L35 - intro to virology Flashcards
outlines
- principles of virus structure and classification
- different stages and outcome of viruses
- life cycle of HIV
- basics of viral vaccines
properties of viruses
- obligate intracellular
- host specific
- one of the smallest biology entities (30-400nm)
- genome size varies from 3.2kb (4 genes) to 1.2Mb (911 genes)
what does it mean by viruses are obligate intracellular?
- can’t grow or replicate outside host (can’t live on their own)
- don’t acquire nutrients, produce energy or synthesise proteins
how are viruses classified?
- type of nucleic acid
- morphology
- presence/ absence envelope
- host organism
viral genomes of DNA viruses
- ssDNA
- dsDNA
viral genomes of RNA viruses
- single stranged
- double stranded
viral genomes of RNA <–> DNA viruses
- single stranded
- double stranded
structure of naked viruses
- no outer membrane e.g polio virus
- very simple
- shell of protein filled with nucleic acid
structure of enveloped viruses
- outer membrane
- derived from host cell membrane
- modified with viral proteins for recognition and attachment to host cells
stages of viral multiplication
- attachment
- entry and uncoating
- synthesis of viral components
- assembly
- release
attachment stage of viral multiplication
- viruses are not motile
- initial contact from random collision
- followed by specific interaction between attachment site on viral surface and receptor on cell surface
- SARS-Cov2 - ACE2 receptor on eptithelial cells
entry and unceasing stage of viral multiplication
- coupled process often
- entry through endocytosis (enveloped + naked virus)
- end-some formed and sent to lysosomes to dispose
- entry through fusion with membrane (enveloped)
- after entry of nucleic acid is prepared for expression/ replication: full or partial shedding of capsid proteins (uncoating)
synthesis of viral components stage of viral multiplication
- viral nucleic acid competes with host cell for control of biological machinery
- viral mRNA produced
- mRNA directs synthesis of early proteins
- these proteins direct nucleic acid replication
- synthesis of late proteins
assembly stage of viral multiplication
nucleic acid is either
1. packaged into preassembled capsid
2. associated with capsid proteins during formation
release stage of viral multiplication
- cytolysis: naked viruses
- budding: enveloped, developed derived from plasma memb
how are viruses released by cytolysis?
release by budding
- virus makes contact with memb
- memb wraps around virus
- piches off
- releases fully formed virus particle
- memb is modified with viral proteins
outcomes of viral infection
- cytocidal infection (acute infections that lead to lots of cells death)
- chronic infections (slow cell death)
- latent infection (infection has no symptoms for a while, something triggers it)
- transforming infections (cancers)
live vaccines
- using attenuated (weak, normal viruses) strains
- can replicate
killed vaccines
viruses killed by heat or chemicals
component vaccines
- isolated from whole virus particles
- produced by recombinant DNA technology
vector vaccines
viral vector carrying component from pathogen
mRNA vaccines
mRNA encoding antigen introduced into tissue
DNA tissue
introduction of plasmid encoding antigen into tissue
production of virus particles
- cell cultures
- embryonate hen eggs
production of viruses via cell cultures
- infect mammalian cell line with virus
- isolate and purify virus particles
