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The development of a novel immunotherapy model of human ovarian cancer in human PBL-severe combined immunodeficient (SCID) mice.

The reported ability of SCID mice to accept xenografts of both human tumors and peripheral blood lymphocytes (PBL) provides the potential for the development of novel immunotherapy models in these animals. This study describes the development of a novel small animal model of human ovarian cancer. This was achieved by engrafting a human ovarian cancer cell line (Ovan-4) into the peritoneal cavity of immunodeficient SCID and immune reconstituted human PBL-SCID mice. When transplanted to SCID mice this cell line exhibited growth characteristics similar to the clinical disease observed in patients with implantation of metastatic nodules onto the interior surface of the peritoneal wall. Reconstituted human PBL-SCID mice challenged with identical numbers of Ovan-4 cells exhibited a significant increase in survival time, suggesting a role for cells of the human immune system in preventing the development of this type of malignancy in vivo. Furthermore, vaccination of human PBL-SCID mice against Ovan-4 produced tumour-specific human antibodies in the serum of these animals. Animals reconstituted with CD8-depleted PBL exhibited increased serum immunoglobulin levels and produced enhanced anti-Ovan-4 activity after vaccination. Subsequent challenge of these animals with Ovan-4 revealed a further increase in survival time. These results suggest that human antibodies may have a role in immunity against ovarian cancer and could be of therapeutic value in this type of disease.

Animals↗

Murine IL-2 receptor beta chain blockade improves human leukocyte engraftment in SCID mice.

Severe combined immunodeficient (SCID) mice accept human xenografts and can act as a model for human immune functions. Murine natural killer cells (NK), however, represent an important barrier for the reconstitution of SCID mice with human peripheral blood leukocytes (Hu-PBL). We investigated the effect on Hu-PBL survival of pretreatment with TM-beta1, a rat monoclonal antibody for the mouse IL-2 receptor beta chain. TM-beta1 greatly improved the survival of Hu-PBL. Human lymphocytes, predominantly T cells, survived in the peritoneum and infiltrated spleen and lungs already 1 week after engraftment and liver and thymus from 2 weeks on. Secondary humoral responses were evaluated with Hu-PBL from a donor immune to hepatitis-B surface Ag (HBsAg) and tetanus toxoid (TT). TM-beta1 pretreatment enhanced the recall Ig response to HBsAg and did not affect the baseline anti-TT Ig production. In conclusion, TM-beta1 pretreatment of SCID mice significantly improves the survival and functionality of the Hu-PBL graft.

Animals↗

Suppression of human anti-mouse idiotypic antibody responses in hu-PBL-SCID mice.

Severe combined immunodeficient (SCID) mice were engrafted with appropriate numbers of T cells and B plus mononuclear cells, which had been fractionated from normal human peripheral blood leukocytes (hu-PBLs). Treatment of these hu-PBL-SCID mice with a tolerogenic covalent conjugate of monomethoxypolyethylene glycol (mPEG) and an anti-ovalbumin, IgG1 murine monoclonal antibody, Mab-2, suppressed the human anti-mouse antibody responses to both the common (gamma 1,kappa) and the idiotypic determinants of Mab-2. Moreover, the Mab-2(mPEG)36 conjugate suppressed the immune responses of hu-PBL-SCID mice to the common and idiotypic determinants of murine monoclonal antibodies to the 2,4-dinitrophenyl residue and to human CD4, consisting also of gamma 1 and kappa chains. It is concluded that a tolerogenic mPEG conjugate of a murine monoclonal antibody induces pan-suppression of the human lymphoid system with respect to other murine monoclonal antibodies that share the isotypic determinants of the original one (here, Mab-2) incorporated in the conjugate. Hence, it may be anticipated that human anti-mouse antibody responses to any murine IgG monoclonal antibody would be suppressed by one of eight mPEG conjugates, each incorporating one of the four subclasses of IgG and one of the two light chains.

Animals↗

Primary central nervous system lymphoma following transfer of human peripheral blood lymphocytes into SCID mice.

Severe combined immunodeficiency (SCID) mice are genetically deficient in both B and T cells. To study immune-mediated phenomena in the CNS, myelin basic protein-reactive T cell clones, admixed with peripheral blood lymphocytes as a source of antigen-presenting cells, derived from a healthy human donor, were injected intracerebrally (IC) into 10 SCID mice. One mouse developed quadriplegia 2 months after the last injection. Autopsy revealed marked meningeal and parenchymal infiltration by large cell lymphoma. There was no evidence of lymphoma outside of the CNS. The majority of the tumor cells were positive for L26 (a human pan B cell marker), with some cells positive for UCHL-1 (a human pan T cell marker). The majority of the tumor cells were also positive for Epstein-Barr virus (EBV) genome by in situ hybridization. Thus, primary CNS, EBV-positive B cell lymphoma can be produced in SCID mice by IC injection of nontransformed human peripheral blood lymphocytes. This phenomenon can be used as a model system for the study of primary CNS lymphomas under immunodeficiency conditions.

Adoptive Transfer↗

Specific immunosuppression of human anti-murine antibody responses in hu-PBL-SCID mice.

Severe combined immunodeficient (SCID) mice were reconstituted with normal human peripheral blood leukocytes (PBLs) and were shown to produce a human anti-mouse immunoglobulin antibody response on immunization with heat-treated murine monoclonal IgG1 antibody to ovalbumin, referred to as ha-Mab-2. The human anti-mouse antibody response was proportional tot the number of B cells and mononuclear cells transferred from a given batch of PBL. However, pretreatment of hu-PBL-SCID mice with a tolerogenic covalent conjugate of monomethoxypolyethylene glycol (mPEG) and Mab-2 suppressed this response on subsequent injections of ha-Mab-2, and this suppression was shown to be antigen-specific, i.e., it did not suppress the antibody response to ovalbumin and did not affect the level of production of human immunoglobulin of hu-PBL-SCID mice. The suppression was due to the generation of human suppressor CD8+ T (Ts) cells, which down regulated CD4+ helper T cells in an antigen and HLA class I specific manner, i.e., these findings were in accord with the previously shown immunosuppressive effect of tolerogenic mPEG conjugates in normal mice.

Animals↗

Human immunodeficiency virus infection of human-PBL-SCID mice.

Severe combined immunodeficient (SCID) mice reconstituted with human peripheral blood leukocytes (hu-PBL-SCID mice) have inducible human immune function and may be useful as a small animal model for acquired immunodeficiency syndrome (AIDS) research. Hu-PBL-SCID mice infected with human immunodeficiency virus-1 (HIV-1) contained virus that was recoverable by culture from the peritoneal cavity, spleen, peripheral blood, and lymph nodes for up to 16 weeks after infection; viral sequences were also detected by in situ hybridization and by amplification with the polymerase chain reaction (PCR). Mice could be infected with multiple strains of HIV-1, including LAV-1/Bru, IIIB, MN, SF2, and SF13. HIV-1 infection affected the concentration of human immunoglobulin and the number of CD4+ T cells in the mice. These results support the use of the hu-PBL-SCID mouse for studies of the pathogenesis and treatment of AIDS.

Animals↗

High yields of anti-HLA human monoclonal antibodies can be provided by SCID mice.

In an attempt to develop a suitable model for increasing the yield of human anti-HLA mAbs, we have used mice with SCID for i.p. injection of two human-mouse heterohybridomas. HMP1 hybridoma secretes a DQB1*0201 allele-specific human mAb whereas HMP12 secretes a human mAb recognizing the DRB1*1101, 1102, 1103, and 1104 alleles. Both hybridomas could be grown in SCID mice as localized tumors with no apparent alteration in the morphology of the cells or in the immunoglobulin secretion. Ascitic fluid was produced that showed a 600- to 1000-fold increase in monoclonal antibody cytotoxic titer as compared with that obtained in tissue culture. HLA-DQB1* and DRB1* alleles recognized by ascites and supernatants from SCID-derived cultures were analyzed by microlymphocytotoxicity assay on a small panel of B-lymphoblastoid cell lines. The results show that HLA specificity was retained after in vivo passage.

Animals↗

Presence of murine retroviral sequences in human cell line transplanted in immunosuppressed SCID-mice.

The SCID-hu mouse, a severe combined immunodeficient mouse transplanted with human hematopoietic cells, has been proposed as an experimental model for HIV-1 infection. However, like other animal models for infectious diseases, the SCID-hu mouse should provide the replication of the experimental agent without conferring any alteration during growth in the host. In this study using Southern blot hybridization, in situ hybridization and PCR analysis we demonstrate the presence of specific murine retroviral sequences in human cells recovered from the in vivo passages in SCID mice. Since the acquisition of endogenous retrovirus by human cells was demonstrated after their growth in nude mice, the data reported here extend this observation to the SCID model.

Animals↗

Cytokine dependent growth of human TF-1 leukemic cell line in human GM-CSF and IL-3 producing transgenic SCID mice.

Although severe combined immunodeficient (SCID) mice are considered useful as an animal model for human hematopoietic diseases, the complete reconstruction of human hematopoietic cells can not be established even in these mice. This appears to be because human cytokines, adhesion molecules and extracellular matrices which support differentiation and growth of human hematopoietic cells differ from those in animals. To improve this animal model, we attempted to produce transgenic (Tg) mice producing human interleukin 3 (hIL-3) and human granulocyte macrophage colony stimulating factor (hGM-CSF) with the homozygote of the scid gene. We established two Tg mouse lines, one releasing both 0.5-1 ng/ml of hIL-3 and 0.05-0.2 ng/ml of hGM-CSF in their sera and another releasing only high (2-10 ng/ml) levels of hGM-CSF. When human cytokine-dependent myeloid cell line, TF-1, was subcutaneously transplanted into these two Tg-SCID mouse lines, TF-1 could be successfully engrafted and grew in all lines of Tg-SCID mice but not in control mice. We also observed that TF-1 grows in GM-CSF Tg-SCID mice in a dose dependent manner in vivo and IL-3 shows an additive effect on its growth. These results indicated that these Tg-SCID mice were an useful in vivo model for investigating human leukemogenesis, especially the role of IL-3 and GM-CSF in leukemogenesis.

Animals↗

Outer membrane protein-specific monoclonal antibodies protect SCID mice from fatal infection by the obligate intracellular bacterial pathogen Ehrlichia chaffeensis.

Previous studies of Ehrlichia chaffeensis infection in the mouse have demonstrated that passive transfer of polyclonal Abs from resistant immunocompetent mice to susceptible SCID mice ameliorated infection and disease, even when Abs were administered during established infection. To identify particular Abs that could mediate bacterial clearance in vivo, E. chaffeensis-specific mAbs were generated and administered to infected SCID mice. Bacterial infection in the livers was significantly lowered after administration of either of two Abs of different isotypes (IgG2a and IgG3). Moreover, repeated administration of one Ab (Ec56.5; IgG2a) rescued mice from an otherwise lethal infection for at least 5 wk. Both protective Abs recognized the E. chaffeensis major outer membrane protein (OMP)-1g. Further studies revealed that both Abs recognized closely related epitopes within the amino terminus of the first hypervariable region of OMP-1g. Analyses of human sera showed that E. chaffeensis-infected patients also generated serological responses to OMP-1g hypervariable region 1, indicating that humans and mice recognize identical or closely related epitopes. These studies demonstrate that OMP-specific mAbs can mediate bacterial elimination in SCID mice, and indicate that Abs, in the absence of cell-mediated immunity, can play a significant role in host defense during infection by this obligate intracellular bacterium.

Amino Acid Sequence↗

Introduction of Pneumocystis carinii in a colony of SCID mice.

Pneumocystis carinii-free SCID mice were housed closely exposed to corticosteroid-treated non-SCID mice in a conventional area of our laboratory animal facilities. A one-day exposure was sufficient for P. carinii transmission. The lung infection increased thereafter. Irradiation or splenectomy of SCID mice at the beginning of the exposure resulted in a marked increase of parasite multiplication. Extrapulmonary foci of pneumocystosis were detected in heart and spleen of SCID mice infected by P. carinii via air transmission.

Animals↗

Immune deficiency in SCID mice.

Since the discovery of SCID mice in 1983, numerous studies utilizing these mice were carried out. These investigations can be classified into two major groups. First, the analysis of the immune defect has revealed defective V(D)J recombination and defective DNA double-strand break repair, and has lead to the identification of the candidate gene for SCID mice. Second, the use of SCID mice to explore ways to introduce a murine or xenogeneic immune system into SCID mice by taking advantage of the immune deficiency of the mice has provided an animal model to examine the in vivo function of transferred human or murine immune cells. In this review, we summarize the recent advances made in these two areas of SCID mouse research.

Animals↗

Analysis of candidate human blood stem cells in "humanized" immune-deficiency SCID mice.

Immune deficient SCID mice support the hematopoietic development of surgically implanted human fetal thymus and bone. The usability of the resulting SCID-hu hematolymphoid chimaera as an assay system for human candidate blood stem cells was suggested by the observation that allogeneic CD34+ cells sorted from fetal liver and bone marrow can engraft and differentiate in the transplanted human thymus and bone marrow. The SCID-hu mouse has been further used, in combination with a mouse bone marrow stromal cell line that supports human myeloid and B lymphoid differentiation in vitro, to identify a minor subset of fetal CD34-expressing cells that exhibit multilineage hematopoietic potentialities.

Animals↗

Bcl-2 expression promotes B- but not T-lymphoid development in scid mice.

Expression of antigen receptors is vital for the development of B and T lymphocytes. In mice with the scid mutation, which are unable to make productive rearrangements of their immunoglobulin and T-cell receptor (TCR) genes, lymphopoiesis aborts at an early stage. The death of the immature lymphocytes by apoptosis is postulated to result from a failure to receive a survival signal induced by receptor engagement. Consistent with this hypothesis, introduction of immunoglobulin or TCR transgenes into scid mice promoted an increase in B- or T-lymphoid cells, respectively. As the protein encoded by the bcl-2 gene can inhibit cell death, we tested whether lymphopoiesis could be rescued in scid mice by crossing in a bcl-2 transgene. Strikingly, the bcl-2/scid mice accumulated almost normal numbers of B-lymphoid cells which lacked surface immunoglobulin but expressed markers of maturity. T-cell development remained blocked. Introducing a TCR transgene enabled bcl-2/scid mice to develop normal numbers of CD4+8+ thymocytes even in the absence of immunological selection, suggesting that T cells become competent to respond to bcl-2 protein only after the TCR complex is displayed at the cell surface.

Animals↗

Splenic T helper cell type 1 cytokine profile and extramedullary haematopoiesis in severe combined immunodeficient (scid) mice with inflammatory bowel disease (IBD).

Scid mice develop a severe, chronic, and lethal IBD 3-6 months after engraftment of gut wall from immunocompetent congenic donors, induced by donor-derived CD4+ T cells migrating from the graft. We have investigated intracellular T-helper type 1 (Th1) cytokines in the spleens of gut wall-transplanted scid mice with IBD. Increased fractions of interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and IL-2-positive CD4+ T cells were found in the spleens of diseased mice compared with control mice. Moreover, a small but significant population of CD4+ T cells which stained positive for granulocyte-macrophage colony-stimulating factor (GM-CSF) was found in scid mice with IBD but was virtually absent in congenic non-scid control mice. Cloning of granulocyte/ macrophage colony-forming cells (G/M-CFC) revealed that both non-transplanted scid mice and scid mice with IBD had an 8-14-fold increase in splenic G/M-CFC compared with control mice. No significant difference in the number of G/M-CFC per total spleen was found between non-transplanted and disease scid mice, although both groups of mice showed a nearly two-fold increase compared with control mice. G/M-CFC were never found in the thymus, liver or lymph nodes of diseased mice. Immunohistochemistry revealed that the multinucleated giant cells observed in the gut wall of diseased mice did not represent haematopoietic foci, but were derived from macrophages. These observations point towards a dominant role for Th1-type CD4+ T cells in the immunopathogenesis of IBD, whereas haematopoiesis does not seem to be affected by the development of the disease.

Animals↗

Proliferation and apoptosis of lamina propria CD4+ T cells from scid mice with inflammatory bowel disease.

Scid mice transplanted with low numbers of syngeneic CD4+ T cells, develop a chronic and lethal inflammatory bowel disease (IBD) within 4-6 months. We have used in vivo 5-bromo2-deoxy-uridine (BrdU) labeling to assess the proliferation of lamina propria-derived CD4+ T cells in diseased scid mice. The hourly rate of renewal of colonic lamina propria CD4+ T cells in diseased mice was 7% compared with 1.5% in normal BALB/c control mice. Transplantation of scid mice with in vitro activated CD4+ T cells accelerated the disease onset and development in a cell dose-dependent fashion when compared with non-activated CD4+ T cells. In pulse-chase experiments it was shown that BrdU-labeled cells disappeared rapidly from the lamina propria of diseased mice. DNA analysis revealed that this was due to the presence of nearly four times as many apoptotic CD4+ T cells in diseased than in control mice. Further analyses showed that the apoptotic lamina propria CD4+ T cells were derived from cells having entered the cell cycle within the previous 8 h. These data clearly demonstrate that vigorous CD4+ T cell proliferation and death are involved throughout the course of IBD.

Animals↗

Enteroviral and immune mediated myocarditis in SCID mice.

Severe combined immune deficiency (SCID) mice have been used as an animal model to study both the direct cytopathic effect of enteroviruses on the heart in the absence of an effective immune system and to investigate the role of immune mediated processes in the pathogenesis of human myocarditis. The infection of SCID mice with coxsackievirus B3 resulted in severe myocarditis with very high titers of the virus in the myocardium and severe necrosis of myocytes. This direct cytopathic effect caused an impairment of the myocardial function and resulted in a high mortality rate of the infected animals. For the study of the immune mechanisms in human myocarditis, peripheral blood leukocytes of patients with myocarditis, having an impaired left ventricular function without viral persistence in the myocardium, were transferred into SCID mice. As controls peripheral blood leukocytes of normal donors were used. At 60 days after transfer, human immunoglobulines could be demonstrated in the peripheral blood of the SCID mice, however, human autoantibodies against the adenine nucleotide translocator, a myocardial autoantigen, were only present in the animals receiving peripheral blood leukocytes from patients with myocarditis. Cellular infiltrates of human leukocytes in the myocardium and an impaired left ventricular function were also only observed in animals reconstituted with peripheral blood leukocytes from patients. These effects were T cell dependent as shown by differential transfer. These results are of interest for the treatment of human myocarditis, suggesting the avoidance of an immunosuppressive therapy in acute or chronic myocarditis with viral persistence to prevent a direct cytopathic effect in the absence of an effective immune system. However, in the setting of a chronic, (auto-)immunological myocarditis with the proven absence of entero- or adenoviral sequences an immunomodulatory therapy seems to be effective and safe.

Animals↗

Immune responses to Cryptosporidium muris and Cryptosporidium parvum in adult immunocompetent or immunocompromised (nude and SCID) mice.

Adult murine models of Cryptosporidium infection involving Cryptosporidium muris and C. parvum were used to study immunity to cryptosporidiosis in the mammalian host. Immunocompetent BALB/c or C57BL/6 mice developed a highly patent infection with the RN 66 strain of C. muris but overcame the infection and were immune to reinfection. In contrast, severe combined immunodeficiency (SCID) mice or nude mice had a chronic infection lasting at least 109 days. The development of the C. muris infection appeared to be confined to the gastric epithelium in immunocompetent and immunocompromised mice. SCID mice injected intraperitoneally with histocompatible spleen or mesenteric lymph node cells from uninfected BALB/c mice were able to recover from the C. muris infection. The protective effect of donor spleen cells was not reduced by depletion of the B cell population but was significantly reduced by depletion of Thy.1 cells. Treatment of C57BL/6 or BALB/c mice during infection with a gamma interferon-neutralizing monoclonal antibody, but not a tumor necrosis factor-neutralizing monoclonal antibody, resulted in a significant increase in oocyst production. In the C. parvum model, a severe and eventually fatal chronic infection with a cervine isolate was established in SCID mice, with parasitization occurring in the ileum, cecum, and colon. SCID mice injected with unprimed BALB/c spleen cells prior to inoculation of C. parvum oocysts were resistant to infection. These results suggested that the two animal models should be valuable in the study of immunity to cryptosporidial infection.

Animals↗