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2014 Research Showcase
IVCB Abstracts
Abstract Title : Group A Streptococcus M2 Protein Interaction with C4BP and Interference by Hyaluronic Acid Capsule
Abstract : Streptococcus pyogenes, or group A Streptococcus (GAS), is an important human pathogen that contributes to more than half a million deaths annually. GAS pathogenicity is attributed to the expression of many virulence factors, including M protein and a hyaluronic acid capsule, that diminish the host immune response. GAS hyaluronic acid (HA) encapsulation, encoded by the hasABC synthase operon, contributes to host immune response evasion by precisely mimicking the structure of human hyaluronic acid. M proteins are surface-bound molecules that promote GAS colonization through increased epithelial cell adherence and internalization. Some M protein subtypes have been shown to promote resistance to opsonophagocytosis mediated by the binding of C4BP, a human complement-inhibitory protein. AP2 is a GAS isolate that expresses M2 protein, but due to a mutation to the CovR/S regulator, also expresses high levels of HA capsule. Although M2 protein is known to bind C4BP, wild type AP2 showed no C4BP binding, suggesting that AP2 hyper-encapsulation interferes with the interaction between M2 protein and C4BP. To test this hypothesis, the HA capsule was enzymatically cleaved using hyaluronidase, which resulted in increased C4BP binding. Additionally, a mutant strain deficient in capsule expression (AP2hasA) showed enhanced C4BP binding. Together, these data demonstrate an inverse correlation between capsular expression levels and C4BP binding in GAS.
Abstract Title : Investigating the Molecular Regulation of CD100-Induced Dendritic Epidermal γδ T Cell Rounding
Abstract : Dendritic Epidermal T Cells (DETC) are the prototypic dendritic γδ T cell resident in the epidermis. DETCs make multiple contacts with neighboring keratinocytes via dendritic protrusions that monitor for signs of damage, upon which DETCs retract their dendrites, adopt a rounded morphology, and secrete effector molecules?including keratinocyte growth factors?that facilitate wound repair. It has been shown that the DETC CD100 (Semaphorin 4D) receptor interaction with its Plexin B2 ligand on neighboring keratinocytes is required to facilitate DETC rounding in response to keratinocyte damage. However, the molecular regulation of CD100-induced DETC rounding has not been fully defined. Here we demonstrate that the CD100 molecular signaling pathway involves the activation of RhoA-GTPase, a molecular switch involved in both cellular migration and cytoskeletal dynamics. Immunoblot analyses of RhoA-GTPase were performed following stimulation of CD100-expressing CHO cells with CD100 antibody. Our results indicate a rapid and transient RhoA-GTPase activation peaking at five minutes after CD100 antibody addition, followed by a similarly rapid and transient inactivation of RhoA-GTPase beyond the five minute time point. Uniquely, this is the first demonstration of RhoA-GTPase activation via semaphorin signaling. To further investigate the importance of RhoA-GTPase activation, in vivo experiments utilizing RhoA-GTPase inhibitors to block CD100-regulated activation are currently in progress. Additional experiments in the future will be directed towards the analysis of various RhoA-GTPase downstream effectors, including ROCK and LIMK. We anticipate that these experiments will help decipher DETC biology, resulting in an improved understanding of immune defects contributing to chronic, non-healing wounds in patients.
Advisor : MICK CROFT
Abstract Title : Role of TRAIL in NK Cell-Mediated Control of Murine Cytomegalovirus in C57BL/6 Mice
Abstract : Natural Killer (NK) cells play an important role in the early antiviral response to murine cytomegalovirus (MCMV) infection. C57BL/6 (B6) mice mount a strong NK response to CMV as a result of the interaction between MCMV glycoprotein m157 and NK-activating receptor Ly49H, leading to reduced acute viral replication. TNF-related apoptosis inducing ligand (TRAIL) interacts with its death receptors (DR) to promote antiviral defenses through apoptosis regulation. CMV encodes many immune modulatory genes which aid in viral persistence. Our recent work has demonstrated that MCMV m166 protein restricts cell surface expression of TRAIL-DR in infected cells, thus protecting them from TRAIL-mediated apoptosis. An MCMV mutant lacking m166 gene expression is severely attenuated for replication in vivo, especially in the liver of BALB/c mice. In this study we sought to determine the contribution of NK cell TRAIL in early MCMV control in B6 mice. MCMV-m166stop replicates to the same extent as WT MCMV indicating that TRAIL on B6 NK cells plays little to no role in viral control. We verified the presence of four NK cell developmental subsets in the B6 liver that have differential TRAIL surface expression. We show that IFN-I signaling influences constitutive TRAIL expression in na´ve NK subsets. We finally demonstrate that MCMV orf m166 is sufficient for inhibiting TRAIL-DR surface expression. These results indicate that in B6 mice where NK cell responses are very robust, despite the presence of TRAIL on liver NK cells, TRAIL-dependent NK cell mediated apoptosis is not a major contributor to early MCMV control.
Abstract Title : Identification of GM-CSF Target Genes Capable of Reducing Leukemogenic Potential of AML1-ETO Hematopoietic Stem/Progenitor Cells
Abstract : AML1-ETO, the fusion gene generated from chromosomal translocation t(8;21)(q22;q22), is present in approximately 15% of adult Acute Myeloid Leukemia (AML) cases. Though expression of AML1-ETO is associated with increased proliferation and decreased differentiation in hematopoietic stem/progenitor cell (HSPC) populations, additional aberrations are necessary for leukemogenesis. Our lab previously demonstrated that loss of granulocyte-macrophage colony stimulating factor (GM-CSF) signaling in AML1-ETO HSPCs results in leukemia development. This indicates that GM-CSF signaling has a negative effect on t(8;21)-induced leukemogenesis. We hypothesize that this negative effect is dependent on activation of select downstream GM-CSF signaling pathways that diminish self-renewal capacity and promote myeloid differentiation. Current data show that AML1-ETO specifically enhances GM-CSF responsiveness in HSPCs. We employed a barcoded cDNA screening method to characterize this hypersensitivity and identify GM-induced genes that negatively affect AML1-ETO HSPCs. We found that overexpression of MXI1, CXCL1, or LTB4R1 alone is sufficient in negating leukemic phenotypes in vitro. This work contributes deeper understanding of molecular mechanisms underlying t(8;21) leukemogenesis while illuminating therapeutic targets with potential of improving clinical prognoses of Acute Myeloid Leukemia patients.
Abstract Title : Reverse phase protein microarray identifies IL6 receptor ligation induced PI3K/AKT, insulin receptor, and JAK/STAT signaling pathways in the CARD11 mutated lymphoma cell line OCI-Ly3
Abstract : A subset of diffuse large B cell lymphoma of the activated B cell subtype bear mutations that drive B cell antigen receptor (BCR) independent chronic activation of NFkB. The consequence appears to be loss of dependency for survival on BCR proximal kinases (BTK, SYK) and the initiation of a cytokine autocrine stimulation loop conferring an alternate survival mechanism. In the OCILy3 cell line, for example, IL6 is produced de novo as a consequence of NFkB gene transcription, and both neutralizing anti-IL6 antibody and small molecule JAK inhibition affects cell survival. The exact nature of this survival mechanism, however, is unclear. The goal of our studies was to more clearly define the molecular events induced by IL6 stimulation that promote survival in OCILy3 DLBCL.
Abstract Title : Role of Intelukin-37 in an adaptive-immune mediated model of Inflammatory Bowel Disease.
Abstract : Interleukin-37 (hIL-37) protects mice from innate-immune mediated models of inflammation. We aimed to determine whether hIL-37 may play protective a role in adaptive-immune mediated model of Crohn's Disease (TNFdeltaARE), that develops ileitis and arthritis. Ilea from untreated TNFdeltaARE and TNFdeltaARE/hIL-37tg mice were collected for histology. Ileitis severity at basal conditions showed no difference between TNFdeltaARE and TNFdeltaARE/hIL-37tg mice. No differences were observed in CD4, CD8, B220, or CD11c cells isolated from the mesenteric lymph node or spleen. To determine whether colonic injury was required for therapeutic effect, mice were treated with Dextran Sodium Sulfate (DSS) to induce colitis. Weights were monitored daily. Mice were sacrificed and intestine collected for evaluation of ileitis and colitis severity. Although significant change in weight was observed upon DSS treatment at day 6 and 7 between TNFdeltaARE and TNFdeltaARE/hIL-37tg mice, we did not observe any changes in ileal scores. Our results suggest that hIL-37 does not attenuate ileitis in TNFdeltaARE/hIL-37tg mice under basal conditions, although treatment with DSS seems to reduce the inflammation. However the absence of significance may be due to the small sample size, and an increased n in future experiments may provide clearer evidence of a potential role for hIL-37 in attenuating adaptive-immune mediated inflammation.