Virology Chapter 5

Question 1

What are the 3 types of virus in a vaccine

Answer 1

Attenuated, Inactivated, Subunit

Question 2

What is the difference between an active virus and an attenuated virus? Can an attenuated virus ever cause disease?

Answer 2

an active virus can still infect and replicate, but an attenuated virus can replicate but cannot cause a disease (no infection cycle)

Question 3

Which virus out of the 3 contains intact virus particles

Answer 3

Attenuated and inactivated

Question 4

Which virus out of the 3 contains purified proteins

Answer 4

subunit

Question 5

Which virus out of the 3 can replicate in host

Answer 5

attenuated

Question 6

Which virus out the 3 can induce Ab-mediated immunity

Answer 6

all 3; attenuated, inactivated, subunit

Question 7

Which virus out the 3 induce cell mediated immunity

Answer 7

only attenuated

Question 8

What is cell-mediated immunity

Answer 8

doesn’t rely on antibodies, but rather T cell activation (innate immunity)

Question 9

Explain the characteristics of attenuated virus vaccine

Answer 9

• weakened form of the virus, but it can still replicate
• e.g: OPV
• strong immunity response: activate B cell and T cell
• mimics real infection

Question 10

Explain the characteristics of inactivated virus vaccine

Answer 10

• inactivated = can’t replicate = no infection cycle
• e.g: IPV
• mainly B cell (antibody) (humoral mediated immunity)

Question 11

Why IPV’s have weak T cell activation (no cell-mediated immunity)

Answer 11

because they don’t have virus replication, so the T cell’s can’t recognize and alert the immune system

Question 12

Explain the characteristics of Subunit virus vaccine

Answer 12

• purified parts of the vaccine that has epitopes
• causes a strong antibody response
• not the whole virus

Question 13

what genus is poliovirus from

Answer 13

enterovirus genus

Question 14

why polio can spread through swimming pools?

Answer 14

because the organic matter (dust, sweat, fluids) mask or protect the virus from chlorine in the swimming pool, and poliovirus uses the fecal-oral route

Question 15

what is the term when a virus enters the blood stream

Answer 15

viremia

Question 16

what is poliomyelitis

Answer 16

inflammation of the gray matter of the spinal cord, but most cases infect the throat and gastrointestinal tract

Question 17

why is polio infecting the CNS a “mistake”?

Answer 17

because it doesn’t benefit the virus whatsoever, since infecting motor neurons cannot pass it to other human beings, so the virus just dies

Question 18

what are the three types of poliovirus

Answer 18

abortive polio
non-paralytic polio
paralytic polio

Question 19

explain the characteristics of abortive polio

Answer 19

• subclinical (not detectable, asymptomatic)
• 72 hours
• cold like symptoms = fever, sore throat, headache

Question 20

explain the characteristics of non-paralytic polio (aseptic meningitis)

Answer 20

• clinical (need doctor) = 1-2 weeks
• influenza like symptoms + back pain, muscle stiffness, diarrhea, vomit
• local inflammatory response (innate)
• some infection in meninges

Question 21

explain the characteristics of paralytic polio

Answer 21

• infection of the motor neuron, brain stem, motor cortex
• tingling in the muscles
• muscle cramps, spasms
• muscle pain and weakness on 1 SIDE
• sensitive to touch

Question 22

what is the most severe case of paralytic polio

Answer 22

when the breathing muscles are paralysed so the person cannot breathe = die

Question 23

when a person has paralysis, and they do intense physiotherapy, but then 30-40 years they get Post-polio syndrome, why?

Answer 23

because as you age, you lose surviving motor neurons
AND
surviving motor neurons sprout new dendrites to promote more muscle use, but they can’t handle that stress, so they deteriorate

Question 24

is post-polio syndrome just polio again?

Answer 24

no, polio is an acute infection, the RNA virus cannot stay there for decades

Question 25

what are the symptoms of post-polio syndrome

Answer 25

new muscle weakness that had nerve damage from polio, fatigue, muscle pain because they muscles from polio are usually weaker

Question 26

when you isolate a wild poliovirus, what cell line do you pass it through?

Answer 26

monkey kidney cell line that is continuous

Question 27

to make a virus, why do you have to mutate the isolated virus in the monkey kidney cell line, why can't they be wild?

Answer 27

because only mutants are able to infect and replicate

Question 28

Enteroviruses such as poliovirus, are known for being transmitted via the fecal-oral route and causing disease. What physical traits do these viruses have that allow them to carry this out?

Answer 28

it's a naked virus, so it's resistant to low pH in the gastrointestinal tract, and also resistant to chlorine in swimming pools

Question 29

What are the two types of vaccines are used to induce immunity against poliovirus? What specific forms of immunity do they induce?

Answer 29

OPV = attentuated, so it causes both cell-mediated in the gut (igA) and antibody mediated immune response in the blood (igG) - good for society, can't spread - risk mutation of vaccine and can paralyze IPV = inactive, it causes antibody mediated immune response, good for booster vaccine - protects individual (can't get infected) because injected intramuscular = IgG blood - polio can infect the gut, poop, infect others - expensive

Question 30

From the point-of-view of a physician practicing in Vancouver, what are the important advantages and disadvantages of using each type? What type is typically used to vaccinate children in North America? Would this vaccine be sufficient for a child that travels to areas where poliovirus is still endemic?

Answer 30

IPV advantages – There is no risk of reversion and it promotes a strong, protective immune response, can be used with the immune compromised people or infants that don’t have fully developed immune systems OPV advantages – immunity lasts longer than an IPV Immunity is both systemic and localized antibodies IPV disadvantage – expensive to make, maintain and administer, only produces a systemic response and requires booster shots. OPV disadvantage – potential for a reversion, not be given to the immune compromised people Children in North America get an inactivated form of the vaccine. For children who are traveling in endemic areas, it would be best to get an attenuated virus vaccine so they have a stronger, longer lasting immunity that will protect them better. In addition, once they have cleared the virus from the vaccine, they will make IgA antibodies in their gut secretions. This child could no longer be a carrier of the virus, and cause infections in susceptible people.

Question 31

What is a serotype?

Answer 31

distinct variations within a subspecies of a virus that will cause the production of a distinct population of antibodies

Question 32

what do these antibodies to?

Answer 32

they bind to serotypes (that are used as antigens) and induce an immune response

Question 33

what is the difference between an antigen and a serotype?

Answer 33

Antigens are molecules that can cause an immune response when they enter the human body. Serotypes are groups of a microorganism that all have the same antigens composition on their surface.

Question 34

what are the 3 surface proteins of poliovirus

Answer 34

VP1, VP2, VP3