Complete sequence analysis of human norovirus GII.17 detected in South Korea.

Norovirus, a major cause of gastroenteritis in people of all ages worldwide, was first reported in South Korea in 1999. The most common causal agents of pediatric acute gastroenteritis are norovirus and rotavirus. While vaccination has reduced the pediatric rotavirus infection rate, norovirus vaccines have not been developed. Therefore, prediction and prevention of norovirus are very important. Norovirus is divided into genogroups GI-GVII, with GII.4 being the most prevalent. However, in 2012-2013, GII.17 showed a higher incidence than GII.4 and a novel variant, GII.P17-GII.17, appeared. In this study, 204 stool samples collected in 2013-2014 were screened by reverse transcriptase-polymerase chain reaction; 11 GI (5.39%) and 45 GII (22.06%) noroviruses were identified. GI.4, GI.5, GII.4, GII.6 and GII.17 were detected. The whole genomes of the three norovirus GII.17 were sequenced. The whole genome of GII.17 consists of three open reading frames of 5109, 1623 and 780 bp. Compared with 20 GII.17 strains isolated in other countries, we observed numerous changes in the protruding P2 domain of VP1 in the Korean GII.17 viruses. Our study provided genome information that might aid in epidemic prevention, epidemiology studies and vaccine development.

Whole-genome sequencing analysis of human bocavirus detected in South Korea.

Human bocaviruses (HBoVs) have been detected in human gastrointestinal infections worldwide. In 2005, HBoV was also discovered in infants and children with infections of the lower respiratory tract. Recently, several genotypes of this parvovirus, including HBoV genotype 2 (HBoV2), genotype 3 (HBoV3) and genotype 4 (HBoV4), were discovered and found to be closely related to HBoV. HBoV2 was first detected in stool samples from children in Pakistan, followed by detection in other countries. HBoV3 was detected in Australia and HBoV4 was identified in stool samples from Nigeria, Tunisia and the USA. Recently, HBoV infection has been on the rise throughout the world, particularly in countries neighbouring South Korea; however, there have been very few studies on Korean strains. In this study, we characterised the whole genome and determined the phylogenetic position of CUK-BC20, a new clinical HBoV strain isolated in South Korea. The CUK-BC20 genome of 5184 nucleotides (nt) contains three open-reading frames (ORFs). The genotype of CUK-BC20 is HBoV2, and 98.77% of its nt sequence is identical with those of other HBoVs, namely Rus-Nsc10-N386. Especially, the ORF3 amino acid sequences from positions 212-213 and 454 corresponding to a variable region (VR)1 and VR5, respectively, showed genotype-specific substitutions that distinguished the four HBoV genotypes. As the first whole-genome sequence analysis of HBoV in South Korea, this information will provide a valuable reference for the detection of recombination, tracking of epidemics and development of diagnosis methods for HBoV.

Full-genome sequence analysis of an uncommon norovirus genotype, GII.21, from South Korea.

Noroviruses (NoVs) are major causal agents of acute gastroenteritis in humans. NoV GII.4 is the predominant genotype globally. However, uncommon and minor types of NoVs are consistently detected and some have been shown to dominate over GII.4. Therefore, the prevalence of dominant and uncommon NoVs makes the identification of these viruses important for the prediction and prevention of pandemics. In this study, the full-genome sequence of a NoV (strain JW) detected in Korea was extensively characterized. The full-length genome was 7510 nucleotides long, and phylogenetic analysis based on the whole-genome sequences, including open reading frame (ORF)1, ORF2, and ORF3, indicated that it belonged to the GII.21 genotype. Strain JW showed maximum identity with strain YO284; however, comparison of the amino acid sequence of ORF2, which functions as an antigen, showed substitutions in several amino acids. GII.21 is not a prevalent epidemiological agent of acute gastroenteritis in humans, but it is consistently found in gastroenteritis patients from several countries. The present study provides the first full-genome sequence analysis of NoV GII.21 isolated from a patient in Korea. Our findings provide not only valuable genome information but also data for epidemiology studies, epidemic prevention, and vaccine development strategies.

An outbreak of norovirus infection associated with fermented oyster consumption in South Korea, 2013.

An acute gastroenteritis (AGE) outbreak was reported in May 2013 in Gyeonggi Province, South Korea. Eight students who had eaten breakfast on 21 May 2013 at a high-school restaurant exhibited AGE symptoms. Our case-control study showed that a strong association was observed between AGE symptoms and fermented oyster consumption. Virological studies also indicated that noroviruses (NoVs) were detected from both clinical samples and fermented oyster samples, and multiple different genotypes (genogroups GII.4, GII.11 and GII.14) of NoVs were present in both samples. The nucleotide sequence similarity between the strains found in the clinical samples and those in the fermented oysters was more than 99·5%. Therefore, to prevent further outbreaks, proper management of raw oysters is necessary and the food industry should be aware of the risk of viral gastroenteritis posed by fermented oysters contaminated with NoVs.

Acute gastroenteritis outbreaks associated with ground-waterborne norovirus in South Korea during 2008-2012.

Epidemiological and virological studies indicate that noroviruses-contaminated groundwater was the primary source of four acute gastroenteritis outbreaks in South Korea between 2008 and 2012. Furthermore, cabbage kimchi was first identified as the vehicle of transmission between groundwater and infected patients in an outbreak in 2011. The proper treatment of groundwater sources prior to use for drinking or in food preparation is necessary to prevent further outbreaks.

Hyperfine-field-mediated spin beating in electrostatically bound charge carrier pairs.

Organic semiconductors offer a unique environment to probe the hyperfine coupling of electronic spins to a nuclear spin bath. We explore the interaction of spins in electron-hole pairs in the presence of inhomogeneous hyperfine fields by monitoring the modulation of the current through an organic light emitting diode under coherent spin-resonant excitation. At weak driving fields, only one of the two spins in the pair precesses. As the driving field exceeds the difference in local hyperfine field experienced by electron and hole, both spins precess, leading to pronounced spin beating in the transient Rabi flopping of the current. We use this effect to measure the magnitude and spatial variation in hyperfine field on the scale of single carrier pairs, as required for evaluating models of organic magnetoresistance, improving organic spintronics devices, and illuminating spin decoherence mechanisms.

Spin Rabi flopping in the photocurrent of a polymer light-emitting diode.

Electron spin is fundamental in electrical and optical properties of organic electronic devices. Despite recent interest in spin mixing and spin transport in organic semiconductors, the actual spin coherence times in these materials have remained elusive. Measurements of spin coherence provide impartial insight into spin relaxation mechanisms, which is significant in view of recent models of spin-dependent transport and recombination involving high levels of spin mixing. We demonstrate coherent manipulation of spins in an organic light-emitting diode (OLED), using nanosecond pulsed electrically detected electron spin resonance to drive singlet-triplet spin Rabi oscillations. By measuring the change in photovoltaic response due to spin-dependent recombination, we demonstrate spin control of electronic transport and thus directly observe spin coherence over 0.5 s. This surprisingly slow spin dephasing underlines that spin mixing is not responsible for magnetoresistance in OLEDs. The long coherence times and the spin manipulation demonstrated are crucially important for expanding the impact of organic spintronics.

In vitro selection and characterization of human immunodeficiency virus type 1 resistant to Zidovudine and tenofovir.

In this study, we undertook to generate HIV-1 resistance to PMPA by in vitro passage and to characterize the cross-resistance patterns and RT mutations in the generated resistant virus. The HIV-1 A102-resistant to AZT was serially passaged for 4 months in the presence of increasing concentrations of PMPA up to maximum of 40 microM on the fresh MT-2 cells. After 25 passages, HIV-1 developed decreased sensitivity to PMPA after long-term in vitro exposure. Selected HIV-1 mutants were characterized by decreased susceptibility to PMPA (4-fold). This decrease could be related to PMPA resistant caused by an amino acid change associated with a V148M substitution. From these results, additional studies will be needed to determine whether a similar mutation in HIV RT develops in patients receiving PMPA or its orally bioavailable prodrug, tenofovir dipivoxil fumarate.

Inhibition of UL54 and UL97 genes of human cytomegalovirus by RNA interference.

Short interfering RNAs (siRNAs), namely siUL54-1 and siU54-2 targeting UL54 (DNA polymerase) gene, and siUL97-1 and siUL97-2 targeting UL97 (phosphotransferase) gene, were used to inhibit respective genes of Human cytomegalovirus (HCMV) and consequently the virus infection process in human foreskin fibroblast (HFF) cultures. The virus infection was monitored by cell morphology (CPE), levels of UL83 and IE86 mRNAs, and virus antigen. The results showed that siUL97-2 remarkably inhibited viral CPE while other siRNAs were less inhibitory. The siRNAs reduced the levels of UL83 mRNA but not that of IE86 mRNA; again, siUL97-2 was most inhibitory. Particularly, siUL97-2 reduced the UL83 mRNA level 14, 19, 203, and 37 times at 24, 48, 72, and 96 hrs post infection (p.i.), respectively. When tested for the effect on viral antigen by immunofluorescent assay (IFA), UL97-2 exerted a marked inhibition. These results demonstrate the effectiveness of siRNAs against experimental HCMV infection and indicate their therapeutic potential.

Defective HIV-1 provirus encoding a multitarget-ribozyme inhibits accumulation of spliced and unspliced HIV-1 mRNAs, reduces infectivity of viral progeny, and protects the cells from pathogenesis.

A HeLa T4 cell line containing a defective human immunodeficiency virus type 1 (HIV-1) DNA (HD4) was isolated. After transactivation with Tat, the HD4 DNA was transcribed into a single 3.7-kb mRNA that encodes a chimeric CD4/Env protein and a multitarget-ribozyme directed against multiple sites within the gp120 coding region of HIV-1 RNA (Chen et al., 1992). Early steps in HIV infection such as entry, reverse transcription, and proviral DNA formation were not affected in HD4 cells, and HD4 was efficiently transactivated after either HIV-1 or HIV-2 infections. HIV-2, which lacks all of the HIV-1-specific ribozyme target sites, replicated to high levels in HD4 cells whereas HIV-1 replication was selectively inhibited. Despite a reduced accumulation of all HIV-1 transcripts, transactivation of HD4 was efficient. Surprisingly, the most abundant, multiply spliced mRNAs were reduced even though they lack all of the ribozyme target sites. These results strongly suggest that the ribozyme co-localizes with unspliced HIV-1 pre-mRNA and/or genomic HIV-1 RNA in the nucleus. Cleavage of these precursor RNAs explains the reduction of all spliced and unspliced HIV-1 RNAs. Cleavage of genomic RNA probably contributed to the three-fold reduction in the infectivity of viral progeny. Thus, the HD4 ribozyme RNA functioned as a ribozyme in the nucleus and as a mRNA for a chimeric CD4/Env protein in the cytoplasm. Its unusual large size for a ribozyme (3.7 kb) indicates that, in the future, other antiviral proteins, like negative transdominant mutant HIV-1 proteins, may also be encoded to increase its antiviral potential in a gene therapy approach.

GB virus C/hepatitis G virus infection among Korean patients with liver diseases and general population.

GB virus C and hepatitis G virus (GBV-C/HGV) have been identified from the patients with acute or chronic liver diseases as possible agents of non-B, non-C hepatitis by two different groups, independently. To investigate whether GBV-C/HGV plays a role among Korean patients with liver diseases, GBV-C/HGV RNA were evaluated in 337 sera by the reverse transcription polymerase chain reaction (RT-PCR) using specific primers derived from 5'-noncoding region of GBV-C/HGV genome. GBV-C/HGV RNA was identified in 11/337 (3.3%). They consisted of 1/160 (0.6%) and 10/177 (3.3%) among the general population and patients with liver diseases, respectively (P < 0.01). Nucleotide sequences of all PCR amplicons were determined by the dideoxy chain termination method and analyzed by molecular evolutionary methods. The phylogenetic tree showed all sequences could be divided into three genotypes. These results indicate that: (1) GBV-C/HGV already exist in Korea; (2) GBV-C/HGV may play some role as an etiologic factor among the Korean patients with liver diseases; (3) GBV-C/HGV infection is rare among Korean general population; and (4) there are at least three different types of GBV-C/HGV in Korea.

Molecular biological characterization of enterovirus variant isolated from patients with aseptic meningitis.

In Korea, there was a big outbreak of aseptic meningitis in 1993. Six clinical isolates of enterovirus were obtained from patients with aseptic meningitis and were identified as echovirus type 9 by serotyping with a pool of neutralizing antisera. For molecular characterization of the isolates, the nucleotide sequences of 5'-noncoding region (NCR), VP4, VP2, VP1, 2A and 2C regions of the isolates were compared with the corresponding regions of echovirus type 9 Hill and Barty strains. Unlike Hill strain, Barty strain contained a C-terminal extension to the capsid protein VP1 with an RGD (argnine-glycine-aspartic acid) motif. To determine whether similar structural features were present in our isolates, their nucleotide sequences including the VP1 region were analyzed. All isolates exhibited the VP1 extension with the RGD motif. We concluded the Korean isolates in the year of 1993 as the echovirus type 9 Barty strain although the isolates showed 15-20% nucleotide sequence differences in the several genomic regions.

Rapid subgrouping of nonpolio enterovirus associated with Aseptic Meningitis by RFLP (Restriction Fragment Length Polymorphism) assay.

In Korea, there was a big outbreak of Aseptic Meningitis due to enterovirus infection in 1993. Since virus isolation and neutralizing tests are too laborious and time-consuming for the detection of enterovirus from clinical specimen, we have developed a new molecular identification method for rapid subgrouping of isolates from patients with aseptic meningitis. For the rapid subgrouping of isolates, RT-PCR (Reverse Transcription-Polymerase Chain Reaction) and RFLP (Restriction Fragment Length Polymorphism) assays were used. We have selected two oligonucleotide primers from the conserved 5'-UTR/VP2 and VP1 regions. A 652 bp (base pair) product was amplified from the 5'-UTR/VP2 region of reference viruses and the isolates. For the subgrouping of the isolates by RFLP assay, we have used 12 reference viruses (Echovirus, E6, E9, E11, E12, Coxsackievirus, CB1, CB3, CB4, CB5, Coxsackievirus, CA9, CA16, CA21, CA24), which are the common viral agents associated with aseptic meningitis. By using subgroup-specific restriction enzymes BsmAI, , HinP1I, and PleI, the isolates were classified into Echovirus subgroups. We have also shown that subgrouping of the isolates by RFLP assay based on the VP1 region is possible.

Isolation and properties of a puromycin acetyltransferase from puromycin-producing Streptomyces alboniger.

Puromycin 2"-N-acetyltransferase was isolated from cell extracts of puromycin-producing Streptomyces alboniger KCC S-0309 by ammonium sulfate fractionation, heat treatment to eliminate contaminant proteins and chromatography on DEAE-Toyopearl 650S. After PAGE (polyacrylamide gel electrophoresis) of the final fraction, a single protein band corresponding to puromycin 2"-N-acetyltransferase was detected. The molecular weight of the enzyme determined by SDS-PAGE and Sephadex G-150 chromatography was about 21,000 and 85,000, respectively, suggesting that the enzyme consisted of four subunits. The isoelectric point and the optimum pH for reaction were 6.2 and 7.7, respectively. The Km values for puromycin and acetyl coenzyme A were 40 microM and 67 microM, respectively. The enzyme was thermostable up to 70 degrees C for 12 minutes. It was shown, by using an in vitro protein synthesizing system from a puromycin-susceptible organism S. flavotricini subsp. pseudochromogenes V-13-1, that the isolated puromycin 2"-N-acetyltransferase could protect polyphenylalanine synthesis from inhibition by puromycin.

Acetylation of blasticidin S by its producing actinomycetes.

A blasticidin S-producing actinomycetes, Streptoverticillium sp. JCM 4673 possesses an enzyme activity which acetylates the drug in the presence of acetyl coenzyme A. The modified drug was biologically inactive when tested against protein synthesis in vivo and in vitro. Production of the enzyme which acetylates blasticidin S increases with formation of the antibiotic during cell growth.

Pleomorphic adenoma of the trachea--a case report.

An unusual tracheal tumor was found in a 50 year old male who was admitted due to mild dyspnea on exertion. Simple chest X-ray showed an abnormal mass shadow in the trachea and computerized chest tomogram revealed a tumor in the mid 1/3 of the trachea obstructing 80% of the lumen. Through a right thoracotomy incision, resection of a 2.5 cm segment of the trachea with end-to-end anastomosis was done and microscopic findings showed many cystic spaces with myxomatous hyalinous stroma. It was diagnosed as a pleomorphic adenoma of the trachea.

Human rotavirus genotypes in hospitalized children, South Korea, April 2005 to March 2007.

Availability of new rotavirus vaccines highlights the need to maintain and enhance rotavirus strain surveillance. We collected stool samples from children with gastroenteritis admitted to eight hospitals in South Korea from April 2005 to March 2007. Of the 6057 samples collected, 1337 (22%) were positive for rotavirus by one of several antigen detection assays. G and P genotypes were identified for 1299 (97%) of rotavirus-positive specimens. G1P[8] (36%) was the most prevalent strain, followed by G3P[8] (16%), G4P[6] (8.9%) and G1P[6] (8.2%). G1P[8] was also the most prevalent strain in each hospital. Seasonal peaks of rotavirus infection were noted from November 2005 to April 2006 and January to March 2007. This large-scale surveillance study provides important insights into rotavirus genotype distribution and pattern changes in South Korea.

Mechanism of self-protection in a puromycin-producing micro-organism.

Puromycin is a potent inhibitor of bacterial protein synthesis, but puromycin-producing Streptomyces alboniger KCC S-0309 is tolerant to the antibiotic in vivo. Puromycin bound to both 30S and 50S ribosomal subunits from S. alboniger and inhibited polyuridylate-directed polyphenylalanine synthesis by the ribosomes. However, the organism possessed a novel puromycin-inactivating enzyme which acetylated the antibiotic at the 2''-NH2 group of the O-methyltyrosine moiety.

Nucleolar organizer regions of lymphomas in Korea.

Nucleolar organizer regions (NORs) are loops of DNA which occur in the nucleoli of cells and which possess ribosomal RNA (rRNA) genes. The numbers and/or configurations of NORs have been thought to be related to cellular activities. To assess the applicability of NORs associated protein (Ag-NORs) in the field of diagnostic histopathology, a silver staining was done in paraffin sections of malignant lymphomas, tonsils and reactive lymph nodes and the numbers of Ag-NORs in the nuclei of low-grade and those of high-grade lymphomas were compared. A significant difference was found between the numbers of Ag-NORs in the nuclei of low-grade lymphoma (a mean of 1.3 per nucleus) and those of high-grade lymphomas (a mean of 4.2 to 8.3 per nucleus). The Ag-NORs were often observed in nuclei in areas where nucleoli themselves were not visible in H&E stain. It is suggested that this method would be of great value in the field of tumor histopathology.