Ebola virus disrupts the inner blood-retinal barrier by induction of vascular endothelial growth factor in pericytes

Ponatinib and other clinically approved inhibitors of Src and Rho-A kinases abrogate dengue virus serotype 2- induced endothelial permeability

Severe dengue often presents as shock syndrome with enhanced vascular permeability and plasma leakage into tissue spaces. In vitro studies have documented the role of Src family kinases (SFKs) and RhoA-kinases (ROCK) in dengue virus serotype 2 (DENV2)-induced endothelial permeability. Here, we show that the FDA-approved SFK inhibitors Bosutinib, Vandetanib and Ponatinib, as well as the ROCK inhibitors, Netarsudil and Ripasudil significantly inhibit DENV2-induced endothelial permeability. In cultured telomerase immortalized human microvascular endothelial cells (HMEC-1), treatment with these inhibitors reduced the phosphorylation of VE-Cadherin, Src and myosin light chain 2 (MLC2) proteins that were upregulated during DENV2 infection. It also prevented the loss of VE-Cadherin from the inter-endothelial cell junctions induced by viral infection. In in-vivo studies using DENV2-infected AG129 IFN receptor-α/β/γ deficient mice, ponatinib, when administered 24 h post-infection onwards, demonstrated significant benefits in improving body weight, clinical outcomes, and survival rates. While all virus-infected, untreated mice died by day-10 post-infection, 80% of the ponatinib-treated mice survived, and approximately 60% were still alive at the end of the 15-day observation period. The treatment also significantly reduced disease severity factors such as vascular leakage, thrombocytopenia; mRNA transcript levels of proinflammatory cytokines such as IL-1β and TNF-α; and restored liver function. Comparable effects were observed even when ponatinib treatment was initiated after symptom onset. The results highlight ponatinib as an effective therapeutic option in severe dengue; and also a similar potential for other FDA- approved SFK and ROCK inhibitors.

Ebola Virus Glycoprotein Impairs Human Retinal Pigment Epithelial Barrier Function via the PI3K/Akt-Nrf2 Pathway

Ebola virus (EBOV) causes deadly Ebola virus disease (EVD), and EVD survivors are at high risk of developing blinding ocular complications, which associate with the breakdown of human retinal pigment epithelial (RPE) barrier. Here, we demonstrated EBOV glycoprotein (GP) could directly impair RPE barrier function. EBOV GP significantly decreased expression of tight junction (TJ) proteins in RPE monolayers, resulting in an increase of monolayer permeability. EBOV GP activated PI3K/Akt pathway and induced oxidative stress in RPE cells as evidenced by an increase in the production of reactive oxygen species (ROS), decreased expression of an antioxidant factor, nuclear factor erythroid 2-related factor 2 (Nrf2), and its downstream proteins heme oxygenase 1 (HO-1) and NAD(P)H dehydrogenase (quinone) 1 (NQO1). We found activating Nrf2 could counteract EBOV GP-induced RPE barrier injury. Furthermore, GP2 subunit is the key region in the GP that impairs RPE barrier function. Destruction of RPE barrier function by EBOV GP leads to translocation of bacteria and HIV-1. We confirmed EBOV GP-mediated impairment of RPE barrier function in mice. As an Nrf2 activator, resveratrol displays protective effects on the RPE barrier function. Collectively, our study demonstrates EBOV GP impairs the RPE barrier function through PI3K/Akt-Nrf2 pathway and resveratrol is a promising therapeutic agent for EVD-associated retinal complications.

Ocular neuroinflammatory response secondary to SARS-CoV-2 infection-a review

With the consistent occurrence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the prevalence of various ocular complications has increased over time. SARS-CoV-2 infection has been shown to have neurotropism and therefore to lead to not only peripheral inflammatory responses but also neuroinflammation. Because the receptor for SARS-CoV-2, angiotensin-converting enzyme 2 (ACE2), can be found in many intraocular tissues, coronavirus disease 2019 (COVID-19) may also contribute to persistent intraocular neuroinflammation, microcirculation dysfunction and ocular symptoms. Increased awareness of neuroinflammation and future research on interventional strategies for SARS-CoV-2 infection are important for improving long-term outcomes, reducing disease burden, and improving quality of life. Therefore, the aim of this review is to focus on SARS-CoV-2 infection and intraocular neuroinflammation and to discuss current evidence and future perspectives, especially possible connections between conditions and potential treatment strategies.

Neurovascular dysfunction in psychiatric disorders: Underlying mechanisms and therapeutic approaches

BACKGROUND

Neurovascular interfaces, specifically the blood-brain barrier (BBB) and blood-retinal barrier (BRB), play pivotal roles in maintaining the homeostasis of the central nervous system (CNS). For a long time, these structures were seen only as a way of protection, but we currently know that they have a critical role in CNS (dys)function. Several studies have identified neurovascular alterations in early stages of brain and eye diseases, contributing to the pathophysiology of such conditions. More recently, interesting data have also highlighted the importance of neurovasculature in psychiatric disorders.

METHODS

Using the PubMed database, we brought together the evidence concerning the changes in BBB and BRB under psychiatric conditions, with a focus on anxiety, major depressive disorder (MDD), attention-deficit/hyperactivity disorder (ADHD) and drug abuse, specifically related with methamphetamine (METH) and cocaine consumption.

RESULTS

We summarized the main findings obtained from in vitro and animal studies, as well as clinical research that has been undertaken to identify neurovascular abnormalities upon such neuropsychiatric disorders. The drivers of barrier alterations were examined, namely the role of neuroinflammation, while reporting putative barrier-associated biomarkers of these disorders.

CONCLUSION

This review underscores the critical need for a deeper understanding of BBB and BRB function in neuropsychiatric conditions and their potential as therapeutic targets while elucidating the key players involved. The innovative approaches to managing these complex disorders are also addressed while bridging the gap concerning what is currently known regarding the association between neuropsychiatric conditions and their vascular implications.

Hippo signaling pathway regulates Ebola virus transcription and egress

Filovirus-host interactions play important roles in all stages of the virus lifecycle. Here, we identify LATS1/2 kinases and YAP, key components of the Hippo pathway, as critical regulators of EBOV transcription and egress. Specifically, we find that when YAP is phosphorylated by LATS1/2, it localizes to the cytoplasm (Hippo "ON") where it sequesters VP40 to prevent egress. In contrast, when the Hippo pathway is "OFF", unphosphorylated YAP translocates to the nucleus where it transcriptionally activates host genes and promotes viral egress. Our data reveal that LATS2 indirectly modulates filoviral VP40-mediated egress through phosphorylation of AMOTp130, a positive regulator of viral egress, but more surprisingly that LATS1/2 kinases directly modulate EBOV transcription by phosphorylating VP30, an essential regulator of viral transcription. In sum, our findings highlight the potential to exploit the Hippo pathway/filovirus axis for the development of host-oriented countermeasures targeting EBOV and related filoviruses.

Ebola virus-induced eye sequelae: a murine model for evaluating glycoprotein-targeting therapeutics

BACKGROUND

Ebola virus disease (EVD) survivors experience ocular sequelae including retinal lesions, cataracts, and vision loss. While monoclonal antibodies targeting the Ebola virus glycoprotein (EBOV-GP) have shown promise in improving prognosis, their effectiveness in mitigating ocular sequelae remains uncertain.

METHODS

We developed and characterized a BSL-2-compatible immunocompetent mouse model to evaluate therapeutics targeting EBOV-GP by inoculating neonatal mice with vesicular stomatitis virus expressing EBOV-GP (VSV-EBOV). To examine the impact of anti-EBOV-GP antibody treatment on acute retinitis and ocular sequelae, VSV-EBOV-infected mice were treated with polyclonal antibodies or monoclonal antibody preparations with antibody-dependent cellular cytotoxicity (ADCC-mAb) or neutralizing activity (NEUT-mAb).

FINDINGS

Treatment with all anti-EBOV-GP antibodies tested dramatically reduced viremia and improved survival. Further, all treatments reduced the incidence of cataracts. However, NEUT-mAb alone or in combination with ADCC-mAb reduced viral load in the eyes, downregulated the ocular immune and inflammatory responses, and minimized retinal damage more effectively.

INTERPRETATION

Anti-EBOV-GP antibodies can improve survival among EVD patients, but improved therapeutics are needed to reduce life altering sequelae. This animal model offers a new platform to examine the acute and long-term effect of the virus in the eye and the relative impact of therapeutic candidates targeting EBOV-GP. Results indicate that even antibodies that improve systemic viral clearance and survival can differ in their capacity to reduce acute ocular inflammation, and long-term retinal pathology and corneal degeneration.

FUNDING

This study was partly supported by Postgraduate Research Fellowship Awards from ORISE through an interagency agreement between the US DOE and the US FDA.

SARS-CoV-2 infects cells lining the blood-retinal barrier and induces a hyperinflammatory immune response in the retina via systemic exposure

SARS-CoV-2 has been shown to cause wide-ranging ocular abnormalities and vision impairment in COVID-19 patients. However, there is limited understanding of SARS-CoV-2 in ocular transmission, tropism, and associated pathologies. The presence of viral RNA in corneal/conjunctival tissue and tears, along with the evidence of viral entry receptors on the ocular surface, has led to speculation that the eye may serve as a potential route of SARS-CoV-2 transmission. Here, we investigated the interaction of SARS-CoV-2 with cells lining the blood-retinal barrier (BRB) and the role of the eye in its transmission and tropism. The results from our study suggest that SARS-CoV-2 ocular exposure does not cause lung infection and moribund illness in K18-hACE2 mice despite the extended presence of viral remnants in various ocular tissues. In contrast, intranasal exposure not only resulted in SARS-CoV-2 spike (S) protein presence in different ocular tissues but also induces a hyperinflammatory immune response in the retina. Additionally, the long-term exposure to viral S-protein caused microaneurysm, retinal pigmented epithelium (RPE) mottling, retinal atrophy, and vein occlusion in mouse eyes. Notably, cells lining the BRB, the outer barrier, RPE, and the inner barrier, retinal vascular endothelium, were highly permissive to SARS-CoV-2 replication. Unexpectedly, primary human corneal epithelial cells were comparatively resistant to SARS-CoV-2 infection. The cells lining the BRB showed induced expression of viral entry receptors and increased susceptibility towards SARS-CoV-2-induced cell death. Furthermore, hyperglycemic conditions enhanced the viral entry receptor expression, infectivity, and susceptibility of SARS-CoV-2-induced cell death in the BRB cells, confirming the reported heightened pathological manifestations in comorbid populations. Collectively, our study provides the first evidence of SARS-CoV-2 ocular tropism via cells lining the BRB and that the virus can infect the retina via systemic permeation and induce retinal inflammation.

Contrasting effects of filamin A and B proteins in modulating filovirus entry

Ebola (EBOV) and Marburg viruses (MARV) cause severe hemorrhagic fever associated with high mortality rates in humans. A better understanding of filovirus-host interactions that regulate the EBOV and MARV lifecycles can provide biological and mechanistic insight critical for therapeutic development. EBOV glycoprotein (eGP) and MARV glycoprotein (mGP) mediate entry into host cells primarily by actin-dependent macropinocytosis. Here, we identified actin-binding cytoskeletal crosslinking proteins filamin A (FLNa) and B (FLNb) as important regulators of both EBOV and MARV entry. We found that entry of pseudotype psVSV-RFP-eGP, infectious recombinant rVSV-eGP-mCherry, and live authentic EBOV and MARV was inhibited in filamin A knockdown (FLNaKD) cells, but was surprisingly enhanced in filamin B knockdown (FLNbKD) cells. Mechanistically, our findings suggest that differential regulation of macropinocytosis by FLNa and FLNb likely contributes to their specific effects on EBOV and MARV entry. This study is the first to identify the filamin family of proteins as regulators of EBOV and MARV entry. These findings may provide insight into the development of new countermeasures to prevent EBOV and MARV infections.