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Virology > Test 1 > Flashcards

Test 1 Flashcards

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1
Q

What is emerging disease

A

Newly recognized or evolved

expansion in an area, host, or vector

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2
Q

Relies totally upon the host cell for energy and synthesis of structural components

A

Virus - no ribosomes, mitochondria

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3
Q

Progeny infectious virus particles are called

A

Virions

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4
Q

formed by denovo assembly from components within the host cell

A

virions

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5
Q

vehicle for transmission of viral genome to next host

A

viron

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6
Q

transmission strategies

A

close contact - enveloped
resistant to environment - naked
uses arthropod
vertical - infects fetus

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7
Q

3 parts to virion

A

Nucleic Acid - RNA or DNA
Capsid - outer shell
Envelope

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8
Q

Capsid is the outer shell of a virus comprised of repeating protein subunits called

A

capsomeres

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9
Q

the nucleic acid protein assembly packaged in the viron is called

A

neucleocapsid

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10
Q

2 types of capsids

A

icosahederal or helical

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11
Q

purpose of capsid

A

cover & protect

conserve energy

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12
Q

Where is virus envelope dervirved from

A

host cell membrane

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13
Q

glycoproteins important for attachment to host cell are called

A

peplomeres

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14
Q

process where envelope is acquired is called

A

budding

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15
Q

Viral glycoportiens that project through envelope

A

spikes or peplomeres

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16
Q

fibers that project from naked virions

A

pentons

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17
Q

what is sensitive to heat, drying, detergents, and acid

A

virus envelopes

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18
Q

what are non-enveloped virus called

A

naked

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19
Q

enzymes needed for NA replication and proteins that allow take over of host cell

A

non-structural

made 1st

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20
Q

proteins that form the capsid and package the NA genome

A

structural

made last

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21
Q

3 properties of viral propagation

A

viron mediate transmission of viral NA from host to host
viral genome contains the info for initiation and completing and infectious cycle
all virus are able to establish in a host population so they can survive

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22
Q

What does the nature of viral disease depend on

A

effects of replication on host cells
response of host defense system
ability of virus to spread

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23
Q

what effects do virus have on cells

A

lysis
establish a persistent infection
transformation - neoplasia

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24
Q

viral genome always present but virons not always produced

A

latent infection

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25
virions always being produced
chronic infection
26
Since enveloped virus are sensitive to dry,heat, detergent, acid
close contact required can spread w/o killing cell host has to have both humoral and cell-mediated response to inactivate
27
naked virus capsids are resistant to dry,heat, acid, and detergents
survive in environment fomite transmission released by lysis of infected cells humoral antibody response
28
examples of enveloped virus
influenza A - helical
29
examples of naked virus
parvovirus adenovirus both icosahederal
30
T or F Viruses are acellular, small, and simple
True
31
T or F Viruses can contain both DNA and RNA
True but not both at same time
32
T or F Viruses are obligate intracellular parasite
True - they depend on host cells to produce viral proteins
33
2 general types of viral proteins are:
Structural - building blocks Later physical structure | Non-structural - Functional EARLY
34
What does viral replication depend on
release of the genome from the viron
35
What is the range of size of viruses
Pox (300nm) | Parvo (20nm)
36
What is required for the viral life cycle
genetic information in the viral genome
37
what do viral genomes produce
messenger RNA (+) or sense strand
38
where do DNA viruses replicate
nucleus of the infected cell
39
Where do poxviruses (DNA virus) replicate
Cytoplasm
40
Where do RNA viruses replicate
Cytoplasm
41
Which is smaller DNA or RNA genomes
RNA is smaller
42
Where do retroviruses replicate
RNA virus with DNA intermediate which replicates in Nucleus
43
Viral genomes encode minimal info bc:
1- genome replication and packaging 2- produce viral proteins 3 - subversion of cellular function to produce new virons
44
What are the 2 arrengments of viral nucleic acid
Monoparite - single NA molecules | Segmented - reassort rapidly
45
What do viral genomes encode
``` gene products for replication of the viral genome assembly and packing of genome regulation of replication evasion of host defense spread to other cells and new host ```
46
what do viral genomes NOT encode
ribosomal RNA or RNA translation proteins genes involved in energy metabolism or membrane synthesis telomeres centromeres
47
The synthesis of RNA molecules by RNA viruses is a unique process that ...
has no parallel in the cell
48
RNA viruses encode a _____ to synthesize new RNA genomes
RNA-dependent RNA polymerase
49
retroviruses genome have 4 coding regions
gag - group specific antigen (maxtrix protein, nucleoprotein, capsid) Pro - Protease Pol- Reverse Transcriptase and RNaseH env - envelope and receptor binding
50
What are the effects of infection with retrovirus
latent infection active infection with production of new virons cell transformed and oncogensis occurs
51
What are the steps of replicative intermediates
+ parental strand serves as a template for the transcription of of many (-) RNA strands that can be used as templates for production of new (+) stranded genomes
52
T or F If a virus contains a + strand RNA genome they are directly infectious to host cell
True - immediately translated
53
why are RNA viruses with (-) RNA genomes NOT directly infective
b/c the viron must first be acted upon by a polymerase
54
Poxoviruses use cytoplasmic factories that result in the formation of...
intracytoplasmic inclusion bodies
55
DNA viruses that mutiply in the nucleus use ____ for transcription
DNA-dependent RNA polymerase
56
T or F Replication of viral DNa is conserative
FAlse - semi-conserative with symmetrical both stands being replicated
57
Why are most DNA viruses potentially oncogenci
they contain genes capable of transforming cells
58
In the replication cycle a large mRNA called _____ is produced
pg-RNA )pre-genomic RNA
59
a cDNA copy of the pgRNA is made by
reverse transcriptase called viral RNA-dependent DNA polymerase
60
What type of protein is envelope glycoproteins that are attachment between viron and cell
Structural
61
What makes up the capsid
capsomers that are identical protein subunites
62
What is the capsid in non-enveloped virus
external layer of the viron
63
What is the envelope composed of
lipid bilayer from budding of the host cell membrane
64
virus envelope glycoproteins function to
intial attachment of virion to target cell penetration fusion cell to cell spread
65
T or F Budding or forming the envelope can result in cell death of host cell
True
66
What is the primary criteria for delineating the main viral taxa
type and character of viral genome strategy of viral replication structure of the viron (size,shape)
67
How are animal viruses differentatied and classified
``` physical and chemical properties genetic and antigenic relatedness host range cytopathology site of replication ```
68
A persistent infection of a cell in which the complete viral genome is continually present, but no infectious virus is produced except during periodic reactivations
Latent infection
69
chemical or physical agents that increase the mutation rate of DNA
mutagens
70
A state wherein the particular virus in question is permitted to replicate by the cell and produce progeny virus
Permissive
71
An infection of a cell by a virus that results in the production of progeny virus particles
Productive Infection
72
a measure of the sensitivity of the host cell to infection by presence or abscence of receptors
Susceptibility
73
The natural virus used as reference strains no mutations or variants
Wild Type
74
What are the steps of viral replication
``` attachment penetration uncoating Transcription of mRNA viral proteins Translation of viral proteins replication of progeny genomes maturation and assembly of virions release of progeny virus ```
75
Attachment occurs by
ligand on the virus and receptor on the host cell
76
Can viral infection occur without attachment
NO
77
The receptor for Foot and Mouth and Bovine Herpes 1 is
Heparin sulfate
78
The receptor for HIV is
CD-4 molecule on human T-lymphocytes
79
Receptor for rabies is
Acetylcholine receptor
80
How are viruses uptaken
Receptor mediated endocytosis fusion of the viral envelope with plasma membrane Capsid interacts with cell receptors in non-enveloped virus
81
How are fusion proteins activated
cleavage by a cellular protesase or by a drop in the pH of the enviroment
82
What are the steps in Uncoating
removal of capsid endocytic vacuole or cytoplasm requires pH drop or enzyme inhibited by antibody or modulation of pH genome ready for replication cycle or integration
83
In order for the virus to complete its replication cycle the genome needs to produce 2 major categories of products
proteins to make up its capsomeres and its envelope glycoprotiens New genome
84
What is produced and translated into viral proteins
messenger RNA
85
What mechanisms do viruses use to direct the machinery of the host cell to synthesize viral products instead of host cell products
viral mRNA takes over host cell translation machinery and viral mRNA is translated instead of the host cells
86
What happens to the host cells metabolism and protein synthesis during viral RNA synthesis
they are both shut down and only viral products are made
87
T or F Viruses have the capablility to switch genes on and off
TRUE called gene regualtion
88
how does gene regulation occur in large DNA viruses and retroviruses?
sequential waves
89
What are the 3 classes of gene expression
intermediate-early early late
90
What are early proteins
Large regulatory enzymes | Polymerases and transcriptional activators
91
What are large proteins
proteins to form the viron structure
92
T or F Replication of viral RNA is a thing unique to only viruses
TRUE
93
Explain the replication of viral RNA
transcription of RNA from an RNA template requires RNA-dependent RNA polymerase, a virus encoded enzyme that is not found in uninfected cells
94
WHat is the maturation and release of non-enveloped viruses
structural proteins of simple icosahedral viruses associated spontanoulsy to form capsomeres than capsids. More complex viruses have a packaging sequence encoded at the end of thier DNA
95
what is the maturation and release of enveloped viruses
all mammalian viruses with helical nucelocapsids mature and acquire an envelope by budding through host cellular membranes.
96
How is the viron released in non-enveloped viruses
the cell must die and lost its membrane integerity | thousand of progeny virions are released by host cell death and lysis
97
how is the viron released for enveloped viruses
plasma membrane is not breached hence thousand of virions can be shed over several hours or days without significant cell damage many are persistent infections
98
Where do exterior influenza virus shed from
apical membrane
99
where do persistent infections (retroviruses) bud from
baso-lateral membrane
100
What is unique about the viral life cycle
there are many steps that can be blocked
101
What are the stages of Multiplication or Replication
Eclipse - where the virus is taken up by cells Latent Yield Cellular
102
T or F Viruses don't like mutations
FALSE - they actually rely on mutations to live and die
103
Which strands of viruses replicate faster
virulent strands
104
What happens when high titer viremia is achieved during infection
likelihood of transmission to additional uninfected hosts is increased
105
Arboviruses use high titers as a strategy to infect new arthopod hosts who co-evolved mechanisms to what
tolerate the viral load
106
What is important for completion of viral transmission cycle, with many viruses demonstrating tropism for specific host receptors
Capacity to replicate in key tissues
107
how do viruses envade the host immune response
encoding proteins that interfere with specific host antiviral activities
108
mutations in nucleotide sequence are usually lethal for the virus but
sometimes mutation causes a survial advantage and a mutant strain is able to propgate
109
what are the common types of mutations
single nucleotide substitution called point mutations
110
What type of viruses are more stable
DNA are more stable than RNA bc they have proofreading
111
DO RNA viruses have proofreading ability
NO only DNA
112
what are host range mutations
a species jump parvo in dogs was parvo in cats 1st (1980) flu from swine to humans equine flu infects dogs now
113
what are conditional lethal mutations
replicate under specific conditions | temperatute-sensitive mutations
114
what are deletion mutations
results from a loss of nucleotides
115
what is antigenic shift
Large change due to a novel gene or change in existing one
116
what is antigenic drift
small change resulting from accumulation of point mutations (single base subsutitions)
117
T or F Antigenic changes can have changes at the phenotypic level
TRUE
118
What are the ways viruses interact with eachother
``` complementation - 1 deficient recombination - chromosomes reassorment - viral segments reactivation - nonnon-infectious phenotypic mixing - non genetic interaction ```
119
What is a cytocidal viral infection
lysis of host cells
120
what is a productive viral infection
production and release of new virons
121
what is non-productive viral infection
new virons cant be produced
122
what are permissive host cells
they support complete replication of a particular virus
123
what is non-permissive host cells
they block viral replication
124
What type of interactions are persistent and latent infection
non-productive virus cell interactions
125
What are the 4 types of changes virus have on host cell
cytocidal - death or lysis, apoptosis cytopathology - distrupt functions of specialized cells malignant changes no alteration
126
syncytium formation allows the plasma membrane to
fuse with neighboring cells
127
what are multinucleated giant cells
synctia that envades the host cell defense system
128
What happens with cell membrane fusion
fusion proteins found in enveloped viruses glycoproteins FP - are inactive but become activated by pH or protease
129
how is a syncytial recgonized
focal clusters forming like in measles and herpes
130
WHat is it called with virus absorb red blood cells
hemadsorption/hemagglutination
131
What is it called when virus distrupts the cytoskeleton leaving a rounded up apperance
cytoskeleton distruption
132
Name 3 viruses that have inclusion bodies
hepres - intranuclear adeno - multiple intranuclear pox - large intra cytoplasmic
133
WHat is a negri body
neuron infected with rabies
134
DNA viruses associated with oncogenesis are
``` marek disease (Herpes) Papilloma ```
135
WHat phase is turned on in oncogenesis
S - phase = rapid multiplication or uncontrolled growth
136
what RNA viruses associated with oncogenesis
avain leukossi feline luk Retrovirade - provirus integrade thier genome into host chromosome
137
What are the 2 ways retroviruses can cause onogenesis
enoding oncogenes | altering expression of proto-oncogenes by inserting their chromosomes
138
what are the 3 types of persistent infections
steady state infection - virus production carrier state - lysis produce new virus interference with specialized function of high differentiated cells - hormones, or immune
139
What does pathogenic mean
capable of inducing disease or lesion
140
WHat is virulence
measure of ability to produce disease in the host
141
What are the sources of virus infections
``` diseased animals persistently infected animals animal products environment reservior host and vectors ```
142
how are viruses transmitted
horizontal - between animals Direct contact - cohabition indirect contat - formites vectors
143
What is vertical transmission
``` parent to offspring in germplasm - retroviruses through egg across placenta - non-immune dams milk ```
144
what are the 2 portals of entry for viruses
respiratory tract and fecal oral
145
where are virus shed
``` respiratory route oral route fecal milk skin urogential ```
146
Respiratory tranmission
``` Flu CDV - aerosolized mucocillary clearance phagocytosis immunosuprission receptor - entry into cell impair clearence - macrophage ```
147
Alimentary tract transmission
VM - CPV, Rota ingested in contaminated food or water low pH stomach and high pH of SI mucous and persitaltic action prevent entery and remove virus
148
Skin transmission
Tramua Insect bit animal bite instruments
149
Transmission genital tract
veneral infections | herepesviruses
150
placental transmission
``` infertility if embryo killed early mummy is fetus killed kid-gestation abortion if fetus killed late gestation stillbirth if fetus is dead at term congential abnormal at term persistant tolerant infections if infected early in pregancy normal is fetus is immune ```
151
virus - host interactions
``` inapparent or subclinical - parvo in adults local - equine flu generalized - systemic sequale of primary infection - distemper persistant infection ```
152
mechanisms of disease production by virus
direct cell damage with loss of organ function cell transfomation, tumor production inflammatory response Immunosupression destorys lympocytes, and macrophages immune mediated antigen antibody accumulation
153
what determines severity of disease
``` location (swelling in brain vs skin) function (what does target cell do ) Regeneration ability (nureons cant) ```
154
local virus replication
entry, replication, lesions, shedding in organ system
155
what determines if virus stays local or spreads
presence of susceptible cells in other tissues | outcome of encounter between immune system and the virus
156
sytemic virus replication
entry, spread to other systems, shedding in several secretions and excretions
157
pathogenesis of acute viral infection
after entry at one surface virus is able to penetrate into tissue under and multiply virus spreads via lymphatics to infect regional lymph nodes - primary amplification virus spreads to blood no clinical signs virus gets to central organs spleen mass replication - fever systemic symptoms secondary virema replication in susceptible cells
158
localized infections
very rapid, immune system prevents re-infection by time of fever, sheeding is large and disease signs appear, take samples early wait days after fever to take post infection samples
159
recovery from virus
depletion of susceptible cell population | immune response - cell mediated cytotoxic response
160
control of virus infections
viral epi - study in a population helps prevent or interrupt spread of disease life cycle of virus requires excretion from animal
161
quarantine procedures
restrict movement testing of imported animals quarentine during epidemics closed herds
162
sanitation procedures
slaughter and disposal by burn or bury disposal of bedding, food, manure disinfection of housing heat treatment of animal material for feed
163
wildlife control of spread
reduce risk of exposure to domestic animals | housing, fencing, removal of wildlife and vaccination
164
vector control
reduce the spread of infection insect control in barns dipping or spraying animals destruction of breeding sites for insects
165
susceptibility is usually correlated with ___
increased levels of replication in the tissues
166
What is a major factor in determine the outcome of infection
genetic background but specific factors are not known
167
What determines resistance to different viruses
genes
168
WHat is associated with the presence of absence of a host cell receptor on target cells
susceptibility
169
What are some exapmples of host cell determinantes
transcription factors DNA replication enzymes host cell proteases
170
The immune system determines the level of susceptibility of animals to a virus by
the antiviral action of OFN or CMI
171
Does age have an effect of viruses production
yes some viruses produce more severe infections in young animals = maturation of the immune system or of specific cells
172
what role does fever play
fever inhibits the replication of many viruses and enhances the inflammatory reaction which aids in clearance of virus
173
Virus and immune systems are both shaped by the constant pressure of
the immune system to eliminate the virus
174
what drives the evolution of viruses
effort of the virus to envade the immune response - virus cant afford to be eliminated
175
how does a host change to fight off infection
host become better able to survive infection and those genes are selected for
176
Non antigen receptors influence the outcome of infection examples
interferon NK cells muco-cillary response
177
what 2 things play a vital role in inhibiting viral replication
interferons and cytokins
178
T or F viruses can turn on and off cytokins
TRUE = this enables them to direct the immune system that best suits its needs for replication
179
WHat cells are important in the clearance and inactivation of most viral pathogens
macrophages = also major target cell and resivor
180
What is importatn in preventing the inital entry of virus
Ab bc it decreased teh inital load of virus in blood
181
why is cell mediated immunity importatn in recovery
lysis of virus infected cells prevents further replication and leads to clearance from host
182
how do viruses avoid immunity
immune privelaged sites - neurons down regulation of protein expression infects cells lacking MHC to envade T-cell reponse integration of viral genome into host chromosome DNA infection of lymphocytes and macrophages non-neitralizing Ab induction of Ab which enhances infection by attaching to virus and aiding infection of macrophages
183
What is antigenic drift
mutation of viral genes by HA and N function | subtle changes but give replication advantage
184
what is antigenic shift
reassortment of viral genome | severe epidemics
185
what is virus induced immune mediated inflammatory disease
viral anitgen persits and there is continued immune response at the site of viral infection causing more extensive damage to surronding tissues
186
What is immunosuppression
viruses destroy lymphocytes resulting in immunosupression and predisposing the host to develop opportunitics infections
187
what is modular mimicry
viral anitgens does not remian but primes the immune response to produce autoimmune disease
188
What is persistant viral infection
virus remains for long time killing cells without being eleminated by host cell defence usually requies a specialized cell type to set up persistent infection
189
Examples of persistent infections
``` canine distemper and herpes feline luke, FIV, herpes, peritonitis, calici equine herpes, EIA, arteritis bovine herpes BVD, Luke PRS cholera, PRRS, circo blue tounge, visna caprine arthrisits encephalitis Mareks disease ```
190
what is important about persistant infections
can be source in population infecting new animals can reactivate and cause acute disease immunopathologic diaseas neoplasms
191
what are the general features of persistant infections
natural selection pressures minimal tissue damage difficult to control by vaccination
192
What are the 2 types of persistant infections
chronic - persistant shedding | latent - only periodic shedding or none
193
chronic virus infection
virus replicates in host to a degree then persist over time clinical disease patterns are variable shedding to enviroment ocurs
194
how do chronic infections damage the host
cytopathic effects of the virus on the cell | immunopathologic tissue damage
195
WHat is the objective of vaccination
prevent animal from developing disease if exposure to the pathogen occurs
196
T or F Vaccination prevent infection
FALSE - only primes the host immune system to respond to pathogen exposure
197
WHat is the overall objective of vaccination
Immunize as many as possible vaccinate no more than necessary vaccination only against risky pathogens
198
What is sterilizing Immunity
vaccine gives complete protection for clinical disease | No viral replication or shedding to other animals
199
What has to happen for a vaccine to be the most effective
generate the type of immune response that the natural infection would
200
What can block spread of the virus from blood and also prevent clinical disease
Serum IgG
201
what can be a reasonable estimate for the level of protection like CDV, CPV2
serum IgG
202
When is CMI more important that systemic antibody
if virus is intracellular or persistant infection
203
When do serum IgG levels NOT correlate to protection
in intracellular or presistant infections like Herpes, retroviruses, and calicli
204
What % vaccinations immunize the target species
65-98%
205
Does contagious viruses with high amounts of shedding have better protection from vaccines
Yes those vaccines protect about 98% of the time
206
Viruses that are latent infections or have sporadic shedding have high levels of vaccine protection
NO - actually have low levels of protection
207
What age animals are the target of vaccine programs
Young animals bc their are most susceptible to disease immune system matures months after birth also clinical disease is worse
208
T or F Themorulation is import when vaccinating neonates
TRUE - hypothermia permits replication of viruses that would be inhibited at normal tempature Especially Canine Herpes in puppies
209
What is the Window of susceptibility
When colostral antibody declines and neonate is exposed to virulent virus
210
Why do we vaccinate neonates multiple times
presence of colostral antibodies blocks the development of adaptive immune response and neonates remain vulnerable despite prior vaccinations
211
What makes Live viruses so different
they actually replicate in the host so they see the live virus
212
What are the 5 types of Live Viruses
``` 1 - MLV or Attenuated 2 - Cold-adapted, temp sensitive 3 - recombinant vectored vaccine 4 - deletion mutant vaccine 5 - Chimera ```
213
What are the 4 types of killed vaccines
1 - Whole virus 2 - subunit 3 - Nucleic Acid 4 - Peptide
214
Why are MLV the best type of vaccine, Most common and effective
they activate both arms of the adaptive immunity the CMI and humoral
215
How are MLV derived
passaging a pathogenic virus in tissue cultures or another species
216
If MLV are adminstered on the epithelial or mucosal surfaces they can initate
Local secretory IgA
217
What vaccine can overcome materal antibodies blockade
MLV
218
What are temp-sensitive vaccines
only replicate when temp is lower than core body temp
219
How are Recombinant vector virus derived
genes associated with protective antigens of a pathogenic virus is inserted into another virus that is NOT a pathogen but will express the pathogen virus
220
T or F Vectored vaccines will replicate in mammals
FALSE - they do NOT | canary-pox vectored vaccine for WN, distemper, FELV, Avipox
221
Why would poxviruses be particulary attractive for use in live agent recombinate vector vaccines
They replicate in the cytoplasm They are large DNA virus so there is room to insert genes They are not natural to mammals so they can't replicate to form a super pathogen
222
Advantages of Vectored Vaccines
can NOT revert to virulence or cause disease can induce robust immune response, with live non-replicating live virus (Ab&CMI) overcomes maternal antibodies Diagnostic can differentiate between natural infection and vaccine induced response
223
What is a deletion mutant recombinate vaccine
delete or inactive a gene that is required for virulence while leaving the capability to replicate intact
224
What is used to distinguish vaccinated animals from natural infections
Marker vaccines or DIVA test (distinguished from infected animal)
225
What type of vaccine is used in eradication programs
Deletion mutant recombinant vaccine
226
WHat is a chimeric vaccine
recombinatnt vaccine that contains at least one functional gen from a pathogenic closely-related virus
227
How are chimeric vaccines made
inserting a structural protein gene from a pathogenic virus into non-path vaccine strain
228
What are the advantages of live vaccines
robust immunity (CMI - sees virus) decreased potential for allergic reactions bc antigenic load is small and adjuvants are not needed long duration recombinate can overcome materal antibodies one injection gets immunity
229
when are live vaccines indicated
sistuations where antibody levels do not correlate with protection and where induction of anitbody may block effective imunological response or contribute disease
230
Disadvantages of Live vaccines
Can replicate in host - overt disease in vacc animals - acquire mutations and revert to virulence -teratogenic and/or abortions - transmitted to others very susceptible to inactivation - handle, mix store carefully
231
What are the 3 types of inactivated vaccines
non infectious whole agent - Killed Genetic vaccines - DNA plasmids, RNA mRNA Purified subunit vaccine
232
T or F inactivated viruses replication occurs in the host
FALSE - no reversion to virulence | no sheddign
233
why do inactivted killed and non-infectiour vaccines require higher antigen mass and adjuvants
hypersenstitivity reactions injection site reactions sarcomas in cats
234
Which type of vaccines are stable to store and safer for pregant and immune supporesed animals
inactivated or killed
235
What are the disadvantages of killed vaccines
require multiple doses, very frequent can NOT overcome maternal antibodies Short duration NO CMI

Virology (4 decks)

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