Term
| What are the basic stages of viral pathogenesis? |
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Definition
1) Entry
2) Primary replication
3) Spread (bloodstream/nervous system)
4) Secondary replication (liver/spleen)
5) Spread to target organs |
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Term
| How does Coronavirus (SARS) gain access to the body? |
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Definition
Alimentary tract; Fecal-Oral
Example of localized acquisition, whether the virus stays where it infects. |
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Term
| Provide an example of localized and system Alimentary tract acquisition of a virus. |
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Definition
Fecal-Oral spread
Local= Corona virus (SARS)
Systemic= **Enterovirus**, Reovirus, Adenovirus |
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Term
| Provide an example of upper-localized, lower-localized and systemic Respiratory tract acquisition of a virus. |
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Definition
Upper-locaized= Rhinovirus and **Influenza**
Lower-localized= RSV and **Influenza**
Systemic= Measles and VZV (chicken pox) |
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Term
| Provide an example of localized and systemic Urogenital tract (Sexual) acquisition of a virus. |
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Definition
Localized= HPV
Systemic= **HIV** and HBV |
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Term
| Provide an example of systemic Eye acquisition of a virus. |
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Definition
| **Enterovirus**, Adenovirus |
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Term
| Which viruses are acquired through contact with an insect vector or animal bite? |
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Definition
1) Rabies (nonsegmented, ssRNA (-))
2) Bunyavirus (segmented, ssRNA (-))- Hantavirus
3) Togavirus (enveloped, ssRNA (+))- Rubella
4) Flavivirus (enveloped, ssRNA (+))- West Nile/ Dengue |
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Term
Where are each of the following viruses restricted to:
1) Rhinovirus
2) Parainfluenza
3) Influenza |
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Definition
1) Upper respiratory tract
2) everywhere
3) everywhere, but more in bronchial |
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Term
| What are 3 factors that affect dissemination? |
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Definition
1) Portal of entry
2) Host immunity
3) Cell-specific virus receptors |
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Term
| Explain how viral tropism is determined in HIV-1, Influenza and Poliovirus. |
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Definition
1) HIV-1 binds CDR (receptor) and CCR5/CXCR4 (co-receptor)
2) Influenza binds sialic acid (recptor) and CLRs (co-receptors)
3) Poliovirus binds Pvr (receptor) |
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Term
| What are 4 types of cell dysfunction/morphology change that can occur upon viral infection? |
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Definition
1) Hyperplasia (HPV warts)
2) Mucous secretion (colds from rhino- and coronaviruses)
3) SYNCITIA (multi-nucleated giant cells in HSV)
4) Inclusion body formation |
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Term
| What viruses can cause cancerous transformation? |
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Definition
1) HTLV-1
2) EBV
3) HPV-16/18 |
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Term
| Which viruses can be diagnosed with a Plaque assay? |
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Definition
Measures virus titer an involves cellular lysis.
1) HSV
2) Adenovirus |
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Term
| Which viruses can be diagnosed with a focus forming assay? |
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Definition
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Term
| What are cytopathic effects that could be detected by CPE? |
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Definition
| Rounding of cells and Syncytia formation |
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Term
| How can you detect virus particles or virion components in a sample? |
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Definition
1) light microscope of morphology
2) IF for viral antigens
3) EM for viral particles
4) Hemmaglutination assay for RBC lysis
5) ELISA (indirect) |
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Term
| How can you detect antibodies made against viruses that circulate in the serum (Serology)? |
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Definition
1) ELISA for antibodies against viral antigens
2) Virus neutralization |
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Term
| What does the IgM:IgG ratio tell you about a viral life cycle? |
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Definition
- Early IgG response indicates that the viral antigens have been seen before
- A higher ratio means that it is likely a secondary response |
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Term
| Which viruses involve acute infection followed by death of host? |
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Definition
1) Ebola
2) Hantavirus (Bunyavirus) |
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Term
| Which viruses involve acute infection followed by clearance? |
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Definition
1) Rhinovirus
2) Rotavirus
3) Influenza |
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Term
| Which viruses involve persistent chronic infections? |
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Definition
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Term
| Which viruses involve later infections and reactivation? |
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Definition
1) HIV
2) HSV
3) VZV (chicken pox and shingles)
4) EBV |
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Term
| Explain the molecular life cycle of a Enterovirus infection (Picornavirus family). |
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Definition
Small, unenveloped, ssRNA (+) virus spread by oral-fecal route.
1) Binds to Poliovirus receptor (Pvr)
2) Endocytosis with conformational changes in VP1 and VP4 resulting in fusion.
3) Uncoating at low pH in endosome causes release of ssRNA
4) Replication in cytoplasm, assembly and egression. |
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Term
| What virulence factors are associated with Enterovirus? |
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Definition
1) CNS spreading
2) Survival in acidic environment (stomach)
3) 2A protein inhibits eIF4G and protein translation
4) 2BC/3A proteins inhibit cell secretory pathway (IL-6 ect)
5) 3C protease cleaves Tbp subunit of TFIId, so not TATA-binding can take place. |
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Term
| How does an Enterovirus spread? |
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Definition
1) Enters GI (fecal:oral) and spreads to LN in small intestine
2) Primary Replication in LN leads to fever, GI symptoms (90% asymptomatic but STILL infectious)
3) Spread through blood to liver/spleen (1% to CNS b/c of antibody response)
4) If it gets to the brain, it can cause Meningitis (fever, headache, over in 2 weeks) and Paralytic poliomyelitis (acute, flacid paralysis) |
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Term
| How would you diagnose a case of Poliomyelitis? |
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Definition
Remember, this is very rare (1/20,000) in a Enterovirus infection that has spread to the CNS.
Tissue culture from stool sample and CSF |
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Term
| What is the difference between the Salk and Sabin Polio vaccines? |
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Definition
Salk- IPV that treats CNS but not GI
Sabin- OPV that also takes care of gut. |
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Term
| What is Pleconaril used for? |
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Definition
| Antiviral drug used against enteroviruses and other picornaviruses such as Polio. |
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Term
| Explain how latent/chronic viral infections occur. |
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Definition
Example is HIV, with Wedge-shaped nucleocapsid core containing 5-10 copies of RT and IN
1) During latency, NO infectious virus is produced
2) Can undergo reactivation in response to stress, cellular injury or cell-type permissive for replication |
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Term
| How is HIV an example of a latent/chronic viral infection? |
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Definition
Background- Wedge-shaped nucleocapsid core containing 5-10 copies of RT and IN
- Virion-associated RT converts linear ssRNA to circular dsDNA, which is integrated into the nuclear.
1) TAT interacts with HIV LTR promoter to produce RNAPII (regulatory protein)
2) REV controls late-gene expression (structural) by binding to cis sequence in RNA and controlling RNA splicing (un-spliced and singly-spliced)
3) Assembly and egress occur in cytoplasm or at cell surface. |
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Term
| Distinguish between Antigenic Drift and Antigenic Shift. |
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Definition
Drift= subtle changes from point mutations
Shift= Dramatic changes from reassortment b/w segmented RNA genomes (influenza)
** remember, reassortment involves exchange of any number of the 8 viral proteins in influenza A with those in influenza B particle) |
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Term
| Which virus is most commonly associated with syncitia formation? |
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Definition
| Multi-nucleated giant cells in HSV |
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Term
| What is the sole reservoir for Polio virus? |
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Definition
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Term
| How are the gp120 (SU) and gp41 (TM) glycoproteins produced during HIV replication? |
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Definition
Protease cleaves itself and other products from GAG-POL (Pr160)
1) Protease cleaves Pr55 into MA, CA and NC, producing a nucleocapsid core.
2) Protease cleaves ENV precursor protein into SU and TM |
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Term
| What are the 3 primary mechanisms of viral adaptation? |
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Definition
1) Point Mutations
2) Recombination between related viral strains (pass on mutations)
3) Reassortment of viral genes (segmented RNA genomes) |
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