Virology Lecture 1

Front 1

what do viruses have?

Back 1

nucleic acid genome, protective coat, and the means to enter, replicate, and exit a host to spread to new hosts

Front 2

what do viruses NOT have?

Back 2

functional ribosomes, mitochondria, or the means to generate metabolic building blocks

Front 3

what type of parasites are viruses?

Back 3

obligatory intracellular parasites (essentially a bag of genes)

Front 4

how do viruses make progeny virus?

Back 4

replicate in cells by synthesizing viral components (nucleic acid and protein) and assembling them.

Front 5

how many progeny do viruses make in a single cell?

Back 5

thousands of progeny

Front 6

what is the viral genome composed of?

Back 6

DNA OR RNA (never both)

Front 7

what do all viruses encode?

Back 7

protein components of their protective coats

Front 8

what else might viruses encode?

Back 8

polymerase to aid in replication of the nucleic acid, additional enzymes (proteases, nucleotide-modifying enzymes), proteins which affect host cell functions (shut off host cell macromolecular synthesis, inhibit induction of interferon, etc)

Front 9

why are infectious pathogens?

Back 9

those produced in one cell can spread to other cells and infection alters fundamental cell processes

Front 10

what do we know about when viruses originated?

Back 10

after cells since they are dependent on cells

Front 11

where did viruses come from?

Back 11

either progressive degeneration of parasitic microorganisms or evolved from components of host cell

Front 12

what class of hosts do viruses infect?

Back 12

animals, plants, bacteria

Front 13

what is the purpose of experimental viral infection of cells/hosts?

Back 13

to amplify virus sample for study, to monitor effects of virus infection,

Front 14

how do we propagate/amplify viruses for study in cells or hosts?

Back 14

start with healthy cells or hosts, infect with virus from impure sample (tracheal wash, feces) or semi-purified or purified virus, allow time for virus replication, then harvest the amplified virus for further study

Front 15

what hosts are available for propagation/amplification for study?

Back 15

laboratory animals, embryonated eggs, organ cultures, cell cultures

Front 16

what are the advantages of using laboratory animals for propagation/amplification?

Back 16

no selection for adaptive mutation in virus and small animals are relatively inexpensive

Front 17

what are the disadvantages of using laboratory animals for propagation/amplification?

Back 17

the affect on the animal and expense of large animals

Front 18

what are the advantages of using embryonated eggs for propagation/amplification?

Back 18

fertile eggs easy to manipulate & respiratory viruses grow well

Front 19

what are the disadvantages of using embryonated eggs for propagation/amplification?

Back 19

most enteric viruses don't grow in eggs

Front 20

what are the advantages of using organ culture for propagation/amplification?

Back 20

grow some viruses that don't grow well in standard cell cultures

Front 21

what are the disadvantages of using organ culture for propagation/amplification?

Back 21

difficult to maintain

Front 22

what are the advantages of using cell culture for propagation/amplification?

Back 22

very easy to amplify virus

Front 23

what are the disadvantages of using cell culture for propagation/amplification?

Back 23

many viruses don't grow well in cultured cells & selects adaptive mutations in virus, often attenuating

Front 24

what is an organ culture?

Back 24

explant organ portion, provide appropriate environment

Front 25

what is a cell culture?

Back 25

isolate tissue, mince & digest with protease to single cells, maintain in appropriate environment as suspension culture or adherent culture depending on cell type

Front 26

what are the classes of cell culture?

Back 26

primary cell cultures, cell strains, cell lines

Front 27

what are primary cell cultures?

Back 27

freshly prepared cells from animal tissue

Front 28

what are cell strains?

Back 28

primary cell cultures 'passaged' successively

Front 29

what are cell lines?

Back 29

immortal cultures derived from cell strain after crisis (immortal but contact inhibited and often aneuploid) or derived from tumors (altered growth regulation in vivo maintained in vitro

Front 30

how do we study cells/hosts as victims or indicators of virus infection?

Back 30

infect cells/hosts, monitor health as indicator of virus infection, cell health (cytopathic effect) and animal health (effects are virus and host specific)

Front 31

what are the advantages of using laboratory animals as victims?

Back 31

true viral pathogenesis

Front 32

what are the disadvantages of using laboratory animals as victims?

Back 32

consequences for animal and costs

Front 33

what are the advantages of using embryonated eggs as victims?

Back 33

respiratory viruses grow well, easy to manipulate, can be sensitive indicators for certain viruses

Front 34

what are the disadvantages of using laboratory animals as victims?

Back 34

enteric virsuses don't grow well

Front 35

what are the advantages of using organ cultures as victims?

Back 35

grow viruses that won't grow in other cultures

Front 36

what are the disadvantages of using organ cultures as victims?

Back 36

inconvenient to use as indicator

Front 37

what are the advantages of using cell cultures as victims?

Back 37

if virus can replicate, it is a sensitive indicator but no host immune response to limit infection other than cell's own antiviral response

Front 38

what are the disadvantages of using cell cultures as victims?

Back 38

many viral isolates don't replicate in cultured cells

Front 39

what are the possible outcomes from viral infection?

Back 39

lytic infection, persistent infection, transforming infection

Front 40

what happens in lytic infection?

Back 40

cells die

Front 41

what is the sequence of events in lytic infection?

Back 41

virus causes cytopathic effect (CPE) then cell death

Front 42

what does CPE stand for?

Back 42

cytopathic effect

Front 43

how is CPE type determined?

Back 43

its specific to virus and cell type

Front 44

what are signs of early CPE?

Back 44

inclusion bodies (viral factories) and multinucleate syncytia

Front 45

what are inclusion bodies?

Back 45

viral factories

Front 46

what are multinucleate syncytia?

Back 46

fused cells with multiple nuclei

Front 47

what are signs of later CPE?

Back 47

adherent cells round up & lose adherence and dead cells no longer exclue vital dyes

Front 48

what are the mechanisms of cell death?

Back 48

necrosis & apoptosis

Front 49

what is necrosis?

Back 49

inhibition of macromolecular synthesis

Front 50

what is apoptosis?

Back 50

activation of specific death pathway

Front 51

how is mechanism of cell death determined?

Back 51

by virus type, cell type, and environment of interaction