Morphological studies of fly puparia (Diptera: Calliphoridae) in the soil from a Joseon Dynasty grave in Korea.

Archaeoentomological investigations were conducted on soil contents from a grave belonging to the Joseon Dynasty as part of the Urban Environment Maintenance Project (UEMP) in Cheongjin 12-16 dong (districts), Jongno-gu, Seoul, Korea, from December 01, 2008 to February 19, 2011. A total of 28 insect puparia with hard shells of the common green bottle fly Lucilia sericata were identified in the soil. Evidence suggested that the corpse was placed outside for some days instead of being buried immediately after death. This is the first report of fly puparia in soil samples from a tomb of the Joseon Dynasty during 16-17 AD in Korea. Our findings may help determine the timeframe of burial and offer archaeological insights into the funerary customs of the period.

Genetic Diversity, Regional Distribution, and Clinical Characteristics of Severe Fever with Thrombocytopenia Syndrome Virus in Gangwon Province, Korea, a Highly Prevalent Region, 2019-2021.

Severe fever with thrombocytopenia syndrome (SFTS) is an arthropod-borne viral disease with a high mortality rate with high fever and thrombocytopenia. We investigated the clinical and epidemiological characteristics and viral genotypes from 2019 to 2021 in Gangwon Province, Korea. Of the 776 suspected cases, 62 were SFTS. The fatality rate was 11.5-28.6% (average rate, 19.4%), and the frequent clinical symptoms were high fever (95.2%), thrombocytopenia (95.2%), and leukopenia (90.3%). Hwacheon had the highest incidence rate per 100,000 persons at 8.03, followed by Inje and Yanggu (7.37 and 5.85, respectively). Goseong, Yangyang, and Hoengseong had rates of 2 or higher; Samcheok, Hongcheon, Jeongsen, and Yeonwol were 1.70-1.98, and Wonju, Gangneung, and Donghae were slightly lower, ranging from 0.31 to 0.74. Of the 57 cases with identified genotypes, eight genotypes (A, B1, B2, B3, C, D, E, and F) were detected, and the B2 genotype accounted for 54.4% (31 cases), followed by the A genotype at 22.8% (13 cases). The B2 and A genotypes were detected throughout Gangwon Province, and other genotypes, B1, B3, C, D, and F, were discovered in a few regions. In particular, genotype A could be further classified into subtypes. In conclusion, SFTS occurred throughout Gangwon Province, and Hwacheon had the highest incidence density. Multiple genotypes of SFTS were identified, with B2 and A being the most common. These findings provide important insights for the understanding and management of SFTS in this region.

Prevalence of chigger mites and Orientia tsutsugamushi strains in northern regions of Gangwon-do, Korea.

The present study aimed to survey the prevalence of chigger mites and Orientia tsutsugamushi (O. tsutsugamushi) infection in the northern regions of Gangwon-do, Korea. From early February to early June 2015, a total of 17,050 chiggers were collected from striped field mice, Apodemus agrarius, in Cheorwon-gun, Hwacheon-gun, Yanggu-gun, and Goseong-gun, which are well-known endemic areas of scrub typhus in Korea. The chiggers were analyzed using molecular genomic methods, as previously described. Among the 7,964 identified chiggers, the predominant species was Leptotrombidium pallidum (76.9%), followed by L. zetum (16.4%), L. orientale (4.3%), L. palpale (0.3%), L. tectum (0.2%), and Neotrombicula tamiyai (1.8%). The chigger index (CI) was highest in Hwacheon (115.58), followed by Cheorwon (97.02), Yanggu (76.88), and Goseong (54.68). Out of the 79 O. tsutsugamushi-positive chigger pools, 67 (84.8%) were identified as the Boryong strain, 10 (12.7%) as the Youngworl strain, and only 2 were the Jecheon strain. Based on the high infestation of chiggers in striped field rodents and the high rate of O. tsutsugamushi infection in chigger mites, Hwacheon-gun and Cheorwon-gun are presumed to be high-risk areas for scrub typhus. Furthermore, L. pallidum, a major vector of scrub typhus, and the dominant O. tsutsugamushi serotype, the Boryong strain, were found in the northern regions of Gangwon-do, Korea.

Antimicrobial peptides ß-defensin family: Expression and regulation in the endometrium during the estrous cycle and pregnancy in pigs.

Members of the ß-defensin (DEFB) family, which are antimicrobial peptides and humoral components of the innate immune system, protect the surfaces of various host tissues by killing a broad range of microorganisms and are involved in immunomodulatory actions. The expression of these DEFB members changed during the estrous cycle and pregnancy in a stage-specific manner. The expression of DEFBs was also detected in conceptus and chorioallantoic tissues during pregnancy. DEFB1 and DEFB3 proteins and DEFB2 mRNA were localized primarily to endometrial epithelial cells during early pregnancy. Increasing doses of progesterone upregulated DEFB2 and EP2C expression in endometrial explant tissues. These results showed that members of the DEFB family were expressed stage-specifically at the maternal-conceptus interface in pigs, suggesting that the DEFB family plays important roles at the maternal-conceptus interface in regulation of innate immunity by protection of the maternal endometrial and conceptus tissues from pathogens to preserve fertility in pigs.

Metabarcoding of bacteria and parasites in the gut of Apodemus agrarius.

BACKGROUND: The striped field mouse Apodemus agrarius is a wild rodent commonly found in fields in Korea. It is a known carrier of various pathogens. Amplicon-based next-generation sequencing (NGS) targeting the 16S ribosomal RNA (rRNA) gene is the most common technique used to analyze the bacterial microbiome. Although many bacterial microbiome analyses have been attempted using feces of wild animals, only a few studies have used NGS to screen for parasites. This study aimed to rapidly detect bacterial, fungal and parasitic pathogens in the guts of A. agrarius using NGS-based metabarcoding analysis. METHODS: We conducted 18S/16S rDNA-targeted high-throughput sequencing on cecal samples collected from A. agrarius (n = 48) trapped in May and October 2017. Taxa of protozoa, fungi, helminths and bacteria in the cecal content were then identified. RESULTS: Among the protozoa identified, the most prevalent was Tritrichomonas sp., found in all of the cecal samples, followed by Monocercomonas sp. (95.8% prevalence; in 46/48 samples) and Giardia sp. (75% prevalence; in 36/48 samples). For helminths, Heligmosomoides sp. was the most common, found in 85.4% (41/48) of samples, followed by Hymenolepis sp. (10.4%; 5/48) and Syphacia sp. (25%; 12/48). The 16S rRNA gene analysis showed that the microbial composition of the cecal samples changed by season (P = 0.005), with the linear discriminant analysis effect size showing that in the spring Escherichia coli and Lactobacillus murinus were more abundant and Helicobacter rodentium was less abundant. Helicobacter japonicus was more abundant and Prevotella_uc was less abundant in males. The microbial composition changed based on the Heligmosomoides sp. infection status (P = 0.019); specifically, Lactobacillus gasseri and Lactobacillus intestinalis were more abundant in the Heligmosomoides sp.-positive group than in the Heligmosomoides sp.-negative group. CONCLUSIONS: This study demonstrated that bacterial abundance changed based on the season and specific parasitic infection status of the trapped mice. These results highlight the advantages of NGS technology in monitoring zoonotic disease reservoirs.

Development of a Real-Time Recombinase Polymerase Amplification Assay for the Rapid Detection of African Swine Fever Virus Genotype I and II.

African swine fever (ASF) is a contagious viral disease in pigs and wild boars which poses a major threat to the pig industry. Rapid and accurate diagnosis is necessary to control ASF. Hence, we developed a rapid diagnostic method using a recombinase polymerase amplification (RPA) assay targeting the conserved sequences of CP204L (p30) thatcan rapidly detect ASF virus (ASFV) genotype strains I and II. The lower detection limit of the real-time RPA assay was 5 × 101 copies per reaction. The real-time RPA assay effectively detected ASFV isolates and clinical specimens belonging to ASFV genotypes I and II. The sensitivity and specificity of the assay were 96.8% (95% confidence interval (CI): 83.3−99.9) and 100% (95% CI: 88.4−100.0), respectively. The agreement between the real-time RPA assay and a reference commercial real-time quantitative polymerase chain reaction (qPCR) was 100%. The real-time RPA assay had a detection time of 6.0 min (95% CI: 5.7−6.2), which was significantly shorter than that of qPCR (49 min; 95% CI: 47.4−50.6; p < 0.001). Thus, the developed real-time RPA assay is a rapid and accurate diagnostic tool for detecting ASFV genotypes I and II.

Microbiome of Haemaphysalis longicornis Tick in Korea.

Ticks can transmit pathogenic bacteria, protozoa, and viruses to humans and animals. In this study, we investigated the microbiomes of Haemaphysalis longicornis according to sex and life stages. The Shannon index was significantly higher for nymphs than adult ticks. Principal coordinates analysis showed that the microbiome composition of female adult and male adult ticks were different. Notably, Coxiella-like bacterium (AB001519), known as a tick symbiont, was found in all nymphs and female adult ticks, but only one out of 4 male adult ticks had Coxiella-like bacterium (AB001519). In addition, Rickettsia rickettsii, Coxiella burnetii, and Anaplasma bovis were detected in this study.

Expression of Caspases in the Pig Endometrium Throughout the Estrous Cycle and at the Maternal-Conceptus Interface During Pregnancy and Regulation by Steroid Hormones and Cytokines.

Caspases, a family of cysteine protease enzymes, are a critical component of apoptotic cell death, but they are also involved in cellular differentiation. The expression of caspases during apoptotic processes in reproductive tissues has been shown in some species; however, the expression and regulation of caspases in the endometrium and placental tissues of pigs has not been fully understood. Therefore, we determined the expression of caspases CASP3, CASP6, CASP7, CASP8, CASP9, and CASP10 in the endometrium throughout the estrous cycle and pregnancy. During the estrous cycle, the expression of all caspases and during pregnancy, the expression of CASP3, CASP6, and CASP7 in the endometrium changed in a stage-specific manner. Conceptus and chorioallantoic tissues also expressed caspases during pregnancy. CASP3, cleaved-CASP3, and CASP7 proteins were localized to endometrial cells, with increased levels in luminal and glandular epithelial cells during early pregnancy, whereas apoptotic cells in the endometrium were limited to some scattered stromal cells with increased numbers on Day 15 of pregnancy. In endometrial explant cultures, the expression of some caspases was affected by steroid hormones (estradiol-17ß and/or progesterone), and the cytokines interleukin-1ß and interferon-γ induced the expression of CASP3 and CASP7, respectively. These results indicate that caspases are dynamically expressed in the endometrium throughout the estrous cycle and at the maternal-conceptus interface during pregnancy in response to steroid hormones and conceptus signals. Thus, caspase action could be important in regulating endometrial and placental function and epithelial cell function during the implantation period in pigs.

Structure-based functional analysis of a PadR transcription factor from Streptococcus pneumoniae and characteristic features in the PadR subfamily-2.

Since the first discovery of phenolic acid decarboxylase transcriptional regulator (PadR), its homologs have been identified mostly in bacterial species and constitute the PadR family. PadR family members commonly contain a winged helix-turn-helix (wHTH) motif and function as a transcription factor. However, the PadR family members are varied in terms of molecular size and structure. As a result, they are divided into PadR subfamily-1 and PadR subfamily-2. PadR subfamily-2 proteins have been reported in some pathogenic bacteria, including Listeria monocytogenes and Streptococcus pneumoniae, and implicated in drug resistance processes. Despite the growing numbers of known PadR family proteins and their critical functions in bacteria survival, biochemical and biophysical studies of the PadR subfamily-2 are limited. Here, we report the crystal structure of a PadR subfamily-2 member from Streptococcus pneumoniae (SpPadR) at a 2.40 Å resolution. SpPadR forms a dimer using its N-terminal and C-terminal helices. The two wHTH motifs of a SpPadR dimer expose their positively charged residues presumably to interact with DNA. Our structure-based mutational and biochemical study indicates that SpPadR specifically recognizes a palindromic nucleotide sequence upstream of its encoding region as a transcriptional regulator. Furthermore, comparative structural analysis of diverse PadR family members combined with a modeling study highlights the structural and regulatory features of SpPadR that are canonical to the PadR family or specific to the PadR subfamily-2.

Transcriptomic analysis of interferon-γ-regulated genes in endometrial explants and their possible role in regulating maternal endometrial immunity during the implantation period in pigs, a true epitheliochorial placentation species.

The implantation process requires precisely controlled interactions between the maternal uterine endometrium and the implanting conceptus. Conceptus-derived secretions affect endometrial cells to facilitate the adhesion and attachment of trophoblasts, and endometrial secretions support the growth and development of the conceptus. In pigs, the conceptus secretes a large amount of type II interferon, interferon-γ (IFNG), during the implantation period. However, the role of IFNG in the implantation process has not been fully understood in pigs. Thus, to determine the role of IFNG in the endometrium during early pregnancy in pigs, we treated endometrial explant tissues with increasing doses of IFNG and analyzed the transcriptome regulated by IFNG using an RNA-sequencing analysis. Data analyses identified 276 differentially regulated genes, their Gene Ontology terms, and 94 signature genes in a Gene Set Enrichment Analysis. Furthermore, we analyzed the expression of IFNG-regulated genes, including CIITA, KYNU, IDO1, WARS, and MHC class II molecules, in the endometrium throughout pregnancy and found that levels of those genes in the endometrium were highest on Day 15 of pregnancy, corresponding to the time of peak IFNG secretion by porcine conceptuses. In addition, immunohistochemical analyses revealed that CIITA, KYNU, and IDO proteins were expressed in a cell type- and pregnancy status-specific manner in the endometrium. These results show that genes overrepresented in endometrial tissues in response to IFNG were mainly related to immune responses, suggesting that conceptus-derived IFNG could play critical roles in regulating the maternal immune response for the establishment of pregnancy in pigs.

Seroprevalence of neutralizing antibodies against human adenovirus type 55 in the South Korean military, 2018-2019.

We conducted a seroprevalence study of a large ongoing outbreak of human adenovirus type 55 (HAdV-55) among the military in South Korea. Serum samples were collected between 2018 and 2019 from military-exposed (military group) and non-exposed (non-military group) populations. The plaque reduction neutralization test (PRNT) was used to assess neutralization activity against HAdV-55. A total of 100 sera was collected from the non-military group, of which 18.8% showed HAdV-55 neutralizing antibody activity. Ninety-six sera were tested from the military group, which had significantly higher prevalence of neutralizing antibodies (56.0%, P <0.001). A significantly higher proportion of the military group had PRNT titers ≥1:1,000 than the non-military group (85.7% vs. 50.0%, P = 0.004). Among the military group, 48.9% of active-duty soldiers had PRNT titers ≥1:5,000, while none of the discharged civilians did (P = 0.007). In conclusion, Koreans were exposed to HAdV-55 in their communities, but the exposure risk was higher among people in military service.

Crystal structure of the Pseudomonas aeruginosa PA0423 protein and its functional implication in antibiotic sequestration.

Pseudomonas aeruginosa is a widely found opportunistic pathogen. The emergence of multidrug-resistant strains and persistent chronic infections have increased. The protein encoded by the pa0423 gene in P. aeruginosa is proposed to be critical for pathogenesis and could be a virulence-promoting protease or a bacterial lipocalin that binds a lipid-like antibiotic for drug resistance. Although two functions of proteolysis and antibiotic resistance are mutually related to bacterial survival in the host, it is very unusual for a single-domain protein to target unrelated ligand molecules such as protein substrates and lipid-like antibiotics. To clearly address the biological role of the PA0423 protein, we performed structural and biochemical studies. We found that PA0423 adopts a single-domain ß-barrel structure and belongs to the lipocalin family. The PA0423 structure houses an internal tubular cavity, which accommodates a ubiquinone-8 molecule. Furthermore, we reveal that PA0423 can directly interact with the polymyxin B antibiotic using the internal cavity, suggesting that PA0423 has a physiological function in the antibiotic resistance of P. aeruginosa.

Cytokine Production in Cholangiocarcinoma Cells in Response to Clonorchis sinensis Excretory-Secretory Products and Their Putative Protein Components.

Clonorchis sinensis is a carcinogenic human liver fluke that promotes hepatic inflammatory environments via direct contact or through their excretory-secretory products (ESPs), subsequently leading to cholangitis, periductal fibrosis, liver cirrhosis, and even cholangiocarcinoma (CCA). This study was conducted to examine the host inflammatory responses to C. sinensis ESPs and their putative protein components selected from C. sinensis expressed sequenced tag (EST) pool databases, including TGF-ß receptor interacting protein 1(CsTRIP1), legumain (CsLeg), and growth factor binding protein 2 (CsGrb2). Treatment of CCA cells (HuCCT1) with the ESPs or bacterial recombinant C. sinensis proteins differentially promoted the secretion of proinflammatory cytokines (IL-1ß, IL-6, and TNF-α) as well as anti-inflammatory cytokines (IL-10, TGF-ß1, and TGF-ß2) in a time-dependent manner. In particular, recombinant C. sinensis protein treatment resulted in increase (at maximum) of ~7-fold in TGF-ß1, ~30-fold in TGF-ß2, and ~3-fold in TNF-α compared with the increase produced by ESPs, indicating that CsTrip1, CsLeg, and CsGrb2 function as strong inducers for secretion of these cytokines in host cells. These results suggest that C. sinensis ESPs contribute to the immunopathological response in host cells, leading to clonorchiasis-associated hepatobiliary abnormalities of greater severity.

Clonorchis sinensis excretory-secretory products increase malignant characteristics of cholangiocarcinoma cells in three-dimensional co-culture with biliary ductal plates.

Clonorchis sinensis is a carcinogenic human liver fluke, prolonged infection which provokes chronic inflammation, epithelial hyperplasia, periductal fibrosis, and even cholangiocarcinoma (CCA). These effects are driven by direct physical damage caused by the worms, as well as chemical irritation from their excretory-secretory products (ESPs) in the bile duct and surrounding liver tissues. We investigated the C. sinensis ESP-mediated malignant features of CCA cells (HuCCT1) in a three-dimensional microfluidic culture model that mimics an in vitro tumor microenvironment. This system consisted of a type I collagen extracellular matrix, applied ESPs, GFP-labeled HuCCT1 cells and quiescent biliary ductal plates formed by normal cholangiocytes (H69 cells). HuCCT1 cells were attracted by a gradient of ESPs in a concentration-dependent manner and migrated in the direction of the ESPs. Meanwhile, single cell invasion by HuCCT1 cells increased independently of the direction of the ESP gradient. ESP treatment resulted in elevated secretion of interleukin-6 (IL-6) and transforming growth factor-beta1 (TGF-ß1) by H69 cells and a cadherin switch (decrease in E-cadherin/increase in N-cadherin expression) in HuCCT1 cells, indicating an increase in epithelial-mesenchymal transition-like changes by HuCCT1 cells. Our findings suggest that C. sinensis ESPs promote the progression of CCA in a tumor microenvironment via the interaction between normal cholangiocytes and CCA cells. These observations broaden our understanding of the progression of CCA caused by liver fluke infection and suggest a new approach for the development of chemotherapeutic for this infectious cancer.

An improved reverse transcription loop-mediated isothermal amplification assay for sensitive and specific detection of serotype O foot-and-mouth disease virus.

A sensitive and specific swarm primer-based reverse transcription loop-mediated isothermal amplification (sRT-LAMP) assay for the detection of serotype O foot-and-mouth disease virus (FMDV) was developed and evaluated. The assay specifically amplified the VP3 gene of serotype O FMDV, but did not amplify the VP3 gene of other serotype FMDVs or any other viruses. The limit of detection of the assay was 102 TCID50/mL or 103 RNA copies/µL, which is 100 times lower than that of the RT-LAMP assay without swarm primers. The new assay is 10 times more sensitive than reverse transcription-polymerase chain reaction (RT-PCR) and is comparable to the sensitivity of real time RT-PCR (qRT-PCR). Evaluation of the assay using different serotypes of FMDV strains showed 100% agreement with the RT-PCR results. The previously reported serotype O FMDV-specific RT-LAMP assay did not detect 20 out of 22 strains of serotype O FMDVs, probably due to multiple mismatches between the primer and template sequences, showing that it is not suitable for detecting the serotype O FMDVs circulating in Pool 1 region countries, including Korea. In contrast, the developed sRT-LAMP assay with improved primers can rapidly and accurately diagnose serotype O FMDVs circulating in Pool 1 region countries and will be a useful alternative to RT-PCR and qRT-PCR.

Glutamate mediated metabolic neutralization mitigates propionate toxicity in intracellular Mycobacterium tuberculosis.

Metabolic networks in biological systems are interconnected, such that malfunctioning parts can be corrected by other parts within the network, a process termed adaptive metabolism. Unlike Bacillus Calmette-Guérin (BCG), Mycobacterium tuberculosis (Mtb) better manages its intracellular lifestyle by executing adaptive metabolism. Here, we used metabolomics and identified glutamate synthase (GltB/D) that converts glutamine to glutamate (Q → E) as a metabolic effort used to neutralize cytoplasmic pH that is acidified while consuming host propionate carbon through the methylcitrate cycle (MCC). Methylisocitrate lyase, the last step of the MCC, is intrinsically downregulated in BCG, leading to obstruction of carbon flux toward central carbon metabolism, accumulation of MCC intermediates, and interference with GltB/D mediated neutralizing activity against propionate toxicity. Indeed, vitamin B12 mediated bypass MCC and additional supplement of glutamate led to selectively correct the phenotypic attenuation in BCG and restore the adaptive capacity of BCG to the similar level of Mtb phenotype. Collectively, a defective crosstalk between MCC and Q → E contributes to attenuation of intracellular BCG. Furthermore, GltB/D inhibition enhances the level of propionate toxicity in Mtb. Thus, these findings revealed a new adaptive metabolism and propose GltB/D as a synergistic target to improve the antimicrobial outcomes of MCC inhibition in Mtb.

Crystal structure of Bacillus cereus flagellin and structure-guided fusion-protein designs.

Flagellin is a major component of the flagellar filament. Flagellin also functions as a specific ligand that stimulates innate immunity through direct interaction with Toll-like receptor 5 (TLR5) in the host. Because flagellin activates the immune response, it has been of interest to develop as a vaccine adjuvant in subunit vaccines or antigen fusion vaccines. Despite the widespread application of flagellin fusion in preventing infectious diseases, flagellin-antigen fusion designs have never been biophysically and structurally characterized. Moreover, flagellin from Salmonella species has been used extensively despite containing hypervariable regions not required for TLR5 that can cause an unexpected immune response. In this study, flagellin from Bacillus cereus (BcFlg) was identified as the smallest flagellin molecule containing only the conserved TLR5-activating D0 and D1 domains. The crystal structure of BcFlg was determined to provide a scheme for fusion designs. Through homology-based modeling and comparative structural analyses, diverse fusion strategies were proposed. Moreover, cellular and biophysical analysis of an array of fusion constructs indicated that insertion fusion at BcFlg residues 178-180 does not interfere with the protein stability or TLR5-stimulating capacity of flagellin, suggesting its usefulness in the development and optimization of flagellin fusion vaccines.

Investigation of bovine tuberculosis outbreaks by using a trace-back system and molecular typing in Korean Hanwoo beef cattle.

Bovine tuberculosis is a chronic contagious disease responsible for major agricultural economic losses. Abattoir monitoring and trace-back systems are an appropriate method to control bovine tuberculosis, particularly in beef cattle. In the present study, a trace-back system was applied to bovine tuberculosis cases in Korean native Hanwoo beef cattle. Bovine tuberculosis was detected in three index beef cattle during abattoir monitoring in Jeonbuk Province, Korea, and the original herds were traced back from each index cow. All cattle in each original herd were subjected to tuberculin skin test. The positive rates in the tuberculin skin test were 64.6% (62 of 96), 4.8% (2 of 42), and 8.1% (3 of 37) at farms A, B, and C, respectively. On post-mortem examination of 56 tuberculin-positive cattle, 62% had granulomatous lesions, and Mycobacterium bovis was cultured from 40 (71.4%) of the cattle. Molecular typing by spoligotyping and the mycobacterial interspersed repetitive unit-variable-number tandem repeat assay revealed the genotype of the M. bovis strains from the index cattle were same as the M. bovis genotype in each original herd. The results suggest that tracing back from index cattle to the original herd is an effective method to control bovine tuberculosis in beef cattle.

Characterization of Echinostoma cinetorchis endoribonuclease, RNase H.

Echinostoma cinetorchis is an oriental intestinal fluke causing significant pathological damage to the small intestine. The aim of this study was to determine a full-length cDNA sequence of E. cinetorchis endoribonuclease (RNase H; EcRNH) and to elucidate its molecular biological characters. EcRNH consisted of 308 amino acids and showed low similarity to endoribonucleases of other parasites (<40%). EcRNH had an active site centered on a putative DDEED motif instead of DEDD conserved in other species. A recombinant EcRNH produced as a soluble form in Escherichia coli showed enzymatic activity to cleave the 3'-O-P bond of RNA in a DNA-RNA duplex, producing 3'-hydroxyl and 5'-phosphate. These findings may contribute to develop antisense oligonucleotides which could damage echinostomes and other flukes.