Endothelial Cell Tropism Research Articles

Endothelial Cells Stably Infected with Recombinant Kaposi’s Sarcoma-Associated Herpesvirus Display Distinct Viscoelastic and Morphological Properties

PurposeKaposi’s sarcoma-associated herpesvirus (KSHV) is a γ-herpesvirus that has a tropism for endothelial cells and leads to the development of Kaposi’s sarcoma, especially in people living with HIV. The present study aimed to quantify morphological and mechanical changes in endothelial cells after infection with KSHV to assess their potential as diagnostic and therapeutic markers.MethodsVascular (HuARLT2) and lymphatic endothelial cells (LEC) were infected with recombinant KSHV (rKSHV) by spinoculation, establishing stable infections (HuARLT2-rKSHV and LEC-rKSHV). Cellular changes were assessed using mitochondria-tracking microrheology and morphometric analysis.ResultsrKSHV infection increased cellular deformability, indicated by higher mitochondrial mean squared displacement (MSD) for short lag times. Specifically, MSD at τ = 0.19 s was 49.4% and 42.2% higher in HuARLT2-rKSHV and LEC-rKSHV, respectively, compared to uninfected controls. There were 23.9% and 36.7% decreases in the MSD power law exponents for HuARLT2-rKSHV and LEC-rKSHV, respectively, indicating increased cytosolic viscosity associated with rKSHV infection. Infected cells displayed a marked spindloid phenotype with an increase in aspect ratio (29.7%) and decreases in roundness (26.1%) and circularity (25.7%) in HuARLT2-rKSHV, with similar changes observed in LEC-rKSHV.ConclusionsThe quantification of distinct KSHV-induced morpho-mechanical changes in endothelial cells demonstrates the potential of these changes as diagnostic markers and therapeutic targets.

Tropism-shifted AAV-PHP.eB-mediated bFGF gene therapy promotes varied neurorestoration after ischemic stroke in mice

JOURNAL/nrgr/04.03/01300535-202602000-00040/figure1/v/2025-05-05T160104Z/r/image-tiff AAV-PHP.eB is an artificial adeno-associated virus (AAV) that crosses the blood-brain barrier and targets neurons more efficiently than other AAVs when administered systematically. While AAV-PHP.eB has been used in various disease models, its cellular tropism in cerebrovascular diseases remains unclear. In the present study, we aimed to elucidate the tropism of AAV-PHP.eB for different cell types in the brain in a mouse model of ischemic stroke and evaluate its effectiveness in mediating basic fibroblast growth factor ( bFGF ) gene therapy. Mice were injected intravenously with AAV-PHP.eB either 14 days prior to (pre-stroke) or 1 day following (post-stroke) transient middle cerebral artery occlusion. Notably, we observed a shift in tropism from neurons to endothelial cells with post-stroke administration of AAV-PHP.eB-mNeonGreen (mNG). This endothelial cell tropism correlated strongly with expression of the endothelial membrane receptor lymphocyte antigen 6 family member A (Ly6A). Furthermore, AAV-PHP.eB-mediated overexpression of bFGF markedly improved neurobehavioral outcomes and promoted long-term neurogenesis and angiogenesis post-ischemic stroke. Our findings underscore the significance of considering potential tropism shifts when utilizing AAV-PHP.eB-mediated gene therapy in neurological diseases and suggest a promising new strategy for bFGF gene therapy in stroke treatment.

Evaluation of BR1 and BI30 AAVs for Brain Endothelial Tropism.

Brain endothelial cells are critical for homeostasis of the central nervous system. Novel adeno-associated viruses (AAV) with brain endothelial cell tropism have been developed and are beginning to be employed in mechanistic and therapeutic research. Studies using AAVs can be involved in terms of cost, time and personnel, and many groups, including our own, are not experts on the technology. Therefore, it is important to report data using AAVs with the research community as a guide for ongoing and future studies. Here, we detail our initial experience with the two most prevalent AAVs with tropism for brain endothelial cells, AAV-BR1 and AAV-BI30. One of our long-term goals is to express key proteins in brain endothelial cells and determine the impact on brain function. For method development, we administered AAV-BR1 and AAV-BI30 with a CMV-driven fluorescent reporter (CMV-P2A-mCherry) to wild-type mice intravenously (retro-orbital) and measured expression in brain and peripheral tissues by RT-PCR and immunostaining. We found that AAV-BR1 transduces neurons and endothelial cells in the brain, and the lung and liver, whereas AAV-BI30 transduces brain endothelial cells and peripheral tissue. Our data highlights the importance of using the AAV best suited to the scientific question.

Lymphedema and Kaposi sarcoma: A narrative review

Lymphedema and Kaposi sarcoma: A narrative review

Improving retinal vascular endothelial cell tropism through rational rAAV capsid design

Vascular endothelial cells (VEC) are essential for retinal homeostasis and their dysfunction underlies pathogenesis in diabetic retinopathy (DR) and exudative age-related macular degeneration (AMD). Studies have shown that recombinant adeno-associated virus (rAAV) vectors are effective at delivering new genetic material to neural and glial cells within the retina, but targeting VECs remains challenging. To overcome this limitation, herein we developed rAAV capsid mutant vectors with improved tropism towards retinal VEC. rAAV2/2, 2/2[QuadYF-TV], and rAAV2/9 serotype vectors (n = 9, capsid mutants per serotype) expressing GFP were generated by inserting heptameric peptides (7AA) designed to increase endothelial targeting at positions 588 (2/2 and 2/2[QuadYF-TV] or 589 (2/9) of the virus protein (VP 1–3). The packaging and transduction efficiency of the vectors were assessed in HEK293T and bovine VECs using Fluorescence microscopy and flow cytometry, leading to the identification of one mutant, termed EC5, that showed improved endothelial tropism when inserted into all three capsid serotypes. Intra-ocular and intravenous administration of EC5 mutants in C57Bl/6j mice demonstrated moderately improved transduction of the retinal vasculature, particularly surrounding the optic nerve head, and evidence of sinusoidal endothelial cell transduction in the liver. Most notably, intravenous administration of the rAAV2/2[QuadYF-TV] EC5 mutant led to a dramatic and unexpected increase in cardiac muscle transduction.

Molecular analysis of Bartonella spp. in liver tissue of bats from the Atlantic Forest biome, Brazil

The genus Bartonella comprises gram-negative bacilli that possess tropism for erythrocytes and endothelial cells in animals of the orders Rodentia, Lagomorpha, Carnivora, Artiodactyla, Eulipotyphla, and Chiroptera. Bacterial infection may be associated with lymphadenitis, endocarditis, bacillary angiomatosis, and peliosis hepatis. Thirteen species of Bartonella are recognized as zoonotic and bats are considered to be their potential reservoirs. This study aimed to analyze the occurrence of Bartonella spp. in livers of neotropical bats belonging to the families Molossidae, Phyllostomidae, and Vespertilionidae, classified into 21 genera from the Atlantic Forest biome in São Paulo. A total of 341 (n = 341) chiropterans samples were tested for the presence of citrate synthase (gltA) gene of Bartonella by partial amplification using polymerase chain reaction (PCR). Samples of two bats (0.6%) of the species Glossophaga soricina from the municipality of São Roque were tested positive for gltA gene. Phylogenetic analysis indicated that sequences clustered in a clade that was close to the Bartonella sp. detected in G. soricina, which was collected from the Cerrado biome in Tocantins, Brazil. Despite a low prevalence of the detected infection, results indicated that neotropical bats from the Atlantic Forest were potential hosts of Bartonella spp., which might be related to the maintenance of a wild enzootic cycle of the bacterium. Additional studies, particularly on bats of genus Glossophaga, are required to elucidate the dynamics of intraspecific relationships between etiologic agent-vector-hosts.

Organotypic stromal cells impact endothelial cell transcriptome in 3D microvessel networks

Endothelial cells line all major blood vessels and serve as integral regulators of many functions including vessel diameter, cellular trafficking, and transport of soluble mediators. Despite similar functions, the phenotype of endothelial cells is highly organ-specific, yet our understanding of the mechanisms leading to organ-level differentiation is incomplete. We generated 3D microvessel networks by combining a common naïve endothelial cell with six different stromal cells derived from the lung, skin, heart, bone marrow, pancreas, and pancreatic cancer. Single cell RNA-Seq analysis of the microvessel networks reveals five distinct endothelial cell populations, for which the relative proportion depends on the stromal cell population. Morphologic features of the organotypic vessel networks inversely correlate with a cluster of endothelial cells associated with protein synthesis. The organotypic stromal cells were each characterized by a unique subpopulation of cells dedicated to extracellular matrix organization and assembly. Finally, compared to cells in 2D monolayer, the endothelial cell transcriptome from the 3D in vitro heart, skin, lung, and pancreas microvessel networks are more similar to the in vivo endothelial cells from the respective organs. We conclude that stromal cells contribute to endothelial cell and microvessel network organ tropism, and create an endothelial cell phenotype that more closely resembles that present in vivo.

Neutralization of Typhoid Toxin by Alpaca-Derived, Single-Domain Antibodies Targeting the PltB and CdtB Subunits.

ABSTRACTTyphoid toxin is secreted by the typhoid fever-causing bacterial pathogen Salmonella enterica serovar Typhi and has tropism for immune cells and brain endothelial cells. Here, we generated a camelid single-domain antibody (VHH) library from typhoid toxoid-immunized alpacas and identified 41 VHHs selected on the glycan receptor-binding PltB and nuclease CdtB. VHHs exhibiting potent in vitro neutralizing activities from each sequence-based family were epitope binned via competition enzyme-linked immunosorbent assays (ELISAs), leading to 6 distinct VHHs, 2 anti-PltBs (T2E7 and T2G9), and 4 anti-CdtB VHHs (T4C4, T4C12, T4E5, and T4E8), whose in vivo neutralizing activities and associated toxin-neutralizing mechanisms were investigated. We found that T2E7, T2G9, and T4E5 effectively neutralized typhoid toxin in vivo, as demonstrated by 100% survival of mice administered a lethal dose of typhoid toxin and with little to no typhoid toxin-mediated upper motor function defect. Cumulatively, these results highlight the potential of the compact antibodies to neutralize typhoid toxin by targeting the glycan-binding and/or nuclease subunits.

Engineering Functional Vasculature in Decellularized Lungs Depends on Comprehensive Endothelial Cell Tropism.

Tissue engineering using decellularized whole lungs as matrix scaffolds began as a promise for creating autologous transplantable lungs for patients with end-stage lung disease and can also be used to study strategies for lung regeneration. Vascularization remains a critical component for all solid organ bioengineering, yet there has been limited success in generating functional re-endothelialization of most pulmonary vascular segments. We evaluated recellularization of the blood vessel conduits of acellular mouse scaffolds with highly proliferating, rat pulmonary microvascular endothelial progenitor cells (RMEPCs), pulmonary arterial endothelial cells (PAECs) or microvascular endothelial cells (MVECs). After 8 days of pulsatile perfusion, histological analysis showed that PAECs and MVECs possessed selective tropism for larger vessels or microvasculature, respectively. In contrast, RMEPCs lacked site preference and repopulated all vascular segments. RMEPC-derived endothelium exhibited thrombomodulin activity, expression of junctional genes, ability to synthesize endothelial signaling molecules, and formation of a restrictive barrier. The RMEPC phenotype described here could be useful for identifying endothelial progenitors suitable for efficient vascular organ and tissue engineering, regeneration and repair.

Covid-19 and oral diseases: Crosstalk, synergy or association?

SummaryThe coronavirus disease 2019 (Covid‐19) is a viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) that clinically affects multiple organs of the human body. Cells in the oral cavity express viral entry receptor angiotensin‐converting enzyme 2 that allows viral replication and may cause tissue inflammation and destruction. Recent studies have reported that Covid‐19 patients present oral manifestations with multiple clinical aspects. In this review, we aim to summarise main signs and symptoms of Covid‐19 in the oral cavity, its possible association with oral diseases, and the plausible underlying mechanisms of hyperinflammation reflecting crosstalk between Covid‐19 and oral diseases. Ulcers, blisters, necrotising gingivitis, opportunistic coinfections, salivary gland alterations, white and erythematous plaques and gustatory dysfunction were the most reported clinical oral manifestations in patients with Covid‐19. In general, the lesions appear concomitant with the loss of smell and taste. Multiple reports show evidences of necrotic/ulcerative gingiva, oral blisters and hypergrowth of opportunistic oral pathogens. SARS‐CoV‐2 exhibits tropism for endothelial cells and Covid‐19‐mediated endotheliitis can not only promote inflammation in oral tissues but can also facilitate virus spread. In addition, elevated levels of proinflammatory mediators in patients with Covid‐19 and oral infectious disease can impair tissue homeostasis and cause delayed disease resolution. This suggests potential crosstalk of immune‐mediated pathways underlying pathogenesis. Interestingly, few reports suggest recurrent herpetic lesions and higher bacterial growth in Covid‐19 subjects, indicating SARS‐CoV‐2 and oral virus/bacteria interaction. Larger cohort studies comparing SARS‐CoV‐2 negative and positive subjects will reveal oral manifestation of the virus on oral health and its role in exacerbating oral infection.

Pathogenesis of COVID-19-induced ARDS: implications for an ageing population

The coronavirus disease 2019 (COVID-19) pandemic has elicited a swift response by the scientific community to elucidate the pathogenesis of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2)-induced lung injury and develop effective therapeutics. Clinical data indicate that severe COVID-19 most commonly manifests as viral pneumonia-induced acute respiratory distress syndrome (ARDS), a clinical entity mechanistically understood best in the context of influenza A virus-induced pneumonia. Similar to influenza, advanced age has emerged as the leading host risk factor for developing severe COVID-19. In this review we connect the current understanding of the SARS-CoV-2 replication cycle and host response to the clinical presentation of COVID-19, borrowing concepts from influenza A virus-induced ARDS pathogenesis and discussing how these ideas inform our evolving understanding of COVID-19-induced ARDS. We also consider important differences between COVID-19 and influenza, mainly the protean clinical presentation and associated lymphopenia of COVID-19, the contrasting role of interferon-γ in mediating the host immune response to these viruses, and the tropism for vascular endothelial cells of SARS-CoV-2, commenting on the potential limitations of influenza as a model for COVID-19. Finally, we explore hallmarks of ageing that could explain the association between advanced age and susceptibility to severe COVID-19.

Cytomegalovirus Strain TB40/E Restrictions and Adaptations to Growth in ARPE-19 Epithelial Cells.

Despite displaying broad tropism in vivo, human cytomegalovirus (CMV) contained in bodily fluids replicates inefficiently in most cultured cell types except fibroblasts. As propagation in fibroblasts leads to the accumulation of genomic changes, a number of strains were generated by serial passaging on endothelial cells. One of these, TB40/E, was shown to contain a mixture of genetically distinct virus variants, and to retain tropism for fibroblasts, endothelial and epithelial cells. Cloning of an endotheliotropic subpopulation produced the TB40-BAC4 variant, extensively used in CMV tropism studies. Because TB40-BAC4 represents only one of the different variants comprising TB40/E, we generated a series of epithelial-cell adapted stocks derived from a TB40/E mixed stock, rather than from TB40-BAC4. Within two passages on ARPE-19 cells, virus populations were produced with the ability to enter and initiate replication with similar efficiencies in both epithelial cells and fibroblasts. Although the ability to release progeny also increased, cell-free virus yields from ARPE-19 cells remained consistently two to three-logs lower than from fibroblasts, hinting at the existence of a post-entry and post-genome synthesis block in epithelial cells. Multinucleated syncytia also rapidly appeared exclusively in ARPE-19 cell cultures, where their numbers and dimensions increased with virus passage. Irrespective of the number of infected nuclei comprising each syncytium, however, only one cytoplasmic virion assembly compartment was consistently observed, leading us to speculate that improvements in entry efficiency associated with ARPE-19 cell adaptation lead to the development of syncytia, which may negatively affect progeny release by limiting the amount of resources available to maturing virions.

HHV-6A Infection and Systemic Sclerosis: Clues of a Possible Association

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, excessive extracellular matrix deposition, and fibrosis of the skin and internal organs. Several infectious agents, including human herpesvirus-6 (HHV-6), have been suggested as possible triggering factors, but a direct association is still missing. We characterized 26 SSc patients for the presence of HHV-6 in tissues and blood, the anti-HHV-6 response, HLA-G plasma levels, and KIR typing. Given the prominent role of endothelial cells (EC) in SSc pathogenesis, along with HHV-6 tropism for EC, we also investigated the expression of pro-fibrosis factors in HHV-6 infected EC. Results showed the presence of HHV-6A in skin biopsies, and an increased virus load was associated with disease severity and poor natural killer (NK) response against the virus, particularly in subjects exhibiting a KIR2 phenotype. HLA-G plasma levels were significantly higher in HHV-6A/B-KIR2 positive SSc patients and in vitro HHV-6A infection-induced pro-fibrosis factors expression in EC, supporting its role in the development of the fibrosing process. Our data suggest an association between virus infection/reactivation and disease, opening the way to future studies to understand the mechanisms by which HHV-6A might contribute to the multifactorial pathogenesis of SSc.

The culture of primary duck endothelial cells for the study of avian influenza

BackgroundEndothelial cells play a major role in highly pathogenic avian influenza (HPAI) virus pathogenesis in gallinaceous poultry species (e.g. chicken, turkey and quail). Upon infection of gallinaceous poultry with HPAI viruses, endothelial cells throughout the body become rapidly infected, leading to systemic dissemination of the virus, disseminated intravascular coagulation, oedema and haemorrhaging. In contrast, the pathogenesis of HPAI viruses in most wild bird species (e.g. duck, goose and gull species) is not associated with endothelial tropism. Indeed, viral antigen is not found in the endothelial cells of most wild bird species following infection with HPAI viruses. This differential endothelial cell tropism in avian species is poorly understood, mainly due to the absence of appropriate cell culture systems.ResultsHere, we describe the isolation and purification of primary duck endothelial cells from the aorta or bone marrow of Pekin duck embryos. Cells were differentiated in the presence of vascular endothelial growth factor and, if needed, enriched via fluorescent-activated cell sorting based on the uptake of acetylated low-density lipoprotein. The expression of von Willebrand factor, a key marker of endothelial cells, was confirmed by polymerase chain reaction. Monocultures of duck endothelial cells, either derived from the aorta or the bone marrow, were susceptible to infection with an H5N1 HPAI virus but to a much lesser extent than chicken endothelial cells.ConclusionsThe methods described herein to isolate and purify duck endothelial cells from the aorta or bone marrow could also be applied to obtain microvascular endothelial cells from other tissues and organs, such as the lung or the intestine, and represent a valuable tool to study the pathogenesis of avian viruses.

The pentameric complex of human Cytomegalovirus: cell tropism, virus dissemination, immune response and vaccine development.

Between the 1980s and 1990s, three assays were developed for diagnosis of human cytomegalovirus (HCMV) infections: leuko (L)-antigenemia, l-viremia and l-DNAemia, detecting viral protein pp65, infectious virus and viral DNA, respectively, in circulating leukocytes Repeated initial attempts to reproduce the three assays in vitro using laboratory-adapted strains and infected cell cultures were consistently unsuccessful. Results were totally reversed when wild-type HCMV strains were used to infect either fibroblasts or endothelial cells. Careful analysis and sequencing of plaque-purified viruses from recent clinical isolates drew attention to the ULb' region of the HCMV genome. Using bacterial artificial chromosome technology, it was shown by both gain-of-function and loss-of-function experiments that UL131-128 genes are indispensable for virus growth in endothelial cells and virus transfer to leukocytes. In addition, a number of clinical isolates passaged in human fibroblasts had lost both properties (leuko-tropism and endothelial cell-tropism) when displaying a mutation in the UL131-128 locus (referred to as UL128L). In the following years, it was shown that pUL128L was complexed with gH and gL to form the pentameric complex (PC), which is required to infect endothelial, epithelial and myeloid cells. The immune response to PC was studied extensively, particularly its humoral component, showing that the great majority of the neutralizing antibody response is directed to PC. Although anti-HCMV antibodies may act with other mechanisms than mere neutralizing activity, these findings definitely favour their protective activity, thus paving the way to the development of a potentially protective HCMV vaccine.

Endothelial cell tropism is a determinant of H5N1 pathogenesis in mammalian species.

The cellular and molecular mechanisms underpinning the unusually high virulence of highly pathogenic avian influenza H5N1 viruses in mammalian species remains unknown. Here, we investigated if the cell tropism of H5N1 virus is a determinant of enhanced virulence in mammalian species. We engineered H5N1 viruses with restricted cell tropism through the exploitation of cell type-specific microRNA expression by incorporating microRNA target sites into the viral genome. Restriction of H5N1 replication in endothelial cells via miR-126 ameliorated disease symptoms, prevented systemic viral spread and limited mortality, despite showing similar levels of peak viral replication in the lungs as compared to control virus-infected mice. Similarly, restriction of H5N1 replication in endothelial cells resulted in ameliorated disease symptoms and decreased viral spread in ferrets. Our studies demonstrate that H5N1 infection of endothelial cells results in excessive production of cytokines and reduces endothelial barrier integrity in the lungs, which culminates in vascular leakage and viral pneumonia. Importantly, our studies suggest a need for a combinational therapy that targets viral components, suppresses host immune responses, and improves endothelial barrier integrity for the treatment of highly pathogenic H5N1 virus infections.

Angiosarcoma in HIV-negative patients is not associated with HHV-8.

Angiosarcoma in HIV-negative patients is not associated with HHV-8.

AXL-Mediated Productive Infection of Human Endothelial Cells by Zika Virus.

The mosquito-borne Zika virus (ZIKV) is now recognized as a blood-borne pathogen, raising an important question about how the virus gets into human bloodstream. The imminent threat of the ZIKV epidemic to the global blood supply also demands novel therapeutics to stop virus transmission though transfusion. We intend to characterize ZIKV tropism for human endothelial cells (ECs) and provide potential targets for intervention. We conducted immunostaining, plaque assay, and quantitative reverse transcription-polymerase chain reaction of ZIKV RNA to evaluate the possible infection of ECs by ZIKV. Both the African and the South American ZIKV strains readily infect human umbilical vein endothelial cells and human ECs derived from aortic and coronary artery, as well as the saphenous vein. Infected ECs released infectious progeny virus. Compared with the African strains, South American ZIKV isolates replicate faster in ECs and are partially cytopathic, suggesting enhanced virulence of these isolates. Flow cytometric analyses showed that the susceptibility of ECs positively correlated with the cell surface levels of tyrosine-protein kinase receptor UFO (AXL) receptor tyrosine kinase. Gain- and loss-of-function studies further revealed that AXL is required for ZIKV entry at a postbinding step. Finally, small-molecule inhibitors of the AXL kinase significantly reduced ZIKA infection of ECs. We identified EC as a key cell type for ZIKV infection. These data support the view of hematogenous dissemination of ZIKV and implicate AXL as a new target for antiviral therapy.

Systemic Vascular Transduction by Capsid Mutant Adeno-Associated Virus After Intravenous Injection.

The ability to effectively deliver genetic material to vascular endothelial cells remains one of the greatest unmet challenges facing the development of gene therapies to prevent diseases with underlying vascular etiology, such as diabetes, atherosclerosis, and age-related macular degeneration. Herein, we assess the effectiveness of an rAAV2-based capsid mutant vector (Y272F, Y444F, Y500F, Y730F, T491V; termed QuadYF+TV) with strong endothelial cell tropism at transducing the vasculature after systemic administration. Intravenous injection of QuadYF+TV resulted in widespread transduction throughout the vasculature of several major organ systems, as assessed by in vivo bioluminescence imaging and postmortem histology. Robust transduction of lung tissue was observed in QuadYF+TV-injected mice, indicating a role for intravenous gene delivery in the treatment of chronic diseases presenting with pulmonary complications, such as α1-antitrypsin deficiency. The QuadYF+TV vector cross-reacted strongly with AAV2 neutralizing antibodies, however, indicating that a targeted delivery strategy may be required to maximize clinical translatability.

Brain Invasion by Mouse Hepatitis Virus Depends on Impairment of Tight Junctions and Beta Interferon Production in Brain Microvascular Endothelial Cells.

Coronaviruses (CoVs) have shown neuroinvasive properties in humans and animals secondary to replication in peripheral organs, but the mechanism of neuroinvasion is unknown. The major aim of our work was to evaluate the ability of CoVs to enter the central nervous system (CNS) through the blood-brain barrier (BBB). Using the highly hepatotropic mouse hepatitis virus type 3 (MHV3), its attenuated variant, 51.6-MHV3, which shows low tropism for endothelial cells, and the weakly hepatotropic MHV-A59 strain from the murine coronavirus group, we investigated the virus-induced dysfunctions of BBB in vivo and in brain microvascular endothelial cells (BMECs) in vitro. We report here a MHV strain-specific ability to cross the BBB during acute infection according to their virulence for liver. Brain invasion was observed only in MHV3-infected mice and correlated with enhanced BBB permeability associated with decreased expression of zona occludens protein 1 (ZO-1), VE-cadherin, and occludin, but not claudin-5, in the brain or in cultured BMECs. BBB breakdown in MHV3 infection was not related to production of barrier-dysregulating inflammatory cytokines or chemokines by infected BMECs but rather to a downregulation of barrier protective beta interferon (IFN-β) production. Our findings highlight the importance of IFN-β production by infected BMECs in preserving BBB function and preventing access of blood-borne infectious viruses to the brain. Coronaviruses (CoVs) infect several mammals, including humans, and are associated with respiratory, gastrointestinal, and/or neurological diseases. There is some evidence that suggest that human respiratory CoVs may show neuroinvasive properties. Indeed, the severe acute respiratory syndrome coronavirus (SARS-CoV), causing severe acute respiratory syndrome, and the CoVs OC43 and 229E were found in the brains of SARS patients and multiple sclerosis patients, respectively. These findings suggest that hematogenously spread CoVs may gain access to the CNS at the BBB level. Herein we report for the first time that CoVs exhibit the ability to cross the BBB according to strain virulence. BBB invasion by CoVs correlates with virus-induced disruption of tight junctions on BMECs, leading to BBB dysfunction and enhanced permeability. We provide evidence that production of IFN-β by BMECs during CoV infection may prevent BBB breakdown and brain viral invasion.