METHODS AND SYSTEMS FOR RNA OR DNA DETECTION AND SEQUENCING

Abstract

Methods, systems, and kits described herein are for detecting and sequencing nucleic acids (e.g., RNA) in a wide range of samples such as samples with low concentrations of nucleic acid, samples with degraded nucleic acid, samples that would not otherwise be amenable to conventional sequencing or RNA detection methods, poor quality samples, high quality samples in which rare mutations are sought, formalin-fixed paraffin-embedded samples, blood samples, etc. The methods of the present invention may use paired, large panels of primers to amplify many short fragments that overlap between but not within each panel. Each panel's amplicon set may fill the gaps between those of the opposing panel, thereby providing complete gene or genomic coverage. A preliminary, multiplex amplification step amplifies target nucleic acid for all downstream reactions such as Sanger sequencing, cloning, and NGS.

Claims

1. A method of sequencing a target nucleic acid sequence in a sample, said method comprising: a) aliquoting the sample into at least two portions; b) subjecting each sample portion to a polymerase chain reaction (PCR) amplification using a thermostable polymerase and one or more primer pairs, wherein each sample portion have different primer pairs; wherein the one or more primer pairs in each sample portion amplify a fragment of the target nucleic acid sequence, wherein within each sample portion, there are non-overlapping amplified fragments; wherein the amplified fragments overlap between but not within each sample portion; and c) sequencing the amplified fragment from (b).

2. The method of claim 1, wherein the overlapping amplified fragments between each sample portion fill in non-overlapping gaps in the target nucleic acid sequence such that a complete gene or genomic coverage is obtained.

3. The method of claim 1, wherein the target nucleic acid sequence is a target RNA sequence or a target DNA sequence.

4. The method of claim 3, wherein if the target nucleic acid sequence is a target RNA sequence, the method further comprises subjecting each portion of the sample from (a) to a reverse transcription (RT) reaction; wherein the reverse transcription reaction in each sample portion comprises i) a reverse transcriptase and ii) a primer for reverse transcription of all fragments to be amplified.

5. The method of claim 4, wherein the primer comprises one or more primers for reverse transcription of fragments to be amplified, a first primer of the one or more primer pairs, or a combination thereof.

6. The method of claim 5, wherein: i) if the reverse transcription reaction comprises the first primer, then the second primer of the primer pair is added in b); or ii) if the reverse transcription reaction does not have the first primer, then both primers of the primer pair are added in b).

7. The method of claim 1, further comprising subjecting each sample portion in (a) to multiplex PCR amplification using the thermostable polymerase and two or more primer pairs prior to step (b).

8. The method of claim 1, wherein the PCR amplification comprises a multiplex PCR amplification, wherein the multiplex PCR amplification comprises two or more primer pairs.

9. The method of claim 1, wherein the sample comprises a formalin-fixed paraffin-embedded (FFPE), serum, plasma, nasal, oral, dental, throat, gargle, fecal, saliva, tear, sweat, breath, blood, hair, semen, vaginal, pus, organ, tissue, cell, urine, biopsy, autopsy, wastewater, soil, environmental, air, air filter sample, etc.

10. A kit for use in a method according to claim 1, wherein the kit comprises at least two primer pairs, each pair comprising a first primer and a second primer, wherein the at least two primer pairs are separated into at least two primer pools such that each primer pool has different primer pairs; wherein the primer pairs in each of the at least two primer pools amplify fragments of the target nucleic acid sequence, wherein within each primer pool there are non-overlapping amplified fragments.

11. A kit for detecting and sequencing a target nucleic acid sequence in a sample, the kit comprising: a) two or more primer pairs, each pair comprising a first primer and a second primer, wherein the at least two primer pairs are separated into at least two primer pools such that each primer pool has different primer pairs, wherein the primer pairs in each of primer pools amplify fragments of the target nucleic acid sequence; and b) a set of instructions for amplifying the target nucleic acid sequence in the sample, wherein the instructions comprise: i) aliquoting the sample into at least two portions; and ii) subjecting each sample portion to a polymerase chain reaction (PCR) amplification using a thermostable polymerase and one or more primer pairs, wherein each sample portion have different primer pairs; wherein the one or more primer pairs in each sample portion amplify a fragment of the target nucleic acid sequence, wherein within each sample portion, there are non-overlapping amplified fragments; wherein the amplified fragments overlap between but not within each sample portion.

12. The kit of claim 11, wherein the target nucleic acid sequence is a target RNA sequence or a target DNA sequence.

13. The kit of claim 12, wherein if the target nucleic acid sequence is a target RNA sequence, the method further comprises subjecting each portion of the sample from (i) to a reverse transcription (RT) reaction.

14. The kit of claim 13, wherein the reverse transcription reaction comprises i) a reverse transcriptase and ii) a primer for reverse transcription of all fragments to be amplified; wherein the primer comprises one or more primers for reverse transcription of fragments to be amplified, a first primer of the one or more primer pairs, or a combination thereof.

15. The kit of claim 14, wherein: i) if the reverse transcription reaction comprises the first primer, then the second primer of the primer pair is added in ii); or ii) if the reverse transcription reaction does not have the first primer, then both primers of the primer pair are added in ii).

16. The kit of claim 11, wherein the first primer comprises a reverse primer, and the second primer comprises a corresponding forward primer.

17. The kit of claim 11, further comprising the reverse transcriptase, the thermostable polymerase, or a combination thereof, wherein the thermostable polymerase comprises a Taq polymerase.

18. The kit of claim 11, wherein the instructions further comprise detecting or sequencing amplified fragments of (iii).

19. The kit of claim 11, wherein the target nucleic acid sequence is an RNA sequence, wherein the RNA sequence comprises a sequence from a human immunodeficiency virus (HIV), a hepatitis C virus (HCV), a hepatitis B virus (HBV), an influenza virus, an ebolavirus, or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

20. An amplified product produced by a method of amplifying a target nucleic acid sequence in a sample, wherein the amplified product comprises a plurality of amplified fragments, wherein the method comprises: a) aliquoting the sample into at least two portions; and b) subjecting each sample portion to a polymerase chain reaction (PCR) amplification using a thermostable polymerase and one or more primer pairs, wherein each sample portion has different primer pairs; wherein the one or more primer pairs in each sample portion amplify a fragment of the target nucleic acid sequence, wherein within each sample portion, there are non-overlapping amplified fragments.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The features and advantages of the present invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which:

[0027] FIG. 1 shows a non-limiting example of the methods and systems described herein.

[0028] FIG. 2 shows a schematic view of an example of nucleic acid amplification methods of the present invention (and alignment of the amplicons).

[0029] FIG. 3 (PRIOR ART) shows a schematic view of conventional amplification methods used for the detection and amplification of a target RNA molecule in an old, degraded, low-titer sample. Tube 1 (left tube): As an example, in this tube, there are 10.sup.13 RNA molecules, but only one molecule that is both capable of being primed by primer KG1 R and long enough to form an 80bp product when amplified with primers KG1F/KG1R. RT is performed with 10.sup.7 molecules of KG1R. There is one usable product (Tube 2, middle tube). PCR amplification is performed on a subsample (aliquot) of Tube B (e.g., 10% of Tube B) using primers KG1 F and KG1 R. There is a large chance (e.g., about a 90% chance) that this (Tube 3, right tube) will be a negative sample.

[0030] FIG. 4 shows a schematic view of the methods of the present invention used for the detection and amplification of a target molecule in an old, degraded, low-titer sample. Note that this schematic view is a simplified schematic. For example, instead of 1 pair of non-overlapping primers, there may be 10 or more (and 10 or more final amplifications). (Note the present invention is not limited to 1 pair or 10 or more pairs of primers.) Tube 1: As an example, in this tube, there are 10.sup.13 RNA molecules, but only one molecule that is both capable of being primed by primer KG1 R and long enough to form an 80bp product when amplified with primers KG1F/KG1R. In Tube 1, RT is performed with 10.sup.7 molecules of KG1R. There is one usable product. Tube 2 shows RT is then performed with 10.sup.7 molecules of KG1 R. There is one usable product. Tube 3 shows amplification with 10.sup.7 molecules of KG1F and proofreading Taq. After 20 amplification cycles, there are 105 usable products. An aliquot (e.g., 10% of the product) is transferred to Tube 4 and amplified in a PCR reaction with primers KG1 F and KG1 R. There is essentially a 100% chance that this will be a positive sample. As an example, with a 10 primer pool and 10 final reactions, there is potential to get 10 amplicons for sequencing.

DETAILED DESCRIPTION OF THE INVENTION

[0031] For purposes of summarizing the disclosure, certain aspects, advantages, and novel features of the disclosure are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiments of the disclosure. Thus, the disclosure may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0032] Additionally, although embodiments of the disclosure have been described in detail, certain variations and modifications will be apparent to those skilled in the art, including embodiments that do not provide all the features and benefits described herein. It will be understood by those skilled in the art that the present disclosure extends beyond the specifically disclosed embodiments to other alternative or additional embodiments and/or uses and obvious modifications and equivalents thereof. Moreover, while a number of variations have been shown and described in varying detail, other modifications, which are within the scope of the present disclosure, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the present disclosure. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the present disclosure. Thus, it is intended that the scope of the present disclosure herein disclosed should not be limited by the particular disclosed embodiments described herein.

[0033] As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”

[0034] Referring now to FIG. 1, FIG. 2, and FIG. 4, the present invention features methods, systems, and kits for detecting RNA or DNA in a wide range of samples, e.g., samples with low concentrations of nucleic acid, samples with degraded nucleic acid, samples that would not otherwise be amendable to conventional sequencing or RNA detection methods, poor quality samples, high-quality samples, formalin-fixed paraffin-embedded (FFPE) samples, blood samples (e.g., serum or plasma samples), breast milk samples, archival serum/plasma, etc. The present invention also features methods, systems, and kits for sequencing nucleic acids (e.g., RNA or DNA) in said samples. The present invention also features methods of detecting or sequencing viral nucleic acid.

[0035] Methods of the present invention may be used for the detection and phylogenetically relevant amplification of pathogens (e.g., RNA viruses) for which sequence data can only be guessed and are difficult, fractured, and low titer samples. For example, when attempting to detect and amplify sequences from, for example, fifty-year-old HIV samples, modern sequences can be of only limited use in designing primers.

[0036] The present invention features a method of sequencing a target nucleic acid sequence in a sample. The method may comprise a) aliquoting the sample into at least two portions, b) subjecting each sample portion to a polymerase chain reaction (PCR) amplification (e.g., a multiplex PCR reaction) using a thermostable polymerase and one or more primer pairs, and c) sequencing the amplified fragment from (b).

[0037] In some embodiments, the present invention features a method of sequencing a target nucleic acid sequence in a sample. The method may comprise a) aliquoting the sample into at least two portions, b) subjecting each sample portion to a multiplex polymerase chain reaction (PCR) amplification using a thermostable polymerase and one or more primer pairs, and c) subjecting each sample portion in b) to PCR amplification (e.g., a multiplex PCR reaction) using the thermostable polymerase and one or more primer pairs; and d) sequencing the amplified fragment from (c).

[0038] In some embodiments, the present invention features a method of sequencing a target nucleic acid sequence in a sample. The method may comprise a) aliquoting the sample into at least two portions, b) subjecting each portion of the sample to a reverse transcription (RT) reaction, c) adding at least one primer (e.g., a first primer; e.g., a reverse primer) from a primer pair to each sample portion, wherein the sample portions have different primer pairs, d) subjecting each sample portion to a multiplex polymerase chain reaction (PCR) amplification using a thermostable polymerase and both primers of the primer pair, e) subjecting each sample portion in (d) to PCR amplification using the thermostable polymerase and the primer pair.

[0039] In some embodiments, the method comprises a) aliquoting the sample into at least two portions, b) subjecting each portion of the sample to a reverse transcription (RT) reaction, c) adding at least one primer from a primer pair to each sample portion, wherein the sample portions have different primer pairs, d) subjecting each sample portion to a multiplex polymerase chain reaction (PCR) amplification using a thermostable polymerase and both primers of the primer pair, and e) subjecting each sample portion in (d) to PCR amplification using the thermostable polymerase and the primer pair.

[0040] The aforementioned methods may further comprise detecting and sequencing amplified products from the final step.

[0041] Each primer pair comprises a first primer and a corresponding second primer. In some embodiments, the first primer comprises a reverse primer, and the second primer comprises a corresponding forward primer.

[0042] Each sample portion has different primer pairs (i.e., different sets of primers). In some embodiments, the one or more primer pairs in each sample portion amplify a fragment of the target nucleic acid sequence. Within each sample portion, there are non-overlapping amplified fragments, such that there are gaps between the non-overlapping amplified fragments. In some embodiments, the amplified fragments overlap between each sample portion but not within each sample portion.

[0043] Without wishing to limit the present invention to any theory or mechanism, it is believed that the overlapping amplified fragments between each sample portion fill in non-overlapping gaps in the target nucleic acid sequence such that a complete gene or genomic coverage is obtained (FIG. 1).

[0044] In some embodiments, the methods herein comprise aliquoting the sample into at least three portions. In some embodiments, the methods herein comprise aliquoting the sample into at least four portions. In some embodiments, the methods herein comprise aliquoting the sample into at least five portions. In some embodiments, the methods herein comprise aliquoting the sample into at least ten portions. In some embodiments, the methods herein comprise aliquoting the sample into at least twenty portions. In some embodiments, the methods herein comprise aliquoting the sample into at least fifty portions. In some embodiments, the methods herein comprise aliquoting the sample into at least 100 portions. The present invention is not limited to the aforementioned examples, and more than 100 sample portions may be used in accordance with the present invention.

[0045] In some embodiments, the methods herein comprise aliquoting the sample into two portions. In some embodiments, the methods herein comprise aliquoting the sample into three portions. In some embodiments, the methods herein comprise aliquoting the sample into four portions. In some embodiments, the methods herein comprise aliquoting the sample into five portions. In some embodiments, the methods herein comprise aliquoting the sample into ten portions. In some embodiments, the methods herein comprise aliquoting the sample into twenty portions. In some embodiments, the methods herein comprise aliquoting the sample into fifty portions. In some embodiments, the methods herein comprise aliquoting the sample into 100 portions. The present invention is not limited to the aforementioned examples, and more than 100 sample portions may be used in accordance with the present invention.

[0046] In some embodiments, the target nucleic acid sequence is a target RNA sequence or a target DNA sequence. If the target nucleic acid sequence is a target RNA sequence, the methods described herein further comprise subjecting each portion of the sample from (a) (e.g., after aliquoting the sample into portions) to a reverse transcription (RT) reaction. In some embodiments, the reverse transcription reaction in each sample portion comprises i) a reverse transcriptase and ii) a primer for reverse transcription of all fragments to be amplified in subsequent PCR amplification(s).

[0047] The primer may comprise one or more primers (e.g., a set of primers) for reverse transcription of fragments to be amplified, or a first primer of the one or more primer pairs (e.g., a first primer from each of the one or more primer pairs). In some embodiments, the primer comprises a random primer (e.g., a random hexamer). In some embodiments, the primer for the reverse transcription may comprise both the set of primers and the first primer of the one or more primer pairs.

[0048] In some embodiments, the reverse transcription reaction in each sample portion comprises i) a reverse transcriptase and ii) a first primer from each of the one or more primer pairs. In some embodiments, the reverse transcription reaction in each sample portion comprises i) a reverse transcriptase and ii) a random primer (e.g., a random hexamer). In some embodiments, the reverse transcription reaction in each sample portion comprises i) a reverse transcriptase and ii) both a first primer from each of the one or more primer pairs and a random primer.

[0049] In some embodiments, if the reverse transcription reaction comprises the first primer of the one or more primer pairs, then the second primer of the primer pair is added to the PCR amplification (e.g., the PCR amplification in step b). In some embodiments, if the reverse transcription reaction does not have the first primer, then both primers of the primer pair are added to the PCR amplification (e.g., the PCR amplification in step b). In some embodiments, if the reverse transcription reaction comprises the random primer (e.g., a random hexamer), then both primers of the primer pair are added to the PCR amplification (e.g., the PCR amplification in step b).

[0050] The present invention may also feature a kit for the use in methods described herein. The kit may comprise at least two primer pairs, each pair comprising a first primer and a second primer. The at least two primer pairs are separated into at least two primer pools (e.g., panels of primers) such that each primer pool has different primer pairs. In some embodiments, the primer pairs in each of the at least two primer pools amplify fragments of the target nucleic acid sequence. Within each primer pool, there are non-overlapping amplified fragments. In some embodiments, the amplified fragments overlap between the primer pools (e.g., panels) but not within the primer pools (e.g., panels).

[0051] The present invention may also feature a kit for detecting and sequencing a target nucleic acid sequence in a sample. The kit may comprise two or more primer pairs, each pair comprising a first primer and a second primer. The at least two primer pairs are separated into at least two primer pools (e.g., a panel of primers) such that each primer pool has different primer pairs. In some embodiments, the primer pairs in each of the at least two primer pools amplify fragments of the target nucleic acid sequence. Within each primer pool, there are non-overlapping amplified fragments. In some embodiments, the amplified fragments overlap between the primer pools (e.g., panels) but not within the primer pools (e.g., panels). The kit may further comprise a set of instructions (e.g., methods described herein) for amplifying the target nucleic acid sequence in the sample.

[0052] In some embodiments, the instructions comprise a) aliquoting the sample into at least two portions, b) subjecting each sample portion to a polymerase chain reaction (PCR) amplification (e.g., a multiplex PCR amplification) using a thermostable polymerase and one or more primer pairs, and optionally subjecting each sample portion in (b) to PCR amplification using the thermostable polymerase and one or more primer pairs. Each sample portion has different primer pairs. In some embodiments, the one or more primer pairs in each sample portion amplify a fragment of the target nucleic acid sequence. The instructions may further comprise detecting or sequencing amplified fragments from either of the PCR amplification steps. In some embodiments, within each sample portion, there are non-overlapping amplified fragments. In some embodiments, the amplified fragments overlap between but not within each sample portion.

[0053] The kit may further comprise a reverse transcriptase, a thermostable polymerase, or a combination thereof. In some embodiments, the thermostable polymerase comprises a Taq polymerase.

[0054] Methods and kits of the present invention feature using panels of primer pairs (e.g., primer pools). For example, in some embodiments, the methods of the present invention use panels (e.g., primer pools; e.g., eight to ten panels) of primer pairs (e.g., degenerate primers, non-degenerate primers or a combination thereof) for detection (e.g., sequencing) of a target nucleic acid sequence. In some embodiments, the methods of the present invention use panels (e.g., primer pools; e.g., eight to ten panels) of non-degenerate primers (or a mix of degenerate and non-degenerate primers) for detection (e.g., sequencing) of a target nucleic acid sequence.

[0055] In some embodiments, the methods and/or kits of the present invention use 50-200 primer pairs (e.g., degenerate, non-degenerate, a combination thereof) for near full-length sequencing. Methods and/or kits of the present invention may also feature a pre-amplification step of RT products so as to increase titer prior to final PCR. This helps allow for adequate sequence yield from some samples that have immeasurably low yields of RNA and/or are highly fractured. Because methods of the present invention may be designed to amplify 1000-1500 bp of sequence from a given aliquot of native RNA, the sample size may be much less a factor than if each PCR fragment was generated from a separate RT reaction. In the case of the 1978 and 1979 serum samples mentioned above, a near full-length sequence could be generated using only 30 μl of 50 μl serum eluate generated from 50-100 μl of serum.

[0056] The present invention also features methods and kits for detecting or sequencing genetic variations of a target nucleic acid sequence, e.g., RNA (e.g., variations of the RNA within the same sample), e.g., detecting within-host viral genetic variation with phenotypic consequences (e.g., on drug resistance, pathogenesis, cell/tissue tropism, transmissibility to secondary hosts, etc.). Without wishing to limit the present invention to any theory or mechanism, it is believed that the methods of the present invention may help to detect genetic variations that are not necessarily apparent when large amplicons are generated. For example, variations in primer regions in some clones may prevent them from being amplified. Also, the effective template number of large amplicons may be much smaller than small amplicons (e.g., there may only be one or a few template molecules 1000 nt in length in a degraded sample, whereas there may be more template molecules shorter in length). In the present invention, if several 100 nt regions within that same region are separately assayed, there may be orders of magnitude more template molecules and thus a chance to observe within-patient diversity that may otherwise be invisible when aiming for a larger fragment.

[0057] As previously discussed, the methods of the present invention feature targeting several small fragments of the target nucleic acid sequence, e.g., an RNA. For example, in some embodiments, the fragment that is targeted is about 70 nt in length. In some embodiments, the fragment is about 80 nt in length. In some embodiments, the fragment is about 90 nt in length. In some embodiments, the fragment is about 100 nt in length. In some embodiments, the fragment is about 110 nt in length. In some embodiments, the fragment is from 65 to 90 nt in length. In some embodiments, the fragment is from 70 to 100 nt in length. In some embodiments, the fragment is from 70 to 110 nt in length. In some embodiments, the fragment is from 80 to 100 nt in length. In some embodiments, the fragment is from 100 to 200 nt in length. In some embodiments, the fragment is from 70 to 200 nt in length. The present invention is not limited to the aforementioned examples. For example, in some embodiments, the fragment is more than 200 nt in length, e.g., from 200 to 250 nt, from 200 to 300 nt, from 300 to 400 nt, from 400 to 500 nt, etc. Fragment size may depend on the quality of the sample.

[0058] In some embodiments, at least two primer pairs are used per primer pool (e.g., panel). In some embodiments, at least three primer pairs are used per primer pool (e.g., panel). In some embodiments, at least four primer pairs are used per primer pool (e.g., panel). In some embodiments, at least five primer pairs are used per primer pool (e.g., panel). In some embodiments, at least six primer pairs are used per primer pool (e.g., panel). In some embodiments, at least seven primer pairs are used per primer pool (e.g., panel). In some embodiments, at least eight primer pairs are used per primer pool (e.g., panel). In some embodiments, at least nine primer pairs are used per primer pool (e.g., panel). In some embodiments, at least ten primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 20 primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 30 primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 40 primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 50 primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 75 primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 100 primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 150 primer pairs are used per primer pool (e.g., panel). In some embodiments, at least 200 primer pairs are used per primer pool (e.g., panel). The present invention is not limited to the aforementioned examples, and more than 200 primer pairs may be used per primer pool (e.g., panel).

[0059] In some embodiments, two primer pairs are used per primer pool (e.g., panel). In some embodiments, three primer pairs are used per primer pool (e.g., panel). In some embodiments, four primer pairs are used per primer pool (e.g., panel). In some embodiments, five primer pairs are used per primer pool (e.g., panel). In some embodiments, six primer pairs are used per primer pool (e.g., panel). In some embodiments, seven primer pairs are used per primer pool (e.g., panel). In some embodiments, eight primer pairs are used per primer pool (e.g., panel). In some embodiments, nine primer pairs are used per primer pool (e.g., panel). In some embodiments, ten primer pairs are used per primer pool (e.g., panel). In some embodiments, 11 primer pairs are used per primer pool (e.g., panel). In some embodiments, 12 primer pairs are used per primer pool (e.g., panel). In some embodiments, 13 primer pairs are used per primer pool (e.g., panel). In some embodiments, 14 primer pairs are used per primer pool (e.g., panel). In some embodiments, 15 primer pairs are used per primer pool (e.g., panel). In some embodiments, 16 primer pairs are used per primer pool (e.g., panel). In some embodiments, 17 primer pairs are used per primer pool (e.g., panel). In some embodiments, 18 primer pairs are used per primer pool (e.g., panel). In some embodiments, 19 primer pairs are used per primer pool (e.g., panel). In some embodiments, 20 primer pairs are used per primer pool (e.g., panel). In some embodiments, 21 primer pairs are used per primer pool (e.g., panel). In some embodiments, 22 primer pairs are used per primer pool (e.g., panel). In some embodiments, 23 primer pairs are used per primer pool (e.g., panel). In some embodiments, 24 primer pairs are used per primer pool (e.g., panel). In some embodiments, 25 primer pairs are used per primer pool (e.g., panel). In some embodiments, 26 primer pairs are used per primer pool (e.g., panel). In some embodiments, 27 primer pairs are used per primer pool (e.g., panel). In some embodiments, 28 primer pairs are used per primer pool (e.g., panel). In some embodiments, 29 primer pairs are used per primer pool (e.g., panel). In some embodiments, 30 primer pairs are used per primer pool (e.g., panel). In some embodiments, 40 primer pairs are used per primer pool (e.g., panel). In some embodiments, 50 primer pairs are used per primer pool (e.g., panel). In some embodiments, 100 primer pairs are used per primer pool (e.g., panel). In some embodiments, 200 primer pairs are used per primer pool (e.g., panel). As previously discussed, the present invention is not limited to the aforementioned examples, and more than 200 primer pairs may be used.

[0060] The primer pairs may be divided into at least two primer pools. In some embodiments, two primer pools are used. In some embodiments, three primer pools are used. In some embodiments, four primer pools are used. In some embodiments, five primer pools are used. In some embodiments, six primer pools are used. In some embodiments, seven primer pools are used. In some embodiments, eight primer pools are used. In some embodiments, nine primer pools are used. In some embodiments, ten primer pools are used. In some embodiments, more than ten primer pools are used. In some embodiments, primer pools have about ten primers each.

[0061] For example, in some embodiments, when attempting to detect the presence of a particular RNA, about 8 to 10 primer pairs may be used. In some embodiments, when attempting to sequence a particular RNA, about 50 primer pairs may be used. However, the present invention is not limited to the aforementioned examples.

[0062] In some embodiments, the target nucleic acid sequence is a whole genome. In some embodiments, the target nucleic acid sequence is a viral nucleic acid. In some embodiments, the target nucleic acid sequence is a whole viral genome. In some embodiments, the method and kits described herein detect genetic variations in the viral nucleic acid.

[0063] In some embodiments, the target nucleic acid sequence is an RNA sequence, wherein the RNA sequence comprises a sequence from a human immunodeficiency virus (HIV), a hepatitis C virus (HCV), a hepatitis B virus (HBV), an influenza virus, an ebolavirus, or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

[0064] In some embodiments, the sample may comprise a biological sample or an environmental sample. In some embodiments, the sample comprises a formalin-fixed paraffin-embedded (FFPE) sample, a serum sample, a plasma sample, a nasal sample, an oral sample, a dental sample (e.g., plaque), a throat sample, a gargle sample, a fecal sample, a saliva sample, a tear sample, a sweat sample, a breath sample, a blood sample, a hair sample, a semen sample, a vaginal sample (e.g., a cervicovaginal lavage), a pus sample, a urine sample. In some embodiments, the sample may comprise a tissue sample or an organ sample. In some embodiments, the sample may be collected during a biopsy or an autopsy (e.g., a biopsy sample or an autopsy sample). In some embodiments, the sample may comprise a wastewater sample, a soil sample, an environmental sample, an air sample, or an air filter sample.

[0065] As previously discussed, the present invention may help sequence RNAs in historical samples of unknown subtypes, as well as sequence variants of an RNA. Without wishing to limit the present invention to any theory or mechanism, it is believed that the use of multiple, small fragments may be advantageous for sequencing unknown subtypes or RNAs with polymorphisms.

[0066] The present invention may also feature an amplified product produced by a method of amplifying a target nucleic acid sequence in a sample, wherein the amplified product comprises a plurality of amplified fragments. The method may comprise a) aliquoting the sample into at least two portions, b) subjecting each sample portion to a polymerase chain reaction (PCR) amplification (e.g., a multiplex PCR reaction) using a thermostable polymerase and one or more primer pairs, and c) sequencing the amplified fragment from (b).

[0067] In some embodiments, the method comprises a) aliquoting the sample into at least two portions, b) subjecting each sample portion to a multiplex polymerase chain reaction (PCR) amplification using a thermostable polymerase and both primers of the primer pair (e.g., a pre-amplification reaction), c) subjecting each sample portion in (b) to PCR amplification using the thermostable polymerase and the primer pair. The primers of the primer pair in each sample portion amplify a fragment of the target nucleic acid sequence. Within each sample portion, there are non-overlapping amplified fragments. In some embodiments, within each sample portion, there are non-overlapping amplified fragments. In some embodiments, the amplified fragments overlap between but not within each sample portion

[0068] In some embodiments, the method comprises a) aliquoting the sample into at least two portions, b) subjecting each portion of the sample to a reverse transcription (RT) reaction, c) adding at least one primer from a primer pair to each sample portion, wherein the sample portions have different primer pairs, d) subjecting each sample portion to a multiplex polymerase chain reaction (PCR) amplification using a thermostable polymerase and both primers of the primer pair, e) subjecting each sample portion in (d) to PCR amplification using the thermostable polymerase and the primer pair. The primers of the primer pair in each sample portion amplify a fragment of the target nucleic acid sequence. Within each sample portion, there are non-overlapping amplified fragments. In some embodiments, within each sample portion, there are non-overlapping amplified fragments. In some embodiments, the amplified fragments overlap between but not within each sample portion.

Example 1—Plasma/Serum Samples

[0069] Example 1 describes an example of a protocol for plasma/serum samples. The present invention is not limited to the details of Example 1. This example describes a procedure for working up a sample using 40 overlapping primer pairs designed to generate products of approximately 200 bp. This will provide 6000+ bp of sequence. The actual amount of sequence is a function of how much overlap is designed into the primers. For FFPE samples or severely degraded liquid samples, 70-100 bp primer pairs may be designed. High quality proof-reading Taq is used. This protocol uses Promega Goscript and RNAsin plus for RT. Taq is Accustart.

[0070] Below shows a non-limiting example of 4 primer pools (A, B, C, D) and each comprises different primer pairs. Each primer pair within a primer pool amplifies non-overlapping fragments; however, the amplified fragments between the 4 primer pools (A, B, C, and D) overlap, such that a whole sequence of a target nucleic acid may be obtained. The following schematic may be used:

TABLE-US-00001 Pool A Pool B Pool C Pool D Primer Pair # 1 2 3 4 Primer Pair # 5 6 7 8 Primer Pair # 9 10 11 12 Primer Pair # 13 14 15 16 Primer Pair # 17 18 19 20 Primer Pair # 21 22 23 24 Primer Pair # 25 26 27 28 Primer Pair # 29 30 31 32 Primer Pair # 33 34 35 36 Primer Pair # 37 38 39 40

[0071] Reverse Transcription: For each sample to be amplified, the following may be used: Primer/dNTP: Make up 4 reverse primer/dNTP pools, one for each of A, B, C, D. (1) Primer—9 ul, (2) dNTP—3 ul. Add 4 ul of ‘A’ to wells 1 and 5 of an 8 place strip. Add ‘B’ to wells 2 and 6 and etc. Then add 6 ul sample to each of wells 1-4 and 6 ul control to wells 5-8. Mix well. Incubate at 70 C for 5′. Ice. RT mix: (1) 5× buffer—36 ul; (2) 25 mM Mg—36 ul; (3) RNasin—9 ul; (4) Goscript—9 ul. Add 10 ul per sample, mix well and incubate at 42 C for 2 hours, followed by 10′ at 85 C.

[0072] Preliminary amplification: The following may be used: Add 4 ul ‘A’ forward primer pool to wells 1 and 5 of an 8 place strip, and 4 ul of CB' to wells 2 and 6 and etc. Master mix: 10×—45ul; 50 mM Mg—18 ul; dNTP—9 ul; Taq—4 ul; Water—252 ul. 36 ul mix into each well. Add 10 ul individual RT reactions in the appropriate well. Mix well. Amplify for 30 cycles in a standard PCR program at the appropriate annealing temperature (e.g., primers may be designed around 52 degrees C.).

[0073] Final amplification: The following may be used: Make up 5×8 well strips with individual primer pairs in numerical order as in the schema below (e.g., 2 ul primer total per well). One may want one set for the sample and one for the control.

TABLE-US-00002 Well 1 Well 2 Well 3 Well 4 Well 5 Well 6 Well 7 Well 8 Strip 1 Primer Primer Primer Primer Primer Primer Primer Primer Pair 1 Pair 2 Pair 3 Pair 4 Pair 5 Pair 6 Pair 7 Pair 8 Strip 2 Primer Primer Primer Primer Primer Primer Primer Primer Pair 9 Pair 10 Pair 11 Pair 12 Pair 13 Pair 14 Pair 15 Pair 16 Strip 3 Primer Primer Primer Primer Primer Primer Primer Primer Pair 17 Pair 18 Pair 19 Pair 20 Pair 21 Pair 22 Pair 23 Pair 24 Strip 4 Primer Primer Primer Primer Primer Primer Primer Primer Pair 25 Pair 26 Pair 27 Pair 28 Pair 29 Pair 30 Pair 31 Pair 32 Strip 5 Primer Primer Primer Primer Primer Primer Primer Primer Pair 33 Pair 34 Pair 35 Pair 36 Pair 37 Pair 38 Pair 39 Pair 40

[0074] Make up 8 Master mixes, four for samples (A, B, C, D) and four for controls (A, B, C, D). Master mix: 10×—27.5 ul; 50 mM Mg—11 ul; dNTP—5.5 ul; Taq—1 ul; Pre-amp product—22 ul; Water—187 ul. Add 23 ul of Sample ‘A’ master mix to primer wells 1 and 5 of each strip, Master mix Sample ‘B’ to wells 2 and 6 and etc. as per schema above. Mix well. Amplify for 40 cycles at appropriate annealing temperature.

[0075] In some embodiments, this protocol, e.g., when used in conjunction with appropriately designed primers, may generate 70-90% of the target sequence on the first go through. Note that some products may be double banded with a contaminating human band, so some gel clipping may be required unless going to NGS sequencing. Note that when the first go round is done, there is 10 ul leftover RT reaction for each pool of each sample. This can be used to pre-amp and amp on an alternative cycling program such as a Touchdown program to generate bands that cover some of the blank spots. In some embodiments, this step is done before going to sequencing. Once sequencing is done and the sequences are lined up with the primers, new primers may be designed to match missing sequence. Note also that this protocol may help ensure that no given amplification is exposed to confounding internal primers from the primer pairs immediately upstream or downstream of the amplification. This may help ensure that mis-incorporation of primers doesn't compromise the data.

Example 2—Recovery of HIV Sequences from Degraded Archival Samples

[0076] Methods of the present invention for recovering viral RNA were used test 1970s HIV serum samples (degraded archival samples). Example 2 describes the recovery of eight near-full-length genomes from US serum samples from 1978-79—eight of the nine oldest HIV-1 group M genomes to date. Example 2 also describes recovery of the HIV-1 genome from the individual known as Patient 0′ (Auerbach et al, 1984, Am J Med 76: 487-492) (showing there is neither biological nor historical evidence he was the primary case in the US or for subtype B as a whole).

[0077] HIV-1 serological screening of serum samples from San Francisco from 1978. 2231 samples collected from the cohort of gay and bisexual men in San Francisco in 1978 (Jaffe et al., 1985, Ann Intern Med 103: 210-214) were tested, and 83 WB-positives were detected (3.7% prevalence). Samples were first screened by GS HIV-1/HIV-2 Plus O EIA (Bio-Rad Laboratories, Redmond WA) and reactive samples were further tested by WB Genetic Systems HIV-1 Western Blot (Bio-Rad Laboratories, Redmond WA).

[0078] HIV-1 nucleic acid amplification. A total of 33 samples of frozen serum previously identified as positive for antibody to HIV-1 (Stevens et al, 1986, JAMA 255: 2167-2172; Szmuness et al, 1981, Hepatology 1: 377; Koblin et al., 1992, J Epidemiology 136:646-656) were assayed from New York City; a total of 20 frozen serum samples from San Francisco (Jaffe et al., 1985, Ann Intern Med 103: 210-214), identified as part of the present study as positive for antibody to HIV-1, were assayed. The New York City samples were from 1978 and 1979 though no complete genomic sequences from 1978 were developed. The San Francisco samples were all from 1978. Additionally, a sample of PMBC and a sample of serum were both assayed; these had been collected from a single individual in 1983 (Patient 0), and the samples were stored at CDC Atlanta. Other than Patient 0, now deceased, the data recorded were unlinked to individual identifiers and the work was approved by the Human Subjects Protection Program at the University of Arizona.

[0079] Four panels of degenerate primers were designed using a suite of North American subtype B sequences. Primers were designed to be able to amplify both conserved regions and predictably variable sites. Primers within each panel were designed to generate sequence from the 5′ end of gag to the 3′ end of nef and were designed to amplify overlapping fragments. Two panels “HIVL” (N=25) and “HIVLb” (N=22) were designed to amplify fragments of ˜500-650 bases in length. Two other panels “HIVm” (N=50) and “HIVr” (N=46) were designed to amplify fragments of ˜200-320 bases in length. Nucleic acids from 100 ul aliquots of serum (or PMBCs in the case of Patient 0) were isolated using the QIAamp Viral RNA Mini Kit (Qiagen, Gaithersburg, MD) with 5mcg added carrier RNA. Serum samples were then treated with DNase I (Invitrogen, Life Technologies, Carlsbad, CA) prior to reverse transcription. PMBC nucleic acids were left untreated. Proviral DNA from Patient 0′s PMBCs was amplified with all four primer panels and from multiple separate isolations. Amplification was achieved using Invitrogen Platinum Taq DNA polymerase High Fidelity (Life Technologies, Carlsbad, CA) and run for 55 cycles at an annealing temperature of 52° C. Additionally, attempts were made to amplify longer fragments using PCR SuperMix High Fidelity (Life Technologies, Carlsbad, CA) and forward and reverse primers matched from the HIVLb primer panel for long fragment length followed by nesting with primers for slightly shorter fragment length. A single fragment of slightly more than 7000 bases was generated after multiple attempts with multiple primer combinations and cloned using the Invitrogen TOPO XL PCR Cloning Kit (Life Technologies, Carlsbad, CA). Fragments of individual clones were then amplified using HIVLb forward and reverse primers matched to give approximately 1000-base overlapping fragments and then sequenced.

[0080] Methods of the present invention using the serum samples proceeded as follows: Aliquots of isolated RNA were reverse transcribed using the GoScript Reverse Transcription System (Promega, Madison, WI) using a program of 4 cycles of 50° C. for 30′ followed by 55° C. for 30′ and an 85° C. final incubation. Primers used were pools of reverse primers from widely spaced amplicons, abrogating the possibility of incorporation of an internal primer into any given amplicon. RT products were then briefly amplified in multiplex reactions (denaturation for 3′ at 94° C. followed by 30 cycles of 94° C. for 30″, 52° C. for 30″, 68° C. for 30″, and a final extension of 68° C. for 5′) with matching forward primer pools and then amplified via single primer pairs (denaturation for 3′ at 94° C. followed by 40 cycles of 94° C. for 30″, 52° C. for 30″, 68° C. for 30″, and a final extension of 68° C. for 5′). Two separate isolates were amplified from each sample in this manner with a minimum of one amplification with each primer panel per isolate. Sequencing was performed at the University of Arizona Genetics Core using an ABI 3730XL. The Patient 0 sample contained considerable heterogeneity (mixed bases) both in proviral assembly and in viral RNA amplifications. Heterogeneity in the NY and SF samples (all sequences derived from viral RNA) was low. In all cases consensus sequences were used in the phylogenetic analyses.

Example 3—Viral Enrichment and Multiplex RT-PCR Viral Genetic Screening Assays

[0081] Example 3 describes the development of viral enrichment and multiplex RT-PCR viral genetic screening assays that are more sensitive than existing RT-PCR protocols for detection of viral RNA. The methods of the present invention could allow recovery of viral genomic information from challenging source material (e.g., specimens with low concentration of template viral RNA, samples containing no viable (culturable) virus, etc.). The methods of the present invention may be useful in conventional samples as well, e.g., for conventional samples in resource-limited settings where culturing of virus may be precluded but RT-PCR may be possible. Without wishing to limit the present invention to any theory or mechanism, it is believed that the methods of the present invention may allow for detection of viral RNA with very high sensitivity (e.g., up to 100% specificity after sequencing). Thus, this may allow for the use of the methods of the present invention in resource-limited settings (e.g., without the need for culturing viral isolates), for detecting viral RNA in low-concentration, damaged or otherwise challenging samples (e.g., pooled mosquito specimens, archival human specimens, or perhaps even municipal influent (e.g., sewage) samples), etc.

[0082] In some embodiments, the methods of the present invention feature RNA (or DNA capturing, e.g., for concentration of viral nucleic acids from large pooled samples. This may increase the chances of finding the target sequence and may be effective at sequestering target nucleic acids away from potential inhibitors.

[0083] Referring to FIG. 4, the methods further comprise using non-degenerate and/or degenerate primers directed to a wide spectrum of viral strains, which are designed to amplify 70-100 nt fragments in overlapping fashion (e.g., for FFPE samples) or 200-300 nt fragments (e.g., for serum/plasma). Primers are then pooled in non-overlapping fashion for reverse transcription, and then a ‘preliminary-amplification’ (pre-amplification) step is employed to amplify with corresponding primer mates. The pre-amplified mix is then broken up for amplification with single primer pairs. The pre-amplification step greatly increases the effective titer of the target molecules, thus increasing both sensitivity and coverage.

[0084] This technique allows for HIV detection that is not otherwise detectable using previous techniques (see FIG. 3) and for development of long sequences by alignment of overlapping short sequences in samples that would otherwise be recalcitrant to viral genome sequencing. This technique provides a greater degree of assurance that a virus can be identified in samples with very low copy number and/or damaged RNA. Without wishing to limit the present invention to any theory or mechanism, it is believed that sequencing short reads in samples that have damaged RNA increases the likelihood of detecting polymorphisms.

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[0086] Various modifications of the invention, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. Each reference cited in the present application is incorporated herein by reference in its entirety.

[0087] Although there has been shown and described the preferred embodiment of the present invention, it will be readily apparent to those skilled in the art that modifications may be made thereto which do not exceed the scope of the appended claims. Therefore, the scope of the invention is only to be limited by the following claims. Reference numbers recited in the claims are exemplary and for ease of review by the patent office only, and are not limiting in any way. In some embodiments, the figures presented in this patent application are drawn to scale, including the angles, ratios of dimensions, etc. In some embodiments, the figures are representative only and the claims are not limited by the dimensions of the figures. In some embodiments, descriptions of the inventions described herein using the phrase “comprising” includes embodiments that could be described as “consisting of”, and as such the written description requirement for claiming one or more embodiments of the present invention using the phrase “consisting of” is met.