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Flashcards in Polio Deck (24):
1

General Virus Characteristics
1. Describe
2. Depend on what?
3. made of what?
4. what are they sensitive to?
5. Structure

1. Filterable agents of infectious disease
2. Depend on host machinery for their energy production and protein synthesis
3. composed on nucleic acid and protein
4. sensitive to interferon, not antibiotics
5. Protein (making up capsid), and nucleic acid (DNA or RNA)

2

Capsid Functions (4)

1. Packaging or condensation
2. protection of nucleic acid
3. transport of nucleic acid from cell to cell
4. provides specificity for attachment

3

Types of Virus Genomes

DNA(Single or Double stranded, can be circular)
RNA (+/-; segmented, single/double stranded)

4

Viral Life Cycle

Attachment
Penetration
Uncoating
Replication
Transcription and Translation of genetic info to make proteins for capsid
Assembly (maturation)
Release

5

Locations where Drugs can act against Viruses (3)

1. Prevent uncoating
2. Interfere with genome replication
3. prevent assembly of replicated virus

6

One Step Growth Curve

After infection, virus uncoats and the ability to detect infectious virus drops, so viral load goes down (eclipse period);
Then virus replicates and viral load increases

7

Routes of Viral Infection/Transmission

1. Respiratory
2. Fecal oral
3. Transcutaneous
4. Sexual
5. Mother to fetus
6. Zoonoses

8

1. When is interferon made?
2. What does it do?

1. made by a cell during/after infection with virus
2. induces uninfected neighboring cells to make new proteins that create an anti-viral state that is hostile to new virus replication; does this by breaking down mRNA and inhibiting protein synthesis

9

Types of Viral Infections
1. Acute
2. Latent
3. Chronic

1. viral load increases and then decreases; may have a late complication
2. acute episode, time in between when virus not demonstrable, then another acute episode
3. virus always demonstrable; body can't control infection

10

How are viruses detected?

1. Virus isolation, replication, CPE
2. Detect viral antigens
3. Serology (Ab to Ag)
4. Detect viral genetic information

11

7 Question Approach to Medical Virology

1. What virus is assoicated with the disase?
2. How is the virus transmitted?
3. How is the viral infection detected?
4. What is the mechanism/pathogenesis of disease?
5. Are there any anti-viral therapies for this viral infection?
6. Are there any vaccines that protect against infections with this virus?
7. Are there any long term consequences associated with infection of this virus?

12

Poliovirus
1. What kind/class of virus?
2. What kind of genome?
3. Where does it replicate?
4. What does it do to cells?
5. What is it resistant to?

1. Picornaviridae; enterovirus
2. + strand RNA in icosehedreal capsid
3. cytoplasm
4. lyses
5. pH 3.0-9.0; mild sewage treatment, temperature

13

Epidemiology: Poliovirus
1. Reservoir
2. Transmission
3. Temporal Pattern
4. Communicability
5. Incubation period

1. human (exlusively)
2. fecal-oral; oral-oral possible(usually ingested)
3. summer-fall in temperate areas; no seasonal pattern in tropics
4. probably 7-10 days before onset; virus present in stool for 3-6 weeks
5. 6-20 days; range 3-35 days

14

Poliovirus Pathogenesis
4. It is primarily what kind of virus?

1. Invades and multiplies in SI, excreted in feces
2. creates primary viremia and viral multiplication
3. Invades CNS and multiplies; has intraneural spread; --> paralysis
4. Primarily an enteric virus which occasionally invades the CNS

15

Clinical Outcomes of Poliovirus
1. What do 90-95% get?
2. What do 4-8% get?
3. What do 1-2% get?
4. What do 0.1-2% get?

1. inapparent infection without symptoms
2. minor illness without CNS involvement; may resemble URI or gastroenteritis; complete recovery
3. nonparalytic with aseptic meningitis
4. paralytic poliomyelitis: usually asymetric, sensory intact;
may recover some or all function

16

Detection of Poliovirus infection (3)

1. Isolated from throat swabs
2. isolated from multiple fecal samples
3. serology

17

1. What is the Salk vaccine?
2. What is the Sabin vaccine?

1. IM polio vaccine
2. Oral polio vaccine

18

1. How many does seroconversion occur in?
2. What does protective efficacy correlate with?
3. How long does immunity last?

1. over 95% after 3 doses of either IPV or OPV
2. seroconversion
3. probably life long (OPV)/ long lasting (IPV)

19

Oral Poliovirus Vaccine
1. Benefits (4)
2. Major Adverse Effect

1. safe and effective even in newborns; heat stable, simple oral administration, elicits powerful mucosal immunity
2. Paralytic poliomyelitis (more likely in immunodef. persons; no procedure available for IDing persons at risk of paralytic disease) usually leads to death

20

Problems with Oral Polio Vaccine

1. Vaccine associated paralytic poliomyelitis (1:1.6 million in first dose)
2. Shedding of revertants (mutated) that are more virulent can lead to contamination of local water supply

21

What is recommended for polio vaccination for children in US?

3 Dose IM regimen

22

1. What is in the oral vaccine?
2. How do revertants occur?

1. attenuated vaccines; serotypes with mutations that affect capsid integrity
2. mistakes in replication mutate the mutations back to the "correct" form, making a much stronger capsid

23

Seven Question Approach
1. What virus is assoicated with the disase?
2. How is the virus transmitted?
3. How is the viral infection detected?
4. What is the mechanism/pathogenesis of disease?
5. Are there any anti-viral therapies for this viral infection?
6. Are there any vaccines that protect against infections with this virus?
7. Are there any long term consequences associated with infection of this virus?

1. unapparent infection, can cause GI symptoms and neurological symptoms
2. fecal-oral route, or oral-oral (rare)
3. Viremia state --> CNS invasion
4. Serology
5. No
6. Live attenuated and killed virus; seroconversion and high IgG in blood stream
7. inapparent infection: life long immunity
Paralytic: may recover partial function, post polio syndrome

24

Post Polio Syndrome

People get symptoms again (paralysis) after having polio as a child and recovering; seems like the neurons "give out"