Viruses Flashcards
1
Q
characteristics of viruses
A
- obligatory intracellular parasites
- contain DNA or RNA
- contain a protein coat
- no ribosomes
- no ATP-generating mechanism
2
Q
____ of diseases are viruses
A
1/3
3
Q
why can’t viruses use ATP generating mechanisms?
A
they do not have ATPases (important for production of ATP)
4
Q
what main replicative feature (used to differentiate bacteria) do viruses lack?
A
16S rRNA
5
Q
which bacteria share certain features with viruses but not other bacteria? what are these features?
A
rickettsias/chlamydias are both intracellular parasites and sometimes require a host for ATP generation
6
Q
what is meant by ‘host range’?
A
the spectrum of host cells a virus can infect
7
Q
most viruses infect only _____ of cells in ______
A
specific types, one host
8
Q
what is the specific types of cells a virus infects determined by?
A
specific host attachment sites and cellular factors (protein-protein interactions)
9
Q
what are bacteriophages
A
viruses that infect bacteria
10
Q
what is the size range of a bacteriophage?
A
20nm to 1000nm in length
11
Q
are bacteriophages specific to a certain type of bacteria?
A
yes
12
Q
what are the 3 components of a virion (fully developed viral particle)?
A
- nucleic acid
- capsid
- envelope
- spikes
13
Q
describe nucleic acid in viral structures
A
DNA or DNA can be single or double stranded, linear or circular
14
Q
describe capsid in viral structures
A
protein coat made of capsomeres (subunits)
15
Q
describe envelope in viral structures
A
lipid, protein, and carbohydrate coating on some virsues
16
Q
describe spikes in viral structures
A
projections from outer surface
17
Q
do all viruses have an envelope? does influenza virus?
A
no some do not. influenza does though - N protein.
18
Q
describe the general morphology of viruses
A
- polyhedral viruses - many sided
- enveloped viruses
- helical viruses - hollow, cylindrical capsid
- complex viruses - complicated structures
19
Q
viruses must be grown in ___
A
living cells
20
Q
how are bacteriophages grown in the lab? how can they be recognized?
A
in agar cultures of bacteria. form plaques (clear areas) around bacteriophages on agar surface
-> each plaque corresponds to a single virus; can be expressed as plaque forming units (PFU)
21
Q
how do we grow viruses in animals?
A
- embryonate eggs
- cell cultures
22
Q
how do we grow viruses in live animals using emyro’s?
A
inject virus into egg and viral growth is signalled by changes or death of the embryo
23
Q
how do we grow viruses with cell cultures?
A
tissues are treated with enzymes to separates cells
- virally infected cells are detected via their deterioration (cytopathic effect - CPE)
- continuous cell lines are used for the production of vaccine
24
Q
what are ways to identify viruses?
A
- cytopathic effects
- serological tests
- nucleic acids
25
what do serological tests include?
western blotting - reaction of the virus with antibodies
26
what does testing nucleic acids include?
RFLPs, PCR
27
for viruses to multiply...
- must invade a host cell
- must take over the hosts metabolic machinery
28
what does the viral one step growth curve include
- eclipse period
- virions released from host cell
- acute infection
29
describe the eclipse period of a viral infection
the period while the virus is replicating in the cell and before mature virions are released
30
describe the acutre period of viral infection
when virion release from the cell ramps up and before the immune response takes over
31
what are the two types of cycles for multiplication?
- lytic cycle
- lysogenic cycle
32
what is the difference between the viral lytic cycle and a viral lysogenic cycle?
lytic: phage causes lysis of cell upon rpelication
lysogenic: phage DNA incorporated into host DNa and replicates normally
33
what 5 mains steps outline the viral lytic cycle?
1. attachment
2. penetration
3. biosynthesis
4. maturation
5. release (lysis)
34
what happens during attachment?
phage attaches by the tail fibers to the host cell
35
what happens during penetration?
phage lysozyme opens the cell wall; tail sheath contracts to force the tail core and DNA into the cell
36
what happens during biosynthesis?
production of phage DNA and proteins
37
what happens during maturation?
assembly of phage DNA and proteins
38
what happens during release?
phage lysozyme breaks the cell wall
39
what lysogeny
phage remains latent
40
what term is used to describe the inserted phage DNA before it becomes a new virion?
a prophage
41
describe the lysogenic cycle
- phage DNA incorporates into host cell DNA
- when the host cell replicates its chromosomes, it also replicates prophage DNA
- results in phage conversion
42
whats phage conversion?
the host cell exhibits new properties
43
what is meany by 'specialized transduction' with regards to bacterial/viral reproduction?
when a bacteria takes advantage of a phage to spread its genes to other bacteria for reproduction
44
what does specialized transduction result in?
changes genetic properties of the bacteria
45
viral genus names end in ____
-virus
46
viral family names end in ___
-viridae
47
viral order names end in ____
-ales
48
definition of a viral species?
a group of viruses sharing the same genetic info and ecological niche (host)
49
what must a virus also have if it carries its genetic material as RNA?
reverse transcriptase
50
what must a virus also have if it carries its genetic material as DNA?
regular transcriptase (polymerase)
51
where in a bacterial cell does viral infection occur? what about euk cells?
bacteria: cytosol
euks: cytosol or nucleus
52
what are two way viruses can enter into host cells?
receptor mediated endocytosis
fusion
53
what virus enters via receptor mediated endocytosis?
pig retrovirus
54
what virus enters by fusion?
herpesvirus
55
DNA viruses ____ their DNA in the _____ of the host using _____
replicated, nucleus, viral enzymes
56
in the biosynthesis of DNA viruses, they synthesize _____ in the ____ using host cell _____
capsid, cytoplasm, enzymes
57
how are enveloped viruses released from the cell? non enveloped viruses?
enveloped: budding (endocytosis)
non: lysis
58
what kind of genome do class I viruses have?
dsDNA
59
examples of class I viruses
smallpox (poxviridae), chickenpox (herpesviridae), adenoviridae, herpes simplex, epsterin-barr
60
what 2 notifiable diseases belong to class I (dsDNA viruses)?
1. small pox - poxviridae
2. chickenpox - herpesviridae
61
what does adenoviridae cause in humans? animals?
respiratory infections in humans, and tumors in animals
62
what has adenoviridae been used for?
used for development of astrazeca vaccine against covid 19
63
is adenoviridae enveloped or non?
is a dsDNA nonenveloped
64
what kind of virus is poxviridae?
dsDNA, enveloped
65
what symptom does poxviridae cause?
skin lesions
66
what are some examples of poxviridae?
smallpox, variola virus, vaccinia, cowpox, monkeypox, camelpox
67
what is the origin of vaccinia?
unclear, no one knows for sure
68
why is it important for the variola virus genome to have inverted tandem repeats at both ends? how are these sometimes activated?
to enable circularization/insertion. sometimes triggered by UV light
69
what kind of virus is herpesviridae?
dsDNA enveloped
70
list the examples of herpesviridae
HHV-1 Simplexvirus
HHV-2 Simplexvirus
HHV-3 Varicellovirus
HHV-4 Epstein-Barr virus
HHV-5 Cytomegalovirus
HHV-6 Roseolovirus
HHV-7 Roseolovirus
HHV-8 Rhadinovirus
71
what does HHV-1 and HHV-2 causes?
cold sores and conjunctivitis
72
what does HHV-3 - varicellovirus cause?
chicken pox, is notifiable
73
what does HHV-4 causes?
lymphocryptovirus; causes mononucleosis (epstein barr virus)
74
what does HHV-8 cause?
rhadinovirus; causes kaposi's sarcoma (cancer)
75
what kind of virus is papovaviridae?
dsDNA, nonevloped
76
what is an example of papoviridae?
papillomavirus
77
what does papillomarvirus cause?
warts, can transform cells and cause cancer
78
how can HPV be implicated in cancer development?
because one of its early genes binds to p53, a well known oncogene
79
what accounts for class II viruses?
ssDNA viruses ->few human animal disease and no notifiable dz
80
what is an example of a ssDNA virus?
parvovirus b19
81
what does parvovirus b19 causes
is a childhood dz giving a red skin rash
82
what is an example of partial dsDNA virus?
hepatitis b virus, can cause jaundice
83
hepadnaviridae uses ____ to make ___ from ___
reverse transcriptase, DNA,RNA
84
virus multiples in the host cells ____ using ____
cytoplasm, RNA-dependent RNA polymerase
85
What differentiates ssRNA (+) from ssRNA (-)?
(+): sense, RNA acts as mRNa and is translated directly.
(-): antisense, transcribed to + strand before translation.
86
are reoviridae viruses notifiable?
no
87
what is an example of dsRNA virus?
rotavirus, causes infant dha
88
what are two examples of reoviridae?
reovirus, rotavirus
89
what are the notifiable dz's of ssRNA (+)?
- Poliomyelitis (Picornaviridae)
- HepatitisA (Picornaviridae)
- HepatitisC (Flaviviridae)
- WestNileVirus (Flaviviridae)
- YellowFeverVirus (Flaviviridae)
- Rubella( Togaviridae)
- Norovirus(Norwalk)
- SARSCoV-1(Coronaviridae)
-SARS CoV-2 (Special database for Covid-19)
- MERS (not notifiable in Canada)
90
what is picornaviridae?
ssRNA, + strand, nonenveloped, no membrane
91
examples of picornaviridae
enterovirus, rhinovirus, hepatitis A
92
what is an example of an entervirus?
poliovirus and coxsackievirus
93
what does rhinovirus cause
common cold
94
when looking at poliovirus, it is noted there is a poly-a tail. why is this important?
it is involved in protein synthesis in euks, implies virus may be derived from euks
95
what are togaviridae?
ssRNA + strand, enveloped virus
96
what are the two genera of togaviridae?
1. alphavirus
2. rubivirus
97
alpha virus
transmitted by arthropods, includes chikungunya
98
example of rubivirus
rubella
99
what is rubella congenital syndrome
serious dx of fetus: possible blindness or mental retardation
100
What 3 viruses are countered by the MMR vaccine given to children? What genotype does it target?
- Measles
- Mumps
- Rubella
Target A genotype, though effective against some others.
101
what are flaviviridae?
ssRNA, + strand, enveloped viruses
102
3 examples of viruses belonging to flaviviridae
1. hepatitis c
2. west nile virus
3. yellow fever virus
103
how is hep c transmitted?
blood, sex, mother to infant, needles
104
how are west nile virus and yellow fever virus transmitted?
by arthropods
105
norovirus
ssRNA + strand viruses
106
example of notifiable norovirus
norwalk virus
107
norwalk virus
cause GE which includes diarrhea and vomiting
- can affect all age groups
- more common in winter
108
coronaviridae examples
SARS Cov1, SARS Cov2, MERS
109
SARS cov1
(Severe Acute Respiratory Syndrome Coronavirus 1)
* Origin in China in January 2003. Outbreak in Canada. early 2003 (Toronto). CFR about 10%. Bats and civets as original host.
110
SARS Cov2
(disease is Covid-19)
* Origin in China in December 2019. Outbreak worldwide in 2020.
CFR about 1%. Bats likely the original host, but unclear still.
111
MERS
Middle East Respiratory Syndrome
* Origin in Saudi Arabia 2012 but has spread to several countries including the USA. CFR 36%. Camels likely the original host. No cases reported in Canada. No specific vaccine or treatments. 2519 cases between 2012 and 2020.
112
MERS and SARS relation
evolved from a distant ancestor: helps us design vxn and control spread of dz
113
what is used as target for vaccine in SARS cov2?
spike protein w/ receptor binding domain
114
what is used by BC CDC for genotyping on SARS cov2?
RdRp: RNA dependent RNA polymerase
115
ssRNA - strand notifiable dz's
* InfluenzaVirus
* Rabies
* Measles
* Mumps
* Hantavirus pulmonary syndrome
* Hemorrhagic fever (Ebola,Marburg)
116
example of orthomyxoviridae
influenza A virus: segmented genome
117
rhabdoviridae
ssRNA - strand, envloped viruses
118
example of rhabdoviridae
rabies
119
2 examples of paramyxoviridae
- measles virus (morbillivirus)(vxn preventable)
- mumps (rubulavirus)(vxn preventable)
- both are class V ssRNA -
120
what is the difference in measles and mumps genomic structure?
mumps has SH, HN, and V/P
121
