virology basics

Question 1

viruses: obligate

Answer 1

cells that cannot function on own (cannot reproduce unless are in host cell)

Question 2

composition of virus

Answer 2

genetic material enclosed in protein coat (some have envelope as well), DNA OR RNA (not both, single or double stranded), capsid that keeps genetic info safe, have surface glycoprotein that protrude to bind to host cell

Question 3

viral replication steps

Answer 3

• attachment
• entry
• gene expression (mRNA synthesis and protein translation)
• genome replication
• assembly
• egress
• release

Question 4

do viruses use only one receptor on host cell all the time?

Answer 4

no, complex viruses may need to bind to more than 1 (ex: HIV binds first to CD4 on T cells and then to chemokine receptors)

Question 5

viral receptor interacting proteins

Answer 5

• spikes and knobs
• envelope glycoproteins
• receptor binding proteins
• lipid interactions (pore formation, membrane disruption and fusion)

Question 6

cellular receptors

Answer 6

• integral membrane proteins
• cellular surface/plasma proteins
• apical v basolateral location v cell junctions
• endosome
• protein v non protein interacting molecules
• *entry initiated by receptor interactions

Question 7

viral load

Answer 7

how much DNA or RNA of virus in blood (can also seems quantity of receptor on host cell)

Question 8

Where do most viruses replicate?

Answer 8

most in host cell cyto (some in nucleus = influenza and retroviruses, DNA viruses replicate in nucleus except for poxvirus)

Question 9

-/+ single strand RNA

Answer 9

• strand needs to be converted to + strand (needs to go through translation and needs to make more - strand rna…both)

Question 10

+ strand RNA

Answer 10

ready to go and replicate, but during process makes more - strand RNA

Question 11

DNA polymerase

Answer 11

copies viral genome to make more DNA

Question 12

RNA polymerase

Answer 12

assists in transcription (to eventually make protein)

Question 13

assembly of virion

Answer 13

package DNA or RNA and capsized proteins into nucleocapsids (assembly of capsid is coupled to replication of viral genome and this may occur on CM or ER that may become viral envelope, unless doesn’t have envelope)

Question 14

viral pathogenesis

Answer 14

process by which viral infection leads to disease (not all cells infected end up in disease)

Question 15

disease from virus

Answer 15

• virus at target organ
• produces signs and symptoms associated with disease (not all symptomatic though) -> these are a fxn of virus (virulence factors and sites of replication) and the host (genetics, immunocomp)

Question 16

DNA and RNA?

Answer 16

No! Can have both in cell, but only one type is packaged

Question 17

acute infection

Answer 17

• get infection
• have period of virema (symptoms)
• then virus goes away (short lived, finite period of infection then virus is gone)

Question 18

persistant infection, latent

Answer 18

• acute primary infection (can be subclinical)
• viral replication (cleared by IS)
• virus will remain with you, dormant (absence of viral replication)
• followed by reoccurrence (viral rep active)
• PERIODS OF LATENCY

Question 19

persistant infection, slow

Answer 19

• initial primary infection

- persistent low level viral replication (not a true latent phase where have no viral replication), until host dies

Question 20

most common route of viral infection is..?

Answer 20

respiratory tract (have large surface area)

Question 21

fecal oral infection

Answer 21

• infection through gut
• virions must be resistant to extreme conditions
• usually associated with childhood infection (except for noro)
• short incubation periods before disease onset

Question 22

skin infection

Answer 22

-virus enters through breaks in skin, animal bite or injected by anthropod vector

Question 23

cellular changes: cytopathic effect

Answer 23

degenerative changes in cells that are associated with multiplication of certain viruses

• cell transformation -> malignancy (some immortalize cells, make them go on to replicate and cause cancer)
• cell death

Question 24

serology

Answer 24

detects IgG and IgM antibodies

Question 25

culture

Answer 25

detects LIVE virus (replaced by molecular diagnostic techniques), highest specificity

Question 26

DFA (direct fluor antibody)

Answer 26

detects viral protein

Question 27

PCR

Answer 27

detects viral nucleic acid (RNA and DNA), sensitive, specific, fast (cannot detect live virus, so cannot tell if someone has active infection -> can have nuc acid hanging around long after virus dead)
-clinically relevant: if someone is responding well to therapy or not

Question 28

IgM

Answer 28

marker of recent, acute infections (right meow)

Question 29

IgG

Answer 29

more remote infection (remain high forever in host), will be IgG - in first few weeks of disease

Question 30

EIA

Answer 30

enzyme immunoassay: based on flow technology, not sensitive, but fast (used in urgent care settings)

Question 31

histopathology

Answer 31

gold standard for diagnosis of tissue invasive disease (immunostaining for viral protein)

Question 32

if virus in latent state, is antiviral effective?

Answer 32

No! (it will suppress virus for reactivating, does not cure infection)
-when virus latent, DNA polymerase isn’t active (which is what drug works on) so drug won’t do anything

Question 33

antigenic drift

Answer 33

small changes in the genes of influenza viruses that happen continually over time as the virus replicates

Question 34

antigenic shift

Answer 34

abrupt change in the virus