After reading an article, I saw expressions like "cross-immunoreactivity among epitopes", "cross-immunoreactivity among variants of virus", "immunological reactions among pairs of peptides" and so on.

I wish to verify my following understandings:

An epitope is also called antigenic determinant, and it is part of the antigen that is recognized by the antibody. An epitope, then, is a part of a virus variant. Peptides are short chains of amino acids. Thus, we can talk about the immunological reactions among peptide-pairs, because the virus variant itself is a protein, which is composed of peptides? Did I understand it correctly?

Moreover, I saw a sentence like "this antibody is against a few variants while reacting with all tested peptides", so I guess reacting here includes against? Reacting may include other situations, right?

  • $\begingroup$ I slightly modified your wording. Feel free to roll back. $\endgroup$ – AliceD May 21 '15 at 2:50

Everything you state is correct, except that I disagree with your statement that a "[...] virus variant itself is a protein, which is composed of peptides.

A virus is typically composed of a protein capsule with genetic material on the inside. So technically, a virus is not a protein, but its outer shell is composed of proteins. Further, a protein does not necessarily have to be composed of (multiple) peptides - it can be a single amino acid chain.

  • 1
    $\begingroup$ IIRC proteins are made of at least one, but possibly more than one peptide (eg hemoglobin) $\endgroup$ – March Ho May 21 '15 at 5:30

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