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The Wikipedia article for Viral Proteins contains the following line:

Thus, viruses do not code for many of their own viral proteins, and instead use the host cell's machinery to produce the viral proteins they require for replication

If the host-derived (i.e. not encoded by the virus) viral proteins are made following the hosts DNA, are those proteins still flagged as "viral" by cytotoxic T cells? If so, why don't they attack host cells that have those proteins when uninfected?

My guesses:

  • Those host-derived viral proteins are coded for by the host, but aren't usually produced during normal function
  • The proportion of host-derived viral peptides matters, with a lower proportion indicating normal cell function and a higher proportion indicates infection
  • The viral proteins are a mix of host proteins that, separately, are not recognized as viral, but when put together by virus instruction can form composite proteins whose peptides fragments are viral
  • I'm misunderstanding the quote, and what they meant was "Thus, viruses do not code for self-generation of many of their own viral proteins, and instead code to utilize the host cell's machinery to produce the viral proteins they require for replication"
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  • $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Biology Meta, or in Biology Chat. Comments continuing discussion may be removed. $\endgroup$
    – Bryan Krause
    Aug 25, 2023 at 20:11

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The phrase “viruses do not code for many of their own viral proteins” in this Wikipedia entry is an obvious oxymoron.

I echo what someone else said: “The beauty of Wikipedia is not that it is correct, but that it is correctable”. So I corrected it.

Unless it has been reverted (let battle commence) the first paragraph now reads as follows:

The term viral protein refers to both the products of the genome of a virus and any host proteins incorporated into the viral particle. Viral proteins are grouped according to their functions, and groups of viral proteins include structural proteins, nonstructural proteins, regulatory proteins, and accessory proteins. Viruses are non-living and do not have the means to reproduce on their own, instead depending on their host cell's machinery to do this. Thus, viruses do not code for most of the proteins required for their replication and the translation of their mRNA into viral proteins, but use proteins encoded by the host cell for this purpose.

To expand for this answer:

  • Many viruses rely on either the host-encoded DNA polymerase, RNA polymerase or both for replicating their genome, depending on their size and complexity
  • All viruses depend on the host-encoded machinery of protein synthesis (ribosomes, tRNA, aminoacyl-tRNA synthetases etc.) for the translation of the proteins encoded in their mRNAs (which in some RNA viruses are also their genomes)
  • Some viruses — especially those enclosed by lipid envelopes — may have host-encoded proteins included in their virions, whether by chance or to serve some function.

The immunity ‘problem’

There seems to be no problem to answer regarding the host’s immune response to viral particles, in any case. The immune response recognizes proteins that are ‘foreign’. Virus-encode proteins are foreign. Any host constituents of the virion are not. (This is the essence of the answer from @PrashantBharadwaj.)

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  • $\begingroup$ I lack the permissions to delete the question, I have flagged it for moderator review. Regardless of whether it is deleted, I appreciate your answer and your Wikipedia correction $\endgroup$
    – Gumpf
    Aug 25, 2023 at 18:42
  • $\begingroup$ @Gumpf Since David's answer was useful to you, it probably makes more sense to let both your question and also David's answer stand, in case it's also helpful to someone else in the future. $\endgroup$
    – Bryan Krause
    Aug 25, 2023 at 20:12
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    $\begingroup$ @BryanKrause — Sure. Let it stand. I'll delete the PS. $\endgroup$
    – David
    Aug 26, 2023 at 12:07
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The short answer is that what is attacked is usually what is recognized as foreign (other than exceptions as in autoimmune disorders). As any epitopes that belong to the host are usually protected from attack during immune cell training/selection.

So if viruses use host proteins, there is no reason to attack host proteins because of that.

Immune system only reacts to viral proteins that they have ready access to - such as the outer capsid or coat proteins - and these are not host derived.

I don't have any direct citations, but this article might be insightful - Immune recognition of self and non-self explored in new study, from ScienceDaily

PS : I like the analogies in the comments below the question!

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