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Flashcards in Introduction to Virology Deck (14)
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1
Q

What are the 3 types of capsid symmetry exhibited by viruses?

A
  1. helical/tubular- most have an outer envelope (measles); RNA
  2. Icosahedral– isometric/cubic; envelope (herpes) and no envelope (adenovirus)
  3. Complex- doesn’t fit into other two groups (vaccinia/smallpox)
2
Q

What 4 factors is virus classification based on?

A
  1. type and structure of the iral nucleic acid
  2. strategy used in replication
  3. type of symmetry of the virus capsid
  4. presence or absence of lipid envelope
3
Q

What defines a viral:
family
genera
subtype

A

family: similar structure/genomic/replication properties; “-viridae’ ex. herpesviridae
genera: families breakdown into genera; “-virus” ex. HSV, CMV, Vericella Zoster virus

Subtypes: based on nucleotide sequence and anitgenic reactivities ex. HSV type 1, HSV type 2 etc.

4
Q

What are the common clinically encountered DNA viruses?

A
  • Hep B
  • HPV
  • Parvovirus B19
  • Adenovirus
  • Herpesviridae
  • Polyomaviruses
5
Q

What are the common clinically encountered RNA viruses?

A
  • Influenza
  • RSV
  • Parainfluenza
  • Hepatitis A,C,D,E
  • Enteroviruses
  • Encephalitis viruses
  • Measles, mumps, rubella
  • Norwalk, Rotavirus

*most others

6
Q

What are the 7 steps of viral replication?

A
  1. adsorption
  2. entry
  3. uncoating
  4. transcription
  5. synthesis of virus components
  6. assembly
  7. release
7
Q

What virus is an exception in that it synthesizes its parts (nucleic acid + structural proteins) in the host cells cytoplasm instead of the nucleus?

A

Poxvirus

8
Q

What are 4 possible outcomes of virus-host cell interaction?

A
  1. cell death (lytic)- due to cytophathic effect of virus
  2. cell transformation - cell converted to malignant/cancerous cell
  3. latent infection (occult)–persistent infection in quiescent state …can reactivate anytime to produce disease; continuous or intermittent shedding.
  4. cell fusion to form multinucleated cells
9
Q

What are the 3 types of persistent viral infection?

A
  1. chronic carrier- ex. Hep B, C and congenital Rubella, CMV—chronic illness characterized by continuous shedding for long periods
  2. Latent infection- ex. herpesviridae—symptomatic or asymptomatic shedding
  3. Slow virus infections- due to prolonged incubation period (measles, SSPE)
10
Q

Which viruses take the following amount of time for incubation:

hours to 1-2 days

1-3 weeks

weeks-months

months-years

A

hours to 1-2 d: respiratory viruses, GI viruses

1-3 wks: M/M/R, VZV, HSV, Chlamydia, Enteroviruses, Polio, WNV

weeks-months: Hepatitis viruses, HIV, EBV, Rabies

Months-yrs: Prions

11
Q

What 3 Igs are involved in viral infections?

A

IgM- earliest Ab produced, pentamer, formed 1 wk post infx, persists 4-6 wkes pi

IgG- months-yrs, immunity to re-infx bc of this

IgA- dimer, found in secretions, key for immunity post enteric infx, not measured for diagnosis usually

12
Q

How do the following act in fighting viral infx?

Th
Ts
Tc
Td
NK
IL-1, IL-2
A

Th- T helper cells–> stimulate CTL and activate B cells

Ts- T suppressor cells–> control and regulate the CTL by suppressing Th cells

Tc- cytotoxic T cells–> main effector cells that kill virus-infected cells

Td- delayed hypersensitivity T cells–> release macrophage activation factor

NK-direct killing of virus-infected cells

IL-1,IL-2: modulate immune response

13
Q

What are the 3 mainstays of diagnostic virology?

A
  1. virus isolation (culture)
  2. direct detection
  3. serology (Ab/Ag)
14
Q

What is the diagnosis of acute (recent) infx based on wrt serology?

A

i) detection of IgM
ii) four-fold rise in Ab titre
iii) seroconversion
iv) very high single Ab titre (unreliable)