Q4 Flashcards
(382 cards)
1
Q
How to study virus infection and disease in mouse?
A
- Mice with new receptors
- Mice with complete viral genome
- Mice that express individual viral genes
- Clonal T cell receptor
- Immune mediator deletion
- Overproduction of immune mediator
- Deletion of immune cell
2
Q
What are the two general ways of studying host response to infection?
A
- Human viruses in animals
- Animal viruses that resemble human infections
3
Q
What is viral virulence?
A
The capacity of a virus to cause disease in a host
4
Q
What are the different ways that virulence can be quantitated?
A
- Mean time to death
- Mean time to appearance of symptoms
- Measurement of fever, weight loss
- Measurement of pathological lesions (poliovirus), blood CD4+ lymphocyte reduction (HIV-1)
5
Q
For what virus infection are pathological lesions quantified?
A
Poliovirus
6
Q
For what virus infection, there is a reduction in blood CD4+ lymphocyte?
A
HIV-1
7
Q
Which of Poliovirus type I and type II is more virulent, and why?
A
Type II is more virulent, when mice is inoculated intracerebrally (5 per virus), 7 days post-infection mice start dying, and within 15 days, all the mice are dead, all type I infected mice are alive
8
Q
Two general methods for measuring viral virulence
A
- Measurement of survival
- Measurement of pathological lesions
9
Q
Which among the five viruses seen for pathological lesions had relatively the highest neurovirulence score? Which CNS parts had the highest?
A
Japanese encephalitis virus
Cerebrum, brain stem; followed by spinal cord
10
Q
Which among the five viruses seen for pathological lesions had relatively the lowest neurovirulence score?
A
Dengue
11
Q
Why can viral virulence be compared only between similar types of viruses?
A
It is a relative property
11
Q
What are the properties of viral virulence?
A
- Cannot compare virulence of different viruses
- For similar viruses, assays has to be same
- Influenced by dose, route of infection, gender, species, susceptibility of host, age
12
Q
Example of a virus that is virulent when intracerebrally inoculated but not when subcutaneously inoculated (because it cannot reach the brain)
A
Tahyna virus
13
Q
How many wild-type la crosse virus is needed to kill 50% of suckling mice when inoculated intracerebrally?
A
~1
14
Q
How many wild-type la crosse virus is needed to kill 50% of suckling mice when inoculated subcutaneously?
A
~1
15
Q
How many wild-type la crosse virus is needed to kill 50% of adult mice when inoculated intracerebrally?
A
~1
16
Q
How many wild-type la crosse virus is needed to kill 50% of adult mice when inoculated subcutaneously?
A
~10
17
Q
How many attenuated la crosse virus mutant is needed to kill 50% of suckling mice when inoculated subcutaneously?
A
> 10^5
18
Q
How many attenuated la crosse virus mutant is needed to kill 50% of suckling mice when inoculated intracerebrally?
A
~1
19
Q
How many attenuated la crosse virus mutant is needed to kill 50% of adult mice when inoculated intracerebrally?
A
> 10^6
20
Q
How many attenuated la crosse virus mutant is needed to kill 50% of adult mice when inoculated subcutaneously?
A
> 10^7
21
Q
What is the major goal of virology?
A
To determine viral and host genes that determine virulence
22
Q
How are virulence genes usually identified?
A
They are identified by mutation, a virus that causes reduced or no disease in a specified system
23
Q
What are the effects of viral virulence genes?
A
Viral replication
Invasiveness
Tropism
Modify the host defense systems
Enable the virus to spread in the host
Intrinsic cell killing effects
24
How does a virus with a mutation in gene required for virulence reproduce in a cell culture?
They reproduce well
25
How does a virus with a mutation in gene required for virulence reproduce in mouse brain?
Poor replication
26
Examples of virulence determinants that do not encode proteins
1. Poliovirus - Attenuated sabin vaccine strains - Mutation in the 5' NC region - Reducing neurovirulence
2. Mengovirus - Deletion in the long poly(C) tract in the 5' NC region - Reducing virulence
27
What are the different virus gene products that modify the host immune system?
1. Autophagy and apoptosis
2. Virokines and viroreceptors
3. Modifiers of MHC-I and MHC-II pathways
4. Complement binding proteins
28
What is the mechanism of rotavirus induced diarrhea?
During rotavirus reproduction in intestinal epithelial cells, it produces nsP4, which serves as nonstructural glycoprotein and viral enterotoxin, which inhibits the sodium-glucose luminal cotransporter, required for water reabsorption in the intestine. It also induces a PLC dependent calcium signaling pathway; increased intracellular calcium induce calcium dependent chloride secretion
29
Example of a cellular virulence factor
Trim5alpha
30
What does trim5alpha do?
Work on the viral capsid, prevents HIV-1 in old world monkeys, virions can enter but encounter block before reverse transcription
31
What is the name of anti-mir-122?
Miravirsen
32
What does miravirsen do in chimpanzees?
Reduce the yield of HCV
33
What is mir-122?
A liver specific miRNA necessary for HCV replication, which binds to its 5'-UTR
34
What are the mechanisms of cell injury by viruses
Cytolytic viruses: Cytopathic effects
Formation of syncytium: Enveloped viruses (Parainfluenza, HIV)
Apoptosis, necrosis, pyroptosis (a type of cell death primarily seen in inflammatory cells such as macrophages)
Viral inhibition of host protein and RNA synthesis; loss of membrane integrity, leakage of enzymes from lysosomes, cytoplasmic degradation
35
What is pyroptosis
Type of cell death primarily seen in inflammatory cells such as macrophages
36
Which viruses form syncytium
Enveloped viruses (HIV, influenza)
37
Mechanisms of global immune response suppression
1. Replication in one or more cells of immune system
2. Perturbation of cytokine homeostasis and intracellular signaling
3. Viral proteins acting as virokines and viroreceptors (immune modulators)
38
What cells are infected in measles infection?
DC, monocytes, thymic epithelial cells
39
How does measles manifest itself?
Reduced delayed type hypersensitivity, enhanced infection
40
What cells are infected in rubella?
Lymphoid cells
41
How does rubella manifest itself?
Persistent rubella infection
42
What cells are infected in AIDS?
CD4+ T cells, monocytes
43
How does HIV manifest itself?
Neoplasia, opportunistic infection
44
Example of a host gene that controls host susceptibility to virus
flv
45
What does the flv gene encode?
2'-5'-oligo(A) synthetase
46
Which virus does flv gene determine susceptibility to?
flavivirus
47
What is the flavivirus susceptible mice strain named, and why is it susceptible?
C3H/He; has a mutated flv gene, 100% dead
48
What is the flavivirus resistant mice strain named? Survival percentage?
C3H/RV, 50% dead and 50% alive
49
What mutation protects from HIV-1 infection?
Ccr-5 delta32 mutation
50
In what percentage of people of European descent is Ccr-5 delta32 mutation present?
4-16%
51
How was a German AIDS patient cured?
With stem cell therapy with Ccr5 delta32 mutation
52
Full form of GWAS
Genome wide association studies
53
What are some SNPS that predispose human carriers to HSV encephalitis?
UNC-93B, TLR3, TRIF, TRAF3
54
Abbreviation: TRIF
TIR-domain-containing-adapter-inducing Interferon beta
55
Abbreviation: TRAF3
TNF receptor associated factor 3
56
What viruses does IFITM inhibit
Influenza, HCV, ebola, dengue
57
Abbreviation: IFITM
Interferon induced transmembrane protein
58
Which IFITM protein controls influenza morbidity and mortality in mice?
IFITM3
59
What mutation does humans hospitalized with severe influenza have?
Enriched in IFITM3 gene mutations
60
Which mouse MHC allele has more % splenomegaly?
H-2a/a
61
Which mouse MHC allele has less % splenomegaly?
H-2a/b
62
What are elite controllers also known as?
Long-term non-progressors
63
What is understood by long term non-progressors?
Low HIV loads without anti retro-viral therapy
64
What is the reason for elite controllers?
Multiple traits responsible
65
Which MHC allele is associated with elite controllers?
Specific MHC-I allele (HLA-B57)
66
Examples of two viruses that co-infect?
HIV-1 and HSV-2
67
What does HSV-2 stimulate production of?
Antimicrobial peptides
68
What antimicrobial peptide enhances HIV infection of Langerhans cells?
LL-37 by epithelial cells
69
Mechanism of action of LL-37 to enhance HIV infection?
Upregulates the HIV-1 receptors CD4 and CCR5
70
What happens when LCM (lymphocytic choriomeningitis) is injected intracerebrally of adult mice?
It is lethal
71
What happens when LCM (lymphocytic choriomeningitis) is injected intracerebrally of infant mice?
It survives (T cell response)
72
Why are old people more susceptible to infections?
Less elastic alveoli
Weaker respiratory muscles
Diminished cough reflex
73
Why are young people more susceptible to infections?
Immaturity of immune response
74
What does immaturity of immune response also lead to
Greater freedom from immunopathology
75
Which viruses are milder at young age?
Poliovirus, measles virus, mumps virus
76
Why are some some viruses milder at young age?
Better balance between protective and pathogenic immune response
76
Why is measles 300x more lethal in developing countries than Europe, N. America?
Because of malnutrition, which leads to compromised physical barriers and immune response
77
Why was 1918 influenza pandemic lethal for young adults as well?
Lacked protective immunity which would be conferred by previous infection with related virus
78
Which viruses are more lethal in pregnancy?
Hepatitis A,B,E, influenza
79
Which virus is more common in pregnancy?
Poliovirus
80
What are the factors other than viral or host determinants that influence viral infections?
1. Cigarette smoking
2. Air pollution
3. Stress
4. Malnutrition
5. Pregnancy
6. Age
7. Male > Female
81
What are the different patterns of infection?
1. Acute infection
2. Persistent infection, smoldering
3. Persistent infection, latent
4. Persistent infection, slow
82
Example of a virus causing latent persistent infection?
HSV
83
Example of viruses causing slow persistent infection?
HIV
HTLV
Measles virus, SSPE
84
Example of a virus causing smoldering persistent infection
Lymphocytic choriomeningitis virus
85
Examples of viruses causing acute infections?
Influenza virus
Rotavirus
Rhinovirus
86
Course of a typical acute infection (Graph explanation)
X axis: Duration of infection
Y axis: Virus growth
Set a threshold level of virus required to activate adaptive immune response
Until establishment of adaptive immune response:
1. Innate defenses
2. Establishment of infection
Then:
Adaptive response
Memory
Graph two ends, entry of virus, virus cleared
87
What is an incubation period?
Initial period before obvious symptoms of disease, where virus is replicating, host is responding with cytokines of global effects, transmission of virus is possible
88
What does short incubation period imply?
Replication at primary site produces symptoms
89
What does long incubation period imply?
Symptoms beyond the primary site
90
What is the incubation pereiod of HepB and HepC?
50-150 days
91
Why are acute infections difficult/common public health problems?
1. By the time we feel ill, infection may be over
2. Serious endemics affecting millions each year (Influenza, measles, polio)
92
What are some viruses that can cause acute infections?
Influenza, polio, measles, rotavirus, norovirus, west nile virus
93
Which of influenza A,B,C cause pandemics?
A
94
Which of influenza A,B,C are mostly inapparent or cause mild upper respiratory tract illness?
C
95
Which of influenza viruses cause similar disease?
A,B
96
What is the hallmark of the influenza virus helping it evade immune system?
Antigenic variation
97
Methods of influenza transmission
1. Droplets produced by coughing, sneezing, talking
2. Direct contact with infected individuals
3. Contact with contaminated surface, touch mouth, eyes, nose
98
Uncomplicated influenza series of actions
1. Incubation period (1-5 days) depending on dose and host immune system
2. Abrupt onset: Headache, chills, dry cough
3. High fever, myalgias, malaise, anorexia
4. Fever peaks within 24 hours: 38 - 40 degrees celsius
5. Declines in 2-3 days
6. Fever gone in 6 days
7. Respiratory signs intensify with declining fever
8. Dry cough becomes productive cough
9. Cough, weakness persist 1-2 weeks
10. Virus replicates throughout the tract, depending on sialic acid receptors for the strains
11. Symptoms differ in elderly and children
99
What is the problem of diagnosing influenza with rapid lab tests?
Poor accuracy
100
Ways to diagnose influenza
PCR, viral culture, serology
influenza like illness (Ili)
Fever at least 100 degree farenheit
Cough or sore throat
No other known cause
101
What is reye syndrome?
Swelling in the liver and brain
102
What are the complications on influenza?
Primary viral pneumonia
Secondary bacterial pneumonia
Myositis (Generalized muscle pain)
Reye syndrome
Cardiac involvement
103
What is generalized muscle pain called
Myositis
104
104
What are the interventions of influenza?
Non-pharmaceutical
Vaccines
Antiviral drugs:
1. Oseltamivir (Tamiflu)
2. Zanamavir (Relenza)
3. Rimantadine (Flumadine)
104
How many episodes of diarrheal incidence each day
4.7 million
105
Reduction in diarrheal deaths for aged <5 years since 1980s
89%
106
Which enteropathogen is mostly associated with diarrheal deaths for children aged 0-59 m and to what percent
Rotavirus (28%)
107
Top 3 enteropathogens associated with diarrheal deaths of 0-59 months
Rotavirus (28%)
EPEC (11%)
Norovirus (10%)
108
Which viral agent was first shown to cause gastroenteritis?
Norovirus
109
Using what technique was norovirus first visualized in 1972?
Immunoelectron microscopy
110
When was the outbreak that got 50% of the students in Ohio affected by gastroenteritis
1968
111
Why is norovirus perfect human pathogen?
1. Highly contagious >= 18 virus particles
2. Rapidly and prolifically shed
3. Virus evolution
4. Aerosol transmission
5. Evoking limited immunity
6. Moderately virulent
112
What family is norovirus part of?
Calciviridae
113
Structure, genome and size of calciviridae
+SSRNA
Nonenveloped
7.6 kb
114
Which genogroups of norovirus affect humans?
GI and GII
115
Which GII genotype is mostly associated with humans?
GII.4
116
How do the genogroups of norovirus range?
7 groups GI, GII, GIII, GIV, GV, GVI, GVII
117
How many genotypes of norovirus are there?
~40
118
Which genogroup of norovirus is present in humans to a limited extent?
GIV
119
Can norovirus be present without diarrhea?
Yes in all ages
120
What are the settings of norovirus outbreaks
Cruise ships
Healthcare facilities
Schools
Leisure settings/hotels
121
Where do noroviruses bind?
Carbohydrates known as human blood group antigens, HbGAs
122
Who are less likely to be infected by norovirus?
Non-secretors
123
Which gut bacteria help norovirus?
HBGA+ to help cross gut-lining?
124
Where is rs601338 found?
Chromosome 19 in the alpha (1,2) fucosyltransferase FUT2 gene
125
Which is the inactive non-secretor RS601338 allele?
Homozygous A:A, resistant to norovirus
126
Which RS601338 alleles are susceptible to norovirus infection?
A:G, G:G
127
Why are non secretors less likely to have norovirus?
They do not have carbohydrate HBGAs in their gut linings for norovirus to bind
128
What are the norovirus antiviral targets?
Blood group trisaccharide A (alpha-galnac, beta-gal)
Blood group trisaccharide B
129
Factors making norovirus vaccine development challenging
1. Unknown duration of protective immunity
2. Unknown effects of pre-exposure history
3. Few human studies
4. Lack of appropriate model systems
5. Antigenic variation within some genotypes
6. Antigenic variation among genogroups and genotypes
130
How many genotypes in genogroup I of norovirus?
9
131
What is the disease burden of genogroup I for norovirus?
~10%
132
How many genotypes in genogroup II of norovirus?
22
133
What is the disease burden of genogroup II for norovirus?
70% : GII.4
10% : Other GII genotypes
134
What is the benefit of multivalent vaccine?
Broadens protection against genotypes not included in the vaccine
135
What is the norovirus vaccine?
Multivalent VLP vaccine
136
When to move to vaccine reformulation for norovirus?
Changes in GII.4 antigenicity
Changes in epidemiologically important strains
137
Most common cause of childhood gastroenteritis
Rotavirus
138
What percentage of all mortality <5 years does rotavirus diarrheal dehydration cause in developing world
~5%
139
What is the condition of rotavirus in US?
Prevaccine: 1 in 72 hospitalized, all children infected by 5 years
140
How many physician visits does rotavirus cause per year
25000000
141
How many hospitalizations does rotavirus cause per year
2000000
142
How many deaths does rotavirus cause per year
800000
143
Common features of rotavirus pathogenesis
1. Transmitted by fecal oral transmission
2. 10^8-10^10 particles/ml of feces
3. 10-100 virions
4. Infants <24 months risk of dehydration
5. Older children or reinfected adults, mild or no disease
6. Contaminated hands
7. Contaminated food
8. Virions are stable in environmental surfaces
9. Recovery complete unless electrolyte replenishment not done
10. Incubation period 1-3 days
11. Asymptomatic infections play a role in spread
12. Vomiting; 4-8 days of diarrhea, fever
144
What kind of vaccine is rotarix?
Infectious attenuated human isolate (Rotavirus)
145
What kind of vaccine is RotaTeq?
Human-bovine reassortant (Rotavirus)
146
Acute vs persistent infections
Acute - Rapid + Self - limiting
Persistent - Long term, life of host
Stable, characteristic for each virus family
Most persistent infections probably begin as an acute infection
147
What are persistent infections
Occur when primary infection is not cleared by immune response; viral genome, virions, proteins continue to be produced; viral immune modulation; occurs when cytopathic effects are absent, or host defenses are reduced, viral genomes may remain after proteins are not detected, no single mechanism
148
Give five examples of viruses which cause persistence infection.
HTLV
HIV
Hepatitis B, Hepatitis C
HSVI, HSVII
Adenovirus
Polyomavirus
Papillomavirus
Measles virus
EBV
149
Hepatitis B virus: site of persistence
Liver, lymphocytes
150
Hepatitis C virus: site of persistence
Liver
151
Hepatitis B and C virus persistence consequence
Cirrhosis, hepatocellular carcinoma
152
Example of a virus infecting cells of the immune system, and what do they infect
HIV: Macrophages, monocytes, dendritic cells, CD4+ T cells
153
Acute HBV infection characteristics
1. Main target hepatocytes
2. 95% adults, 5-10% newborns, resolve acute infections
3. Transmitted by exposure to blood (Transmission, nosocomial, sex, child birth, drug use)
154
What are the characteristics of persistent/chronic hepatitis B virus infections?
1. Hepatocellular carcinoma
2. ~350 million worldwide have chronic HBV
3. Virus is not cytopathic for hepatocytes
4. Cytopathic T lymphocytes kill infected cells
5. Fibrosis > Cirrhosis > liver failure
6. Hepatocellular carcinoma develops after 20-30 years after asymptomatic or chronic infection
155
Which antibody is not made in chronic infections of hepatitis B infection?
Anti-HBs
Anti-HBe
156
Which antibodies are made in both acute and chronic infections?
IGM anti-HBc
Total anti-HBc
157
Which antibodies are made specifically in acute HBV?
Anti-HBs
158
Which of the measures do not come down in chronic infections of HBV?
ALT in blood
HBsAG
HBV-DNA
159
What does serological testing of hepatitis B involve?
Measurement of HBV specific antigens or antibodies (Different serological markers or combination of markers)
160
Significance of anti-HBs
1. Successful vaccination against Hepatitis B
2. Person has been recovered and immune from hepatitis B virus infection
161
Significance of anti-HBc (Core antibody)
1. Previous or ongoing HBV infection in an undefined timeframe (persists for life), onset of symptoms in acute HBV
162
Significance of IgM antibody to HBc
Recent infection (<6 months). Presence = Acute infection
163
HBsAg - Negative
anti-HBc - Positive
anti - HBs - Negative
interpretation
Resolved infection (Most common)
Resolving acute infection
False positive anti HBc, susceptibe
"Low level" chronic infection
164
HBsAg - Positive
anti-HBc - Positive
IgM anti-HBc - Negative
anti-HBs - Negative
Chronic infection
165
HBsAg - Positive
anti-HBc - Positive
IgM anti-HBc - Positive
anti-HBs - Negative
Acutely infected
166
HBsAg - Negative
anti-HBc - Negative
anti-HBs - Positive
Immune from vaccination
167
HBsAg - Negative
anti-HBc - Positive
anti-HBs - Positive
Immune due to natural infection
168
HBsAg - Negative
anti-HBc - Negative
anti-HBs - Negative
Susceptible
169
Hepatitis C virus genome type
+RNA
170
Hepatitis C virus family
Flaviviridae
171
How many people worldwide and what percentage of population are infected with HCV?
185 million (2.2% of population)
172
What happens in acute HCV infection
Typical hepatitis signs or asymptomatic
173
What happens in chronic HCV infection
High level viremia
174
Hepatitis C chronic infection flowchart
Acute infection ->
i. Spontaneous resolution
ii. 60-85% chronic infection
Chronic ->
i. Stable
ii. Cirrhosis in 5-20% of infected in 25 years of infection
Cirrhosis ->
i. Slowly progressive
ii. Decompensation hepatocellular carcinoma (~7% per year)
175
How many genotypes of hepatitis C virus
7
176
What are the genotypes of HCV based on
Genomic variation
177
How many subtypes does hepatitis C virus have
> 70
178
When was HCV first identified
1989
179
What are the treatment for HCV infections?
Past-decade:
Pegylated interferon combined with ribavirin
Past 5 years:
Interferon-free direct acting antiviral (DAA)
180
Cons of pegylated interferon combined with ribavirin
Suboptimal response rates (54-56%)
Significant toxicity
181
Interferon-free direct acting antiviral (DAA) characteristics
Effectiveness >95%
Highly expensive
Short treatment course
Licensed in 2014
182
When was DAA licensed
2014
183
What are the different HCV genotypes? Why are they important?
1-6
Help determine the appropriate medication for chronic HCV
184
Which interferon free regimens are effective against all genotypes of HCV?
Sofosbuvir + declatasvir (+- RBV)
185
In what class of people was highest prevalence of HCV observed in Bangladesh?
PWID (people who inject drugs), >50% in some cities including Dhaka
186
What is the general prevalence of HCV in Bangladesh
0.2 - 0.9%
187
Prevalence of HCV in Bangladeshi blood donors
0.2%
188
What are the general properties of latent infection?
1. Viral gene products that promote productive replication are not made or found in low concentration
2. Cells harboring the latent viral genome are poorly recognized by the immune system
3. Viral genome persists intact so that productive infection can be initiated to spread infection to new hosts
189
Process of transformation
Hamster embryo -> Use trypsin to make single cells -> seed plates -> Chemically treat -> Transformed clones morphologically identified
190
What are the properties of transformed cells
Immortal: grow indefinitely (HeLa cells)
Loss of contact inhibition
Loss of anchorage dependence
Colony formation in semi-solid media
Decreased requirements for growth factors (serum)
191
What is cancer? Why does it develop?
A malignant tumor, a genetic disease.
Growth that is not encapsulated and infiltrates into surrounding tissues; replacing normal tissues
192
What do the mutations related to cancer affect?
Steps in cell communication, growth, proliferation
193
What are the sources of mutation in cancer?
Inherited
Caused by DNA damage
Environmental carcinogens
Infectious agents including viruses
194
Benefit of studying virus transformed cells?
Provides insight into molecular events that establish oncogenic potential
195
Give examples of five viruses and their associated cancer.
Adenoviridae - Various solid tumors
Polyomaviridae - Various solid tumors
Hepatitis C virus (Flaviviridae) - Hepatocellular carcinoma
Hepadnaviridae - Hepatocellular carcinoma
Papillomaviridae - Papillomas and carcinomas
Poxviridae - Myxomas and fibromas
Herpesviridae - Carcinoma, sarcoma, lymphoma
Retroviridae - Hematopoietic cancers, sarcoma, carcinoma
196
What percentage of human cancers have relation with viruses
~20%
197
Do viruses need to cause transformation and oncogenesis to replicate?
No
198
Which scientist indicated the idea that virus infection can cause cancer?
Dr. Peyton Rous
199
When did Dr. Peyton Rous removed a tumor from an english hen and injected cell-free filtrate from the tumor into a healthy chicken which developed the tumor?
Oct 1, 1909
200
When did Dr Peyton Rous get his nobel prize in physiology and medicine
1966
201
Which virus did he discover to cause cancer?
RSV
202
How many nobel prizes did RSV give rise to
2 more
203
How many feuding camps were the cancer researchers split in 1950s and what were they?
1. Led by Rous: Viruses cause cancer, no such virus found in human studies
2. Epidemiologists said exogenous chemicals, no mechanistic explanation
3. Genes internal to the cell, weak circumstantial evidence
204
Examples of viral transformation of cells
Most infected cells die, but rare cells do not, are transformed
i.e.
1962: Rare BHK21: Polyoma: Changed shape, kept growing
1964: Swiss 3T3 cells: SV40: Rare cells grew as colonies
205
How can a viral infection transform a cell?
1. Cytopathic effects must be reduced or eliminated so the infected cell does not die
2. Viral replication must be reduced or eliminated so the transformed cell does not produce virions
3. The cell must continue to divide so that it becomes immortal
206
What happens to the viral genome
in transformed cells?
1. Some transformed cells contain all or parts of viral genomes integrated into the host genome
2. Sometimes no viral nucleic acid remain in the transformed cell
3. Key, but mystifying early observations
207
Who discovered Avian Leucosis Retroviruses ALV and when?
1908, Ellerman and Bang
208
What virus is most chickens infected with within a few months of hatching?
Avian Leucosis Retrovirus
209
What percentage of ALV infected chickens develop leukemia and what age
3%, >14 weeks
210
What happens to 97% of ALV infected chickens
Develop transient viremia, not leukemia, become immune
211
What does the leukemia lead to in ALV infected chickens when they age?
Connective tissue tumors or sarcoma (solid tumor)
212
What happens if virus isolated from solid tumors that are derived from leukemia is inserted into a healthy chicken?
Solid tumors
213
Example of a virus isolated from solid tumors that are derived from leukemia. What is their state mostly?
Rous Sarcoma Virus
Defective, cannot replicate independently
214
What was different about the viral genomes isolated from solid tumors from that of ALV that allowed them to form solid tumors but not ALV?
A piece of the ALV genome was replaced with the host DNA (oncogene) named v-SRC (recombination)
215
Which gene allows rous sarcoma virus to form solid tumors but not ALV?
v-SRC
216
Who identified the oncogene v-SRC and when?
J. Michael Bishop and H. Varmus, 1976
217
When did J. Michael Bishop and H. Varmus gain nobel prize for their discovery of v-SRC
1989
218
What happens to ALV infected chickens if you let them age?
They develop rare tumors, each time with retroviruses derived from ALV, but each different, and most defective
219
The retrovirus genomes isolated from each new solid tumor
had different host DNA, NOT the v
--‐SRC gene found in RSV
220
What are the structures of typical progenitors of avian transducing retroviruses and mammalian transducing retroviruses?
Avian leukosis virus: gag, pol, env
Murine leukemia virus: gag, pol, env
221
Defective vs non-defective virus
Defective viruses require helper viruses to produce more virus
Usually missing envelope proteins
Envelope genes deleted during oncogene capture
PRC II avian sarcoma virus require avian leucosis virus as helper, due to gene fps
222
How many proto-oncogenes are identified
>60
223
How does the nomenclature of proto-oncogenes go
Normally cellular genes are abbreviated with a c in front of the name, i.e., c-ONCS, c-SRC, c-MYC, c-MOS, c-RAS
224
Altered copies of c--ONCS isolated from retroviruses of tumors are named like
v-ONCS, v-RC, v-MYC, v-MOS, v-RAS
225
Who discovered the first oncogenic DNA virus and when?
Richard Shope, 1933
226
Which was the first oncogenic DNA virus discovered?
Papillomavirus that caused warts or papillomas in cottontail rabbits
227
Who discovered murine polyomaviruses and when?
Ludwig Gross, 1953
228
What is the natural host of polyomavirus and what does it do under certain conditions?
Mouse, cause rare tumors under certain conditions
229
How is polyomavirus in mouse
Ubiquitious, no role in mouse cancer
230
Where does polyomavirus cause tumors
Tumors of many tissues (polyomas) in infant hamsters, rats, rabbits
231
What did Eddy and Hilleman show in 1962?
They showed that SV40, a contaminant of early poliovirus vaccines, induced rare tumors in newborn hamsters
232
Which virus was early poliovirus vaccines contaminated by
SV40
233
What is the natural host of SV40
Monkey
234
SV40 transforms monkey cell in culture, True or False?
False
235
In which animal does SV40 cause cancer?
Rats and hamsters
236
SV40 in mouse
Non-permissive
237
SV40 in monkey
Permissive
238
Mouse polyomavirus in mouse
Permissive
239
Mouse polyomavirus in monkey
Non-permissive
240
What is the rate of polyomaviral transformation of cultured cells
1 in 100,000
241
Does adenovirus cause tumors and transformation of cultured cells?
Very rare events like polyomavirus and papillomavirus
242
Does adenovirus cause cancer in humans
No despite many human serotypes
243
How many tumors does adenovirus add in hamsters?
12-18 tumors
7-11 poorly tumorigenic
244
What are the properties of T antigens?
1. Required for replication
2. Activate viral transcription
3. Required for viral DNA synthesis
4. They are the only viral genes always retained in tumor cells or transformed cells
5. Can alone transform cultured cells
6. They are encoded by essential viral genes
245
T antigens found in SV40
Large T, small T
246
T antigens found in polyomavirus
Large T, middle T, small T
247
Papillomavirus T antigen encoded by
E5, E6, E7 genes
248
T antigens found in adenovirus
E1A, E1B
249
What are the three cellular proteins that are involved with T antigen to produce transformed cells?
1. p53 (53 kDa cell protein) binding SV40 T antigen
2. Retinoblastoma protein (Rb) binding E2F
3. Transcription of a set of adenovirus early genes (E2 gene cluster) require E2F cell proteins
250
Why is transformation rare?
It requires two low probability events to occur simultaneously.
1. Lethal late genes must not be expressed
I. Rare spontaneous deletion of late genes must occur
II. Virus infects semi-permissive cells where late gene expression is blocked
2. T antigens must be on constitutively and transmitted to every cell
i. Viral DNA encoding T antigen must be incorporated in host DNA
ii. T antigen must be produced
251
What is the proven best defense against viruses?
Vaccines
252
How are vaccines the proven best defense against viruses?
They mobilize the host immune system to prevent virus infection (immune memory).
They break the chain of transmission
253
Who developed the first vaccine that we know of and when
Edward Jenner, 1796; smallpox
254
What vaccine did Pasteur develop and when
Rabies vaccine, second vaccine developed; 1885
255
Who introduced the term vaccination and what was its origin
Pasteur, vaccination from vacca (Latin, cow) in honor of Jenner
256
When was yellow fever, influenza vaccines developed
1930
257
Name two viruses that underwent large scale vaccination campaigns
Polio, measles
258
Inactivated vaccine vs oral vaccine for polio
Oral more effective
259
Why are many childhood diseases rare?
Because of immunization
260
What is a major part of the first world's public health measure, but not the third world's
Vaccines
261
How does vaccination work in the real world?
They work via Herd immunity: Maintenance of a critical level of immunity in the population
262
What does herd immunity imply?
Virus spread stops when the probability of infection drops below a critical threshold
263
What does the critical threshold in herd immunity depend on?
It depends on the virus and the population
264
What percentage of the population needs to be immunized to get herd immunity for smallpox
80-85%
265
What percentage of the population needs to be immunized to get herd immunity for measles
93-95%
266
What percentage of population is immune from measles when 80% is immunized with measles vaccines?
76%
267
How to make a vaccine?
1. Induction of an appropriate immune response (Th1 or Th2)
2. Vaccinated individuals must be protected against disease caused by the virulent form of the specific pathogen.
Just getting a response isn't enough (producing antibodies)
268
What are active and passive vaccination?
Active: Long term protection (Instilling into the recipient a modified form of the pathogen or material derived from it that induces immunity to disease)
Passive: Short term protection (Instilling the products of the immune response [Antibodies or immune cells] into the recipient
269
What are the requirements of an effective vaccine?
1. Safety: no disease, minimal side effects
2. Induce protective immunity in the population
3. Protection must be long-lasting
4. Low cost (<1 dollars, WHO), genetic stability, storage considerations, delivery (oral vs needle)
270
What are the five stages of vaccine development?
1. Preclinical (Lab studies animals) : Number of doses, local application, immune response
2. Phase I (Tens healthy adults): Safety, minimizing adverse effects, potential risks
3. Phase IIa (Hundreds target people): Side effects, immunogenicity
4. Phase IIb/III (Thousands target people): Effectiveness, immunogenicity
5. Phase IV (Hundreds of thousands): Safety monitoring, potential adverse effects
271
What are the types of coronavirus vaccines?
1. DNA/RNA
2. Protein subunit
3. Viral vector
4. Live attenuated
5. Inactivated
272
How do DNA/RNA vaccines work?
Uses DNA or RNA molecules to teach the immune system to target key viral proteins
273
Example of DNA coronavirus vaccine?
Inovio
274
Advantages of DNA/RNA vaccine?
Easy and quick to design
275
What is live-attenuated vaccine?
Uses a weakened version of the actual virus
276
What is inactivated vaccine?
Uses the whole virus after it has been killed with heat or chemicals
277
What is a subunit vaccine?
Uses a piece of a virus's surface to focus our immune system to a single target
278
What is a viral vector vaccine?
This approach takes a harmless virus and uses it to deliver viral genes to build immunity
279
What is the advantage of using viral vector vaccine?
Live viruses tend to elicit stronger immune response than dead viruses or subunit vaccines
280
Existing examples of viral vector vaccines
Ebola, veterinary vaccine
281
Disadvantage of using viral vector vaccine
Important to pick a viral vector that is truly safe. An immune response to the viral vector could make the vaccine less effective.
282
Group testing viral vector vaccine for Covid-19
Johnson and Johnson
University of Oxford and Astrazeneca
Cansino Biologics
283
Advantage of using subunit vaccine
It focuses your immune response on the most important part of the virus for protection and it cannot cause infection
284
Disadvantages of using subunit vaccine
It may not elicit a strong immune response and other chemicals may need to be added to boost long term immunity
285
Existing examples of subunit vaccine
Pertussis
Hepatitis B
Human Papilloma Virus
286
Existing examples of inactivated vaccine
Poliovirus
287
Existing examples of live attenuated vaccine
Measles, mumps, rubella, chickenpox
288
Advantage of using inactivated vaccine
Safe because virus is already dead and easy to make
289
Advantage of using live attenuated vaccine
Stimulates a robust immune response without causing serious disease
290
Disadvantages of using DNA/RNA vaccine
Never been done before. No licensed DNA or RNA vaccine currently in use.
291
Disadvantages of using live attenuated vaccine
May not be safe for immunocompromised individuals
292
Disadvantage of using inactivated vaccine
Not as affective as a live virus. Some previous inactivated vaccines have made the disease worse. Safety for the novel coronavirus needs to be shown in clinical trials.
293
Group testing live attenuated vaccine for Covid-19
Codagenicx
Indian Immunologicals Ltd.
294
Group testing inactivated vaccine for Covid-19
Sinovac
Sinopharm
295
Group testing subunit vaccine for Covid-19
Novavax
AdaptVac
296
How can we inactivate a virus?
Chemical procedures like formalin, nonionic detergent, beta-propriolactone
297
What is the special feature of inactivated vaccines?
Infectivity is eliminated but antigenicity is not compromised
298
What is an example of an inactivated vaccine?
Inactivated poliovirus vaccine IPV
299
How was IPV made?
Treated with formalin to destroy infectivity
300
History of IPV
1954: National Foundation for Infantile Paralysis sponsored clinical trials of Jonas Salk's IPV, 1,800000 children
>50% protection, results were released on 12 April, 1955, licensed the same day
Cutter incident: Wrongly inactivated virus, caused polio, many people died
301
How many people die in the US per year for influenza?
3000-49000
302
How are inactivated influenza vaccines made?
Virus grown in chicken embryonated eggs, formalin-inactivated or detergent or chemically disrupted virions.
Or vaccine produced in cell culture avoids egg allergies (flucelvax)
303
How many doses of influenza inactivated vaccine are manufactured each year in the US?
75-100 million
304
How effective is inactivated influenza vaccine?
60% effective in individuals <65 years
305
What does the protection by inactivated influenza vaccine correlate to?
Correlates to serum antibodies to HA, NA
306
How are subunit vaccines?
Could be recombinant or non-recombinant.
Non-recombinant:
Break the virus into components (fractionation), purify the components, and immunize with purified components
Recombinant:
Clone the viral gene encoding the desired antigen (which is usually a capsid or membrane protein), express the gene in bacteria, insect cells, cell culture, yeast, purify the protein and that would make the subunit vaccine
307
What are the advantages of a modern subunit vaccine?
Recombinant DNA technology
No viral genome or infectious virus
308
What are the disadvantages of a modern subunit vaccine?
Poor immunogenicity
Expensive
Injected
309
How is HBV subunit vaccine produced?
HbsAg protein produced in yeast and they assemble into empty particles
310
Which protein is targeted to make Human Papilloma virus subunit vaccine?
L1 major capsid protein
311
Where is the gene for L1 major capsid protein inoculated for making subunit vaccine?
Recombinant yeast or baculovirus
312
For what HPV types does Gardasil (Merck) make vaccines?
6,11,16,18
313
For what HPV types does Cervarix (GlaxoSmithKline) make vaccines?
16,18
314
Where are the Gardasil (Merck) HPV vaccines grown?
S. cerevisiae
315
Where are the Cervarix (GlaxoSmithKline) vaccines grown?
Insect cells
316
What are the common problems for inactivated and subunit vaccine?
Pure proteins often requires an adjuvant to mimic inflammatory effects of infection
They do not send danger signals to the immune response
Viral proteins don't replicate or infect
317
How do adjuvants produce a more robust acquired immune response with less antigen?
Stimulate inflammation
Slow release of antigen at the site of inoculation
318
What can stimulate early processes in immune recognition?
Adjuvants
319
What kind of adjuvant is MF59?
Squalene water-in-oil emulsion (depot, innate stimulatory), Europe
320
What kind of adjuvant is alum?
Aluminum hydroxide/Aluminum phosphate used in HBV, US
321
What kind of adjuvant is AS04?
In cervarix
alum, monophosphoryl lipid A, TLR4 ligand, US
322
How are live attenuated vaccines made?
Virus replicates, stimulates immune response
Infection causes mild or inapparent disease
323
The graph for the live vs killed vaccine; features of killed vaccine
Three doses
324
The graph for the live vs killed vaccine; features of live vaccine
Initial dose, amplification of injected dose
325
What was mRNA technology originally developed as?
Cancer therapy
326
How the Pfizer-BioNTech vaccine works?
1. Scientists take the genetic sequence of the spike protein and synthesize an mRNA sequence, instructions that the cells can use to produce spike protein
2. Synthetic mRNA is packaged in a lipid nanoparticle that delivers the instructions into the cell
3. Once inside the cell, the cellular machinery follows the instructions to produce the viral protein, displayed on the surface of the cell and stimulates an immune system response
327
Which among the DNA and RNA vaccines manufacturing require cells or animal substrates
DNA virus
328
Amplification (Number of protein antigen molecules per molecule of mRNA delivered) ranking for live attenuated vaccines, DNA vaccines, RNA vaccines, protein subunits or inactivated vaccines
Live attenuated > plasmid DNA > mRNA > protein subunits/inactivated
329
How is the immuno-stimulatory effects of plasmid DNA compared to mRNA vaccines?
Fewer and better defined
330
Regulatory concerns of integration of RNA vaccines
theoretically should not integrate if no endogenous retroviruses or retroviruses due to infection are present
331
Which among DNA and RNA virus vaccines need to enter the nucleus
DNA
332
How can immunostimulatory effects decrease potency of mRNA
Decreased stability of mRNA
Decreased translation into protein
Effects upon desired type of immunity
333
Why is formulation needed for mRNA vaccine?
This observation is based upon the use of formulations by the majority of mRNA entities in clinical trials
334
Why may finding the optimal formulation/ delivery device be challenging for humans?
Unpredictability of animal models
335
What is known to cause toxicity in RNA based drugs?
Unnatural modified nucleoside analogues
336
How can the concomitant administration of other drugs influence the potency of mRNA vaccine?
It may impact mRNA metabolism and thus decrease the potency
337
Which vaccine would have a therapeutic effect after an individual is already infected?
Rabies
338
What is our second arm of antiviral defense
Antivirals
339
How long has antiviral research spanned and what is the number of antivirals available in the US market
50 years
30 antivirals
340
What are the maximum number of antivirals against
HIV and herpesviruses (persistent infections)
341
Targets of antivirals for HIV infection
DNA polymerase
Reverse transcriptase
342
Targets of antivirals for herpesvirus infection
DNA polymerase
343
Targets of antivirals for influenza A infection
virion uncoating
viral neuraminidase
344
Targets of antivirals for influenza B infection
viral neuraminidase
345
Targets of antivirals for hepatitis C virus infection
Inosine monophosphate dehydrogenase
346
Targets of antivirals for respiratory syncytial virus (RSV) infection
Inosine monophosphate dehydrogenase
347
Why are there so few antiviral drugs?
1. Compounds interfering with virus growth can adversely affect the host cell, as side effects are common which is unacceptable and every step in viral life cycle engages host functions
2. Many medically important viruses cannot be propagated, have no animal models or are dangerous
i.e., Lassa, smallpox, HBV, HPV, norovirus, ebola
3. A compound must block the virus replication completely, has to be potent, that makes drug discovery expensive, as partial inhibition may give rise to resistant mutants
4. Many acute infections are of short duration and thus by the time the patient feels ill, it is too late to impact clinical disease. The drugs in this case must be given early in infection or injected prophylactically to populations at risk, which gives rise to safety issues, and giving drugs to healthy people is not wise. Moreover, lack of rapid diagnostic reagents has hampered the development of antiviral drugs. No broad spectrum antiviral agents are currently available.
348
Which medically important viruses cannot be propagated?
Smallpox, ebola, lassa, HPV, HBV, norovirus
349
When did the first modest search for antiviral drugs occur?
Early 1950s
350
What did the chemists target in the first modest search for antiviral drugs?
They looked at derivatives of sulfonamide antibiotics
Synthesis of thiosemicarbazones active against poxviruses
351
When did the blind screening programs to find chemicals with antiviral activity begin?
1960s and 1970s
352
How was the blind screening programs spurred on?
Successes in the treatment of bacterial infections with antibiotics
353
What is blind screening for antiviral discovery?
No attempt to focus discovery on a virus or virus-specific mechanism
Random chemicals or natural product mixtures are tested for ability to block replication of a variety of viruses in cell culture systems
354
What are hits in blind screening for antiviral discovery?
Compounds or mixtures that can block viral replication in-vitro, which are purified and fractions tested in various cell cultures and animal models for safety and efficacy
355
What are leads in blind screening for antiviral discovery?
The compounds (hits) that are modified systematically by medicinal chemists to reduce toxicity, increase solubility, and bioavailability and to improve other pharmokinetic properties
356
Which antiviral was approved in late 1960s for treatment of influenza A which is one of the three antivirals for the virus?
Symmetrel (amantadine)
357
When was the mechanism of action of Symmetrel deduced?
1990s
358
What are the strategies today for antiviral discovery?
1. Blind screening procedures are dead
2. Recombinant DNA technology and sophisticated chemistry make targeted discovery possible
3. Modern technology allow inhibitors to be found even for viruses that cannot be propagated in cell cultures
4. Life cycle of most viruses known, targets for intervention can be generalized
5. Essential virus genes cloned, expressed in genetically tractable organisms, purified, and analyzed in atomic detail
359
What are the main targets of antiviral drug discovery?
Influenza (NA inhibitor, entry inhibitor)
HIV (Fusion inhibitor, protease inhibitor, nucleoside-non-nucleoside analogs)
HCV (Protease inhibitor, interferon, nucleoside-non-nucleoside analog)
Herpesvirus (Nucleoside-non-nucleoside analog)
360
How does symmetral (amantadine) work
It interacts with influenza virus M2 protein (ion channel) and blocks the entry of the protons into the virion and prevents uncoating
361
How do inhibitors of NA (Oseltamivir-Tamiflu, Zanamivir- Relenza) work?
They are designed to mimic natural ligand (sialic acid), and the closer the inhibitor is to the natural ligand, the less likely the virus will mutate or change to avoid binding drug as it would lose its viable function
362
Which among Tamiflu and Relenza more closely resemble sialic acid?
Relenza
363
What are the targets for intervention of HIV replication?
Virion assembly, release: Protease inhibitor
Cell attachment, fusion entry: CD4 derivatives, chemokine analog, SU/V3 loop inhibitors
Reverse transcription: Nucleoside analogs, nonnucleoside inhibitors
Integration: Integrase inhibitors
Transcription and post-transcriptional processing: Tat inhibitor
364
AZT
Azido-deoxythymidine (First HIV drug) is a nucleoside analog drug which was initially discovered during screens for anti-tumor cell compounds, they are phosphorylated to active form by kinases, and works in chain termination, not good substrates for most cellular polymerases, better for HIV-1 RT. But, it has substantial side effects (unlike acyclovir). Half life is 1 hour (degraded by liver enzymes), it can be given orally, absorbed rapidly. Patients need 2-3x dose daily, multidose regime give rise to resistant mutants.
365
NNRT1
Non-nucleoside HIV-1 RT inhibitors
It targets away from the active site, but it works in a way so the reverse transcriptase does not work
366
What is an example of a HIV-1 protease inhibitor?
Peptidomimetic
367
What is a key finding that helped in the development of HIV-1 protease inhibitor?
HIV protease recognizes and cleaves small synthetic petides
368
Example of a CCR5 inhibitor
Maraviroc
369
Example of a HIV fusion inhibitor and when was it licensed
Fuzeon, March 2003
370
What is the composition of HIV fusion inhibitor
36 aa synthetic peptide
371
How does HIV fusion inhibitor work
It binds to the transmembrane subunit of viral glycoprotein and blocks the transition into fusion active conformation
372
Problems with HIV fusion inhibitor
Resistance can grow by amino acid changes in the peptide binding site of the TM
Very expensive (25000 USD/yr)
Must be injected
373
What is combination therapy?
It targets different mechanisms and one pill can contain three inhibitors
HAART: HIV can be treated as a chronic disease
374
Pathological lesions graph:
Japanese encephalitis virus
C-100
B-100
S-80
375
Pathological lesions graph:
Yellow fever virus 17D strain
C-82
B-72
S-42
376
Pathological lesions graph:
West Nile Virus
C-75
B-95
S-40
377
Pathological lesions graph:
Langat virus
C-100
B-60
S-30
378
Pathological lesions graph:
Dengue virus
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