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30 Cards in this Set
- Front
- Back
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Viruses are ... parasites
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obligate intracellular
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Basic composition of viruses:
genomes may be either ... or ... -the DNA genome is ... or ... stranded and is either ... or ... -the RNA genome is ... sense (+) or ... sense (-), ... (+/-) or ... (+ and – RNA portions linked end to end) *(+) strand is equivalent to ... *RNA may exist in ... segments (i.e. influenza) |
DNA or RNA
single or double linear or circular positive negative double-strand ambisense mRNA linear |
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... viruses are environmentally stable and spread through fomites and oral-fecal route
... viruses are environmentally liable and normally spread through secretions and blood |
Capsid
Enveloped |
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What are the 6 stages of the viral replication cycle?
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Early phase
Late phase Infection period Eclipse period Latent period Production period |
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Early phase
... of appropriate target cell, ... to the cell, and ... of the plasma membrane once the virus is taken up by the cell, it must release the genome into the cytoplasm (...) in some instances, the genome must be transferred to the nucleus |
recognition
adhesion penetration uncoating |
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Late phase
genome ... and ... of viral proteins the genomic and protein components are assembled into a viral particle and ... from the cell |
replication
synthesis release |
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Infection period
viral particles are actively ... to and ... target cells accompanied by a ... in the overall concentration of detectable virus |
adhering
penetrating drop |
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Eclipse period
timeframe in between the adherence and penetration of viral particles to the target cells and the appearance of newly assembled ... (noninfectious and infectious) |
virions
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Latent period
period during which no extracellular infectious virus is ... includes the ... period viruses can remain in a latent stage for a few hours to an indefinite amount of time |
detected
eclipse |
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Production period
new viral particles are being produced at a rapid rate -only 1% to 10% of the viral particles are infectious -remaining viral particle are noninfectious or defective particles yield of infectious virus per cell is called the ... |
burst size
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Overview of viral replication:
1. ... of the target cell 2. Attachment 3. Penetration 4. Uncoating 5. Macromolecular synthesis a. Early messenger RNA (mRNA) and nonstructural ...: genes for enzymes and nucleic acid-binding proteins b. ... of genome c. late mRNA and structural ... d. Post-translational ... of protein 6. ... of virus 7. ... of enveloped viruses 8. ... of virus |
Recognition
protein synthesis replication protein synthesis modification Assembly Budding Release |
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Release of the genome
1 and 2. Recognition and attachment ... or other surface structures bind to receptors on the target cells -in capsid viruses, the viral attachment structure is ... of the capsid or a protein that extends from the capsid -in envelope proteins, VAPs are specific ... that bind to cell surface receptors -receptors may be proteins or carbohydrates found on glycoproteins or glycolipids on the cell surface of the target cell viruses bind to target cells with different ... and ... -... is when only certain cell types are susceptible to infection (i.e. only infect B cells) -... means the viral infection is restricted to certain species (i.e. only infect humans) |
viral attachment proteins (VAPs)
part glycoproteins tropism host range tropism host range |
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3. Penetration
interaction between the VAPs or specific viral structures with cell surface receptors leads to the ... of the virus Mechanism of internalization -varies with virion structure and cell type A. Receptor-mediated endocytosis -... viruses -exposure of hydrophobic regions of ... proteins allow the virus or viral genome to translocate across the plasma membrane B. Fusion of viral membranes with the cell membranes -... viruses -fusion of the viral membrane to the cell membrane allowing delivery of the nucleocapsid of genome directly into the cytoplasm -some ... viruses enter cells via endocytosis and fuse with the endosome |
internalization
capsid capsid enveloped enveloped |
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4. Uncoating
once a nucleocapsid is delivered into the cytoplasm, it must be transported to the site of replication and the ... and/or ... removed |
capsid
envelope |
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Synthesis of macromolecules
the ... genome directs the synthesis of viral mRNA, protein and generates identical copies of itself through replication ... genome of DNA viruses and positive-stranded RNA serve as infectious nucleic acids -sufficient to initiate infection cycle |
viral
naked |
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Replication of DNA viruses
occur in the ... require a DNA-dependent DNA polymerase, other enzymes involved in replication and dNTPs supplied by the ... cell |
nucleus
host |
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Replication of RNA viruses
replication and transcription of RNA viruses is similar as the viral genome is either ... stranded RNA (mRNA) or ...-stranded RNA (template for RNA) the viral genome must encode for RNA-dependent RNA polymerases (replicases and transcriptases) -cell cannot replicate ... |
positive
negative RNA |
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Transcription and translation:
Early gene products: transcription of mRNA for ... proteins occurs first -proteins are catalytic and involved in ... -transcribed at ... levels -replication of the genome initiates the transition to the transcription of ... viral genes |
nonstructural
replication low late |
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Late viral genes:
newly replicated genomes provide new templates for more late gene mRNA synthesis encode ... proteins -translated at ... levels -involved in the packaging and assembly of ... -generally not required for ... |
structural
high virions replication |
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Translation of early and late mRNAs:
dependent on host cell ribosomes, tRNAs and the cellular machinery for post-translational modifications most viral mRNAs have a ... and a polyA tail |
5’-cap
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Assembly and release of virions:
Assembly: systematic assembly of non-structural and structural proteins to provide functional packaging of the genome each structure in the virion is composed of ... structures -allow for the appropriate protein-protein, protein-nucleic acid protein-membrane interactions initiated when all viral components are synthesized and the concentration of structural proteins is high enough to drive the process-site and mechanism of virion assembly depends on where the genome is replicated and whether the final structure is a ... or an ... Release: naked capsid viruses are released by ... of the cell; cell dies enveloped viruses are released by ... from the plasma membrane; cell does not die -enveloped that gain their membrane in the cytoplasm remain within the cell and are released by exocytosis or cell lysis |
recognition
naked capsid enveloped virus lysis budding |
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Naked capsid virus
-assembled as a empty structure ... with the genome OR -assembled ... the genome |
filled
around |
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Enveloped virus
delivery of viral glycoproteins to cell surface by ... transport envelope acquired after the assembly of the ... the nucleocapsid associates with the ... where the viral glycoproteins are concentrated -the envelope is associated through the process of ... |
vesicular
nucleocapsid membrane budding |
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Problems viruses must solve:
Ability to ... within host -Copy genetic material and generate the mRNA necessary to produce viral proteins Ability to be ... from one person to another -Exploitation of human behavior to move from one individual to another Ability to evade ... -Develop strategies to elude the host’s antiviral defenses Viruses encode activities (...) that enhance viral replication, transmission and evasion |
replicate
transmitted host defenses virulence factors |
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Outcomes of viral infections:
... infections -kill infected cells ... -caused by the replication of the virus and the accumulation of viral proteins and progeny -disruption of normal cell and lysosome function leading to lysis of the cell ... -caused by the expression of viral antigens on the cell surface and disruption of the cytoskeleton -changes cell surface proteins and cell-to-cell interactions -changes allows for recognition by CTLs ... -induced by the viral infection or cytotoxic immune responses ... or ... infections -infections that are not cleared -infected cell is not killed by virus -virus gently released either by budding or exocytosis ... infection -Mutated viruses that do not replicate |
Lytic
Autolysis Cytolysis Apoptosis Chronic or persistent Abortive |
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2 types of chronic or persistent infections:
1) Latent -virus infects a cell that does not support ... of viral genes -stress or other stimuli lead to the production of ... 2) Transformation or immortalization -infection with ... viruses -establishment of a persistent infection that stimulates uncontrolled cell ... -cells are immortalized a. Activation or introduction of growth stimulating genes (...) b. Removal of tumor ... gene or their products c. Prevention of ... |
transcription
virion oncogenic growth oncogenes suppressor apoptosis |
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... infection
-Initiation of the infection -Development of the disease state -Clearance of the infection ... infection -Initiation of the infection -Development of the disease state -Inability to clear the infection |
Acute
Chronic |
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Steps in viral pathogenesis:
1. Acquisition of ... from another source -entry into the host 2. Initiation of ... at primary site 3. An ... period -virus is replicated at high frequency and may spread to a secondary site 4. ... in target tissue -development of characteristic disease symptoms 5. ... response -limits progression to a disease state OR -contributes to disease state 6. ... -production and release of virus to infect a new host 7. Clearance of infection or establishment of a persistent chronic infection |
contagion
infection incubation Replication Immune Contagion |
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Incubation period:
... viral replication ... if the primary site of infection is the target site -development of characteristic disease symptoms ... if infection must spread to site other than primary site |
active
short longer |
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... -non-specific or flu-like symptoms that precede the characteristic disease symptoms
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Prodrome
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