after i.v. inoculation. Infection was found to be dependent upon the time after inoculation, the virus isolate, the titer of virus, and the human target organ implanted into the mouse. Ten to 14 days after the i.v. administration of HIV isolates derived freshly from patients (e.g., JR-CSF, JR-FL, SM), 100% of engrafted human lymph nodes in SCID-hu mice were infected; greater than 95% of these animals were also viremic. Implants of human thymus or connective tissue, as well as the endogenous murine hematolymphoid organs, were not infected. As demonstrated by a combination of in situ hybridization and immunohistochemistry, both T-lymphoid and myelomonocytic lineage cells were infected in this system. HIV isolates that have been adapted to growth in vitro (e.g., HTLV-IIIb) were not infectious. When either 3'-azido-3'-deoxythymidine (AZT) or 2',3'-dideoxyinosine (ddIno) was administered to SCID-hu mice before HIV infection, the animals were protected in dose ranges similar to those used in man. This animal model may now be used as an efficient intermediate step between the lab and the clinic to study the infectious process in vivo and to best select efficacious antiviral compounds against HIV.

Animals↗

The SCID-ra mouse: rat T-cell differentiation in the severe combined immunodeficient mouse.

The SCID-hu mouse model offers the possibility to study the human thymus in vivo in an isolated xenogeneic environment. Whilst studying the toxicology of the human thymus using the SCID-hu model, a "control" model to test for differences in toxicokinetics due to the different localization of the thymus is desirable when SCID-hu data have to be extrapolated to the normal human situation. For this reason, SCID-ra mice were constructed by implanting rat fetal or postnatal thymus and liver explants under the renal capsule of severe combined immunodeficient (SCID) mice. Implantation of rat fetal thymus in combination with fetal liver resulted in thymus grafts with a histological appearance that was virtually identical to that of normal age-matched rat thymus. T cells of rat origin were found in the circulating blood and lymphoid organs of the recipient mice. After implantation of postnatal thymus and liver, the thymus grafts showed a dysplastic morphology. These grafts were devoid of thymocytes and consisted mainly of thymic microenvironmental components and large numbers of thymic macrophages. Some SCID-ra mice showed signs of graft-versus-host (GVH) reactions in the skin. The incidence of GVH reactions was higher with increasing developmental stage of the donor material used for implantation.

Animals↗