Biology subjects

Coyne, C. B.

Publications and source records attributed to Coyne, C. B..

18 recordsLinked to original sources

bioRxiv2026

TLR3 Expression in Villus-Like Enterocytes Drives IFN-III Responses to Enteroviruses

Enteroviruses initiate infection at the intestinal epithelium but can spread systemically to cause severe disease. Although both MDA5 and TLR3 have been implicated in enterovirus sensing, the mechanisms by which the intestinal epithelium detects these viruses remain poorly defined. To address this, we infected human intestinal organoids (enteroids) with echovirus 11 (E11) and compared responses in models differentiated to mimic either crypt-like or villus-like epithelium. Villus-like enteroids produced significantly more type III interferons (IFN-{lambda}s) following E11 infection or treatment with the dsRNA mimetic poly I:C, and exhibited heightened responsiveness to IFN-{lambda} signaling. Single-cell RNA sequencing (scRNA-seq) of infected enteroids revealed that E11 broadly infected epithelial cell types, but IFN-{lambda} expression was largely restricted to mature enterocytes. Notably, enterocyte differentiation was also associated with upregulation of innate immune genes. Using CRISPR-Cas9 knockout enteroids, we found that TLR3 signaling was essential for intestinal IFN-{lambda} responses to E11 infection, whereas loss of MAVS, the adaptor for MDA5, had no effect. Together, these data support a model in which mature enterocytes serve as key sensors of enterovirus infection via TLR3, triggering a localized IFN-{lambda} response that may help restrict viral spread. ImportanceEnteroviruses are commonly circulating viruses that can cause a broad spectrum of disease, particularly in pediatric populations. Innate immune sensing in the intestinal epithelium likely plays a critical role in determining the outcome of enterovirus infections. Deficiencies in TLR3 signaling, IFN-{lambda} responses, or crypt-villus architecture may contribute to severe disease presentations. Our findings highlight the importance of TLR3-mediated sensing in mature enterocytes, which may also have broader implications for other intestinal viruses, as well as for inflammatory conditions like inflammatory bowel disease. A deeper understanding of how TLR3 sensing and IFN-{lambda} production are regulated in the intestine could inform new therapeutic strategies aimed at modulating mucosal sensitivity to viral nucleic acids and enhancing antiviral defense.

immunology↗

bioRxiv2025

Tissue-Resident Macrophage and Dendritic Cell Cooperation Drives Type I IFN Immunity to Enteroviruses in the Liver

Enteroviruses are major causes of neonatal morbidity and mortality, with echovirus infections commonly associated with severe disease, including acute liver failure. The human neonatal Fc receptor (hFcRn) is the primary receptor for echoviruses, and its expression is required for infection of the liver in mouse models. While type I interferons (IFNs) are known to protect against echovirus-induced disease, the specific innate immune cells responsible for initiating this antiviral signaling in the liver remain undefined. To dissect the relative contributions of type I and type III IFNs in protecting the liver during echovirus infection, we combined in vivo mouse models (expressing hFcRn and deficient in Ifnar1, Ifnlr1, or both) with single cell RNA sequencing (scRNA-seq). This approach enabled us to pinpoint the hepatic cell types targeted by echoviruses and to identify the specific cells producing IFNs in response. We found that hepatocytes and Kupffer cells were the most heavily infected cell types. In contrast, early and robust type I IFN responses were primarily driven by Kupffer cells and a subset of dendritic cells. To determine whether type I IFNs act directly on hepatocytes to mediate protection, we generated conditional knockout mice lacking Ifnar1 specifically in hepatocytes. These mice showed similar morbidity, mortality, and hepatic viral titers as whole-body Ifnar1-/- animals, indicating that hepatocytes depend on protective IFN signals produced by immune cells during echovirus infection. These findings uncover cell-type-specific mechanisms by which echoviruses subvert host immunity and show how dysregulated IFN responses drive liver pathology and neonatal mortality.

microbiology↗

bioRxiv2025

Cellular and Immune Adaptations at the Maternal-Fetal Interface in Bats

Bats maintain pregnancy despite extended gestation relative to other small mammals, high fetal investment, recurrent pathogen exposure, and the metabolic demands of flight. These physiological extremes likely drive unique adaptations in placental function and maternal-fetal immune regulation, yet the cellular and molecular basis of these adaptations remains largely unknown. Here, we mapped the cellular landscape of the Jamaican fruit bat (Artibeus jamaicensis) placenta using single-nucleus RNA sequencing (snRNA-seq), integrated with histological and immunohistochemical analyses. We identified diverse trophoblast, stromal, and immune populations at the maternal-fetal interface, including specialized macrophages expressing pregnancy-associated signaling molecules. Trajectory analysis revealed dynamic trophoblast differentiation through proliferative, invasive, and syncytial states. To model these processes in vitro, we derived trophoblast and decidual gland organoids from matched tissues, which recapitulated key in vivo cell types and lineage trajectories. Cross-species transcriptomic comparisons with human and mouse placentas uncovered bat-specific gene programs in trophoblasts, fibroblasts, and immune cells. Notably, bat trophoblast organoids exhibited attenuated antiviral signaling compared to their human counterparts, suggesting species-specific modulation of innate immunity at the maternal-fetal interface. These findings define cellular strategies that support pregnancy under extreme physiological conditions and establish a framework for investigating the evolution of placental adaptations across mammals. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/654282v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@12e7580org.highwire.dtl.DTLVardef@1245751org.highwire.dtl.DTLVardef@e0b9b0org.highwire.dtl.DTLVardef@1bf0694_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract:C_FLOATNO Using single-nucleus RNA sequencing (snRNA-seq) and placental organoids, we reveal unique trophoblast differentiation, immune cell specialization, and expanded stromal populations in Jamaican fruit bat placentas. Cross-species comparisons underscore bat-specific evolutionary adaptations critical for sustaining pregnancy amid extreme metabolic and immunological challenges. C_FIG SummaryPregnancy in bats occurs under a combination of physiological stressors rarely encountered in other mammals, including extended gestation relative to other small mammals, elevated metabolic load, temperature fluctuations associated with flight, and constant microbial exposure. To investigate how the placenta adapts to these challenges, we profiled Jamaican fruit bat (Artibeus jamaicensis) placenta using single-nucleus RNA sequencing and tissue-derived organoid models. This analysis revealed diverse trophoblast, stromal, and immune cell populations with bat-specific transcriptional programs. We identified dynamic trophoblast differentiation trajectories, fibroblasts with hybrid adventitial-neuronal signatures, and macrophages expressing pregnancy-associated molecules typically restricted to trophoblasts. Cross-species comparisons with human and mouse placentas uncovered both conserved cell states and lineage-specific adaptations, providing insight into the evolution of placental function and immune regulation across mammals. HighlightsO_LISingle-nucleus RNA-seq defines cell types and differentiation pathways in the bat placenta C_LIO_LIBat trophoblast and decidua gland organoids recapitulate in vivo lineage trajectories and cell signatures C_LIO_LIBat-specific transcriptional programs revealed across trophoblast, stromal, and immune lineages C_LIO_LIBat trophoblasts exhibit attenuated antiviral responses compared to human counterparts C_LI

developmental biology↗

bioRxiv2025

DUX4-stimulated genes define the antiviral response to herpesviruses in human trophoblasts

The placenta combats mother-to-fetus transmission of viruses through the antiviral activities of fetal-derived trophoblasts. Placental trophoblasts employ specialized antiviral strategies to protect against infection while preventing maternal immune rejection of the fetus. However, the full extent of how trophoblasts respond to viral infections is not well understood. To address this, we defined the transcriptional landscape of human trophoblast organoids infected with seven diverse teratogenic viruses. We found that herpesviruses, including HSV-1, HSV-2, and HCMV, did not trigger a typical interferon (IFN) response. Instead, they activated the expression of DUX4 and its downstream target genes, collectively known as DUX4-stimulated genes (DSGs). This program was highly specific for trophoblasts and was associated with cells containing low viral transcripts following HSV-1 infection, suggesting an antiviral activity. Screening of highly expressed DSGs revealed that many of them exhibited anti-herpesvirus activity, indicating the existence of an alternative antiviral pathway similar to the IFN-stimulated gene response. These findings identify DUX4 as a master regulator of a coordinated antiviral program in trophoblasts, specifically targeting a prominent family of teratogenic viruses. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/634317v2_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@57206dorg.highwire.dtl.DTLVardef@11f100org.highwire.dtl.DTLVardef@1e56846org.highwire.dtl.DTLVardef@20e95c_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

Tissue Context Drives Regional Differences in Trophoblast Differentiation in Fetal Membranes and Chorionic Villi

Trophoblasts within the fetal membrane primarily serve as protective barriers, shielding the developing fetus from the external environment, while those in chorionic villi facilitate interactions between the maternal and fetal compartments. Although these distinct trophoblast populations perform specialized roles based on their placental location, the mechanisms governing their development and differentiation remain largely unknown. In this study, we derived trophoblast organoids from both the smooth chorion of fetal membranes and chorionic villi from matched human placentas to create parallel in vitro models of these distinct trophoblast populations. Using comparative transcriptional profiling with both bulk and single-cell RNA sequencing, we identified subtle transcriptional variations, while overall gene expression patterns and cellular composition remained highly conserved. Comparative single-cell RNA sequencing and differentiation trajectory analysis of organoids derived from chorion and villous tissues, along with their respective tissue counterparts, revealed region-specific gene expression patterns that were only partially conserved in organoids. The similarity between these in vitro models suggests that regional differences in trophoblast expression observed in vivo are driven by environmental and regional cues. These findings highlight the critical role of local environmental factors in shaping trophoblast function and offer insights into the conserved mechanisms that support placental integrity and fetal development, while emphasizing the influence of region-specific cues in vivo.

cell biology↗

bioRxiv2024

Toxoplasma gondii infection misdirects placental trophoblast lineage specification

Pregnancy is a critical point of vulnerability to infection and other insults that could compromise proper fetal development. The placenta acts as a protective and nutrient-permeable barrier to most infectious agents, but a few are capable of bypassing its defenses. Remarkably little is known about how exposure to these select pathogens might impact ongoing placental development. Here we demonstrate that Toxoplasma gondii entirely misdirects the developmental program of trophoblast stem cells. Infection of progenitor cytotrophoblasts prevents fusion and differentiation to infection-resistant syncytiotrophoblast. Rather, T. gondii elicits a unique transcriptional identity that polarizes cytotrophoblasts to the infection-permissive extravillous trophoblast fate. Strong evidence of developmental disruption is found in multiple orthogonal models, including trophoblast stem cells, trophoblast organoids, and chorionic villi. Manipulation of cell fate by the parasite is most dramatic in trophoblast organoids, where we see robust outgrowth of HLA-G(+) extravillous trophoblasts. Collectively, these data show that Toxoplasma antagonizes differentiation of an infection-resistant cell type by inducing formation of an infection-permissive cell type, therefore potentiating its own transmission to the fetus.

developmental biology↗

bioRxiv2024

Comparative analysis of the syncytiotrophoblast in placenta tissue and trophoblast organoids using snRNA sequencing

The outer surface of chorionic villi in the human placenta consists of a single multinucleated cell called the syncytiotrophoblast (STB). The unique cellular ultrastructure of the STB presents challenges in deciphering its gene expression signature at the single-cell level, as the STB contains billions of nuclei in a single cell. There are many gaps in understanding the molecular mechanisms and developmental trajectories involved in STB formation and differentiation. To identify the underlying control of the STB, we performed comparative single nucleus (SN) and single cell (SC) RNA sequencing on placental tissue and tissue-derived trophoblast organoids (TOs). We found that SN RNA sequencing was essential to capture the STB population from both tissue and TOs. Differential gene expression and pseudotime analysis of TO-derived STB identified three distinct nuclear subtypes reminiscent of those recently identified in vivo. These included a juvenile nuclear population that exhibited both CTB and STB marker expression, a population enriched in genes involved in oxygen sensing, and finally a subtype enriched in transport and GTPase signaling molecules. Notably, suspension culture conditions of TOs that restore the native orientation of the STB (STBout) showed elevated expression of canonical STB markers and pregnancy hormones, along with a greater proportion of the STB nucleus subtype specializing in transport and GTPase signaling, compared to those cultivated with an inverted STB polarity (STBin). Gene regulatory analysis identified novel markers of STB differentiation conserved in tissue and TOs, including the chromatin remodeler RYBP, that exhibited STB-specific RNA and protein expression. CRISPR/Cas9 knockout of RYBP in STBin TOs did not impact cell-cell fusion; however, bulk RNA sequencing revealed downregulation of the pregnancy hormone CSH1 and upregulation of multiple genes associated with the oxygen-sensing STB nuclear subtype. Finally, we compared STB gene expression signatures amongst first trimester tissue, full-term tissue, and TOs, identifying many commonalities but also notable variability across each sample type. This indicates that STB gene expression is responsive to its environmental context. Our findings emphasize the utility of TOs to accurately model STB differentiation and the distinct nuclear subtypes observed in vivo, offering a versatile platform for unraveling the molecular mechanisms governing STB functions in placental biology and disease.

developmental biology↗

bioRxiv2023

Human trophoblast stem cells can be used to model placental susceptibility to Toxoplasma gondii and highlight the critical importance of the trophoblast cell surface in pathogen resistance

The placenta is a critical barrier against viral, bacterial, and eukaryotic pathogens. For most teratogenic pathogens, the precise molecular mechanisms of placental resistance are still being unraveled. Given the importance to understand these mechanisms and challenges in replicating trophoblast-pathogen interactions using in vitro models, we tested an existing stem-cell derived model of trophoblast development for its relevance to infection with Toxoplasma gondii. We grew human trophoblast stem cells (TSCT) under conditions leading to either syncytiotrophoblast (TSSYN) or cytotrophoblast (TSCYT) and infected them with T. gondii. We evaluated T. gondii proliferation and invasion, cell ultrastructure, as well as for transcriptome changes after infection. TSSYNs cells showed similar ultrastructure compared to primary cells and villous explants when analyzed by TEM and SEM, a resistance to T. gondii adhesion could be visualized on the SEM level. Furthermore, TSSYNs were highly refractory to parasite adhesion and replication, while TSCYT were not. RNA-seq data on mock-treated and infected cells identified differences between cell types as well as how they responded to T. gondii infection. We also evaluated if TSSC-derived SYNs and CYTs had distinct resistance profiles to another vertically transmitted facultative intracellular pathogen, Listeria monocytogenes. We demonstrate that TSSYNs are highly resistant to L. monocytogenes, while TSCYTs are not. Like T. gondii, TSSYN resistance to L. monocytogenes was at the level of bacterial adhesion. Altogether, our data indicate that stem-cell derived trophoblasts recapitulate resistance profiles of primary cells to T. gondii and highlight the critical importance of the placental surface in cell-autonomous resistance to teratogens.

microbiology↗

bioRxiv2022

An in vivo model of echovirus-induced meningitis in neonates

Echoviruses are amongst the most common causes of aseptic meningitis worldwide, which can cause long-term sequelae and death, particularly in neonates. However, the mechanisms by which these viruses induce meningeal inflammation is poorly understood, owing at least in part to the lack of in vivo models that recapitulate this aspect of echovirus pathogenesis. Here, we developed an in vivo neonatal mouse model that recapitulates key aspects of echovirus-induced meningitis. We found that expression of the human homologue of the neonatal Fc receptor (FcRn), the primary echovirus receptor, in neonatal mice was not sufficient for infection of the brain. However, ablation of type I, but not III, IFN signaling in mice expressing human FcRn permitted high levels of echovirus replication in the brain, with corresponding clinical symptoms including delayed motor skills and hind limb weakness. We also defined the immunological response of the brain to echovirus infections and identified key cytokines induced by this infection. Lastly, we found that echoviruses robustly replicate in the leptomeninges, where they induce profound inflammation and cell death. Together, this work establishes an in vivo model of aseptic meningitis associated with echovirus infections and defines the specificity of echoviral infections within the meninges. Significance StatementEchoviruses are amongst the most common causes of aseptic meningitis worldwide, which can cause long-term sequelae or even death. The mechanisms by which echoviruses infect the brain are poorly understood, largely owing to the lack of robust in vivo models that recapitulate this aspect of echovirus pathogenesis. Here, we establish a neonatal mouse model of echovirus-induced aseptic meningitis and show that expression of the human homologue of the neonatal Fc receptor (FcRn), the primary receptor for echoviruses, and ablation of type I interferon (IFN) signaling are required to recapitulate echovirus-induced meningitis and clinical disease. These findings provide key insights into the host factors that control echovirus-induced meningitis and a model that could be used to test anti-echovirus therapeutics.

microbiology↗

bioRxiv2022

Enterovirus replication and dissemination are differentially controlled by type I and III interferons in the GI tract

Enteroviruses are amongst the most common viral infectious agents of humans and cause a broad spectrum of mild-to-severe illness. Enteroviruses are primarily transmitted by the fecal-oral route, but the events associated with their intestinal replication in vivo are poorly defined. Here, we developed a neonatal mouse model of enterovirus infection by the enteral route using echovirus 5 and used this model to define the differential roles of type I and III interferons (IFNs) in enterovirus replication in the intestinal epithelium and subsequent dissemination to secondary tissues. We show that human FcRn, the primary receptor for echoviruses, is essential for intestinal infection by the enteral route and that type I IFNs control dissemination to secondary sites, including the liver. In contrast, type III IFNs limit enterovirus infection in the intestinal epithelium and mice lacking this pathway exhibit persistent epithelial replication. Finally, we show that echovirus infection in the small intestine is cell-type specific and occurs exclusively in enterocytes. These studies define the type-specific roles of IFNs in enterovirus infection of the GI tract and the cellular tropism of echovirus intestinal replication.

microbiology↗

bioRxiv2021

Innate immune signaling in trophoblast and decidua organoids defines differential antiviral defenses at the maternal-fetal interface

Infections at the maternal-fetal interface can directly harm the fetus and induce complications that adversely impact pregnancy outcomes. Innate immune signaling by both fetal-derived placental trophoblasts and the maternal decidua must provide antimicrobial defenses at this critical interface without compromising its integrity. Here, we developed matched trophoblast and decidua organoids from human placentas to define the relative contributions of these cells to antiviral defenses at the maternal-fetal interface. We demonstrate that trophoblast and decidua organoids basally secrete distinct immunomodulatory factors, including the constitutive release of the antiviral type III interferon IFN- {lambda}2 from trophoblast organoids, and differentially respond to viral infections through the induction of organoid-specific factors. Lastly, we define the differential susceptibility of trophoblast and decidua organoids to human cytomegalovirus (HCMV) and the transcriptional and immunological responses of these organoids to HCMV infection. Our findings establish matched trophoblast and decidua organoids as ex vivo models to study vertically transmitted infections and highlight differences in innate immune signaling by fetal-derived trophoblasts and the maternal decidua.

immunology↗

bioRxiv2020

Toxoplasma gondii GRA28 is required for specific induction of the regulatory chemokine CCL22 in human and mouse cells.

Toxoplasma gondii is an intracellular protozoan pathogen of humans that can cross the placenta and result in adverse pregnancy outcomes and long-term birth defects. The mechanism used by T. gondii to cross the placenta are unknown but complex interactions with the host immune response are likely to play a role in dictating infection outcomes during pregnancy. Prior work showed that T. gondii infection dramatically and specifically increases the secretion of the immunomodulatory chemokine CCL22 in human placental cells during infection.. Given the important role of this chemokine during pregnancy, we hypothesized that CCL22 induction was driven by a specific T. gondii-secreted effector. Using a combination of bioinformatics and molecular genetics, we have now identified T. gondii GRA28 as the gene product required for CCL22 induction. GRA28 is secreted into the host cell where it localizes to the nucleus, and deletion of this gene results in reduced CCL22 placental cells as well as a human monocyte cell line. The impact of GRA28 on CCL22 production is also conserved in mouse immune and placental cells both in vitro and in vivo. Moreover, parasites lacking GRA28 are impaired in their ability to disseminate throughout the animal, suggesting a link between CCL22 induction and the ability of the parasite to cause disease. Overall these data demonstrate a clear function for GRA28 in altering the immunomodulatory landscape during infection of both placental and peripheral immune cells, and show a clear impact of this immunomodulation on infection outcome. AUTHOR SUMMARYToxoplasma gondii is a globally ubiquitous pathogen that can cause severe disease in HIV/AIDS patients and can also cross the placenta and infect the developing fetus. We have found that placental and immune cells infected with T. gondii secrete significant amounts of a chemokine (called "CCL22") that is critical for immune tolerance during pregnancy. In order to better understand whether this is a response by the host or a process that is driven by the parasite, we have identified a T. gondii gene that is absolutely required to induce CCL22 production in human cells, indicating that CCL22 production is a process driven almost entirely by the parasite rather than the host. Consistent with its role in immune tolerance, we also found that T. gondii parasites lacking this gene are less able to proliferate and disseminate throughout the host. Taken together these data illustrate a direct relationship between CCL22 levels in the infected host and a key parasite effector, and provide an interesting example of how T. gondii can directly modulate host signaling pathways in order to facilitate its growth and dissemination.

microbiology↗

bioRxiv2020

Antiviral activity of a human placental protein of retroviral origin

Endogenous retroviruses are abundant components of mammalian genomes descended from ancient germline infections. In several mammals, the envelope proteins encoded by these elements protect against exogenous viruses, but this activity has not been documented in human. We report that our genome harbors a large pool of envelope-derived sequences with the potential to restrict retroviral infection. To further test this, we characterize in detail the envelope-derived protein, Suppressyn. We found that Suppressyn is expressed in preimplantation embryos and developing placenta using its ancestral retroviral promoter. Restriction assays in cell culture show that Suppressyn, and its hominoid orthologs, can restrict infection by extant mammalian type D retroviruses. Our data support a generalizable model of retroviral envelope cooption for host immunity and genome defense. SummaryWe found that the human genome expresses a vast pool of envelope sequences of retroviral origin and provide proof of principle that such proteins can restrict zoonotic viruses.

molecular biology↗

bioRxiv2020

BPIFB3 interacts with ARFGAP1 and TMED9 to regulate non-canonical autophagy and RNA virus infection

Autophagy is a degradative cellular pathway that targets cytoplasmic contents and organelles for turnover by the lysosome. Various autophagy pathways play key roles in the clearance of viral infections, and many families of viruses have developed unique methods for avoiding degradation. Some positive stranded RNA viruses, such as enteroviruses and flaviviruses, usurp the autophagic pathway to promote their own replication. We previously identified the endoplasmic reticulum-localized protein BPIFB3 as an important regulator of non-canonical autophagy that uniquely impacts the replication of enteroviruses and flaviviruses. Here, we find that many components of the canonical autophagy machinery are not required for BPIFB3-regulated autophagy and identify the host factors that facilitate its role in the replication of enteroviruses and flaviviruses. Using proximity-dependent biotinylation (BioID) followed by mass spectrometry, we identify ARFGAP1 and TMED9 as two cellular components that interact with BPIFB3 to regulate autophagy and viral replication. Importantly, our data demonstrate that non-canonical autophagy in mammalian cells can be controlled outside of the traditional pathway regulators and define the role of two proteins in BPIFB3-mediated non-canonical autophagy. Summary StatementBPIFB3 is a regulator of a non-canonical cellular autophagy pathway that impacts the replication of enteroviruses and flaviviruses. Here we define ARFGAP1 and TMED9 as essential components of this pathway.

cell biology↗

bioRxiv2018

Rift Valley fever virus induces fetal demise through direct placental infection

Rift Valley fever virus (RVFV) infections in pregnant livestock are associated with high rates of fetal demise and have been linked to miscarriage in pregnant women. To address how acute RVFV infection during pregnancy causes detrimental effects on the fetus, we developed an immunocompetent pregnant rodent model of RVFV infection. We found that pregnant rats were more susceptible to RVFV-induced death than their non-pregnant counterparts and that RVFV infection resulted in intrauterine fetal death and severe congenital abnormalities, even in pups from infected asymptomatic pregnant rats. Virus distribution in infected dams was widespread, with a previously unrecognized preference for infection, replication, and tissue damage in the placenta. In human mid-gestation placental tissue, RVFV directly infected placental chorionic villi, with replication detected in the outermost syncytial layer. Our work identifies direct placental infection by RVFV as a mechanism for vertical transmission and points to the teratogenic potential of this virus in humans. This is the first time vertical transmission of RVFV has been shown in species other than livestock. This study highlights the potential impact of a future epidemic of this emerging mosquito-borne virus.

microbiology↗

bioRxiv2018

Type III interferon signaling restricts Enterovirus 71 infection of goblet cells

Recent worldwide outbreaks of enterovirus (EV71) have caused major epidemics of hand, foot, and mouth disease (HFMD) with severe neurological complications, including acute flaccid paralysis. EV71 is transmitted by the enteral route, but very little is known about the mechanisms it utilizes to cross the human gastrointestinal (GI) tract. Using primary human intestinal epithelial monolayers, we show that EV71 infects the GI epithelium from the apical surface, where it preferentially infects goblet cells. Unlike echovirus 11 (E11), an enterovirus that infects enterocytes, EV71 infection did not alter epithelial barrier function, but did reduce the expression of a goblet cell-derived mucin, suggesting it alters goblet cell function. We also show that the intestinal epithelium responds to EV71 infection through the selective induction of type III IFNs, which potently restrict EV71 replication. Collectively, these findings define the early events associated with EV71 infections of the human intestinal epithelium and show that host IFN signaling controls replication in an IFN-specific manner.

microbiology↗

bioRxiv2018

BPIFB3 facilitates flavivirus infection by controlling RETREG1-dependent reticulophagy

The flavivirus genus, which includes dengue virus (DENV) and Zika virus (ZIKV), are significant human pathogens and the prevalence of infected vectors continues to geographically expand. Both DENV and ZIKV rely on expansion of the endoplasmic reticulum (ER) and the induction of autophagy to establish a productive viral infection. However, little is known regarding the interplay between the requirements for autophagy initiation during infection and the mechanisms used by these viruses to avoid clearance through the autophagic pathway. We recently showed that DENV and ZIKV inhibit reticulophagy (specific degradation of the ER through autophagy) by cleaving reticulophagy regulator 1 (RETREG1), an autophagy receptor responsible for targeted ER sheet degradation. These data suggest that DENV and ZIKV require specific autophagic pathways for their replication, while other autophagic pathways are antiviral. We previously identified BPI Fold Containing Family B Member 3 (BPIFB3) as a regulator of autophagy that negatively controls enterovirus replication. Here, we show that in contrast to enteroviruses, BPIFB3 functions as a positive regulator of DENV and ZIKV infection and that its RNAi-mediated silencing drastically inhibits the formation of viral replication organelles. We show that BPIFB3 depletion enhances ER fragmentation, while its overexpression protects against autophagy-induced ER degradation, demonstrating that BPIFB3 serves as a specific regulator of ER turnover. We further show that the antiviral effects of BPIFB3 depletion on flavivirus infection are reversed in RETREG1-depleted cells, and that BPIFB3 associates with RETREG1 within the ER, suggesting that BPIFB3 regulates a RETREG1-specific reticulophagy pathway. Collectively, these studies identify BPIFB3 as a regulator of the reticulophagy pathway and define the requirements for a novel host regulator of flavivirus infection.\n\nAuthor SummaryFlaviviruses and other arthropod transmitted viruses represent a widespread global health problem with limited treatment options currently available. Thus, greater knowledge of the host factors required for replication and transmission is needed to provide a better understanding of the cellular requirements for infection. Here, we show that the endoplasmic reticulum (ER) localized protein, BPIFB3 is required to facilitate flavivirus infection. Depletion of BPIFB3 in cells inhibits dengue virus and Zika virus infection prior to replication of the viral genome. Mechanistically, we show that BPIFB3 inhibits ER degradation in an autophagy-specific manner and that loss of BPIFB3 decreases the availability of ER membranes needed for flavivirus replication. We further show that BPIFB3 specifically regulates the RETREG1 pathway, but not other pathways of ER turnover. Together, our data define a previously uncharacterized method of regulating ER degradation and show that BPIFB3 is an essential host factor for a productive flavivirus infection.

microbiology↗

bioRxiv2017

Human placental syncytiotrophoblasts restrict Toxoplasma gondii vertical transmission at two distinct stages and induce CCL22 in response to infection

Toxoplasma gondii is a major source of congenital disease worldwide, but the cellular and molecular factors associated with its vertical transmission are largely unknown. In humans, the placenta forms the key interface between the maternal and fetal compartments and forms the primary barrier that restricts the hematogenous spread of microorganisms. Here, we utilized primary human trophoblast (PHT) cells isolated from full-term placentas and human mid-gestation chorionic villous explants to determine the mechanisms by which human trophoblasts restrict and respond to T. gondii infection. We show that placental syncytiotrophoblasts, multinucleated cells that are in direct contact with maternal blood, restrict T. gondii infection at distinct stages of the parasite lytic cycle--at the time of attachment and also during intracellular replication. Utilizing comparative RNAseq transcriptional profiling, we also show that human placental trophoblasts at both mid- and late-stages of gestation induce the chemokine CCL22 in response to T. gondii infection, which relies on the secretion of parasite effector(s). Collectively, our findings provide new insights into the mechanisms by which the human placenta restricts the vertical transmission of T. gondii at early and late stages of human pregnancy, and demonstrate the existence of at least two interferon-independent pathways that restrict T. gondii access to the fetal compartment.\n\nSignificance statementToxoplasma gondii is a major source of congenital disease worldwide and must breach the placental barrier to be transmitted from maternal blood to the developing fetus. The events associated with the vertical transmission of T. gondii are largely unknown. Here, we show that primary human syncytiotrophoblasts, the fetal-derived cells that comprise the primary placental barrier, restrict T. gondii infection at two distinct stages of the parasite life cycle and respond to infection through the induction of the chemokine CCL22. Collectively, our findings provide important insights into the mechanisms by which human syncytiotrophoblasts restrict T. gondii infection at early and late stages of human pregnancy and identify the placental-enriched signaling pathways induced in response to infection.

microbiology↗