Ebolavirus: An Overview of Molecular and Clinical Pathogenesis

Annexin A2 depletion exacerbates the intracerebral microhemorrhage induced by acute rickettsia and Ebola virus infections

Intracerebral microhemorrhages (CMHs) are small foci of hemorrhages in the cerebrum. Acute infections induced by some intracellular pathogens, including rickettsia, can result in CMHs. Annexin a2 (ANXA2) has been documented to play a functional role during intracellular bacterial adhesion. Here we report that ANXA2-knockout (KO) mice are more susceptible to CMHs in response to rickettsia and Ebola virus infections, suggesting an essential role of ANXA2 in protecting vascular integrity during these intracellular pathogen infections. Proteomic analysis via mass spectrometry of whole brain lysates and brain-derived endosomes from ANXA2-KO and wild-type (WT) mice post-infection with R. australis revealed that a variety of significant proteins were differentially expressed, and the follow-up function enrichment analysis had identified several relevant cell-cell junction functions. Immunohistology study confirmed that both infected WT and infected ANXA2-KO mice were subjected to adherens junctional protein (VE-cadherin) damages. However, key blood-brain barrier (BBB) components, tight junctional proteins ZO-1 and occludin, were disorganized in the brains from R. australis-infected ANXA2-KO mice, but not those of infected WT mice. Similar ANXA2-KO dependent CMHs and fragments of ZO-1 and occludin were also observed in Ebola virus-infected ANXA2-KO mice, but not found in infected WT mice. Overall, our study revealed a novel role of ANXA2 in the formation of CMHs during R. australis and Ebola virus infections; and the underlying mechanism is relevant to the role of ANXA2-regulated tight junctions and its role in stabilizing the BBB in these deadly infections.

Characterization of Ebola Virus Disease (EVD) in Rhesus Monkeys for Development of EVD Therapeutics

Recent Ebola virus (EBOV) outbreaks in West Africa and the Democratic Republic of the Congo have highlighted the urgent need for approval of medical countermeasures for treatment and prevention of EBOV disease (EVD). Until recently, when successes were achieved in characterizing the efficacy of multiple experimental EVD therapeutics in humans, the only feasible way to obtain data regarding potential clinical benefits of candidate therapeutics was by conducting well-controlled animal studies. Nonclinical studies are likely to continue to be important tools for screening and development of new candidates with improved pharmacological properties. Here, we describe a natural history study to characterize the time course and order of progression of the disease manifestations of EVD in rhesus monkeys. In 12 rhesus monkeys exposed by the intramuscular route to 1000 plaque-forming units of EBOV, multiple endpoints were monitored for 28 days following exposure. The disease progressed rapidly with mortality events occurring 7–10 days after exposure. Key disease manifestations observed consistently across the infected animals included, but were not limited to, viremia, fever, systemic inflammation, coagulopathy, lymphocytolysis, renal tubular necrosis with mineralization, and hepatocellular degeneration and necrosis.

Perspectives towards antiviral drug discovery against Ebola virus

Ebola virus disease (EVD), caused by Ebola viruses, resulted in more than 11 500 deaths according to a recent 2018 WHO report. With mortality rates up to 90%, it is nowadays one of the most deadly infectious diseases. However, no Food and Drug Administration‐approved Ebola drugs or vaccines are available yet with the mainstay of therapy being supportive care. The high fatality rate and absence of effective treatment or vaccination make Ebola virus a category‐A biothreat pathogen. Fortunately, a series of investigational countermeasures have been developed to control and prevent this global threat. This review summarizes the recent therapeutic advances and ongoing research progress from research and development to clinical trials in the development of small‐molecule antiviral drugs, small‐interference RNA molecules, phosphorodiamidate morpholino oligomers, full‐length monoclonal antibodies, and vaccines. Moreover, difficulties are highlighted in the search for effective countermeasures against EVD with additional focus on the interplay between available in silico prediction methods and their evidenced potential in antiviral drug discovery.

Ocular complications in Ebola virus disease survivors: the importance of continuing care in West Africa

Introduction

The largest Ebola virus (EBOV) outbreak occurred from 2013 - 2016 in West Africa and consequently resulted in the largest cohort of Ebola virus disease (EVD) survivors to date. Ocular disease is among the most common sequelae reported in EVD survivors. This review discusses the prevalence, manifestations, pathogenesis, diagnosis and management of EVD-related ocular disease.

Areas covered

An extensive review of the literature was performed to detail the prevalence and manifestations of EVD-related ocular disease. We also review current eye screening and treatment strategies and our current understanding and approach to invasive ophthalmic procedures including surgery.

Expert opinion

The ocular sequelae of EVD can lead to vision impairment or blindness, if untreated. Keys to the prevention of such an outcome include timely evaluation and access to appropriate ophthalmic care. The persistence of EBOV in the eye and other immune-privileged sites is the subject of ongoing investigation, but should not be a barrier to care if appropriate screening and biosafety measures are taken. Improved understanding of the pathogenesis of this condition and ongoing clinical care are needed for EVD survivors at-risk for ocular complications.

An update on ocular complications of Ebola virus disease

PURPOSE OF REVIEW

This review provides a summary of our current understanding of the ophthalmic manifestations of Ebola virus disease (EVD), pathogenesis, treatment options and directions for future study. The individual, public health and global health implications of eye disease in EVD survivors are discussed.

RECENT FINDINGS

The West Africa EVD outbreak was of unprecedented magnitude, leading to the largest survivor cohort since the first documented EVD outbreak in 1976. Because of the magnitude of the recent outbreak, thousands of survivors are at-risk of systemic and ophthalmic sequelae termed the 'post Ebola virus disease syndrome'. Uveitis is the most common finding during EVD convalescence and may lead to severe vision impairment or blindness in 40% of affected individuals. Ocular complications leading to vision loss include cataract, retinal scarring, optic neuropathy, hypotony and phthisis bulbi. The pathogenesis of eye disease in EVD survivors likely involves Ebola virus persistence, severe inflammation and tissue edema, which present as acute, rapidly progressive disease or chronic, smoldering disease. Further studies into disease pathogenesis including mechanisms of viral persistence may provide guidance into therapies for uveitis secondary to EVD.

SUMMARY

Uveitis is the most common ophthalmic finding in EVD survivors and can lead to vision loss. Further studies into the clinical manifestations and mechanisms of disease are needed to improve therapies for EVD survivors who often have limited access to ophthalmic medical and surgical care.