Sung-Geun Lee

Homeotropically aligned nematic liquid crystal device locked by a polymer wall with wide viewing angle

We fabricated a homeotropically aligned nematic liquid crystal display (LCD), where the chiral-doped LC with negative dielectric anisotropy is locked by a polymer wall under crossed polarizers and whose on and off states are controlled by a vertical electric field. In the absence of an electric field, the rubbing-free device appears to be dark. In the presence of the field, the homeotropically aligned LCs tilt down, giving rise to brightness but four brush schlieren textures appear with point singularity S=+1. This indicates that the mid-directors have radial alignment inside the polymer wall in the voltage-on state. Consequently, the device shows excellent viewing angle characteristics. The electro-optic characteristics of one prototype with excellent viewing angles are reported herein.

Full-Genomic Analysis of a Human Norovirus Recombinant GII.12/13 Novel Strain Isolated from South Korea

Norovirus (NoV) genogroups I and II are frequently recognized as the main causes of acute gastroenteritis and outbreaks of non-bacterial foodborne diseases. Furthermore, variants and recombinant strains of this virus are continuously emerging worldwide. The aim of this study was to identify NoV strains and to investigate and characterize rare genotypes. Stool samples (n = 500) were collected from patients with symptoms of acute gastroenteritis in Korea between December 2004 and November 2007. For analysis of the samples, rapid genotype screening was performed using reverse transcriptase-polymerase chain reaction. Full sequencing, using a newly designed set of 12 primers, revealed GII-12/13 strain. The partial sequence of GII-12/13 strain was compared with published NoV (GII-1 - 14) sequences targeting RdRp and capsid regions using phylogenetic analysis with the SimPlot program, which could evaluate recombination breakpoints. SimPlot analysis was also performed with the strain GII-12/Gifu-96/JPN (AB045603) for the RdRp region and with GII-13/G5175B-83/AUS(DQ379714) for the capsid region. NoV was detected in 19 of the 500 stool samples (3.8%). Genogroup GII-4 was found most frequently (n = 9, 1.8%), followed by GII-3 (n = 4, 0.8%), GII-6 (n = 3, 0.6%), GI-6 (n = 2, 0.4%), and GII-12/13 (n = 1, 0.2%). Importantly, we identified a novel NoV recombinant strain, C9-439 (KF289337), indicating potential risks, which suggested that, recombination occurred in the region between open reading frames 1 and 2 of the GII-12/13 strain and that breakpoints occurred in the polymerase region.

Molecular epidemiology of norovirus GII.4 variants in children under 5 years with sporadic acute gastroenteritis in South Korea during 2006-2013.

BACKGROUNDnThe global emergence of norovirus (NoV) GII.4 variants has raised public concerns in the world including South Korea since 1996.nnnOBJECTIVEnWe analyzed seasonality and genotypic pattern for sporadic cases by norovirus GII-4 variants.nnnSTUDY DESIGNnTo determine the epidemic status of GII.4 variants in South Korea during 2006-2013, 7301 fecal specimens were collected from children who were younger than 5 years and had sporadic acute gastroenteritis (AGE).nnnRESULTSnDuring the study period, NoVs were the most prevalent viral agent, detected in 877 (12.0%) of the 7301 fecal specimens from children with sporadic AGE. NoV GII strains predominantly accounted for 97.6% of all sporadic NoV infections. NoV GII.4 was the most prevalent genotype and comprised 67.6% of the NoV GII strains. However, seasonal prevalence of GII.4 strains varied depending on the spread of GII.4 variants. GII.4-2006b variant most predominantly circulated from 2006-2007 to 2009-2010 and persisted during other seasons. GII.4-2009 variant was first detected in January 2010 and predominant in 2011-2012. However, it was rapidly displaced by GII.4-2012 variant, which emerged in May 2012 and substantially circulated in 2012-2013.nnnCONCLUSIONSnThe frequent emergence and rapid spread of GII.4 variants significantly affect the magnitude of sporadic NoV infections in children. Hence, to minimize the disease burden of NoV infections, GII.4 strains should be considered as a primary target for vaccine development against NoVs.

Emergence of Norovirus GII.4 variants in acute gastroenteritis outbreaks in South Korea between 2006 and 2013

BACKGROUNDnNew emerging strains of noroviruses (NoVs) often increase acute gastroenteritis (AGE) outbreaks worldwide.nnnOBJECTIVEnWe analyzed the epidemiological features and genotypic patterns of NoVs in AGE outbreaks.nnnSTUDY DESIGNnTo elucidate the public health impact of NoVs during AGE outbreaks in South Korea, a molecular and epidemiological investigation was performed with 318 AGE outbreaks reported from the Gyeonggi province of South Korea during the period from 2006 to 2013.nnnRESULTSnNoVs were associated with 102 (32.1%) of the AGE outbreaks. Epidemiological data revealed that the majority of NoV outbreaks were in the student group (47.1%), and the majority of AGE patients were identified in schools (68.8%). NoV genogroup (G) II strains were associated with 94 (92.2%) of the NoV outbreaks, and GII.4 strains were predominantly associated with 57.6% (n=49) of NoV GII outbreaks. Four GII.4 variants (2006b, 2007, 2009 and 2012 variants) emerged and showed different contributions to NoV outbreak activity. The 2006b variant was predominantly associated with NoV outbreaks during the early years of the study period, and was subsequently displaced by the New Orleans 2009 variant, and most recently by the Sydney 2012 variant. In addition, the GII.2, GII.14, and GII.17 strains have recently been often associated with NoV AGE outbreaks.nnnCONCLUSIONSnThe emergence of new NoV GII.4 variants significantly affected the NoV outbreak activity in South Korea during the period from 2006 to 2013. The surveillance for new emerging strains affecting NoV outbreak activity should be intensified to develop an adequate policy to prevent further NoV outbreaks.

Genetic analysis of the capsid region of norovirus GII.4 variants isolated in South Korea

Norovirus is one of the major causes of non-bacterial gastroenteritis in humans. The aim of this study was to analyze the amino acid variation of open reading frame 2 of GII.4 variants in South Korea during the period from November 2006 to December 2012. Sixty-nine complete nucleotide sequences of open reading frame 2 were obtained from 113 GII.4 strains. The GII.4 2006b variants were detected predominantly between 2006 and 2009; however, new GII.4 variants, which were termed the 2010 variant and the 2012 variant, emerged in 2010 and 2012, respectively. The number of GII.4 2006b variants steadily decreased until 2012, whereas the number of gastroenteritis cases caused by the new variants increased between 2010 and 2012. The amino acid sequence in the ORF2 region obtained in this study was compared with other GII.4 variants isolated in various countries. Amino acid variations were observed primarily at epitope sites and the surrounding regions. Amino acids 294, 359, 393, and 413 of the P2 subdomain were the most variable sites among the GII.4 variants. The information in this study can be useful in basic research to predict the emergence and determine the genetic functions of new GII.4 variants.

Vertical alignment liquid crystal cell with optically compensated splay configuration of the liquid crystal

We have observed a phenomenon associated with a transition from vertical alignment to an optically compensated splay structure. With rubbed homeotropic alignment in parallel directions, the device shows vertical alignment but the liquid crystals (LCs) are twisted 180° in the absence of an electric field. Depending on the voltage applied, two different configurations of LCs are possible. After applying a critical voltage, the LC configuration becomes splayed such that the middirector lies parallel to the substrate and around it, and a hybrid structure forms symmetrically. A method for obtaining the transition and the electro-optic characteristics of the device is discussed.

Full genomic analysis of a human rotavirus G1P[8] strain isolated in South Korea.

A rotavirus G1P[8] strain C1‐81 was isolated from a 5‐month‐old female infant admitted to hospital with fever and severe diarrhea in Incheon, South Korea. To investigate its full genomic relatedness and its group, the full genome of strain C1‐81 was determined. Based on a full genome classification system, C1‐81 was shown to possess the typical Wa‐like genotype constellation: G1‐P[8]‐I1‐R1‐C1‐M1‐A1‐N1‐T1‐E1‐H1. On the basis of sequence similarities, the strain was shown to be the closest related strain to contemporary human rotavirus strains with recent strains isolated in Asia. This C1‐81 strain showed the highest degree of nucleic acid similarity (98.8% and 97%) to G1 B4633‐03 and P[8] (Thai‐1604 and Dhaka8‐02), respectively. This is the first report that group A rotavirus was analyzed with G1P[8] in South Korea. The study of the complete genome of the virus will help understanding of the evolution of rotavirus. J. Med. Virol. 85:157–170, 2012.

Complete genome sequencing of a recombinant strain between human astrovirus antigen types 2 and 8 isolated from South Korea.

Human astroviruses (HAstVs) occur worldwide and are known to the causative agents of diarrhea in infants and elderly patients with immune dysfunction. This study aimed to identify recombinant HAstV strains and characterize rare genotypes. The full-length genome of a recombinant HAstV strain isolated from the stool sample of a patient with acute gastroenteritis from South Korea was amplified using three pairs of previously designed primers and seven newly designed primers. The recombinant HAstV was 6757-bp long and contained three sequential open reading frames (ORFs), designated as ORF1a (2781 bp), ORF1b (1548 bp), and ORF2 (2349 bp). Our findings suggested that a recombination event had occurred between ORF1b and ORF2 of the isolated strain, with a recombination breakpoint at 4081 bp. To our knowledge, this is the first study to reveal the complete nucleotide sequence of a recombinant HAstV strain from South Korea. Our study findings might be useful for identifying other recombinant HAstV strains and for developing vaccines against this pathogenic virus.

Detection of waterborne norovirus genogroup I strains using an improved real time RT-PCR assay

Noroviruses (NoVs) are the major global source of acute gastroenteritis (AGE) outbreaks. To detect NoVs, real-time reverse transcription-quantitative PCR (RT-qPCR) assays have been widely employed since the first decade of the 21st century. We developed a redesigned probe, JJV1PM, for RT-qPCR assay detection of NoV genogroup (G) I strains. The new RT-qPCR assay using the JJV1PM-probe showed broader strain reactivity for 10 NoV GI genotypes, while the old method, using the JJV1PT-probe assay, detected only 7 NoV GI genotypes in a validation panel using human fecal specimens. The improved RT-qPCR assay was also successfully applied to water samples. The JJV1PM-probe assay identified 7 NoV GI genotypes, whereas the JJV1PT-probe assay detected only 2 NoV GI genotypes from water samples. Notably, groundwater-borne NoV GI strains detected by the improved JJV1PM-probe assay were associated with groundwater-borne AGE outbreaks in South Korea. The results of this study underscore the importance of the evaluation of RT-qPCR assays using recently circulating NoV strains prior to field application.

Full sequence analysis and characterization of a human astrovirus type 1 isolate from South Korea

Human astroviruses are recognized as an important cause of infantile gastroenteritis around the world. In South Korea, sporadic cases of HAstV infection have been reported since 2002. However, hitherto, there have been no studies reporting the whole genome sequence of an HAstV isolate from South Korea. Hence, we sequenced and analyzed the entire genome of an HAstV-1 strain (lhar) that was isolated in Seoul, South Korea. The whole-genome sequence analysis revealed 3 open reading frames comprising the whole genome: ORF1a (2,763 bp), ORF1b (1,548 bp), and ORF2 (2,364 bp). The lhar strain showed amino acid identities with 8 other reference strains of 87.6–98.7%, 94.2–98.8%, and 62.6–99.0% in the ORF1a, ORF1b, and ORF2 regions, respectively. The amino acid sequence of the capsid region encoded by ORF2 was compared with a total of 19 HAstV-1 strains and 8 HAstVs reference strains isolated in various countries. This revealed 1 amino acid substitution, at aa412 (Pro → Arg) in ORF2. This study, the first to report the full-length sequence of an HAstV isolated in South Korea, is meaningful in that it can be used as a full-length HAstV sequence standard for future comparison studies. It may also prove useful to the field of public health field by facilitating the diagnosis and the prediction of new emerging variants.