Polio vaccine question

[LuckiestOne]

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Which of the following features of the inactivated poliovirus vaccine best explains why it prevents paralytic polio but does not prevent replication of the virulent poliovirus in the enteric tract?

a) It does not elicit cell-mediated immunity to viral capsid proteins

b) It does not elicit neutralizing antibody to virulent poliovirus

c) It elicits IgG but not secretory IgA

d) It only protects against one serotype of virulent poliovirus

This is an NBME question and I don't know what the true answer is but the general consensus is that C is correct.

But why is it? Why is it that only IgG is produced but not IgA? Wouldn't APC activate Th2 cell -> activate all types of immunoglobulin?

If you could clarify the mechanism in how these immunoglobulins come about, I'd appreciate it!

 

[Myxedema]

IgA is generated as a result of mucosal immune response and acts as an important host defense factor against mucosal agents. Since inactivated form of polio is given IM, it leads to IgG, not IgA, production.

 

[Belleza156]

Live polio vaccine is taken orally, so you would get secretory IgA in the enteric tract, preventing viral replication. They are just testing that you know the difference between live and inactivated (Salk and Sabin) polio vaccine.

 

[LuckiestOne]

Thanks for your responses. So how exactly are each of the Igs created? M and D are simply created from peripheral B cell phagocytosis, right?

I thought that IgG requires IL-4 trigger and IgA requires IL-5 trigger... So an intramuscular injection would not cause IL-5 release? I don't understand why not, as Th2 cells will be activated...

So do we ONLY have IgA against the things that have come in contact with our mucosa?

I would appreciate it if you could tell us the mech behind each Ig's production.. Thank you for your help!

 

[Phloston]

LuckiestOne, be sure you specifically write in the titles of your threads: "NBME question." There are probably quite a few of us who want to look at / answer your posts, but who also don't want the NBME questions spoiled.

 

[Morsetlis]

Live polio vaccine is taken orally, so you would get secretory IgA in the enteric tract, preventing viral replication. They are just testing that you know the difference between live and inactivated (Salk and Sabin) polio vaccine.

It bugs me a bit that you say "live and inactivated" then put Salk and Sabin, wherein Salk's is actually the inactivated and Sabin's is the live.

😛