toxoplasma develop similar pathologies, including higher parasite burdens, inflam- mation and necrosis in the liver and central nervous system. In order to assess whether or not there was a humoral defect in the IL-6 KO we measured serum Immu- noglobulin during the course of infection with Toxoplasma gondii. IL-6 KO mice have less parasite-specific IgG2a when compared to WT and fewer PNA+ Germinal Center B cells and IgG2a+ plasma cells. The deficiency of GC B cells is not due to diminished expansion of the total B cell population during the course of infection, suggesting a germinal center-specific defect. Previous studies have demonstrated the importance of CD4+ T cells in maintaining germinal center reactions. More specifically a subset of CD4 T cells that express the chemokine receptor CXCR5, called T Follicular helper cells (T FH ), were identified as having a primary role in maintaining germinal center reactions. IL-6 KO mice infected with toxoplasma have a 50-60% reduction in T FH cells during the course of infection in LN and Spleen. These deficits correlate with reduced production of the IL-6 inducible cytokine IL-21, a known T FH differentiation factor. Infected IL-6 KO that were given 2e6 T FH cells intravenously had higher levels of par- asite-specific IgG2a and fewer areas of necrosis in the liver. Additionally, IL-6 KO mice given immune sera have lower parasite burdens Collectively, these data suggest that the T FH cell defect underlies the humoral defects in infected IL-6 KO mice and that these cells are required for production of antigen-specific immunoglobulins. T cell help for B cells is a fundamental aspect of immunity, and our work has revealed a novel role for IL-6 in the generation of T FH during infection with Toxoplasma gondii. doi:10.1016/j.cyto.2010.07.388 PS3-50 Differential transcriptosome profiles and antiviral effect of interferon-k and interferon-a on HCV-infected and uninfected hepatoma cells Alison A. Murphy 1 , Xiaozhen Zhang 1 , Jun Yang 2 , Raymond Donnelly 3 , Howard Young 4 , Richard A. Lempicki 2 , Shyam Kottilil 1 , 1 Laboratory of Immunoregulation, NIAID, NIH, Bethesda, MD 20892, 2 SAIC-Frederick, Frederick, MD, 3 CDER, FDA, Bethesda, MD, 4 Laboratory of Experimental Immunology, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 Background: IFN-k polymorphisms are associated with spontaneous clearance of Hepatitis C and enhanced cure rates. However, the mechanisms of IFN-k activity in the control and pathogenesis of HCV and response to IFN-a are presently unknown. In this study, we performed transcriptosome profiling of HCV-infected and uninfected Huh cells to identify the cellular factors modulated by HCV infection and IFN. Meth- ods: We performed in vitro experiments and DNA microarray (Affymetrix U133plus 2.0) analysis using RNA extracted from Huh7.5 cells infected (using supernatants from infectious cultures of J6/JFH-1/Huh7.5cc system) or uninfected in the presence or absence of IFN-a or IFN-k. After Loews normalization and Hierarchical clustering, two-way ANOVA was performed to identify differentially expressed genes (Fold Change of 2 and p < 0.05). RT-PCR was performed to validate biologically relevant genes determined by functional annotation analysis and literature mining algorithms. Results: IFN-k exhibited comparable levels of suppression of HCV replication to that observed with IFN-a at 24 hours (34 ± 8% vs. 56 ± 12 %) and at 72 hours (80 ± 9% vs. 74 ± 11%). In both JFH-uninfected and infected hepatoma cells, IFN-k and IFN-a induced similar gene expression profile. However, IFN-k preferentially induced sev- eral ISGs at higher levels than IFN-a in uninfected Huh cells (IFIH1, OAS2, STAT2) and JFH-infected Huh cells (IFI35, IFI44, OAS3 and IL18) while IFN-a induced higher expression of IFI6, ISG15 and IFITM3 genes when compared to IFN-k. Conclusion: IFN-k and IFN-a have very similar transcription profiles in HCV uninfected and infected Huh cells. However, IFN-k selectively induces genes such as IL-18, that may result in hepatic NK cell activation facilitating HCV clearance. Kinetics of IFN- k-mediated antiviral effect suggests a delayed, but more sustained suppression of HCV replication. Our data suggests that IFN-k may have an equal therapeutic but bet- ter safety profile than current treatment of HCV. doi:10.1016/j.cyto.2010.07.389 PS3-51 TNF-alpha-induced pro-inflammatory monocyte differentiation in cutaneous leishmaniasis: Role for notch signaling Sara Passos, Angela Giudice, Thais Delavechia, Olivia Bacellar, Lucas P. Carvalho, Edgar M. Carvalho, Immunology Service – Federal University of Bahia, Salvador, BA, Brazil Cutaneous leishmaniasis (CL) due to L. braziliensis infection leads to secretion of high levels of monocytes-derived TNF-alpha, cytokine known to contribute to tissue damage and ulcer formation observed in this disease. Increased frequency of pro- inflammatory monocytes (CD14+CD16+) has been associated with pathogenesis of many inflammatory diseases such as sepsis and rheumatoid arthritis. These cells are known to secrete high levels of TNF-alpha and migrate to inflammatory sites. We have found that CL patients have higher frequency of circulating CD14+CD16+ cells in blood when compared to healthy subjects. Characterization of these cells revealed that they had an activated phenotype. Notch signaling takes place when the ligands (Delta and Jagged) bind to Notch receptors, which gets cleaved by a gamma secretase. Notch intracellular domain translocates to the nucleus and induces transcription of Notch target genes. It has been shown that Notch signaling mediates activation of mouse macrophage and dendritic cell. In order to test whether TNF- alpha-mediated differentiation of human monocytes into CD14+CD16+ cells relied on signaling through Notch receptor, we used a gamma secretase inhibitor to block Notch signaling. Inhibition of gamma secretase activity prevented TNF-alpha-induced differentiation of CD14+ cells into pro-inflammatory monocytes. These results shows increased frequency of circulating activated monocytes in CL patients, and underlies an important role for Notch signaling in controlling TNF-alpha-induced activation of human monocytes. doi:10.1016/j.cyto.2010.07.390 PS3-52 Inhibitory effects of heme arginate on HIV-1 Growth Prakash Shankaran, Zora Melkova , Department of Immunology and Microbiology, 1 st Medical Faculty, Charles University, Prague, Czech Republic NF-jB is an essential transcription factor that regulates expression of various cytokines, other factors as well as reactivation of the HIV-1 provirus. Its activation is controlled by multiple signaling cascades, and it is dependent on the activation sta- tus and the redox potential of the immune cell. NF-jB translocation to the nucleus can be stimulated by both oxygen and nitrogen free radicals, leading to the reactiva- tion of the HIV provirus. On the other hand, HIV replication itself stimulates produc- tion of various cytokines and expression of the inducible NO-synthase, generating a vicious cycle. Heme is a well known scavenger of NO, thus, it could be suggested to decrease the NO-mediated reactivation of the latent provirus. Heme is also a very effi- cient inhibitor of HIV-1 reverse transcriptase and it was shown to ameliorate HIV-1 infection via induction of heme oxygenase-1. Normosang (heme arginate) is a human hemin-containing compound used to treat acute porphyria. There are no reports about the effect of heme arginate on HIV-1. Therefore, we attempted to study the effect of heme arginate on the growth and reactivation of HIV-1 in the infected T-cell lines Jurkat and A3.01, in PMA-stimulated ACH-2 cells that harbour HIV-1 proviral DNA, and in PMA-stimulated Jurkat cells that harbour an HIV-minigene consisting of an LTR-EGFP. Here we demonstrate that heme arginate inhibits the overall growth of HIV-1 characterized by the levels of p24 antigen at the concentrations that are not toxic to the cells. Additionally, heme arginate does not affect the activation of the cells as determined by the expression of CD69, a T-cells activation marker. doi:10.1016/j.cyto.2010.07.391 PS3-53 Association of IL-10 polymorphisms with hepatitis C infection susceptibility in Pakistani population Amna Salman 1 , Tahir A. Baig 1 , Ishtiaq Qadri 1 , 1 NUST Centre of Virology and Immunology, National University of Sciences and Technology, Sector H-12, Islamabad Background: Hepatitis C virus (HCV) commonly causes a chronic infection but few of patients are able to clear the virus naturally. IL-10 is an anti-inflammatory cytokine that can suppress the immune response against HCV. Interindividual variations in IL- 10 production were genetically contributed by polymorphisms within IL-10 promoter region. Aim: The aim of this study was to investigate the association of IL-10 gene pro- moter -1082 G/A, -819 C/T, and 592 C/A polymorphism with HCV infection suscepti- bility in Pakistani individuals. Methods: Eighty nine chronically infected patients and 99 controls were enrolled in the study. IL10 (-1,082 G/A, -819 C/T, -592 C/A) genotyp- ing was performed by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Results: A suggestive evidence of association with hepatitis C was obtained for IL-10 819 C/T (592 C/A) (p: 0.031) promoter polymorphism at the level of allele and but not in genotype distribution. IL-10 1082 allele showed no asso- ciation while positive association of GG (p: 0.001) gene and negative for GA (0.001) gene was observed. Higher frequencies were observed for GTA (p: 0.024), ACC (p: 0.014) haplotype and GCC/GTA (p: 0.005) diplotype in HCV patients then controls while diplotype GCC/ATA showed protective effect against HCV. Conclusion: Our find- ings suggest that the imbalance between the pro-inflammatory and anti-inflamma- tory responses mediated by polymorphisms in the IL-10 genes may influence the susceptibility of HCV infection. doi:10.1016/j.cyto.2010.07.392 92 Abstracts / Cytokine 52 (2010) 82–98