banfield lecture 12

Question 1

what kind of virus is Polio virus?

Answer 1

• part of the picornavirus family
• is an enterovirus (infects GI tract)
• as 3 serotypes

Question 2

what is the genome and capsid of poliovirus?

Answer 2

it is a +RNA genome. It has no envelope.

Question 3

t or f, polio has more than one host

Answer 3

false, humans are the only host for polio

Question 4

what is the GALT

Answer 4

gust associated lymphoid tissue

Question 5

explain the dissemination of polio in humans (starting from location of infection to shedding)

Answer 5

1. it enters the mouth in fecal water
2. gets into GALT where it reaches M cells.
3. this transfers the virus into lymphoid cells which then permits the virus into the blood. Note: polio virus in the blood is cell-free (not bound to cells)
4. from the blood polio invades motor neurons of the SC
5. shed when you shit

Question 6

t or f, 90% of ppl with polio have an inapparent infection. 4% have minor illness. 2% meningitis. 0.2% flaccid paralysis

Answer 6

true, only 0.2% of ppl have paralysis from motor function loss

Question 7

how do you measure polio virus in a population?

Answer 7

you have to measure the number of ppl with flaccid paralysis and then work backwards

Question 8

t or f, children are more susceptible to paralytic polio

Answer 8

false, as you get older the odds of developing it increase. Additionally children tend to get paralysis in one leg whereas adults may get it in more places.

Question 9

what neurons are the cause of paralytic polio?

Answer 9

motor neurons of the dorsal horn ganglia in SC.

Question 10

What is inactivated polio vaccine (IPV)?

Answer 10

• this is an injected vaccine that gives you systemic immunity.
• it places IgG into your bllod stream. Upon a polio viremia, IgG will attack immediately.
• IPV will prevent flaccid paralysis

Question 11

What are the cons of IPV?

Answer 11

• it does not provide mucosal immunity
• this means it does not prevent you from getting the virus, it just prevents you from getting disease.
• this is b/c IgG is not in your gut.
• another con is that this is expensive

Question 12

what is one major pro to the IPV?

Answer 12

• it has never been linked to vaccine associated disease.

Question 13

What is the Oral poliovirus vaccine? (OPV)

Answer 13

• ## this is a live attenuated poliovirus that you ingest orally.

Question 14

what are the cons of OPV

Answer 14

• since RNA dependent RNA polymerases do not have proofreading mechanisms , a mutation can sometimes revert the attenuated polio virus back into its wild type form!!
• This is called VAPP–> Vaccine associated paralytic poliomyelitis.

Question 15

what are the pros of OPV?

Answer 15

• inexpensive
• provides systemic AND mucosal immunity
• easy administration

Question 16

t or f, within 35 hours OPV can revert to wild type mixture within a person. Within 2 days its entirely reverted

Answer 16

true, viruses exist as their wild types for a reason. Therefore NS will select for them as much as possible.

Question 17

WHO wants to eradicate polio by widespreading OPV in countries with it. Will this work?

Answer 17

probably not since OPV gives wild type polio evert 250 million doses. (over 2 billion doses needed)

Question 18

t or f, india still has polio

Answer 18

false, its declared polio free

Question 19

what are some problems with WHO’s plans to eradicate polio?

Answer 19

• OPV is a live vaccine which can revert (must use IPV)
• OPV strains can be transmitted
• Hypo/agamma globulinemic people can shed polio without having the disease.
• upon stopping vaccination, infants will be at risk.

Question 20

what is one cause that makes eradicating polio seem impossible?

Answer 20

it can be sequenced and made given the correct. resources