Positive Rate of Antibody Against Dengue Virus for Korean Who Traveled to Dengue Epidemic Area / 감염과화학요법

BACKGROUND: Recently, dengue fever has increased throughout tropical regions and emerged as the most important vector borne viral disease in human. 4 serotypes of viruses are circulating concurrently in these regions and thus it may be anticipated to increase risk of dengue hemorrhagic fever. Even though dengue fever is still not endemic in Korea, it is necessary to test antibodies against dengue viruses because the number of Koreans who have visited these regions is continuously increasing. MATERIALS AND METHODS: Serum specimens from persons with suspected dengue fever had been collected. Commercial kit, immunochromatographic test (ICA), and the IgM capture enzyme-linked immunosorbent assay (MAC-ELISA) were employed for dengue fever detection in these studies. For confirmation randomized 25 specimens among total of 99 specimens were selected and compared with those results from commercial kit and IFA. RESULTS: 33 (33.3%) among 99 specimens showed positive antibody against dengue virus by commercial kit. Positive rate of traveller who have visited Indonesia, Philippines, Malaysia, Thiland was 54.5%. To compare the efficiency of test methods, 25 randomly selected specimens were tested by the MAC-ELISA and IFA simultaneously. 9 specimens showed postive results with the MAC-ELISA method whereas 13 speciments were positive with the IFA methods. CONCLUSION: Confirming the diagnosis of dengue fever with antibody against dengue virus was attempted for the first time in Korea. The results from our study indicate that establishing a national surveillance and/or laboratory diagnostic system in Korea are necessary. In addtion, antibody test strategies for national surveillance system should be carefully considered.

Positive Rate of Antibody Against Dengue Virus for Korean Who Traveled to Dengue Epidemic Area / 감염과화학요법

BACKGROUND: Recently, dengue fever has increased throughout tropical regions and emerged as the most important vector borne viral disease in human. 4 serotypes of viruses are circulating concurrently in these regions and thus it may be anticipated to increase risk of dengue hemorrhagic fever. Even though dengue fever is still not endemic in Korea, it is necessary to test antibodies against dengue viruses because the number of Koreans who have visited these regions is continuously increasing. MATERIALS AND METHODS: Serum specimens from persons with suspected dengue fever had been collected. Commercial kit, immunochromatographic test (ICA), and the IgM capture enzyme-linked immunosorbent assay (MAC-ELISA) were employed for dengue fever detection in these studies. For confirmation randomized 25 specimens among total of 99 specimens were selected and compared with those results from commercial kit and IFA. RESULTS: 33 (33.3%) among 99 specimens showed positive antibody against dengue virus by commercial kit. Positive rate of traveller who have visited Indonesia, Philippines, Malaysia, Thiland was 54.5%. To compare the efficiency of test methods, 25 randomly selected specimens were tested by the MAC-ELISA and IFA simultaneously. 9 specimens showed postive results with the MAC-ELISA method whereas 13 speciments were positive with the IFA methods. CONCLUSION: Confirming the diagnosis of dengue fever with antibody against dengue virus was attempted for the first time in Korea. The results from our study indicate that establishing a national surveillance and/or laboratory diagnostic system in Korea are necessary. In addtion, antibody test strategies for national surveillance system should be carefully considered.

Application of Hantavirus N Protein Expressed by E. coli System

Hantaan viruses cause haemorrhagic fever with renal syndrome (HFRS), resulting in severe morbidity and mortality in humans. The genome of Hantaan virus is composed of three segmented and single stranded negative sense RNA genome. In this study, we expressed nucleocapsid (N) proteins of Hantaan 76-118, Seoul 80-39 and Hantaan virus isolated in Korea (01-23) using E. coli system. These N proteins were fused with a thioredoxin protein for secretion of the expressed protein. The antigenicity of each expressed N proteins was examined in Western blot with sera from HFRS patients and normal controls. The expressed N proteins did not show any cross-reactivity with sera obtained from patients with leptospirosis and tsutsugamushi disease. These results suggest that our recombinant N proteins can be used for the development of diagnostic system to distinguish between HFRS and leptospirosis or tsutsugamushi.

Serologic and Genetic Characterization of Hantavirus from Apodemus Mice Captured in Kyonggi - do and Gangwon - do , 2001

Hantaan virus is widely distributed in Korea and has been known to cause hemorrhagic fever with renal syndrome (HFRS). Hantaviruses are carried by numerous rodent species throughout the world. Especially, the striped field mice, Apodemus agrarius, is natural host for Hantaan virus in Korea. In this study, a total 105 wild rodents of 3 species (101 of Apodemus agrarius, 2 of Eothenomys regulus, and 2 of Mus musculus) were trapped in Kyonggi and Gangwon provinces for April to June, 2001 to study serologic and genetic characterization. 8 Apodemus agrarius (7.9%) were immunofluorescent antibody (IFA) positive against Hantaan virus and Hantaan virus genome was found in 5 among 8 seropositive rodents. S gene of isolated Hantaan virus genome was amplified and directly sequenced. Based on 917 bases of S gene (411-1327 bases), 2001 Korean isolates showed 94.8% to 95.5% nucleotide homologies in comparison with prototype Hantaan virus 76-118 which was isolated from Apodemus agrarius in Korea, 1976. The partial M gene (1969-2240 bases) showed 94.1% to 100.0% nucleotide homologies in comparison with 76-118 strain. In phylogenetic analysis, 2001 Korean isolates made the distinct cluster. Therefore, Hantaan viruses isolated in 2001 were not significantly chinged in genetic level comparison with previous isolate from Korea.

The Role of Noncoding Region in Hantaan Viral S Genome for Expression of Nucleocapsid Protein

The genome of Hantaan virus, the prototype of the hantavirus genus, is composed of three segmented, single stranded negative sense RNA genome. The 5' and 3' termini of the Hantaan virus RNA genome contain noncoding regions (NCRs) that are highly conserved and complementary to form panhandle stuctures. There are some reports that these NCRs seems to control gene expression and viral replication in influenza virus and vesicular stomatitis virus. In this study, we examined whether NCRs in Hantaan virus play a role in expression of the viral nucleocapsid protein (Np) and foreign (luciferase) gene. The 5' and/or 3' NCR-deleted mutants were constructed and analysed. The Np expression of 5' NCR-deleted clone, it showed 40% reduction. To investigate the role of NCR in foreign gene expression, the clones which are replaced ORF of Hantaan viral Np gene with that of luciferase gene were constructed. The results were similar to those of the experiments using Np gene. These results suggest that 3' NCR is more important than 5' NCR in protein expression. To find out a critical region of 3' NCR in more important than 5' NCR in protein expression. To find out a critical region of 3' NCR in protein expression, several clones with a deleted part of 3' NCR were constructed and analyzed. The deletion of the conserved region in 3' NCR showed 20~30% decrease in Np expression. However there were no change in luciferase activities between clones with or without non-conserved region of 3' NCR. These results suggest that the 3' NCR of Hantaan virus S genome, especially conserved region in 3' NCR, plays and important role in the expression of Hantaan viral Np and foreign genes.