B4: ebola Flashcards
What virus family does Ebola belong to?
Filoviridae
What are the key characteristics of filoviruses?
Filamentous morphology, highly pleomorphic, cause severe haemorrhagic fever
When and where was Ebola virus first identified?
Zaire, 1976
How many subtypes of Ebola virus exist?
Six: Zaire, Bundibugyo, Sudan, Taï Forest, Reston, Bombali
Which Ebola strain is the most deadly?
Zaire (ZEBOV), with higher mortality than Sudan (SEBOV)
How is Ebola virus transmitted?
Direct contact with bodily fluids of infected persons or animals
What is the incubation period for Ebola?
3-16 days
What are the initial symptoms of Ebola virus disease?
Flu-like symptoms: fever, headache, aches, pains
What additional symptoms occur around days 5-7?
Maculopapular rash in ~50% of patients
What are severe symptoms of Ebola virus infection?
Gastrointestinal bleeding, organ failure, shock, and death in 50-90% of cases
What is the key approach to Ebola virus containment?
Barrier nursing, quarantine, and education
What is the name of the Ebola vaccine?
Ervebo
How is the Ervebo vaccine administered?
Dose 1: Zabdeno, Dose 2: Mvabea (8 weeks later)
Is the Ebola vaccine used during outbreaks?
No, it is used prophylactically
What is believed to be the primary reservoir of Ebola virus?
Fruit bats
What evidence supports bats as an Ebola virus reservoir?
Leroy et al. (2005): fruit bats were either IgG or PCR positive but asymptomatic
What animals have been linked to Ebola virus transmission but are not reservoirs?
Chimpanzees, gorillas, and antelope
What is the genome structure of Ebola virus?
Negative-sense, single-stranded RNA (-ssRNA)
What is the function of the L protein in Ebola virus?
It acts as the RNA-dependent RNA polymerase (RdRp)
What is the shape of the Ebola virus nucleocapsid?
Helical
How is Ebola virus related to other viruses?
It is closely related to rhabdoviruses (e.g. rabies) and paramyxoviruses (e.g. measles)
What viral order does Ebola virus belong to?
Mononegavirales (-ve ssRNA genome)
What is a pseudotype virus?
A modified virus used for studying viral entry, e.g., VSV with Ebola glycoprotein
What is the role of the Ebola virus glycoprotein (GP)?
Mediates viral entry into host cells
What does it mean that Ebola virus is pantropic?
It can infect and damage many different organs, particularly the liver and spleen
Which immune cells does Ebola virus initially infect?
Monocytes, dendritic cells, macrophages
Which cells does Ebola virus infect later in the disease?
Endothelial cells
What is the estimated viral load in the blood during peak infection?
Up to 10¹⁰ virus particles/ml
What are the major immune responses induced by Ebola virus infection?
Cytokine storm, suppression of interferons, and depletion of lymphocytes
Which cytokines are involved in the Ebola virus-induced cytokine storm?
TNF-α, IFN-γ, but NOT IFN-α or IFN-β
hat immune response does Ebola virus suppress?
Production and action of IFN-α and IFN-β
What are the consequences of immune suppression by Ebola virus?
Decreased dendritic cell maturation, reduced T & B cell activation, and NK cell depletion
How does Ebola virus cause coagulopathy?
Increased tissue factor (TF) expression on macrophages and endothelial cells
What is the predominant coagulation defect in Ebola virus disease?
Inappropriate coagulation, rather than lack of coagulation
What are some hypotheses for antibody-dependent enhancement of infection?
C1q/Ab/virus complex may contribute to hyperactivation of the immune system
What are the two major components of Ebola virus pathogenesis?
1) Suppression of immune response, 2) Hyperactivation of immune response
Why is Ebola virus highly contagious?
Transmitted in body fluids, remains infectious for long periods
How does the Ebola vaccine help prevent infection?
It stimulates a strong immune response before exposure to the virus
What factors contribute to the high mortality rate of Ebola virus?
Severe immune dysregulation, widespread organ damage, lack of effective treatment
What is a key similarity between Ebola virus and measles virus in immune evasion?
Both suppress IFN-α & IFN-β responses
Why are pseudotype viruses used in Ebola virus research?
They allow researchers to study Ebola virus entry and immune responses safely by replacing the Ebola glycoprotein in a non-lethal virus like VSV.
How long can Ebola virus survive outside the body?
Ebola virus can remain viable for hours to days on surfaces, depending on environmental conditions like temperature and humidity.
What are the differences between human-to-human and animal-to-human Ebola virus transmission?
Human-to-human occurs via direct contact with bodily fluids, while animal-to-human happens through handling infected wildlife (e.g., fruit bats, primates).
What is the role of Ebola virus glycoprotein (GP)?
GP mediates virus entry by binding to host receptors and inducing membrane fusion. It also helps the virus evade immune detection.
What are the functions of VP35 and VP40 in Ebola virus?
VP35 suppresses interferon production, helping the virus evade the immune response, while VP40 regulates virus assembly and budding.
How does Ebola virus cause haemorrhagic symptoms?
The virus infects endothelial cells, triggering a cytokine storm and coagulation defects, leading to blood vessel leakage and internal bleeding.
How do macrophages contribute to the spread of Ebola virus?
Infected macrophages travel through the bloodstream, spreading the virus to multiple organs, including the liver and spleen, leading to widespread damage.
Why isn’t Ervebo used during Ebola outbreaks?
Ervebo is used prophylactically for high-risk individuals but not for immediate outbreak control, as it takes time for immunity to develop.
What monoclonal antibody treatments exist for Ebola virus?
Inmazeb (REGN-EB3) and Ebanga are FDA-approved monoclonal antibody therapies that neutralize Ebola virus and improve survival rates.
How does Ebola virus affect NK cells?
Ebola virus depletes NK cells, reducing the body’s ability to clear infected cells and increasing viral spread.
