Zika virus E protein dysregulate mir-204/WNT2 signalling in human fetal neural stem cells

Congenital Zika Virus Syndrome: Microcephaly and Orofacial Anomalies

The progressive reappearance of Zika virus (ZIKV) infections since October 2013 and its circulation in >70 countries and territories (from French Polynesia to Brazil and other countries in the Americas, with sporadic spread in Europe and the East) has long been reported as a global public health emergency. ZIKV is a virus transmitted by arthropods (arboviruses), mainly by Aedes mosquitoes. ZIKV can also be transmitted to humans through mechanisms other than vector infection such as sexual intercourse, blood transfusions, and mother-to-child transmission. The latter mode of transmission can give rise to a severe clinical form called congenital Zika syndrome (CZS), which can result in spontaneous abortion or serious pathological alterations in the fetus such as microcephaly or neurological and orofacial anomalies. In this study, beside a succinct overview of the etiological, microbiological, and epidemiological aspects and modes of transmission of Zika virus infections, we have focused our attention on the pathogenetic and histopathological aspects in pregnancy and the pathogenetic and molecular mechanisms that can determine microcephaly, and consequently the clinical alterations, typical of the fetus and newborns, in a subject affected by CZS.

Strain Variation Can Significantly Modulate the miRNA Response to Zika Virus Infection

Zika virus (ZIKV) is a mosquito-transmitted virus that has emerged as a major public health concern due to its association with neurological disorders in humans, including microcephaly in fetuses. ZIKV infection has been shown to alter the miRNA profile in host cells, and these changes can contain elements that are proviral, while others can be antiviral in action. In this study, the expression of 22 miRNAs in human A549 cells infected with two different ZIKV isolates was investigated. All of the investigated miRNAs showed significant changes in expression at at least one time point examined. Markedly, 18 of the miRNAs examined showed statistically significant differences in expression between the two strains examined. Four miRNAs (miR-21, miR-34a, miR-128 and miR-155) were subsequently selected for further investigation. These four miRNAs were shown to modulate antiviral effects against ZIKV, as downregulation of their expression through anti-miRNA oligonucleotides resulted in increased virus production, whereas their overexpression through miRNA mimics reduced virus production. However, statistically significant changes were again seen when comparing the two strains investigated. Lastly, candidate targets of the miRNAs miR-34a and miR-128 were examined at the level of the mRNA and protein. HSP70 was identified as a target of miR-34a, but, again, the effects were strain type-specific. The two ZIKV strains used in this study differ by only nine amino acids, and the results highlight that consideration must be given to strain type variation when examining the roles of miRNAs in ZIKV, and probably other virus infections.

Potential role of lncRNA in impairing cellular properties of human neural progenitor cells following exposure to Zika virus E protein

Zika virus (ZIKV) infection during the first trimester of the pregnancy may lead to Congenital zika syndrome in the neonates. The viral infection hampers foetal brain development and causes microcephaly. Human neural progenitor cells (hNPCs) play an important role in brain development, however they are highly susceptible to ZIKV infection. In this study, we elucidated the molecular mechanisms that lead to cellular alterations in hNPCs due to ZIKV E-protein. We investigated proliferation, differentiation, migration and inflammation in hNPCs, which may lead to microcephaly. In our study, we found that ZIKV E-protein causes cell cycle arrest, decrease in proliferation and increase in mitotic length of the dividing hNPCs. We observed CyclinD1 and upstream molecules (p21 and p53) of the pathway are dysregulated, and intracellular calcium at basal level as well as upon ATP stimulation were reduced following over expression of ZIKV E-protein. ZIKV E-protein transfected hNPCs exhibited pre-mature differentiation with pro-neural genes upregulated. Furthermore, ZIKV E-protein disrupted migrational properties of hNPCs and caused elevated levels of inflammatory chemokines and cytokines. To gain insights into molecular mechanisms of these effects on hNPCs, we explored the possible involvement of long non coding RNAs in ZIKV neuropathogenesis. We have shortlisted lncRNAs associated with differentially expressed genes from publicly available transcriptomic data and found some of those lncRNAs are differentially expressed upon E-protein transfection of hNPCs. Gene ontology analysis suggest these lncRNAs play an important role in regulation of viral life cycle, host's defence response and cell proliferation.

Zika virus E protein modulates functions of human brain microvascular endothelial cells and astrocytes: implications on blood-brain barrier properties

Neurotropic viruses can cross the otherwise dynamically regulated blood-brain barrier (BBB) and affect the brain cells. Zika virus (ZIKV) is an enveloped neurotropic Flavivirus known to cause severe neurological complications, such as encephalitis and fetal microcephaly. In the present study, we employed human brain microvascular endothelial cells (hBMECs) and astrocytes derived from human progenitors to establish a physiologically relevant BBB model. We used this model to investigate the effects of ZIKV envelope (E) protein on properties of cells comprising the BBB. E protein is the principal viral protein involved in interaction with host cell surface receptors, facilitating the viral entry. Our findings show that the presence of ZIKV E protein leads to activation of both hBMECs and astrocytes. In hBMECs, we observed a decrease in the expression of crucial endothelial junction proteins such as ZO-1, Occludin and VE-Cadherin, which are vital in establishment and maintenance of the BBB. Consequently, the ZIKV E protein induced changes in BBB integrity and permeability. We also found upregulation of genes involved in leukocyte recruitment along with increased proinflammatory chemokines and cytokines upon exposure to E protein. Additionally, the E protein also led to astrogliosis, evident from the elevated expression of GFAP and Vimentin. Both cell types comprising the BBB exhibited inflammatory response upon exposure to E protein which may influence viral access into the central nervous system (CNS) and subsequent infection of other CNS cells. Overall, our study provides valuable insights into the transient changes that occur at the site of BBB upon ZIKV infection.

Modulation of cellular machineries by Zika virus-encoded proteins

The strain of Zika virus (ZIKV) that circulated during the 2015 epidemic in Brazil has been associated with more than 2000 cases of microcephaly from September 2015 through November 2016. The viral genome determines the biology and pathogenesis of a virus and the virus employs its own gene products to evade host immune surveillance, manipulate cellular machineries, and establish efficient replication. Therefore, understanding the functions of virus-encoded protein not only aids the knowledge of ZIKV biology but also guides the development of anti-ZIKV drugs. In this review, we focus on 10 proteins encoded by ZIKV and summarize their functions in ZIKV replication and pathogenesis according to studies published in the past 6 years.

miR-204-5p Inhibits the Proliferation and Differentiation of Fetal Neural Stem Cells by Targeting Wingless-Related MMTV Integration Site 2 to Regulate the Ephrin-A2/EphA7 Pathway

Neonatal hypoxic ischemic encephalopathy (HIE) is mainly resulted from perinatal asphyxia, which can be repaired by NSCs. miR-204-5p is claimed to impact the activity NSCs. Our research will probe the miR-204-5p function in oxygen-glucose deprivation (OGD)-treated NSCs. miR-204-5p level was enhanced and WNT2 level was reduced in HIE rats. Rat NSCs were stimulated with OGD condition under the managing of mimic or inhibitor of miR-204-5p. The declined cell viability, enhanced apoptosis, downregulated Tuj1 and GFAP levels, and shortened total neurite length were observed in OGD-treated NSCs, which were further aggravated by the mimic and rescued by the inhibitor of miR-204-5p. Furthermore, the inactivated WNT2 and Ephrin-A2/EphA7 signaling pathway in OGD-stimulated NSCs was further repressed by the mimic and rescued by the inhibitor of miR-204-5p. In addition, WNT2 was confirmed as the targeting of miR-204-5p. Lastly, the function of miR-204-5p mimic on the proliferation, apoptosis, differentiation, WNT2 and Ephrin-A2/EphA7 signaling pathway in OGD-stimulated NSCs was abolished by HLY78, an activator of Wnt signaling. Collectively, miR-204-5p repressed the growth and differentiation of fetal NSCs by targeting WNT2 to regulate the Ephrin-A2/EphA7 pathway.

Regulatory Role of Host MicroRNAs in Flaviviruses Infection

MicroRNAs (miRNAs) are small non-coding RNA that affect mRNA abundance or translation efficiency by binding to the 3′UTR of the mRNA of the target gene, thereby participating in multiple biological processes, including viral infection. Flavivirus genus consists of small, positive-stranded, single-stranded RNA viruses transmitted by arthropods, especially mosquitoes and ticks. The genus contains several globally significant human/animal pathogens, such as Dengue virus, Japanese encephalitis virus, West Nile virus, Zika virus, Yellow fever virus, Tick-borne encephalitis virus, and Tembusu virus. After flavivirus invades, the expression of host miRNA changes, exerting the immune escape mechanism to create an environment conducive to its survival, and the altered miRNA in turn affects the life cycle of the virus. Accumulated evidence suggests that host miRNAs influence flavivirus replication and host–virus interactions through direct binding of viral genomes or through virus-mediated host transcriptome changes. Furthermore, miRNA can also interweave with other non-coding RNAs, such as long non-coding RNA and circular RNA, to form an interaction network to regulate viral replication. A variety of non-coding RNAs produced by the virus itself exert similar function by interacting with cellular RNA and viral RNA. Understanding the interaction sites between non-coding RNA, especially miRNA, and virus/host genes will help us to find targets for antiviral drugs and viral therapy.