lecture set 4 banfield

Question 1

what animal is one of the only animals to not have disease related with the herpes virus?

Answer 1

sheep

Question 2

true or false, the natural host reservoir of a virus is often not harmful, but if the virus jumps to a different species it is.

Answer 2

true, e.g. a zebra herpes virus killed a polar bear at a zoo

Question 3

explain the shared properties of ALL herpes viruses.

Answer 3

• spherical, enveloped virions
• icosahedral capsid with 162 capsomeres
• lipid envelope with many glycoproteins (10 - 12)
• linear dsDNA
• 70-200 genes

Question 4

explain the alpha proteins of the herpes virus

Answer 4

herpes virus has a sequential transcription. alpha protein genes are turned on first which help the virus evade the host immune response and regulate the viruses further gene expression

Question 5

what class of proteins are the alpha proteins?

Answer 5

they are called the kinetic class (transcribed quickly)

Question 6

explain beta proteins in herpes transcription

Answer 6

proteins for nucleotide metabolism and genome replication

Question 7

explain gamma proteins of herpes virus transcription

Answer 7

gamma proteins are structural proteins required after genome replication

Question 8

t or f, herpes viruses establish latency where few of their genes are expressed. they can be reactivated to become infectious.

Answer 8

true,

Question 9

explain the transmission of herpes viruses

Answer 9

herpes particles are very fragile outside of cells and therefore require close transmission. Typically by skin to skin contact. in crowded areas such as where livestock live, sneezing and droplet spread can transmit it too.

Question 10

explain alpha herpesviruses

Answer 10

• they replicate quickly, within 12 hours
• they infect the skin then go up axons and establish latency in neurons.
• they lyse the cells they infect
• some have a broad range of hosts

Question 11

what 2 viruses are prototype alpha herpes viruses?

Answer 11

herpes simplex virus 1 and VZV

Question 12

what is the leading cause of blindness?

Answer 12

HSV1 reactivation in the eye

Question 13

explain beta herpesviruses

Answer 13

• they grow very slowly (80-20 hours)
• they become latent in lymphocytes and monocytes
• they take several days to lyse the cells they infect
• they have a restricted host range

Question 14

t or f, HCMV and VZV are both common beta herpesviruses

Answer 14

false,
HCMV = Beta
VZV = alpha

Question 15

explain gamma herpes viruses

Answer 15

• restricted host range
• infect (and can transform) B lymphocytes
• only herpes virus that can cause cancer

Question 16

there are 8 human herpes virus where humans are the natural host. there is an additional pseudo one. what is this 9th one?

Answer 16

monkey B virus

Question 17

t or f, Monkey B virus is very pathogenic to humans

Answer 17

true, it infects pseudo bi-polar neurons allowing it to go the brain

Question 18

what are tegument proteins

Answer 18

they are proteins that are beteen the viral envelope and the nucleocapsid which act as a middle layer. They are often involved in evasion of the host immune response

Question 19

explain how HSV attaches and enters to host cells

Answer 19

• glycoprotein D is important in binding the cell receptors
• then 4 glycoproteins form a complex which leads to fusion with the cell membrane
• hsv capsid and tegument proteins are released into the cell (tegument set up internal environment of cell)
• hsv capsid binds a microtubule for transport

Question 20

explain how the HSV gets its genome into the nucleus

Answer 20

• after binding the microtubule, motor proteins take it to the nucleus where it docs to a nuclear pore
• since the DNA is packaged at a very high pressure, upon this binding the capsid opens and injects the DNA.
• the linear dsDNA becomes circular once in the nucleus.

Question 21

what is VP16?

Answer 21

a very potent and well known transcription factor which is in the herpes tegument. it enters the nucleus and acts on the circular DNA when it enters.

Question 22

explain DNA replication and gene expression in the HSV.

Answer 22

VP16 acts on the DNA to create transcripts for alpha proteins. the translated alpha proteins will aid in immune evasion and they will be transcription factors for beta genes to turn on. the translated beta proteins are responsible for DNA replication which now begins. The circular DNA gets converted into whats called concatameric DNA which is transcribed to make gamma proteins for capsid synthesis

Question 23

where does the HSV replicated DNA get packed into the nucleus? how does this occur?

Answer 23

• occurs in the nucleus

- it gets fed through the UL6 portal

Question 24

what is concatemeric DNA molecules?

Answer 24

this the REPLICATED DNA that transcribes for gamma proteins and gets packaged into the capsid

Question 25

what are the three components of the HSV capsid

Answer 25

hexamers pentamers triplexes

Question 26

Explain HSV egress.

Answer 26

once the Concatemeric DNA has been fed into the capsid egress occurs. - the capsid interacts with two proteins which form an "egress complex" this leaves into the perinuclear space in an endosome. - Endosome fuses with the nuclear membrane and capsid + proteins enter the cytoplasm - Capsid goes to the golgi where TGN proteins interact with capsid glycoproteins to coordinate the budding rxn. - now infectious, the HSV leaves the golgi forming an outer endosome - this fuses with the PM to expel the enveloped HSV

Question 27

t or f, all HSV capsids are egressed to become infectious by envelope acquirement

Answer 27

false, there is the two proteins binding the HSV capsid upon initial export have a "quality control" mechanism that will not allow non-functional (No DNA) capsids to pass

Question 28

explain the characteristics of poxviruses.

Answer 28

- large viruses - DNA genome - has envelope with many glycoproteins - replicate in the cytoplasm! - some are restricted to one host, others have multiple hosts

Question 29

what is a zoonotic virus?

Answer 29

a virus that can jump hosts, often animal to human

Question 30

t or f, disease is never seen in zoonotic hosts

Answer 30

false, disease is not normally seen in natural hosts but often seen in zoonotic hosts

Question 31

explain | monkeypox

Answer 31

monkey pox is poxvirus that becomes fatal for humans. Once infected, monkey pox can be spread further by human - human transmission. small pox vaccine provides some immunity to it.

Question 32

what is a dead end host?

Answer 32

once in the host the virus can no longer be transmitted. This is not the case for monkey pox

Question 33

why do poxviruses have many enzymes within their core?

Answer 33

since they replicate in the cytoplasm they need defensive enzymes! additionally it cannot use the cells transcription machinery and needs to bring its own.

Question 34

t or f, pox virus gene expression is sequential

Answer 34

true, similar to herpes virus

Question 35

t or f, the initial proteins made by pox virus can be immunosupressents that may have a medial application

Answer 35

true

Question 36

explain pox virus DNA replication | 8

Answer 36

1. dsDNA is linear and ends are closed 2. so nuclease nicks one end exposing it. 3. the ends are IR's therefore they fold over and hybridize each other 4. the 3' end is now folded over and looks ds which acts as a primer for synthesis. 5. DNA synthesis occurs at both ends of the linear genome making two genomes joined end to end 6. the process begins again to form a concatemer 7. this is cleaved into individual genomes 8. the ends are sealed off.