Please enable JavaScript.
Coggle requires JavaScript to display documents.
L13 - Introduction to Viruses
Understand and describe the basic…
L13 - Introduction to Viruses
- Understand and describe the basic components of viral; morphology, structure and taxonomy, and of the prion diseases
- Understand and desribe the major medically important viral disease described in this lecture
- Understand and describe the basic elements of virus evolution
- Understand and describe the basic properties of prions and prion diseases
Notable Viral Disease
-
Influenza Virus
Prolific Mutator
Antigenic shift => Re-assortment of Viral Genomes => Cross-species transmission => Evasive resistant to vaccine eradication
All influezna viruses have AVIAN ORIGINS
All influenza A virus infections begin with birds and human infections are found due to antigenic shift
-
-
SARS-CoV (2002-2003)
=> Novel coronavirus => severe respiratory syndrome
=>Emergent from zoonotic resevoirs - acquire human transmission (pathogenic to humans, yet non-harmful to zoonotic as evolved alongside oneanother
-
MERS-CoV
-
PRIONS
Proteinaceous infectious particles
Responsible for transmission of Spongiform enkephalopathies which are progressive neurodegenerative disorders
-
Pathogensis
Abnormal protein molecules which have been misfolded => sporaidc/spontaneous occurrence=> Transmissable and induce abnormal folding of otherwise normal prion proteins
=> Prions are found aboundantly in the brain
-
-
Viral Morphology
Typical viral particles require E-microscopy to visualise.
1000s < NA Genome < 2.5 mill
Large viral species have been mistaken as bacteria =>Mimivirus => pneumonia causing bacteria
-
Enveloped
Those enveloped Viruses exhibit an added layer of protection, comprised of Carbohydrates, lipids and proteins
Encoded endogenously
Influenza Virus
Acquired from host cell's plasma membrane during extrusion
Helical
Campsomeres organised into helical/spiral structure => NA contained within interior
Ebola virus = helical
-
-
Virus (Latin - poison)
=> Inert elementa which are incapable of replicating outside of a host cell => obligate intracellular parasites
**We in fact carry viral genes embedded within our genome => Endogenous retroviruses => Integrated into DNA => some have physiological roles => most are silent => some may have increased/active expression under certain conditions
-
Host Range
- Refers to the spectrum of host cells which the virus can infect.
- Not restricted to cell types withina single species
- A determinant of viral virulence/pathogenicity
Once Virus has;
- Adhered
- Evaded
- Infected
- Synthesised
- Assembled
=> Extrudes viral progeny
Antigenic Drift/Shift
- prevents the total eradication of virus
- creates problems for antiviral drugs => drug selectively destroys virus with target antigen, suppressing replication of known virus => simultaneously incapable of preventing replication of anitgenic divergents =>* proliferate and new virus emerges*
Viral Structure and Composition
Virion => complete virus particle
- Composed of; proteinaceous coating nucleic acid genome
Nucleic Acid
Single/Double Stranded;
Arranged in linear, or circular arrangement.
May be several separate segments-
-
Capsid
Proteinaceous coating encapsulating viral genome
- Consists of repeated subunits => Campsomere
- Also embeds ligands which bind to host cell
-
-
-
Taxonomy
-
Baltimore classification
Classifies Viral species based on how they synthesis mRNA