Mutation screening in KCNQ1, HERG, KCNE1, KCNE2 and SCN5A genes in a long QT syndrome family.

INTRODUCTION: Long QT syndrome (LQTS), an inherited cardiac arrhythmia, is a disorder of ventricular repolarisation characterised by electrocardiographic abnormalities and the onset of torsades de pointes leading to syncope and sudden death. Genetic polymorphisms in 5 well-characterised cardiac ion channel genes have been identified to be responsible for the disorder. The aim of this study is to identify disease-causing mutations in these candidate genes in a LQTS family. MATERIALS AND METHODS: The present study systematically screens the coding region of the LQTS-associated genes (KCNQ1, HERG, KCNE1, KCNE2 and SCN5A) for mutations using DNA sequencing analysis. RESULTS: The mutational analysis revealed 7 synonymous and 2 non-synonymous polymorphisms in the 5 ion channel genes screened. CONCLUSION: We did not identify any clear identifiable genetic marker causative of LQTS, suggesting the existence of LQTS-associated genes awaiting discovery.

Host heterogeneous ribonucleoprotein K (hnRNP K) as a potential target to suppress hepatitis B virus replication.

BACKGROUND: Hepatitis B virus (HBV) infection results in complications such as cirrhosis and hepatocellular carcinoma. Suppressing viral replication in chronic HBV carriers is an effective approach to controlling disease progression. Although antiviral compounds are available, we aimed to identify host factors that have a significant effect on viral replication efficiency. METHODS AND FINDINGS: We studied a group of hepatitis B carriers by associating serum viral load with their respective HBV genomes, and observed a significant association between high patient serum viral load with a natural sequence variant within the HBV enhancer II (Enh II) regulatory region at position 1752. Using a viral fragment as an affinity binding probe, we isolated a host DNA-binding protein belonging to the class of heterogeneous nuclear ribonucleoproteins--hnRNP K--that binds to and modulates the replicative efficiency of HBV. In cell transfection studies, overexpression of hnRNP K augmented HBV replication, while gene silencing of endogenous hnRNP K carried out by small interfering RNAs resulted in a significant reduction of HBV viral load. CONCLUSION: The evidence presented in this study describes a wider role for hnRNP K beyond maintenance of host cellular functions and may represent a novel target for pharmacologic intervention of HBV replication.

Identification of CD8+ T-cell epitopes specific for immediate-early transactivator Rta of Epstein-Barr virus.

Nasopharyngeal carcinoma (NPC) is a human epithelial tumor with a high incidence in Southern Chinese population, with contributions from Epstein-Barr virus (EBV), human leukocyte antigen (HLA), and environmental factors to its etiology. It has been shown previously that the recognition of immediate-early transactivator Rta of EBV by CD8+ T cells may have a significant impact on controlling EBV and, indirectly, NPC. The current study used two computer-aided prediction methods and competition-based HLA-peptide binding assays to screen for HLA B2704/B4601/B5801 restricted T-cell epitopes derived from Rta. HLA tetrameric complexes containing these potential T-cell epitopes were synthesized. Rta-specific CD8+ T-cell responses in healthy virus carriers were then defined by these tetramers and IFN-gamma ELISPOT assays. We clearly demonstrated that healthy virus carriers have detectable Rta-specific CD8+ T cells restricted by B2704 in the circulation. However, there were no B4601/B5801 tetramer-reactive T cells specific for Rta in the peripheral blood of matched/mismatched donors. On the other hand, B4601 tetramers containing the computer-predicted B4601 binder EBNA3A (318-326) showed detectable tetramer-reactive T cells in the circulation of healthy virus carriers. topes also elicited IFN-gamma responses as detected by ELISPOT.

Seroepidemiology of human enterovirus 71, Singapore.

Human enterovirus 71 has caused outbreaks in many parts of the world, especially Southeast Asia, with some fatal cases. The epidemiology of this viral infection is not well understood. We conducted a serologic survey in Singapore children, and the results indicate that infection occurs largely in preschool settings.

Increased HLA- A*11 in Chinese children with steroid-responsive nephrotic syndrome.

Human leukocyte antigen (HLA) associations have been frequently reported in childhood steroid-responsive nephrotic syndrome (SRNS) in other populations. The aim of this study was to characterize the immunogenetic background of Singaporean Chinese patients with childhood SRNS. We determined the HLA class I (HLA- A* and HLA-B*) as well as class II (HLA- DRB1*, HLA- DQB1*) gene polymorphisms using the polymerase chain reaction-sequence specific oligonucleotide (PCR-SSO) technique, in patients with SRNS (n=64) and normal controls (n=236 for HLA- A*, n=80 for HLA- B*, HLA- DRB1* and HLA- DQB1*). The frequency of HLA- A*11 allele was significantly higher in the SRNS patients compared to controls (78.1% vs 54.2%, respectively; relative risk, RR=3.01, Pc=0.011). However, there was no significant difference in the allele frequencies of HLA- B*, HLA- DRB1* and HLA- DQB1* between the SRNS patients and controls, unlike that in previous studies. Our data suggest that the immunogenetic background of Singaporean Chinese with childhood SRNS was different from that in other populations. As HLA- A*11 has been strongly associated with other autoimmune diseases, it is conceivable that the HLA- A*11-specific motif may play a role in the development of the abnormal T-cell-mediated immune response that may be responsible for triggering the proteinuria seen in SRNS.

HLA association in Singapore children with Grave's disease.

HLA associations in patients with Grave's disease are B8 in whites and BW35 in Japanese. This study shows the HLA association of Singapore Chinese children with Grave's disease. Forty unrelated Chinese children with Grave's disease were typed. The control population consisted of 238 consecutive unrelated normal Chinese individuals. Patients with Grave's disease showed a significantly higher frequency of BW46 than control subjects (corrected P = .0005, relative risk (RR) = 4.61). Only two patients had BW35 and none had B8. There was an increased frequency of both homozygotes and heterozygotes in thyrotoxic patients compared with controls, the RR being slightly higher in the homozygotes. Among the patients, BW46 was most frequently associated with B40, B13, and B15. The joint occurrence of BW46/B40 in thyrotoxic children had a lower relative risk than BW46 alone, whereas the joint occurrence of BW46/B13 had a higher relative risk than BW46 alone.