EBOLA: niente si trasmette come la paura
4 dicembre 2014
Sala Congressi - Asse Didattico E
Complesso Universitario di Monserrato
La biologia del virus Ebola
Alessandra Pani
Dipartimento di Scienze Biomediche
Università degli Studi di Cagliari
La biologia del virus Ebola
1. Struttura del virione
2. Infezione e replicazione
3. Fattori di virulenza e di evasione dalla risposta
immunitaria
4. Target molecolari per lo sviluppo di farmaci
Filovirus
• Filamentous or Bacillus form
• Vary greatly in length (up to 14000 nm)
Mean Unit Length
Ebola - 1200 nm
Marburg - 860 nm
• Uniform diameter of 80 nm
Genome and Proteins
EBOV-Z
MARV
Non-segmented, negative-strand RNA
Filovirus Genome – 19 kb
7 Genes
Nucleotide and amino acid differences b/w
• Marburg and Ebola – 55%
• Ebola – 37 to 41%
Overlaps
•
•
1 in Marburg genome – VP30 to VP24
2 in Ebola genome-VP35 to VP40 & GP to
VP30
Mühlberger E., Future Virology 2007
EboV-Z GP cleaved by FURIN
Hofmann-Winkler et al.,Viruses 2012
La biologia del virus Ebola
1. Struttura del virione
2. Infezione e replicazione
3. Fattori di virulenza e di evasione dalla
risposta immunitaria
4. Target molecolari per lo sviluppo di farmaci
Filovirus life cycle
Dolnik et al., Cell. Mol. Life Sci. 2008
Dolnik et al., Cell. Mol. Life Sci. 2008
Miller & Chandran, Curr Opinion Virol 2012
Kondratowicz et al., Proc Natl Acad Sci USA 2011
Hofmann-Winkler, Viruses 2012
Lectins involved in Filovirus attachment
GP-binding lectins
Tissue distribution
ASGPR-1
•hepatocytes
hMGL
•monocyte-derived immature dendritic cells
•intermediate precursors of macrophages
DC-SIGN
•dendritic cells
•fetal macrophages
•decidual macrophages
•alveolar macrophages
•platelets
•activated primary B-cells
DC-SIGNR
•endothelial cells in the placenta
•endothelial cells in the liver and lymph node
sinuses
LSECtin
•sinusoidal endothelial cells in liver, lymph nodes
and bone marrow
•thymic dendritic cells
•monocyte-derived macrophages
•peripheral blood cells
Cellular endocytic pathways and factors implicated
in Filovirus entry
Bhattacharyya et al., Virology 2010
Saeed et al., PLoS Pathog 2010
Carette et al., Nature 2011
Cote et al., Nature 2011
Filovirus life cycle
Dolnik et al., Cell. Mol. Life Sci. 2008
GP expression in Ebola virus
Transcriptional RNA Editing
At a series of 7 U’s on the GP RNA insert a non-template coded
adenosine:
• 20% of GP mRNA is edited
GP
• 80% of GP mRNA is not edited
sGP
EBOV GP gene encodes 2 products: 2 ORF
(MARV GP gene encodes 1 product: 1 ORF)
GP-RNA Editing
• Over-expression of GP
• Cytotoxicity and eventual cell death
GP expression and cytotoxicity can be regulated by virus through
transcriptional RNA editing and secretory-GP expression
Volchkov et al., Science 2001
Filovirus life cycle
Dolnik et al., Cell. Mol. Life Sci. 2008
La biologia del virus Ebola
1. Struttura del virione
2. Infezione e replicazione
3. Fattori di virulenza e di evasione dalla
risposta immunitaria
4. Target molecolari per lo sviluppo di farmaci
EboV virulence factors: GP and sGP
GP
1. Specific region of GP induces cytotoxic effects in endothelial cells
-Rapid release
of vasoactive agents from infected cells
-Induces cell rounding and detachment from extracellular matrices
-Increases cell membrane permeability
2. Specific region of GP contribute to evasion
of host immunity
-Possible immunosuppressive sequence in GP2: blocks lymphocyte
mitogen-stimulated proliferation in vitro
sGP
1. Inhibits early activation of
neutrophils
-Binds to neutrophils via CD16b cell surface receptor
2. Sequesters neutralizing antibodies
Yang et al., Nature Med 2000
Simmons et al., J Virol 2002
Marzi et al., Virology 2006
EboV virulence factors: VP35 and VP24
Dolnik et al., Cell. Mol. Life Sci. 2008
Ramanan et al., Viruses 2011
Wei Xu et al., Cell Host & Microbs 2014
VP35: No IFN-α/β
VP24: No IFNantiviral effectors
Multiple funtions
of
IFN-α and IFN-β
1
(antiviral-IFNs)
2
3
• Antiviral state of host cells
• Activation of immune cells
5
• Induction of IFN-γ (immune-IFN)
cell-mediated immune response
5
5
Basler et al., Proc Natl Acad Sci USA 2000
Basler & Amarasinghe, J Interferon Cytokine Res 2009
Ramanan et al., Viruses 2011
Wei Xu et al., Cell Host & Microbs 2014
4
5
La biologia del virus Ebola
1. Struttura del virione
2. Infezione e replicazione
3. Fattori di virulenza e di evasione dalla
risposta immunitaria
4. Target molecolari per lo sviluppo di farmaci
EboV molecular targets
for the therapy and/or prevention of
Ebola infections
•
•
•
•
•
•
vGlycoprotein GP (adhesion/penetration)
cNPC1 (necessary for uncoating)
vRNApol L (transcription/replication)
VP35 (transcription/replication and IFN inhibition)
VP40 (transport/assembly)
VP24 (assembly and IFN inhibition)
Drugs and vaccines in clinical trials
with support for further development according to the
Centers for Disease Control and Prevention
Animals Healthy
Small group Large group
of patients
Trials
volunteers of patients
ZMapp
GP: triple mAbs cocktail
Brincidofovir
RNA-pol (??): nucleoside analog;
broad spectrum - DNA viruses
TKM-Ebola
RNApol: siRNA
RNApol: nucleoside analog; chain
terminator; anti-Flu approved
Favipiravir
AVI-7537
BCX4430
ChAd3
VSV-EBOV
Approved
for use
VP24: anti-sense oligomer
Drugs
RNApol: nucleoside analogue; broad spectrum - RNA viruses
Vaccines
Kondratowicz & Maury, Future Microbiol 2012
Nature Reviews Drug Discovery 2014
Gao, Drug Discov Ther 2014
Cohen, Science 2014
