Lecture 8: Viral Structure and Replication part 2

Question 1

What are the different types of virus architecture

Answer 1

1. Cylindrical, icosahedral, complex
2. Enveloped or non-enveloped

Question 2

what Baltimore classification and architecture type do herpesviruses have

Answer 2

group 1, icosahedral and enveloped

Question 3

How does valacylovir work

Answer 3

competitively inhibits and inactivates viral DNA polymerases preventing further viral DNA synthesis without affecting normal cellular process

Question 4

what are the 3 requirements for successful viral infection

Answer 4

1. Viral inoculum of sufficient size
2. Accessible cells that are both susceptible and permissive
3. Local anti-viral defense absent or overcome- viruses often encode specific proteins that evade or mitigate immune response

Question 5

what are the viral transmission routes

Answer 5

1. Vector
2. Fecal oral
3. Maternal-fetal
4. Direct contact
5. Airborne

Question 6

how does temperature and humidity affect transmission

Answer 6

increase humidity and temperature: decrease transmission
Cold and dry: increase transmission

Question 7

the top layer of skin is __ and therefore unable to support viral replication

Answer 7

dead

Question 8

__surfaces consist of exposed live cells are the main portals for viral entry

Answer 8

mucosal

Question 9

what occurs during incubation period

Answer 9

1. Initial period before symptoms obvious
2. Viral genomes replicating
3. May or may not be transmitted during incubation

Question 10

incubation period of 30-100 days for rabies is the rationale for why __

Answer 10

vaccines can be administered post-exposure

Question 11

short incubations have replication at __

Answer 11

primary site produces symptoms

Question 12

long incubations have symptoms __

Answer 12

beyond primary site

Question 13

what is prodrome period

Answer 13

period of symptoms before those characteristics of disease

Question 14

what two things combine to cause clinical disease

Answer 14

viral replication + immune response

Question 15

what 4 things determine viral pathogenesis

Answer 15

1. Interaction with specific host cells
2. Interaction with immune system
3. Host immune response causing pathology
4. Cellular transformation

Question 16

SARS-CoV-2 spike glycoprotein specifically attach to ACE-2, highly expressed on lung alveolar epithelial cells: what concept is this

Answer 16

viral tropism

Question 17

Define susceptible

Answer 17

cell has functional receptor for given virus- the cell may or may not be able to support viral replication

Question 18

define resistant

Answer 18

cell has no receptor- it may or may not be competent to support viral replication

Question 19

Define permissive

Answer 19

cell has capacity to replicate virus- may or may not be susceptible

Question 20

what does it mean to be susceptible and permissive

Answer 20

Only cell that can take up a virus particle and replicate

Question 21

what is virulence

Answer 21

relative capacity to cause damage to host

Question 22

what is virulence determined by

Answer 22

both the host and the virus

Question 23

how can virulence be quantified

Answer 23

1. Virus titer in a host
2. Mean time to death
3. Mean time to appearance of signs
4. Measurement of fever, weight loss
5. Measurement of pathological lesions in the CNS

Question 24

what are some things that influence virulence

Answer 24

dose, route of infection, species, age, sex and susceptibility of host

Question 25

mutations in viral genes can change __

Answer 25

viral properties

Question 26

how does attenuation reduce virulence- how is it conceptual basis for viral vaccines

Answer 26

take virus and inject into not normal host- replicates and virus becomes well adapted to new host and lost ability to cause disease in normal host- but still causes an immune response