Multifaceted Roles of microRNAs in Host-Bacterial Pathogen Interaction

A Review on miRNAs in Enteric Bacteria-mediated Host Pathophysiology: Mechanisms and Implications

Recently, many studies focused on the billions of native bacteria found inside and all over the human body, commonly known as the microbiota, and its interactions with the eukaryotic host. One of the niches for such microbiota is the gastrointestinal tract (GIT), which harbors hundreds to thousands of bacterial species commonly known as enteric bacteria. Changes in the enteric bacterial populations were linked to various pathologies such as irritable bowel syndrome and obesity. The gut microbiome could affect the health status of individuals. MicroRNAs (miRNAs) are one of the extensively studied small-sized noncoding RNAs (ncRNAs) over the past decade to explore their multiple roles in health and disease. It was proven that miRNAs circulate in almost all body fluids and tissues, showing signature patterns of dysregulation associated with pathologies. Both cellular and circulating miRNAs participate in the posttranscriptional regulation of genes and are considered the potential key regulators of genes and participate in cellular communication. This manuscript explores the unique interplay between miRNAs and enteric bacteria in the gastrointestinal tract, emphasizing their dual role in shaping host-microbiota dynamics. It delves into the molecular mechanisms by which miRNAs influence bacterial colonization and host immune responses, linking these findings to gut-related diseases. The review highlights innovative therapeutic and diagnostic opportunities, offering insights for targeted treatments of dysbiosis-associated pathologies.

Exploring the regulatory role of small RNAs in modulating host-pathogen interactions: implications for bacterial and viral infections

MicroRNAs (miRNAs) and transfer RNA-derived stress-induced RNAs (tiRNAs) have emerged as crucial players in the post-transcriptional regulation of gene expression in various cellular processes, including immunity and host defense against infections. In recent years, increasing evidence has highlighted their complex role in influencing the host response during viral and bacterial infections. miRNAs have been shown to play multiple roles in host-pathogen interaction like TLR activation and altered disease virulence during bacterial infections. In the context of viral infections, miRNAs are involved in regulating viral replication, pathogenesis, and immune evasion. Similarly, tiRNAs have recently emerged as novel players in bacterial and viral infections such as modulating bacterial growth, adaptation to stress conditions, host antiviral responses, and impacting viral replication and pathogenesis. This review provides a comprehensive analysis of the potential of miRNA expression profiles as diagnostic biomarkers to differentiate between bacterial and viral infections. Further discusses the key pathways through which small RNAs regulate bacterial and viral infection-related diseases.

In Silico Hybridization and Molecular Dynamics Simulations for the Identification of Candidate Human MicroRNAs for Inhibition of Virulent Proteins' Expression in Staphylococcus aureus

Staphylococcus aureus is a major threat to human health, causing infections that range in severity from moderate to fatal. The rising rates of antibiotic resistance highlight the critical need for new therapeutic techniques to combat this infection. It has been recently discovered that microRNAs (miRNAs) are essential for cross-kingdom communication, especially when it comes to host-pathogen interactions. It has been demonstrated that these short noncoding RNAs control gene expression in the gut microbiota, maintaining homeostasis; dysbiosis in this system has been linked to several diseases, including cancer. Our research attempts to use this understanding to target specific bacterial species and prevent severe diseases. In particular, we look for putative human miRNAs that can attach to virulent bacterial proteins' mRNA and prevent them from being expressed. In-silico hybridization experiments were performed between 100 human miRNA sequences with varied expression levels in gram-positive bacterial infections and five virulence factor genes. In addition, these miRNAs' binding properties were investigated using molecular dynamics (MD) simulations. Our findings demonstrate that human miRNAs can target and inhibit the expression of bacterial virulent genes, thereby opening up new paths for developing innovative miRNA-based therapeutics. The implementation of MD simulations in our study not only improves the validity of our findings but also proposes a new method for constructing miRNA-based therapies against life-threatening bacterial infections.

Unraveling the role of LncRNAs in glioblastoma progression: insights into signaling pathways and therapeutic potential

Glioblastoma (GBM) is one of the most aggressive types of brain cancer, characterized by its poor prognosis and low survival rate despite current treatment modalities. Because GBM is lethal, clarifying the pathogenesis's underlying mechanisms is important, which are still poorly understood. Recent discoveries in the fields of molecular genetics and cancer biology have demonstrated the critical role that non-coding RNAs (ncRNAs), especially long non-coding RNAs (lncRNAs), play in the molecular pathophysiology of GBM growth. LncRNAs are transcripts longer than 200 nucleotides that do not encode proteins. They are significant epigenetic modulators that control gene e expression at several levels. Their dysregulation and interactions with important signaling pathways play a major role in the malignancy and development of GBM. The increasing role of lncRNAs in GBM pathogenesis is thoroughly examined in this review, with particular attention given to their regulation mechanisms in key signaling pathways such as PI3K/AKT, Wnt/β-catenin, and p53. It also looks into lncRNAs' potential as new biomarkers and treatment targets for GBM. In addition, the study discusses the difficulties in delivering lncRNA-based medicines across the blood-brain barrier and identifies areas that need more research to advance lncRNA-oriented treatments for this deadly cancer.

Expression profiles of miRNAs in the lung tissue of piglets infected with Glaesserella parasuis and the roles of ssc-miR-135 and ssc-miR-155-3p in the regulation of inflammation

MicroRNAs (miRNAs) have been shown to play an important regulatory role in the process of pathogenic infection. However, the miRNAs that regulate the pathogenic process of G. parasuis and their functions are still unknown. Here, high-throughput sequencing was used to quantify the expression of miRNA in piglet lung tissue after G. parasuis XX0306 strain infection. A total of 25 differentially expressed microRNAs (DEmiRNAs) were identified. GO and KEGG pathway enrichment analysis showed that many of the functions of genes that may be regulated by DEmiRNA are related to inflammatory response and immune regulation. Further studies found that ssc-miR-135 may promote the expression of inflammatory factors through NF-κB signaling pathway. Whereas, ssc-miR-155-3p inhibited the inflammatory response induced by G. parasuis, and its regulatory mechanism remains to be further investigated. This study provides a valuable reference for revealing the regulatory effects of miRNAs on the pathogenesis of G. parasuis. DATA AVAILABILITY: The datasets generated during the current study are not publicly available due to this study is currently in the ongoing research stage, and some of the data cannot be made public sooner yet, but are available from the corresponding author on reasonable request.

Long Non-Coding RNAs and Their "Discrete" Contribution to IBD and Johne's Disease-What Stands out in the Current Picture? A Comprehensive Review

Non-coding RNAs (ncRNA) have paved the way to new perspectives on the regulation of gene expression, not only in biology and medicine, but also in associated fields and technologies, ensuring advances in diagnostic means and therapeutic modalities. Critical in this multistep approach are the associations of long non-coding RNA (lncRNA) with diseases and their causal genes in their networks of interactions, gene enrichment and expression analysis, associated pathways, the monitoring of the involved genes and their functional roles during disease progression from one stage to another. Studies have shown that Johne's Disease (JD), caused by Mycobacterium avium subspecies partuberculosis (MAP), shares common lncRNAs, clinical findings, and other molecular entities with Crohn's Disease (CD). This has been a subject of vigorous investigation owing to the zoonotic nature of this condition, although results are still inconclusive. In this review, on one hand, the current knowledge of lncRNAs in cells is presented, focusing on the pathogenesis of gastrointestinal-related pathologies and MAP-related infections and, on the other hand, we attempt to dissect the associated genes and pathways involved. Furthermore, the recently characterized and novel lncRNAs share common pathologies with IBD and JD, including the expression, molecular networks, and dataset analysis results. These are also presented in an attempt to identify potential biomarkers pertinent to cattle and human disease phenotypes.

Comparative microRNA profiling of Trypanosoma cruzi infected human cells

Introduction

Trypanosoma cruzi, the causative agent of Chagas disease, can infect almost any nucleated cell in the mammalian host. Although previous studies have described the transcriptomic changes that occur in host cells during parasite infection, the understanding of the role of post-transcriptional regulation in this process is limited. MicroRNAs, a class of short non-coding RNAs, are key players in regulating gene expression at the post-transcriptional level, and their involvement in the host-T. cruzi interplay is a growing area of research. However, to our knowledge, there are no comparative studies on the microRNA changes that occur in different cell types in response to T. cruzi infection.

Methods and results

Here we investigated microRNA changes in epithelial cells, cardiomyocytes and macrophages infected with T. cruzi for 24 hours, using small RNA sequencing followed by careful bioinformatics analysis. We show that, although microRNAs are highly cell type-specific, a signature of three microRNAs -miR-146a, miR-708 and miR-1246, emerges as consistently responsive to T. cruzi infection across representative human cell types. T. cruzi lacks canonical microRNA-induced silencing mechanisms and we confirm that it does not produce any small RNA that mimics known host microRNAs. We found that macrophages show a broad response to parasite infection, while microRNA changes in epithelial and cardiomyocytes are modest. Complementary data indicated that cardiomyocyte response may be greater at early time points of infection.

Conclusions

Our findings emphasize the significance of considering microRNA changes at the cellular level and complement previous studies conducted at higher organizational levels, such as heart samples. While miR-146a has been previously implicated in T. cruzi infection, similarly to its involvement in many other immunological responses, miR-1246 and miR-708 are demonstrated here for the first time. Given their expression in multiple cell types, we anticipate our work as a starting point for future investigations into their role in the post-transcriptional regulation of T. cruzi infected cells and their potential as biomarkers for Chagas disease.

Transcriptome-wide identification and characterization of the Macrobrachium rosenbergii microRNAs potentially related to immunity against non-O1 Vibrio cholerae infection

Non-O1 Vibrio cholerae, a member of the Vibrio family, could cause gastrointestinal infection of Macrobrachium rosenbergii and result in significant economic losses. However, few studies on microRNA immunity related to non-O1 V. cholerae infection of M. rosenbergii. The aim of this study was to elucidate the mechanism of miRNA in the potential immune response of M. rosenbergii. to non-O1 V. cholerae MSVC-GY01 infection by transcriptome sequencing. Following quality screening, the control group received 10, 616, 712 clean reads, whereas the infected group received 9,727,616. The miRNA sequences in the two samples are extremely consistent and have a length of roughly 23 nt. In all, 871 known miRNAs were discovered, with 279 differentially expressed miRNAs (DEMs). Meanwhile, 62 novel miRNAs were predicted, including 43 DEMs. In order to understand the immune-related biological functions of DEMs, target genes were predicted. Pathway function annotation analysis showed that non-O1 V. cholerae affected the NOD-like receptor signaling pathway, RIG-I-like receptor signaling pathway, and Toll-like receptor signaling pathway, suggesting that miRNAs in the hepatopancreas play a key role in immune responses to pattern recognition receptors. Twelve DEMs were randomly selected for Quantitative Real-time PCR (qRT-PCR). Overall, the expression trends of qRT-PCR were consistent with the sequencing results. These findings corroborate the immunomodulatory function of miRNA in M. rosenbergii against non-O1 V. cholerae infection and provide guidance for the prevention and treatment of related illnesses.

Identification and characterization of microRNAs, especially gga-miR-181b-5p, in chicken macrophages associated with avian pathogenic E. coli infection

AbstractAvian pathogenic E. coli (APEC) is a common pathogen in the poultry industry, which can cause substantial economic losses. Recently, emerging evidence showed that the miRNAs were involved in various viral and bacterial infection. To elucidate the role of miRNAs in chicken macrophages in response to APEC infection, we attempted to investigate the miRNAs expression pattern upon APEC infection via miRNA-seq, and to identify the molecular mechanism of the important miRNAs by using RT-qPCR, Western blotting, dual-luciferase reporter assay, and CCK-8. Results showed that a total of 80 differentially expressed (DE) miRNAs were identified in the comparison of APEC vs. wild type group, which corresponded to 724 target genes. Moreover, the target genes of the identified DE miRNAs were mainly significantly enriched in MAPK signaling pathway, Autophagy-animal, mTOR signaling pathway, ErbB signaling pathway, Wnt signaling pathway, TGF-beta signaling pathway. Remarkably, gga-miR-181b-5p is capable to participate in host immune and inflammatory response against APEC infection via targeting of TGFBR1 to modulate the activation of TGF-beta signaling pathway. Collectively, this study provides a perspective of miRNA expression pattern in chicken macrophages upon APEC infection. These findings provide the insight into miRNAs against APEC infection and gga-miR-181b-5p might be a potential target for treating APEC infection.

Epigenetic changes induced by pathogenic Chlamydia spp

Chlamydia trachomatis, C. pneumoniae, and C. psittaci, the three Chlamydia species known to cause human disease, have been collectively linked to several pathologies, including conjunctivitis, trachoma, respiratory disease, acute and chronic urogenital infections and their complications, and psittacosis. In vitro, animal, and human studies also established additional correlations, such as between C. pneumoniae and atherosclerosis and between C. trachomatis and ovarian cancer. As part of their survival and pathogenesis strategies as obligate intracellular bacteria, Chlamydia spp. modulate all three major types of epigenetic changes, which include deoxyribonucleic acid (DNA) methylation, histone post-translational modifications, and microRNA-mediated gene silencing. Some of these epigenetic changes may be implicated in key aspects of pathogenesis, such as the ability of the Chlamydia spp. to induce epithelial-to-mesenchymal transition, interfere with DNA damage repair, suppress cholesterol efflux from infected macrophages, act as a co-factor in human papillomavirus (HPV)-mediated cervical cancer, prevent apoptosis, and preserve the integrity of mitochondrial networks in infected host cells. A better understanding of the individual and collective contribution of epigenetic changes to pathogenesis will enhance our knowledge about the biology of Chlamydia spp. and facilitate the development of novel therapies and biomarkers. Pathogenic Chlamydia spp. contribute to epigenetically-mediated gene expression changes in host cells by multiple mechanisms.

Uncovering the role of microRNA671-5p/CDCA7L/monoamine oxidase-A signaling in Helicobacter pylori mediated apoptosis in gastric epithelial cells

Helicobacter pylori is a gram-negative microaerophilic bacterium and is associated with gastrointestinal diseases ranging from peptic ulcer and gastritis to gastric cancer and mucosa-associated lymphoid tissue lymphoma. In our laboratory, the transcriptomes and miRnomes of AGS cells infected with H. pylori have been profiled, and an miRNA-mRNA network has been constructed. MicroRNA 671-5p is upregulated during H. pylori infection of AGS cells or of mice. In this study, the role of miR-671-5p during infection has been investigated. It has been validated that miR-671-5p targets the transcriptional repressor CDCA7L, which is downregulated during infection (in vitro and in vivo) concomitant with miR-671-5p upregulation. Further, it has been established that the expression of monoamine oxidase A (MAO-A) is repressed by CDCA7L, and that MAO-A triggers the generation of reactive oxygen species (ROS). Consequently, miR-671-5p/CDCA7L signaling is linked to the generation of ROS during H. pylori infection. Finally, it has been demonstrated that ROS-mediated caspase 3 activation and apoptosis that occurs during H. pylori infection, is dependent on the miR-671-5p/CDCA7L/MAO-A axis. Based on the above reports, it is suggested that targeting miR-671-5p could offer a means of regulating the course and consequences of H. pylori infection.

MicroRNAs: master regulators in host-parasitic protist interactions

MicroRNAs (miRNAs) are a group of small non-coding RNAs present in a wide diversity of organisms. MiRNAs regulate gene expression at a post-transcriptional level through their interaction with the 3' untranslated regions of target mRNAs, inducing translational inhibition or mRNA destabilization and degradation. Thus, miRNAs regulate key biological processes, such as cell death, signal transduction, development, cellular proliferation and differentiation. The dysregulation of miRNAs biogenesis and function is related to the pathogenesis of diseases, including parasite infection. Moreover, during host-parasite interactions, parasites and host miRNAs determine the probability of infection and progression of the disease. The present review is focused on the possible role of miRNAs in the pathogenesis of diseases of clinical interest caused by parasitic protists. In addition, the potential role of miRNAs as targets for the design of drugs and diagnostic and prognostic markers of parasitic diseases is also discussed.

MicroRNA hsa-let-7a facilitates staphylococcal small colony variants survival in the THP-1 macrophages by reshaping inflammatory responses

Recent studies have provided emerging evidence of the critical involvement of microRNAs in host immune defence against bacterial infection and that likewise the expression of the miRNAs is profoundly impacted by a variety of pathogens to subvert the immune response. Here, we report the role of hsa-let-7a miRNA in response to Staphylococcus epidermidis Small Colony Variants infection. We also assessed whether the expression levels of inflammatory cytokines associated with the hsa-let-7a are manipulated by the pathogen and the effect of the IFN-γ priming on the expression of hsa-let-7a and the fate of SCVs/WTs in infected macrophages. A striking observation was the downregulation of the let-7a miRNA upon challenge of the THP-1 activated cells with the SCV isolates while no significant changes in expression were noticed after the infection of macrophages with their WT counterparts. Staphylococcus epidermidis WT and SCV strains were found to invade and survive in macrophages. A significant reduction in bacterial load for both phenotypes was observed in macrophages treated with let-7a mimic compared to untreated ones. Survival of WTs was augmented in cells treated with the inhibitor in 4 out of 5 strains as compared to the number of bacteria recovered from non-transfected cells. At the same time, let-7a inhibitor did not influence on the survival of SCVs in macrophages as their number was comparable to number recovered from non-transfected cells. When the ratio of both let-7a cytokine targets was compared, anti-inflammatory IL-10 cytokine was induced by SCVs predominantly, while the macrophage challenge with WTs was characterized by the inflammatory cytokine profile with high IL-6 and low IL-10 production. Moreover, the balance between pro-inflammatory and anti-inflammatory cytokines has been expectedly retrieved when macrophages were transfected with let-7a mimic before infection with WT or SCV strains. The results also show that IFN-γ likely regulates the macrophage environment contributing to the inflammatory response and elimination of bacteria from intracellular milieu by augmenting the synthesis of pro-inflammatory cytokines and supressing the anti-inflammatory IL-10. Our work has shown that SCVs have the potential to regulate the let-7a miRNA to balance the pro-inflammatory IL-6 with anti-inflammatory IL-10 and this mechanism is one of the ways in a complex regulatory network adopted by SCVs to promote their survival.

MiR-279-3p regulates deltamethrin resistance through CYP325BB1 in Culex pipiens pallens

Background

The overuse of insecticides to control insect vectors has promoted extensive insecticide resistance in mosquitoes. In this study, the functions of microRNA (miR)-279-3p and its target CYP325BB1 in the regulation of deltamethrin resistance in Culex pipiens pallens was investigated.

Methods

Quantitative real-time reverse transcription PCR was used to detect the expression levels of miR-279-3p and CYP325BB1. Then, the dual-luciferase reporter assay system, RNA interference, CDC bottle bioassay and Cell Counting Kit-8 (CCK-8) assay were used to explore the roles of these molecules in deltamethrin resistance both in vivo and in vitro.

Results

The expression patterns of miR-279-3p and CYP325BB1 were compared between deltamethrin-sensitive (DS-strain) and deltamethrin-resistant (DR-strain) mosquitoes. Luciferase activity was downregulated by miR-279-3p, the effect of which was ablated by a mutation of the putative binding site for CYP325BB1. In DR-strain mosquitoes, the expression of miR-279-3p was increased by microinjection and oral feeding of miR-279-3p agomir (mimic). CYP325BB1 mRNA levels were downregulated, which resulted in a higher mortality of the mosquitoes in miR-279-3p mimic-treated groups. In the DS-strain mosquitoes, microinjection of a miR-279-3p inhibitor decreased miR-279-3p expression, whereas the expression of CYP325BB1 was increased; the mortality of these mosquitoes decreased significantly. In addition, overexpression of pIB/V5-His-CYP325BB1 changed the sensitivity of C6/36 cells to deltamethrin in vitro. Also in DR-strain mosquitoes, downregulation of CYP325BB1 expression by microinjection of si-CYP325BB1 increased mosquito mortality in vivo.

Conclusions

These findings provide empirical evidence of the involvement of miRNAs in the regulation of insecticide resistance and indicate that miR-279-3p suppresses the expression of CYP325BB1, which in turn decreases deltamethrin resistance, resulting in increased mosquito mortality. Taken together, the results provide important information for use in the development of future mosquito control strategies.

Graphical abstract

Diagnostic predictability of miR-4535 and miR-1915-5p expression in amniotic fluid for foetal morbidity of infection

INTRODUCTION

Clinical prediction of foetal inflammatory response syndrome (FIRS) is highly necessary. We have previously reported that miR-4535 and miR-1915-5p are potential biomarkers for severe chorioamnionitis based on the results of microRNA array analysis. Therefore, we evaluated the relationship between foetal morbidity of infection and miR-4535, miR-1915-5p, interleukin (IL)-6, or 16S rDNA copy number levels in amniotic fluid from pregnant women with chorioamnionitis.

METHODS

Amniotic fluid from 57 pregnant women with preterm premature membrane rupture or threatened premature labour were collected. Infants with WBC counts <5000/μL or >20,000/μL, CRP >0.5 mg/mL, or IgM >20 mg/mL at birth received a diagnosis of suspicious foetal infection, and those requiring antibiotic administration for >5 days were considered infected newborns. miR-4535, miR-1915-5p, and IL-6 levels and 16S rDNA copy number were evaluated. Mann-Whitney U test and Dunn's test were used for comparison. The area under the curve (AUC) and Youden index were calculated to examine the diagnostic accuracy of foetal morbidity of infection.

RESULTS

miR-4535, miR-1915-5p, 16S rDNA, and IL-6 were significantly higher in patients with severe chorioamnionitis than in patients with chorionitis or sub-chorionitis (P < 0.05). miR-4535 and miR-1915-5p levels were significantly associated with WBC counts <5000/μL or >20,000/μL, CRP >0.5 mg/mL, or IgM >20 mg/mL (P < 0.05). AUC values of miR-4535 and miR-1915-5p indicated moderate or low accuracy for foetal morbidity of infection, while those of IL-6 and 16S rDNA seemed unreliable.

DISCUSSION

MiR-4535 and miR-1915-5p levels in amniotic fluid may be considered clinically predictive for foetal morbidity of infection.

Reprogramming of microRNA expression via E2F1 downregulation promotes Salmonella infection both in infected and bystander cells

Cells infected with pathogens can contribute to clearing infections by releasing signals that instruct neighbouring cells to mount a pro-inflammatory cytokine response, or by other mechanisms that reduce bystander cells’ susceptibility to infection. Here, we show the opposite effect: epithelial cells infected with Salmonella Typhimurium secrete host factors that facilitate the infection of bystander cells. We find that the endoplasmic reticulum stress response is activated in both infected and bystander cells, and this leads to activation of JNK pathway, downregulation of transcription factor E2F1, and consequent reprogramming of microRNA expression in a time-dependent manner. These changes are not elicited by infection with other bacterial pathogens, such as Shigella flexneri or Listeria monocytogenes. Remarkably, the protein HMGB1 present in the secretome of Salmonella-infected cells is responsible for the activation of the IRE1 branch of the endoplasmic reticulum stress response in non-infected, neighbouring cells. Furthermore, E2F1 downregulation and the associated microRNA alterations promote Salmonella replication within infected cells and prime bystander cells for more efficient infection.

Cells infected with pathogens can release signals that instruct neighbouring cells to mount an immune response or that reduce these cells’ susceptibility to infection. Here, Aguilar et al. show the opposite effect: cells infected with Salmonella Typhimurium secrete host factors that facilitate the infection of bystander cells by activating their ER-stress response.

Probiotics and MicroRNA: Their Roles in the Host-Microbe Interactions

Probiotics are widely accepted to be beneficial for the maintenance of the gut homeostasis - the dynamic and healthy interactions between host and gut microorganisms. In addition, emerging as a key molecule of inter-domain communication, microRNAs (miRNAs) can also mediate the host-microbe interactions. However, a comprehensive description and summary of the association between miRNAs and probiotics have not been reported yet. In this review, we have discussed the roles of probiotics and miRNAs in host-microbe interactions and proposed the association of probiotics with altered miRNAs in various intestinal diseases and potential molecular mechanisms underlying the action of probiotics. Furthermore, we provided a perspective of probiotics-miRNA-host/gut microbiota axis applied in search of disease management highly associated with the gut microbiome, which will potentially prove to be beneficial for future studies.

A Novel MicroRNA From the Translated Region of the Giardiavirus rdrp Gene Governs Virus Copy Number in Giardia duodenalis

Giardia duodenalis is an important zoonotic parasite that can cause human and animal diarrhea. Giardiavirus (GLV) is a double-stranded RNA virus in Totiviridae family, which specifically infects trophozoites of the primitive protozoan parasite G. duodenalis. However, the GLV infectious and the pathogenicity of the G. duodenalis still remain to be confirmed. The GLV genome is 6,277 bp, which encodes two proteins (Gag and Gag-Pol). The expression of Gag-Pol protein is regulated by a-1 ribosomal frameshift. In this report, we identified a novel microRNA (GLV miRNA1) from the GLV. Split ligation northern results showed that GLV miRNA1 is a special expression product of GLV, and the precursor was also identified by primer extension. Antisense sequence of the GLV miRNA1 could increase the copy number of virus in G. duodenalis. It suggests that GLV miRNA1 governs the copy number of Giardiavirus in G. duodenalis. Most importantly, the GLV miRNA1 lies at the translated region of the rdrp gene, which is the first case that microRNA locates in the translated region of a known protein. It may be implying a novel phenomenon for miRNA biogenesis.