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CVSOH BVSc3 > Virology - Calicivirus, coronavirus, reovirus, flavivirus > Flashcards

Virology - Calicivirus, coronavirus, reovirus, flavivirus Flashcards

Calicivirus Coronavirus Reovirus Flavivirus

1
Q

Is calicivirus enveloped?

A

No

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2
Q

What kind of symmetry does calicivirus nucleocapsid have?

A

Icosohedral

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3
Q

How many dimers does calicivirus have?

A

90

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4
Q

What kind of classification of virus is calicivirus?

A

Positive sense single stranded RNA virus - group 4 of Baltimore classification system

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5
Q

What is an example of a calicivirus?

A

Norovirus

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6
Q

What does calicivirus mainly cause?

A

Gastroenteritis - vomiting, diarrhoea

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7
Q

What species does calicivirus affect?

A

Most species

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8
Q

What are the structural proteins initials?

A

VP

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9
Q

How many non structural and structural capsid proteins does calicivirus have?

A

NS - 7

VP - 2

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10
Q

What is the important protein called on the calicivirus and where is it located?

A

VPg

Covalently bonded on the 5 prime end (5’)

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11
Q

What is found at the 3’ end and what is it for?

A

Poly A tail
Increase the stability of the RNA
Help transport newly synthesised RNA out of the nucleus into the cytoplasm

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12
Q

What is a strand of positive sense RNA the equivalent to? What does this mean?

A

mRNA

It is infectious on its own

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13
Q

How does the calicivirus replicate?

A

It converts its positive sense RNA into negative sense RNA

This then acts as a template for millions of copies of positive sense RNA to be made

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14
Q

What does RdRp stand for and what is it for?

A

RNA dependent RNA polymerase
Needs RNA to build RNA
Is used to replicate the viral genome

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15
Q

What is RdRp encoded by?

A

Viral NS7

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16
Q

What does the 5’ cap VPg do?

A

Protects the 5’ end of the viral RNA from cellular exonucleases
Also acts as a primer during negative strand RNA synthesis

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17
Q

What are the steps of calicivirus infection and replication?

A

Attachment - cell receptors
Entry - endocytosis
Uncoating and RNA release - escapes the endosome
Translation - RNA attaches to ribosomes and produces RdRp viral protein
RNA replication - RdRp binds to viral genome and replicates it
Assembly - RNA is encapsidated

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18
Q

What receptors does feline calicivirus bind to?

A

Sialic acid

Junction Associated Molecule-A (JAM-A)

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19
Q

What does calicivirus use to bind to receptors?

A

VP1

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20
Q

Where does calicivirus replication occur?

A

In the ER and golgi in membranous vesicles

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21
Q

What is self assembly?

A

When viral proteins find it more energetically favourable to interact with each other to remain alone

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22
Q

What does calicivirus have on its surface?

A

32 cup shaped depressions

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23
Q

What does calicivirus do to the cells?

A

Causes cell lysis/death - cytopathic

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24
Q

Why does calicivirus cause cell death?

A

Has to exit the cells but it is not enveloped (doesnt bud from the surface of the cell) so cant get out otherwise

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25
Q

What disease does calicivirus cause in cats?

A

Feline calicivirus (FCV) infection - cat flu

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26
Q

What are the symptoms of feline calicivirus?

A 
Acute oral and upper respiratory system disease 
Sneezing
Palatine ulcerations 
Fever
Nasal discharge etc.
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27
Q

How is feline calicivirus transmitted?

A

Fomites, direct contact and aerosol over short distances

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28
Q

What is the worse strain of FCV called? What does it cause?

A

FCV-associated virulent systemic disease
Multiple organ failure
Disseminated intravascular coagulation

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29
Q

Do cats recover from calicivirus?

A

Most do but some remain as carriers or have persistent infection in some adult cats

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30
Q

How does calicivirus evade the immune system in persistent infection?

A

Antigenic drift

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31
Q

How is calicivirus diagnosed?

A

Swabs from nose and oropharynx

Identification using PCR

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32
Q

Can you vaccinate against calicivirus? How?

A

Yes - intranasal

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33
Q

What antibody is used in the calicivirus vaccine?

A

IgG

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34
Q

What disease does calicivirus cause in rabbits?

A

Rabbit haemorrhagic disease

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35
Q

What is the mortality rate of rabbit haemorrhagic disease?

A

80% - high

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36
Q

How is rabbit haemorrhagic disease transmitted?

A

Faecal-oral route
Biting insects
Flies
Fomites

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37
Q

What are the symptoms/pathology of rabbit haemorrhagic disease?

A

Nasal haemorrhage
Necrosis of the liver
Disseminated intravascular coagulation

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38
Q

How is rabbit haemorrhagic disease diagnosed?

A

Immunofluorescence
PCR - detect viral genome
ELISA - detect viral proteins
Electron microscopy

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39
Q

Is there a vaccine for rabbit haemorrhagic disease?

A

Yes

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40
Q

What order of viruses is coronavirus in?

A

Nidovirales

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41
Q

What viral classification are nidovirales?

A

Positive sense single stranded RNA viruses - group 4 of Baltimore classification system

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42
Q

What does polycistronic RNA genome mean?

A

The separate proteins that are encoded are found on a single molecule of mRNA

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43
Q

What family is coronavirus in?

A

Coronaveridae

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44
Q

What genus are in the family coronaveridae?

A

Coronavirus

Torovirus

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45
Q

What is the genus coronavirus split into?

A

Alpha, beta and gamma coronaviruses

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46
Q

What do coronaviruses look like?

A

Surface projections forming a spherical halo made of club shaped surface spike proteins

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47
Q

Does coronavirus have an envelope?

A

Yes

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48
Q

What symmetry does the coronavirus nucleocapsid have?

A

Helical - unusual as most positive sense RNA viruses have icosahedral symmetry

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49
Q

What shape does the torovirus have?

A

Crescent shape

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50
Q

What shape do bafinivirus and ronivirus have? (In the coronaveridae family)

A

Rod

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51
Q

What is the coronavirus spike structure?

A

Trimer
Three receptor binding S1 domains
Three S2 domains which anchor the spike into the envelope

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52
Q

How does coronavirus enter cells?

A

Receptor binding domain on the end of the spike protein attaches to a host cell receptor
This causes endocytosis

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53
Q

Where do coronaviruses replicate?

A

In the cytoplasm

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54
Q

What does translation of the positive strand genomic material produce?

A

A large polyprotein which can be broken down into viral proteins such as RdRp

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55
Q

What do viruses assemble in?

A

Intracellular vesicles

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56
Q

What is a syncytia?

A

A large multinucleated cell formed from the fusion of lots of different cells

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57
Q

What causes syncytia to occur?

A

Spike proteins being expressed on the surface of infected cells attach to receptors on neighbouring uninfected cells and fuse them together

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58
Q

How do coronaviruses exit cells?

A

Budding from the ER into vesicles and then exocytosis

Because they have an envelope

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59
Q

What is the structure of the coronavirus genome?

A

Nonsegmented - all genes encoded on a single strand of the genome
Largest genome

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60
Q

What do the open reading frames encode?

A

The replication machinery

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61
Q

What do the nested set of genes on the 3’ end of the genome encode?

A

Viral structural proteins

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62
Q

WHat is subgenomic RNA?

A

The genome is truncated - a portion/fragment of the original size

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63
Q

What causes subgenomic RNA?

A

The RNA polymerase gets bounced off the genome at transcription-regulatory sequences (TRS)
When it rejoins the genome, it skips a bit

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64
Q

What is the process of producing subgenomic RNA called?

A

Discontinuous transcription

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65
Q

What are the different lengths of RNA that are produced called?

A

Nested RNA

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66
Q

What is the main disease in pigs that is produced by coronavirus?

A

Porcine transmissible gastroenteritis

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67
Q

What are the symptoms of porcine transmissible gastroenteritis?

A

Watery diarrhoea

Vomiting

68
Q

What is the route of infection of porcine transmissible gastroenteritis?

A

Ingestion via faecal-oral route

69
Q

What age of pigs does this affect?

A

Neonates - mortality

Does cause morbidity in older pigs though

70
Q

What receptor does porcine transmissible gastroenteritis virus attach to?

A

Animopeptidase-N (APN) - on epithelial cells of intestinal villi

71
Q

What part of the intestinal villi is affected in infection by porcine transmissible gastroenteritis?

A

Crypts

Also infect paneth cells in crypts

72
Q

What do paneth cells do?

A

Specialised secretory cells
Produce antimicrobial peptides and immunomodulatory proteins
Regulates composition of gut flora

73
Q

What does infection with porcine transmissible gastroenteritis ultimately cause?

A 
Stops epithelial escalator Affects villi integrity - blunts them
Villi slough off
Loss of balance of the gut flora
Loss of fluid absorption
Cant digest milk
74
Q

How is porcine transmissible gastroenteritis diagnosed?

A

Histological staining of the intestines
ELISA on faeces
PCR

75
Q

How are piglets protected against porcine transmissible gastroenteritis?

A

Maternal IgA antibodies via colostrum

76
Q

What are the two types of feline coronavirus?

A

Feline infections peritonitis virus (FIPV)

Feline enteric coronavirus (FECV)

77
Q

How is feline coronavirus transmitted?

A

Faecal-oral route

78
Q

What does FECV infect?

A

Gastrointestinal epithelial cells only - causing enteritis

79
Q

What are the clinical signs of FECV?

A

Few outward signs
Usually chronic
May be brief bouts of diarrhoea

80
Q

What is the outcome of FIP?

A

Progressive disease that is almost always fatal

81
Q

What is the timeframe of FIP?

A

8-9 days

82
Q

How do cats get FIP?

A

FECV virus mutates in 10% of cats and infects WBCs - monocytes and macrophages
This spreads the virus throughout the body causing big inflammatory reaction in abdomen, kidney and brain

83
Q

What is antibody dependent enhancement?

A

Where virus infects macrophages better in the presence of antibodies that are against the spike protein

84
Q

How do you diagnose FECV and FIP?

A

Histological examination - only definitive one for FIP
ELISA doesnt distinguish between FECV and FIP
PCR

85
Q

Can you vaccinate against FIP?

A

Yes - intranasal
Live mutant strain of the virus
Designed to prevent antibody dependent enhancement

86
Q

What kind of classification of virus is reovirus?

A

Double stranded RNA viruses - group 3 in the Baltimore classification system

87
Q

What viruses are included in the reoveridae family?

A

All animal viruses with multisegmented double stranded RNA genomes

88
Q

What kind of symmetry does reovirus nucleocapsid have?

A

Icosahedral

89
Q

Are reoviruses enveloped?

A

No

90
Q

What is the structure of the reovirus capsid?

A

Triple layered

91
Q

What is the structure of the genome of reoviruses?

A

No poly A tail (does still have a 5’ cap)
Segmented - 9-12 segments
Double stranded

92
Q

What are the two ways that reovirus alters its genome?

A

Genetic shift and genetic drift

93
Q

What does the segments allow reovirus to do?

A

Genetic shift - via genetic reassortment of the segments

94
Q

What is genetic shift in reoviruses?

A

Where they swap segments of their genome with other reoviruses that are coinfecting the same cell forming a recombinant virus
This is a sudden change/mutation.

95
Q

What is genetic drift?

A

When mutations occur when the genome is replicating using RdRp
mutations are slowly accumulated over time

96
Q

How is the reovirus genome replicated?

A

Negative strand is copied into mRNA by RdRp
These mRNAs are encapsidated and copied to produce negative RNA
The +ve and -ve RNA strands base pair to produce double stranded RNA

97
Q

Where does reovirus replication occur?

A

Entirely in the cytoplasm

98
Q

What does reovirus use to bind to the receptors on host cell?

A

Sigma1 protein

99
Q

What receptors does reovirus bind to?

A

Sialic acid

JAM-A

100
Q

What extra protein does reovirus use to bind to integrin as a final step to enter the cells?

A

Lambda1 protein

101
Q

What are reovirus inclusion bodies called?

A

Viral factories

102
Q

Where are viral factories located?

A

ER vesicles

103
Q

What do viral inclusion bodies include?

A

Filaments
Viral proteins
Single and double stranded RNA
Viral particles

104
Q

What are examples of reovirus?

A

Rotavirus

Bluetongue virus

105
Q

What does rotavirus cause?

A

Watery diarrhoea in young animals (especially intensively farmed)
Looks like white scours
Vomiting
Dehydration

106
Q

What are rotaviruses divided into and which is the biggest?

A

Serogroups A-G

A contains the most isolates

107
Q

How is rotavirus transmitted?

A

Faecal-oral route

108
Q

How does rotavirus affect the intestines?

A

They destroy terminally differentiated enterocytes at the tips of the villi
Shortens the villi so reduces the SA

109
Q

How does rotavirus cause vomiting and diarrhoea?

A

NSP4 is released from infected enterocytes
This signals for increased secretion of chloride ions into the intestinal lumen
This causes water to move into the lumen by osmosis
It also stimulates enteric/vagal nerves for intestinal motility and nausea

110
Q

How do you diagnose rotavirus?

A

Electron microscopy
ELISA
PCR

111
Q

What type of vaccine is used for rotavirus and who is it administered to?

A

Killed virus vaccine

Pregnant animals - raises antibodies (IgA) in colostrum

112
Q

What is the vector for bluetongue disease?

A

Culicoides - biting midges

113
Q

What parts of the body are affected by bluetongue disease?

A

Initially replicates in the draining regional lymph node

Spreads to organs such as lungs, lymph nodes and spleen

114
Q

What cells does bluetongue virus replicate in?

A

Macrophages
Dendritic cells
Vascular endothelium

115
Q

What cells does bluetongue virus spread in?

A

All blood cells

116
Q

What are the clinical signs of bluetongue disease?

A

Most are asymptomatic

Fever, conjunctivitis, lameness, cyanosis, drooling etc. in varying degrees

117
Q

What causes death from bluetongue disease?

A

Pulmonary oedema

118
Q

How does the virus survive vector free periods?

A

Overwintering in host lymphocytes - gamma delta T cells

119
Q

What do inflamed fibroblasts express?

A

WC1 ligand

120
Q

What activates T cells to release the bluetongue virus from dormancy?

A

Co culture of the gamma delta T cells and fibroblasts during inflammation caused by the midge bite

121
Q

How do you diagnose bluetongue disease?

A

PCR detecting viral RNA

Difficult to culture

122
Q

Can you vaccinate against bluetongue disease?

A

Yes - but only if it is the same serotype as the vaccine

123
Q

What do you use to vaccinate against multiple serotypes of bluetongue disease?

A

Polyvalent vaccine

124
Q

What does flavus mean?

A

Yellow

125
Q

Does flavivirus have an envelope? Any features?

A

Yes - tightly adhered with glycoprotein spikes

126
Q

What classification of virus is flavivirus?

A

Single stranded positive sense RNA - group 4 of the Baltimore classification system

127
Q

What symmetry is flavivirus?

A

Icosaheral

128
Q

What is an example of flavivirus in humans?

A

Zika virus

129
Q

What are the two main genera of flaviviridae?

A

Flavivirus

Pestivirus

130
Q

What vectors spread flavivirus?

A

Mosquitos and ticks

131
Q

What cells does flavivirus infect initially?

A

Keratinocytes and skin dendritic cells in the epidermis

132
Q

Where in the body does flavivirus replication occur?

A

Lymphoid organs

133
Q

Where in the body does flavivirus affect?

A

Central nervous system - neuroinvasive and neurovirulent

134
Q

What do the glycoprotein spikes on the flavivirus bind to on target cells to cause endocytosis?

A

Lectin receptors - DC-SIGN and DC-SIGNR

135
Q

What do flaviviruses have on their 5’ and 3’ ends of the genome?

A

5’ - capped

3’ no poly adenylated/poly A tail

136
Q

What causes the varying lengths of viral genomic RNA (sfRNA) in flaviviruses?

A

A host enzyme called XRN1 digests it

137
Q

What does sfRNA stand for?

A

Small fragment RNA

138
Q

How does the sfRNA help the flaviviruses?

A

It makes it more infectious and replicates better

It also stops the immune response

139
Q

Where does virion assembly occur?

A

On the membranes of the endoplasmic reticulum

140
Q

How do immature virions mature?

A

Conformational change occurs as the virion is transported from the ER to the acidic pH in the golgi

141
Q

What is cleaved on the virion to make flavivirus infectious? What is produced?

A

prM protein is cleaved to make M protein

142
Q

What is the enzyme that cleaves the prM to make the M protein in flavivirus maturation?

A

Furin

143
Q

How does flavivirus exit the cell?

A

Exocytosis and lysis

144
Q

What are examples of flaviviruses?

A

Louping ill virus

Bovine viral diarrhoea virus (BVD)

145
Q

What is louping ill virus spread by?

A

Ticks - ixodes ricinus

Uses the tick grouse cycle

146
Q

What part of the body does louping ill virus affect?

A

CNS - meningoencephalitis

147
Q

What animal does louping ill virus affect?

A

Sheep

Other animals can be carriers though

148
Q

What symptoms does louping ill virus cause?

A

Two phases
1 - flu like symptoms
2 - more severe, fever and neuro effects

149
Q

How do you diagnose louping ill virus?

A

Histology of CNS material
Detection of IgM through ELISA
PCR
Culture

150
Q

How are animals vaccinated against louping ill virus?

A

Inactivated virus

Passive immunity from colostrum

151
Q

What is a diagnostic marker for louping ill virus?

A

Haemagglutination inhibition - when there is no agglutination of virus and RBCs if they are mixed in serum

152
Q

What genus is bovine viral diarrhoea (BVD) virus in?

A

Pestivirus

153
Q

What is persistant infection by BVD called?

A

Mucosal disease

154
Q

What is BVD made up of?

A

Two major genotypes

Two distinct biotypes in each genotype

155
Q

What are the different types of biotypes of BVD?

A

Cytopathic and non-cytopathic (persistant infection)

156
Q

Which is the most common biotype of BVD?

A

Biotype 1

157
Q

What does conversion of biotype 1 to cytopathic form cause in BVD?

A

Typical mucosal disease

158
Q

What does conversion of biotype 2 to cytopathic form cause in BVD?

A

Thrombocytopenia and haemorrhagic disease

Less common

159
Q

What causes conversion of biotypes to cytopathic strains in BVD?

A

Massive changes to the viral genome caused by mutations and recombination events

160
Q

What are the symptoms of BVD?

A 
Mostly subclinical - morbidity rather than mortality
Fever 
Diarrhoea
Inappetence
Depression
161
Q

When in gestation does transplacental infection of BVD cause persistent infection?

A

Between 90-120 days of gestation after foetal immune system develops
Infection before this causes foetal death

162
Q

When can a persistent infection of BVD turn into a cytopathic disease?

A

Between 6 months and 2 years

163
Q

What is the mortality rate of mucosal disease?

A

100%

164
Q

What does the cytopathic biotype of BVD have a tropism for?

A

Gut lymphoid tissue

165
Q

How do you diagnose BVD?

A

Look at herd repro records - abortion etc.
Tissue culture - immunofluorescence
PCR
ELISA

166
Q

How do we control BVD?

A

Remove persistently infected animals

Inactivated vaccines - reduces clinical disease but not foetal infections

CVSOH BVSc3 (60 decks)

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