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Sujin Lee

Publications and source records attributed to Sujin Lee.

15 recordsLinked to original sources
PubMed2006

Structural and functional insights into intramolecular fructosyl transfer by inulin fructotransferase.

Inulin fructotransferase (IFTase), a member of glycoside hydrolase family 91, catalyzes depolymerization of beta-2,1-fructans inulin by successively removing the terminal difructosaccharide units as cyclic anhydrides via intramolecular fructosyl transfer. The crystal structures of IFTase and its substrate-bound complex reveal that IFTase is a trimeric enzyme, and each monomer folds into a right-handed parallel beta-helix. Despite variation in the number and conformation of its beta-strands, the IFTase beta-helix has a structure that is largely reminiscent of other beta-helix structures but is unprecedented in that trimerization is a prerequisite for catalytic activity, and the active site is located at the monomer-monomer interface. Results from crystallographic studies and site-directed mutagenesis provide a structural basis for the exolytic-type activity of IFTase and a functional resemblance to inverting-type glycosyltransferases.

Amino Acid Sequence↗
PubMed2006

Tissue-specific regulation of CD8+ T-lymphocyte immunodominance in respiratory syncytial virus infection.

Cytotoxic T lymphocytes (CTLs) are critical for control of respiratory syncytial virus (RSV) infection in humans and mice. To investigate cellular immune responses to infection, it is important to identify major histocompatibility complex (MHC) class I-restricted CTL epitopes. In this study, we identified a new RSV-specific, H-2K(d)-restricted subdominant epitope in the M2 protein, M2(127-135) (amino acids 127 to 135). This finding allowed us to study the frequency of T lymphocytes responding to two H-2K(d)-presented epitopes in the same protein following RSV infection by enzyme-linked immunospot (ELISPOT) and intracellular cytokine assays for both lymphoid and nonlymphoid tissues. For the subdominant epitope, we identified an optimal nine-amino-acid peptide, VYNTVISYI, which contained an H-2K(d) consensus sequence with Y at position 2 and I at position 9. In addition, an MHC class I stabilization assay using TAP-2-deficient RMA-S cells transfected with K(d) or L(d) indicated that the epitope was presented by K(d). The ratios of T lymphocytes during the peak CTL response to RSV infection that were specific for M2(82-90) (dominant) to T lymphocytes specific for M2(127-135) (subdominant) were approximately 3:1 in the spleen and 10:1 in the lung. These ratios were observed consistently in primary or secondary infection by the ELISPOT assay and in secondary infection by MHC/peptide tetramer staining. The number of antigen-specific T lymphocytes dropped in the 6 weeks after infection; however, the proportions of T lymphocytes specific for the immunodominant and subdominant epitopes were maintained to a remarkable degree in a tissue-specific manner. These studies will facilitate investigation of the regulation of immunodominance of RSV-specific CTL epitopes.

Amino Acid Sequence↗
PubMed2006

Crystallization and initial crystallographic characterization of the Corynebacterium glutamicum nitrilotriacetate monooxygenase component A.

Safety and environmental concerns have recently dictated the proper disposal of nitrilotriacetate (NTA). Biodegradation of NTA is initiated by NTA monooxygenase, which is composed of two proteins: component A and component B. The NTA monooxygenase component A protein from Corynebacterium glutamicum was crystallized using the sitting-drop vapour-diffusion method in the presence of ammonium sulfate as the precipitant. X-ray diffraction data were collected to a maximum resolution of 2.5 A on a synchrotron beamline. The crystal belongs to the monoclinic space group C2, with unit-cell parameters a = 111.04, b = 98.51, c = 171.61 A, beta = 101.94 degrees . The asymmetric unit consists of four molecules, corresponding to a packing density of 2.3 A(3) Da(-1). The structure was solved by molecular replacement. Structure refinement is in progress.

Bacterial Proteins↗
PubMed2006

Depletion of MCP-1 increases development of herpetic stromal keratitis by innate immune modulation.

Chemokines are important chemoattractant inflammatory molecules, but their interdependent network in disease pathogenesis remains unclear. Studies in mouse models have shown that herpetic stromal keratitis (SK) is produced by the consequence of a tissue-destructive immunoinflammatory reaction involving herpes simplex virus type 1 (HSV) infection. Here we found that ocular HSV infection leads to increased expression of monocyte chemoattractant protein-1 (MCP-1), one of the major chemoattractants for immune cells that express CCR2, in the SK cornea. However, MCP-1 is unlikely to be a chemoattractant for infiltrating Gr-1(+), CD11b(+) cells in SK, as these cells are found to be CCR2 negative. Nevertheless, infection of MCP-1(-/-) mice resulted in more severe SK lesion severity compared with WT mice (P<0.01). We demonstrated that the loss of MCP-1 in the SK cornea caused a significant overexpression of macrophage inflammatory protein-2 (MIP-2) (P<0.01) on days 2 and 4 postinfection and increased infiltration of inflammatory cells (Gr-1-high and CD11b(+)) expressing CXCR2, a receptor for MIP-2, into the cornea. Subsequently, increased infiltration of inflammatory cells accelerated by MIP-2 overexpression might result in the high production of inflammatory molecules, including vascular endothelial growth factor (VEGF) and IL-1beta in SK, as well as CpG oligodeoxynucleotide (ODN)-implanted eyes of MCP-1(-/-) mice. These results indicate that MCP-1 in the SK cornea might regulate the expression of other chemokines, as well as the infiltration of inflammatory cells and control development of SK.

Animals↗
PubMed2006

Vascular endothelial growth factor receptor 2-based DNA immunization delays development of herpetic stromal keratitis by antiangiogenic effects.

Stromal keratitis (SK) is an immunoinflammatory eye lesion caused by HSV-1 infection. One essential step in the pathogenesis is neovascularization of the normally avascular cornea, a process that involves the vascular endothelial growth factor (VEGF) family of proteins. In this report, we targeted the proliferating vascular endothelial cells expressing VEGFR-2 in the SK cornea by immunization with recombinant Salmonella typhimurium containing a plasmid encoding murine VEGFR-2. This form of DNA immunization resulted in diminished angiogenesis and delayed development of SK caused by HSV-1 infection and also reduced angiogenesis resulting from corneal implantation with rVEGF. CTL responses against endothelial cells expressing VEGFR-2 were evident in the VEGFR-2-immunized group and in vivo CD8+ T cell depletion resulted in the marked reduction of the antiangiogenic immune response. These results indicate a role for CD8+ T cells in the antiangiogenic effects. Our results may also imply that the anti-VEGFR-2 vaccination approach might prove useful to control pathological ocular angiogenesis and its consequences.

Angiogenesis Inhibitors↗
PubMed2006

Application of FGF-2 to modulate herpetic stromal keratitis.

PURPOSE: Herpetic stromal keratitis (SK) is a tissue destructive eye lesion caused by infection of herpes simplex virus-1 (HSV-1). One step by which HSV-1 enters the cell is through binding to surface heparan sulfate proteoglycans (HSPG), a process that can be inhibited by fibroblast growth factor 2 (FGF-2). The current study examined the effect of FGF-2 application on the outcome of ocular HSV infection. METHODS: Vero cells were infected with HSV-1 after preincubation with FGF-2 protein, and viral infectivity was determined by plaque reduction assay. In an in vivo study, mice were ocularly treated with FGF-2 before (plasmid DNA) or after (recombinant protein) HSV-1 infection, and SK lesion severity was observed. RESULTS: Whereas FGF-2 had excellent antiviral effects in vitro, it was without significant inhibitory effects when given as plasmid DNA encoding FGF-2 (100 microg/application) onto the cornea of the susceptible mouse (BALB/c) before virus infection. Only minor antiviral effects of FGF-2 in vivo were initially observed. Interestingly, topical treatment of recombinant FGF-2 protein (50 ng, two times daily until day 10 postinfection) into HSV-1-infected corneas significantly reduced SK lesion severity and incidence, presumably by promoting epithelial ulcer healing. CONCLUSIONS: These results suggest that treatment of FGF-2 has therapeutic effects on herpetic SK progression via its role in wound healing.

Administration, Topical↗
PubMed2005

Application of plasmid DNA encoding IL-18 diminishes development of herpetic stromal keratitis by antiangiogenic effects.

HSV-1 infection of the eye can cause a blinding immunoinflammatory stromal keratitis (SK) lesion. Using the mouse model, we have demonstrated that angiogenesis is an essential step in lesion pathogenesis because its inhibition results in diminished severity. The molecules involved in causing corneal angiogenesis are multiple and include the vascular endothelial growth factor (VEGF) family of proteins. In this report we show that application of plasmid DNA encoding IL-18 to the cornea of mice before HSV-1 ocular infection resulted in reduced angiogenesis and diminished SK immunoinflammatory lesions. The antiangiogenic effects of IL-18 treatment appeared to be mediated by inhibition of VEGF production in the cornea. We also showed that IL-18 controlled VEGF expression in vitro and also decreased CpG oligodeoxynucleotide induced VEGF-dependent neovascularization. In addition the administration of IL-18-binding protein, an IL-18 antagonist, into the inflammatory eye resulted in elevated angiogenesis and increased VEGF expression. Our results indicate that IL-18 is an important endogenous negative regulator of HSV-induced angiogenesis resulting in reduced SK lesion severity. Our results could mean that IL-18 administration may represent a useful approach to manage unwanted angiogenesis.

Animals↗
PubMed2004

CXCR2-/- mice show enhanced susceptibility to herpetic stromal keratitis: a role for IL-6-induced neovascularization.

Ocular infection with HSV results in a blinding immunoinflammatory lesion known as herpetic stromal keratitis (HSK). Early preclinical events include inflammatory cell, mainly neutrophils, infiltration of the stroma, and neovascularization. To further evaluate the role of neutrophils in pathogenesis, HSV infection was compared in BALB/c and mice of the same background, but lacking CXCR2, the receptor for chemokines involved in neutrophil recruitment. Our results show clear differences in the outcome of ocular HSV infection in CXCR2-/- compared with control BALB/c mice. Thus, CXCR2-/- animals had minimal PMN influx during the first 7 days postinfection, and this correlated with a longer duration of virus infection in the eye compared with BALB/c mice. The CXCR2-/- mice were also more susceptible to HSV-induced lesions and developed HSK upon exposure to a dose of HSV that was minimally pathogenic to BALB/c mice. The basis for the greater HSK lesion susceptibility of CXCR2-/- mice was associated with an elevated IL-6 response, which appeared in turn to induce the angiogenic factor, vascular endothelial growth factor. Our results serve to further demonstrate the critical role of angiogenesis in the pathogenesis of ocular lesions.

Administration, Topical↗
PubMed2003

CD4+CD25+ T cells regulate virus-specific primary and memory CD8+ T cell responses.

Naturally occurring CD4+CD25+ regulatory T cells appear important to prevent activation of autoreactive T cells. This article demonstrates that the magnitude of a CD8+ T cell-mediated immune response to an acute viral infection is also subject to control by CD4+CD25+ T regulatory cells (Treg). Accordingly, if natural Treg were depleted with specific anti-CD25 antibody before infection with HSV, the resultant CD8+ T cell response to the immunodominant peptide SSIEFARL was significantly enhanced. This was shown by several in vitro measures of CD8+ T cell reactivity and by assays that directly determine CD8+ T cell function, such as proliferation and cytotoxicity in vivo. The enhanced responsiveness in CD25-depleted animals was between three- and fourfold with the effect evident both in the acute and memory phases of the immune response. Surprisingly, HSV infection resulted in enhanced Treg function with such cells able to suppress CD8+ T cell responses to both viral and unrelated antigens. Our results are discussed both in term of how viral infection might temporarily diminish immunity to other infectious agents and their application to vaccines. Thus, controlling suppressor effects at the time of vaccination could result in more effective immunity.

Adoptive Transfer↗
PubMed2003

Influence of DNA encoding cytokines on systemic and mucosal immunity following genetic vaccination against herpes simplex virus.

The aim of our investigation was to improve the effectiveness of DNA vaccines against herpes simplex virus (HSV) infection. We chose coimmunization with DNA encoding cytokines known to emphasize components of immune defense that best correlate with immune protection. These include interferon-producing T and NK cells and the IgG2a isotype immunoglobulin. Our results show that the coadministration of plasmid DNA encoding IL-12 or IL-18 along with glycoprotein B (gB) DNA improves immune induction. Recipients of the coimmunization procedure had elevated humoral as well as IFN-gamma-producing T cell responses and showed greater resistance to vaginal challenge with a lethal dose of HSV-1. The adjuvant effects were observed when the vaccines were administered either systemically or mucosally. By most assays, the adjuvant effect of IL-18 was superior to IL-12, although gB DNA plus IL-18 failed to induce levels of immunity achieved by UV-inactivated HSV immunization. Mucosal immunization proved as an effective means of inducing systemic immunity, but was less effective than the systemic route for inducing protection from vaginal challenge. Our results also demonstrated that protection from such challenges was mainly a property of IFN-gamma. Thus, immunized IFN-gamma-/- mice remained susceptible to challenges even while generating readily measurable immune responses. The approach of using DNA vaccines combined with DNA encoding cytokines holds promise and represents a potentially useful approach for vaccines.

Administration, Intranasal↗
PubMed2003

Internet over-users' psychological profiles: a behavior sampling analysis on internet addiction.

What kinds of psychological features do people have when they are overly involved in usage of the internet? Internet users in Korea were investigated in terms of internet over-use and related psychological profiles by the level of internet use. We used a modified Young's Internet Addiction Scale, and 13,588 users (7,878 males, 5,710 females), out of 20 million from a major portal site in Korea, participated in this study. Among the sample, 3.5% had been diagnosed as internet addicts (IA), while 18.4% of them were classified as possible internet addicts (PA). The Internet Addiction Scale showed a strong relationship with dysfunctional social behaviors. More IA tried to escape from reality than PA and Non-addicts (NA). When they got stressed out by work or were just depressed, IA showed a high tendency to access the internet. The IA group also reported the highest degree of loneliness, depressed mood, and compulsivity compared to the other groups. The IA group seemed to be more vulnerable to interpersonal dangers than others, showing an unusually close feeling for strangers. Further study is needed to investigate the direct relationship between psychological well-being and internet dependency.

Adolescent↗
PubMed2002

Induction of CD8 T-cell-specific systemic and mucosal immunity against herpes simplex virus with CpG-peptide complexes.

Oligodeoxynucleotides (ODN) containing unmethylated CpG motifs exert powerful adjuvant activity in vivo and in vitro. Administered with antigen they induce a population of antigen-specific CD8+ T cells. In this study we immunized C57BL/6 mice with bioactive CpG ODN combined with an immunodominant epitope derived from herpes simplex virus (HSV) glycoprotein B (amino acids 498 to 505; SSIEFARL) and analyzed the magnitude and durability of the peptide-specific response. The effectiveness of the CD8+ T-cell response as measured by peptide-specific tetramers, peptide-induced intracellular gamma interferon expression, and resistance to systemic and mucosal challenge during the acute and memory phases was compared with the response induced by immunization with recombinant vaccinia virus encoding SSIEFARL as a minigene (VvgB(498-505)). Confirming the reports of others, our results demonstrate that the CpG ODN-peptide approach generates an antigen-specific CD8+ T-cell population, but the frequency of CD8+ T cells is lower than that induced by VvgB(498-505). Nevertheless, the protection level was comparable when mice were systemically and mucosally challenged during the acute phase. However, such responses by both groups waned with time and were functionally less effective. Still, our results indicate that the CpG ODN-peptide immunization system holds promise as a means of selectively inducing a CD8+ T-cell response against HSV.

Animals↗
PubMed2002

Role of matrix metalloproteinase-9 in angiogenesis caused by ocular infection with herpes simplex virus.

In this report, we demonstrate that herpes simplex virus (HSV) infection of the cornea results in the upregulation of the matrix-degrading metalloproteinase enzyme MMP-9. This enzyme was shown to contribute to the neovascularization process that occurs in the corneal stroma in response to HSV infection. The likely source of MMP-9, at least initially after infection, was neutrophils that were signaled to invade the cornea soon after infection. Corneal infiltrating neutrophils were shown to express MMP-9, and preventing the neutrophil response with specific mAb diminished MMP-9 expression as well as the extent of angiogenesis. Further supporting a role for MMP-9 in HSV-induced corneal angiogenesis was the observation that inhibition of MMP-9 with the specific inhibitor TIMP-1 resulted in reduced angiogenesis. In addition, angiogenesis was diminished in ocularly infected MMP-9 knockout mice. Our results demonstrate that MMP-9 is involved in angiogenesis caused by HSV. Since angiogenesis appears to represent a vital step in the pathogenesis of herpetic stromal keratitis, these results indicate that targeting MMP-9 for inhibition should prove useful for the therapy of herpetic stromal keratitis.

Animals↗
PubMed2002

IL-12 suppresses the expression of ocular immunoinflammatory lesions by effects on angiogenesis.

Topical application of plasmid DNA encoding IL-12 to the cornea of mice prior to ocular infection with Herpes simplex virus type 1 (HSV) results in diminished corneal immunoinflammatory lesions. Such herpetic stromal keratitis (HSK) reactions in humans represent an important cause of blindness. The effect of IL-12 pretreatment acted via inhibitory effects on corneal neovascularization rather than by inhibiting viral replication or the function of CD4(+) T cells that mediate HSK. The antiangiogenesis induced by IL-12 DNA application was mediated indirectly via the cytokine IFN-gamma and one or both of two chemokine molecules, IP-10 and MIG. Thus IL-12 DNA administration lacked modulatory effects on HSK in GKO mice, indicating the necessary involvement of IFN-gamma induction for antiangiogenesis. In contrast, exposure of GKO mice to IP-10 DNA did suppress the severity of HSK. Furthermore, treatment with specific antisera to IP-10 and MIG in HSV-infected mice abrogated the IL-12-induced inhibitory effect on lesion severity. Taken together, our data indicate that the HSV-induced ocular immunoinflammatory lesions can be modulated by IL-12 and that this effect results from chemokine inhibition of angiogenesis. The use of antiangiogenesis therapy might represent a useful control measure against HSK.

Animals↗