Lecture 2 Flashcards
(177 cards)
1
Q
Name 3 facts about RNA viruses
A
- Must encode or carry RNA-dependent RNA polymerase
- Replicate in cytoplasm
- genomic structure determines
2
Q
What special enzyme must RNA viruses encode or carry?
A
RNA-dependent RNA polymerase
3
Q
Where do RNA viruses usually replicate inside the host cell?
A
cytoplasm
4
Q
What determines how RNA viruses replicate and function?
A
genomic structure
5
Q
Name 3 facts about DNA viruses
A
- Viral genomes stable in cell (persistent infections)
- Most occupy nucleus
- Temporal control of viral gene expression
6
Q
Are DNA virus genomes stable or unstable in host cells?
A
Stable (which can lead to persistent infections)
7
Q
Where do most DNA viruses replicate in the host cell?
A
nucleus
8
Q
How is viral gene expression controlled in DNA viruses?
A
It’s controlled temporally (genes are turned on at different times)
9
Q
What are virulence factors in viruses?
A
Virus-encoded activities that enhance attachment, transmission, replication, and evasion of host responses
10
Q
What does an attenuated virus mean?
A
A virus that has lost its virulence factors
11
Q
What is acquisition in viral infection?
A
when a virus gains access to the body
12
Q
Where do viruses often initiate primary site infection?
A
in oral or respiratory areas
13
Q
What immune response is activated first during a viral infection?
A
innate immune response
14
Q
What are two components of the innate immune response?
A
phagocytes and IFN response
15
Q
What is the incubation period in viral infection?
A
time when virus is present but symptoms have not appeared
16
Q
What happens after the incubation period in a viral infection?
A
virus spreads to secondary site
17
Q
What occurs at the virus’s target tissue?
A
virus replicates in target tissue
18
Q
What immune response follows the innate response?
A
adaptive immune response
19
Q
What are the effects of the adaptive immune response?
A
it can be beneficial or cause immunopathologies
20
Q
What does contagion production mean in a viral infection?
A
virus is being made and can spread to others
21
Q
What are the two possible outcomes of a viral infection?
A
Resolution (clearing the virus) or persistence (long-term infection)
22
Q
What does “asymptomatic” mean in viral infection?
A
can progress to 2° site without
symptoms
23
Q
What is the prodrome phase?
A
A stage with early, non-specific symptoms like fever, aches, and chills.
24
Q
What are examples of prodrome symptoms?
A
fever, aches and chills
25
What immune response typically resolves a viral infection?
innate immune response
26
What is the convalescence phase?
The recovery period where symptoms result from tissue repair
27
What important immune function develops during convalescence?
immunological memory
28
What is the most common route of virus entry?
inhalation
29
Which parts of the body do viruses most commonly infect via inhalation?
Oral and respiratory mucosa
30
Why do epithelial cells in the respiratory and oral areas allow viral infection?
They express viral receptors and have the necessary replication machinery
31
How are viruses transmitted via the gastrointestinal route?
The virus is shed in feces and enters another person through the fecal-oral route
32
What are M cells in Peyer’s patches?
Special cells in the intestines that help viruses cross into the body during gastrointestinal infection
33
Name 4 other routes of transmission
1. sexual
2.blood
3. transcutaneous
4.
Maternal (fetal/neonatal)
34
What is an abortive viral infection?
a failed infection
35
What defines an inapparent infection?
It is asymptomatic with no consequences
36
What happens during a lytic infection?
infection kills host cell
37
What characterizes a non-lytic (persistent) infection?
infection does not result in cell death
38
How is a chronic infection described in this context?
It is a non-lytic but productive infection
39
What defines a latent infection?
It is non-productive
40
What is meant by a recurrent infection?
It is characterized by on/off production of virus
41
How is a transforming infection described?
immortalizing
42
What does a permissive infection allow?
It allows a complete replicative cycle, typically resulting in lysis
43
What is a semi-permissive infection?
It involves slow, inefficient replication
44
What characterizes a non-permissive infection?
The host cell either lacks the essential machinery or actively blocks replication or assembly
45
What do lytic infections do to target cells?
kills target cells
46
How do lytic infections affect host tissue?
inflict damage
47
What do lytic infections do to the cell’s ability to repair?
inhibit repair
48
How do lytic infections impact DNA and protein synthesis?
inhbits DNA and protein synthesis
49
What happens to host nucleic acids during lytic infection?
Degrade host nucleic acids
50
How do lytic infections disrupt the cell?
Disrupt host cellular functions
51
What do infected host cells express during lytic infection?
viral antigens
form syncytia (multi-nucleate, giant cells)
52
How do lytic infections relate to apoptosis?
They promote apoptosis, although some viruses can suppress it
53
How are viruses released from cells during non-lytic infections?
exocytosis or budding
54
What type of cell is involved in non-lytic infections where the virus can't replicate?
a non-permissive cell
55
What can viral gene products do to infected cells in non-lytic infections?
Viral gene products transform cells
56
What happens when viral DNA incorporates into the host cell's nucleus?
disrupt growth regulation
57
What is oncogenic transformation?
When viral genes promote unregulated cell growth
58
What percentage of cancers are related to viral oncogenes?
15%
59
Name 4 most common viral diseases
1. common cold
2. influenza
3. flulike syndromes
4. gastroenteritis
60
Name 6 determinants of viral disease
1. exposure/entry
2. viral dose
3. target tissue/tissue tropism
4. permissiveness of cells
5. host status (age, immunity, health)
6. viral structure (naked vs. envelope)
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slide 16 and 17
62
ORTHOMYXOVIRUSES:
INFLUENZA VIRUSES
63
What type of envelope does the influenza virus have?
Pleomorphic envelope
64
What is the shape of the influenza virus's nucleocapsid?
Helical nucleocapsid capsid segments
65
What kind of genome does influenza have?
ssRNA(-)
66
How many RNA segments are in the influenza virus genome?
Segmented genome (8 RNA(-) segments)
67
What is antigenic shift, and why is it important for influenza?
It's a major genetic change that increases the chance of new mutant strains
68
What do mutant influenza strains potentially cause?
Epidemics and pandemics
69
Which types of influenza are important for human disease?
Influenza A and B
70
Where does influenza infect the body?
upper respiratory tract epithelium
71
Where does transcription and replication of influenza occur?
nucleus
72
Where does influenza virus assembly and release take place?
at the plasma membrane
73
s 23
74
What are PB2, PB1, and PA in the influenza virus?
components of the viral polymerase complex
75
What is the role of NP in the influenza virus?
It is the nucleocapsid protein that associates with the RNA genome
76
What does HA (hemagglutinin) do in influenza?
attachement and fusion protein
77
What is the function of NA (neuraminidase)?
cleaves sialic acid in mucus
78
What is the role of M2 in the influenza virus?
It is a membrane protein channel that facilitates uncoating
79
What does M1 do in the influenza virus?
It is a structural matrix protein
80
What type of proteins are NS1 and NS2 in influenza?
nonstructural proteins
81
What is the function of NS1 in the influenza virus?
it acts as a IFN anatagonist
82
s 25
83
PARAMYXOVIRUSES:
PARAINFLUENZA VIRUSES
84
What is the genus name for the measles virus?
Morbillivirus
85
How many serotypes for measles virus exist?
one serotype
86
What is the genus name for the mumps virus?
Paramyxvirus
87
How many serotypes of the mumps virus exist?
one serotype
88
What types of parainfluenza viruses exist?
types 1-4
89
What genus does Respiratory Syncytial Virus (RSV) belong to?
pneumovirus
90
What other virus is included in the pneumovirus genus?
Metapneumovirus
91
How stable are paramyxoviruses in the environment?
very liable and quickly inactivated
92
What environmental factors inactivate paramyxoviruses?
Heat, organic solvents, detergents, ultraviolet or visible light, and low pH values
93
What kind of envelope do paramyxoviruses have?
A pleomorphic envelope with specific viral attachment proteins
94
What shape does the nucleocapsid of paramyxoviruses have?
helical nucleocapsid
95
What type of genome do paramyxoviruses have?
Large, ssRNA(-) viruses
96
What is the structure of the genome of paramyxoviruses?
linear genome
97
What do paramyxoviruses carry with their nucleocapsid?
carries nucleocapsid-associated proteins
98
How are paramyxovirus genera distinguished?
by their attachment proteins
99
What are some major diseases caused by paramyxoviruses?
measles, mumps & RSV
100
What structure do paramyxoviruses induce in infected cells?
Syncytia
101
How do paramyxoviruses invade cells?
membrane fusion
102
How are new paramyxoviruses released from host cells?
by budding
103
How are paramyxoviruses transmitted?
aresols
104
Where do paramyxoviruses establish their primary infection in the body?
respiratory tract
105
s35
106
What is the function of the NP (nucleoprotein) in paramyxoviruses?
It binds and protects viral RNA
107
What does the P (polymerase phosphoprotein) do in paramyxoviruses?
facilitates RNA replication
108
What role does the L protein play in paramyxoviruses?
acts as a RNA polymerase
109
What does the F (fusion) protein do in paramyxoviruses?
promotes fusion and viral entry
110
Which attachment protein is found in parainfluenza virus and mumps?
HN (hemagglutinin-neuraminidase), which binds to sialic acid.
111
What is the attachment protein for measles virus, and what does it bind?
H (hemagglutinin), which binds MCP and SLAM receptors
112
What is the attachment protein in RSV, and what is special about it?
G (glycoprotein), which binds sialic acid but is not a hemagglutinin
113
What is the role of the M (matrix) protein in paramyxoviruses?
It assists in the assembly of virions
114
Adenoviruses
115
Does adenovirus have an envelope?
no envelope
116
What is the shape of the adenovirus capsid?
Icosadeltahedral capsid
117
What type of genome does adenovirus have?
dsDNA virus and linear genome
118
How many adenovirus serotypes exist, and which are most common?
52 serotypes (1-7 most common)
119
Where does adenovirus replicate and assemble in the cell?
nucleus
120
What kind of infection does adenovirus cause in permissive cells?
lytic infection
121
What kind of infection does adenovirus cause in non-permissive cells?
latent ot persistent
122
Can adenovirus be transformative in human cells?
No, it is only transformative in non-human cells
123
What biological discoveries has adenovirus been important for?
introns and RNA splicing
124
What medical applications is adenovirus used for?
gene replacement, anti-viral & cancer therapy
125
s44
126
Where are the viral attachment proteins located on adenovirus?
On fibers at the vertices of the capsid
127
What do adenovirus fiber proteins determine?
Type-specific antigens that define serotype specificity
128
What is the function of adenovirus fibers
act as hemagglutinins
129
What part of the adenovirus is toxic to cells?
fibers and pentose base
130
What host molecule does adenovirus attach to for entry?
Immunoglobulin (Ig) superfamily glycoproteins, including the Coxsackie-Adenovirus Receptor (CAR
131
Besides CAR, what else can adenovirus bind to?
MCH I
132
How does adenovirus enter the host cell?
Through receptor-mediated endocytosis
133
What happens after adenovirus is endocytosed?
It lyses the vesicle and enters the nucleus.
134
What do E1A and E1B genes inhibit in adenovirus?
inhibits p53 and p105B
135
What is the function of the E2 gene in adenovirus?
It encodes the viral DNA polymerase, which is necessary for replicating viral DNA
136
What does the E3 gene do in adenovirus?
It is an immunosuppressant that blocks apoptosis and decreases MHC I expression
137
What is the role of the E4 gene in adenovirus?
It prevents apoptosis, helping the virus keep the host cell alive longe
138
What do VA RNAs do in adenovirus?
They inhibit (IFN) response, blocking antiviral defenses.
139
What do the L1 to L5 genes encode in adenovirus?
they encode structural/capsid proteins
140
What are the main routes of transmission for adenovirus?
1. inhalation
2. close contact
3. oral/fecal
4. fomites
5. poorly chlorinated pools
141
How does adenovirus spread through the body?
spreads by viremia (though bloodstream)
142
What is the hallmark of adenovirus infection?
The presence of inclusion bodies without cellular enlargement
143
Clinical Diseases (dependent upon tissue infected and virus
type)
* Acute febrile pharyngitis and pharyngoconjunctivital fever
* Acute respiratory disease
* Laryngitis, bronchiolitis, pneumonia
* Conjunctivitis (pink eye, swimming pool conjunctivitis)
* Gastroenteritis
144
PICORNAVIRUSES:
RHINOVIRUSES
145
What type of virus is a Picornavirus?
It is a small, ssRNA (+) virus with no envelope and an icosahedral capsid
146
How is the Picornavirus genome structured
a linear mRNA genome
147
Where do Picornaviruses replicate and assemble?
cytoplasm
148
Why are Picornaviruses highly resistant to harsh conditions?
They can tolerate extreme pH and temperatures, making them durable in tough environments.
149
What is the primary mode of transmission for Picornaviruses?
fecal-oral route
150
true or false
Picornaviruses are lytic viruses that cause cell death
true
151
true or false
Picornaviruses infect a wide variety of tissues, showing specific tissue tropism
true
152
s53
153
What viruses are included in the Enterovirus subgroup of Picornaviruses?
* Poliovirus
* Coxsackie A virus
* Coxsackie b virus
* Echovirus
154
What virus causes the common cold among Picornaviruses?
rhinovirus
155
s54
156
What is the number one cause of the common cold and upper respiratory tract infections?
rhinovirus
157
What cellular receptor do Rhinoviruses use to attach to host cells?
ICAM-1
158
Can Rhinoviruses tolerate the environment of the gastrointestinal tract?
No, they cannot survive the GI tract.
159
How are Rhinoviruses primarily acquired?
acquired by inhalation as aerosols or by fomites
160
Where do Rhinoviruses replicate in the body?
primarily in the nose
161
Are Rhinoviruses more or less resistant than Enteroviruses?
less resistant
162
Coronavirus
163
Is coronavirus enveloped?
yes it is enveloped viron
164
What kind of genome does Coronavirus have?
ssRNA(+) virus, long and flexible helical genome
165
What gives Coronavirus its "crown-like" appearance?
Envelope glycoproteins that form club-like projection
166
Why can Coronaviruses survive in the GI tract?
Their envelope glycoproteins provide resistance to acids
167
Where in the body do Coronaviruses primarily infect?
Infect upper respiratory tract epithelial cells
168
How are Coronaviruses released from infected cells?
exocytosis
169
What temperature range allows optimal growth for Coronaviruses?
33°C to 35°C, which is cooler than body temperature
170
What is the second most common cause of the common cold?
coronavirus
171
Name two severe diseases caused by Coronaviruses.
SARS and MERS
172
60
173
What is the function of the E2 protein in coronaviruses?
attachment protein
174
Which coronavirus protein functions as a hemagglutinin?
H1
175
What does the N protein in coronaviruses do?
RNA-binding protein
176
What is the role of the E1 protein in coronaviruses?
envelope protein
177
Which coronavirus protein acts as the RNA polymerase?
L protein
