METHODS OF DETECTING ANTIBODIES TO SARS-COV-2
The present disclosure provides solution based assays for detecting antibodies induced by SARS-CoV-2 (anti-SARS-CoV-2) in a biological sample.
1 . A solution phase bridging assay for detecting antibodies induced by SARS-CoV-2 (anti-SARS-CoV-2) in a biological sample from a subject, the assay comprising:
contacting the sample with a first labeled protein with a donor fluorophore;
contacting the sample with a second labeled protein with an acceptor fluorophore, wherein the first and second proteins are both spike proteins (S-protein), the first and second proteins are both nucleocapsid proteins (N-proteins), or in an alternative embodiment, two S-proteins and two N-proteins;
incubating the sample for a time sufficient to generate a ternary complex of the first labeled protein with a donor fluorophore, the second labeled protein labeled with an acceptor fluorophore and the anti-SARS-CoV-2, or in the alternative embodiment, incubating the sample for a time sufficient to generate two ternary complexes, wherein (i) the first ternary complex is a S-protein labeled with a donor fluorophore, a S-protein labeled with an acceptor fluorophore and the anti-SARS-CoV-2, the (ii) second ternary complex is a N-protein labeled with a donor fluorophore, a N-protein labeled with an acceptor fluorophore, which acceptor fluorophore is optionally different than the S acceptor fluorophore and the anti-SARS-CoV-2; and
exciting the sample having the ternary complex(es) using a light source to detect a fluorescence emission signal associated with fluorescence resonance energy transfer (FRET) when the donor fluorophore is excited.
2 . The method according to claim 1 , wherein the antibodies are members selected from the group consisting of IgA antibodies, IgM antibodies, IgG antibodies or a combination thereof.
3 . The method according to claim 1 , wherein the S-protein is a member selected from the group consisting of a mammalian cell expressed recombinant spike protein of SARS-CoV-2, a fragment thereof or a synthetic S-peptide.
4 . The method according to claim 1 , wherein the N-protein is a member selected from the group consisting of mammalian cell expressed recombinant nucleocapsid protein of SARS-CoV-2, a fragment thereof or a synthetic N-peptide.
5 . The method according to claim 1 , wherein the FRET emission signals are time resolved FRET emission signals.
6 . The method according to claim 1 , wherein the sample is a biological sample.
7 . The method according to claim 6 , wherein the biological sample is selected from the group consisting of whole blood, urine, a fecal specimen, plasma, serum, saliva or an oral fluid.
8 . The method according to claim 7 , wherein the biological sample is serum.
9 . The method according to claim 1 , wherein in the alternative embodiment, two S-proteins and two N-proteins are used to generate two ternary complexes, wherein (i) the first ternary complex is a S-protein labeled with a donor fluorophore, a S-protein labeled with an acceptor fluorophore and the anti-SARS-CoV-2, the (ii) second ternary complex is a N-protein labeled with a donor fluorophore, a N-protein labeled with a different acceptor fluorophore and the anti-SARS-CoV-2, to obtain total antibody.
10 . The method according to claim 1 , wherein the donor fluorophore is a cryptate.
11 . The method according to claim 1 , wherein the cryptate is a terbium cryptate.
12 . The method according to claim 1 , wherein the acceptor fluorophore or the different acceptor fluorophore is independently selected from the group consisting of fluorescein-like (green zone) dyes, Cy5, DY-647, phycoerythrin, allophycocyanin (APC), Alexa Fluor 488, Alexa Fluor 546, and Alexa Fluor 647.
13 . The method according to claim 1 , wherein the light source provides an excitation wavelength between about 300 nm to about 400 nm.
14 . The method according to claim 1 , wherein the fluorescence emission signals emit emission wavelengths that are between about 450 nm to 700 nm.
15 . The method according to claim 1 , wherein an emission signal associated with a test sample with a value equal to or greater than a cut-off value is considered to be positive.
16 . The method according to claim 1 , wherein an emission signal associated with a test sample with a value less than a cut-off value is considered to be negative.
17 . A competitive assay method for detecting antibodies induced by SARS-CoV-2 (anti-SARS-CoV-2) in a biological sample from a subject, the assay comprising:
contacting the sample with a complex comprising an anti-SARS-CoV-2 antibody labeled with a first fluorophore and an isolated labeled protein(s) with a second fluorophore, wherein the isolated labeled protein is a spike protein (S-protein) specific to the anti-SARS-CoV-2 antibody or a nucleocapsid proteins (N-protein) specific to the anti-SARS-CoV-2 antibody, wherein the complex emits a fluorescence emission signal associated with fluorescence resonance energy transfer (FRET) when the first fluorophore is excited using a light source;
incubating the biological sample with the complex for a time sufficient for the anti-SARS-CoV-2 in the sample to compete for binding with the anti-SARS-CoV-2 antibody labeled with the first fluorophore; and
exciting the sample using a light source to detect the fluorescence emission signal associated with FRET, wherein an absence of the fluorescence emission signal or a decrease in the fluorescence emission signal relative to the fluorescence emission signal initially emitted by the complex indicates the presence or amount of antibodies induced by SARS-CoV-2 (anti-SARS-CoV-2) in the sample.
18 . The method according to claim 17 , wherein the first fluorophore is a donor fluorophore.
19 . The method according to claim 17 , wherein the second fluorophore is an acceptor fluorophore.
20 . The method according to claim 17 , wherein the antibodies are members selected from the group consisting of IgA antibodies, IgM antibodies, IgG antibodies or a combination thereof.