Jungsang Ryou

Severe Fever with Thrombocytopenia Syndrome Virus in Ticks Collected from Humans, South Korea, 2013

We investigated the infection rate for severe fever with thrombocytopenia syndrome virus (SFTSV) among ticks collected from humans during May–October 2013 in South Korea. Haemaphysalis longicornis ticks have been considered the SFTSV vector. However, we detected the virus in H. longicornis, Amblyomma testudinarium, and Ixodes nipponensis ticks, indicating additional potential SFTSV vectors.

Prevalence of severe fever with thrombocytopenia syndrome virus in Haemaphysalis longicornis ticks in South Korea.

Haemaphysalis longicornis a vector that harbors severe fever with thrombocytopenia syndrome virus (SFTSV) is a major species of tick in South Korea. To investigate the existence and prevalence of SFTSV in Korea, we collected ticks from nine provinces in South Korea for detecting SFTSV. In all, we collected 13,053 ticks, and H. longicornis (90.8%, 11,856/13,053) was the most abundant among them. The minimum infection rate (MIR) of SFTSV in H. longicornis was 0.46% (55 pools). SFTSV was detected in ticks during all the developmental stages, showing MIR in larvae (2/350, 0.57%), nymphs (38/10,436, 0.36%), males (2/221, 0.90%), and females (13/849, 1.53%), respectively. Viruses were detected in ticks collected between April and September. A higher MIR was detected in ticks from the southern part of the country. We amplified the M and S segment partial genes from a sample and analyzed the nucleotide sequence. The results showed a 93-98% homology to Chinese and Japanese strains registered in Genbank. In this study, we confirmed the existence of SFTSV for the first time in South Korea. The SFTSV prevalence data from the studies are essential for raising the awareness of SFTS in South Korea.

Molecular epidemiology of Japanese encephalitis virus circulating in South Korea, 1983-2005

We sequenced the envelope (E) gene of 17 strains of the Japanese encephalitis virus (JEV) isolated in South Korea in 1983-2005 and compared the sequences with those from previously reported strains. Our results show the remarkable genetic stability of the E gene sequence in Korean JEV strains. Five pairs of E gene sequences from 10 Korean strains were identical, despite geographical differences and a maximum five-year time span. Sequence comparisons with other Asian strains revealed that the Korean strains are closely related to those from China, Japan, and Vietnam. Genotype 3 strains were predominant in Korea before 1993, when genotype 1 strain K93A07 was first isolated. The two genotypes were detected simultaneously in 1994 but since then, only genotype 1 has been isolated in South Korea. Thus, the genotype change occurred according to the year of isolation rather than the geographical origin.

Severe fever with thrombocytopenia syndrome virus, South Korea, 2013.

During 2013, severe fever with thrombocytopenia syndrome was diagnosed in 35 persons in South Korea. Environmental temperature probably affected the monthly and regional distribution of case-patients within the country. Phylogenetic analysis indicated that the isolates from Korea were closely related to isolates from China and Japan.

Prevalence of Tick-Borne Encephalitis Virus in Ixodid Ticks Collected from the Republic of Korea During 2011–2012

Objectives In this study, we demonstrated that TBEV-infected ticks have been distributed in the ROK, combined with our previous results. These results suggest that TBEV may exist in the ROK, and H. longicornis, H. flava, and I. nipponensis may be potential vectors of TBEV. In addition, these results emphasize the need for further epidemiological research of TBEV. Methods We examined for the presence of RNA of TBEV by reverse transcriptase-nested polymerase chain reaction (RT-nested PCR) using ixodid ticks captured in 25 localities of 10 provinces. Ticks were collected by the flagging and dragging method or using sentinel BG traps at forests, grass thickets, and grassland. A total of 13,053 ticks belonging to two genera and four species were collected and pooled (1292 pools), according to collection site, species of tick, and developmental stage. Results Among 1292 pools, the envelope (E) protein gene of TBEV was detected using RT-nested PCR in 10 pools (3 pools of the 1,331 adult ticks and 7 pools of the 11,169 nymph ticks) collected from Gangwon-do province, Jeonrabuk-do province, and Jeju Island. The minimum infection rates for TBEV of Haemaphysalis longicornis, Haemaphysalis flava, and Ixodes nipponensis were 0.06%, 0.17%, and 2.38%, respectively. Phylogenetic analysis based on the partial E protein gene was performed to identify relationships between the TBEV strains. This showed that 10 Korean strains clustered with the Western subtype. Conclusion In this study, we investigated the prevalence of tick-borne encephalitis virus (TBEV) in ixodid ticks from various regions of the Republic of Korea (ROK) during 2011–2012 to identify whether TBEV is circulating and to determine the endemic regions of TBEV.

Hantaan virus nucleocapsid protein stimulates MDM2-dependent p53 degradation.

Apoptosis has been shown to be induced and downregulated by the Hantaan virus (HTNV) nucleocapsid (N) protein. To address these conflicting data, expression of the p53 protein, one of the key molecules involved in apoptosis, was assessed in the presence of the N protein in A549 and HeLa cells. The amount of p53, increased by drug treatment, was reduced when cells were infected with HTNV or transfected with an expression vector of the HTNV N protein. When cells were treated with a proteasome inhibitor (MG132) or an MDM2 antagonist (Nutlin-3), p53 expression was not reduced in N protein-overexpressed cells. We concluded that the HTNV N protein ubiquitinates and degrades p53 MDM2-dependently. Here we report downregulation of p53 expression through a post-translational mechanism: MDM2-dependent ubiquitination and degradation by the HTNV N protein. These results indicate that N protein-dependent p53 degradation through the ubiquitin proteasome system is one of the anti-apoptotic mechanisms employed by HTNV.

PREVALENCE OF HANTAVIRUS INFECTION IN WILD RODENTS FROM FIVE PROVINCES IN KOREA, 2007

Hemorrhagic fever with renal syndrome (HFRS) is an infectious disease caused by hantaviruses of the family Bunyaviridae. Among them, Hantaan virus (HTNV) is most widely distributed in Korea. The striped field mouse, Apodemus agrarius, is the natural host of HTNV in rural Korea. We trapped 766 small mammals of three species (1 Eothenomys regulus, 13 Crocidura suaveolens, and 752 Apodemus agrarius) in five provinces in Korea from January to December 2007. We tested 542 rodent sera for HTNV antibodies by an indirect immunofluorescent assay (IFA), finding antibody prevalences of 4 to 29% among the five provinces. Peaks in monthly antibody prevalence occurred in spring and fall. Antibody prevalence during the second peak coincided increased HFRS incidence in autumn. We used multiplex reverse transcription polymerase chain reaction (RT-PCR) to detect the partial S segment of Hantaan, Seoul, and Puumala viruses in 766 lung samples of all captured animals and found HTNV RNA in 25 A. agrarius. Two isolates of HTNV were obtained from PCR-positive A. agrarius by cultivation in Vero E6 cells. This first systemic survey of monthly antibody prevalence in hantavirus hosts in wide regions in Korea could provide useful information for other researchers studying environmental and ecological factors affecting HFRS.

Seroprevalence of hantaviruses in small wild mammals trapped in South Korea from 2005 to 2010

ABSTRACT: The seroprevalence of Hantaan virus (HTNV) in wild rodents in South Korea was analyzed. Wild rodents were trapped in 18 cities in eight provinces during 2005–2007 and on three islands and four mountains during 2008–2010. Sera were collected from 629 out of 933 trapped wild animals and examined for immunoglobulin G antibodies to HTNV using indirect immunofluorescence assays. Apodemus agrarius (80.1%) was the most frequently captured species at almost all trapping sites. The overall prevalence of HTNV antibodies was 0.26 (162/629). Seropositive individuals were more frequent in cities (32.2%, n=410) than on islands (14.0%, n=57) or mountains (13.6%, n= 162). HTNV antibody-positive rate was higher in the fall (29.6%, n=253) than in the spring (23.1%, n=376). A. agrarius had the highest prevalence of HTNV antibodies (26.9%, n=561) of all tested species. Considering all the individuals, the prevalence of HTNV antibodies was higher in males (29.2%, n=250) than in females (22.3%, n=305). Our results show that HTNV is widely distributed throughout South Korea, and that HTNV infection of wild rodents is affected by their habitat, species, sex, and season.