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84 Cards in this Set
- Front
- Back
Viruses are classified based on what?
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-Genome structure (DNA/RNA, single/double)
-Viral envelope (absence/presence) -Virus particle shape (capsomere morphologic unit of capsid & protomer structural subunit of capsomere) (virus= nucleid acid + capsid protein)* |
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Viral shape is determined by symmetrical _________ arrangement. What are the possible shapes?
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capside (w/ capsomere units)
-isometrical (spherical) -helical (cylindrical) -complex (may have spherical head & cylindrical body) (most medically sig. viruses are isometric (w/ icosahedral (5 protomer subunits) or helical) |
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ALL viral envelopes are produced from host cytoplasmic membrane, EXCEPT ___________
What is this viral envelope made from? |
Herpes
-made from host nuclear membrane (envelope = lipid bilayer= host membrane protein + viral glycolipid) (virus may also lack envelope= 'naked' virus) |
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Viruses may also have ____________ on envelope or on capsid (if "naked"), for host attachment.
If the virus doesn't have these, how does it act on host? |
spike protein
may fuse to host instead & insert viral DNA (cell-membrane-fusion) |
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Viruses usually have species-specific or even tissue-specific (lung, etc) host ranges. Some however may have a wider host range.
Give an example of this |
H1N1 (influenze virus)
swine, bird, & human flu (^mosaic virus bc it has parts from each organism) |
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3 possible outcomes of viral infection
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1. acute/lytic infection= host manifests disease (virion release & cell lysis) & dies
2. chronic/persistent infection= host manifests disease (viron release w/o lysis) & host survives (may be asymptomatic or relapse later) 3. latent/nonproductive infection= host does not manifest upon infection (virus becomes part of host DNA, may reactivate later or remain asymptomatic) (ex:herpes simplex) |
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Differentiate btwn virulent & temperate virus
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virulent (lytic) virus- enter host, cause acute productive infection (reproduce) (then go to another host & repeat)
temperate virus- enter host, may become lytic/produce infection (at any point) OR may establish non-productive relationship (latent do not infect) |
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Why can't viruses be eliminated by filtration?
How can they be eliminated? |
too small
eliminated by; 1. chemicals (destroy envelope), 2. UV (kills), 3. heat (denature capsid/nucleic acid, >90 C) |
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Viral genomes may be arranged in _ or _ form
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linear or circular
(either RNA or DNA, not both) |
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Retroviruses, such as HIV carry what type of genome?
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Diploid genome
2 identical copies of its genome |
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DNA viruses are usually double stranded with the exception of _
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parvoviruses
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RNA viruses are usually single stranded with the exception of _
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REOviridae family
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Reoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some human relevant examples? |
dsRNA (10-12 segments)
Naked ROTAvirus (#1 cause of infantile water diarhea), Colorado tick fever virus, & reovirus |
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Viruses w/ single stranded RNA genomes may have (+) sense/polarity or (-) polarity nucleic acid. What is the difference?
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(+) sense: can use viral RNA directly as mRNA for translation (reproduction)
(-) sense: must transfer RNA to complementary (+) sense, then to mRNA (DNA viruses usually a combination of +/-) |
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The Coding Strand (+) is always read in the _' to _' direction.
The non coding strand (-) is always read in the _' to _' direction. |
5' to 3'
3' to 5' |
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List the 7 (+) sense ssRNA families
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Call Henry Pico-Flow To Come Right away-->
Call= Calicivirdae Henry= Hepevirdae Pico= Picornaevirdae Flow= Flaviviridae To= Togaviradae Come= Coronaviridae Right Away= RETROviridae |
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4 Common Characteristics of (+) sense ssRNA
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1. replicate in cytoplasm
2. do not have enzymes 3. icosahedral shape 4. enveloped (some exceptions) |
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Exception-
Which (+) ssRNA families are naked ? *MOST are enveloped |
(Call Henry Pico-)
Caliciviridae Hepeviridae Picornaeviridae |
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Exception-
Which (+) ssRNA are NOT icosahedral? What shape? |
(come)
Coronaviridae helical (all (-) sense ssRNA are helical) |
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Exception-
Which (+) ssRNA does NOT replicate in the cytoplasm? Where does it replicate? |
RETROviridae
replicates in nucleus |
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Exception-
Which (+) ssRNA DOES carry enzyme? Why? |
RETROviridae
retroviruses do reverse transcription (RNA->DNA), need reverse transcriptase to do this (all other (+) ssRNA do NOT need enzymes bc they can be used directly as mRNA w/o conversion/rxn) |
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(call) Caliciviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(+) ssRNA genome
No envelope (Naked) Human relevant viruses: -Norwalk agent/Noroviruses (causes 2/3 nonbacterial watery diarrhea in adults) -Hepatitis E virus (fatal in preg) |
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(Pico-) Picornaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(+) ssRNA genome
No envelope (Naked) Human relevant viruses: -Hepatitis A -Rhinovirus (common cold) -Enteric viruses: Poliovirus (paralysis), Coxsackievirus, & Echovirus (enter through GI, but effect other systems) -Enterovirus |
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(-Flow) Flaviviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(+) ssRNA genome
Enveloped Human relevant viruses: Hepatitis C |
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(To) Togaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(+) ssRNA genome
Enveloped Human relevant viruses: Rubella virus (german measles, can cross placenta) |
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(Come) Coronaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
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(+) ssRNA genome
Enveloped *also Helical (w/ crown shaped surface proteins) Human relevant viruses: SARS coronavirus (flu-like symptoms) |
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(Right away) RETROviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(+) ssRNA genome, diploid*
Enveloped *also replicates in nucleus & carries enzyme Human relevant viruses: -HIV-I, HIV-II (from Lentivirus genus, non-oncogenic) -HTLV-I, HTLV-II (oncogenic, cause I-T cell, 2- B-cell leukemia) |
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List the 6 (-) sense ssRNA families
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Pain Results From Our Bunion Always
Pain= Paramyxoviridae Results= Rhabdoviridae From= Filoviridae Our= Orthomyxoviridae Bunion= Bunyaviridae Always= Arenaviridae |
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4 Common Characteristics of (-) sense ssRNA
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1. Replicate in cytoplasm
2. Carry Enzymes 3. Helical shape 4. Enveloped |
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Exception-
Which (-) ssRNA replicates in BOTH the cytoplasm & the cell nucleus? |
Orthomyxoviridae (influenze virus)
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(Pain) Paramyxoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
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(-) ssRNA genome
Enveloped Human relevant viruses: Parainfluenza virus Respiratory syncytial virus (Croop) Newcastle disease virus Mumps virus Rubeola (measles) virus |
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(Results) Rhabdoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
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(-) ssRNA genome
Enveloped Human relevant viruses: Rabies virus (life-threatening) |
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(From) Filoviredae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(-) ssRNA
Enveloped Human relevant viruses: -Ebola virus (causes high fever, encephalitis, fatal) -Marburg Virus |
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(Our) Orthomyxoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(-) ssRNA genome
8 segments Enveloped *replicates in BOTH cytoplasm & nucleus Human relevant viruses: Influenza A (multi-species, H1N1), B (human), and C (non-virulent) viruses |
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(Bunion) Bunyaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(-) ssRNA genome
3 circular (?) segments Enveloped Human relevant viruses: (most zoonotic) Hantavirus (causes Hantavirus pulmonary syndrome) |
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(Always) Arenaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(-) ssRNA genome
2 segments Enveloped Human relevant viruses: -Lymphocytic choriomeningitis virus -Lassa fever virus (both cause encephalitis) |
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List the 6 DNA viral families
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Parden Papa As He Has Pox
Parden= Parvoviridae Papa= Papoviridae As= Adenoviridae He= Hepadnaviridae Has= Herpesviridae Pox= Poxviridae |
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What are the 4 common characteristics for DNA viruses
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1. double stranded
2. replicate in nucleus 3. Enveloped 4. Do NOT carry enzymes |
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Exception-
Which DNA viral families are "naked" |
(Parden Papa As)
Parvoviridae, Papoviridae (papilloma), Adenoviridae |
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Exception-
Which DNA viral family does NOT replicate in the nucleus? |
Poxaviridae
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Exception-
Which viral DNA families carry enxymes? (most DONT) |
Hepadnaviridae & Poxaviridae
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(Parden) Parvoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
(+ or -) ssDNA genome
No envelope (Naked) Human relevant viruses: Parvovirus B19 (anemia) (causes Slapcheck fever) |
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(Papa) Papovaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
dsDNA genome
*circular No envelope (Naked) Human relevant viruses: -Human papillomavirus (HPV) (cervial cancer) -JC virus (PMI in AIDs pt) -BK virus (kidney disease in AIDs pt) |
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(As) Adenoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
dsDNA genome
No envelope (Naked) Human relevant viruses: Human adenoviruses (common cold or malignancy) |
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(He) Hepadnaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
dsDNA genome
*Gapped circle (incomplete dsDNA) Enveloped Human relevant viruses: Hepatitis B virus |
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(Has) Herpesviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
dsDNA genome
Enveloped (from host nuclear membrane*) Human relevant viruses: -Herpes -Epstein-Barr virus (mono & cancer) -Cytomegalovirus -Varicella-Zoster (chicken pox-->shingles) |
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(Pox) Poxviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).
What are some examples? |
dsDNA genome
*Dual Enveloped Human relevant viruses: Variola virus (smallpox- irradicated) |
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Common Respiratory (transmitted) viruses
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Influenze (orthomyxoviridae), rhinoviruses
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Common Enteric (transmitted) viruses
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Enteroviruses (polio, coxsacki B), rotaviruses (diarhea)
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Epstein Bar uses _ & _ receptor for attachment
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CR2 & CD21 (on B cell)
causes B cell lymphoma) |
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Rabies virus uses _ receptor for attachment
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Nicotinic acetocholine receptor (neuromuscular jxn)
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Rhinovirus uses ___ receptor for attachment
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ICAM1 (adhesion molecule)
(rhinovirus is #1 cause of common cold) |
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HIV uses ____ receptor for attachment
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CD4
& CXCR$ & CCR5 coreceptors |
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What are the 2 mechanisms of enveloped animal virus entry to host cell?
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1. Direct membrane fusion
2. Receptor-mediated endocytosis (viropexis) (both begin w/ virus envelope spikes attaching to specific receptors on host cell) |
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__________ involves viral envelope fusion w/ & incorporation into host cell membrane, nucleocapsid is released into host cell, nucleic acid separates from capsid (uncoating)
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Direct membrane Fusion
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_________ involves host plasma membrane surrounding virus & forming vesicle, vesicle endocytosed, viral envelope fuses w/ plasma membrane allowing nucleocapsid to be released from endosomal vesicle, uncoating occurs
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Receptor-mediated endocytosis (viropexis)
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What is the mechanism for naked animal virus entry into host cell?
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Receptor-mediated endocytosis (viropexis)
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How does viropexis differ for naked animal viruses?
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lack of envelop prevents nucleocapsid release from endosomal vesical using membrane fusion
(some naked animal viruses use other mechanisms besides fusion to release nucleic acid from endosome, lysis, etc)* |
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Most RNA viruses use the _ as the site of replication and transcription
What is the exception? |
cytoplasm
Orthomyxoviruses and Retroviruses |
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All DNA viruses, except Pox viruses use the _ as the site of replication and transcription
How do they get to the site of replication? |
nucleus
(Pox replicates in cytoplasm) pilot proteins accompany & translocate (phage) viral genome to nucleus |
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All viruses (RNA & DNA) need to _________ before replication (via polymerase) may occur
How does this differ for large & small viruses? |
uncoat (separate nuc. acid from capsid protein coat)
large- uncoat, then enter nucleus to replicate (herpes, adeno) small- enter nucleus, then uncoat (parvo, papo) |
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When in the cell cycle is cellular DNA polymerase expressed?
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S phase (in nucleus)
*The viruses that use cellular DNA polymerase have mechanisms to force the cell into its cell cycle, therefore expressing the DNA polymerase |
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When in the cell cycle is RNA polymerase expressed?
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NEVER
RNA viruses must code for RNA polymerase (transcriptase) & RNA dependent RNA polymerase (replicase), host cells don't have these in cytoplasm |
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What type of virus relies completely on host cell enzymes for mRNA synthesis?
(does NOT use viral enzymes to synth mRNA ) |
DNA
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(+) RNA viruses can directly translate into a single polypeptide (w/o enzyme). Why?
What happens to this polypeptide/polyprotein? |
because (+) RNA can be used as mRNA & translated directly into proteins
Polypeptide cleaved into RNA polymerase (replicase), protease, & viral structural components |
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RNA polymerase (replicase) (produced via cleavage) copies (+) sense RNA into ___________________
Then what? |
complementary (-) sense RNA
this (-) sense RNA serves as a template for new (+) sense strands |
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What is the fate of the new (+) sense RNA?
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3 options;
1. used as template to make more (-) strands 2. package into new virions 3. translated into another polyprotein** |
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New (-) sense RNA can be acted on by RNA polymerase (transcriptase) & translated into _____
OR by RNA polymerase (replicase) & copied into _____ |
(+) mRNA**
(+) sense RNA (can also be packaged into virions) |
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How is retrovirus (HIV) RNA virus replicated?
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-reverse transcriptase converts ssRNA to dsDNA
-host integrates viral nucleic acid into host genome -creating provirus -host cell replicates genomic & viral nucleic acid -protease cleaves polyprotein into capsid, envelope spikes & reverse transcriptase enzyme -components reassemble as new virus particle |
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How are new viruses assembled?
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-scaffolding proteins reassemble proteins into capsid, proteins release after capsid formation
-concatemers thread nucleic acid into empty capsid |
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How are new virus particles released from host?
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naked viruses- released via lysis, leads to host death
enveloped virus- released by budding, virus evaginates host & becomes enveloped during exocytosis, host lives (except- Poxvirus, not released by budding) |
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What is antigenic drift?
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genetic mutation of influenza virus changes antigenic structure on envelop protein
(host antibodies will no longer match virus antigen= new infection by mutated strain) |
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What is antigenic shift?
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host infected w/ 2 diff viral strains, genetic reassortment of 2 segmented genomes occurs, recombinent progeny is an entirely diff virus (than 2 parent strains)
(only occurs in segmented virus, orthomyxo or reo) |
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What is phenotypic mixing
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Host cell contains 2 diff viruses, during replication, protein coat nucleic acid is exchanged, new virus has protein coat w/ unique surface proteins, allowing it to act on different hosts
(viral surface proteins attach to specific host membrane receptors*) |
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Some viruses (particularly retrovirus (HTLV), adenovirus, herpes) can cause malignant transformation in host cells. What does this mean?
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Host cell morphology is altered
grows indefinately due to lost regulation of cell replication (transformation induced via viral oncogenes) |
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What RNA retrovirus induces malignancy?
What kind of tumor does it cause? |
HTLV1- T cell leukemia
(HTLV2 induces B cell leukemia) |
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Which 2 DNA viruses cause hepatocellular carcinoma?
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Heptatitis B & C
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What DNA virus leads to Burkit's or B cell lymphoma
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Epstein-Bar
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What DNA virus leads to Kaposi's sarcoma?
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Herpes 8
(HPV is a DNA virus, causes cervical cancer) |
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What are three reasons a virus would shut down the host protein synthesis?
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More protein synthesis machinery available for production of viral proteins
Blocks cell presentation of viral proteins to immune system Blocks production of anti-viral proteins |
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Innate Immune response to virus:
Alpha & beta interferons are found in are released from virally infected cell, what is their mechanism of action? |
stimulate NK
NK leads to antiviral response in entire area, release IFN-gamma enhancing T cell response, & directly kill infected cells |
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What is the humoral & cellular adaptive immune responses to viral infection?
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humoral- neutralize antiviral antibodies
cellular- virus specific CTL (kill infected cells) |
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There are 2 lines of Anti-HIV drugs. How does the first line work?
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targets reverse transcriptase & protease enzymes in attempt to inhibit viral replication
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How does the second line work?
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targest integrase (enzyme) & CCR5 (receptor) prevent viral uptake into new host cells
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