5. Intro to Viruses Flashcards
What kind of microscope do you use to see a virus?
Electron
Which virus family does influenza belong to?
Orthomyxovirus
Through which mechanism do retroviruses, such as HIV, spread from one cell to another in an infected host?
Nuclear
Traditionally, which approach was used to detect viruses in specimens from infected patients?
Tissue culture and light microscopy
How are viruses classified?
Phenotype Nucleic acid How they replicate Host Disease
What type of capsid does herpes simplex virus have?
Icosahedral
What is a capsid?
Protein shell made of capsomers
What are the 3 types of capsids?
Icosahedral
Helical
Complex
What is the structure of an icosahedral capsid?
20 equilateral triangles
What type of capsid do coronaviruses have?
Helical
What parts of the virus interact with host cell receptors and contains antigens?
Capsid
Envelope
What are the advantages to capsids?
Resistant to drying, heat, acids, proteases
Survive in GIT and in environment
What are the disadvantages to capsids?
Humoral response may be enough to kill the virus
Needs to kill cells to spread
What is a virus envelope made up of?
Phospholipids and glycoprotein
Taken from host cell membranes
What surface polypeptide helps influenza to bind to sites on the host cell?
Haemaglutinins
What are the disadvantages of envelopes?
Can’t survive in GIT
Need to stay wet in transmission, so spread through large droplets
What are the advantages of envelopes?
Don’t need to kill cells to spread
Need both the humoral and cellular response
What are the methods of virus acquisition?
Vector Inhalation Faecal oral Blood borne Sexual Congenital
What is tropism?
Virus is specific for a certain cell type
What factors influences the tropism of a virus?
Cell receptor Cell transcription factors (recognise viral promoters etc) Ability to support viral replication Physical barriers Environment Digestive enzymes and bile
What are the 5 stages in virus replication?
Adsorption Penetration Uncoating Synthesis and assembly Release
What are the 2 methods of viral penetration?
Internalised via endocytosis
Envelope fuses with membrane
What is the purpose of uncoating?
Makes the virus’s genome available
How does a non-enveloped virus get released?
Lysis or exocytosis
How does an enveloped virus get released?
Budding
What effect do viruses have on host cells?
Cell death
Tranformation to malignant or pre-malignant
Latent infection
What ways can viral infections spread within the body?
Intracellular
Extracellular (blood and lymph)
Neural (PNS to CNS)
Nuclear (virus genome added to host’s)
What 3 ways can viral infections be combatted?
Directly inactivate
Increase host response
Inhibit viral replication
Name a drug that inhibits viral replication
Aciclover
What ways can viruses be identified in culture?
Immunofluorescence
Neutralisation
Haemabsorption inhibition
What does serology test for?
Viral antigens
Antibody produced against viral antigen
What is used to detect viral antibodies?
ELISA
What method can be used to detect resistance to antivirals?
PCR
What is the cytopathic effect?
The way the presence of a virus can be seen in culture
Ballooning or shrivelling of cells
Disruption of cell monolayer
What virus is associated with liver cancer?
Hep B and C
What virus is associated with cervical cancer?
Papillomavirus
What virus is associated with lymphoma and nasopharyngeal cancer?
Epstein Barr
What virus can spread along neurons?
Rabies
What type of virus is hepatitis B?
Hepadna DNA virus
What type of virus is influenza?
Orthomyxo RNA virus
What type of viruses are polio and hepatitis A?
Picorna RNA
What type of virus is HIV?
Retro RNA virus
Name a virus that spreads intracellularly
HSV
Name a virus that spreads extracellularly
Influenza
Name a virus that spreads in neurons
Rabies, HSV
What can be seen in hippocampal cells in rabies?
Negri bodies
