L31 - Intoduction To Virology Flashcards
What are properties of viruses?
- obligate intracellular
- host specific
- ~smallest biological entities
- genome size 3.2kb (4 genes) to 1.2Mb (911 genes)
What does obligate intracellular mean for the virus?
- can’t grow/replicate outside host
- dont acquire nutrients, produce energy/synthesise proteins
What can viruses be classified on?
- type on nucleic acid
- morphology
- presence/absence envelope
- host organism
What are DNA viruses, RNA viruses and RNA<->DNA viruses classification?
ss or ds (single/double stranded)
What are the structure of viruses?
- naked viruses
- enveloped viruses
What are naked viruses like?
No outer membrane
// polio virus
What are enveloped viruses like?
- outer membrane // herpes simplex virus, SARS_Cov2
-derived from host cell membrane - modified by viral proteins for recognition and attachment to host cells
What do naked virus have, what do enveloped virus have?
Naked - nucleic acid, in capsid
Enveloped - spikes, surrounded membrane over capsid, nucleic acid
What are the steps in viral multiplication?
- attachment of virus
- entry and uncoating (nucleic acid enters)
- replication and synthesis on nucleic acid and proteins
- assembly of virus particles
- release
What is the attachment like?
- virus attach from random collision
- specific interaction between attachment site on viral surface and receptor on cell surface
What is the entry and uncoating like?
- often coupled process
- entry through endocytosis (en and naked virus)
- entry through fusion with membrane (env virus)
- nucleic acid prepared for expression/replication, full or partial shedding of capsid proteins
What is synthesis of viral component like?
- viral nucleic acid competes with host for control of biological machinery
- viral mRNA produced
- mRNA -> synthesis of early proteins
- early proteins -> nucleic acid replication
- synthesis of late proteins
What is assembly like?
Nucleic acid either
- packed into preassembled capsid
- associates with capsid proteins during formation
What is release like?
- cytosis (naked virus)
- budding (env virus, usually derived from plasma membrane)
During release by cytolysis, what is the lawn and plaque?
Lawn - confluent layer of bacteria
Plaque - due to lysis of infected bacteria
What are the outcomes of viral infection?
- cytpcidal infection //polio virus
- chronic infection // hep B virus
- latent infection // HIV
- transforming infections // HPV
What leads to the different outcomes of viral infection?
- acute infection - rapid replication - release and cell death
- latent infection, activation to rapid replication
- chronic infection - slow release, no cell death
- tranformin infection - insertion of oncogene, protooncogene activation
What is the life cycle of HIV?
- fusion of HIV to membrane
- reverse transcriptase of ssRNA
- viral DNA integrated into nucleus
- transcription of mixed DNA
- genomic ssRNA and proteins bud off
What are the different viral vaccines?
- live
- killed
- component
- vector
- mRNA
- DNA
What are live vaccines like?
Usin attenuated strains
What are killed vaccines like?
Viruses killed by heat or chemicals
What are component vaccines like?
- isolated from whole virus particles
- produced by recombinant DNA tech
What are vector vaccines like?
viral vector carrying component from pathogen
What are mRNA vaccines like?
MRNA encoding antigen introduced into tissue
What are DNA vaccines like?
Intro of plasmid encoding antigen into tissue
What are the ways to produce virus particles?
- cell cultures
- embryonated hen’s eggs
What are cell cultures like?
- infect mammalian cell line with virus
- isolate and purify virus particles
What are embryonated hen’s eggs like?
- virus injected into fetrilised chicken eggs
- eggs incubated 2-3 days
- isolate and purify virus particles
