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It is said that

  1. "When a virus or a pathogen enters the body, the immune-response produces Y-shaped proteins called antibodies to bind to the pathogen or virus".
  2. "Also it is possible to extract antibodies from the blood."
  3. Since antibodies are proteins, is it possible to sequence their structure ?
  4. If the answer to point-3 is Yes, then can't coronavirus antibodies be sequenced, more antibodies be produced from this sequence on a large scale, and then these are administered to the infected people ?

I would like to know any challenges to the above mechanism like "difficulty in figuring out the correct antibody or so" ? Thanks!

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    $\begingroup$ Looks like you have re-invented monoclonal antibodies. en.wikipedia.org/wiki/Monoclonal_antibody $\endgroup$ Nov 23 '20 at 20:53
  • $\begingroup$ @PolypipeWrangler Yeah, in a way. But this is not done via sequencing of the protein but isolating and identifying the right plasma cell. $\endgroup$
    – Chris
    Nov 24 '20 at 6:31
  • $\begingroup$ Thank you all for the information! $\endgroup$ Nov 24 '20 at 10:34
  • $\begingroup$ @Chris does this mean that the above mechanism has not been "exactly" applied till date ? I am asking this since you said "not done via sequencing of the protein but isolating and identifying the right plasma cell". $\endgroup$ Nov 24 '20 at 10:39
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    $\begingroup$ @harrypotter having the protein sequence doesn't help you making the functional protein. Having the relevant plasma cell does. $\endgroup$
    – Chris
    Nov 24 '20 at 10:42
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Giving a simple answer is difficult as the field of humoral immunology is quite extensive. Here is an abbreviated overview.

Our body produces myriads of different antibodies during an immune response, not just one. It is impractical to isolate and sequence one antibody protein as their sequence differs in very subtle ways. N-terminal sequencing like Edman degradation is not practical as it covers only a few dozen residues at most. Perhaps proteolytic digest of an antibody and peptide sequencing is possible, but again this requires a large amount of a pure antibody. Protein sequencing is not practical.
Instead, people sequence the DNA corresponding to a given antibody instead of sequencing the antibody protein itself. As a given B cell expresses one antibody in large amounts, Milstein and Kohler (Nobel laureates) devised a technique to fuse B cells with tumor cells, creating hybridomas. Each hybridoma thus produces a single antibody. Such hybridomas may be cultured – monocultured in fact - in the lab to large amounts, leading to the production of a uniform, single antibody, termed monoclonal antibody. The corresponding DNA sequence of such monoclonal antibody may be readily sequenced.
I would think it feasible to create a library of individual hybridoma monocultures using a patient’s B cells, and then select the hybridoma producing the best monoclonal antibody from the library, and sequence that DNA. Epitope binning [https://en.wikipedia.org/wiki/Epitope_binning] is one example of a technique to identify the best antibody. The successful hybridoma may then be culture to large scale to produce lots of that exact antibody.
Administering such purified antibodies to a patient is not straightforward as this foreign protein will be itself recognized by the patient's immune system and cleared. There are techniques to reduce the immunogenicity of a given antibody, but that will be a lengthy discussion in itself.

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  • $\begingroup$ Welcome to Biology.SE! This looks like it may be a good answer, but answers are much more likely to receive a favorable response if you include supporting references (primary literature is best, but for this textbooks may be acceptable). Without that support, your answer is indistinguishable from opinion. This is a good example of how to format references. ——— You may also want to take the tour and then consult the help center pages for additional advice on How to Answer effectively on this site. Thank you! 😊 $\endgroup$
    – tyersome
    Dec 24 '20 at 19:52
  • $\begingroup$ Thanks for the answer. It was useful! $\endgroup$ Jan 4 at 10:13
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  1. It is possible to sequence these antibodies.
  2. It is likely that these antibodies are already produced, but injecting antibodies into people does not build immunity. At best, it can temporarily mitigate the spread of the virus. It does not build immunity because it would not teach your body to make its own antibodies, which is the purpose of a vaccine.
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  • $\begingroup$ Thanks @JMorrissette, if I give sequenced antibodies over a period of time, is it possible that these antibodies bind to all the existing virus proteins. Partly we will have destroyed cells but partly the uninfected cells can be saved. Isn't it true ? $\endgroup$ Nov 24 '20 at 10:37

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