Serological Evidence of Severe Fever with Thrombocytopenia Syndrome Virus and IgM Positivity Were Identified in Healthy Residents in Vietnam

Severe fever with thrombocytopenia syndrome (SFTS), an emerging tick-borne viral disease, is prevalent in East Asia and has also been reported in Southeast Asia since 2019. SFTS patients in Vietnam were first reported in 2019. However, the seroprevalence of severe fever with thrombocytopenia syndrome virus (SFTSV) in Vietnam has not been reported. To investigate the seroprevalence of SFTSV in Vietnam, we collected serum samples from 714 healthy residents in Thua Thien Hue and Quang Nam Province, Vietnam, and the seroprevalence of SFTSV was assessed using immunofluorescence antibody assay (IFA), Enzyme-Linked Immunosorbent Assays (ELISAs) and the 50% focus reduction neutralization test (FRNT50) assay. The seroprevalence of anti-SFTSV IgM or IgG was observed to be 3.64% (26/714), high IgM positivity was >80 (0.28%, 2/714) and the titer of neutralizing antibodies against SFTSV ranged from 15.5 to 55.9. In Pakistan, SFTSV infection confirmed using a microneutralization test (MNT) assay (prevalence is 2.5%) and ELISAs showed a high seroprevalence (46.7%) of SFTSV. Hence, the seroprevalence rate in Vietnam is similar to that in Pakistan and the number of SFTS patients could increase in Vietnam.

Viral and Immunologic Factors Associated with Fatal Outcome of Patients with Severe Fever with Thrombocytopenia Syndrome in Korea

Significant progress has been made on the molecular biology of the severe fever with thrombopenia virus (SFTSV); however, many parts of the pathophysiological mechanisms of mortality in SFTS remain unclear. In this study, we investigated virologic and immunologic factors for fatal outcomes of patients with SFTS. We prospectively enrolled SFTS patients admitted from July 2015 to October 2020. Plasma samples were subjected to SFTSV RNA RT-PCR, multiplex microbead immunoassay for 17 cytokines, and IFA assay. A total of 44 SFTS patients were enrolled, including 37 (84.1%) survivors and 7 (15.9%) non-survivors. Non-survivors had a 2.5 times higher plasma SFTSV load than survivors at admission (p < 0.001), and the viral load in non-survivors increased progressively during hospitalization. In addition, non-survivors did not develop adequate anti-SFTSV IgG, whereas survivors exhibited anti-SFTSV IgG during hospitalization. IFN-α, IL-10, IP-10, IFN-γ, IL-6, IL-8, MCP-1, MIP-1α, and G-CSF were significantly elevated in non-survivors compared to survivors and did not revert to normal ranges during hospitalization (p < 0.05). Severe signs of inflammation such as a high plasma concentration of IFN-α, IL-10, IP-10, IFN-γ, IL-6, IL-8, MCP-1, MIP-1α, and G-CSF, poor viral control, and inadequate antibody response during the disease course were associated with mortality in SFTS patients.

Yes-Associated Protein Is Required for ZO-1-Mediated Tight-Junction Integrity and Cell Migration in E-Cadherin-Restored AGS Gastric Cancer Cells

Yes-associated protein (YAP) regulates numerous cellular homeostasis processes and malignant transformation. We found that YAP influences ZO-1-mediated cell migration using E-cadherin-restored EC96 cells derived from gastric malignant AGS cells. Ectopic expression of E-cadherin enhanced straightforward migration of cells, in comparison to the meandering movement of parental AGS cells. In EC96 cells, YAP and ZO-1 expression increased but nuclear YAP levels and activity were reduced. Nuclear factor-κB (NF-κB) mediated the increase in ZO-1 expression, possibly stabilizing cytoplasmic YAP post-translationally. Downregulation of YAP expression using siYAP RNA or stable knock-down inhibited straightforward cell migration by fragmenting ZO-1 containing tight junctions (TJs) but not adherens junctions, implying involvement of YAP in ZO-1-mediated cell migration. The association of YAP with ZO-1 was mediated by angiomotin (AMOT) because downregulation of AMOT dissociated YAP from ZO-1 and reduced cell migration. E-cadherin restoration in malignant cancer cells induced NF-κB signaling to enhance ZO-1 expression and subsequently stabilize YAP. At high expression levels, YAP associates with ZO-1 via AMOT at TJs, influencing ZO-1-mediated cell migration and maintaining TJ integrity.

Severe Fever with Thrombocytopenia Syndrome Virus in Ticks and SFTS Incidence in Humans, South Korea

During 2016–2018, we collected 3,193 ticks from rural areas in South Korea to investigate the prevalence of severe fever with thrombocytopenia syndrome virus (SFTSV). We detected SFTSV in ticks at an infection rate (IR) of 11.1%. We noted increases in the human IR associated with the monthly SFTSV IR in ticks.

Familial risk of Behçet's disease among first-degree relatives: a population-based aggregation study in Korea

OBJECTIVE

Previous studies have indicated that Behçet's disease (BD) has a genetic component, however population-level familial risk estimates are unavailable. We quantified the familial incidence and risk of BD in first-degree relatives (FDR) according to age, sex and type of family relationship.

METHODS

Using the Korean National Health Insurance database, which has full population coverage and confirmed FDR information, we constructed a cohort of 21 940 795 individuals comprising 12 million families, which were followed for a familial occurrence of BD from 2002 to 2017. Age- and sex-adjusted incidence risk ratios for BD were calculated in individuals with affected FDR compared with those without affected FDR.

RESULTS

Among the total study population, 53 687 individuals had affected FDR, of whom 284 familial cases developed BD with an incidence of 3.57/104 person-years. The familial risk (incidence) for BD was increased to 13.1-fold (2.71/104 person-years) in individuals with an affected father, 13.9-fold (3.11/104 person-years) with affected mother, 15.2-fold (4.9/104 person-years) with an affected sibling and the highest risk was 165-fold (46/104 person-years) with an affected twin. Familial risks showed age dependence, being higher in younger age groups. The sex-specific familial risk was similar in males and females.

CONCLUSION

This study provides quantified estimates of familial incidence and risk in FDR of BD patients in an entire population. Familial risks were higher within generation (sibling-sibling) vs between generations (parent-offspring). This implicates complex interactions between genetic factors and shared childhood environmental exposures in the pathogenesis of BD.

Expression of E-Cadherin in Epithelial Cancer Cells Increases Cell Motility and Directionality through the Localization of ZO-1 during Collective Cell Migration

Collective cell migration of epithelial tumor cells is one of the important factors for elucidating cancer metastasis and developing novel drugs for cancer treatment. Especially, new roles of E-cadherin in cancer migration and metastasis, beyond the epithelial–mesenchymal transition, have recently been unveiled. Here, we quantitatively examined cell motility using micropatterned free edge migration model with E-cadherin re-expressing EC96 cells derived from adenocarcinoma gastric (AGS) cell line. EC96 cells showed increased migration features such as the expansion of cell islands and straightforward movement compared to AGS cells. The function of tight junction proteins known to E-cadherin expression were evaluated for cell migration by knockdown using sh-RNA. Cell migration and straight movement of EC96 cells were reduced by knockdown of ZO-1 and claudin-7, to a lesser degree. Analysis of the migratory activity of boundary cells and inner cells shows that EC96 cell migration was primarily conducted by boundary cells, similar to leader cells in collective migration. Immunofluorescence analysis showed that tight junctions (TJs) of EC96 cells might play important roles in intracellular communication among boundary cells. ZO-1 is localized to the base of protruding lamellipodia and cell contact sites at the rear of cells, indicating that ZO-1 might be important for the interaction between traction and tensile forces. Overall, dynamic regulation of E-cadherin expression and localization by interaction with ZO-1 protein is one of the targets for elucidating the mechanism of collective migration of cancer metastasis.

Kinetics of Serological Response in Patients with Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is caused by SFTS virus (SFTSV). We investigated the detailed kinetics of serologic response in patients with SFTS. Twenty-eight patients aged ≥18 years were enrolled between July 2015 and October 2018. SFTS was confirmed by detecting SFTSV RNA in their plasma using reverse transcription polymerase chain reaction. SFTSV-specific IgG and IgM were measured using immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA). We found that SFTSV-specific IgG was detected at days 5–9 after symptom onset, and its titer was rising during the course of disease. SFTSV-specific IgM titer peaked at around week 2–3 from symptom onset. The SFTSV-specific seropositive rates for days 5–9, 10–14, 15–19, and 20–24 from symptom onset using IFA and ELISA were 63%, 76%, 90%, and 100%, and 58%, 86%, 100%, and 100%, respectively, for IgG, whereas they were 32%, 62%, 80%, and 100%, and 53%, 62%, 70%, and 100%, respectively, for IgM. The delayed IgM response could be attributed to the low sensitivity of SFTSV-specific IgM IFA or ELISA and/or impaired immune responses. The IgM test using IFA or ELISA that we used in this study is, therefore, insufficient for the early diagnosis of SFTS.

Capsaicin induces atopic dermatitis-like manifestations through dysregulation of proteolytic system and alteration of filaggrin processing in rats

Atopic dermatitis (AD) is a complex disease featuring pruritic skin inflammation. Many animal models have been developed. In a rat model, subcutaneous capsaicin injection within 48 hours after birth induces AD-like skin manifestations of dermatitis and scratching behaviour 3 weeks after the injection. When 2- to 4-week-old rats were injected with capsaicin, the lag period was shortened, and the severity of skin manifestations was significantly reduced, suggesting influences of postnatal development. Lgr6 is an epidermal stem cell marker that is normally restricted to the isthmus area of hair follicles at postnatal 2 weeks. Lgr6 persisted in the interfollicular epidermis of capsaicin-injected rats beyond 3 weeks after birth, indicating that capsaicin-induced skin manifestations were influenced by postnatal epidermal development. Capsaicin injection induced alteration of proteolytic processing of filaggrin and corneodesmosin, suggesting epidermal barrier dysfunction. Inappropriate degradation of matriptase was observed. Degrees of proteolysis of these proteins were corelated with the severity of manifestations, suggesting that inappropriate proteolysis might be a possible cause of the skin manifestations. These results strongly suggest that capsaicin may dysregulate the protease system, resulting in alteration of profilaggrin and corneodesmosin proteolysis and skin manifestations. These events may be influenced by postnatal epidermal development.

Metformin-activated AMPK regulates β-catenin to reduce cell proliferation in colon carcinoma RKO cells

Metformin can suppress cell proliferation and viability by altering mitochondrial energy metabolism and by the activation of 5′-adenosine monophosphate-activated protein kinase (AMPK). The current study demonstrated that metformin-induced suppression of cell proliferation is further potentiated by AMPK-mediated suppression of β-catenin-dependent wingless-type (Wnt) signaling. Treatment with metformin reduced mitochondrial oxidative phosphorylation and glycolysis, leading to an energy imbalance that may induce AMPK phosphorylation in RKO cells. Metformin treatment also decreased β-catenin expression in the cytoplasm and nucleus. Active AMPK was revealed to be associated with β-catenin. The decrease in β-catenin expression was inhibited by proteosome inhibition through phosphorylation of β-catenin at serine 33/37. Given that nuclear translocation-associated phosphorylation of β-catenin at serine was maintained, the association of β-catenin with AMPK may sequester β-catenin in the cytoplasm and lead to proteosomal degradation. Furthermore, metformin-induced suppression of cell proliferation was partially recovered by AMPK inhibition, while metformin inhibited Wnt-mediated cell proliferation and β-catenin expression. The present results suggest that AMPK activation can suppress β-catenin-dependent Wnt signaling by cytoplasmic sequestering of β-catenin through AMPK, which further decreases cell proliferation in addition to metformin-induced mitochondrial dysfunction.

Adaptive mutations of neuraminidase stalk truncation and deglycosylation confer enhanced pathogenicity of influenza A viruses

It has been noticed that neuraminidase (NA) stalk truncation has arisen from evolutionary adaptation of avian influenza A viruses (IAVs) from wild aquatic birds to domestic poultry. We identified this molecular alteration after the adaptation of a 2009 pandemic H1N1 virus (pH1N1) in BALB/c mice. The mouse-adapted pH1N1 lost its eight consecutive amino acids including one potential N-linked glycosite from the NA stalk region. To explore the relationship of NA stalk truncation or deglycosylation with viral pathogenicity changes, we generated NA stalk mutant viruses on the pH1N1 backbone by reverse genetics. Intriguingly, either NA stalk truncation or deglycosylation changed pH1N1 into a lethal virus to mice by resulting in extensive pathologic transformation in the mouse lungs and systemic infection affecting beyond the respiratory organs in mice. The increased pathogenicity of these NA stalk mutants was also reproduced in ferrets. In further investigation using a human-infecting H7N9 avian IAV strain, NA stalk truncation or deglycosylation enhanced the replication property and pathogenicity of H7N9 NA stalk mutant viruses in the same mouse model. Taken together, our results suggest that NA stalk truncation or deglycosylation can be the pathogenic determinants of seasonal influenza viruses associated with the evolutionary adaptation of IAVs.

E-cadherin expression increases cell proliferation by regulating energy metabolism through nuclear factor-κB in AGS cells

β-Catenin is a central player in Wnt signaling, and activation of Wnt signaling is associated with cancer development. E-cadherin in complex with β-catenin mediates cell-cell adhesion, which suppresses β-catenin-dependent Wnt signaling. Recently, a tumor-suppressive role for E-cadherin has been reconsidered, as re-expression of E-cadherin was reported to enhance the metastatic potential of malignant tumors. To explore the role of E-cadherin, we established an E-cadherin-expressing cell line, EC96, from AGS cells that featured undetectable E-cadherin expression and a high level of Wnt signaling. In EC96 cells, E-cadherin re-expression enhanced cell proliferation, although Wnt signaling activity was reduced. Subsequent analysis revealed that nuclear factor-κB (NF-κB) activation and consequent c-myc expression might be involved in E-cadherin expression-mediated cell proliferation. To facilitate rapid proliferation, EC96 cells enhance glucose uptake and produce ATP using both mitochondria oxidative phosphorylation and glycolysis, whereas AGS cells use these mechanisms less efficiently. These events appeared to be mediated by NF-κB activation. Therefore, E-cadherin re-expression and subsequent induction of NF-κB signaling likely enhance energy production and cell proliferation.

Homogenizing cellular tension by hepatocyte growth factor in expanding epithelial monolayer

Hepatocyte growth factor (HGF) induces cell migration and scattering by mechanisms that are thought to tip a local balance of competing physical forces; cell-to-cell and cell-to-substrate forces. In this local process, HGF is known to attenuate local cadherin-dependent adhesion forces for cell-cell junction development and enhance local integrin-dependent contractile forces for pulling neighboring cells apart. Here we use an expanding island of confluent Madin-Darby canine kidney (MDCK) cells as a model system to quantify the collective cell migration. In the absence of HGF, cell trajectories are highly tortuous whereas in the presence of HGF, they become far less so, resembling free expansion of a gas. At the level of cell-to-cell junctions, HGF attenuates the linkage of stress fibers to cell-to-cell junctions with concomitant decrease in intercellular stress. At the level of cell-to-substrate junctions, HGF augments the linkage of stress fibers to cell-to-substrate junctions with no apparent effect on traction. Together, HGF induces both structural changes in the actin-bound junctional protein complex and physical forces spanning multicellular clusters, which further promotes the expansion of confluent cellular layer.

Phylogenetic relationships of the HA and NA genes between vaccine and seasonal influenza A(H3N2) strains in Korea

Seasonal influenza is caused by two influenza A subtype (H1N1 and H3N2) and two influenza B lineage (Victoria and Yamagata) viruses. Of these antigenically distinct viruses, the H3N2 virus was consistently detected in substantial proportions in Korea during the 2010/11-2013/14 seasons when compared to the other viruses and appeared responsible for the influenza-like illness rate peak during the first half of the 2011/12 season. To further scrutinize possible causes for this, we investigated the evolutionary and serological relationships between the vaccine and Korean H3N2 strains during the 2011/12 season for the main antigenic determinants of influenza viruses, the hemagglutinin (HA) and neuraminidase (NA) genes. In the 2011/12 season, when the number of H3N2 cases peaked, the majority of the Korean strains did not belong to the HA clade of A/Perth/16/2009 vaccine, and no Korean strains were of this lineage in the NA segment. In a serological assay, post-vaccinated human sera exhibited much reduced hemagglutination inhibition antibody titers against the non-vaccine clade Korean H3N2 strains. Moreover, Korean strains harbored several amino acid differences in the HA antigenic sites and in the NA with respect to vaccine lineages during this season. Of these, the HA antigenic site C residues 45 and 261 and the NA residue 81 appeared to be the signatures of positive selection. In subsequent seasons, when H3N2 cases were lower, the HA and NA genes of vaccine and Korean strains were more phylogenetically related to each other. Combined, our results provide indirect support for using phylogenetic clustering patterns of the HA and possibly also the NA genes in the selection of vaccine viruses and the assessment of vaccine effectiveness.

Reassortment compatibility between PB1, PB2, and HA genes of the two influenza B virus lineages in mammalian cells

In addition to influenza A subtypes, two distinct lineages of influenza B virus also cause seasonal epidemics to humans. Recently, Dudas et al. have done evolutionary analyses of reassortment patterns of the virus and suggested genetic lineage relationship between PB1, PB2, and HA genes. Using genetic plasmids and reassortant viruses, we here demonstrate that a homologous lineage PB1-PB2 pair exhibits better compatibility than a heterologous one and that the lineage relationship between PB1 and HA is more important for viral replication than that between PB2 and HA. However, co-adaptation of PB1-PB2-HA genes appears to be affected by complete gene constellation.

Axin is expressed in mitochondria and suppresses mitochondrial ATP synthesis in HeLa cells

Many recent studies have revealed that axin is involved in numerous cellular functions beyond the negative regulation of β-catenin-dependent Wnt signaling. Previously, an association of ectopic axin with mitochondria was observed. In an effort to investigate the relationship between axin and mitochondria, we found that axin expression suppressed cellular ATP production, which was more apparent as axin expression levels increased. Also, mitochondrial expression of axin was observed using two axin-expressing HeLa cell models: doxycycline-inducible ectopic axin expression (HeLa-axin) and axin expression enhanced by long-term treatment with XAV939 (HeLa-XAV). In biochemical analysis, axin is associated with oxidative phosphorylation (OXPHOS) complex IV and is involved in defects in the assembly of complex IV-containing supercomplexes. Functionally, axin expression reduced the activity of OXPHOS complex IV and the oxygen consumption rate (OCR), suggesting axin-mediated mitochondrial dysfunction. Subsequent studies using various inhibitors of Wnt signaling showed that the reduction in cellular ATP levels was weaker in cases of ICAT protein expression and treatment with iCRT3 or NSC668036 compared with XAV939 treatment, suggesting that XAV939 treatment affects ATP synthesis in addition to suppressing Wnt signaling activity. Axin-mediated regulation of mitochondrial function may be an additional mechanism to Wnt signaling for regulation of cell growth.

Axin expression delays herpes simplex virus-induced autophagy and enhances viral replication in L929 cells

Axin, a negative regulator of the Wnt signaling pathway, plays a critical role in various cellular events including cell proliferation and cell death. Axin-regulated cell death affects multiple processes, including viral replication. For example, axin expression suppresses herpes simplex virus (HSV)-induced necrotic cell death and enhances viral replication. Based on these observations, this study investigated the involvement of autophagy in regulation of HSV replication and found axin expression inhibits autophagy-mediated suppression of viral replication in L929 cells. HSV infection induced autophagy in a time- and viral dose-dependent manner in control L929 cells (L-EV), whereas virus-induced autophagy was delayed in axin-expressing L929 cells (L-axin). Subsequent analysis showed that induction of autophagy by rapamycin reduced HSV replication, and that inhibiting autophagy by 3-methyladenine (3MA) and beclin-1 knockdown facilitated viral replication in L-EV cells. In addition, preventing autophagy with 3MA suppressed virus-induced cytotoxicity in L-EV cells. In contrast, HSV replication in L-axin cells was resistant to changes in autophagy. These results suggest that axin expression may render L929 cells resistant to HSV-infection induced autophagy, leading to enhanced viral replication.

Axin expression enhances herpes simplex virus type 1 replication by inhibiting virus-mediated cell death in L929 cells

Herpes simplex virus type 1 (HSV-1) replicates in various cell types and induces early cell death, which limits viral replication in certain cell types. Axin is a scaffolding protein that regulates Wnt signalling and participates in various cellular events, including cellular proliferation and cell death. The effects of axin expression on HSV-1 infection were investigated based on our initial observation that Wnt3a treatment or axin knockdown reduced HSV-1 replication. L929 cells expressed the axin protein in a doxycycline-inducible manner (L-axin) and enhanced HSV-1 replication in comparison to control cells (L-EV). HSV-1 infection induced cell death as early as 6 h after infection through the necrotic pathway and required de novo protein synthesis in L929 cells. Subsequent analysis of viral protein expression suggested that axin expression led to suppression of HSV-1-induced premature cell death, resulting in increased late gene expression. In analysis of axin deletion mutants, the regulators of the G-protein signalling (RGS) domain were involved in the axin-mediated enhancement of viral replication and reduction in cell death. These results suggest that viral replication enhancement might be mediated by the axin RGS domain.

Axin1 expression facilitates cell death induced by aurora kinase inhibition through PARP activation

Axin, a negative regulator of Wnt signaling, participates in apoptosis, and Axin1 localizes to centrosomes and mitotic spindles, which requires Aurora kinase activity. In this study, Aurora inhibition of Axin1-expressing cells (L-Axin) produced polyploid cells, which died within 48 h posttreatment, whereas Axin2-expressing cells (L-Axin2) survived the same period. These cell death events showed apoptotic signs, such as chromatin condensation and increased sub-G1 populations, as well as cell membrane rupture. Further analysis showed that Aurora kinase inhibitor (AKI) treatment of L-Axin cells induced poly(ADP-ribose) polymerase (PARP) activation, which increased the poly(ADP-ribosyl)ation of cellular proteins and reduced cellular ATP content. PARP inhibition reduced a proportion of dead cells, suggesting PARP involvement in AKI-induced cell death. Also, AKI treatment of L-Axin cells induced mitochondrial apoptosis-inducing factor (AIF) release, but not mitochondrial cytochrome c release or caspase-3 activation. Knockdown of AIF attenuated AKI-induced cell death in L-Axin cells. Thus, our results suggest that Axin1 expression renders L929 cells sensitive to Aurora inhibition-induced cell death in a PARP- and AIF-dependent manner.

Regulation of AHI1 expression in adult rat brain: Implication in hypothalamic feeding control

Recent studies revealed that Abelson helper integration site 1 (AHI1) plays a role in brain development. However, little is known about the role of AHI1 in adult brain. To directly assess the role of AHI1 in the adult brain, we cloned full-length cDNA of rat AHI1 and observed prominent expression of AHI1 in the hypothalamus, which contributes mainly to the control of energy homeostasis. Furthermore, we demonstrated that food deprivation caused induction of AHI1 in the hypothalamus and subsequent re-feeding down-regulated AHI1 expression, suggesting the involvement of AHI1 in feeding control. Moreover, the expression of AHI1 was increased in serum-depleted Neuro2A cells and restored by subsequent insulin treatment. Furthermore, treatment in food-deprived rat with intraperitoneal glucose also reduced the increased AHI1 expression. These results demonstrate that AHI1 expression can be regulated through diet and suggest the novel role of AHI1 in feeding behavior.

Axin localizes to mitotic spindles and centrosomes in mitotic cells

Wnt signaling plays critical roles in cell proliferation and carcinogenesis. In addition, numerous recent studies have shown that various Wnt signaling components are involved in mitosis and chromosomal instability. However, the role of Axin, a negative regulator of Wnt signaling, in mitosis has remained unclear. Using monoclonal antibodies against Axin, we found that Axin localizes to the centrosome and along mitotic spindles. This localization was suppressed by siRNA specific for Aurora A kinase and by Aurora kinase inhibitor. Interestingly, Axin over-expression altered the subcellular distribution of Plk1 and of phosphorylated glycogen synthase kinase (GSK3beta) without producing any notable changes in cellular phenotype. In the presence of Aurora kinase inhibitor, Axin over-expression induced the formation of cleavage furrow-like structures and of prominent astral microtubules lacking midbody formation in a subset of cells. Our results suggest that Axin modulates distribution of Axin-associated proteins such as Plk1 and GSK3beta in an expression level-dependent manner and these interactions affect the mitotic process, including cytokinesis under certain conditions, such as in the presence of Aurora kinase inhibitor.

Hanultarin, a cytotoxic lignan as an inhibitor of actin cytoskeleton polymerization from the seeds of Trichosanthes kirilowii

Bioactivity-directed fractionation of extracts from the seeds of Trichosanthes kirilowii led to the isolation of (-)-1-O-feruloylsecoisolariciresinol (2), named hanultarin, In addition, four known lignans were also isolated, including (-)-secoisolariciresinol (1), 1,4-O-diferuloylsecoisolariciresinol (3), (-)-pinoresinol (4), and 4-ketopinoresinol (5). Their structures were elucidated on the basis of spectroscopic data. Compounds 2 and 3 exhibited strong cytotoxic effects against human lung carcinoma A549 cells, melanoma SK-Mel-2 cells, and mouse skin melanoma B16F1 cells with IC(50) ranges of 3-13 microg/mL. Compound 2 showed an inhibitory effect on the polymerization of the actin cytoskeleton in normal epidermal keratinocyte (HaCaT cells), suggesting unique biological properties of compound 2 compared to those of the other isolates.

Clusterin enhances proliferation of primary astrocytes through extracellular signal-regulated kinase activation

Clusterin, a secretory glycoprotein, has been shown to be up-regulated in the reactive astrocytes in response to brain injury and neurodegenerative diseases, but its function has not been clearly elucidated. In this study, we investigate whether clusterin has growth-stimulatory activity in astrocytes. Suppression of clusterin with antisense oligonucleotide induced growth arrest, whereas transient overexpression of clusterin by cDNA transfection or exogenous treatment with purified clusterin promoted proliferation of the primary astrocytes in culture. This clusterin-stimulated proliferation was abrogated by PD98059, an inhibitor of mitogen-activated protein kinase kinase. These results suggest that clusterin might play an important role in astrogliosis by stimulating the proliferation of astrocytes through activation of the extracellular signal-regulated kinase 1/2 signaling pathway.

Expression of class II ?-tubulin in non-melanoma cutaneous tumors

BACKGROUND

Different combinations of beta-tubulin isotypes contribute to the diverse functions of microtubules (MTs). Class II beta-tubulin (class II tubulin) is up-regulated in differentiated keratinocytes. In contrast, the expression of class II tubulin in follicular differentiation and cutaneous tumors has not been studied.

METHODS

The immunohistochemical expression of class II tubulin was investigated in 117 cutaneous tumors: 30 squamous cell carcinomas (SCCs), seven keratoacanthomas (KAs), 57 basal cell carcinomas (BCCs), 23 trichoepitheliomas (TEs), and in the adjacent non-neoplastic skin.

RESULTS

Class II tubulin was expressed in the keratinocytes of the granular layer, melanocytes, hair cortical and cuticular cells, inner root sheath (IRS), companion layer (CL) of the outer root sheath (ORS), and mesenchymal cells with Schwannian or myogenic differentiation. Moreover, class II tubulin expression was increased in the areas of squamous or follicular differentiation in cutaneous tumors. On grading the follicular differentiation or myofibroblastic response with anti-class II tubulin, TE showed follicular differentiation more frequently (p < 0.001) with less of a myofibroblastic response (p = 0.001) than BCC.

CONCLUSIONS

Class II tubulin expression is closely related to squamous or follicular differentiation and may be helpful in distinguishing most SCCs from KAs and BCC from TE. However, it does not reliably distinguish well-differentiated, crateriform SCC from KA.

Analysis of calcium-inducible genes in keratinocytes using suppression subtractive hybridization and cDNA microarray

Terminal differentiation of skin keratinocytes is a vertically directed multistep process that is tightly controlled by the sequential expression of a variety of genes. To gain further insight into the molecular events involved in this process, we used suppression subtraction hybridization (SSH) and cDNA microarray analysis. Messenger RNAs were isolated from primary skin keratinocytes cultured in vitro after treatment with calcium and then SSH was performed. A total of 840 cDNA clones were obtained from subtracted libraries, and these cDNA clones were used to make the microarray slides. Time-course cDNA microarray analysis (1, 3, 7, and 14 days after calcium treatment) revealed the global gene expression profile during keratinocyte differentiation. Of the 840 genes tested, 290 showed a greater than twofold change in expression level at least once over four time points. The genes were clustered into six groups according to their expression pattern using self-organizing map analysis and showed the global feature of function-related regulation. The genes related to keratinocyte differentiation were markedly up-regulated by calcium treatment. In addition, a unique pattern of increase was seen in the expression of genes related to ribosomal proteins. On the other hand, transcripts involved in metabolism, DNA repair, transcription, and translation were generally down-regulated. These results demonstrate the complexity of the gene expression profile that contributes to the spatiotemporal regulation of keratinocyte differentiation.

Molecular Cloning and Expression of Human Keratinocyte Proline-Rich Protein (hKPRP), an Epidermal Marker Isolated from Calcium-Induced Differentiating Keratinocytes

We isolated a human gene encoding keratinocyte proline-rich protein (hKPRP). hKPRP gene is located in the region of epidermal differentiation complex on chromosome 1q21, and its approximately 2.5 kb mRNA encodes 579 amino acid protein with high proline content (18%). The mRNA level of hKPRP was markedly increased at both 7 and 14 d after treatment with 1.2 mM calcium in cultured normal human epidermal keratinocytes. In situ hybridization demonstrated that hKPRP was expressed in upper granular layer of normal epidermis with characteristic intermittent pattern. In psoriatic lesion, hKPRP expression was increased as compared with normal skin and showed continuous pattern. Immunohistochemical analysis also confirmed the expression of hKPRP at the protein level. Western blot analysis showed that hKPRP protein of approximately 70 kDa size was significantly increased by calcium in a time-dependent manner. In mouse tissue blot assays, the expression of KPRP was detected in stomach and skin tissues, and began at 17.5 embryonic days. Additionally, hKPRP expression was detected in the periderm of human fetal skin from 16 wk estimated gestational age. Together, these results suggest that hKPRP is an epidermal marker expressed in stratified squamous epithelia and has a potential role in keratinocytes differentiation.

Multinuclear giant cell formation is enhanced by down-regulation of Wnt signaling in gastric cancer cell line, AGS

AGS cells, which were derived from malignant gastric adenocarcinoma tissue, lack E-cadherin-mediated cell adhesion but have a high level of nuclear beta-catenin, which suggests altered Wnt signal. In addition, approximately 5% of AGS cells form multinuclear giant cells in the routine culture conditions, while taxol treatment causes most AGS cells to become giant cells. The observation of reduced nuclear beta-catenin levels in giant cells induced by taxol treatment prompted us to investigate the relationship between Wnt signaling and giant cell formation. After overnight serum starvation, the shape of AGS cells became flattened, and this morphological change was accompanied by decrease in Myc expression and an increase in the giant cell population. Lithium chloride treatment, which inhibits GSK3beta activity, reversed these serum starvation effects, which suggests an inverse relationship between Wnt signaling and giant cell formation. Furthermore, the down-regulation of Wnt signaling caused by the over-expression of ICAT, E-cadherin, and Axin enhanced giant cell formation. Therefore, down-regulation of Wnt signaling may be related to giant cell formation, which is considered to be a survival mechanism against induced cell death.

Upregulation of class II beta-tubulin expression in differentiating keratinocytes

The diverse functions of microtubules (MT) in different cells and tissues may be facilitated by compositional changes in tubulin isotypes. We obtained partial cDNA clones of class II beta-tubulin from a library of differentiating normal human epidermal keratinocytes (NHEK) cells, whereas screening via subtractive hybridization for genes involved in calcium-induced keratinocyte differentiation. Analysis of the isotypic composition of beta-tubulin from NHEK cells revealed elevations in class II beta-tubulin concentrations at both protein and message levels during cell differentiation, resulting in increased rates of incorporation of class II beta-tubulin into MT. Immunohistochemistry of normal and pathologic skin tissues showed that class II beta-tubulin occurred in the granular layer of the epidermis and in differentiated areas of carcinomas. Class II beta-tubulin was, however, not observed in the uppermost granular and cornified layers of normal epidermis. Further experiments showed that MT were likely to decay in the final stage of terminal differentiation during formation of the cornified envelope. Our results suggest that there is differential modulation of MT composition and stability during keratinocyte differentiation.

Effects of endocytosis inhibitory drugs on rubella virus entry into VeroE6 cells

It has been suggested that infectious entry of rubella virus (RV) is conducted by receptor mediated endocytosis. To explore the cellular entry mechanism of RV, inhibitory effects of drugs affecting various endocytic pathways on RV entry into VeroE6 cells were analyzed. Results showed that RV infectious entry into VeroE6 cells is mediated by clathrin-dependent endocytosis and not by caveolae-mediated endocytosis. Moreover, chemical inhibition of macropinocytosis such as treatments of amiloride, actin and microtubule-disrupting drug significantly reduced RV infection. Considering that macropinocytosis is inducible endocytosis by cellular stimulations, clathrin-mediated endocytosis is likely to be a major route of RV infectious entry.

Analysis of genes responding to ultraviolet B irradiation of HaCaT keratinocytes using a cDNA microarray

BACKGROUND

Ultraviolet (UV) B irradiation causes many important biological changes in skin, which lead to pathophysiological alterations of the homeostatic environment.

OBJECTIVES

To gain more insight into the molecular events provoked by UVB irradiation, we performed cDNA microarray analysis.

METHODS

Immortalized HaCaT keratinocytes were irradiated with a high cytotoxic dose of UVB (50 mJ cm(-2)), and total RNA was isolated. Fluorescently labelled probes were prepared by reverse transcription and were hybridized with cDNA microarray slides made using 840 cDNA clones.

RESULTS

Time-course cDNA microarray analysis revealed the global gene expression profile after UVB exposure. Of 840 genes tested, 192 genes showed changes in their expression levels at one or more of four time points. The genes were clustered into four groups according to their expression patterns in a self-organizing maps analysis. Classification of these genes into nine functional categories revealed that UVB irradiation affected several biological processes. The genes that were first upregulated and then returned to normal levels included several genes related to the inhibition of cell growth and the proteasome pathway. Conversely, the expressions of many genes involved in the cytoskeleton, signal transduction, metabolism and transcription were first downregulated or unchanged and then upregulated later, reflecting the recovery of UVB-damaged cellular activities.

CONCLUSIONS

These results demonstrate the complexity of the transcriptional profile of the UVB response, and provide a basis for the global characterization of UV-regulated gene expression.

Cell-cell adhesion and RhoA-mediated actin polymerization are independent phenomena in microtubule disrupted keratinocytes

E-cadherin-mediated adherens junction formation and maintenance are thought to involve actin filament rearrangements through the action of small GTPases. Recently, we demonstrated that microtubule disruption in normal human epidermal keratinocytes grown in low calcium media conditions induces cell-cell adhesion by redistribution of endogenous E-cadherin, and it promotes stress fiber formation. This actin rearrangement was apparently mediated by RhoA activation. This model system therefore provides a tool with which to dissect relationships between cell-cell adhesion and Rho-mediated stress fiber formation. In this study, we have demonstrated in normal human epidermal keratinocytes that disruption of actin structures including stress fibers does not interfere with E-cadherin redistribution during microtubule-induced cell-cell adhesion. Moreover, this cell-cell adhesion could not be blocked by RhoA inactivation at the level for inhibition of stress fiber formation. Additionally, in the immortalized HaCaT keratinocyte cell line, which does not undergo cell-cell adhesion after microtubule disruption in low calcium conditions, expression of dominant-active RhoA could induce stress fiber formation without inducing adhesion. On the other hand, a variant of the HaCaT cell line, HC-R1, showed microtubule-disruption-induced cell-cell adhesion without stress fiber formation. Together, our results suggest that, in keratinocytes, the process of cell adhesion can occur independently of RhoA-mediated stress fiber formation.

Three-dimensional structure of the human transglutaminase 3 enzyme: binding of calcium ions changes structure for activation

Transglutaminase (TGase) enzymes catalyze the formation of covalent cross-links between protein-bound glutamines and lysines in a calcium-dependent manner, but the role of Ca(2+) ions remains unclear. The TGase 3 isoform is widely expressed and is important for epithelial barrier formation. It is a zymogen, requiring proteolysis for activity. We have solved the three-dimensional structures of the zymogen and the activated forms at 2.2 and 2.1 A resolution, respectively, and examined the role of Ca(2+) ions. The zymogen binds one ion tightly that cannot be exchanged. Upon proteolysis, the enzyme exothermally acquires two more Ca(2+) ions that activate the enzyme, are exchangeable and are functionally replaceable by other lanthanide trivalent cations. Binding of a Ca(2+) ion at one of these sites opens a channel which exposes the key Trp236 and Trp327 residues that control substrate access to the active site. Together, these biochemical and structural data reveal for the first time in a TGase enzyme that Ca(2+) ions induce structural changes which at least in part dictate activity and, moreover, may confer substrate specificity.

Microtubule disruption in keratinocytes induces cell-cell adhesion through activation of endogenous E-cadherin

The association of the cytoskeleton with the cadherin--catenin complex is essential for strong cell-cell adhesion in epithelial cells. In this study, we have investigated the effect of microtubule organization on cell-cell adhesion in differentiating keratinocytes. When microtubules of normal human epidermal keratinocytes (NHEKs) grown in low calcium media (0.05 mM) were disrupted with nocodazole or colcemid, cell-cell adhesion was induced through relocalization of the E-cadherin-catenin-actin complex to the cell periphery. This was accompanied by actin polymerization. Also, it was found that microtubule disruption-induced cell-cell adhesion was significantly reduced in more advanced differentiated keratinocytes. For example, when NHEK cells cultured under high calcium (1.2 mM) for 8 d and then in low calcium for 1 d were treated with nocodazole, there was no induction of cell-cell adhesion. Also long-term treatment of a phorbol ester for 48 h inhibited nocodazole-induced cell-cell adhesion of NHEK. Furthermore, this nocodazole-induced cell-cell adhesion could be observed in squamous cancer cell lines (A431 and SCC-5, -9, and -25) under low calcium condition, but not in the keratinocyte cell lines derived from normal epidermis (HaCaT, RHEK). On the other hand, HaCaT cells continuously cultivated in low calcium media regained a less differentiated phenotype such as decreased expression of cytokeratin 10, and increased K5; these changes were accompanied with inducibility of cell-cell adhesion by nocodazole. Together, our results suggest that microtubule disruption can induce the cell-cell adhesion via activation of endogenous E-cadherin in non- or early differentiating keratinocytes. However, this is no longer possible in advanced terminally differentiating keratinocytes, possibly due to irreversible changes effected by cell envelope barrier formation.

Role of reconstituted basement membrane in human granulosa cell culture

The effects of Matrigel, a reconstituted basement membrane, on human granulosa cells were investigated. Cells were obtained from follicular aspirate in the course of oocyte retrieval for in vitro fertilization and were cultured on either a surface coated with Matrigel or uncoated plastic. Light and electron microscopy showed that granulosa cells cultured on Matrigel demonstrated three-dimensional aggregated cells with well differentiated morphology: numerous lipid droplets, microvilli, junctional complexes and lumen-like structures were seen. In contrast, cells cultured on plastic were flattened, poorly differentiated and showed apoptotic cells. Immunocytochemistry showed that the proportion of immunopositive cells for 3beta-hydroxysteroid dehydrogenase was increased in cultures on Matrigel. The results of the present study suggest that culture on Matrigel promotes the differentiation of human granulosa cells and provides a useful tool which may improve the efficiency of in vitro fertilization.

Disassembly of focal adhesions during apoptosis of endothelial cell line ECV304 infected with Orientia tsutsugamushi

Many bacterial pathogens induce apoptosis in their host cells. We observed the cellular effect of ECV304 cells infected with Orientia tsutsugamushi. The infected cells became rounded and floated in culture supernatant. These floating cells as well as adherent cells exhibited typical features of apoptosis, such as DNA fragmentation and TUNEL staining. As many cells detached from growth substrate, we examined the focal adhesion using the immunofluorescence assay method and observed decreased focal adhesions in heavily infected cells. As endothelial cells could undergo apoptosis by the loss of focal adhesions, this change of focal adhesions may account for the Orientia-induced apoptosis.

Apoptosis of endothelial cell line ECV304 persistently infected with Orientia tsutsugamushi

Endothelial cells are major targets of Orientia tsutsugamushi. To examine the consequences of the infection of endothelial cells with O. tsutsugamushi, we used human endothelial cell line ECV304. Persistent infection was established and infected cultures could be maintained for over seven months without the addition of normal cells. The heavily infected cells became round and floated in the culture medium, harboring large numbers of organisms inside them. Some of the infected ECV304 cells showed features of apoptotic cells, as determined by the terminal deoxytransferase-mediated dUTP nick end-labeling reaction and DNA fragmentation. We also found that O. tsutsugamushi increased transcription of the mRNAs of proinflammatory cytokines such as IL-6 and IL-8. These results show the first evidence of in vitro-persistent infection by O. tsutsugamushi, which may be related to in vivo persistence reported previously.

Infection rate of Leptospira interrogans in the field rodent, Apodemus agrarius, in Korea

Leptospirosis has significantly decreased in Korea since 1988, following the leptospiral vaccination programme initiated in 1988. Whether this wholly explains the decreased incidence is uncertain. As an initial step to answer this question, infection rates of Leptospira interrogans in field rodents, Apodemis agrarius, were examined and compared with previous data. Two hundred and twenty-two A. agrarius were captured during October-December 1996. Spirochaetes were isolated from 22 (9.9%) and leptospiral DNA was detected in an additional 6 rodents (12.6%). Subsequent microscopic agglutination tests (MAT) classified all these isolates as L. interrogans serogroup Icterohaemorrhagiae serovar lai. The above data did not significantly differ from previous surveys in 1984-7. There was no significant change of L. interrogans infection in field rodents following the introduction of the vaccination programme in Korea. Further studies are needed to determine the role of human vaccination in reducing incidence.

Molecular and serologic survey of Orientia tsutsugamushi infection among field rodents in southern Cholla Province, Korea

Field rodents were collected from six areas in southern Cholla Province, Korea from October to December 1993. Twenty-eight (24%) of the 119 Apodemus agrarius were seropositive (> 1:10) for Orientia tsutsugamushi by the passive hemagglutination assay (PHA). Of the seropositive cases, 11 specimens had antibody titers greater than 1:80. No seropositive specimens were found among the eight Crocidura lasiura collected. On the other hand, the polymerase chain reaction (PCR) amplified about 520 basepairs of a gene encoding the 56-kD protein from the genomic DNA of 12 strains of O. tsutsugamushi tested. This target DNA sequence was amplified from the 11 (8.7%) blood specimens of A. agrarius, and one of the eight C. lasiura also showed evidence of O. tsutsugamushi infection by PCR. Only one of the PCR-positive samples was also PHA-positive. These results suggest that the PCR combined with a serologic assay more accurately detects the degree of infection of rodents with rickettsiae-causing scrub typhus in epidemiologic surveys.

Identification of antigenic differences between the phosphorylated and nonphosphorylated forms of the E7 protein of human papillomavirus type 16

To analyze the antigenic properties of the human papillomavirus type 16 E7 oncoprotein, two monoclonal antibodies, VD6 and IB10, that have different reactivities to the E7 protein were generated. While the VD6 antibody reacted strongly with E7 protein in CaSki cell extracts, the other antibody, IB10, showed much weaker reactivity with E7. This reactivity increased in a dose-dependent manner in the presence of the casein kinase II-specific inhibitor DRB (5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole). Antigenic site estimation and an in vitro phosphorylation assay, using bacterially expressed E7 protein, demonstrated that the weak reactivity of IB10 was related to the phosphorylation status of the E7 protein. Phosphorylation of E7 reduced considerably the reactivity of IB10 but did not affect the reactivity of VD6, which reacts with the N-terminal portion of E7. In immunoprecipitation (IP) assays, IB10 precipitated weakly the E7 protein from CaSki cell extracts. Together, these data suggest that unphosphorylated E7 protein shows distinct antigenic character compared to its phosphorylated form under denaturing conditions; however, under native conditions, the phosphorylated and nonphosphorylated E7 proteins have some antigenic cross-reactivity.

Long-term oral administration of ginseng extract decreases serum gamma-globulin and IgG1 isotype in mice

Effects of long-term oral administration of ginseng extract on serum protein profile and immunoglobulin (Ig) isotypes were studied in mice. Ginseng extract was orally administered to healthy female mice for 52 days at doses of 30 and 150 mg/kg per day and serum protein electrophoretograms and Ig isotypes levels were evaluated. Serum level of gamma-globulin was decreased dose dependently to 82% (P < 0.05) and 56% (P < 0.01) of control values at the doses of 30 and 150 mg/kg per day, respectively. Levels of total protein, albumin, alpha2- and beta-globulin fractions, as well as the ratio of albumin to globulin (A/G) did not change significantly. However, the alpha1-globulin level increased by 24% (P < 0.05) at the doses of 30 and 150 mg/kg per day. Among the Ig isotypes, including IgG1, IgG2a, IgG2b, IgG3, IgM and IgA, serum IgG1 was dose dependently decreased to 68% (P < 0.05) of control values at the dose of 150 mg/kg per day without significant changes in other Ig isotypes. As IgG1 isotype is rarely cytotoxic and can act as a blocking antibody, it is suggested that the selective decrease in serum IgG1 induced by ginseng extract without changes in the cytotoxic antibodies such as IgG2a may be helpful for the prevention and inhibition of cancer.

Major sequence variants in E7 gene of human papillomavirus type 16 from cervical cancerous and noncancerous lesions of Korean women

Geographic specificity of nucleotide sequence variations in the coding and noncoding regions of HPV 16 genome has been reported. Little has been known, however, regarding whether these naturally occurring sequence variations of HPV 16 may result in marked differences in biological properties, such as oncogenic potential. This study was performed to identify sequence variants in the HPV 16 E7 gene derived from Korean women with cervical cancerous and noncancerous lesions, and to assess the association between the sequence variant and the cervical cancer. We examined E7 variants of HPV 16 in a total of 157 patients with no cervical disease (NCD, n = 87) or cervical neoplasia (cervical intraepithelial neoplasia 3, n = 21; cervical carcinoma, n = 49), using the nested polymerase chain reaction (PCR) and the PCR-directed sequencing methods with outer consensus and inner type-specific primers. Forty-two (NCD, n = 9; CIN 3, n = 6; cervical carcinoma, n = 27) of 157 cervical samples contained HPV 16 E7 DNA, but only 8 had prototype sequences. Four variants of the HPV 16 E7 gene were identified. The variant with a single nucleotide change at position 647 (A --> G, Asn --> Ser) was found in about 60% of DNA samples with HPV 16. The second most common variant, found in 16.7% of cases, had three silent mutations at positions 732 (T --> C), 789 (T --> C), and 795 (T --> G). Two other variants were detected, one in a patient with cervical cancer and the other in a patient with no cervical disease. One had a single nucleotide change at position 666 (G --> A) and the other had one silent mutation at position 796 (T --> C). The most common variant in Korea has a change of nucleotide affecting the predicted amino acid related with high antigenicity and binding to retinoblastoma protein. There was a statistically significant trend for this variant to be more frequently detected in cancerous lesions of the uterine cervix than in noncancerous lesions. These data suggest that naturally occurring sequence variants of HPV 16 E7 gene may have different oncogenic properties.

Genetic analysis of Borrelia burgdorferi sensu lato in Korea using genomic hybridization and 16S rRNA gene sequence determination

Nine Borrelia burgdorferi sensu lato isolated in Korea were subjected to genomic hybridization using 16S rRNA gene probe and specific restriction patterns (HindIII and EcoRV) led these nine Borrelia into five subtypes. The evolutionary relationships of the five isolates corresponding to five RFLP groups were measured through the sequence determination of 16S rRNA gene and phylogenetic analysis. The isolates 935T (group I), 934U and 17Y (Group IIa, IIb) were well clustered with B. garinii and B. afzelii. 5MT and 9MT strains (Group IIIa and Group IIIb) formed a common branch shared with B. afzelii cluster although the evolutionary distance was rather long. So, most of B. burgdorferi sensu lato in Korea was B. afzelii or B. afzelii-related group and some minor group such as B. garinii also existed.

Detection of Rickettsia tsutsugamushi in Experimentally infected mice by PCR

We developed a rapid procedure for the detection of Rickettsia tsutsugamushi DNA by the PCR technique. The primer pair used for the PCR was designed from the DNA sequence of the gene encoding a 120-kDa antigen, which was proven to be group specific by immunoblot analysis with mouse hyperimmune sera against various rickettsial strains. This PCR method was able to detect up to 10 ag of plasmid DNA (pKT12). Specific PCR products were obtained with DNAs from R. tsutsugamushi Kato, Karp, Gilliam, TA716, TA1817, and Boryong, but not with DNAs from other rickettsiae, such as R. prowazekii, R. typhi, R. akari, and strain TT118. In a study with experimentally infected mice, the PCR method could detect rickettsial DNA from 2 days after inoculation (DAI), whereas serum antibody against R. tsutsugamushi could be detected from 6 to 8 DAI by an immunofluorescence test. Although clinical manifestations subsided after 14 DAI, rickettsial DNA in blood samples could be detected by PCR for up to 64 DAI. These results suggest that this PCR method can be applied to the early diagnosis of scrub typhus and can also be used to detect the residual rickettsiae after clinical symptoms subside.

Detection of leptospiral DNA by PCR

An EcoRI fragment (1.2 kb) which is highly conserved among Leptospira interrogans isolated in Korea was cloned into pBluescript vector from L. interrogans serovar lai WH20. The EcoRI fragment was sequenced, and a pair of primers (LP1 and LP2) was designed for PCR assay. PCR amplification of target DNA obtained from cultured L. interrogans showed that 274 bp could be detected when as little as 100 fg of leptospiral genomic DNA was used in the reaction mixture. No amplification of DNA was detected from DNA of Leptospira biflexa serovars patoc and sau paulo, Borrelia burgdorferi, Staphylococcus aureus, Escherichia coli, and Salmonella typhimurium. Amplification of 274-bp target DNA could be detected in DNA samples purified from 500 microliters of blood collected from experimentally infected gerbils 2 days after infection, while antibodies to L. interrogans could be detected by the microscopic agglutination test 7 days after infection. The specificity and high sensitivity of the test provided valuable tools for the early diagnosis of leptospirosis.