Treatment of severe combined immunodeficiency mice with anti-murine granulocyte monoclonal antibody improves human leukocyte xenotransplantation

In vivo antiaging effects of alkaline water supplementation

Telomeres length and telomerase activity are currently considered aging molecular stigmata. Water is a major requirement for our body and water should be alkaline. Recent reports have shown that aging is related to a reduced water intake. We wanted to investigate the effect of the daily intake of alkaline water on the molecular hallmark of aging and the anti-oxidant response. We watered a mouse model of aging with or without alkaline supplementation. After 10 months, we obtained the blood, the bone marrow and the ovaries from both groups. In the blood, we measured the levels of ROS, SOD-1, GSH, and the telomerase activity and analysed the bone marrow and the ovaries for the telomeres length. We found reduced ROS levels and increased SOD-1, GSH, telomerase activity and telomeres length in alkaline supplemented mice. We show here that watering by using alkaline water supplementation highly improves aging at the molecular level.

Beneficial Effects of Fermented Papaya Preparation (FPP®) Supplementation on Redox Balance and Aging in a Mouse Model

In recent decades much attention has been paid to how dietary antioxidants may positively affect the human health, including the beneficial effects of fermented foods and beverages. Fermented Papaya Preparation (FPP^®) has been shown to represent a valuable approach to obtain systemic antioxidants effect. In this study, we wanted to verify whether FPP^® had a clear and scientifically supported in vivo anti-aging effect together with the induction of a systemic antioxidant reaction. To this purpose we daily treated a mouse model suitable for aging studies (C57BL/6J) with FPP^®-supplemented water from either the 6th weeks (early treatment) or the 51th weeks (late treatment) of age as compared to mice receiving only tap water. After 10 months of FPP^® treatment, we evaluated the telomerase activity, antioxidants and Reactive Oxygen Species ROS plasmatic levels and the telomeres length in the bone marrow and ovaries in both mice groups. The results showed that the daily FPP^® assumption induced increase in telomeres length in bone marrow and ovary, together with an increase in the plasmatic levels of telomerase activity, and antioxidant levels, with a decrease of ROS. Early treatment resulted to be more effective, suggesting a potential key role of FPP^® in preventing the age-related molecular damages.

Analysis of innate defences against Plasmodium falciparum in immunodeficient mice

BACKGROUND

Mice with genetic deficiencies in adaptive immunity are used for the grafting of human cells or pathogens, to study human diseases, however, the innate immune responses to xenografts in these mice has received little attention. Using the NOD/SCID Plasmodium falciparum mouse model an analysis of innate defences responsible for the substantial control of P. falciparum which remains in such mice, was performed.

METHODS

NOD/SCID mice undergoing an immunomodulatory protocol that includes, clodronate-loaded liposomes to deplete macrophages and an anti-polymorphonuclear leukocytes antibody, were grafted with human red blood cells and P. falciparum. The systematic and kinetic analysis of the remaining innate immune responses included the number and phenotype of peripheral blood leukocytes as well as inflammatory cytokines/chemokines released in periphery. The innate responses towards the murine parasite Plasmodium yoelii were used as a control.

RESULTS

Results show that 1) P. falciparum induces a strong inflammation characterized by an increase in circulating leukocytes and the release of inflammatory cytokines; 2) in contrast, the rodent parasite P. yoelii, induces a far more moderate inflammation; 3) human red blood cells and the anti-inflammatory agents employed induce low-grade inflammation; and 4) macrophages seem to bear the most critical function in controlling P. falciparum survival in those mice, whereas polymorphonuclear and NK cells have only a minor role.

CONCLUSIONS

Despite the use of an immunomodulatory treatment, immunodeficient NOD/SCID mice are still able to mount substantial innate responses that seem to be correlated with parasite clearance. Those results bring new insights on the ability of innate immunity from immunodeficient mice to control xenografts of cells of human origin and human pathogens.

NOD-scid IL2rgamma(null) mouse model of human skin transplantation and allograft rejection

BACKGROUND

Transplantation of human skin on immunodeficient mice that support engraftment with functional human immune systems would be an invaluable tool for investigating mechanisms involved in wound healing and transplantation. Nonobese diabetic (NOD)-scid interleukin-2 gamma chain receptor (NSG) readily engraft with human immune systems, but human skin graft integrity is poor. In contrast, human skin graft integrity is excellent on CB17-scid bg (SCID.bg) mice, but they engraft poorly with human immune systems.

METHODS

Human skin grafts transplanted onto immunodeficient NSG, SCID.bg, and other immunodeficient strains were evaluated for graft integrity, preservation of graft endothelium, and their ability to be rejected after engraftment of allogeneic peripheral blood mononuclear cells.

RESULTS

Human skin transplanted onto NSG mice develops an inflammatory infiltrate, consisting predominately of host Gr1(+) cells, that is detrimental to the survival of human endothelium in the graft. Treatment of graft recipients with anti-Gr1 antibody reduces this cellular infiltrate, preserves graft endothelium, and promotes wound healing, tissue development, and graft remodeling. Excellent graft integrity of the transplanted skin includes multilayered stratified human epidermis, well-developed human vasculature, human fibroblasts, and passenger leukocytes. Injection of unfractionated, CD4 or CD8 allogeneic human peripheral blood mononuclear cell induces a rapid destruction of the transplanted skin graft.

CONCLUSIONS

NSG mice treated with anti-Gr1 antibody provide a model optimized for both human skin graft integrity and engraftment of a functional human immune system. This model provides the opportunity to investigate mechanisms orchestrating inflammation, wound healing, revascularization, tissue remodeling, and allograft rejection and can provide guidance for improving outcomes after clinical transplantation.

Mouse models with human immunity and their application in biomedical research

Biomedical research in human beings is largely restricted to in vitro studies that lack complexity of a living organism. To overcome this limitation, humanized mouse models are developed based on immunodeficient characteristics of severe combined immunodeficiency (SCID) or recombination activating gene (Rag)(null) mice, which can accept xenografts. Peripheral constitution of human immunity in SCID or Rag(null) mice has been achieved by transplantation of mature human immune cells, foetal human thymus, bone marrow, liver tissues, lymph nodes or a combination of these, although efficiency needs to be improved. These mouse models with constituted human immunity (defined as humanized mice in the present text) have been widely used to investigate the basic principles of human immunobiology as well as complex pathomechanisms and potential therapies of human diseases. Here, elements of an ideal humanized mouse model are highlighted including genetic and non-genetic modification of recipient mice, transplantation strategies and proposals to improve engraftments. The applications of the humanized mice to study the development and response of human immune cells, human autoimmune diseases, virus infections, transplantation biology and tumour biology are reviewed as well.

Humanized SCID mouse models for biomedical research

There is a growing need for effective animal models to carry out experimental studies on human hematopoietic and immune systems without putting individuals at risk. Progress in development of small animal models for the in vivo investigation of human hematopoiesis and immunity has seen three major breakthroughs over the last three decades. First, CB 17-Prkdc(scid) (abbreviated CB 17-scid) mice were discovered in 1983, and engraftment of these mice with human fetal tissues (SCID-Hu model) and peripheral blood mononuclear cells (Hu-PBL-SCID model) was reported in 1988. Second, NOD-scid mice were developed and their enhanced ability to engraft with human hematolymphoid tissues as compared with CB17-scid mice was reported in 1995. NOD-scid mice have been the "gold standard" for studies of human hematolymphoid engraftment in small animal models over the last 10 years. Third, immunodeficient mice bearing a targeted mutation in the IL-2 receptor common gamma chain (IL2rgamma(null)) were developed independently by four groups between 2002 and 2005, and a major increase in the engraftment and function of human hematolymphoid cells as compared with NOD-scid mice has been reported. These new strains of immunodeficient IL2rgamma(null) mice are now being used for studies in human hematopoiesis, innate and adaptive immunity, autoimmunity, infectious diseases, cancer biology, and regenerative medicine. In this chapter, we discuss the current state of development of these strains of mice, the remaining deficiencies, and how approaches used to increase the engraftment and function of human hematolymphoid cells in CB 17-scid mice and in previous models based on NOD-scid mice may enhance human hematolymphoid engraftment and function in NOD-scid IL2rgamma(null) mice.

Reconstitution of a human immune system in immunodeficient mice: models of human alloreaction in vivo

Rodents have been widely used for studies in transplantation immunology because of their short reproduction period and the relative ease of generating inbred mutant or transgenic strains. However, although many biological mechanisms are similar between rodents and humans, several features clearly distinguish the immune system in these species. Consequently, it is rarely possible to extrapolate observations from rodent models directly into clinical practice. In vitro studies with human cells are useful for elucidation of basic mechanisms, but in order to study complex biological phenomena, in vivo studies are indispensable. In later years, a number of interesting models have been described where immunodeficient mice have been reconstituted with human cells, so-called humanized mice, in order to study human immune responses in vivo. This has opened a new field of experimental immunology that has been applied to areas such as cancer, autoimmunity, allergy, infections, and transplantation biology. In this review, we shall concentrate on the use of severe combined immunodeficient mice reconstituted with human immune or stem cells for studies of human alloreaction in vivo.

Regulation of human short-term repopulating cell (STRC) engraftment in NOD/SCID mice by host CD122+ cells

OBJECTIVE

NOD/SCID and NOD/SCID B2m(null) mice are used for the in vivo study of human hematopoietic stem cells (HSC). A previously unrecognized HSC in cord blood, termed short-term repopulating cell (STRC), has been identified using NOD/SCID B2m(null) mice. However, only low levels of STRC engraft in NOD/SCID mice, presumably due to their higher levels of NK cell activity. The objective of these studies was to deplete NK cells both by genetic manipulation of the hosts and by antibody depletion of cell populations that may regulate engraftment with human STRC.

METHODS

C57BL/6-SCID mice and immunodeficient NOD mice genetically deleted in NK cell activity were injected intravenously with human cord blood cells to quantify STRC engraftment. Cohorts of these mice were also treated with anti-NK1.1 or anti-CD122 (IL-2r beta-chain) antibodies.

RESULTS

Human STRC fail to engraft in C57BL/6-SCID mice treated with anti-NK1.1 or with anti-CD122 antibody that targets mouse NK and myeloid cells. NOD/SCID mice, NOD-Rag1(null) mice, and NOD-Rag1(null)Pfp(null) mice that are genetically deleted in NK cell cytotoxic activity support only low levels of STRC engraftment. In contrast, STRC engraft at high levels in all three strains of immunodeficient NOD mice treated with anti-CD122 antibody.

CONCLUSION

Injection of anti-CD122 antibody leads to high levels of STRC engraftment in immunodeficient NOD mice, but not in C57BL/6-SCID mice. These data document that depletion of NK cells is required, and that additional murine host innate immune factors, presumably myeloid cells, are important in regulating human STRC engraftment.

Patterns of engraftment in different strains of immunodeficient mice reconstituted with human peripheral blood lymphocytes

BACKGROUND

Models of immunodeficient mice reconstituted with a competent human immune system would represent an invaluable tool for the study of transplantation immunobiology allergy, autoimmunity, and infectious diseases. Severe combined immune deficiency (scid) mice can be successfully reconstituted with human peripheral blood lymphocytes (PBLs), but rates and levels of engraftment are poor. New strains of mice with diverse immunodeficiencies have been recently characterized or developed, which might prove to be advantageous for in vivo studies of human immune reactivity.

METHODS

We have compared rates and patterns of human PBL engraftment in four available immunodeficient murine strains; scid-beige, nonobese diabetic (NOD)-scid, NOD-scid-beta2 m- and rag-. T- and B-lymphocyte engraftment, phenotype of engrafted cells, and occurrence of graft-versus-host disease (GVHD) were studied and compared.

RESULTS

Successful engraftment of human PBL was readily obtained in the majority of scid-beige, NOD-scid, and NOD-scid-beta2 m- with a single i.p. administration of human PBLs, whereas it was seldom achieved in rag- animals. Human Ig levels were accordingly remarkably low in rag- recipients but, interestingly also in NOD-scid-beta2 m- mice. Engraftment was readily observed not only in peripheral blood but also in spleen and bone marrow of successfully reconstituted animals. Phenotypic analysis of engrafted human cells showed preserved CD4/CD8 ratios and a clear skewing toward an activated phenotype. GVHD was invariably observed in successfully reconstituted animals.

CONCLUSIONS

Our data indicate that a high rate of reconstitution with human lymphocytes can be achieved in scid-beige, NOD-scid, and NOD-scid-beta2 m- mice. Human Ig are produced at high levels, except in NOD-scid-beta2 m-, including xenoreactive natural antibodies. Scid-beige and NOD-scid appear therefore better suited than NOD-scid-beta2 m- or rag- for analysis of human immunoreactivity in vivo. An important caveat is the invariable occurrence of GVHD that precludes long-term studies in this model system.

Human peripheral blood lymphocyte severe combined immunodeficiency (hu-PBL SCID) models of toxoplasmosis

Toxoplasmosis is a potentially fatal opportunistic infection of immunocompromised hosts. Improved animal models of toxoplasmosis are needed to more nearly approximate conditions that occur in immunocompromised humans. The development of models of toxoplasmosis using human peripheral blood lymphocytes (hu-PBL) transplanted into severe combined immunodeficiency (SCID) mice is described here. Transplantation of hu-PBL into SCID mice without prior conditioning of the mice resulted in detectable differences in quantitative histological scores of brain inflammation due to Toxoplasma gondii infection, but did not alter mortality when compared to SCID mouse controls. The lack of detectable differences in survival were due to inadequate engraftment of hu-PBL, as assessed by flow cytometry. Unconditioned hu-PBL SCID mice had low titre T. gondii-specific antibody detectable after infection. When pretransplantation conditioning with irradiation and antiasialo GM 1 (n-glucolyl neuraminic acid) antibody was used, prolonged hu-PBL engraftment was observed in SCID mice, which was associated with worsened histopathology and usually impaired survival when compared with SCID mouse controls. When pretransplantation conditioning with irradiation, antiasialo GM antibody and polyethylene glycol-conjugated IL-2 was used, prolonged hu-PBL engraftment was also documented, but this did not affect survival from T. gondii infection when compared with similarly conditioned SCID mouse controls. The latter conditioning protocol resulted in hu-PBL SCID mice producing high titre T. gondii-specific antibody after infection. Conditioned hu-PBL SCID mice had evidence of increased T. gondii-induced inflammatory scores when compared with conditioned SCID mice. These models show promise for the study of the pathogenesis of toxoplasmosis and conditioned hu-PBL SCID mice may have applications for the evaluation of novel therapies for toxoplasmosis in immunocompromised humans.

Murine granulocytes control human tumor growth in SCID mice

Severe combined immunodeficient (SCID) mice generally do not reject allogeneic or xenogeneic organ grafts and represent a unique model for investigating in vivo the behaviour of both normal and neoplastic human cells. However, cells from human primary tumors often do not grow in SCID mice. We have previously shown that the major reaction of SCID mice to the engraftment of human peripheral blood leukocytes is a massive granulocyte recruitment into the site of transplantation. In this study, we have investigated the role of murine granulocytes in the control of human tumor cell growth in SCID mice. We report here that murine granulocytes infiltrate and delimit the human tumor mass and that treatment of SCID mice with anti-murine granulocyte antibody markedly improves the growth of human tumor cell lines of different origin through suppression of the host granulocyte reaction. This finding provides a new tool for improving the human tumor take in SCID mice, thus opening new perspectives for a practical in vivo preclinical test of anti-tumor strategies. Moreover, this study, even with the limits of the known natural reaction against xenotransplants, further supports the importance of granulocytes in the control of tumor take and growth.

Primary HIV-1 infection of human CD4+ T cells passaged into SCID mice leads to selection of chronically infected cells through a massive fas-mediated autocrine suicide of uninfected cells

We have recently shown that a human CD4+ T cell line (CEM-SS) acquires the permissiveness to M-tropic strains and primary isolates of HIV-1 after transplantation into SCID mice. This permissiveness was associated with the acquisition of a memory (CD45RO+) phenotype as well as of a functional CCR5 coreceptor. In this study, we have used this model for invest-igating in vivo the relationships between HIV-1 infection, apoptosis and T cell differentiation. When an in vivo HIV-1 infection was performed, the CEM cell tumors grew to a lower extent than the uninfected controls. CEM cells explanted from uninfected SCID mice (ex vivo CEM) underwent a significant level of spontaneous apoptosis and proved to be CD45RO+, Fas+ and Fas-L+, while Bcl-2 expression was significantly reduced as compared to the parental cells. Acute HIV-1 infection markedly increased apoptosis of uninfected ex vivo CEM cells, through a Fas/Fas-L-mediated autocrine suicide/fratricide, while parental cells did not undergo apoptosis following viral infection. The susceptibility to apoptosis of ex vivo CEM cells infected with the NSI strain of HIV-1, was progressively lost during culture, in parallel with the loss of Fas-L and marked changes in the Bcl-2 cellular distribution. On the whole, these results are strongly reminiscent of a series of events possibly occurring during HIV-1 infection. After an initial depletion of bystander CD4+ memory T cells during acute infection, latently or chronically infected CD4+ T lymphocytes are progressively selected and are protected against spontaneous apoptosis through the development of an efficient survival program. Studies with human cells passaged into SCID mice may offer new opportunities for an in vivo investigation of the mechanisms involved in HIV-1 infection and CD4+ T cell depletion.

Type I interferon is a powerful inhibitor of in vivo HIV-1 infection and preserves human CD4(+) T cells from virus-induced depletion in SCID mice transplanted with human cells

Although several studies are available on the in vitro inhibitory activities of type I interferon (IFN) on HIV-1 replication, the role of these cytokines in the pathogenesis of AIDS is still matter of conjecture. Both beneficial and adverse effects have been envisaged and considered as a possible rationale for the development of either IFN or anti-IFN therapies in HIV-1-infected patients. In the present study, we have evaluated the efficacy of human type I IFN on HIV-1 infection and virus-induced depletion of human CD4 T cells in two models established in SCID mice. In SCID mice transplanted with human U937 cells (U937-SCID mouse model), continuous treatment with type I consensus IFN (CIFN) resulted in a total suppression of HIV-1 infection. This inhibitory effect was superior to that obtained after AZT treatments. Results from an ensemble of experiments in SCID mice transplanted with either control or genetically modified human U937 cells transduced with a Tat-inducible IFN-alpha gene (LTR-IFN-A2 U937) indicated that low levels of IFN-alpha, produced locally as a result of virus infection, were extremely effective in inhibiting acute HIV infection and virus replication. Of interest, LTR-IFN-A2 U937 cells conferred a strong anti-HIV-1 protection to coinjected bystander U937 cells. Notably, experiments with SCID mice reconstituted with human PBL (hu-PBL-SCID mouse model) showed that treatment with CIFN inhibited HIV-1 replication more effectively than AZT treatment. Remarkably, treatment with CIFN resulted in a clear-cut protection from the virus-induced depletion of human CD4 T cells, which was also associated with the generation of an antibody response toward HIV-1 antigens in 50% of the virus-injected xenografts. These results suggest that type I IFN efficiently preserves human CD4(+) cells from virus-induced damage in hu-PBL-SCID mice, not only by inducing an antiviral state in target cells but also by stimulating anti-HIV-1 human immune responses in vivo.

Human lymphoblastoid CD4(+) T cells become permissive to macrophage-tropic strains of human immunodeficiency virus type 1 after passage into severe combined immunodeficient mice through in vivo upregulation of CCR5: in vivo dynamics of CD4(+) T-cell differentiation in pathogenesis of AIDS

In this article, we show that passage in SCID mice rendered a human CD4(+) T-cell line (CEM cells) highly susceptible to infection by macrophage-tropic (M-tropic) strains and primary clinical isolates of human immunodeficiency virus type 1 (HIV-1). This in vivo-acquired permissiveness of CEM cells was associated with the induction of a CD45RO+ phenotype as well as of some beta-chemokine receptors. Regulated upon activation, normal T-cell expressed and secreted chemokine entirely inhibited the ability of M-tropic HIV-1 strains to infect these cells. These findings may lead to new approaches in investigating in vivo the capacity of different HIV strains to exploit chemokine receptors in relation to the dynamics of the activation and/or differentiation state of human CD4(+) T cells.