Term
| Different type of replication patterns |
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Definition
- abortive- no virus production and no effect on host
- lytic- viral production with host cell death (MOST COMMON)
- persistent
- productive- viral production with senescence effect on host cell
- latent- no viral production and no effect on host cell
- transforming
- DNA virus- no viral production with host cell immortality
- RNA virus- viral production with host cell immortality
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Term
| factors that effect viral replication |
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Definition
- host susceptiblities and defenses
- portal of entry
- host range of virus
- cellular permissiveness/host cell functions
- host immune responses
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Term
| Process of lytic infection |
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Definition
- absorption
- penetration
- uncoating
- early transcription
- early translation
- DNA synthesis and late transcription
- late translation
- condensation
- assembly
- release
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Term
| phases of lytic infection |
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Definition
- attachment
- eclipse (while virus replicated, so increase in nucleic acids)
- synthesis (increase in proteins)
- maturation (increase in intracellular virions)
- release (increase in extracellular virions)
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Term
| lytic infection: attachment phase mechanism |
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Definition
- binding to specific receptor define tropism
- receptor is usually a cellular glycoprotein
- virus may bind to more than one receptor
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Term
| lytic infection: entry phase mechanism |
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Definition
- energy dependent
- envelope cell membrane fusion of enveloped viruses
- endocytosis of nonenveloped viruses
- translocation of nonenveloped viruses
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Term
| lytic infection: uncoating/nuclear transport mechanism |
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Definition
- uncoating may be mediated by lysosomes
- nuclear transport of genomes may be mediated by microtubules or other cellular elements
- transport not needed for viruses replicating in cytoplasm (ex: poxvirus)
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Term
| At what point within lytic cycle are viral genes expressed? Effect on viral life cycle? |
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Definition
- after nuclear transport, leading to:
- alteration of host cell function
- preferential viral gene expression
- host cell shutoff
- activation/regulation of viral genes
- viral genome replication
- structural proteins
- genome packaging
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Term
| Role of RNA processing in virus life cycle |
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Definition
| give flexibility in gene expression |
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Term
| phases of viral gene expression |
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Definition
- early (nonstructural) genes (eclipse phase)
- genome replication (eclipse phase)
- late (structural) genes (maturation phase)
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Term
| Function of "early" genes in virus |
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Definition
- turn on virus and turn off cell
- early genes encode
- transcriptional activators
- host shut off/alteration proteins
- DNA replication enzymes
- immunomodulating proteins
- initial gene expression may be self activating
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Term
| role of DNA replication in separating early and late viral phases |
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Definition
- occurs between early and late stages
- usually relies on viral polymerases and host cell components
- energy dependent
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Term
| Function of "late" genes in viruses |
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Definition
- produce new viruses
- encode capsid, assembly, packaging proteins
- produced in much greater quantities via:
- regulation of gene expression
- increased number of viral templates
- host shut off usually complete at this point
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Term
| Mechanism of assembly of new virions |
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Definition
- must happen after structural proteins made
- individual polypeptide subunis assemble into structures of nonidentical subunits
- structure units assmble into symmetrical assembly units
- capsomere - assembly of >1 viral protein
- subunits assemble by noncovalent interactions
- polar (H bonds)
- nonboplar (hydrophobic bonds, van der Waals)
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Term
| Mechanism of viral release |
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Definition
- cell lysis
- release by budding (if enveloped)
- this is how it gets its envelope
- it will go to the portion of membrane that has proteins it needs
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Term
| dsDNA virus mechanism of producing mRNA |
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Definition
- use DNA as template for mRNA and new viral genomes
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Term
| +RNA virus mechanism of producing mRNA and new genomes |
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Definition
- use (-) RNA as template for mRNA and new genomes
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Term
| mechanism of - RNA viruses making mRNA |
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Definition
- use + RNA as mRNA and as template for new genome
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Term
| mechanism of dsRNA viruses making mRNA |
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Definition
- dsRNA use + and - RNA to produce mRNA and new genomes
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Term
| mechanism of retrovirus RNA making mRNA |
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Definition
- use DNA as template to make mRNA and new genomes
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Term
| Role of viruses interacting with other different viruses |
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Definition
- some viruses are dependent on other viruses for replication factors
- ex: Hep D depends on Hep B
- ex: adeno associated viruses depends on adenoviruses
- some viruses can accelerate the growth or disease by other viruses
- ex: HIV + Hep C cause liver damage much quicker
- ex: HIV + HTLV-1
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Term
| patterns of viral infection |
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Definition
- lytic
- latent
- chronic (cause acute infection, but then continues replicating at low and detectable level)
- slow (virus doesnt really cause an acute infection, until replication builds up over years to cause an acute infection)
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Term
| Mechanism of latent infection stoping to multiply after initial infection |
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Definition
- establish latency
- restrcit cytolytic effect
- episome formation
- limitation of viral transcription
- maintenance of latency
- latent protein synthesis
- viral genome replication
- evasion of host immunity
- reactivation of lytic infection
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Term
| Mechanism and examples of latent viruses bing reactivated and causing cancer |
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Definition
- recurrent infection in normal host (HSV)
- immunodeficiency associated infections (HZ, CMV)
- cellular transfomration and tumorigenesis (EBV, HPV)
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Term
| Types of genetic changes involved in viruses |
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Definition
- mutation (change in individual bases)
- recombination (changes in stretches of genome via rearrangements)
- reassortment (changes via mixing of different genome segments)
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Term
| different types of mutations |
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Definition
- physically/chemically defined
- missense (altered protein)
- nonsense (truncated protein)
- deletion/insertion (frameshift mutation)
- biologically defined
- phenotypic (ex: plaque morphology, host range)
- biochemically defined
- revertants
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Term
| mechanism of recombination |
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Definition
- switching of two different strains of genome
- this gives you new viral genomes that are enclosed in capsids
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Term
| mechanism of reassortment |
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Definition
- you end up with some progeny with parental segments and mix of segment of each virus that got in
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Term
| Effect of viral genetic changes |
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Definition
- immunogenic
- antigenic drift- mior antigenic changes from random mutations (ex: influenza A)
- antigenic shift- major antigenic changes uusally from recombination or reassortment leading to pandemics
- pharmacologic (drug R)
- biologic (increase virulence)
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