Flashcards in Introduction to Virology Deck (14):
What are the 3 types of capsid symmetry exhibited by viruses?
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)
What 4 factors is virus classification based on?
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
What defines a viral:
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.
What are the common clinically encountered DNA viruses?
What are the common clinically encountered RNA viruses?
-Measles, mumps, rubella
What are the 7 steps of viral replication?
5. synthesis of virus components
What virus is an exception in that it synthesizes its parts (nucleic acid + structural proteins) in the host cells cytoplasm instead of the nucleus?
What are 4 possible outcomes of virus-host cell interaction?
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
What are the 3 types of persistent viral infection?
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)
Which viruses take the following amount of time for incubation:
hours to 1-2 days
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
What 3 Igs are involved in viral infections?
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
How do the following act in fighting viral infx?
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
What are the 3 mainstays of diagnostic virology?
1. virus isolation (culture)
2. direct detection
3. serology (Ab/Ag)