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Viral Infections Flashcards

1
Q

What are the 7 groups of viruses

A

dsDNA, ssDNA, dsRNA, +ssRNA, -ssRNA, rtDNA, rtRNA

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2
Q

The Baltimore classification system is based on…

A

Nucleic acid present in the virion particles and the pathway for expression of the genetic material

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3
Q

+ssRNA vs -ssRNA: infectivity

A 
\+ssRNA = infectious right away, directly translated into proteins
-ssRNA = not infectious right away, needs to be converted to +ssRNA first
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4
Q

Ambisense ssRNA

A

Virus resembles a negative sense RNA virus, but they can also translate genes from the positive strand

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5
Q

Viral entry is initiated by… (3)

A
  1. Conformational changes in virus that expose receptors for membrane fusion and penetration
  2. Transmit signals through membrane to prepare cell for invasion
  3. Induction of endocytic pathway
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6
Q

2 ways RNA viruses replicate their genomes

A
  1. RNA dependent RNA synthesis

2. RNA dependent DNA synthesis (RT) followed by DNA replication and transcription (Retroviruses)

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7
Q

What is a downside of a high error rate for RNA viruses

A

Error rates impose an upper limit on genome size (most are 5-15kb)

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8
Q

Virus assembly: non-enveloped vs enveloped

A

Non-enveloped can assemble in the cytoplasm or nucleus

Enveloped must get a lipid bilayer from a host cell membrane during assembly

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9
Q

4 steps of non-enveloped virus assembly

A
  1. Macromolecules form empty capsids
  2. Viral DNA is inserted via packaging sequence at one end
  3. Precursor core proteins are also packaged
  4. Proteolytic cleavage of precursors proteins by proteinase makes infectious virion
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10
Q

3 pathways of enveloped virus assembly

A
  1. Proteins transported to PM and capsid assembly and envelopment occur simultaneously
  2. Capsid assembly happens in cytoplasm and virus buds from PM to get its membrane
  3. Capsid assembly happens in ER, gets its envelop from ER and is exocytosis
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11
Q

Enteric viruses do not multiply in…

A

Food systems

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12
Q

What is poliovirus associated with

A

Milk and milk products

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13
Q

What kills polio in milk

A

Pasteurization above 70C for 30 seconds

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14
Q

How is polio transmitted

A

Fecal oral route, it multiplies in the intestine

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15
Q

What does polio do in the body

A

It invades the nervous system and can cause total paralysis in hours

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16
Q

Initial symptoms of polio in the body

A

Fever, fatigue, headache, vomiting, stiffness of neck

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17
Q

Genome and capsid of polio

A 
RNA genome (+ssRNA)
Non-enveloped
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18
Q

What are the 3 serotypes of the polio and what is different about them

A

PV1, PV2 and PV3

Each has a slightly different capsid

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19
Q

What is the most common polio serotype

A

PV1, localized in Pakistan and Afghanistan

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20
Q

Polio: 5’ NTR region

A

Harbors 2 domains, cloverleaf and internal ribosome entry site
Covalently linked to viral protein VPg

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21
Q

What does the cloverleaf structure do

A

Regulates viral RNA replication and the initiation of translation

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22
Q

What does the IRES domain do

A

Mediates translation of viral mRNA

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23
Q

How is polio mRNA translated

A

As one long polypeptide, later cleaved into mature structural and non-structural proteins by proteolytic processing

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24
Q

P1 precursor protein of polio is cleaved into what

A

VP1, VP3 and VP0

25
What does HAV effect
The liver
26
Duration and symptoms of HAV
8 weeks | Nausea, vomiting, diarrhea, jaundice, fever, abdominal pain
27
How is HAV spread
Fecal oral route, and undercooked contaminated seafood
28
If you get HAV once...
You are immune for life
29
Genome and capsid of HAV
``` RNA genome (+ssRNA) Non-enveloped ```
30
How many proteins does HAV encode
A single polyprotein
31
What part of the HAV polyproteins codes for the major capsid proteins
The N-terminal (the rest encodes series of nonstructural proteins required for HAV RNA replication)
32
What is the function of VPg on the 5; end of HAV genomic RNA
A protein primer for RNA synthesis
33
How does HAV spread in the body
By secretion from infected hepatocytes via the biliary system
34
When does fecal shedding of the virus reach its max
Just before the onset of hepatocellular injury (individual is most infectious)
35
What accompanies fecal shedding in HAV infection
Extended viremia, but at a lower magnitude
36
What is indicative of hepatocellular injury
Serum alanine aminotransferase
37
When are norovirus outbreaks most common
In fall and winter months
38
What is the contagious period of norovirus
The moment they feel ill to 3 days after recovery (sometimes two weeks)
39
Where is norovirus found in human secretions
The stool and vomit
40
3 ways someone can be infected with norovirus
1. Direct contact 2. Touching surfaces 3. Eating/drinking contaminated sources
41
How is norovirus spread
Fecal oral route, sometimes shellfish
42
Main symptoms of norovirus
Diarrhea, vomiting, nausea, stomach cramps (less common can be headache, chills, fever)
43
Genome and capsid of norovirus
``` RNA genome (+ssRNA) Non-enveloped virus ```
44
What norovirus genogroup is the most prevalent in humans
Genogroup II
45
What NoV genogroups infect: humans, bovine, mice
Humans: I, II, IV Bovine: III Mice: V
46
What does ORF1 in NoV encode
A single nonstructural polyprotein
47
What does ORF2 in NoV encode
VP1 capsid protein (divided in shell and protruding domains)
48
What does ORF3 in NoV encode
Minor structural protein VP2
49
What does ORF4 in NoV encode and where is it found
Only in mice NoV | Encodes virulence factor 1 (newly defined)
50
Why are rotavirus infections rare in adults
Because you get it as a kid (before the age of 5) and immunity develops with each infection so subsequent infections are less severe
51
How is rotavirus transmitted
Fecal oral route
52
Treatment for rotavirus
Oral rehydration and vaccination to prevent infection
53
Rotavirus symptoms
Nausea, vomiting, watery diarrhea and low-grade fever
54
What is the most common cause of death related to rotavirus infection
Diarrhea
55
Genome and capsid of rotavirus
``` RNA genome (dsRNA) - segmented, linear Non-enveloped virus ```
56
How does rotavirus achieve rapid evolution through genetic reassortment
If someone is co-infected with two strains, the segmented genome allows them to be mixed and packaged into a new virion
57
What is the surface of the rotavirus made of
The VP7 glycoproteins and embedded with the VP4 spike attachment protein
58
Why is the dsRNA genome of the rotavirus never completely uncoated
To prevent activation of the an antiviral state by the cell in response to the dsRNA

Food-Borne Pathogens (14 decks)

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