IL-6-mediated endothelial injury impairs antiviral humoral immunity after bone marrow transplantation.

Endothelial function and integrity are compromised after allogeneic bone marrow transplantation (BMT), but how this affects immune responses broadly remains unknown. Using a preclinical model of CMV reactivation after BMT, we found compromised antiviral humoral responses induced by IL-6 signaling. IL-6 signaling in T cells maintained Th1 cells, resulting in sustained IFN-γ secretion, which promoted endothelial cell (EC) injury, loss of the neonatal Fc receptor (FcRn) responsible for IgG recycling, and rapid IgG loss. T cell-specific deletion of IL-6R led to persistence of recipient-derived, CMV-specific IgG and inhibited CMV reactivation. Deletion of IFN-γ in donor T cells also eliminated EC injury and FcRn loss. In a phase III clinical trial, blockade of IL-6R with tocilizumab promoted CMV-specific IgG persistence and significantly attenuated early HCMV reactivation. In sum, IL-6 invoked IFN-γ-dependent EC injury and consequent IgG loss, leading to CMV reactivation. Hence, cytokine inhibition represents a logical strategy to prevent endothelial injury, thereby preserving humoral immunity after immunotherapy.

Human cytomegalovirus (CMV) dysregulates neurodevelopmental pathways in cerebral organoids.

Human cytomegalovirus (CMV) infection is the leading non-genetic aetiology of congenital malformation in developed countries, causing significant fetal neurological injury. This study investigated potential CMV pathogenetic mechanisms of fetal neural malformation using in vitro human cerebral organoids. Cerebral organoids were permissive to CMV replication, and infection dysregulated cellular pluripotency and differentiation pathways. Aberrant expression of dual-specificity tyrosine phosphorylation-regulated kinases (DYRK), sonic hedgehog (SHH), pluripotency, neurodegeneration, axon guidance, hippo signalling and dopaminergic synapse pathways were observed in CMV-infected organoids using immunofluorescence and RNA-sequencing. Infection with CMV resulted in dysregulation of 236 Autism Spectrum Disorder (ASD)-related genes (p = 1.57E-05) and pathways. This notable observation suggests potential links between congenital CMV infection and ASD. Using DisGeNET databases, 103 diseases related to neural malformation or mental disorders were enriched in CMV-infected organoids. Cytomegalovirus infection-related dysregulation of key cerebral cellular pathways potentially provides important, modifiable pathogenetic mechanisms for congenital CMV-induced neural malformation and ASD.

CMV-encoded GPCRs in infection, disease, and pathogenesis.

G protein coupled receptors (GPCRs) are seven-transmembrane domain proteins that modulate cellular processes in response to external stimuli. These receptors represent the largest family of membrane proteins, and in mammals, their signaling regulates important physiological functions, such as vision, taste, and olfaction. Many organisms, including yeast, slime molds, and viruses encode GPCRs. Cytomegaloviruses (CMVs) are large, betaherpesviruses, that encode viral GPCRs (vGPCRs). Human CMV (HCMV) encodes four vGPCRs, including UL33, UL78, US27, and US28. Each of these vGPCRs, as well as their rodent and primate orthologues, have been investigated for their contributions to viral infection and disease. Herein, we discuss how the CMV vGPCRs function during lytic and latent infection, as well as our understanding of how they impact viral pathogenesis.

AAV2 vector optimization for retinal ganglion cell-targeted delivery of therapeutic genes.

Recombinant adeno-associated virus (AAV)-2 has significant potential as a delivery vehicle of therapeutic genes to retinal ganglion cells (RGCs), which are key interventional targets in optic neuropathies. Here we show that when injected intravitreally, AAV2 engineered with a reporter gene driven by cytomegalovirus (CMV) enhancer and chicken ß-actin (CBA) promoters, displays ubiquitous and high RGC expression, similar to its synthetic derivative AAV8BP2. A novel AAV2 vector combining the promoter of the human RGC-selective γ-synuclein (hSNCG) gene and woodchuck hepatitis post-transcriptional regulatory element (WPRE) inserted upstream and downstream of a reporter gene, respectively, induces widespread transduction and strong transgene expression in RGCs. High transduction efficiency and selectivity to RGCs is further achieved by incorporating in the vector backbone a leading CMV enhancer and an SV40 intron at the 5' and 3' ends, respectively, of the reporter gene. As a delivery vehicle of hSIRT1, a 2.2-kb therapeutic gene with anti-apoptotic, anti-inflammatory and anti-oxidative stress properties, this recombinant vector displayed improved transduction efficiency, a strong, widespread and selective RGC expression of hSIRT1, and increased RGC survival following optic nerve crush. Thus, AAV2 vector carrying hSNCG promoter with additional regulatory sequences may offer strong potential for enhanced effects of candidate gene therapies targeting RGCs.

Cucumber mosaic virus impairs the physiological homeostasis of Panax notoginseng and induces saponin-mediated resistance.

As an important medicinal plant, Panax notoginseng often suffers from various abiotic and biotic stresses during its growth, such as drought, heavy metals, fungi, bacteria and viruses. In this study, the symptom and physiological parameters of cucumber mosaic virus (CMV)-infected P. notoginseng were analyzed and the RNA-seq was performed. The results showed that CMV infection affected the photosynthesis of P. notoginseng, caused serious oxidative damage to P. notoginseng and increased the activity of several antioxidant enzymes. Results of transcriptome analysis and corresponding verification showed that CMV infection changed the expression of genes related to plant defense and promoted the synthesis of P. notoginseng saponins to a certain extent, which may be defensive ways of P. notoginseng against CMV infection. Furthermore, pretreatment plants with saponins reduced the accumulation of CMV. Thus, our results provide new insights into the role of saponins in P. notoginseng response to virus infection.

Cytomegalovirus-induced inactivation of TSC2 disrupts the coupling of fatty acid biosynthesis to glucose availability resulting in a vulnerability to glucose starvation.

IMPORTANCE: Viruses modulate host cell metabolism to support the mass production of viral progeny. For human cytomegalovirus, we find that the viral UL38 protein is critical for driving these pro-viral metabolic changes. However, our results indicate that these changes come at a cost, as UL38 induces an anabolic rigidity that leads to a metabolic vulnerability. We find that UL38 decouples the link between glucose availability and fatty acid biosynthetic activity. Normal cells respond to glucose limitation by down-regulating fatty acid biosynthesis. Expression of UL38 results in the inability to modulate fatty acid biosynthesis in response to glucose limitation, which results in cell death. We find this vulnerability in the context of viral infection, but this linkage between fatty acid biosynthesis, glucose availability, and cell death could have broader implications in other contexts or pathologies that rely on glycolytic remodeling, for example, oncogenesis.

rAAV-compatible human mini promoters enhance transgene expression in rat retinal ganglion cells.

Recombinant adeno-associated viral vectors (rAAV) are the safest and most effective gene delivery platform to drive the treatment of many inherited eye disorders in well-characterized animal models. The use in rAAV of ubiquitous promoters derived from viral sequences such as CMV/CBA (chicken ß-actin promoter with cytomegalovirus enhancer) can lead to unwanted side effects such as pro-inflammatory immune responses and retinal cytotoxicity, thus reducing therapy efficacy. Thus, an advance in gene therapy is the availability of small promoters, that potentiate and direct gene expression to the cell type of interest, with higher safety and efficacy. In this study, we used six human mini-promoters packaged in rAAV2 quadruple mutant (Y-F) to test for transduction of the rat retina after intravitreal injection. After four weeks, immunohistochemical analysis detected GFP-labeled cells in the ganglion cell layer (GCL) for all constructs tested. Among them, Ple25sh1, Ple25sh2 and Ple53 promoted a widespread reporter-transgene expression in the GCL, with an increased number of GFP-expressing retinal ganglion cells when compared with the CMV/CBA vector. Moreover, Ple53 provided the strongest levels of GFP fluorescence in both cell soma and axons of retinal ganglion cells (RGCs) without any detectable adverse effects in retina function. Remarkably, a nearly 50-fold reduction in the number of intravitreally injected vector particles containing Ple53 promoter, still attained levels of transgene expression similar to CMV/CBA. Thus, the tested MiniPs show great potential for protocols of retinal gene therapy in therapeutic applications for retinal degenerations, especially those involving RGC-related disorders such as glaucoma.

Rat cytomegalovirus efficiently replicates in dendritic cells and induces changes in their transcriptional profile.

Dendritic cells (DC) play a crucial role in generating and maintaining antiviral immunity. While DC are implicated in the antiviral defense by inducing T cell responses, they can also become infected by Cytomegalovirus (CMV). CMV is not only highly species-specific but also specialized in evading immune protection, and this specialization is in part due to characteristic genes encoded by a given virus. Here, we investigated whether rat CMV can infect XCR1+ DC and if infection of DC alters expression of cell surface markers and migration behavior. We demonstrate that wild-type RCMV and a mutant virus lacking the γ-chemokine ligand xcl1 (Δvxcl1 RCMV) infect splenic rat DC ex vivo and identify viral assembly compartments. Replication-competent RCMV reduced XCR1 and MHCII surface expression. Further, gene expression of infected DC was analyzed by bulk RNA-sequencing (RNA-Seq). RCMV infection reverted a state of DC activation that was induced by DC cultivation. On the functional level, we observed impaired chemotactic activity of infected XCR1+ DC compared to mock-treated cells. We therefore speculate that as a result of RCMV infection, DC exhibit diminished XCR1 expression and are thereby blocked from the lymphocyte crosstalk.

Significance of HLA-E and its two NKG2 receptors in development of complications after allogeneic transplantation of hematopoietic stem cells.

Transplantation of hematopoietic stem cells (HSCT) is a procedure commonly used in treatment of various haematological disorders which is associated with significantly improved survival rates. However, one of its drawbacks is the possibility of development of post-transplant complications, including acute and chronic graft-versus-host disease (GvHD) or CMV infection. Various studies suggested that NK cells and their receptors may affect the transplant outcome. In the present study, patients and donors were found to significantly differ in the distribution of the NKG2A rs7301582 genetic variants - recipients carried the C allele more often than their donors (0.975 vs 0.865, p<0.0001). Increased soluble HLA-E (sHLA-E) levels detected in recipients' serum 30 days after transplantation seemed to play a prognostic and protective role. It was observed that recipients with higher sHLA-E levels were less prone to chronic GvHD (11.65 vs 6.33 pg/mL, p=0.033) or more severe acute GvHD grades II-IV (11.07 vs 8.04 pg/mL, p=0.081). Our results also showed an unfavourable role of HLA-E donor-recipient genetic incompatibility in CMV infection development after transplantation (OR=5.92, p=0.014). Frequencies of NK cells (both CD56dim and CD56bright) expressing NKG2C were elevated in recipients who developed CMV, especially 30 and 90 days post-transplantation (p<0.03). Percentages of NKG2C+ NK cells lacking NKG2A expression were also increased in these patients. Moreover, recipients carrying a NKG2C deletion characterized with decreased frequency of NKG2C+ NK cells (p<0.05). Our study confirms the importance of NK cells in the development of post-transplant complications and highlights the effect of HLA-E and NKG2C genetic variants, sHLA-E serum concentration, as well as NKG2C surface expression on transplant outcome.

Neutralizing antibodies with neurotropic factor treatment maintain neurodevelopmental gene expression upon exposure to human cytomegalovirus.

IMPORTANCE: Human cytomegalovirus (HCMV) infection is the leading cause of non-heritable birth defects worldwide. HCMV readily infects the early progenitor cell population of the developing brain, and we have found that infection leads to significantly downregulated expression of key neurodevelopmental transcripts. Currently, there are no approved therapies to prevent or mitigate the effects of congenital HCMV infection. Therefore, we used human-induced pluripotent stem cell-derived organoids and neural progenitor cells to elucidate the glycoproteins and receptors used in the viral entry process and whether antibody neutralization was sufficient to block viral entry and prevent disruption of neurodevelopmental gene expression. We found that blocking viral entry alone was insufficient to maintain the expression of key neurodevelopmental genes, but neutralization combined with neurotrophic factor treatment provided robust protection. Together, these studies offer novel insight into mechanisms of HCMV infection in neural tissues, which may aid future therapeutic development.

Cutting Edge: STAT4 Promotes Bhlhe40 Induction to Drive Protective IFN-γ from NK Cells during Viral Infection.

NK cells represent a cellular component of the mammalian innate immune system, and they mount rapid responses against viral infection, including the secretion of the potent antiviral effector cytokine IFN-γ. Following mouse CMV infection, Bhlhe40 was the most highly induced transcription factor in NK cells among the basic helix-loop-helix family. Bhlhe40 upregulation in NK cells depended upon IL-12 and IL-18 signals, with the promoter of Bhlhe40 enriched for STAT4 and the permissive histone H3K4me3, and with STAT4-deficient NK cells showing an impairment of Bhlhe40 induction and diminished H3K4me3. Transcriptomic and protein analysis of Bhlhe40-deficient NK cells revealed a defect in IFN-γ production during mouse CMV infection, resulting in diminished protective immunity following viral challenge. Finally, we provide evidence that Bhlhe40 directly promotes IFN-γ by binding throughout the Ifng loci in activated NK cells. Thus, our study reveals how STAT4-mediated control of Bhlhe40 drives protective IFN-γ secretion by NK cells during viral infection.

Identification of a novel cord blood NK cell subpopulation expressing functional programmed death receptor-1.

Background: Natural Killer cells (NKs) represent the innate counterpart of TCRαß lymphocytes and are characterized by a high anti-tumor and an anti-viral cytotoxic activity. Recently, it has been demonstrated that NKs can express PD-1 as an additional inhibitory receptor. Specifically, PD-1 was identified on a subpopulation of terminally differentiated NKs from healthy adults with previous HCMV infection. So far it is unknown whether PD-1 appears during NK-cell development and whether this process is directly or indirectly related to HCMV infection. Methods: In this study, we analyzed the expression and function of PD-1 on Cord Blood derived NKs (CB-NKs) on a large cohort of newborns through multiparametric cytofluorimetric analysis. Results: We identified PD-1 on CB-NKs in more than of half the newborns analyzed. PD-1 was present on CD56dim NKs, and particularly abundant on CD56neg NKs, but only rarely present on CD56bright NKs. Importantly, unlike in adult healthy donors, in CB-NKs PD-1 is co-expressed not only with KIR, but also with NKG2A. PD-1 expression was independent of HCMV mother seropositivity and occurs in the absence of HCMV infection/reactivation during pregnancy. Notably, PD-1 expressed on CB-NKs was functional and mediated negative signals when triggered. Conclusion: To our understanding, this study is the first to report PD-1 expression on CB derived NKs and its features in perinatal conditions. These data may prove important in selecting the most suitable CB derived NK cell population for the development of different immunotherapeutic treatments.

Development of Assays to Measure GNE Gene Potency and Gene Replacement in Skeletal Muscle.

BACKGROUND: GNE myopathy (GNEM) is a severe muscle disease caused by mutations in the UDP-GlcNAc-2-epimerase/ManNAc-6-kinase (GNE) gene, which encodes a bifunctional enzyme required for sialic acid (Sia) biosynthesis. OBJECTIVE: To develop assays to demonstrate the potency of AAV gene therapy vectors in making Sia and to define the dose required for replacement of endogenous mouse Gne gene expression with human GNE in skeletal muscles. METHODS: A MyoD-inducible Gne-deficient cell line, Lec3MyoDI, and a GNE-deficient human muscle cell line, were made and tested to define the potency of various AAV vectors to increase binding of Sia-specific lectins, including MAA and SNA. qPCR and qRT-PCR methods were used to quantify AAV biodistribution and GNE gene expression after intravenous delivery of AAV vectors designed with different promoters in wild-type mice. RESULTS: Lec3 cells showed a strong deficit in MAA binding, while GNE-/-MB135 cells did not. Overexpressing GNE in Lec3 and Lec3MyoDI cells by AAV infection stimulated MAA binding in a dose-dependent manner. Use of a constitutive promoter, CMV, showed higher induction of MAA binding than use of muscle-specific promoters (MCK, MHCK7). rAAVrh74.CMV.GNE stimulated human GNE expression in muscles at levels equivalent to endogenous mouse Gne at a dose of 1×1013vg/kg, while AAVs with muscle-specific promoters required higher doses. AAV biodistribution in skeletal muscles trended higher when CMV was used as the promoter, and this correlated with increased sialylation of its viral capsid. CONCLUSIONS: Lec3 and Lec3MyoDI cells work well to assay the potency of AAV vectors in making Sia. Systemic delivery of rAAVrh74.CMV.GNE can deliver GNE gene replacement to skeletal muscles at doses that do not overwhelm non-muscle tissues, suggesting that AAV vectors that drive constitutive organ expression could be used to treat GNEM.

CLPTM1L is a GPI-anchoring pathway component targeted by HCMV.

The GPI-anchoring pathway plays important roles in normal development and immune modulation. MHC Class I Polypeptide-related Sequence A (MICA) is a stress-induced ligand, downregulated by human cytomegalovirus (HCMV) to escape immune recognition. Its most prevalent allele, MICA*008, is GPI-anchored via an uncharacterized pathway. Here, we identify cleft lip and palate transmembrane protein 1-like protein (CLPTM1L) as a GPI-anchoring pathway component and show that during infection, the HCMV protein US9 downregulates MICA*008 via CLPTM1L. We show that the expression of some GPI-anchored proteins (CD109, CD59, and MELTF)-but not others (ULBP2, ULBP3)-is CLPTM1L-dependent, and further show that like MICA*008, MELTF is downregulated by US9 via CLPTM1L during infection. Mechanistically, we suggest that CLPTM1L's function depends on its interaction with a free form of PIG-T, normally a part of the GPI transamidase complex. We suggest that US9 inhibits this interaction and thereby downregulates the expression of CLPTM1L-dependent proteins. Altogether, we report on a new GPI-anchoring pathway component that is targeted by HCMV.

Enhanced expression of the human Survival motor neuron 1 gene from a codon-optimised cDNA transgene in vitro and in vivo.

Spinal muscular atrophy (SMA) is a neuromuscular disease particularly characterised by degeneration of ventral motor neurons. Survival motor neuron (SMN) 1 gene mutations cause SMA, and gene addition strategies to replace the faulty SMN1 copy are a therapeutic option. We have developed a novel, codon-optimised hSMN1 transgene and produced integration-proficient and integration-deficient lentiviral vectors with cytomegalovirus (CMV), human synapsin (hSYN) or human phosphoglycerate kinase (hPGK) promoters to determine the optimal expression cassette configuration. Integrating, CMV-driven and codon-optimised hSMN1 lentiviral vectors resulted in the highest production of functional SMN protein in vitro. Integration-deficient lentiviral vectors also led to significant expression of the optimised transgene and are expected to be safer than integrating vectors. Lentiviral delivery in culture led to activation of the DNA damage response, in particular elevating levels of phosphorylated ataxia telangiectasia mutated (pATM) and γH2AX, but the optimised hSMN1 transgene showed some protective effects. Neonatal delivery of adeno-associated viral vector (AAV9) vector encoding the optimised transgene to the Smn2B/- mouse model of SMA resulted in a significant increase of SMN protein levels in liver and spinal cord. This work shows the potential of a novel codon-optimised hSMN1 transgene as a therapeutic strategy for SMA.

Murine cytomegalovirus localization and uveitic cell infiltration might both contribute to trabecular meshwork impairment in Posner-Schlossman syndrome: Evidence from an open-angle rat model.

As a special type of glaucoma, Posner-Schlossman syndrome (PSS) is characterized by elevated intraocular pressure (IOP) and anterior uveitis. Cytomegalovirus (CMV) anterior chamber infection has now been considered the leading cause of PSS. We used murine CMV (MCMV) intracameral injection to establish a rat model manifested in IOP elevation and mild anterior uveitis, much like PSS; viral localization and gene expression at various time points and inflammatory cell infiltration derived from innate and adaptive immunity were investigated, as well as pathogenetic changes of the trabecular meshwork (TM). The IOP and uveitic manifestations peaked at 24 h post-infection (p.i.) and returned to normal after 96 h; the iridocorneal angle remained open consistently. At 24 h p.i., leucocytes gathered at the chamber angle. Maximum transcription of MCMV immediate early 1 (IE1) was reached at 24 h in the cornea and 48 h in the iris and ciliary body. MCMV localized in aqueous humor outflow facilities and the iris from 24 h to 28 d p.i. and was detected by in situ hybridization, though it did not transcribe after 7 d p.i. TM and iris pigment epithelial cells harboring viral inclusion bodies and autophagosomes were present at 28 d p.i. These findings shed light on how and where innate and adaptive immunity reacted after MCMV was found and transcribed in a highly ordered cascade, as well as pathogenetic changes in TM as a result of virus and uveitis behaviors.

Intraplacental injection of AAV9-CMV-iCre results in the widespread transduction of multiple organs in double-reporter mouse embryos.

Adeno-associated virus serotype 9 (AAV9) has become a popular tool for gene transfer because of its ability to cross the blood-brain barrier and efficiently transduce genetic material into a variety of cell types. The study utilized GRR (Green-to-Red Reporter) mouse embryos, in which the expression of iCre results in the disappearance of Green Fluorescent Protein (GFP) expression and the detection of Discosoma sp. Red Fluorescent Protein (DsRed) expression by intraplacental injection. Our results demonstrate that AAV9-CMV-iCre can transduce multiple organs in embryos at developmental stages E9.5-E11.5, including the liver, heart, brain, thymus, and intestine. These findings suggest that intraplacental injection of AAV9-CMV-iCre is a viable method for the widespread transduction of GRR mouse embryos.

Plasmodesmal endoplasmic reticulum proteins regulate intercellular trafficking of cucumber mosaic virus in Arabidopsis.

Plasmodesmata (PD) are plasma membrane-lined cytoplasmic nanochannels that mediate cell-to-cell communication across the cell wall. A range of proteins are embedded in the PD plasma membrane and endoplasmic reticulum (ER), and function in regulating PD-mediated symplasmic trafficking. However, knowledge of the nature and function of the ER-embedded proteins in the intercellular movement of non-cell-autonomous proteins is limited. Here, we report the functional characterization of two ER luminal proteins, AtBiP1/2, and two ER integral membrane proteins, AtERdj2A/B, which are located within the PD. These PD proteins were identified as interacting proteins with cucumber mosaic virus (CMV) movement protein (MP) in co-immunoprecipitation studies using an Arabidopsis-derived plasmodesmal-enriched cell wall protein preparation (PECP). The AtBiP1/2 PD location was confirmed by TEM-based immunolocalization, and their AtBiP1/2 signal peptides (SPs) function in PD targeting. In vitro/in vivo pull-down assays revealed the association between AtBiP1/2 and CMV MP, mediated by AtERdj2A, through the formation of an AtBiP1/2-AtERdj2-CMV MP complex within PD. The role of this complex in CMV infection was established, as systemic infection was retarded in bip1/bip2w and erdj2b mutants. Our findings provide a model for a mechanism by which the CMV MP mediates cell-to-cell trafficking of its viral ribonucleoprotein complex.

Murine Cytomegalovirus Infection Induced miR-1929-3p Down-Regulation Promotes the Proliferation and Apoptosis of Vascular Smooth Muscle Cells in Mice by Targeting Endothelin A Receptor and Downstream NLRP3 Activation Pathway.

Our previous study demonstrated in vivo that mouse cytomegalovirus (MCMV) infection promoted vascular remodeling after downregulation of miR-1929-3p. This study aimed to investigate the role of miR-1929-3p/ETAR/NLRP3 pathway in mouse vascular smooth muscle cells (MOVAS) after MCMV infection. First, PCR was used to detect the success of the infection. Second, MOVAS were transfected with the miR-1929-3p mimic, inhibitor, and ETAR overexpressed adenovirus vector. Cell proliferation was detected using EdU, whereas apoptosis was detected using flow cytometry. The expression of miR-1929-3p and ETAR were detected using qRT-PCR. Western blot detected proteins of cell proliferation, apoptosis, and the NLRP3 inflammasome. Interleukin-1ß and interleukin-18 were determined using ELISA. The results revealed that after 48 h, MCMV infection promoted the proliferation of MOVAS when the MOI was 0.01. MCMV infection increased ETAR by downregulating miR-1929-3p. The miR-1929-3p mimic reversed the proliferation and apoptosis, whereas the miR-1929-3p inhibitor promoted this effect. ETAR overexpression further promoted MCMV infection by downregulating miR-1929-3p-mediated proliferation and apoptosis. MCMV infection mediates the downregulation of miR-1929-3p and the upregulation of ETAR, which activates NLRP3 inflammasome. In conclusion, MCMV infection promoted the proliferation of MOVAS, possibly by downregulating miR-1929-3p, promoting the upregulation of the target gene ETAR and activating NLRP3 inflammasome.

Human Cytomegalovirus IE1 Impairs Neuronal Migration by Downregulating Connexin 43.

Human cytomegalovirus (HCMV) is a leading cause of congenital birth defects. Though the underlying mechanisms remain poorly characterized, mouse models of congenital CMV infection have demonstrated that the neuronal migration process is damaged. In this study, we evaluated the effects of HCMV infection on connexin 43 (Cx43), a crucial adhesion molecule mediating neuronal migration. We show in multiple cellular models that HCMV infection downregulated Cx43 posttranslationally. Further analysis identified the immediate early protein IE1 as the viral protein responsible for the reduction of Cx43. IE1 was found to bind the Cx43 C terminus and promote Cx43 degradation through the ubiquitin-proteasome pathway. Deletion of the Cx43-binding site in IE1 rendered it incapable of inducing Cx43 degradation. We validated the IE1-induced loss of Cx43 in vivo by introducing IE1 into the fetal mouse brain. Noteworthily, ectopic IE1 expression induced cortical atrophy and neuronal migration defects. Several lines of evidence suggest that these damages result from decreased Cx43, and restoration of Cx43 levels partially rescued IE1-induced interruption of neuronal migration. Taken together, the results of our investigation reveal a novel mechanism of HCMV-induced neural maldevelopment and identify a potential intervention target. IMPORTANCE Congenital CMV (cCMV) infection causes neurological sequelae in newborns. Recent studies of cCMV pathogenesis in animal models reveal ventriculomegaly and cortical atrophy associated with impaired neural progenitor cell (NPC) proliferation and migration. In this study, we investigated the mechanisms underlying these NPC abnormalities. We show that Cx43, a critical adhesion molecule mediating NPC migration, is downregulated by HCMV infection in vitro and HCMV-IE1 in vivo. We provide evidence that IE1 interacts with the C terminus of Cx43 to promote its ubiquitination and consequent degradation through the proteasome. Moreover, we demonstrate that introducing IE1 into mouse fetal brains led to neuronal migration defects, which was associated with Cx43 reduction. Deletion of the Cx43-binding region in IE1 or ectopic expression of Cx43 rescued the IE1-induced migration defects in vivo. Our study provides insight into how cCMV infection impairs neuronal migration and reveals a target for therapeutic interventions.