Exposure to Zika and chikungunya viruses impacts aspects of the vectorial capacity of Aedes aegypti and Culex quinquefasciatus.

Zika (ZIKV) and chikungunya (CHIKV) are arboviruses that cause infections in humans and can cause clinical complications, representing a worldwide public health problem. Aedes aegypti is the primary vector of these pathogens and Culex quinquefasciatus may be a potential ZIKV vector. This study aimed to evaluate fecundity, fertility, survival, longevity, and blood feeding activity in Ae. aegypti after exposure to ZIKV and CHIKV and, in Cx. quinquefasciatus exposed to ZIKV. Three colonies were evaluated: AeCamp (Ae. aegypti-field), RecL (Ae. aegypti-laboratory) and CqSLab (Cx. quinquefasciatus-laboratory). Seven to 10 days-old females from these colonies were exposed to artificial blood feeding with CHIKV or ZIKV. CHIKV caused reduction in fecundity and fertility in AeCamp and reduction in survival and fertility in RecL. ZIKV impacted survival in RecL, fertility in AeCamp and, fecundity and fertility in CqSLab. Both viruses had no effect on blood feeding activity. These results show that CHIKV produces a higher biological cost in Ae. aegypti, compared to ZIKV, and ZIKV differently alters the biological performance in colonies of Ae. aegypti and Cx. quinquefasciatus. These results provide a better understanding over the processes of virus-vector interaction and can shed light on the complexity of arbovirus transmission.

Gain without pain: adaptation and increased virulence of Zika virus in vertebrate host without fitness cost in mosquito vector.

IMPORTANCE: Previously, we modeled direct transmission chains of Zika virus (ZIKV) by serially passaging ZIKV in mice and mosquitoes and found that direct mouse transmission chains selected for viruses with increased virulence in mice and the acquisition of non-synonymous amino acid substitutions. Here, we show that these same mouse-passaged viruses also maintain fitness and transmission capacity in mosquitoes. We used infectious clone-derived viruses to demonstrate that the substitution in nonstructural protein 4A contributes to increased virulence in mice.

Transcriptomic reveals the ferroptosis features of host response in a mouse model of Zika virus infection.

Zika virus (ZIKV) is a neurotropic flavivirus. The outbreak of ZIKV in 2016 created a global health emergency. However, the underlying pathogenic mechanisms remain elusive. We investigated the host response features of in vivo replication in a mouse model of ZIKV infection, by performing a series of transcriptomic and bioinformatic analyses of ZIKV and mock-infected brain tissue. Tissue damage, inflammatory cells infiltration and high viral replication were observed in the brain tissue of ZIKV infected mice. RNA-Seq of the brain indicated the activation of ferroptosis pathways. Enrichment analysis of ferroptosis regulators revealed their involvement in pathways such as mineral absorption, fatty acid biosynthesis, fatty acid degradation, PPAR signaling pathway, peroxidase, and adipokinesine signalling pathway. We then identified 12 interacted hub ferroptosis regulators (CYBB, HMOX1, CP, SAT1, TF, SLC39A14, FTL, LPCAT3, FTH1, SLC3A2, TP53, and SLC40A1) that were related to the differential expression of CD8+ T cells, microglia and monocytes. CYBB, HMOX1, SALT, and SLAC40A1 were selected as potential biomarkers of ZIKV infection. Finally, we validated our results using RT-qPCR and outside available datasets. For the first time, we proposed a possible mechanism of ferroptosis in brain tissue infected by ZIKV in mice and identified the four key ferroptosis regulators.

Os sentidos produzidos por cuidadoras escolares de crianças com SCZV / Los sentidos producidos por cuidadores escolares de niños con SCZV / The senses produced by school caregivers of children with SCZV

RESUMO. Este estudo, fundamentado na perspectiva da psicologia cultural-histórica sobre a pessoa com deficiência, teve por objetivo apreender a dimensão subjetiva da realidade (ou as mediações) das crianças com a Síndrome Congênita do Zika Vírus (SCZV) no contexto escolar de desenvolvimento e aprendizagem a partir dos sentidos produzidos por cuidadoras escolares. Para tal, foram realizadas entrevistas semiestruturadas com três cuidadoras escolares que trabalham em três creches pertencentes ao sistema de educação de ensino de Campina Grande/PB. Para análise dos dados, foi realizado o procedimento dos Núcleos de Significação, que visa à apreensão das contradições que constituem as produções de significação discursiva dos sujeitos participantes. Os resultados indicaram que as cuidadoras escolares priorizam a mediação pedagógica na relação estabelecida com as crianças com SCZV, embora não desconsiderem a instância do cuidado em termos das necessidades especiais relacionadas à integridade psicomotora que essas crianças apresentam. Ademais, foi evidenciado que as participantes salientam as potencialidades das crianças em detrimento da falta ou lesão gerada pela deficiência.

RESUMEN. Este estudio, basado en la perspectiva de la psicología cultural-histórica sobre las personas con discapacidad, tenía como objetivo apreciar la dimensión subjetiva de la realidad de los niños con Síndrome Congénito del Virus del Zika (SCVZ). en el contexto escolar del desarrollo y el aprendizaje de los significados producidos por los cuidadores escolares. Para ello, se realizaron entrevistas semiestructuradas con tres cuidadores escolares de guarderías diferentes que pertenecen al sistema educativo de Campina Grande/PB. Para el análisis de datos, se realizó el procedimiento de los núcleos de significación, cuyo objetivo es aprehender las contradicciones que constituyen las producciones de significado discursiva de los participantes. Los resultados indicaron que los cuidadores de la escuela dan prioridad a la mediación pedagógica en la relación establecida con los niños con SCVZ, aunque no descuidan la instancia de cuidado en cuanto a las necesidades especiales relacionadas con la integridad psicomotora que tienen estos niños. Además, se destacó que los participantes ponen de relieve el potencial de los niños en detrimento de la falta o lesión generada por la discapacidad.

ABSTRACT This study is based by the perspective of the cultural-historical psychology on people with disabilities, aimed to apprehend the subjective dimension of the reality (or mediations) of children with Congenital Zika Virus Syndrome (CZVS) on the school context development and learning from the senses produced by school children caregivers. For this reason, semi-structured interviews were conducted with three caregivers working in three daycare centers belonging to the teaching system of education in Campina Grande/PB. For data analysis, was performed the meaning core, which aims to apprehend the contradictions that constitute the productions of discursive meaning in the participating subjects. The results indicated that school caregivers prioritize the mediation in the relationship established with children CZVS, though not disregard the instance of care in terms of the special needs related to psychomotor integrity that these children have. Furthermore, it was evidenced that the participants emphasize the children's potentialities to the detriment of the lack or injury generated by the disability.

Pathogenicity and Structural Basis of Zika Variants with Glycan Loop Deletions in the Envelope Protein.

The glycan loop of Zika virus (ZIKV) envelope protein (E) contains the glycosylation site and has been well documented to be important for viral pathogenesis and transmission. In the present study, we report that deletions in the E glycan loop, which were recorded in African ZIKV strains previously, have re-emerged in their contemporary Asian lineages. Here, we generated recombinant ZIKV containing specific deletions in the E glycan loop by reverse genetics. Extensive in vitro and in vivo characterization of these deletion mutants demonstrated an attenuated phenotype in an adult A129 mouse model and reduced oral infections in mosquitoes. Surprisingly, these glycan loop deletion mutants exhibited an enhanced neurovirulence phenotype, and resulted in a more severe microcephalic brain in neonatal mouse models. Crystal structures of the ZIKV E protein and a deletion mutant at 2.5 and 2.6 Å, respectively, revealed that deletion of the glycan loop induces encephalitic flavivirus-like conformational alterations, including the appearance of perforations on the surface and a clear change in the topology of the loops. Overall, our results demonstrate that the E glycan loop deletions represent neonatal mouse neurovirulence markers of ZIKV. IMPORTANCE Zika virus (ZIKV) has been identified as a cause of microcephaly and acquired evolutionary mutations since its discovery. Previously deletions in the E glycan loop were recorded in African ZIKV strains, which have re-emerged in the contemporary Asian lineages recently. The glycan loop deletion mutants are not glycosylated, which are attenuated in adult A129 mouse model and reduced oral infections in mosquitoes. More importantly, the glycan loop deletion mutants induce an encephalitic flavivirus-like conformational alteration in the E homodimer, resulting in a significant enhancement of neonatal mouse neurovirulence. This study underscores the critical role of glycan loop deletion mutants in ZIKV pathogenesis, highlighting a need for global virological surveillance for such ZIKV variants.

Zika virus causes placental pyroptosis and associated adverse fetal outcomes by activating GSDME.

Zika virus (ZIKV) can be transmitted from mother to fetus during pregnancy, causing adverse fetal outcomes. Several studies have indicated that ZIKV can damage the fetal brain directly; however, whether the ZIKV-induced maternal placental injury contributes to adverse fetal outcomes is sparsely defined. Here, we demonstrated that ZIKV causes the pyroptosis of placental cells by activating the executor gasdermin E (GSDME) in vitro and in vivo. Mechanistically, TNF-α release is induced upon the recognition of viral genomic RNA by RIG-I, followed by activation of caspase-8 and caspase-3 to ultimately escalate the GSDME cleavage. Further analyses revealed that the ablation of GSDME or treatment with TNF-α receptor antagonist in ZIKV-infected pregnant mice attenuates placental pyroptosis, which consequently confers protection against adverse fetal outcomes. In conclusion, our study unveils a novel mechanism of ZIKV-induced adverse fetal outcomes via causing placental cell pyroptosis, which provides new clues for developing therapies for ZIKV-associated diseases.

A Reverse Mutation E143K within the PrM Protein of Zika Virus Asian Lineage Natal RGN Strain Increases Infectivity and Cytopathicity.

Zika virus (ZIKV) is a positive-sense single-stranded RNA virus in the Flaviviridae, which is classified into two different lineages Asian and African. The outbreak of ZIKV Asian lineage isolates in 2015-2016 is associated with the increase in cases with prenatal microcephaly and Guillain-Barré syndrome, and has sparked attention throughout the world. Genome sequence alignment and the analysis of Asian and African lineage isolates indicate that amino acid changes, particular in positively charged amino acid substitutions in the pr region of prM protein might involve a phenotypic change that links with the global outbreak of ZIKV Asian-lineage. The study generated and characterized the virological properties of wild type and mutants of single-round infectious particles (SRIPs) and infectious clones (i.c.s) of ZIKV Asian-lineage Natal RGN strain, and then identified the function of amino acid substitutions at the positions 139 [Asn139→Ser139 (N139S)] and 143 [Glu143→Lys143 (E143K)] in ZIKV polyproteins (located within the pr region of prM protein) in the infectivity and cytopathogenicity. The E143K SRIP and i.c. of Natal RGN strain exhibited relatively higher levels of cytopathic effect, EGFP reporter, viral RNA and protein synthesis, and virus yield in three types of human cell lines, TE617, SF268 and HMC3, compared to wild type (WT), N139S SRIPs and i.c.s, which displayed more efficiency in replication kinetics. Additionally, E143K Natal RGN i.c. had greater activities of virus attachment and entry, yielded higher titers of intracellular and extracellular virions, and assembled the E proteins near to the plasma membrane in infected cells than the other i.c.s. The results indicate that the positively charged amino acid residue Lys143, a conserved residue in the pr region of prM of ZIKV African lineages, plays a crucial role in viral replication kinetics, including viral attachment, entry, assembly and egress. Thus, the negatively charged amino acid residue Glu143 within the pr region of prM leads to an alteration of the phenotypes, in particular, a lower replication efficiency of ZIKV Asian-lineage isolates with the attenuation of infectivity and cytopathicity.

Apoptosis during ZIKA Virus Infection: Too Soon or Too Late?

Cell death by apoptosis is a major cellular response in the control of tissue homeostasis and as a defense mechanism in the case of cellular aggression such as an infection. Cell self-destruction is part of antiviral responses, aimed at limiting the spread of a virus. Although it may contribute to the deleterious effects in infectious pathology, apoptosis remains a key mechanism for viral clearance and the resolution of infection. The control mechanisms of cell death processes by viruses have been extensively studied. Apoptosis can be triggered by different viral determinants through different pathways as a result of virally induced cell stresses and innate immune responses. Zika virus (ZIKV) induces Zika disease in humans, which has caused severe neurological forms, birth defects, and microcephaly in newborns during the last epidemics. ZIKV also surprised by revealing an ability to persist in the genital tract and in semen, thus being sexually transmitted. Mechanisms of diverting antiviral responses such as the interferon response, the role of cytopathic effects and apoptosis in the etiology of the disease have been widely studied and debated. In this review, we examined the interplay between ZIKV infection of different cell types and apoptosis and how the virus deals with this cellular response. We illustrate a duality in the effects of ZIKV-controlled apoptosis, depending on whether it occurs too early or too late, respectively, in neuropathogenesis, or in long-term viral persistence. We further discuss a prospective role for apoptosis in ZIKV-related therapies, and the use of ZIKV as an oncolytic agent.

Host cytoskeletal vimentin serves as a structural organizer and an RNA-binding protein regulator to facilitate Zika viral replication.

Emerging microbe infections, such as Zika virus (ZIKV), pose an increasing threat to human health. Investigations on ZIKV replication have revealed the construction of replication complexes (RCs), but the role of cytoskeleton in this process is largely unknown. Here, we investigated the function of cytoskeletal intermediate filament protein vimentin in the life cycle of ZIKV infection. Using advanced imaging techniques, we uncovered that vimentin filaments undergo drastic reorganization upon viral protein synthesis to form a perinuclear cage-like structure that embraces and concentrates RCs. Genetic removal of vimentin markedly disrupted the integrity of RCs and resulted in fragmented subcellular dispersion of viral proteins. This led to reduced viral genome replication, viral protein production, and release of infectious virions, without interrupting viral binding and entry. Furthermore, mass spectrometry and RNA-sequencing screens identified interactions and interplay between vimentin and hundreds of endoplasmic reticulum (ER)-resident RNA-binding proteins. Among them, the cytoplasmic-region of ribosome receptor binding protein 1, an ER transmembrane protein that directly binds viral RNA, interacted with and was regulated by vimentin, resulting in modulation of ZIKV replication. Together, the data in our work reveal a dual role for vimentin as a structural element for RC integrity and as an RNA-binding-regulating hub during ZIKV infection, thus unveiling a layer of interplay between Zika virus and host cell.

Novel Epidemic Metrics to Communicate Outbreak Risk at the Municipality Level: Dengue and Zika in the Dominican Republic.

Arboviruses remain a significant cause of morbidity, mortality and economic cost across the global human population. Epidemics of arboviral disease, such as Zika and dengue, also cause significant disruption to health services at local and national levels. This study examined 2014-2016 Zika and dengue epidemic data at the sub-national level to characterise transmission across the Dominican Republic. For each municipality, spatio-temporal mapping was used to characterise disease burden, while data were age and sex standardised to quantify burden distributions among the population. In separate analyses, time-ordered data were combined with the underlying disease migration interval distribution to produce a network of likely transmission chain events, displayed using transmission chain likelihood matrices. Finally, municipal-specific reproduction numbers (Rm) were established using a Wallinga-Teunis matrix. Dengue and Zika epidemics peaked during weeks 39-52 of 2015 and weeks 14-27 of 2016, respectively. At the provincial level, dengue attack rates were high in Hermanas Mirabal and San José de Ocoa (58.1 and 49.2 cases per 10,000 population, respectively), compared with the Zika burden, which was highest in Independencia and San José de Ocoa (21.2 and 13.4 cases per 10,000 population, respectively). Across municipalities, high disease burden was observed in Cotuí (622 dengue cases per 10,000 population) and Jimani (32 Zika cases per 10,000 population). Municipal infector-infectee transmission likelihood matrices identified seven 0% likelihood transmission events throughout the dengue epidemic and two 0% likelihood transmission events during the Zika epidemic. Municipality reproduction numbers (Rm) were consistently higher, and persisted for a greater duration, during the Zika epidemic (Rm = 1.0) than during the dengue epidemic (Rm < 1.0). This research highlights the importance of disease surveillance in land border municipalities as an early warning for infectious disease transmission. It also demonstrates that a high number of importation events are required to sustain transmission in endemic settings, and vice versa for newly emerged diseases. The inception of a novel epidemiological metric, Rm, reports transmission risk using standardised spatial units, and can be used to identify high transmission risk municipalities to better focus public health interventions for dengue, Zika and other infectious diseases.

Gain-of-function genetic screening identifies the antiviral function of TMEM120A via STING activation.

Zika virus (ZIKV) infection can be associated with neurological pathologies, such as microcephaly in newborns and Guillain-Barre syndrome in adults. Effective therapeutics are currently not available. As such, a comprehensive understanding of virus-host interactions may guide the development of medications for ZIKV. Here we report a human genome-wide overexpression screen to identify host factors that regulate ZIKV infection and find TMEM120A as a ZIKV restriction factor. TMEM120A overexpression significantly inhibits ZIKV replication, while TMEM120A knockdown increases ZIKV infection in cell lines. Moreover, Tmem120a knockout in mice facilitates ZIKV infection in primary mouse embryonic fibroblasts (MEF) cells. Mechanistically, the antiviral activity of TMEM120A is dependent on STING, as TMEM120A interacts with STING, promotes the translocation of STING from the endoplasmic reticulum (ER) to ER-Golgi intermediate compartment (ERGIC) and enhances the phosphorylation of downstream TBK1 and IRF3, resulting in the expression of multiple antiviral cytokines and interferon-stimulated genes. In summary, our gain-of-function screening identifies TMEM120A as a key activator of the antiviral signaling of STING.

Zika Virus Infection in the Ovary Induces a Continuously Elevated Progesterone Level and Compromises Conception in Interferon Alpha/Beta Receptor-Deficient Mice.

Zika virus (ZIKV) belongs to mosquito-borne flaviviruses. Unlike other members in the family, ZIKV can be sexually transmitted, and the female genital tracts are susceptible to ZIKV. However, the impact of ZIKV infection on nonpregnant female reproductive health is not understood. In this study, we investigated the effects of ZIKV infection on the ovary by using nonpregnant female interferon α/ß receptor-deficient (Ifnar1-/-) mice. The results showed that the ovary supported ZIKV replication, and the granulosa and theca cells of antral follicles were susceptible. ZIKV replication in situ significantly reduced the numbers of antral follicles, aggravated follicular atresia, and disrupted folliculogenesis. Notably, ZIKV replication in the ovary caused disordered ovarian steroidogenesis manifested by decreased expression of key enzymes linked to sex hormone synthesis, including the cytochrome P450 17A1 (CYP17A1) and aromatase (CYP19A1). Further, we observed that ZIKV infection disrupted the estrous cycle and thus prolonged the time to conceive. More importantly, although ZIKV RNA could not be detected at 3 months postinfection, damaged ovarian structure and dysfunction were also observed. Taken together, our study demonstrates that ZIKV infection in nonpregnant female mice cause ovarian damage and dysfunction, even long after ZIKV clearance. These data provide important information to understand the effects of ZIKV infection in female reproductive tissues and basic evidence for further studies. IMPORTANCE Zika virus (ZIKV), a flavivirus, is primarily transmitted by mosquito bites. But it can also be transmitted vertically and sexually. Although ZIKV-associated Guillain-Barré syndrome and microcephaly have drawn great attention, there have been few studies on the potential effects of ZIKV on the genital tract of nonpregnant females. This study investigated the effects of ZIKV on the ovaries in mice. We found that ZIKV replicated in the ovary and the granulosa and theca cells of antral follicles were susceptible. ZIKV replication in situ significantly damaged ovarian structure and function and disrupted folliculogenesis. Notably, ZIKV infection further disrupted the estrous cycle and prolonged the time to conceive in mice by causing disordered ovarian steroidogenesis. These effects were observed in both the acute phase and the recovery phase after viral elimination. Overall, the new findings provide important additions to make out the potential adverse impacts of ZIKV on reproductive health in females.

The stressed life of a lipid in the Zika virus membrane.

Protein-lipid interactions modulate a plethora of physiopathologic processes and have been the subject of countless studies. However, these kinds of interactions in the context of viral envelopes have remained relatively unexplored, partially because the intrinsically small dimensions of the molecular systems escape to the current resolution of experimental techniques. However, coarse-grained and multiscale simulations may fill that niche, providing nearly atomistic resolution at an affordable computational price. Here we use multiscale simulations to characterize the lipid-protein interactions in the envelope of the Zika Virus, a prominent member of the Flavivirus genus. Comparisons between the viral envelope and simpler molecular systems indicate that the viral membrane is under extreme pressures and asymmetric forces. Furthermore, the dense net of protein-protein contacts established by the envelope proteins creates poorly solvated regions that destabilize the external leaflet leading to a decoupled dynamics between both membrane layers. These findings lead to the idea that the Flaviviral membrane may store a significant amount of elastic energy, playing an active role in the membrane fusion process.

The impact of Zika virus exposure on the placental proteomic profile.

Zika virus (ZIKV) infection has caused severe unexpected clinical outcomes in neonates and adults during the recent outbreak in Latin America, particularly in Brazil. Congenital malformations associated with ZIKV have been frequently reported; nevertheless, the mechanism of vertical transmission and the involvement of placental cells remains unclear. In this study, we applied quantitative proteomics analysis in a floating explant model of chorionic villi of human placental tissues incubated with ZIKV and with ZIKV pre-adsorbed with anti-ZIKV envelope protein. Proteomic data are available via ProteomeXchange with identifier PXD025764. Altered levels of proteins were involved in cell proliferation, apoptosis, inflammatory processes, and the integrin-cytoskeleton complex. Antibody-opsonized ZIKV particles differentially modulated the pattern of protein expression in placental cells; this phenomenon may play a pivotal role in determining the course of infection and the role of mixed infections. The expression of specific proteins was also evaluated by immunoperoxidase assays. These data fill gaps in our understanding of early events after ZIKV placental exposure and help identify infection control targets.

INMI1 Zika Virus NS4B Antagonizes the Interferon Signaling by Suppressing STAT1 Phosphorylation.

The evasion of the Interferon response has important implications in Zika virus (ZIKV) disease. Mutations in ZIKV viral protein NS4B, associated with modulation of the interferon (IFN) system, have been linked to increased pathogenicity in animal models. In this study, we unravel ZIKV NS4B as antagonist of the IFN signaling cascade. Firstly, we reported the genomic characterization of NS4B isolated from a strain of the 2016 outbreak, ZIKV Brazil/2016/INMI1, and we predicted its membrane topology. Secondly, we analyzed its phylogenetic correlation with other flaviviruses, finding a high similarity with dengue virus 2 (DEN2) strains; in particular, the highest conservation was found when NS4B was aligned with the IFN inhibitory domain of DEN2 NS4B. Hence, we asked whether ZIKV NS4B was also able to inhibit the IFN signaling cascade, as reported for DEN2 NS4B. Our results showed that ZIKV NS4B was able to strongly inhibit the IFN stimulated response element and the IFN-γ-activated site transcription, blocking IFN-I/-II responses. mRNA expression levels of the IFN stimulated genes ISG15 and OAS1 were also strongly reduced in presence of NS4B. We found that the viral protein was acting by suppressing the STAT1 phosphorylation and consequently blocking the nuclear transport of both STAT1 and STAT2.

Shiftless inhibits flavivirus replication in vitro and is neuroprotective in a mouse model of Zika virus pathogenesis.

Flaviviruses such as Zika virus and West Nile virus have the potential to cause severe neuropathology if they invade the central nervous system. The type I interferon response is well characterized as contributing to control of flavivirus-induced neuropathogenesis. However, the interferon-stimulated gene (ISG) effectors that confer these neuroprotective effects are less well studied. Here, we used an ISG expression screen to identify Shiftless (SHFL, C19orf66) as a potent inhibitor of diverse positive-stranded RNA viruses, including multiple members of the Flaviviridae (Zika, West Nile, dengue, yellow fever, and hepatitis C viruses). In cultured cells, SHFL functions as a viral RNA-binding protein that inhibits viral replication at a step after primary translation of the incoming genome. The murine ortholog, Shfl, is expressed constitutively in multiple tissues, including the central nervous system. In a mouse model of Zika virus infection, Shfl-/- knockout mice exhibit reduced survival, exacerbated neuropathological outcomes, and increased viral replication in the brain and spinal cord. These studies demonstrate that Shfl is an important antiviral effector that contributes to host protection from Zika virus infection and virus-induced neuropathological disease.

Murine Trophoblast Stem Cells and Their Differentiated Cells Attenuate Zika Virus In Vitro by Reducing Glycosylation of the Viral Envelope Protein.

Zika virus (ZIKV) infection during pregnancy can cause devastating fetal neuropathological abnormalities, including microcephaly. Most studies of ZIKV infection in pregnancy have focused on post-implantation stage embryos. Currently, we have limited knowledge about how a pre-implantation stage embryo deals with a viral infection. This study investigates ZIKV infection on mouse trophoblast stem cells (TSCs) and their in vitro differentiated TSCs (DTSCs), which resemble the cellular components of the trophectoderm layer of the blastocyst that later develops into the placenta. We demonstrate that TSCs and DTSCs are permissive to ZIKV infection; however, ZIKV propagated in TSCs and DTSCs exhibit substantially lower infectivity, as shown in vitro and in a mouse model compared to ZIKV that was generated in Vero cells or mouse embryonic fibroblasts (MEFs). We further show that the low infectivity of ZIKV propagated in TSCs and DTSCs is associated with a reduced level of glycosylation on the viral envelope (E) proteins, which are essential for ZIKV to establish initial attachment by binding to cell surface glycosaminoglycans (GAGs). The decreased level of glycosylation on ZIKV E is, at least, partially due to the low-level expression of a glycosylation-related gene, Hexa, in TSCs and DTSCs. Furthermore, this finding is not limited to ZIKV since similar observations have been made as to the chikungunya virus (CHIKV) and West Nile virus (WNV) propagated in TSCs and DTSCs. In conclusion, our results reveal a novel phenomenon suggesting that murine TSCs and their differentiated cells may have adapted a cellular glycosylation system that can limit viral infectivity by altering the glycosylation of viral envelope proteins, therefore serving as a unique, innate anti-viral mechanism in the pre-implantation stage embryo.

Tetraspanins: Host Factors in Viral Infections.

Tetraspanins are transmembrane glycoproteins that have been shown increasing interest as host factors in infectious diseases. In particular, they were implicated in the pathogenesis of both non-enveloped (human papillomavirus (HPV)) and enveloped (human immunodeficiency virus (HIV), Zika, influenza A virus, (IAV), and coronavirus) viruses through multiple stages of infection, from the initial cell membrane attachment to the syncytium formation and viral particle release. However, the mechanisms by which different tetraspanins mediate their effects vary. This review aimed to compare and contrast the role of tetraspanins in the life cycles of HPV, HIV, Zika, IAV, and coronavirus viruses, which cause the most significant health and economic burdens to society. In doing so, a better understanding of the relative contribution of tetraspanins in virus infection will allow for a more targeted approach in the treatment of these diseases.

Leu-to-Phe substitution at prM146 decreases the growth ability of Zika virus and partially reduces its pathogenicity in mice.

Zika virus (ZIKV) is a mosquito-borne flavivirus that causes febrile illness. The recent spread of ZIKV from Asia to the Americas via the Pacific region has revealed unprecedented features of ZIKV, including transplacental congenital infection causing microcephaly. Amino acid changes have been hypothesized to underlie the spread and novel features of American ZIKV strains; however, the relationship between genetic changes and the epidemic remains controversial. A comparison of the characteristics of a Southeast Asian strain (NIID123) and an American strain (PRVABC59) revealed that the latter had a higher replication ability in cultured cells and higher virulence in mice. In this study, we aimed to identify the genetic region of ZIKV responsible for these different characteristics using reverse genetics. A chimeric NIID123 strain in which the E protein was replaced with that of PRVABC59 showed a lower growth ability than the recombinant wild-type strain. Adaptation of the chimeric NIID123 to Vero cells induced a Phe-to-Leu amino acid substitution at position 146 of the prM protein; PRVABC59 also has Leu at this position. Leu at this position was found to be responsible for the viral replication ability and partially, for the pathogenicity in mouse testes.