Multiplex quantitative nucleic acid amplification and melting assay
The invention is a single-tube multiplex assay, capable of simultaneously amplifying, detecting and quantifying multiple nucleic acid targets, using multiple hybridization probes, labeled with the same fluorescent reporter label, but each having a distinct melting temperature. The assay can be further multiplexed with the use of multiple sets of hybridization probes, each set labeled with a separate fluorescent reporter label.
1. A method for amplification, detection and quantification of one or more target nucleic acids in a single sample container comprising the steps of:
(a) contacting a sample, suspected of containing one or more target nucleic acids, with at least one set of oligonucleotides, each oligonucleotide within the set labeled with the same one or more reporter moieties, wherein each said labeled oligonucleotide
i. is sufficiently complementary to at least a subsequence of at least one target nucleic acid;
ii. is capable of binding to the corresponding target nucleic acid with a melting temperature distinct from the melting temperatures of the other labeled oligonucleotides within the same set;
(b) amplifying the target nucleic acids in the sample in an amplification reaction that includes a temperature change interval, wherein said labeled oligonucleotides bound to corresponding target nucleic acids dissociate from the corresponding target nucleic acids;
(c) detecting light emission from said reporter moieties over at least a portion of said temperature change interval; and
(d) plotting the first derivative of said light emission detected in step (c) over at least said portion of the temperature change interval;
(e) determining the maximum value of said derivative plotted in step (d);
(f) repeating steps (b) through (e) multiple times; and
(g) plotting the maximum values of said derivative determined in step (e) against the number or repetitions of steps (b) through (e), and determining the number of repetitions at which a predetermined threshold value of the value determined in step (e) is reached, thus quantifying the relative amount of said target nucleic acid.
2. The method of claim 1 , wherein a control nucleic acid of known concentration is subjected to the steps (a)-(f) simultaneously with said target nucleic acids and the value determined in step (f) for each target nucleic acid is compared to the value determined in step (f) for the control nucleic acid, thereby determining the absolute amount of each said target nucleic acid.
3. The method of claim 1 , wherein each said oligonucleotide in step (a) is labeled with a single reporter moiety.
4. The method of claim 3 , wherein said reporter moiety is fluorescent.
5. The method of claim 1 , wherein each said oligonucleotide in step (a) is labeled with a reporter moiety and a quencher moiety.
6. The method of claim 5 , wherein said reporter moiety and said quencher moiety are fluorophores.
7. The method of claim 5 , wherein said reporter moiety is a fluorophore and said quencher moiety is a dark quencher.
8. The method of claim 5 , wherein said reporter and quencher moiety are separated by a nuclease cleavage site.