Targeting ABL1 or ARG Tyrosine Kinases to Restrict HIV-1 Infection in Primary CD4+ T-Cells or in Humanized NSG Mice.

BACKGROUND: Previous studies support dasatinib as a potent inhibitor of HIV-1 replication. However, a functional distinction between 2 kinase targets of the drug, ABL1 and ARG, has not been assessed. SETTING: We used primary CD4 T-cells, CD8-depleted peripheral blood mononuclear cells (PBMCs) from a treatment naïve HIV-1 patient, and a humanized mouse model of HIV-1 infection. We assessed the roles of ABL1 and ARG during HIV-1 infection and use of dasatinib as a potential antiviral against HIV-1 in humanized mice. METHODS: Primary CD4 T-cells were administered siRNA targeting ABL1 or ARG, then infected with HIV-1 containing luciferase reporter viruses. Quantitative polymerase chain reaction of viral integration of 4 HIV-1 strains was also assessed. CD8-depleted PBMCs were treated for 3 weeks with dasatinib. NSG mice were engrafted with CD34 pluripotent stem cells from human fetal cord blood, and infected with Ba-L virus after 19 weeks. Mice were treated daily with dasatinib starting 5 weeks after infection. RESULTS: siRNA knockdown of ABL1 or ARG had no effect on viral reverse transcripts, but increased 2-LTR circles 2- to 4-fold and reduced viral integration 2- to 12-fold. siRNA knockdown of ARG increased SAMHD1 activation, whereas knockdown of either kinase reduced RNA polymerase II activation. Treating CD8-depleted PBMCs from a treatment-naïve patient with 50 nM of dasatinib for 3 weeks reduced p24 levels by 99.8%. Ba-L (R5)-infected mice injected daily with dasatinib showed a 95.1% reduction in plasma viral load after 2 weeks of treatment. CONCLUSIONS: We demonstrate a novel nuclear role for ABL1 and ARG in ex vivo infection experiments, and proof-of-principle use of dasatinib in a humanized mouse model of HIV-1 infection.

Neisseria gonorrhoeae co-infection exacerbates vaginal HIV shedding without affecting systemic viral loads in human CD34+ engrafted mice.

HIV synergy with sexually transmitted co-infections is well-documented in the clinic. Co-infection with Neisseria gonorrhoeae in particular, increases genital HIV shedding and mucosal transmission. However, no animal model of co-infection currently exists to directly explore this relationship or to bridge the gap in understanding between clinical and in vitro studies of this interaction. This study aims to test the feasibility of using a humanized mouse model to overcome this barrier. Combining recent in vivo modelling advancements in both HIV and gonococcal research, we developed a co-infection model by engrafting immunodeficient NSG mice with human CD34+ hematopoietic stem cells to generate humanized mice that permit both systemic HIV infection and genital N. gonorrhoeae infection. Systemic plasma and vaginal lavage titres of HIV were measured in order to assess the impact of gonococcal challenge on viral plasma titres and genital shedding. Engrafted mice showed human CD45+ leukocyte repopulation in blood and mucosal tissues. Systemic HIV challenge resulted in 104-105 copies/mL of viral RNA in blood by week 4 post-infection, as well as vaginal shedding of virus. Subsequent gonococcal challenge resulted in unchanged plasma HIV levels but higher viral shedding in the genital tract, which reflects published clinical observations. Thus, human CD34+ stem cell-transplanted NSG mice represent an experimentally tractable animal model in which to study HIV shedding during gonococcal co-infection, allowing dissection of molecular and immunological interactions between these pathogens, and providing a platform to assess future therapeutics aimed at reducing HIV transmission.

Control of HIV Infection In Vivo Using Gene Therapy with a Secreted Entry Inhibitor.

HIV entry inhibitors are highly effective in controlling virus replication. We have developed a lentiviral vector that expresses a secreted entry inhibitor, soluble CD4 (sCD4), which binds to the HIV envelope glycoproteins and inactivates the virus. We have shown that sCD4 was secreted from gene-modified CD4+ T cells, as well as from human umbilical cord blood-derived CD34+ hematopoietic stem/progenitor cells (HSPCs), and protected unmodified HIV target cells from infection in vitro. To investigate the in vivo application of our approach, we injected gene-modified HSPCs into NOD/SCID/γcnull (NSG) mice. NSG hosts supported multi-lineage differentiation of human gene-modified HSPCs. Upon challenge with HIV, humanized mice capable of secreting sCD4 demonstrated a reduction of viral load over time compared to control humanized mice. In contrast to gene therapy approaches that render only gene-modified HIV target cells resistant to infection, our approach also showed protection of unmodified CD4+ T cells in the peripheral blood and tissues. Our findings provide support for the continuous delivery of secreted entry inhibitors via gene therapy as an alternative to oral administration of antiretroviral drugs or injection of antiretroviral proteins, including antibodies.

IVIG regulates the survival of human but not mouse neutrophils.

Intravenous immunoglobulin (IVIG) are purified IgG preparations made from the pooled plasma from thousands of healthy donors and are being tested in preclinical mouse models. Inherent challenges, however, are the pluripotency of IVIG and its xenogeneicity in animals. IVIG can alter the viability of human neutrophils via agonistic antibodies to Fas and Siglec-9. In this study, we compared the effects of IVIG on human and mouse neutrophils using different death assays. Different commercial IVIG preparations similarly induced cytokine-dependent death in human neutrophils, whereas they had no effects on the survival of either peripheral blood or bone marrow neutrophils from C57BL/6 or BALB/c mice. F(ab')2 but not Fc fragments of IVIG induced death of human neutrophils, whereas neither of these IVIG fragments, nor agonistic monoclonal antibodies to human Fas or Siglec-9 affected the viability of mouse neutrophils. Pooled mouse IgG, which exhibited a different immunoprofile compared to IVIG, also had no effect on mouse cells. Together, these observations demonstrate that effects of IVIG on neutrophil survival are not adequately reflected in current mouse models, despite the key role of these cells in human inflammatory and autoimmune diseases.

Optimal attenuation of experimental autoimmune encephalomyelitis by intravenous immunoglobulin requires an intact interleukin-11 receptor.

BACKGROUND: Intravenous immunoglobulin (IVIg) has been used to treat a variety of autoimmune disorders including multiple sclerosis (MS); however its mechanism of action remains elusive. Recent work has shown that interleukin-11 (IL-11) mRNAs are upregulated by IVIg in MS patient T cells. Both IVIg and IL-11 have been shown to ameliorate experimental autoimmune encephalomyelitis (EAE), an animal model of MS. The objective of this study was to determine whether the protective effects of IVIg in EAE occur through an IL-11 and IL-11 receptor (IL-11R)-dependent mechanism. METHODS: We measured IL-11 in the circulation of mice and IL-11 mRNA expression in various organs after IVIg treatment. We then followed with EAE studies to test the efficacy of IVIg in wild-type (WT) mice and in mice deficient for the IL-11 receptor (IL-11Rα-/-). Furthermore, we evaluated myelin-specific Th1 and Th17 responses and assessed spinal cord inflammation and demyelination in WT and IL-11Rα-/- mice, with and without IVIg treatment. We also examined the direct effects of mouse recombinant IL-11 on the production of IL-17 by lymph node mononuclear cells. RESULTS: IVIg treatment induced a dramatic surge (>1000-fold increase) in the levels of IL-11 in the circulation and a prominent increase of IL-11 mRNA expression in the liver. Furthermore, we found that IL-11Rα-/- mice, unlike WT mice, although initially protected, were resistant to full protection by IVIg during EAE and developed disease with a similar incidence and severity as control-treated IL-11Rα-/- mice, despite initially showing protection. We observed that Th17 cytokine production by myelin-reactive T cells in the draining lymph nodes was unaffected by IVIg in IL-11Rα-/- mice, yet was downregulated in WT mice. Finally, IL-11 was shown to directly inhibit IL-17 production of lymph node cells in culture. CONCLUSION: These results implicate IL-11 as an important immune effector of IVIg in the prevention of Th17-mediated autoimmune inflammation during EAE.

Cytokine profiles in mouse models of experimental immune thrombocytopenia reveal a lack of inflammation and differences in response to intravenous immunoglobulin depending on the mouse strain.

BACKGROUND: Mouse models of human immune thrombocytopenia (ITP) have been used for years to investigate the mechanism of intravenous immunoglobulin (IVIG) to ameliorate ITP; however, how closely these experimental mouse models mirror the human autoimmune inflammatory disease is unclear. The aim of this study was to assess the cytokine profiles in experimental ITP with and without IVIG treatment. STUDY DESIGN AND METHODS: We examined the production of 23 cytokines that included pro- and anti-inflammatory cytokines, in two different mouse strain models of ITP, BALB/c and C57BL/6J, with and without IVIG treatment. RESULTS: In contrast to human ITP, in mouse models of ITP generated by passive transfer of an alloantibody we find no evidence of inflammatory disease even when ITP is robust, suggesting that while these models capture the innate response phase of the disease, they may not be capturing the adaptive mechanisms of autoimmune initiation of the disorder. Regardless of the mouse strain examined, interleukin (IL)-1α, -2, -6, -17, and -23; granulocyte-macrophage-colony-stimulating factor (GM-CSF); monocyte chemoattractant protein (MCP)-1; macrophage inflammatory protein (MIP)-1ß; RANTES; tumor necrosis factor (TNF)-α; and interferon-γ remain at negligible levels after ITP induction. IVIG treatment in the absence of ITP induced significant levels of IL-4, -10, -11, -17, and -23; GM-CSF; MCP-1; and TNF-α in BALB/c mice, but only IL-11 was elevated in C57BL/6J mice. In response to IVIG treatment of ITP, both strains produced IL-4, -10, -11, and -23; GM-CSF; MCP-1; MIP-1ß; and TNF-α; however, only BALB/c exhibited increased MCP-3 and RANTES. IL-11 levels were the highest of any cytokine after IVIG administration, given either alone or as treatment of ITP. CONCLUSIONS: We conclude that mouse models for human ITP do not capture the full range of autoimmune inflammatory mechanisms of this disease. Furthermore, cytokine profiles differ in response to IVIG depending on the mouse strain used.

Therapeutic effect of IVIG on inflammatory arthritis in mice is dependent on the Fc portion and independent of sialylation or basophils.

High-dose i.v. Ig (IVIG) is used to treat various autoimmune and inflammatory diseases; however, the mechanism of action remains unclear. Based on the K/BxN serum transfer arthritis model in mice, IVIG suppression of inflammation has been attributed to a mechanism involving basophils and the binding of highly sialylated IgG Fc to DC-SIGN-expressing myeloid cells. The requirement for sialylation was examined in the collagen Ab-induced arthritis (CAbIA) and K/BxN serum transfer arthritis models in mice. High-dose IVIG (1-2 g/kg body weight) suppressed inflammatory arthritis when given prophylactically. The same doses were also effective in the CAbIA model when given subsequent to disease induction. In this therapeutic CAbIA model, the anti-inflammatory effect of IVIG was dependent on IgG Fc but not F(ab')2 fragments. Removal of sialic acid residues by neuraminidase had no impact on the anti-inflammatory activity of IVIG or Fc fragments. Treatment of mice with basophil-depleting mAbs did not abrogate the suppression of either CAbIA or K/BxN arthritis by IVIG. Our data confirm the therapeutic benefit of IVIG and IgG Fc in Ab-induced arthritis but fail to support the significance of sialylation and basophil involvement in the mechanism of action of IVIG therapy.

Mouse background and IVIG dosage are critical in establishing the role of inhibitory Fcγ receptor for the amelioration of experimental ITP.

A recognized paradigm for the therapeutic action of intravenous immunoglobulin (IVIG) in immune thrombocytopenia (ITP) involves up-regulation of the inhibitory Fcγ receptor (FcγRIIB) in splenic macrophages. However, published data have indicated that opposing results are obtained when using FcγRIIB-deficient mice on different strain backgrounds. Herein we show BALB/c FcγRIIB(-/-) and wild-type, with or without spleens, all recover ITP with similar dynamics after IVIG (1 g/kg) treatment; however, this was not the case for C57BL/6 (B6) FcγRIIB(-/-). In investigating this conundrum, we found that wild-type B6 mice are much less sensitive than BALB/c to IVIG-mediated amelioration of ITP, requiring approximately 2- to 2.5-fold more IVIG than BALB/c. When using 2.5 g/kg IVIG in FcγRIIB(-/-) B6 mice, amelioration of ITP was as in wild-type in all animals. Our findings led us to the conclusion that different strains of mice respond differently to IVIG and that FcγRIIB plays no role in the mechanism of effect of IVIG in experimental ITP.

Sialylation-independent mechanism involved in the amelioration of murine immune thrombocytopenia using intravenous gammaglobulin.

BACKGROUND: Sialylation of the N-linked glycan on asparagine-297 within the Fc region of intravenous gammaglobulins (IVIgs) was shown to be necessary for efficacy of IVIg in the amelioration of experimental inflammatory arthritis. To test the role for Fc sialylation of IVIg in immune modulating therapies beyond the K/BxN arthritis model, we examined the efficacy of sialylated compared to nonsialylated IVIg for the ability to attenuate immune thrombocytopenia (ITP) in a mouse model that approximates the clinical setting of human ITP. STUDY DESIGN AND METHODS: We used a published, passive anti-platelet (PLT) dose-escalation mouse model of ITP that approximates clinical ITP. PLT counts were followed over time before and after IVIg treatment. IVIg from two different manufacturers was used to prepare untreated and neuraminidase-treated IVIg. Sambucus nigra agglutinin (SNA) affinity chromatography was used to obtain sialic acid-enriched and -depleted IVIg. Sialic acid content was determined using Western blot, enzyme-linked immunosorbent assay, and high-performance liquid chromatography. RESULTS: Results were the same using sialylated and desialylated (neuraminidase-treated) IVIg from two different manufacturers. No differences were observed between sialic acid-enriched and -depleted IVIg compared to normal IVIg in their efficacy to alleviate ITP. Using quantitative reverse transcription-polymerase chain reaction, no increase in the spleen FcγRIIB mRNA was detectable, but a pronounced increase of FcγRIIB mRNA in the marrow was seen after IVIg administration. CONCLUSIONS: We conclude that IVIg ameliorates experimental ITP by a mechanism that is independent of sialylation either in the Fc or the Fab region of IVIg.

Improved mouse models for the study of treatment modalities for immune-mediated platelet destruction.

BACKGROUND: We found when using a mouse model of immune thrombocytopenia (ITP) that platelet (PLT) nadir could not be maintained in the face of daily PLT antibody, making interpretation of treatment modalities difficult. This finding was documented to be at least in part due to increased thrombopoiesis as a result of a compensated thrombocytolytic state. Thus, it was important to develop an improved mouse model of human ITP so as to maintain PLT nadir over time. STUDY DESIGN AND METHODS: To maintain PLT nadir, we have developed two mouse models. One model uses single-dose sublethal total body gamma irradiation (TBI) in combination with daily low-dose PLT antibody administration while the second model uses escalation of the dose of PLT antibody over time. Both models maintain PLT nadir and allow for the study of treatment modalities without interference by marrow compensation. RESULTS: Surprisingly, intravenous immune globulin (IVIG) shows no efficacy when using the TBI combination model but works well using the dose-escalation mouse model. In contrast, anti-TER-119 shows efficacy using either mouse model. Our results indicate that the mechanism of action of IVIG requires a functional marrow and/or involves a radiosensitive regulatory cell. However, IVIG works using the dose-escalation model without TBI and the increase in PLT counts correlates directly with reticulated PLTs suggesting that the IVIG mechanism involves effects on megakaryopoiesis/thrombopoiesis. CONCLUSIONS: These mouse models should be useful for investigators wishing to maintain PLT nadir over prolonged periods of time for the study of mechanism and efficacy of various treatments for ITP.