Lecture 37 - Virology Intro Flashcards
Do all viruses cause disease? If not, why not?
No - can be avirulent, not in primary host, latent infection, or host mechanisms stop disease symptoms
Define virome
all viruses in given environment (viral biome)
T/F: viruses outnumber bacterua 10:1 in most ecosystems
TRUE
What are the 3 theories of viral origin?
- self-replicating molecules that existed before cells
- evolved from genetic elements within cells that gained the ability to move between cells
- ancient intracellular parasites that lost other functions
what are the reasons that there are new viruses?
- mutations
- zoonoses development
- genetic shift
- recombination events
how do zoonotic viruses like SARS coronavirus spread to humans
- emerge from bats
- go to intermediate species in a new environment
- infect humans in close contact
T/F: mosquitoes are a vector for many viruses
TRUE
what are the ways humans can be infected by zoonotic viruses
- bats to intermediate species
- mosquito-borne
- primates to humans
- food animal-borne
the spread of HIV or ebola virus to humans illustrates what kind of viral spread
between closely related animal species
what is viral genomics teaching us
viruses have always existed but we are recently finding them via technology
why are viruses considered infectious pathogens
- spread to other cells or hosts
- infection alters fundamental cell processes
what are the 4 steps of viral replication
- enter
- replicate
- exit
- spread
what two structures do viruses have that help replication
- nucleic acid genome
- protective coat
what do viruses lack?
- functional ribosomes
- mitochondria
- means to generate metabolic building blocks
how can viruses be categorized
obligatory intracellular parasites
how are progeny viruses created (2 steps)
- synthesize viral components
- assemble
define tropism
restricted site for viral replication
what can viruses infect based on restrictions
- only one kingdom (animal, plants, fungi, Protista, bacteria)
- only one/several animal species
- a limited number of tissues and cell types
to study viruses, what 4 things do we do in a laboratory
- isolate (swabs/sampling)
- amplify
- concentrate
- purify/enrich
what does amplification select for
viral mutant in an unnatural/selective environment
what are the advantages and disadvantages of using laboratory animals for amplification
advantages: natural environment does not select for adaptive mutations
disadvantage: no consent from animal, discomfort
what are the advantages and disadvantages of using embryonated eggs for amplification
advantage: respiratory viruses grow well, sterile environment
disadvantage: most enteric viruses don’t grow in eggs, egg allergy
what are the advantages and disadvantages of using organ cultures for amplification
advantage: grow viruses that don’t grow in cultures
disadvantages: difficult to maintain
what are the advantages and disadvantages of using cell cultures for amplification
advantage: easy to amplify the virus
disadvantage: many viruses don’t grow in cultures, select adaptive mutations
T/F: different viruses mutate at different rates
TRUE
define strain
lines or isolates of the same virus
define type
the same virus expresses different antigens or other molecules on their surface
define variant
virus mutant that differs from wild-type strain in phenotype
deletion or nonsense mutation
results in loss of protein expression needed for viral replication
host range mutation
ability of virus to infect new host cell or species
resistance mutations
virus adapts to antiviral drugs or host defense responses
reverse mutations
virus returns to wild-type once drug or host defense pressure is removed
