Lytic Lifestyle

Question 1

What are the physical properties of Picornavirus?

Size
Morphology
Nucleic Acid
Envelope
Tegument

Answer 1

Size: 22-30nm

Morphology: Icosahedral

Nucleic Acid: ssRNA (+ polarity)

Envelope: NO lipid envelope

Tegument: NO tegument

Question 2

Describe the pH stability of the two major groups of Picornavirus.

Answer 2

Enterovirus: Stable at pH 3-9

Rhinovirus: Unstable at pH below 6

Question 3

What are the 5 groups of Picornavirus and the conditions they cause?

Answer 3

Enterovirus: paralysis(non-polio and polio), common cold,meningitis, diarrhea,hand-foot-mouth

Rhinovirus: common cold

Hepatoviruses: hepatitis

Parechovirus: gastroenteritis, myocarditis, encephalitis

Kobuvirus: gastroenteritis

Question 4

What allows enteroviruses to be so easily transmitted by fecal-oral routes, fomites and on hands?

Answer 4

It’s capsid structure is resistant to mild sewage treatment, salt water, detergents, and temperature changes.

Question 5

The vast majority of Polio infections fall into what category?

What is this category characterized by?

Answer 5

Inapparent (subclinical) infections (90-95%). Patient is asymptomatic. Virus is recovered from throat/stool.

Question 6

Mild illness polio (4-8%) is characterized by what clinical symptoms?

Answer 6

Minor, undifferentiated febrile illness:

• Occasional URI
• Flu-like illness & gastroenteritis

Question 7

What does aseptic meningitis resulting from polio look like?

Answer 7

1. It is non-paralytic
2. Nuchal rigidity
3. Disease lasts 2-10 days and has rapid and complete recovery

Question 8

1. What percent of infections result in paralytic poliomyelitis?
2. What are the characteristic symptoms?
3. What is the primary long-term complication?

Answer 8

1. 0.1-2%
2. Asymmetric flaccid paralysis
   Affects lower extremities more
   Large mm. groups more involved
3. Residual paralysis

Question 9

How can different Picornaviruses be diagnosed through Virus Isolation (cell culture)? What are the positives and negatives?

Answer 9

1. Stool specimens and throat washings andCSF collection
2. It is sensitive and specific, but time consuming

Question 10

What other two methods are used for Picornavirus diagnosis?

Answer 10

1. Serologic testing for titers which can be 4 times higher
2. PCR

Question 11

1. Where is polio found in nature?
2. What can enhance transmission of polio?

Answer 11

1. Exclusively a human disease
2. sub-clinical infections

Question 12

1. What is the relative incidence of paralytic disesae in areas where polio is endemic?
2. How are infants protected from severe disease in endemic areas?
3. Why might paralytic disease be more common in an epidemic area similar to the U.S. in early 1900s?

Answer 12

1. Very low
2. Maternal antibody offers protection
3. Patients are older when they first encounter the virus

Question 13

What are the steps in the polio infection process?

Answer 13

1. Ig-like receptor binding
2. Endocytosis
3. Uncoating
4. Cap-free translation (+RNA)
5. Single polyprotein is cleaved into capsid proteins and non-structural (genetic) proteins
6. RdRp replication on vesicles and encapsidation
7. Viral exit from cell.

Question 14

How does poliovirus bind and insert it’s genetic material?

Answer 14

1. Binding to ICAM-1 receptor on NH2
2. Endocytosis
3. **VP1 **region on virus injects material into cell

Question 15

What avenues can we attack to treat Picornavirus infection?And the drugs used to treat them?

Answer 15

1. Virus attachment: Block receptors (Antibody & Chemical)
2. Virus entry and genome release (Peconaril)
3. Protease processing (Ruprintrivir)
4. RdRp (Ribavirin)

Question 16

1. What makes orthomyxoviruses, paramyxoviruses, and rhabdoviruses different from picornaviruses?
2. How are reoviruses different from picornaviruses?

Answer 16

1. They have a negative RNA strand
2. They have double stranded RNA

Question 17

What are the characteristics of Adenovirus?

morphology
genetic material
envelope

Answer 17

Morphology: Icosahedral capsid with penton spikes

Genetic material: dsDNA

Envelope: NO envelope present

Question 18

What diseases are produced by Adenovirus?

Answer 18

1. Respiratory
2. Hepatitis
3. Genitourinary
4. Ocular
5. Envephalitis

Gastrointestinal in children - Ad40 and 41

Question 19

1. What is the incubation period for Adenovirus?
2. How long can diarrhea last?
3. What symptoms may precede diarrhea?
4. Is Adenovirus more common in children or adults?

Answer 19

1. 3-10 days
2. 6-9 days
3. Vomiting and Fever
4. More common in children

Question 20

What are the two types of Adenovirus attachment and entry?

Answer 20

**1: **A) Viral surfing with attachment to myosin with rapid movement across surface
B) CAR receptor attachment with clathrin mediated endocytosis

2: Fusion to PIV-3 F protein and porous entry

Question 21

Describe the production and release of Adenovirus from epithelial cells.

Answer 21

1. Attaches to apical surface
2. Virus released from basal surface
3. Penton spike fiber disrupts adhesion junctions
4. Virus shed into intestinal lumen

Question 22

Where does the Adenovirus replicate? Why?

Answer 22

In the nucleus because it is a DNA virus (not all DNA viruses are nuclear but many are)

Question 23

How is gene expression more complex in Adenovirus compared to Picornavirus?

Answer 23

Introns are present and SPLICING is used extensively

Question 24

Is there an adenovirus vaccine?

Answer 24

Yes, it is routinely given upon entry into the armed forces.