Browsing by Subject "dendritic cells"
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Item Characterization of the effects of Interferon gamma protein-10 (CXCL10) against the protozoan parasite Leishmania amazonesis(2007-06-26) Rene Ernesto Vasquez; Lynn Soong; Thomas K. Hughes; Randall Goldblum; Johnny W. Peterson; David CorryLeishmania amazonensis causes progressive disease in most inbred strains of mice. We have previously shown that L. amazonensis-infected C57BL/6 mice have profound impairments in expression of pro-inflammatory cytokines, chemokines and in activation of antigen-specific CD4+ T cells. These impairments are independent of IL-4. The precise mechanism of pathogenesis associated with L. amazonensis infection remains largely unresolved. Since chemokines are essential mediators of leukocyte recruitment and effector cell function, we hypothesized that these molecules are important for the initiation of early responses locally and the eventual control of the infection. In this study, we found that CXCL10-treated bone marrow-derived macrophages from both BALB/c and C57BL/6 mice showed decreased numbers of L. amazonensis parasites, which was partially due to increased nitric oxide production, as well as elevated production of pro-inflammatory chemokines. When susceptible C57BL/6 mice were locally injected with CXCL10 following L. amazonensis infection, there was a significant delay in lesion development and reduction in parasite burdens, accompanied by a 7- and 3.5-fold increase in IFN-γ and IL-12 secretion, respectively, in re-stimulated lymph node cells. This study confirms that CXCL10 assists in the reduction of intracellular parasites. To address the mechanism underlying this enhanced immunity we utilized stationary promastigotes to infect bone marrow-derived DCs of C57BL/6 mice and assessed the activation of DC subsets and the capacity of these DC subsets in priming CD4+ T cells in vitro. We found that CXCL10 induced IL-12p40, but reduced IL-10 production in DCs. Yet, L. amazonensis-infected DCs produced elevated levels of IL-10, despite CXCL10 treatment. Elimination of endogenous IL-10 led to increased responsiveness to CXCL10 treatment, as judged by increased IL-12 production in DCs, as well as increased proliferation and IFN-γ production by CD4+ T cells. In addition, CXCL10-treated CD4+ T cells became more responsive to IL-12 via increased expression of the IL-12Rβ2 chain and produced elevated IFN-γ. This study indicates the interplay between CXCL10 and IL-10 in the generation of Th1-favored, pro-inflammatory responses and further highlights the utility of CXCL10 as a potential therapeutic for the control of non-healing cutaneous leishmaniasis.Item Effector CD4+ T lymphocyte resolution of acute HSV infection at genital and neuronal sites, and the manipulation of CD4+ T cell responses via TLR ligand-induced proinflammatory cytokine milieus(2010-05-17) Alison Joy Johnson; Gregg N. Milligan; Rolf Konig; Nigel Bourne; Lawrence Stanberry; Janice EndsleyIn primary infection, CD8+ T cells are important for clearance of infectious HSV from sensory ganglia. We present evidence of CD4+ T-cell-mediated clearance of infectious HSV-1 from neural tissues. In immunocompetent mice, HSV-specific CD4+ T cells were present in sensory ganglia and spinal cords coincident with HSV-1 clearance and remained detectable at least 8 months post-infection. Neural CD4+ T cells isolated at the peak of neural infection secreted IFN-ã, TNF-á, IL-2, or IL-4 after stimulation with HSV antigen. HSV-1 titers in neural tissues were greatly reduced over time in CD8+ T-cell-deficient and CD8+ T-cell-depleted mice, suggesting CD4+ T cells could mediate clearance from neural tissue. Clearance of infectious virus from neural tissues was not significantly different in CD8+ T-cell-depleted, perforin-deficient or FasL-defective mice compared to wild-type mice. Virus titers in neural tissues of chimeric mice expressing both perforin and Fas or neither perforin nor Fas were significantly lower than in controls. Thus, perforin and Fas were not required for clearance of infectious virus from neural tissues. These results further define the HSV-specific CD4+ T cell response. To determine the influence of differential TLR activation of DCs in development of appropriate CD4+ T cell phenotype, magnitude, and memory, we established bone marrow-derived DCs that were 92.6% CD11c+CD11b+, and 94.0% CD11c+B220-Ly-6c- in vitro. Ligands for TLR3, -4, or -9 were applied to DCs, and cytokine and chemokine secretion was examined. Particular interest was paid to IL-12 and IFN-g (important for TH1 differentiation thought critical against HSV), and antiviral type I interferons. Proliferation and activation of the CD4+ T cells co-cultured with TLR-ligand-stimulated DCs were assessed. CD4+ T cell magnitude, effector function, and establishment of memory generated upon injection of TLR-ligand-stimulated peptide-pulsed DCs were examined. Stimulation of DCs through TLR3 enhanced CD4+ T cell production of large amounts of TH1-type cytokines and cytolytic molecules. Stimulation of DCs through TLR4 did drive this phenotype, and also enhanced memory CD4+ T cell population formation within the genital tract. A vaccine able to elicit a vigorous, long-lasting CD4+ T cell response may prove important in limiting disease and transmission of virus.Item Parasite interactions with dendritic cells and macrophages: Implications for cutaneous Leishmaniasis caused by Leishmania amazonensis(2003-03-26) Hai Qi; Lynn Soong; Vivian L. Braciale; Rolf Konig; Joseph M. Vinetz; David M. Mosser; Barbara L. DoughtyProtozoan Leishmania is an important human pathogen that affects millions people worldwide. Investigation of experimental Leishmania infection in mice has been instrumental to our understanding of interactions between the parasite and the host immune system. Previous studies have established the model of Th1-Th2 paradigm: gamma interferon (IFN-g)-secreting Th1 cells protect the host from developing progressive diseases, while interleukin (IL)-4-producing Th2 cells drive the disease pathogenesis. Focused on L. amazonensis infection in mice, this dissertation study is mainly intended to understand the cellular mechanism underlying the generation of parasite-specific Th2 cells and to ascertain the role for IFN-g in parasite-macrophage interactions. We showed that L. amazonensis parasites infected and activated dendritic cells (DCs), a population of phagocytic antigen-presenting cells specialized in activating naïve T cells. We found that DCs from susceptible or resistant mice differentially responded to amastigotes in CD40-dependent cytokine production and that amastigote-infected DCs favor Th2 priming in susceptible but not resistant mice. IFN-g is believed to be crucial for activating macrophages to kill intracellular parasites such as L. major. However, we found that L. amazonensis amastigotes but not promastigotes could not only survive but also replicate better in IFN-g-activated macrophages. The promastigote was evidently killed in IFN-g-activated macrophages. On the other hand, macrophages activated with IFN-g and LPS were able to limit intracellular amastigote replication. When tested in vivo, endogenous IFN-g apparently exerted minimal effects on the course of amastigote infection. It is likely that IFN-g plays a bidirectional role during L. amazonensis infection: when optimally coupled with other factors, it can activate macrophages to control parasite infection; while in the absence of such synergy, it would promote amastigote propagation by itself. Collectively, results presented in this dissertation have pointed to the unique ability of L. amazonensis amastigotes to modulate host immune system to the advantage of their own survival.Item The role of dendritic cells in rickettsial infection; initation of early immunity to spotted fever group Rickettsiae(2007-06-26) Jeffrey Michael Jordan; David H. Walker, M.D.; Lynn Soong, Ph.D.; D. Mark Estes, Ph.D.; B. Mark Evers, M.D.; Abul Abbas, MBBSIdentifying the role(s) dendritic cells play in rickettsial infection is important in determining the characteristics which elicit protective immunity. Previous data imply that Th1 responses are essential for immunity to rickettsiae; however, they do not address mechanisms important in initiating early immunity, particularly those involving dendritic cells. Dendritic cells are instrumental in initiation and control of a strong Th1 response towards invading pathogens. I hypothesize that cutaneous dendritic cells comprise an important initial target for rickettsial infection. Additionally, activation and migration of rickettsiae-infected dendritic cells to draining lymph nodes may be critical to activation of NK and CD8 T-cells. Lastly, preliminary data suggest that rickettsiae act as TLR4 agonists on dendritic cells, resulting in their activation. To elucidate the significance of dendritic cells in rickettsioses, I developed a model of dermal infection to demonstrate that cutaneous dendritic cells comprise an important initial target cell. Furthermore, I demonstrated that rickettsiae-infected dendritic cells were capable of inducing protective immunity in naïve mice to an ordinarily lethal challenge. This protection was correlated with significantly elevated levels of IFN-γ producing CD4 and CD8 T-cells as well as NK cells, indicating that rickettsiae-infected dendritic cells are capable of inducing protective Th1 responses and NK cell mobilization. Lastly, we demonstrated that mice defective in TLR4 signaling were more susceptible to lethal rickettsial infection. This susceptibility was correlated with a significant decrease in Th1 immune responses. Additionally, TLR4 was shown to be critical towards the generation of Th17 responses. TLR4 ligation in dendritic cells also appears important in augmenting NK cell activation in vivo.