Chandipura virus changes cellular miRNome in human microglial cells.

Chandipura virus (CHPV) is a neurotropic virus, known to cause encephalitis in humans. The microRNAs (miRNA/miR) play an important role in the pathogenesis of viral infection. The present study is focused on the role of miRNAs during CHPV (strain 1653514) infection in human microglial cells. The deep sequencing of CHPV-infected human microglial cells identified a total of 12 differentially expressed miRNA (DEMs). To elucidate the role of DEMs, the target gene prediction, Gene Ontology term (GO Term), pathway enrichment analysis, and miRNA-messenger RNA (mRNA) interaction network analysis was performed. The GO terms and pathway enrichment analysis provided 146 enriched genes; which were involved in interferon response, cytokine and chemokine signaling. Further, the WGCNA (weighted gene coexpression network analysis) of the enriched genes were discretely categorized into three modules (blue, brown, and turquoise). The hub genes in the blue module may correlate to CHPV induced neuroinflammation. Altogether, the miRNA-mRNA interaction network and WGCNA study revealed the following pairs, hsa-miR-542-3p and FAF1, hsa-miR-92a-1-5p and MYD88, and hsa-miR-3187-3p and TNFRSF21, which may contribute to neuroinflammation during CHPV infection in human microglial cells.

Chandipura virus dysregulates the expression of hsa-miR-21-5p to activate NF-κB in human microglial cells.

BACKGROUND: Chandipura virus (CHPV) is a negative single-stranded RNA virus of the Rhabdoviridae family. CHPV infection has been reported in Central and Western India. CHPV causes acute encephalitis with a case fatality rate of 70 % and mostly affects children below 15 years of age. CHPV infection in brain leads to neuronal apoptosis and activation of the microglial cells. The microRNAs (miRNAs) are small endogenous non-coding RNA that regulate the gene expression. Viral infections perturb the expression pattern of cellular miRNAs, which may in turn affect the expression pattern of downstream genes. This study aims to investigate hsa-miR-21-5p mediated regulation of PTEN, AKT, NF-ĸBp65, IL-6, TNF-α, and IL-1ß, in human microglial cells during CHPV infection. METHODS: To understand the role of hsa-miR-21-5p in CHPV infection, the human microglial cells were infected with CHPV (MOI-0.1). Real-time PCR, western blotting, Luciferase assay, over-expression and knockdown techniques were used to understand the role of hsa-miR-21-5p in the regulation of PTEN, AKT and, NF-ĸBp65, IL-6, TNF-α, and IL-1ß in this study. RESULTS: The hsa-miR-21-5p was found to be upregulated during CHPV infection in human microglial cells. This led to the downregulation of PTEN which promoted the phosphorylation of AKT and NF-ĸBp65. Over-expression of hsa-miR-21-5p led to the decreased expression of PTEN and promoted further phosphorylation of AKT and NF-ĸBp65 in human microglial cells. However, the inhibition of hsa-miR-21-5p using hsa-miR-21-5p inhibitor restored the expression. CONCLUSIONS: This study supports the role of hsa-miR-21-5p in the regulation of pro-inflammatory genes in CHPV infected human microglial cells.

Chikungunya virus modulates the miRNA expression patterns in human synovial fibroblasts.

Chikungunya virus (CHIKV) is an alphavirus transmitted by mosquitoes. CHIKV infection leads to polyarthritis and polyarthralgia among patients. The synovial fibroblasts are the primary target for CHIKV. The microRNAs (miRNAs) are the small endogenous noncoding RNAs which posttranscriptionally regulate the expression of genes by binding to their target messenger RNAs (mRNAs) through their 3'-untranslated regions. The miRNAs are the key regulators for various pathological processes including viral infection, cancer, cardiovascular disease, and neurodegeneration. This study was designed to dissect out the roles of miRNAs during CHIKV (Ross Strain E1: A226V) infection in primary human synovial fibroblasts. The miRNA microarray profiling was performed on the primary human synovial fibroblasts infected by CHIKV. The gene target prediction analysis, enrichment, and network analysis were performed by various bioinformatics analyses. The subset of 26 differentially expressed microRNAs (DEMs) were identified through microarray profiling and were further screened for gene predictions, Gene Ontology, pathway enrichment, and miRNA-mRNA network using various bioinformatics tools. The bioinformatics analysis indicates the role of DEMs by suppressing the immune response which may contribute to CHIKV persistence in human primary synovial fibroblasts. Our study provides the plausible roles of DEMs, miRNAs, and mRNA interactions and pathways involved in the molecular pathogenesis of CHIKV.

SARS coronavirus 2: from genome to infectome.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) belongs to the group of Betacoronaviruses. The SARS-CoV-2 is closely related to SARS-CoV-1 and probably originated either from bats or pangolins. SARS-CoV-2 is an etiological agent of COVID-19, causing mild to severe respiratory disease which escalates to acute respiratory distress syndrome (ARDS) or multi-organ failure. The virus was first reported from the animal market in Hunan, Hubei province of China in the month of December, 2019, and was rapidly transmitted from animal to human and human-to-human. The human-to-human transmission can occur directly or via droplets generated during coughing and sneezing. Globally, around 53.9 million cases of COVID-19 have been registered with 1.31 million confirmed deaths. The people > 60 years, persons suffering from comorbid conditions and immunocompromised individuals are more susceptible to COVID-19 infection. The virus primarily targets the upper and the lower respiratory tract and quickly disseminates to other organs. SARS-CoV-2 dysregulates immune signaling pathways which generate cytokine storm and leads to the acute respiratory distress syndrome and other multisystemic disorders.

Exploitation of microRNAs by Japanese Encephalitis virus in human microglial cells.

JEV infection in CNS leads to the JE neuroinflammation. Children and old age individual have been reported to be more prone to JEV infection. MicroRNAs are endogenous, small non-coding RNAs, which regulate the gene expression. These are ∼22 nucleotide long, conserved RNA sequence that binds at the 3'UTR of a target mRNA and regulate the post-transcriptional gene expression. The role of microRNAs has been reported in several diseases like cancer, viral infection, neuro-degeneration, diabetes etc. In the present study, the human microglial cells were infected with JEV (JaOArS982). The control and infected samples were subject to microarray profiling for microRNA expression. The microarray profile yielded differentially expressed microRNAs from JEV infected samples. The microRNA gene targets, gene ontology, annotations, and pathways were identified through various bioinformatics tools. Additionally, the pathways were mostly found common to "ubiquitin mediated proteolysis," "cytokine signaling," "maintenance of barrier function/cell junctions," JAK/STAT pathway" "Toll-like receptor signaling," "Wnt-signaling," "adhesion molecules," "apoptosis," "endocytosis," "vesicle mediated transport" etc.

Implications of non-coding RNAs in viral infections.

The advances in RNA sequencing have unveiled various non-coding RNAs (ncRNAs), which modulate the gene expression. ncRNAs do not get translated into proteins. These include transfer RNAs, ribosomal RNAs, microRNA (miRNA), short interfering RNA, long non-coding RNA, piwi-interacting RNA and small nuclear RNA. ncRNAs regulate gene expression at various levels and control cellular machinery. miRNAs have been reported in plants, animals, several invertebrates and viruses. The miRNAs regulate the gene expression post-transcriptionally. Viral infection strongly influences the abundance and the distribution of miRNAs and other ncRNAs within the host cells. Viruses may encode their own miRNA, which help in the viral life cycle and other aspects of pathogenesis. Viruses are known to successfully modulate the expression pattern of ncRNAs. The ncRNA-based strategies adopted by viruses for their survival present a complex picture of host-virus interactions. Copyright © 2016 John Wiley & Sons, Ltd.

Middle East Respiratory Syndrome Virus Pathogenesis.

Coronaviruses (CoVs) are enveloped RNA viruses that infect birds, mammals, and humans. Infections caused by human coronaviruses (hCoVs) are mostly associated with the respiratory, enteric, and nervous systems. The hCoVs only occasionally induce lower respiratory tract disease, including bronchitis, bronchiolitis, and pneumonia. In 2002 to 2003, a global outbreak of severe acute respiratory syndrome (SARS) was the seminal detection of a novel CoV (SARS-CoV). A decade later (June 2012), another novel CoV was implicated as the cause of Middle East respiratory syndrome (MERS) in Saudi Arabia. Although bats might serve as a reservoir of MERS-CoV, it is unlikely that they are the direct source for most human cases. Severe lines of evidence suggest that dromedary camels have been the major cause of transmission to humans. The emergence of MERS-CoV has triggered serious concerns about the potential for a widespread outbreak. All MERS cases were linked directly or indirectly to the Middle East region including Saudi Arabia, Jordan, Qatar, Oman, Kuwait, and UAE. MERS cases have also been reported in the later phases in the United Kingdom, France, Germany, Italy, Spain, and Tunisia. Most of these MERS cases were linked with the Middle East. The high mortality rates in family-based and hospital-based outbreaks were reported among patients with comorbidities such as diabetes and renal failure. MERS-CoV causes an acute, highly lethal pneumonia and renal dysfunction. The major complications reported in fatal cases are hyperkalemia with associated ventricular tachycardia, disseminated intravascular coagulation, pericarditis, and multiorgan failure. The case-fatality rate seems to be higher for MERS-CoV (around 30%) than for SARS-CoV (9.6%). The combination regimen of type 1 interferon + lopinavir/ritonavir is considered as the first-line therapy for MERS. Antiviral treatment is generally recommended for 10 to 14 days in patients with MERS-CoV infection. Convalescent plasma therapy has shown some efficacy among patients refractory to antiviral drugs if administered within 2 weeks of the onset of the disease.

miR-146a suppresses cellular immune response during Japanese encephalitis virus JaOArS982 strain infection in human microglial cells.

BACKGROUND: Japanese encephalitis virus (JEV) is the causative agent of Japanese encephalitis which is more prevalent in South and Southeast Asia. JEV is a neurotropic virus which infiltrates into the brain through vascular endothelial cells. JEV infects neurons and microglial cells which causes neuronal damage and inflammation. However, JEV also evades the cellular immune response to survive in host cells. Viruses are known to modulate the expression of microRNAs, which in turn modulate cellular immune response by targeting expression of antiviral genes. The aim of this study is to understand the anti-inflammatory role of miR-146a during JEV infection, which facilitates immune evasion. METHODS: Human brain microglial cells (CHME3) were infected by JEV: JaOArS982 and P20778 strain, and expression of miR-146a were analyzed. Overexpression and knockdown studies of miR-146a were done to see the effect on NF-κB pathway and antiviral Jak-STAT pathway. Regulatory role of miR-146a on expression of interferon-stimulated genes was determined by real-time PCR and luciferase assays. RESULTS: JEV infection elevated the expression of miR-146a in JaOArS982 strain which caused downregulation of TRAF6, IRAK1, IRAK2, and STAT1 genes. Exogenous overexpression of miR-146a led to suppression of NF-κB activation and abrogation of Jak-STAT pathway upon JEV infection which led to downregulation of interferon-stimulated genes (IFIT-1 and IFIT-2) and facilitated viral replication. JEV infection initially upregulated cytokine production and activated STAT1 activity but STAT1 levels reduced at later time point, which led to the downregulation of interferon-stimulated genes. CONCLUSION: Upregulation of miR-146a by JEV JaOArS982 strain leads to suppression of NF-κB activity and disruption of antiviral Jak-STAT signaling which helps the virus to evade the cellular immune response. This effect of JEV infection on miR-146a expression was found to be strain specific.

HIV Tat protein: Is Tat-C much trickier than Tat-B?

Out of various subtypes of human immunodeficiency virus type 1 (HIV-1), subtype B and C cause most of the infections worldwide. Clade specific differences have been reported in differences in clinical picture of HIV pathogenesis. Transcription of the HIV-1 genome is regulated by the interaction of HIV Tat protein to the trans-activation response (TAR) element. The differential binding of clade B and C Tat proteins to TAR and differences in activation of NF-κB cascade leading to differential transactivation capacity and cytokine expression has been examined in this study. More stable Tat-TAR complex formation by Tat-C revealed by EMSA and higher TNF-α expression shown by Tat-C compared to Tat-B leads to higher NF-κB activation, which may be plausible cause for higher transactivation by Tat-C as obtained by FACS analysis. This comparative study would be helpful in understanding the basic mechanism of clade specific Tat protein differences and their functional relationships.

HIV-1 Tat C modulates NOX2 and NOX4 expressions through miR-17 in a human microglial cell line.

HIV-1 invades CNS in the early course of infection, which can lead to the cascade of neuroinflammation. NADPH oxidases (NOXs) are the major producers of reactive oxygen species (ROS), which play important roles during pathogenic insults. The molecular mechanism of ROS generation via microRNA-mediated pathway in human microglial cells in response to HIV-1 Tat protein has been demonstrated in this study. Over-expression and knockdown of microRNAs, luciferase reporter assay, and site-directed mutagenesis are main molecular techniques used in this study. A significant reduction in miR-17 levels and increased NOX2, NOX4 expression levels along with ROS production were observed in human microglial cells upon HIV-1 Tat C exposure. The validation of NOX2 and NOX4 as direct targets of miR-17 was done by luciferase reporter assay. The over-expression and knockdown of miR-17 in human microglial cells showed the direct role of miR-17 in regulation of NOX2, NOX4 expression and intracellular ROS generation. We demonstrated the regulatory role of cellular miR-17 in ROS generation through over-expression and knockdown of miR-17 in human microglial cells exposed to HIV-1 Tat C protein. Activated microglial cells mediated neuroinflammatory events are observed in HIV-associated neurological disorders. The reduction in miR-17 levels was observed in microglial cells exposed to HIV-1 Tat C protein. miR-17 regulated the expression of NOX2 and NOX4, which in turn regulated the reactive oxygen species (ROS) production in microglial cells. Increased ROS production led to the activation of microglial cells and increased cytokine production. This study thus demonstrated a novel miR-17-mediated regulatory pathway of ROS production in microglial cells. HMC3 = human microglia clone 3 cell lines.

Regulatory role of TRIM21 in the type-I interferon pathway in Japanese encephalitis virus-infected human microglial cells.

BACKGROUND: Japanese encephalitis virus (JEV) infection leads to Japanese encephalitis (JE) in humans. JEV is transmitted through mosquitoes and maintained in a zoonotic cycle. This cycle involves pigs as the major reservoir, water birds as carriers and mosquitoes as vectors. JEV invasion into the central nervous system (CNS) may occur via antipodal transport of virions or through the vascular endothelial cells. Microglial cells get activated in response to pathogenic insults. JEV infection induces the innate immune response and triggers the production of type I interferons. The signaling pathway of type I interferon production is regulated by a number of molecules. TRIM proteins are known to regulate the expression of interferons; however, the involvement of TRIM genes and their underlying mechanism during JEV infection are not known. METHODS: Human microglial cells (CHME3) were infected with JEV to understand the role of TRIM21 in JEV infection and its effect on type I interferon (IFN-ß) production. Cells were infected in presence and absence of exogenous TRIM21 as well as after knocking down the TRIM21 mRNA. Levels of activated IRF3 expression were measured through Western blot analyses of anti-p-IRF3 antibody, and IFN-ß production was measured by using IFN-ß real-time PCR and luciferase activity analyses. RESULTS: JEV infection increased expression of TRIM21 in CHME3 cells. JEV induced an innate immune response by increasing production of IFN-ß via IRF3 activation and phosphorylation. Overexpression of TRIM21 resulted in downregulation of p-IRF3 and IFN-ß, while silencing led to increased production of p-IRF3 and IFN-ß in JEV-infected CHME3 cells. CONCLUSION: This report demonstrates TRIM21 as a negative regulator of interferon-ß (IFN-ß) production mediated by IRF-3 during JEV infection in human microglial cells.

Hypoxia-Induced miR-101 Impairs Endothelial Barrier Integrity Through Altering VE-Cadherin and Claudin-5.

Stroke is a life-threatening medical condition across the world that adversely affects the integrity of the blood-brain barrier (BBB). The brain microvascular endothelial cells are the important constituent of the BBB. These cells line the blood vessels and form a semipermeable barrier. Disruptions in adherens junction and tight junction proteins of brain microvascular endothelial cells compromise the integrity of BBB. The Vascular Endothelial (VE)-cadherin is an integral adherens junction protein required for the establishment and maintenance of the endothelial barrier integrity. This study aims to investigate the role of miRNA in hypoxia-induced endothelial barrier disruption. In this study, brain endothelial cells were exposed to hypoxic conditions for different time points. Western blotting, overexpression and knockdown of miRNA, real-time PCR, TEER, and sodium fluorescein assay were used to examine the effect of hypoxic conditions on brain endothelial cells. Hypoxic exposure was validated using HIF-1α protein. Exposure to hypoxic conditions resulted to a significant decrease in endothelial barrier resistance and an increase in sodium fluorescein migration across the endothelial barrier. Reduction in endothelial barrier resistance demonstrated compromised barrier integrity, whereas the increase in migration of sodium fluorescein across the barrier indicated the increase in barrier permeability. The present study revealed microRNA-101 decreases the expression of VE-cadherin and claudin-5 in brain endothelial cells exposed to the hypoxic conditions.

ORF3a of SARS-CoV-2 modulates PI3K/AKT signaling in human lung epithelial cells via hsa-miR-155-5p.

SARS-CoV-2 infection results in cytokine burst, leading to proinflammatory responses in lungs of COVID-19 patients. SARS-CoV-2 ORF3a triggers the generation of proinflammatory cytokines. However, the underlying mechanism of dysregulation of proinflammatory responses is not well understood. We studied the role of microRNA in the generation of proinflammatory responses as a bystander effect of SARS-CoV-2 ORF3a in human lung epithelial cells. We observed upregulation of hsa-miR-155-5p in SARS-CoV-2 ORF3a transfected human lung epithelial cells, which led to the reduced expression of SHIP1. This resulted in phosphorylation of AKT and NF-κB, which further led to the increased expression of the proinflammatory cytokines IL-6 and TNF-α. Additionally, overexpression and knockdown studies of hsa-miR-155-5p were performed to confirm the role of hsa-miR-155-5p in the regulation of the SHIP1. We demonstrated that hsa-miR-155-5p modulates the proinflammatory response by activating the PI3K/AKT pathway through the inhibition of SHIP1 in SARS-CoV-2 ORF3a transfected human lung epithelial cells.

Direct antimicrobial effects of chemokines on Cryptococcus spp, with special emphasis on a 'CXC' chemokine.

Cryptococcus species are ingenious human pathogens that are widespread globally. They continue to cause over 200,000 deaths per year. Presently due to the rise in resistance and therapy failure, it is necessary to shift the focus to an alternate therapeutic strategy against this pathogen. One promising approach is to emphasize the host defense system in order to develop more precise and customized treatment strategies. In this regard, research has revealed that interferon-γ-inducible CXCL10 chemokine, amongst other chemokines spanning both CXC and CC categories, has a direct killing effect in vitro against Cryptococcus neoformans and Cryptococcus gattii, with a significantly greater microbicidal effect against the former. Moreover, when CXCL10 is used in combination with CCL5, there is a significant reduction in the survival of C. gattii at normal-serum level concentration, indicating a previously unreported synergistic effect of these two chemokines. Confocal and STED microscopic studies have demonstrated that CXCL10 has both cell wall/membrane and intracellular targets against this fungus. These findings present new possibilities for developing chemokine-derived small molecule antifungals and may represent a step forward in creating precision medicine tailored to each patient.

MicroRNA-155 triggers a cellular antiviral immune response against Chandipura virus in human microglial cells.

Chandipura virus (CHPV) belongs to the family Rhabdoviridae and has a single-stranded RNA genome that causes encephalitis among children in India's tropical states. Activation of the antiviral immune response upon viral infection is important for the host's defense. In response to CHPV infection, the brain resident macrophages (microglial cells) control the pathogenic insults. The microRNAs (miRNAs) are 22 nts non-coding RNAs that serve as delicate regulators of their target genes at the post-transcriptional level. In this study, we explored miR-155 mediated antiviral response in CHPV infected human microglial cells. The gene and protein expression patterns were studied through quantitative real-time PCR (qPCR) and immunoblotting, respectively. Additionally, miRNA target validation was done by overexpression and knockdown of miR-155. We observed an increased expression of miR-155 in CHPV infected human microglial cells. The upregulated miR-155 suppresses the Suppressor of Cytokine Signalling 1 (SOCS1). Reduced SOCS1, in turn, led to enhanced phosphorylation of Signal Transducer and Activator of Transcription 1 (STAT1) and induction of Interferon-ß (IFN-ß), which promoted the expression of IFN-stimulated gene 54 (ISG54) and IFN-stimulated gene 56 (ISG56). In this study, miR-155 positively modulated the cellular antiviral response by enhancing type I IFN signalling through inhibition of SOCS1 in CHPV infected microglial cells.

Zika virus NS1 suppresses VE-cadherin via hsa-miR-29b-3p/DNMT3b/MMP-9 pathway in human brain microvascular endothelial cells.

Zika virus infection has been reported to cause microcephaly in newborns. ZIKV exploits various strategies to cross the blood-brain barrier. ZIKV NS1 may compromise the barrier integrity of endothelial cells by regulating expression of junctional proteins. MicroRNAs play an important role in post-transcriptional gene regulations. We demonstrated that ZIKV-NS1 affected the adherence junction protein in human brain microvascular endothelial cells via hsa-miR-29b-3p/DNMT3b/MMP-9 pathway. The hCMEC/D3 cells were exposed to ZIKV-NS1 with different doses (500 ng/mL and 1000 ng/mL) for 24 h. The expression pattern of DNTM3b, MMP-9, and VE-cadherin were studied using immunoblotting and the distribution of DNMT3b and MMP-9 were studied using immunofluorescence. The quantification of hsa-miR-29b-3p was done through qRT-PCR. Direct regulation of DNMT3b by hsa-miR-29b-3p was demonstrated by overexpression of hsa-miR-29b-3p using hsa-miR-29b-3p mimic, and knockdown of hsa-miR-29b-3p by using hsa-miR-29b-3p inhibitors. The ZIKV-NS1 affected the barrier function of endothelial cells through the increased expression of hsa-miR29b-3p, which suppressed the DNMT3b, thus enhanced expression of MMP-9, which finally suppressed the expression of VE-cadherin. These findings suggested that ZIKV-NS1 alters the expression of Adherens Junction protein in human brain microvascular endothelial cells through hsa-miR-29b-3p/DNMT3b/MMP-9 pathway, which compromised the barrier function of human brain microvascular endothelial cells.

Zika Virus NS1 Suppresses VE-Cadherin and Claudin-5 via hsa-miR-101-3p in Human Brain Microvascular Endothelial Cells.

Zika virus (ZIKV) is a neurotropic virus that causes microcephaly in newborns and Guillain-Barré syndrome (GBS) in adults. ZIKV is known to transmigrate through the blood-brain barrier (BBB) by utilizing different strategies. NS1 is a conserved flavivirus protein, which is secreted extracellularly. ZIKV-NS1 has been shown to target adherens junctions (AJs) and tight junctions (TJs) to disrupt the endothelial barrier integrity. The microRNAs are short non-coding RNAs, which post-transcriptionally regulate the gene expression by binding to 3' UTR of the target gene. In the present study, we studied the ZIKV-NS1-mediated effect through hsa-miR-101-3p on the junctional barrier integrity in human brain microvascular endothelial cells. We exposed hBMVECs and hCMEC/D3 cells with ZIKV-NS1 at different time points (12 h and 24 h) with the doses 500 ng/mL and 1000 ng/mL. The change in the expression of VE-cadherin and claudin-5 was quantified using immunoblotting. The expression of the hsa-miR-101-3p was quantified using qRT-PCR. To prove the targeting of hsa-miR-101-3p to VE-cadherin, we transfected hsa-miR-101-3p mimic, scramble, hsa-miR-101-3p inhibitor, and Cy3 in the ZIKV-NS1-exposed hCMEC/D3 cells. The distribution and expression of the VE-cadherin and claudin-5 were observed using immunofluorescence and immunoblotting. The ZIKV-NS1 compromises the endothelial barrier integrity by disrupting the VE-cadherin and claudin-5 protein expression via hsa-miR-101-3p. The findings of this study suggest that ZIKV-NS1 dysregulates the adherens junction and tight junction proteins through hsa-miR-101-3p, which compromises the barrier integrity of human brain microvascular endothelial cells.

Zika virus NS1 suppresses the innate immune responses via miR-146a in human microglial cells.

Zika virus (ZIKV) is a positive-single strand RNA virus that belongs to the Flaviviridae family. ZIKV infection causes congenital ZIKV syndrome (CZS) in children and Guillain Barre Syndrome (GBS) in adults. ZIKV infected cells secrete non-structural protein 1 (sNS1), which plays an important role in viral replication and immune evasion. The microglial cells are the brain resident macrophages that mediate the immune responses in CNS. The miRNAs are small non-coding RNAs that regulate the expression of their target genes by binding to the 3'UTR region. The present study highlights the bystander effect of ZIKV-NS1 via miR-146a. The Real-Time PCR, Immunoblotting, overexpression, knockdown studies, and reactive oxygen species measurement have been done to study the immunomodulatory effects of ZIKV-NS1 in human microglial cells. ZIKV-NS1 induced the expression of miR-146a and suppressed the ROS activity in human microglial cells. The up-regulated miR-146a led to the decreased expression of TRAF6 and STAT-1. The reduced expression of TRAF6 in turn led to the suppression of pNF-κBp65 and TNF-α downstream. The miR-146a suppressed the pro-inflammatory and cellular antiviral responses in microglial cells. Our findings demonstrate the bystander role of ZIKV-NS1 in suppressing the pro-inflammatory and cellular antiviral responses through miR-146a in human microglial cells.

Gist of Zika Virus pathogenesis.

Zika virus (ZIKV) is a mosquito-borne neurotropic flavivirus. ZIKV infection may lead to microcephaly in developing fetus and Guillain-Barré Syndrome (GBS) like symptoms in adults. ZIKV was first reported in humans in 1952 from Uganda and the United Republic of Tanzania. Later, ZIKV outbreak was reported in 2007 from the Yap Island. ZIKV re-emerged as major outbreak in the year 2013 from French Polynesia followed by second outbreak in the year 2015 from Brazil. ZIKV crosses the blood-tissue barriers to enter immune-privileged organs. Clinical manifestations in ZIKV disease includes rash, fever, conjunctivitis, muscle and joint pain, headache, transverse myelitis, meningoencephalitis, Acute Disseminated Encephalomyelitis (ADEM). The understanding of the molecular mechanism of ZIKV pathogenesis is very important to develop potential diagnostic and therapeutic interventions for ZIKV infected patients.