Virology Flashcards
What are viruses?
Obligate intracellular parasites that require another living cell to infect to replicate within
What is the structure of viruses?
Helical, symmetrical around central axis
Icosahedral, made up of capsomeres
What are the classifications of viruses?
Segmented/non-segmented
Genome linear/circular
Single stranded/double stranded
What are the modes of transmission?
Air borne
Faeces-oral
Bodily fluids
Vectors
What are the steps of replication?
Attachment
Penetration
Uncoating
Replication
Assembly
Release
Explain uncoating
pH/enzyme action change
Explain replication
Nucleic acid and protein synthesis
What are the steps of viral replication (entry and exit)?
Invade host - entry
Vertical transmission
Protein on virus that binds to EXC receptors
Localised infection
Haematogenous/neural spread
Host cell proteases - exit
Explain latency and reactivation
Viral nucleic acid -> pathogenic genes supressed -> genes transcribed and translated -> pathogenic infection -> disease
What are the common pathogens?
Blood borne pathogens
Respiratory tract infections
Skin infections
GI infections
STI
Hospital acquired infections
Vector borne pathogens
Explain influenza
Lipid envelope
segmented (-)sense single strand RNA
Why is HA1 important of influenza virus haemagglutinin?
Important for receptor binding site
Mutations may alter receptor binding
Why is HA2 important of influenza virus haemagglutinin?
Anchor function
Forms stalk
Why is the NA tetramer important?
Important in releasing the virus from host cell
What does oseltamivir target?
neuraminidase protein
What does neuraminic (sialic) acid do?
Allows influenza to bind to multiple cell types
What does the M2 ion channel do?
Allow influx of protons during replication
What does M1 ion channel do?
Beneath lipid membrane and stabilises structure
What is the pathogenesis of influenza?
Air-borne
Destroys cilia
Explain the pathogenesis of influenza
Upper RT replication of virus
immune system response triggered by vRNA recognition
Pattern recognition receptors (PRRs) stimulate cytokine and chemokine production
What are the two immune responses for influenza?
Humoral immunity: effective antibody production helps clear infection by neutralisation (IgA)
Cell mediated immunity: cytotoxic T cells, alveolar macrophages
What are the genetic variations of influenza?
RNA virus
Segmented genome
Reassortment RNA genome
Antigenic shift vs antigenic drift
What is antigenic shift?
Gradual mutation in genes
What is antigenic drift?
Sudden change in genes, creating new strains
