dannieal
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I'm currently studying for my final year exams, but is experiencing a mental block. Could someone please be kind enough to help me answer some immuno questions?

How are polio-derived peptides generated and presented to T cells?
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macpatgh-Sheldon
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Hello Mr Daniel OR Miss Daniella (your username is like most trainers = unisex !)

This topic is very specialized so I can provide only info that is either common knowledge (e.g. about the Salk [inactivated virion] and Sabin [live attenuated virion] vaccines; or the pathogenesis of polio) OR that I have construed from facts I have located.
It also depends on what degree you are doing as to what might be the most relevant info, so please forgive me for any irrelevant stuff.

Poliomyelitis is caused by an unenveloped RNA virus (a retrovirus = one that uses reverse transcriptase to make DNA from RNA [retro = behind or backwards as in retrosternal pain of myocardial infarction = behind the sternum]) with an icosahedral structure. It is a picornavirus (pico = v small then "RNA" [picornavirus = v small RNA virus about 25 nm in diameter]) of the genus enteroviridae [entero = e.g. intestine]. It synthesizes the [viral protein] VP1-4 proteins (see pic I shall upload after). VP1 to VP3 are surface proteins (VP4 is internalized) These proteins have a very high degree of antigenic variability, so that there is difficulty in producing specific antibody [similar to the need for new flu vaccine every year]; however, since the above vaccines have been available for decades, we know that the antibody response (mediated by B cells) plays a major part in our defence against polio.

From the immunology viewpoint, the polio virus, which gains entry into the GI tract via food intake, then resides in the gut lymphoid tissue (e.g. Peyer's patches in the intestine) then causes a viraemia (= spreads via the blood) to infect the motor neurones in the CNS causing paralysis of the limbs, etc. [can paralyse respiratory muscles causing death), is recognized by specific B cells, which produce specific antibody, which neutralizes the viral particles; because of the long incubation period of this infection [due to the time needed for spread from the gut to the brain], the patient can launch a secondary immune response, which then allows T cells to phagocytose the virion-infected cells by the process of opsonization i.e. antibody making it easier for T cells to engulf them.

The involvement of MHC antigens and of complement (C3 and C4) in this processes is probably also crucial, as is the summoning of macrophages by cytokines.

I could not find info specific to polio on ways in which the virus might block the MHC process, but it might be similar to e.g. the EBV (Ebstein-Barr virus - cause of infectious mononucleosis = glandular fever, and of Burkitt's lymphoma) producing glycine/alanine repeats that inhibit processing of viral proteins; OR the CMV [cytomegalovirus], which produces a protein that interferes with an essential part of the peptide loading complex.

I hope this is detailed enough for you!

Regards,
Sheldon.
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macpatgh-Sheldon
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