Virology midterm Flashcards
1
Q
Morphology of virions
A
size range: 20-300nm
Shape: high variety
Content: nucleic acid, proteint
2
Q
what is a vegetative virus
A
a virus that has infected a cell
3
Q
Reproduction of virus
A
no energy and protein synthesis, enzymes
no nucleic acid replication (by the virus itself)
enzyme multiplication 10^3 - 10^6 virion/host cell
4
Q
Occurence
A
can infect anything
active virus mulitplication in 1-3% of people
5360 accepted species
5
Q
multitude of viruses
A
200 million tons is the cumulative weight of viruses
6
Q
origin of viruses
A
suspected to have evolve from bacteriophages
7
Q
origin of viruses, theories
A
cell degeneration
runway cell components
chromosome fragment
8
Q
Virion morphology (what does it consit of)
A
core: protected by capsid, contains proteins and nucleic acids
Capsid: proteins +/-
envelope: lipid membrane + proteins
9
Q
examination methods of virions
A
electron microscopy
negative contrast staining
shadow casting
10
Q
How does electron microscopy work?
A
ultra thin sections are made
water and uraninan salt
11
Q
how does contrast staining work
A
urany acetat
12
Q
how does shadow casting work
A
gold vappour is blown onto the particles and the shadow they form can describe the shape of the virion
13
Q
what is the capsid composed of?
A
protein units
14
Q
what are the different shapes of the capsid?
A
helical quasihelical isohedral binal complex pleomorphic
15
Q
what is nucleocapsi?
A
when the nucleic acids and the capsomer are so close that they cannot be separated
16
Q
give example of a virion with helical structure
A
tobacco mosaid
17
Q
give an example of a virion with quasihelical structure
A
orthomyxo paramyxo thabdovirus ebola
18
Q
what does it mean that a virion is isohedral
A
cubic, spherical 20 equilateral triangle¨ have capsomeres and may have envelope
19
Q
what does binal structure mean?
A
isohedral head+helical tail
20
Q
pleomorphic structure?
A
no capid always enveloped shpe depends on the environment
21
Q
How do nucleic acid get purified
A
add proteinase K enzyme
22
Q
how is the nucleic acids extracted?
A
phenol + chloroform + isoamylalchol
23
Q
is chloroform and ethanol used in the lab for purification?
A
no, it is unhealthy, chromatography is used instead
24
Q
What is the name of the gel used in electrophoresis for NA purification?
A
Agarose-gel electrophoresis
25
example of segmented and continous NA thread
Continous: picornaviridae Segmented: reoviridae - 12 segments
26
Circovirus details
1.7kb single stranded nucleic acids short genome no enzymes
27
pox virus details
300 kbp many genes multiplicates without the help of cell (energy + ribosome) double stranded DNA virus
28
What does the core of a virion consist of?
Proteins and nucleic acids, protected by a capsid
29
what does the capsid consist of?
proteins
30
What does the envelope consist of , if present?
lipid membrane + proteins
31
What affects the shape of the virion?
the size of the capsid symetry of the capsid the presence or absence of the envelope
32
What are the different examination methods of the morphology of virions?
- electron microscope - Negative contrast staining - Shadow casting
33
How does electron microscopy work in examining virions?
Ultra-thin seections 0.1-0.5 um W and urania salts are used makes the inner structure of virus visible
34
How does Negative contrast staining work in examining virions?
Uranyl acetate Surface can be seen
35
How does shadow casting work in examining virions?
Au,Pt, Pi vapor Vapor is blown onto the particles and by the shadow they form their shape can be described 3 dimensional structure
36
What are the different shapes of a virion based on the capsid?
Helical Quasihelical Icosahedral Binal Complex Pleomorphic
37
Where are the nucleic acid of virion found?
in the core
38
What is the function of the viral nucleic acids
carries genetic information and determines the viral properties
39
How is the size of the niral nucleic acids
relative small, easy to handle and to investigate
40
State some general characteristics of **viral nucleic acids**
| (size, structure, chromosomes)
Carries genetic information
relatively small - easy to investigate, 3-300 kilobase
dsDNA, ssDNA, dsRNA, ssRNA
continous or segmented
Haploid - usually ( retrovirus are diploid)
41
on what kind of structure of nucleic acid can we find **positive** and **negative sense**
Single stranded
42
Give example of virus with linear and circular nucleic acids
Linear: Herpes, parvo
Circular: hepadnaviridae
43
Give example of virus with continous or segmented nucleic aicds (chains)
Continous: Herpes, picorna
Segmented: Influenza viruses, Reoviridae
44
What is meant by alien nucleic acids in ex: Retrovirus
it can contain ONC or SRC genes, which gets integrated into the host cell genome, the integration leads to the containment of these genes in the next generation cells - this can cause sarcomas or tumours in organs and is how HIV operates
45
NA defiance in virus
incomplete or defective particles
complete= everything is present, nucleic acid and capsid
Incomplete: lacks nucleic acids, these cannot multiplicate with infected cells
46
What are the steps of nuvleiv avid purification?
1. Proteinase K enzyme is introduced to open the virion capsid and release the nucleic acid
2. the nucleic acids are extracte by either
* Phenol + chloroform + isomylalchol ( not used anymore)
* Chromatography
3. Precipitate the NA with ethanol
47
How does the chromatography NA extraction work?
spesific silicon filters are used to centrifuge a the fluid and the NA will bind to the fluid
48
Why do we need to investigate the viral nucleic acids?
initially for morphology and biochemical studies: later we learned how to manipulate by genetic engineering and we can use them as vectors, marker vaccines and helps differentiate between wild and vaccine
49
How does the electrophoresis work? ( what is the name of the gels used)
The nucleic acids travels through a gel, this happens with different speed depending on the size of the nucleic acid - smaller runs faster
Gels: Agarose-gel, polyacrylamice-gel
50
What is an restriction endonuclase enzyme?
Enxyme that cleaves DNA into fragments at, or near spesific recognition sites within the molecule
51
Endonuclease within the cells and their function
they are bacterial defence enzymes which digest the NA and protect themselfs from virobacteriophage
they can recognize certain sequences - palindrome
52
What is meant by sticky or blunt end?
After restriction endonuclase enzymes has cleaved an NA it will leave an blunt or sticky end
**Sticky end**: different length, will have a part ready to attach to another nucleic acid
**Blunt end**: both pieces ends at the same position, cannot stick to other nucleic acids
53
What are restriction fragment length polymorphism used for?
* Genetic markers in physical mapping
* Identification and taxonomy
* Epidemiological investigations
* Separate between ex difference on chicken or pidgeon virus - newcastle disease
* see if the farms have the same or different disease
54
What is the role of the **viral protein?**
* protects the nucleic acid of the virus
* defense and targeting of the genome - helical tail
* shape of the virion
* enzymes for multiplication, cleaves polypeptides
* receptors, antigen
55
Southern blot?
Agarose-gel is put on a special filter (nylon) and then the direction of electricity is changed, this will cause the NA to migrate to the filter
56
In regard to grouping, what are **structural proteins?**
Surface proteins and core proteins
57
What and where are surface proteins?
Capsid or envelope
* it defines the:
* shape
* adsorption
* HA activity
* enzymes for penetration
* release of virion
* antigenicity
58
What is Core protein?
Proteins which protects the Nucleic acids and stabilizes.
Enzymes for viral multiplication
59
What two categories do we talk about regarding grouping?
Structural and non-structural proteins
60
What are non-structural proteins (grouping)
* proteins which are coded for in th viral genome but is not carried by the virion
* present only in vegetative virus - infected
61
What is the sub-group of non-structural proteins (grouping)?
Early or immidiate proteins
62
What are early or immediate proteins (grouping)?
Proteins produced following entry into the host cell, but prior to replication
Proteins of cell invading
Regulating cell
inhibit cell defense
enzymes of replication
63
What are late proteins (grouping)?
Viral protein formed after replication
* enzymes for structural maturation, cuts polyproteins
* virion particle assembling
* the majority of the late proteins are structural
64
What are some methods to investigate the proteins of the virion?
PAGE (Sds-Polyacrylamide-gel electrophoresis)
Immunoblotting - Western blot
Immunoperoxidase staining
Monoclonal antibody production
65
How does PAGE work?
(Sds-polyacrylamide-gel elecrophoresis
* The size and number of proteins will show different bend's and different number of them
* Concentrated virus suspension
* Linearization (polypeptides) -makes them linear
* The gel lies on the side, electricity passes thorugh
* staining: silver, coomassie brilliant blue
66
Why do we use PAGE?
To determine number and size of viral polypeptide
polypeptide map
We can see the characteristic of the virus
PAGE: less sensitive for drying out, long term storage of protein
67
How does immunoblotting work as a method of protein investigation?
Western blot
Nitrocellulose filter, proteins migrate to this filter
Transfer of viral proteins from PAGE into nitrocellulose filte
68
How does immunoperoxidase staining work?
after sds-PAGE and western blot the sample is put into histological sections
We are to detect antigens:
1. cover with primary AB
2. incubate, wash
3. Cover with conjugat
* peroxidase labeled AB
* spesific to the primary AB
4. Incubation, washing
5. Cover with substarte, gets digested and shows a color change
69
Why do we use immunoperoxidase staining?
it is a diagnostic methode, we identify antigens
check the mechanism and timing of protein production
epitope investigation
- Investigate the surface one by one
70
What is monoclonal antibody production?
* mAb are antibodies that are made by identical immune cells that are all clones of a unique parent cell.
* it is spesific for a particular epitope
* B-lymphocyte
1. mouse immunization with viral antigen - lymphocytes learns the antibodies and produces antigens
2. isolation of lymphocytes from the spleen - Bcells: AB production, but no mitotic division
3. mixing with myeloma cells: mitosis but no AB, type of cancer
4. fusion of cells by polyethylen glucon - tetraploid hybridoma cells
5. cloning - cultivation of the hybridomas
* Selection of the successful fusions
* HAT medium
71
How do we test the clones that we created during Monoclonal antibody production?
ELISA, IF, IPS - epitope spesific mAbs
72
What do we use mAb for?
Diagnostic of viruses, cancer treatment, and other medical use
73
What are and where are viral lipid?
Enevelope of the virus consist of 30-35% lipid
Aquired from cellular membrane structures, goligi - budding
74
How does budding work?
The virion gets out of the cell by putting a stress on the inside of the cell wall and makes a bump and takes a part of the cell membrane with them when they leave
phospholipids, cholesterol + virus spesific proteins
pox virus, ASF does this
75
What are some viral carbohydrates?
Ribose, deoxyribose - in NA
Glycoprotein - surface of virus, specific antigen, Pox has int in the core
76
What are the 6 steps of the multiplication cycle of the viruses
1. Adsorption
2. Penetration
3. Decapsulation
4. Eclipse
5. Maturation
6. Release
77
How does adsorption work in viral reproduction?
The virus attaches to the cell membrane of the host cell and injects its DNA/RNA
78
Explain cell surface receptors (adsorption, replication)
They are genetically coded
* H19 chromosome - poliovirus
* H3 chromosome - HSV
Often expressed in embryonic life/after birth
it is necessary for cellular functions
* CD4 - HIV
* acetylcholine receptor - rabies virus
79
What are virus surface antireceptors? (adsorption, replication)
Variable receptors making it possible for the virus to adapt easily to the cell surface
the viruses will adapt the cellular surface receptors during their evolution
80
Does related viruses target the seme cell surface receptors?
usually yes.
81
How is the specificity of the virus determined?
by the tissue or species of receptor proteins (virus evolution)
82
how is the releationship between receptors and antireceptors?
The negative charge between them will cause repulsion and collision happens only by chance
83
reversible vs irreversible connection (virus surface antireceptor)
reversible: cations neutralize the electrostatic power
Irreversible: chemical bonds between the proteins
84
What are the three general forms of penetration? (replication)
Translocation
Endocytosis
Membrane fusion
85
How does penetration happen in viral replication?
Energy dependent: 4x activation energy than adsorption
only in living cells
only over 4+ degrees
86
How does translocation work? (replication)
Trapdoor mechanism, amorphous RNA-protein complex
When adsorption is happening it will remove its capsid and gets flipped from outside to in (ikea spinning doors) - the transmembrane proteins turns over
87
How does endocytosis work?
this is the most common way (non enveloped viruses + herpes, pox)
cell nutrition endosome --\> phagolysosome --\> decapsidation
(the endosome gets into the cell, here the cell membrane will be start to suck and digest the capsid)
88
How does membrane fusion work?
only possible for enveloped viruses
special fusion proteins are needed
the viral envelope will mrge into the cytoplasmic membrane of the host cell
only the nucleocapsid will get into the cytosol
89
What are the steps 1-4 showing?
1. non enveloped - phagocytosis
2. trapdoor mechanism
3. enveloped, fusion of cell membrane
4. phagocytosis of the cell
90
What are the alternative forms of penetration?
Injection
sexfimbria
passive
91
How does injection work (penetration)?
Tailed bacteriophage uses this method
**lysozyme enzyme** will help with cell wall digestion and weaken a part of the bacterial cell wall before the **contractile proteins** will inject the content
92
How does Sexfimbria work? (penetration)
ribophages
Lack of cellular wall - weak points
they share nucleic plasmid with eachother
known as the bacterial sexual disease
93
Passive penetration?
Plant viruses
the cellular wall gets damaged by arthropod bites
94
What is decapsidation and why do they do it?
when the nucleic acid is released from the capsid
they do it for transcription - it is dangerous for the virus
95
Which viruses are the ones that is most easily discovered by the cell during decapsidation?
double stranded RNA viruses
96
what are some strategies used by the virus to decapsidate (uncoat)?
* Use the bodys own proteins - in lysosomes
* using viral uncoating proteins - pox
* Partial decapsulation
* simultaneous decpasidation and penetration
97
How does partial decapsulation work?
Double stranded RNA - to hide the nucleic acid until early virus protein production
The double capsid will by endocytosis have its outer membrane digested, and let the mRNA out trough little windiws
98
What happens during eclipse? (general)
transcription, translation and nucleic acid replication
there are different strategies according to the type of nucleic acid -Baltimore system is based on this
99
What happens during maturation?
the polypeptides are cleaved and cut
capsid are formed from the proteins and glycosylation
dimer formation, antigen development
this happens at the ER and golgi apparatus
100
what happens during virus assembly and where?
The capsid and nucleic acids find eachother to form the virus protein. usually happens at the site of replication
101
what can be formed during protein transport?
inclusion bodies
- intranuclear or intracytoplasmic
102
What makes the nucleic acids and capsomere find eachother during virus assembly?
Nucleic acid signal
103
How fail proof is virus assembly?
mistakes happens frequently
incomplete virus at 70%
104
What are the methods of virus assembly?
the nucleic acid enters into the capsid - icosahedral
the capsomeres surround the nucleic acid - helical
105
What regulates the virus assembly and what is needed?
Scaffolding proteins regulate
envelope and matrix proteins are acquired from cellular membranes
106
What are the two ways the virus can be released?
passive: the cell will die
active: energy is needed
107
How is the enveloped viruses released?
through Budding - it will push on the cell membrane and exit with a part of it
**rapid budding**: toagv, paramyxo, rhabdo
**slow budding**: arena, retro
108
What about the budding sites for virus release?
They are spesific
Herpes virus: at nuclear membrane
Flavivirus: ER
Coronoa, bunyavirus: Golgi
Asfar, Toga, orthomyxo, paramyxo, rhabdo: cytoplasmic membrane
109
How are cell-associated viruses released
released at cell death or injuries
110
Why does cell fuse and what is another name for it?
syncytium formation - membrane tunnels
- it is a safe way to spread
111
What are some alternative forms of virus release?
lysosome disintegration: exocytosis
The t-bacteriophage will digest the cellular wall of the bacteria
112
What are the 6 categories of the baltimore system based on
what type of nucleic acid they have and their multiplication strategy
113
What are the 6 categories of the baltimore system?
1. dsDNA
2. ssDNA
3. dsRNA
4. +ssRNA
5. -ssRNA
6. viruses using reverse transcriptase
114
What is mutation?
independent changes in the genetic material
- source of evolution
- opportunity for adaption
- risk of loosing advantages/properties
115
What is the cause of mutation?
Mistakes in NA replication - effective polymerase but no proofreading activity
116
What are the types of mutation?
* Spontaneous
* Induced:
* Irridation - UV, X-ray, atomic radiation
* mutagenic drugs - halogenated uridine
117
What are the forms of mutation?
point
sequence
substitution
insertion
deletion
inversion - frame shift
118
what are the different results of mutations
silent mutation - when there is no phenotypic change
lethal mutation - nonsense or missense
conditional lethal mutation - changes in the multiplication activity, thermo sensitive mutants
beneficial mutation: rare
119
What are some influences the mutations can have on the viral phenotype?
* antigenic change
* escape mutants
* influenxa - antigenic drift
* changes in host species specificity
* feline panleucopenia --\> canine parvoenteritis
* changes in organ specificity
* different tissue tropism
* virulence variants
* cytopathic effects, plaque formation
* temperature optimum
120
What is the story of CPV2?
* originally it only spread in small carnivores, but small changes happened and it could only infect dogs
* this new virus strain got extinct in 1979
* CPVa continoued and infected dogs (TfR adaption)
* CPV2b can infect both dogs and cats
* CPV2c appeared after some mutations and can spread from continents replacing previous types
121
Examples where mutations changed the virus organ specificity
EHV1: abortion EHV4: rhinopneumonitis
IBR: rhinotracheitis IPV: vulvo-vaginitis
122
Name some virulence variants due to mutation
* newcastle disease - differentiate between strains
* Lento: only in young chickens, slow
* Meso: young chickens, but spread faster
* Velogen: both young and old, spreads fast
* avian influenza: haemagglutinin protease cleavage site
123
some mutant viruses where the cytopathic effect or plaque formation was altered
aujeszky disease
BVDV: mild cell rounding + no cytopathich effect
124
some viruses affected by change in temperature optimum
rhinoviruses, canine herpes virus - 33 degrees
rabies vaccine strains
125
Evolution by mutation
* selective advantages
* environmental pressure
* immune system, pressure for virus
* adaption, niche
126
stabilization of virus strains
protect from mutations - low passages
seed virus, virus banks
freeze drying: 4, -80 and -196 degrees
127
With what may the virus interact with?
another virus
host cells
host organism
128
When will viruses interact?
when they are inside the same cell and are multiplying
129
Which viruses are most likely to interact?
viruses that are related
130
What are the different types of interactions between viruses
Advantageous
Disaadvantageous
Neutral
131
what is meant by advantageous interactions?
both of the interacting viruses help each other
* on a nucleic acid level:
* they will exchange characters, nucleic acid function/parts - helping the next generation - recombination
* on protein level:
* complete eachother, share capsid/surface proteins - complementation/ phenotype mixing
132
What is meant by disadvantageous interactions between viruses?
interference, one virus will inhibit the other
133
What is meant by neutral interactions?
virusexaltation, they will happily multiply besides eachoter but they dont affect each other
134
what happens with the recombination when there is viral interactions?
there may be exchange of genetic information
the effect of the nucleic acid will be inherited in the next generation giving it new properties
there must be atleast 20-40 nucleotide homology, relatated
135
What are some different ways virus can recombine when they interact?
intramolecular recombination
genetic reassortment
reactivation
phenotype mixing
interference
virusexalteration
136
what happens during intramolecular recombination when there is interaction between viruses?
the polymerase will derail during replication and mix the two genetic informations
during aujeszkys disease there is a 70% transfer
it can happen between related, and some times non-related + RNA viruses
137
What happens during genetic reassortment in regards with virus ainteractions?
When viruses with segmented genome (such as orthomyxoviridae) exchange their segments during viral assembly, and the different segments enters the wrong capsid
this causes a sudden and major antigenic change
138
How does reactivation work in regards to virus interactions?
Cross- reactivation and multiple reactivation
Cross: attenuated vaccine strain + related genes, repair of the defected virulence-genes
multiple: between two attenuated virus-strains, different defected genomic reasons
139
Why shouldnt we give different live vaccines within a short time?
because of the multiple reactivation, different parts of the genoome may be altered and when they are put together they can exchange information and correct the missing genes in the next generation
140
How does complementation work in regards to virus interactions?
it is between a defective and a competent virus.
they will exchange enzymess - where the competent virus will help the defect with multiplication
ex:
heat-sensitive mutant + wild type virus
avirulent virus + inactivated virulent virus
dependovirus + adenovirus
141
How does phenotype mixing work in regards to virus interactions?
they exhange structural proteins
eks: leukosis + sarcoma virus: aquires envelope proteins ( the sarcoma virus cannot replicate but will cause tumors, it cannot spread without the envelope protein of leukosis
**Transcapsidation:** after multiplication the polio and coxsackie virus genes will enter the wrong capsid - will only affect this generation
142
Interference in regards to virus interaction and two different ways it does interact?
one virus inhibits the multiplication of the other
Adsorption interference and heterologous interference
143
How does adsorption interference work?
there will be a competition for the same cell-surface receptors
infection by accident
can happen between related viruses or after phenotype mixing or different viruses looking for the same receptors
144
How does auto interference workj?
between complete and incomplete forms of the same virus (genome is completely missing of shorter)
* it can happen at adsorption
* Incomplete virions have shorter, or is missing genome, this means easier work for the enzymes to replicate and is chosen more often - higher mobility, polymerase affinit
145
What are defective interfering particles?
spnatneously generated virus mutants in which a critical portion of the particles genome has been lost due to defective replication of non-homologous recombination
when viruses compete for enzymes, ribosomes
146
what is the efect of autointerference?
large amounts of incomplete progeny viruses
147
How does heterologous interference work?
when two non-related virus produces proteins which inhibit the other
- herpes, adenovirus inhibit pox
**viral suppressor protein production**
148
How does virusexalteration work?
the viruses will multiplicate independently, and they will not affect eachother but
- there can be changes in the viral influence on the host cell or organism such as increased pathogenicity, and cytopathic effects will appear
149
Give some examples of virusexalttion
poliovirus + coxsackievirus in mokey: increased pathogenicity
classical swine fever virus, BVDV + newcastle disease: cytopathic affect will appear
150
What can be the extent of virus propagation
localized and/or genrealized infection
localized: only an organ or area of body
generalized: viraemia
151
What are the 7 different infectiour routes?
1. transcutaneous
2. airborne
3. oral
4. venreal
5. transplacental
6. germinative
7. iatrogenic
152
Describe the transcutaneous infection and give examples
- via the skin
due to the dead keratinized cells of the skin there needs to be a wound for the virus to enter
arthropod vectors - arbovirus
* mosquito, tick, fly, louse
Special - herpes
* conjuctiva
* latent infection
153
describe the airvorne infections and how the body defends them
- via respiratory tract, respiratory diseases (paramyxo, rhinovirus)
droplet infection - aerosol
defense
* drying out - UV light
* mucosal immunity: IgA, lymphoid cells, alv. macrophages
* temperature: polymerase activitylow at 33 degrees
* microvillis
154
Describe how the body defends against oral infections
- via the enteric system
* lysosomes in the saliva can inactivate the virus
* low pH in the stomach - affects the enveloped virus
* small intestines have digestive enzymes and bile which is a detergent
155
What viruses can cause oral infections?
mainly non enveloped
- corona cirus
reo, adeno, picorna, calici (food poisoning), astro
proteolytic enzymes sometimes actaivete virus receptors
156
How does the venereal infection happen?
urogenital tract
* sexual intercourse
* cell-associated transmission (sperm)
* sensitive viruses can spread
Herpes
pappilloma - human
hepadna: blood transufion, needles, sex
arteritis - horse semen
retrovirus - HIV
157
How does the Transplacental or intrauterine infection start?
(tolerance, abortion, mummification)
via the placenta
* Different placenta structure
* Placental artery and vein
* Age and development the outcome can be different, young, few cells, resorption can happen - abortion
* **Tolerance** - at the time of embryonic life when the immune system is developing, recognize as part of body
* **Abortion** - older, when the last embryo dies
* **Mummification** - when not all of them die, and it leads to the death of the other
* Horse herpes vs arteri: vessels of the mother and placenta, nutrition supply stopped in arteritis, see the different symptoms herpes: spread from mother to embryo through the placenta, kills the embryo, respiratory symptoms a long time ago
158
What is germinatitive infections and the different ways it can infect and whatcan influence the outcome?
- via the egg
1. Virus on the surface of the egg, will infect the chick at hatching
2. inside the egg, while the egg is beeing formed it will enter (circo, adeno, picorna, retro)
Yolk immunity may influence the outcome
159
what is latrogenic infections?
infections caused to faulty of the veterinarian
- non-sterile equipment
needle, syringe
160
Mixed form of infection?
oronasal - infleunza
161
What are the main factors influencing the result of an infection?
* susceptibility
* infectivity
* amount of viruses
* pathogenicity
* virulence
162
what does stenoxen mean?
narrow host spectrum, specificity
163
What does euryoxen mean?
infects many, low specificity
164
What are the parameters of virus infections?
* presence of infectious virions in the host
* sheding of infective virions
* clinical signs
* immune response
165
What are acute infections and their outcomes?
* after infection the virus multiplicates rapidly
* immediate virus shedding
* clinical signs are shown after a certain concentration of virus is present
* antibodies will be produced after a few days
outcome
* recovery
* death
* chronic infection
166
What are the types of chronic infections?
* latent infection
* tolerated infections
* persisting infections
* slow infections
167
what are the phases of a latent infection?
* acute phase
* initial infection, multiplication, shedding and defense by immune ssytem
* latent phase
* low level of immune response, antibodies can be detected after half a year
* reactivation:
* new immune response
* immunosuppression, pregnancy, skiing
168
What are tolerated infections?
infections at the 2nd trimester of pregnancy: which is during the self-recognition phase
the virus antigen will be regarded as own, menaing no immune response and continous shedding
169
What are persisting infections?
- african swine fever
hidden neutralizing agent, it will hide from the antibodies
constant virus concentration until end of life, different times of shedding
there will be clinical symptoms, high level of antibody and immunocomplex deposition
170
Name some hidden viruses
equine arteritis: stallion venereal tract
foot and mouth disease: lymphoid tissue
canine distemper: CNS
171
What are slow infection?
retroviruses
when it is integrated into the genome, antigenic changes
the immune system is destructed, shedding is continous
the clinical signs comes at later age
the immune response will in the begining be at a very high level, but it will in the end give up.
prions can also cause slow infections
172
What is resistance? (virus cell-interactions)
when the cell has no surface receptor for the viral attachement
173
What is the response of the innate immunity? (cell-virus interaction)
* immediate response on cellular level
* Detection of viral components:
* some viral components are easy for the cell to recognize, Double stranded RNA
* Different cascade mechanismes are initiated
* apoptosis
* interferon production
* inflammatory signalling
174
what is an interferon?
a group of signaling proteins made and released by host cells in response to the prescense of several viruses
cell-coded mediator protein
175
What is an interferon inducer?
A component which is recognised by the cell as non cell - dsRNA, RI forms
they will cause a cascade which will lead to IFN release
176
How does the interferons affect the neighbouring cells?
there will be structural changes on the cytoplasmic membrane to decrease the penetration
**L-RNase**: it will destroy all RNA within the cell (cellular and viral)
**proteinkinase**: protein production will be inhibited
177
List 3 IFN types and some properties
178
What is the timeline of interferon production?
* 2-4h after infection
* maximum after 12h
* clearance after 24h
179
Are the interferons host or virus specific?
interfoerons are not virus spesific, but they have host specificity
180
what are the problems of using interferons in therapy?
expensive
parental use, short term efficiacy
the inducers are toxic
toxic side effects
181
What is meant by latency
The virus have infected the cell, but it it is not multiplicating as it tries to get into balance with the cell. There is no virus shedding or clinical signs but host is a **carrier**
182
What is present in the virus during the latency period?
only the nucleic acid and early proteins
- episoma
- integration -provirus
183
What is meant by persistent infection?
There s virus production but there is no severe cell dammage, in this state there will be continous shedding
(flavi, retro, paramyxo)
184
What is the oncogenic effect?
When there is uncontrolled cell proliferation - no control
there is less differentiated cell forms which are less effective
tthey are not able to function effectively and can cause tumors
185
What is cellular oncogenesis?
Oncogenes are genes that has the potential to cause cancer. They wil keep the cell alive even though they are ready to induce apoptosis
186
What is the proto-oncogenes?
genes necessary for cell division and maturation, these can turn into oncogenes if they are mutated or in increased expression.
187
What are some oncogenic viruses?
DNA viruses
* papilloma
* polyoma
* adeno
* herpes
* pox
* hepadnaviridae
RNA viruses
* Retroviridae
188
What are the different types of tumor?
Benignant: limited, less invasive, less destructive (c-onc)
Malignant: invasive, destructive (v-onc)
189
How is cellular oncogenesis activated?
Virus such as retroviridae enters the cell, and will integrate DNA into the cellular genome, when this virus binds to a LTR region near a c-onc gene having a promotor activity this will:
initiated translation
C-onc gene activated: oncoprotein expression, cell proliferation
slow developing lymphatic tumors
190
Expression of the viral oncogenes
Recombination between the cellular and proviral genome - the c-onc gene will be transfered into the virus genome: V-onc
this means when the virus infects there will be quick oncoprotein production which will be the cause for fast developing malignant tumors
191
is the v-onc gene good for the virus?
no, becuase it is replacing essential genes such as the envelope protein gene
192
Viral proteins which have consequent oncogenic effect
* oncogenic DNA viruses, Hepatitis C virus
* viral modulator proteins control the cell machinery
* inactivation of cellular anti-oncogenic proteins
* activation of inflammatory proteins
* inhibition of the apoptosis (Adenoviridae)
* usually benignant tumors
193
What are cytopathogenic effects?
alterations in the morphology of cells due to virus infections
- they are usually degenerative processes
194
name 6 different direct damages of viruses on the cells?
* toxic effect of adsorption
* virus proteins inhibit cellular translation
* early proteins inhibit celullar nucleic acid transcription and replication
* viral proteins or virions are deposited in the cells
* they can damage the cytoplasmic membrane permeability, osmotic changes
* cytoskeleton depolymerisation
* expression of fusion proteins
195
How can we investigate DPEs in vitro?
usually by light microscope with or without staining
196
Will allk virus infections result in CPE?
no, the cytopathic character of a virus strain may change due to mutations
197
is the CPEs always connected to the pathogenicity of the virus?
no
ex: CSF: no CPE but pathogen
spumaviruses - obvious CPE but is an orphan
198
In what case can the most characteristic CPEs be seen?
when the multiplicity of infections are low (MOI)
199
Mention some different ways CPE can occur
they can occur independently or jointly
Different viruses may cause different CPE
CPE may vary according to the host cell
200
What are the main types of CPE?
1. Inclusion bodies
* Intranuclear inclusion bodies
* Intracytoplasmic inclusion bodies
2. Cell rounding
3. Syncytium-formation
4. lumpy cell nucleus
5. call vacuolization
6. hemadsorption
201
Describe the location and investigation if inclusion body formation
it happens at the site of the nucleocapsid assembly
it can be seen in homogenous stained cells
they will be surrounded by a halo after staining - and will shirnk after fixation
202
What causes intranuclear inclusion bodies?
Nucleus replicating DNA viruses and sometimes by RNA viruses
203
What are cowdry bodies and what do they depend on?
eosiniophilic nuclear inclusions composed of nucleic acid and proteins. The two types are dependent on the state of the synthesis of macromolecules
204
What causes intracytoplasmic inclusion bodies?
usually caused by RNA viruses and DNA viruses which can replicate in the cytoplasm
mostly eosiniphilic, rarely basophilic
205
What are some pathognomic intracytoplasmic inclusion bodies?
negri bodies - rabies
guarnieri bodies - pox
206
What is cell rounding?
the most common CPE, cytosceleton depolymerisation.
The cells loses electrolytes
207
How is cell rounding determined?
unstained: double refraction, detachemnt, shrinkage
Stained: intensive staining
208
What kind of viruses causes syncytium-formation?
exclusively formed by enveloped viruses
- alphaherpes, paramyxo, pneumo, corona
209
Why is syncytium formed?
there are fusion proteins present on the surface of the virus and they are fusogenic directly at the host cell membrane, it happens when the viruses are able to directly fuse at the cellular surface without the need of endocytosis
210
What is syncytium-formation?
when there is a fusion of an infected and non-infected cell membrane, they form membrane tunnnels to induce intracellular spread, they create multi-nucleated enlarged cells which is most often seen in lymphatic cells
211
Lumpy cell nucleus
Chromatin conglomeration, rearrangement
changed refraction
nucleus lympy disintegration
- EHV in the liver of foals, ASFV in lymphatic system
212
213
Cell vacuolisation
when small vacuoles (bubbles) are formed in the cell, depending on where they multiplicate (cytoplasm vs nucleus)
214
What is hemadsorption?
when a viral hemagglutinin is expressed ion the surface of the infected cell
215
How is hemaglutin viruses proved?
RBC are added into the culturing medium and after 30 min incubation the unbound RBC will be washed away - the infected cells will capture the RBS - paramyxo and ASFV are diagnosticed this way
216
How does the CPEs appear?
They can appear all over the cell and some of them causes focal plaque
217
Where can plaques be found?
are seen more frequently in some viruses, formd more frequently in low MOI.
syncytia are seen as plaques
I
218
How is plaque formation facilitated?
we force the viruses to form plaques by supplementing the fluid with agar gel, carboxymethyl cellulose or metrazamide. this will make the cell culture thicker and keep the viruses from swimming, forcing it to spread to neighbouring cells
219
What are the advantages of plaques?
They are easier to pick out, separate and transfer
virus purification: subsequent passages of viruses taken from singular plaques - establishments of virus strains
Virus quantification: easy to count - virus concentration
220
What are non-spesific CPEs?
morphological changes in cells independently from virus infections
they can be caused by
* againg of the cell
* alteration of the pH range of the medium
* alterations of the incubations temperature
* toxic component in the inoculum
* bacterial contamination
221
How to differentiate the non-spesific CPE
negative control
compare with the uninfected control
passage the isolate
perform direct demonstrations: PCR, IHC, ISH IF, VN
