I wrote down this manual for anyone to follow - https://drive.google.com/file/d/1qtfyE42ECZAqSFpqGR9JawX3YoVAvVSg/view?usp=sharing
As it is a modified protocol I'm not sure It will work (especially when we do not have any positive and negative baseline).
Antigen (peptide) binding to the plates:
Addition of the primary antibodies (from nasal swabs):
Addition of secondary antibodies conjugated with HRP:
I guess anything with a signal stronger then control can be considered positive signal. Usually for my experiments I'm using the cutoff of "three times value of the blank or more (after subtraction of the proper negative control)". If you do not have negative control you can only use blank as a point of reference.
I think that you can perform ELISA using unpurified nasal wash or diluted mucus. I often perform ELISA using sera/full blood or unpurified cell lysates. I would do a nasal or throat swab and put it in phosphate buffer (or PBS). You can further dilute samples if the viscosity is too high. ELISA is very sensitive and my guess is, you should be able to see positive signal without plate reader. It very much depends on both antigen used in ELISA and antibody concentration. For peptides such as yours (without tags) I use concentration of about 10-20 ug/mL, sera diluted 1:1000-1:10000 and higher and still get good, clear signal. Of course you don't want to dilute your nasal samples so much, but undiluted, 1:5 or 1:20 could give nice reading, hopefully without any background. EDIT: I know it may sound complicated, but I just wanted you to know that checking immune response against antigen used (in this case peptides) is a possibility.
This may be true, I'm talking about ELISA test. In theory you only need high binding plates, secondary antibodies and some kind of detection (TMB + H2SO4 give colorimetric effect and you can try and skip plate reader). I understand that it can be quite complicated to perform, but I am wondering how you plan to chceck the immune response against Orf1 and Orf 8. You could check blood against Spike and nucleocapside (you need to check if antigen test is using full length Spike and Nuc), but due to the use of peptides, lenghth of the peptides and expected low IgG titer, detection (as you said) can get tricky. But congrats anyway.
It's quite interesting what you are doing. Have you thought about testing immune response yourself using peptides from the vaccine? Of course you can only run humoral responses, but it would give you far more accurate results then any commercially available test. You could bind peptides to the high-binding plates, use your mucosa samples and detect with universal anti-human IgM+IgG+IgG antibodies conjugated with HRP.