L3 & L4 Picornaviruses Flashcards
(164 cards)
1
Q
What type of genome do picornaviruses have?
A
A single-stranded, positive-sense RNA genome
2
Q
Are picornaviruses enveloped or non-enveloped?
A
Non-enveloped
3
Q
What is the typical shape and symmetry of picornavirus capsids?
A
Icosahedral and symmetric
4
Q
What does the picornavirus genome encode?
A
A single large polyprotein
5
Q
What is the function of VPg in picornaviruses?
A
Acts as a primer for RNA synthesis
6
Q
What is the 5’ untranslated region (UTR) of the picornavirus genome important for?
A
Initiation of translation and replication
7
Q
What does the internal ribosome entry site (IRES) allow in picornaviruses?
A
Cap-independent translation initiation
8
Q
What are the major genera within the picornavirus family?
A
Enterovirus, Hepatovirus, Rhinovirus, Cardiovirus, Aphthovirus
9
Q
Which genus includes poliovirus, coxsackievirus, and rhinovirus?
A
Enterovirus
10
Q
Which picornaviruses infect the gastrointestinal tract?
A
Enteric picornaviruses like poliovirus and coxsackievirus
11
Q
What temperature does rhinovirus replicate best at?
A
Around 33°C
12
Q
What is the primary receptor for poliovirus entry?
A
CD155 (also known as PVR)
13
Q
How does poliovirus enter host cells?
A
Receptor-mediated endocytosis
14
Q
What is the first step after uncoating in picornavirus replication?
A
Translation of the polyprotein
15
Q
How is the polyprotein processed in picornaviruses?
A
By viral proteases 2A and 3C
16
Q
What proteases are used to cleave the polyprotein in picornaviruses?
A
2A protease and 3C protease
17
Q
Which viral protease cleaves host eIF4G to inhibit host translation?
A
2A protease
18
Q
How does the picornavirus genome switch from translation to replication?
A
By viral protease cleavage of host eIF4G, stopping host translation
19
Q
What is the role of the 3Dpol protein in picornavirus replication?
A
It synthesizes new RNA strands
20
Q
How is the VPg protein uridylylated?
A
By the viral polymerase 3Dpol using a uridine primer
21
Q
What is the function of 2C protein in picornavirus replication?
A
Helps in RNA replication and membrane rearrangement
22
Q
What triggers encapsidation of the picornavirus genome?
A
Positive-strand RNA synthesis reaching a critical point
23
Q
How does poliovirus exit host cells?
A
Cell lysis
24
Q
What are the symptoms of poliovirus infection?
A
Fever, sore throat, and potentially paralysis
25
What are the three serotypes of poliovirus?
Type 1, Type 2, Type 3
26
Which serotype of poliovirus is most commonly associated with paralysis?
Type 1
27
What are the two types of poliovirus vaccines?
IPV and OPV
28
How is the inactivated poliovirus vaccine (IPV) administered?
By intramuscular injection
29
How is the oral poliovirus vaccine (OPV) administered?
Orally
30
What is a major advantage of OPV over IPV?
Induces mucosal immunity
31
What is a risk associated with OPV?
Reversion to neurovirulence
32
What causes vaccine-derived polioviruses (VDPVs)?
Mutation and recombination during replication
33
What strategy is used to combat VDPVs in OPV?
Monovalent OPV and enhanced IPV use
34
What is the goal of the Global Polio Eradication Initiative?
Global eradication of poliovirus
35
How many wild poliovirus serotypes have been eradicated as of recent data?
Two (Type 2 and Type 3)
36
Which wild poliovirus serotype remains in circulation?
Type 1
37
What are some features of coxsackievirus infections?
Hand, foot, and mouth disease, herpangina
38
What diseases are associated with coxsackievirus A?
Aseptic meningitis and myocarditis
39
What diseases are associated with coxsackievirus B?
Fever, sore throat, rash, meningitis
40
How is echovirus transmitted?
Fecal-oral route
41
What clinical features are associated with echovirus?
Flu-like symptoms and meningitis
42
How are enteroviruses diagnosed in the laboratory?
PCR-based methods
43
What is the preferred sample for diagnosing enteroviruses?
Throat swabs, stool, and cerebrospinal fluid
44
What does RT-PCR target in enterovirus detection?
Conserved regions of the 5’ UTR
45
What is a unique feature of picornavirus RNA replication?
VPg-primed RNA synthesis
46
Why is the picornavirus RNA polymerase highly error-prone?
Lack of proofreading activity
47
What is a quasispecies in the context of picornaviruses?
A diverse population of related genomes
48
What advantage does genetic diversity provide to picornaviruses?
Escape from immune pressure and antiviral drugs
49
How does recombination occur in picornaviruses?
Template switching during replication
50
What is the significance of recombination in enterovirus evolution?
It generates diversity and can lead to new strains
51
What are the main characteristics of rhinoviruses?
Cause common cold
52
What receptor does the majority of rhinoviruses use for entry?
ICAM-1
53
Why is it difficult to develop a vaccine for rhinovirus?
High antigenic diversity
54
What structural features define the picornavirus capsid?
Icosahedral shell made of VP1–VP4
55
Which capsid protein is involved in receptor binding?
VP1
56
What is the function of VP1 in the picornavirus capsid?
Receptor binding and entry
57
How does the canyon hypothesis explain picornavirus entry?
The virus binds within a “canyon” on the capsid surface
58
What triggers genome release in picornaviruses?
Receptor binding and conformational changes
59
Which picornavirus genus includes Hepatitis A virus?
Hepatovirus
60
How is Hepatitis A transmitted?
Fecal-oral route
61
What disease does Hepatitis A cause?
Acute hepatitis
62
Is there a vaccine available for Hepatitis A virus?
Yes
63
What is the role of the 3C protease in picornaviruses?
Processes viral polyprotein and shuts down host functions
64
How do picornaviruses shut off host protein synthesis?
By cleaving eIF4G and halting cap-dependent translation
65
What does the picornavirus genome replicate via?
A minus-strand intermediate
66
What is the function of the cloverleaf structure in the 5’ UTR?
Stabilizing the genome and initiating replication
67
How do picornaviruses prime RNA synthesis?
Using uridylylated VPg
68
Which viral protein binds the 5’ cloverleaf to initiate replication?
3CD protein
69
Which host protein binds to both viral RNA and viral protein to help replication?
PCBP2
70
How is minus-strand RNA synthesis initiated in picornaviruses?
Using VPg primer and RNA-dependent RNA polymerase
71
What role does PCBP play in picornavirus replication?
RNA binding and replication complex formation
72
What viral protein induces membrane rearrangement for replication?
2B and 2C proteins
73
How does poliovirus subvert the secretory pathway?
Hijacks ER and Golgi membranes
74
What cellular organelles are involved in the replication complex formation?
Endoplasmic reticulum and Golgi
75
Why is VPg important in picornavirus replication?
Serves as a primer for both replication and translation
76
What causes the cleavage of eIF4G in host cells?
Cleavage by 2A protease
77
Which protease of picornavirus is primarily responsible for eIF4G cleavage?
2A protease
78
Why does cleaving eIF4G benefit the virus?
Prevents host mRNA translation, favoring viral RNA
79
What is the structure of picornavirus RNA at the 3’ end?
Polyadenylated tail
80
What is the significance of the 3’ poly(A) tail in picornavirus RNA?
Stabilizes RNA and enhances replication
81
How are picornavirus capsid proteins synthesized?
From a single polyprotein
82
What is the precursor protein for VP0, VP1, and VP3?
P1
83
When does VP0 get cleaved into VP2 and VP4?
After packaging or virion assembly
84
How does the virus ensure only genomic RNA is packaged?
Via encapsidation signals on the genome and RNA elements
85
What structural feature makes picornaviruses acid-stable or acid-labile?
The capsid structure, particularly stability under acidic pH, determines acid-stability; rhinoviruses are acid-labile, enteroviruses are acid-stable.
86
Which picornavirus genus includes viruses that infect both humans and animals?
The aphthovirus genus (e.g., foot-and-mouth disease virus) includes animal and human-infecting picornaviruses.
87
What is the typical size range of the picornavirus genome?
The genome is typically 7.2 to 8.5 kilobases in length.
88
How does the picornavirus genome mimic host mRNA for translation?
It includes a 5' untranslated region with an IRES that facilitates cap-independent translation.
89
What protein is covalently linked to the 5' end of the picornavirus genome?
VPg (viral protein genome-linked).
90
What role does VPg play in picornavirus replication?
VPg acts as a primer for RNA synthesis and plays a role in replication initiation.
91
How are picornavirus particles released from the host cell?
They are released via cell lysis.
92
What is the function of the 2A protease in picornavirus biology?
2A protease cleaves the viral polyprotein and also cleaves host eIF4G to inhibit translation.
93
How do picornaviruses inhibit host cell protein synthesis?
By cleaving eIF4G and sequestering host translation machinery for viral protein synthesis.
94
What is the function of the internal ribosome entry site (IRES) in picornaviruses?
It recruits host ribosomes directly to the viral RNA for translation initiation.
95
What structural proteins are encoded in the P1 region of the picornavirus genome?
VP1, VP2, VP3, and VP4.
96
How does the 3C protease contribute to both replication and immune evasion?
3C cleaves the polyprotein and interferes with host cell processes like transcription and innate immune signaling.
97
Which picornavirus is most commonly associated with hand, foot, and mouth disease?
Enterovirus 71 (EV-A71).
98
What is the role of 3Dpol in picornavirus replication?
It is the RNA-dependent RNA polymerase responsible for genome replication.
99
How are the capsid proteins VP1-VP4 generated?
Proteolytic cleavage of the P1 region by viral proteases 2A and 3C.
100
Which cellular receptor does poliovirus use for entry?
CD155 (also known as PVR – poliovirus receptor).
101
What disease manifestations can coxsackievirus A and B cause?
Coxsackievirus A causes herpangina and HFMD; Coxsackievirus B is linked to myocarditis and pericarditis.
102
How does enterovirus 71 affect the central nervous system?
It can cause brainstem encephalitis and acute flaccid paralysis.
103
How does rhinovirus differ from enteroviruses in terms of acid stability?
Rhinoviruses are acid-labile and inactivated in the stomach; enteroviruses survive gastric acid.
104
What are the differences between Group A and Group B coxsackieviruses?
Group A coxsackieviruses tend to cause skin/mucosal diseases; Group B cause organ-specific diseases.
105
How is echovirus transmitted?
Via fecal-oral and respiratory routes.
106
Which enterovirus serotypes have been linked to acute flaccid myelitis?
EV-D68 and EV-A71.
107
What is the role of host protein PCBP2 in picornavirus translation?
It stabilizes RNA secondary structures important for IRES function.
108
Which host factor is hijacked by picornaviruses to enhance IRES-mediated translation?
ITAFs (IRES trans-acting factors), including PTB and La protein.
109
What is the mechanism of genome replication in picornaviruses?
It involves VPg-primed synthesis of the negative strand, which serves as a template for positive-strand RNA.
110
What membrane alterations do picornaviruses induce in the host cell?
They induce the formation of double-membraned vesicles (DMVs) derived from the ER.
111
How do picornaviruses ensure unidirectional RNA synthesis?
Through control of primer usage and replication complex compartmentalization.
112
What immune sensing pathways are antagonized by picornavirus proteins?
MDA5, RIG-I, and PKR are inhibited or avoided via proteolytic cleavage by 2A and 3C proteases.
113
Which picornaviruses are known to cause myocarditis?
Coxsackie B viruses are notable causes.
114
What distinguishes parechoviruses from other picornaviruses?
They lack a polyprotein cleavage strategy and differ in genome organization.
115
What is the significance of the 5' cloverleaf structure in picornavirus RNA?
It helps initiate replication and binds PCBP2 and 3CD.
116
What role does the 3' poly(A) tail play in picornavirus replication?
It enhances replication and stabilizes the genome.
117
Which enteroviruses are associated with neonatal sepsis-like illness?
Echoviruses and coxsackieviruses.
118
How does enterovirus D68 enter the respiratory tract?
Via ICAM-5 or sialic acid receptors.
119
What structural feature allows enteroviruses to resist gastric acid?
Acid-stable capsid proteins.
120
How is genome circularization achieved in picornavirus replication?
Through base-pairing between the cloverleaf and 3' poly(A) tail via protein bridges.
121
Which picornavirus encodes a 2B protein that disrupts intracellular calcium stores?
Poliovirus.
122
What is the mechanism of action of the poliovirus vaccine?
It induces immune memory by presenting antigens without causing disease.
123
How does the live-attenuated oral polio vaccine differ from the inactivated polio vaccine?
OPV induces mucosal immunity and is orally administered; IPV induces systemic immunity and is injected.
124
What is the function of 3AB in picornavirus replication?
It helps recruit the RNA polymerase and localize replication.
125
How does the 3C protease cleave host transcription factors?
By cleaving transcription factors like TBP and p53.
126
What cellular compartment is primarily used for picornavirus replication complexes?
Cytoplasmic membranes, often modified ER.
127
How do picornaviruses escape detection by MDA5 and RIG-I?
By cleaving MAVS and other adapter proteins to block interferon responses.
128
How does picornavirus-induced autophagy benefit viral replication?
It may provide membranes for replication and prevent apoptosis.
129
What are the major antigenic sites on the VP1 capsid protein?
VP1 contains key neutralizing epitopes.
130
What is the typical incubation period for poliovirus?
Typically 7–14 days.
131
How is enterovirus infection diagnosed in a clinical setting?
PCR and viral culture of CSF, throat swabs, or stool.
132
What complications can arise from echovirus infection during pregnancy?
It can cause miscarriage, stillbirth, or neonatal sepsis.
133
Which viral protein is the main target of neutralizing antibodies?
VP1.
134
How do mutations in IRES elements affect viral pathogenicity?
They may impair IRES function and reduce translation efficiency.
135
How do picornaviruses modulate the unfolded protein response?
By blocking UPR sensors or modulating ER stress.
136
Which human picornavirus has been associated with type 1 diabetes?
Enterovirus B species, particularly coxsackie B.
137
What distinguishes hepatovirus A from other enteroviruses?
HAV has a different genomic organization and lacks a cytopathic effect.
138
How does HAV evade immune clearance despite being non-cytolytic?
By cloaking in exosome-like vesicles and avoiding detection.
139
What is the role of exosomes in the transmission of HAV?
They facilitate HAV egress in quasi-enveloped vesicles.
140
What is the function of the 2C protein in enteroviruses?
2C is involved in membrane remodeling and RNA replication.
141
How does temperature sensitivity affect rhinovirus replication?
It limits replication to upper respiratory tract at 33°C.
142
Which picornavirus is a common cause of viral meningitis?
Echovirus and coxsackievirus.
143
What laboratory methods are used to serotype enteroviruses?
RT-PCR and VP1 sequencing.
144
How do poliovirus and EV-D68 differ in neurotropism?
Poliovirus is neuroinvasive; EV-D68 shows limited CNS invasion.
145
Which part of the genome is used for genotyping enteroviruses?
The VP1 coding region.
146
How is genome packaging specificity achieved in picornaviruses?
Via packaging signals in the 5' UTR and RNA-protein interactions.
147
What is the process of encapsidation in picornavirus assembly?
It involves assembly of VP0-VP1-VP3 protomers into pentamers and capsids.
148
What role does host autophagy machinery play in enterovirus replication?
It may provide membranes and prevent degradation of replication complexes.
149
Which cytokines are suppressed by picornavirus infection?
Type I interferons and other inflammatory cytokines.
150
What is the difference between persistent and acute picornavirus infection?
Persistent infection may be non-lytic and involve low-level replication.
151
How do picornaviruses modulate host cell apoptosis?
By modulating pro-apoptotic and anti-apoptotic pathways.
152
How does the 2A protease cleave eIF4G to shut off host translation?
It cleaves eIF4G to stop host mRNA translation.
153
How do enteroviruses cause pancreatitis?
By direct invasion of pancreatic islets.
154
What role do environmental factors play in picornavirus outbreaks?
Hygiene, sanitation, and climate affect transmission.
155
How can recombination contribute to enterovirus evolution?
It allows for emergence of new serotypes and immune escape variants.
156
What is the epidemiological significance of non-polio enteroviruses?
They cause a wide range of diseases and are significant in pediatric infections.
157
What are the risk factors for severe EV-A71 infection?
Young age, lack of maternal antibodies, and certain genotypes.
158
What structural changes occur during picornavirus uncoating?
Capsid opens to release RNA into the cytoplasm.
159
Which picornaviruses are associated with conjunctivitis outbreaks?
Coxsackie A24 and enterovirus 70.
160
How is viral RNA synthesis initiated by VPg-uridylation?
By 3Dpol using VPg as a primer for uridylylation.
161
What distinguishes the antigenic drift seen in enteroviruses from influenza?
Enteroviruses drift more slowly and via recombination rather than point mutation.
162
What is the significance of the cis-acting replication element (cre)?
It enhances replication by acting as a template for uridylylation.
163
How does enterovirus infection contribute to chronic neurological conditions?
Possible links to chronic fatigue, type 1 diabetes, and other syndromes.
164
How can CRISPR-Cas13 be used to study or inhibit picornavirus replication?
By targeting and cleaving viral RNA or halting replication through knockdown.
