Viruses Flashcards
Host cell specificity
- what it is and what determines it (viruses)
Virus interact with one or more host cell molecule/receptor
Spike projections determine where have access to, the cells, which may determine symptoms
Examples of viral host cell specificity
Rabies Influenza HIV Epstein-Barr Human rhinoviruses
Rabies - host cell specificity
Rabies - neuronal cells acetylcholine receptor Neuronal cell adhesion molecule
Influenza - host cell specificity
Influenza - sialic acid receptor on lung epithelial cells and upper respiratory tract
Human rhinoviruses - host cell specificity
Human rhinoviruses - lots of different cells, because general targets
iCAM-1 - intracellular adhesion molecule
VLDL-R = very low density lipoprotein receptor
Differences in viral replication steps between types
DNA viruses use host machinery for translation
RNA viruses
Negative-sense strands must be converted to positive-sense then used as mRNA
Positive-sense strands can be used directly as mRNA
Retro-viruses ssRNA+->ssRNA- ->dsDNA->mRNA
Outcomes of viral host cell infection (with examples)
Lytic - e.g. influenza
Persistent infection - e.g. hep B
Latent infects - e.g. herpes virus
Features of a latent viral infection
Remain in cell cytoplasm (e.g. herpes virus)
Is incorporated into host genome
The 7 Ebola proteins in the Ebola genome
Glycoprotein, part of spike (GP/sGP)
Matrix protein (VP24) - INHIBITS NORMAL ANTIVIRAL RESPONSES (INF-β & INF-INDUCED EXPRESSION OF ALPHA-STAT-1)
Nucleoprotein, associated with RNA genome (NP)
Polymerase cofactor (VP35)
Transcription activator (VP30), encourage transcription of viral RNA over host RNA (preference)
Nucleocapsid proteins (VP30, VP24, VP35)
How many strains of Ebola are there?
5
Lifecycle of the Ebola virus
Attached to TIM-1 (T-cell immunoglobulin and mucin domain 1)
Membrane comes round and wraps up ebola and takes in to cell in endosome
Binding to NPC1 (Niemann-Pick C1, endosomal/lysosomal cholesterol transporter)
Release from endosome, release of capsid into cell
Virion constructed, release from cell through lysis (takes membrane of cell as coating)
Key receptors in Ebola life cycle for targeting
Ebola
TIM-1 (T-cell immunoglobulin and mucin domain 1)
NPC1 (Niemann-Pick C1)
TIM-1
T-cell immunoglobulin and mucin domain 1
NPC1
Ebola
Niemann-Pick C1, endosomal/lysosomal cholesterol transporter
DNA viruses (all icosohedral)
Hepatitis B
Epstein Barr Virus
Poxviruses (inc. smallpox)
Papilloma Virus
RNA viruses (icosahedral)
Rubella
HIV
Norovirus
RNA viruses (helical)
Mumps
Marburg
Influenza
Viral replication steps
Attachment and entry
Uncoating of virion
Migration of genomic nucleic acid to nucleus
Transcription/replication
Biosynthesis
Assembly of virion
Release - some retain parts of host membrane (hiding)
Viral replication
Usually one polycistronic RNA (all open reading frames together) - one mRNA
Use host ribosomes for mRNA-> single large protein THEN cleavage with specific proteases
- Viral capsid
- Polymerase
- Protease - for large protein cleavage
Features of a lytic viral infection
Immune response (sometimes severe)
Features of a persistent viral infection
Slow release of viral particles (under detection levels for immune system of host)
HPV viruses that cause cancer
HPV - 18
HPV - 16
HPV - 45
HPV - 31
Viruses linked with cancers
Hepatitis B Epstein-Barr Herpesvirus HPV Merkel cell polyomavirus Human T-cell leukaemia lymphoma virus
What is Ebola?
Filovirus
single-stranded, negative-sense
19k nucleotides (RNA)
Helical structure
How does Ebola enter the cell?
Niemann-Pick C1 receptor
T-cell immunoglobulin and mucin domain 1 (TIM-1)
What does TIM-1 do?
T-cell immunoglobulin and mucin domain 1 (TIM-1)
Receptor for mucosal surfaces - how Eboli is initially contracted? (hand->eye)
What does NPC1 do?
Niemann-Pick C1 receptor
Access to dendritic and other cells.
How Ebola inhibits viral response?
VP24 (viral protein 24)
-> INF-beta & STAT-1 expression
VP24
Ebola Matrix protein
INHIBITS NORMAL ANTIVIRAL RESPONSES (INF-β & INF-INDUCED EXPRESSION OF ALPHA-STAT-1)
NP
Ebola, Nucleoprotein, associated with RNA genome
VP35
Ebola, Polymerase cofactor
VP30
Ebola, Transcription activator, encourage transcription of viral RNA over host RNA
(preference)
VP30, VP24, VP35
Ebola nucleocapsid proteins
HIV - host cell specificity
CD4
CCR5 or CXCR4 chemokine receptors
Epstein-Barr
C3d recpetor on B cells
What does the Ebola virus seem to affect in particular (cells)?
Immune system
- dendritic cells - high amount of Nieman-Pick C1 receptors
