Epidemiology of Murine Typhus in Taiwan from 2013 to 2020.

Murine typhus is a flea-borne disease caused by Rickettsia typhi infection. The disease is a notifiable infectious disease in Taiwan. Specimens from suspected cases are required to be sent to the Taiwan Centers for Disease Control and Prevention for laboratory diagnosis. In this study, 204 cases of murine typhus were identified by bacterial isolation, real-time polymerase chain reaction, or indirect immunofluorescence assay between 2013 and 2020. The average incidence rate was 0.11/100,000 person-years (95% CI: 0.08-0.13). Murine typhus occurred throughout the year, but it was most prevalent in summer (May to August). The majority of patients were males (75%), residents of Kaohsiung city (31%), and worked in agriculture, forestry, fishing, and animal husbandry (27%). Fever was the most common symptom, present in 95.6% of patients, followed by headache (41%), myalgia (33%), and liver dysfunction (33%). Only 13% of patients had a rash. Up to 80% of cases were among hospitalized patients, and 43% of patients developed severe manifestations. Serological assays also indicated coinfection events. Seven patients showed a 4-fold increase in antibody titers against Orientia tsutsugamushi (N = 2), Coxiella burnetii (n = 2), and Leptospira (N = 3). In conclusion, murine typhus is an endemic and important zoonotic rickettsial disease in Taiwan that cannot be ignored. Further epidemiological surveillance and clinical characteristics should be continuously investigated to prevent and control murine typhus.

Genome Analysis of a Novel Tembusu Virus in Taiwan.

We identified and isolated a novel Tembusu virus (TMUV) strain TP1906 (TMUV-TP1906) from a Culexannulus mosquito pool collected from the northern part of Taiwan in 2019. The TMUV-TP1906 genome is a 10,990-nucleotide-long, positive-sense, single-stranded RNA, consisting of a single open reading frame (ORF) encoding a polyprotein of 3425 amino acids, with 5' and 3' untranslated regions (UTRs) of 94 and 618 nucleotides, respectively. The nucleotide sequence of the TMUV-TP1906 of ORF exhibited 93.71% and 91.27% similarity with Sitiawan virus (STWV) and the TMUV prototype strain MM1775, respectively. The 3'-UTR variable region of TMUV-TP1906 showed nucleotide sequence divergence with other TMUV strains. Phylogenetic analysis of the complete ORF and polyprotein sequences revealed that TMUV-TP1906 is most closely related to STWV which causes encephalitis and retarded growth in chickens. We found that the TMUV-TP1906 caused a cytopathic effect (CPE) in the DF-1 chicken fibroblast cell line, while no apparent CPE was observed in Vero and C6/36 cells. In this study, we first identified and isolated a novel TMUV strain in Taiwan. In addition, to our knowledge, it is the first time that the TMUV strain was isolated from the Cx. annulus mosquitoes. Further study is warranted to investigate the host range and virulence of TMUV-TP1906.

Concurrent isolation of chikungunya virus and dengue virus from a patient with coinfection resulting from a trip to Singapore.

We report two cases of imported infection in patients who had returned to Taiwan from Singapore: one was coinfected with chikungunya virus and dengue virus type 2, and the other was infected with the same dengue virus. Both viruses were successfully isolated from the coinfected case by using antibody neutralization and a plaque purification technique.

Phylogenetic analysis of 56-kDa type-specific antigen gene of Orientia tsutsugamushi isolates in Taiwan.

Scrub typhus is a rickettsial disease transmitted to humans through the bite of chigger mites infected with Orientia tsutsugamushi, and is an endemic disease in Taiwan. To elucidate the molecular epidemiology of O. tsutsugamushi, the complete open reading frame of the 56-kDa type-specific antigen gene sequence of strains isolated from scrub typhus patients were determined and analyzed. A total of 116 isolates of O. tsutsugamushi were successfully isolated from patients infected in diverse geographic origins including Taiwan and three offshore islets, Kinmen, Matsu, and Penghu between May 2006 and December 2007. Sequence analysis revealed that 22 distinct sequence types could be identified that were broadly distributed in different clusters of the phylogenetic tree. Most of the isolates belong to Karp, Kawasaki, and Kuroki genotypes and are closely related to strains from Thailand, Japan, and Korea, whereas unique isolates different from other countries were also found in Taiwan. Distinct seasonal distributions were found in different sequence types. Some sequence types caused disease in the cold season, whereas others caused disease in the warm season.

Oxaliplatin down-regulates survivin by p38 MAP kinase and proteasome in human colon cancer cells.

Oxaliplatin, a platinum derivative cancer drug, has been used for treating human colorectal cancers. Survivin has been proposed as a cancer target, which highly expressed in most cancer cells but not normal adult cells. In this study, we investigated the regulation of survivin expression by exposure to oxaliplatin in human colon cancer cells. Oxaliplatin (3-9µM for 24h) markedly induced cytotoxicity, proliferation inhibition and apoptosis in the human RKO colon cancer cells. The survivin protein expression of RKO cells is dramatically reduced by oxaliplatin; however, the survivin gene expression is slightly altered. The survivin blockage of oxaliplatin elevated caspase-3 activation and apoptosis in RKO cells. Over-expression of survivin proteins by transfection with a survivin-expressed vector resisted the oxaliplatin-induced cancer cell death. Meantime, oxaliplatin elicited the phosphorylation of p38 mitogen-activated protein (MAP) kinase. SB202190, a specific p38 MAP kinase inhibitor, restored the survivin protein level and attenuated oxaliplatin-induced cancer cell death. In addition, oxaliplatin increased the levels of phospho-p53 (Ser-15) and total p53 proteins. Inhibition of p53 expression by a specific p53 inhibitor pifithrin-α reduced the phosphorylated p38 MAP kinase and active caspase-3 proteins in the oxaliplatin-exposed RKO cells. In contrast, SB202190 did not alter the oxaliplatin-induced p53 protein level. Furthermore, treatment with a specific proteasome inhibitor MG132 restored survivin protein level in the oxaliplatin-treated colon cancer cells. Taken together, our results demonstrate for the first time that survivin is down-regulated by p38 MAP kinase and proteasome degradation pathway after treatment with oxaliplatin in the human colon cancer cells.

Molecular characterization of dengue viruses imported into Taiwan during 2003-2007: geographic distribution and genotype shift.

We presented our surveillance results on imported dengue cases in Taiwan during 2003-2007. A total of 542 imported dengue patients were identified. The travelers were infected in 17 countries in Southeast Asia, the Indian subcontinent, East African islands, South Pacific islands, and Central America. Most of these imported cases were infected in Southeast Asian countries. Phylogenetic analyses were conducted to examine 288 imported dengue virus (DENV) strains introduced from 13 countries. The results provide an updated view on the geographic distribution and dynamic transmission of epidemic DENV stains circulated in Southeast Asian countries. Although the geographic distributions of genotypes of DENV-3 isolated from Southeast Asian countries remain unchanged, the introductions and local expansions of epidemic DENV-1, DENV-2, and DENV-4 strains into new areas in Asia were observed. These findings highlight the importance to strengthen laboratory-based dengue surveillance for better understanding of transmission dynamics and molecular evolution of DENVs.

Natriuretic peptides cause relaxation of human and guinea-pig gallbladder muscle through interaction with natriuretic peptide receptor-B.

Atrial natriuretic peptide (ANP) binding sites have been demonstrated in the guinea-pig gallbladder muscle with unclear function. To investigate effects of natriuretic peptides in the gallbladder, we measured relaxation of isolated human and guinea-pig gallbladder strips caused by natriuretic peptides, including C-type natriuretic peptide (CNP), brain natriuretic peptide (BNP) and ANP, as well as des[Gln18, Ser19, Gly20, Leu21, Gly22]ANP(4-23) amide (cANP(4-23)), a selective natriuretic peptide receptor-C (NPR-C) agonist. Results in the human gallbladder were similar to those in the guinea-pig gallbladder. CNP, BNP, ANP and cANP(4-23) alone did not cause contraction or relaxation in resting gallbladder strips. However, in carbachol or endothelin-1-contracted strips, CNP caused moderate, sustained and concentration-dependent relaxation. The relaxation was not affected by tetrodotoxin or atropine in endothelin-1-contracted gallbladder strips and not by tetrodotoxin in carbachol-contracted strips. These indicate a direct effect of CNP on the gallbladder muscle. The relative potencies for natriuretic peptides to cause relaxation were CNP>>BNP> or = ANP. cANP(4-23) did not cause relaxation. These indicate the existence of the natriuretic peptide receptor-B (NPR-B) mediating the relaxation. Taken together, these results demonstrate that natriuretic peptides cause relaxation of human and guinea-pig gallbladder muscle through interaction with the natriuretic peptide receptor-B.