Animal viruses Flashcards
what are the characteristics of all viruses?
describe further the following elements of the virion:
genome capsid enzymes matrix envelope membrane
what is a virion?
de novo- built from scratch no cellular components no homeostasis can't be cultured require host
genome- encodes functions to replicate
capsid- either be 100% protein coat in repetitive pattern or nucleocapsid = combo of NA and capsid
enzymes- polymerases, integrases, proteases
marix- layer between capsid & envelope
membrane- phospholipid bilayer taken by host cell membrane for easy host entry & exit- virions without = naked
extracellular form of virus so can travel from 1 host to another
can a virus have both DNA and RNA?
what can genomes be;
what NA do you need to make + mRNA?
Class I is dsDNA ± ; how can you make mRNA?
Class II is ssDNA +: how transcribe mRNA?
Class III is dsRNA ±: how?
Class IV is ssRNA +
Class V is ssRNA -
Class VI is ssRNA + retrovirus
Class VII is dsDNA ± retrovirus
yes but only one type is present at a given time
+ or -
single or double strand
circular, linear, segmented
DNA or RNA
single stranded - DNA
mechanism is same- transcription of minus DNA strand
form complimentary -DNA strand to form + mRNA
already has + RNA - use directly
use directly as mRNA
synthesise + complementary RNA strand into -DNA strand then for + mRNA
reverse transcribe then transcribe -DNA into +mRNA
reverse transcribe & use ssRNA RNA intermediate as a template to make single strand DNA to make double strand DNA in host
What are the 2 types of viral symmetry with enveloped virions?
What are the 5 steps to a virion life cycle?
which steps don’t involve energy from ATP?
what are the 4 phases of virus replication?
Helical/rod subunits = capsomere- length virus determined by length of NA
Isometric/spherical = icosahderal symmetry
- bind host cell with virus attachment proteins = irreversible wiht electrostatic interactions
- pentration virus- entire virion fuses with membrane & is uncoated
- viral genome transcripted/translated: DNA enters nucleus & RNA converted into DNA by enzymes in capsid
- virus progeny forms with NA & proteins- used as template further synthesis
- release new viral particles & exit cell by using host membrane as envelope
3 4 5
- eclipse = translation viral proteins- linear kinetics
- maturation = packaging NA & proteins but viruses aren’t yet detected
- latent period
- release: cell lysis/budding - exponential kinetics
what are the 5 typical stages of viral INFECTION?
what are the 2 types of viral infections?
- infection- colonises host
- incubation- time between infection & symptoms
- acute- disease at height (cells lysed & virions infect other cells)
- decline- disease symptoms subsiding
- convalescent- patient returns normal
non permissive = virus not allowed cell entry
permissive = virus gains cell entry
what are the 4 types of permissive infection?
- acute- virus replicates & release progeny & host either clears it or dies
- persistent/chronic- primary infection not cleared so remains producing virions without excessive damage - eventually cleared
- latent- virus present in cells for life & eventually leads cell lysis & acute
- transformation- viral agent causes tumours
- abortive- virus enter cells but can’t replicate
what is a reservoir?
what is a carrier?
what is antigenic drift?
what is antigenic shift?
is there eventually immunity?
what is the difference between incidence & prevalence?
population which infectious agents remain viable
individual that is pathogen infected who is asymptomatic in incubation period
mutations to original viral strain leading to new strain & as a result viral proteins- effects vaccines
2+ viral strains infect host & combine & reassort genome to form new virus
yes- co adaptation & co evolution
incidence = number new cases in given time so the risk individual becomes infected at given time
prevalence = number of existing & new cases in population- depends on new cases, recovery speed, deaths
how can you break the chain of transmission? (5)
what is innate immunity?
adaptive?
what are the 2 ways of passive immunity?
what is the difference between conventional & newly developed active immunity?
avoid contract with reservoir & eradicate vectors report new cases masks vaccination herd immunity
non-specific- skin, mucus, phagocytosis
acquired immunity in vertebrates- T & B lymphocytes
natural = across placenta artificial = made in lab/transferred from people
conventional = forms of the virus used
newly developed = recombinant viral particles or nucleic acid
what are live attenuated viral vaccines?
what are the pros?
cons?
inactivated viral vaccines?
pros?
viral sub units?
pros?
cons?
using whole viruses weakened- infect & replicate & cause mild-no disease
life long immunity
could revert to morphogenic form- not good for those with weak immune system
made from killed viral agents
can’t cause disease/don’t replicate, safe
antigenic part of viral agent
don’t cause disease, safe
difficult produce & induce immune response & memory
what is recombinant vaccine?
viral vector?
mRNA vaccines?
what do antiviral drugs do?
small piece DNA taken from virus & inserted into manufacturing cells to produce surface protein- purified & used
modified & weakened virus to instruct cell to produce viral antigen for strong T & B cell response
mRNA inside host cells & use protein needed for immunity (antibodies)
often inhibit particular processes of the virus
