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MGY378 Exam Study Guide
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MGY378 Exam Study GuideVirus definition - Answer - multiply only in living cells
- obligate parasites (that are metabolically inert when outside their hosts
- rely to varying extents of hosts' metabolism to reproduce
- induced diseases are interactions between virus and host, and host response to virus
Viroids - Answer circular single stranded RNAs of plants; naked RNA is infectious and
transmitted by entry into plant wounds
Prions - Answer misfolded protein of natural host protein. normally expressed in
nervous system of host
pandora virus - Answer - infects amoebas, 2.4Mbp, encodes >2000 proteins, 1uM in size
- encodes proteins for metabolic processes suggests it is evolving into a self-replicating
life form
composition of virus - Answer 1. Genome: single stranded or double stranded; DNA or
RNA; negative or positive sense
2. Capsid: genome encased in protein shell made up of capsomeres
3. Naked or enveloped (lipid bilayer). Enveloped viruses contain virus-encoded
glycoproteins which mediate binding and entry
4. Enzymes essential for replication
Positive sense - Answer can be directly translated to make protein
Negative sense - Answer must be first transcribed to produce positive sense RNA
before undergoing translation
Helical Capsid - Answer protein binds to viral genome aggregating into helical structure
with nucleic acid on the inside — size of genome determines size of capsid
Icosahedral Capsid - Answer capsid composed of capsomeres that form icosahedron
shell where viral genome and enzymes reside inside
Why viruses have complex structure - Answer 1. protection from surrounding
environment
2. delivery of viral genetic material into target cell — nucleic acid doesn't pass through
plasma membrane easily
3. delivery of enzymatic functions required for replication of virus
,Ecology of Human Virome - Answer virome composition differs dramatically between
different body compartments
Where microbiome and virome come from - Answer 1. in utero
2. birth
microbiome of infant is constantly changing and stabilizes in adulthood
Where viral infections come from - Answer 1. other humans
2. zoonosis
3. arbovirus (via insects)
4. environment
Routes of transmission - Answer 1. fecal-oral
2. airborne
3. blood borne
4. sexual
Why are we not constantly ill - Answer 1. evolved to tolerate infections, or infection is
sub clinical
2. pathogenicity of virus varies between species; human may not be natural host
Hantavirus pathology in different species - Answer 1. viral infection has no effect on
deer mice and they excrete through urine and feces
2. kills human in 24hrs due to lungs filling with fluid
Influenza pathology in different species - Answer 1. infects bird guts
2. infect lungs in humans
Tissues in which virus replicates is different in species
Viral pathogenesis - Answer Process in which viral infection leads to disease
- may be of limited value to virus
- many infections are subclinical
Two components that contribute to viral disease - Answer 1. effect of viral replication on
host
2. effect of human immune response to virus
LCMC infection in mice - Answer Only lethal in mice who have functioning immune
,system
GBV-C and HIV-1 infections - Answer chronic infection of GBV-C associated with
reduced rate of progression to end stage of HIV-1 infection
Factors affecting new virus emergence/transmission - Answer 1. increased population
density
2. rapid transit
3. encroachment of humans into new environments (colonization)
4. global warming
5. changes in societal norms
Virus replication - Answer 1. binding/attachment to host cell
2. delivery
3. viral gene expression
4. assembly
5. release
Picornaviridae - Answer - enteroviruses and rhinoviruses
- transmission via respiration and fecal-oral
- global
- upper respiratory tract and gastrointestinal infection and poliomyelitis
- no treatment available; polio vaccine-preventable; associated vaccine-derived
poliomyelitis
- replication in cytoplasm respiratory and gastrointestinal epithelial cells and some
neuronal cells, then translocation and systemic dissemination
- use cap-independent internal ribosomal entry site (IRES) for translation
- outbreaks associated with crowding with severe disease susceptible hosts
Enteroviruses - Answer - genus consists 15 species
- enteroviruses A-L: poliovirus (3 serotypes), coxsackievirus, echo virus, enterovirus,
bovine, porcine and simian virus
- rhinovirus A, B, C (100 serotypes)
Poliovirus receptor and natural host - Answer CD155; humans
, Vaccine preventable
Rhinovirus receptor and natural host - Answer ICAM-1, LDLR; humans
Foot-and-mouth-disease virus receptor and natural host - Answer Integrins,
cloven-hooved ungulates
Hepatitis A virus receptor and natural host - Answer HAVcr-1, humans
Vaccine preventable
Clinical manifestations: non-specific febrile illness (fever, neonates) - Answer sepsis
Clinical manifestations: hand, foot and mouth disease - Answer herpangina
Clinical manifestations: acute hemorrhagic conjunctivitis - Answer EV70, CVA24
Clinical manifestations: Meningoencephalitis, meningitis, rhombencephalitis - Answer
EV71
Clinical manifestations: acute flacid paralysis/poliomyelitis, polio - Answer EVD68
Clinical manifestations: respiratory disease URTI, pneumonia, exacerbations - Answer
HRV
Clinical manifestations: cardiac disease myocarditis (dilated cardiomyopathy) - Answer
CVB3
Picornaviridae structure and replication - Answer non-enveloped, spherical,
icosahedral arrangement (VP1, VP2, VP3, VP4)
- capsid protein contain antigenic sites and bind host cell receptors
- VP4 reside on inside of membrane, while the other 3 are on the outside
- capsid helps virus survive in stomach acid and other harsher environments
Picornaviridae genome - Answer gene sequence yields polyprotein
- Virion protein, genome-linked
- linear genome 7.1-8.9 kB
- positive sense viral RNA is infectious
- IRES found on 5' end
- 11-15 cleavage products
- proteases 2A, 3C, 3D
- diversity: single nucleotide polymorphisms and recombination
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