CRISPR effector system based diagnostics for malaria detection
The embodiments disclosed herein utilized RNA targeting effectors to provide a robust CRISPR-based diagnostic with attomolar sensitivity. Embodiments disclosed herein can detect broth DNA and RNA with comparable levels of sensitivity and can differentiate targets from non-targets based on single base pair differences. Moreover, the embodiments disclosed herein can be prepared in freeze-dried format for convenient distribution and point-of-care (POC) applications. Such embodiments are useful in multiple scenarios in human health including, for example, viral detection, bacterial strain typing, sensitive genotyping, and detection of disease-associated cell free DNA.
1. A nucleic acid detection system comprising:
a CRISPR system comprising a Type VI Cas effector protein exhibiting collateral activity and one or more guide RNAs capable of binding one or more target nucleic acid sequences of a mosquito-borne parasite, each guide RNA comprising a guide sequence capable of hybridizing to a complementary target nucleic acid sequence of a mosquito-borne parasite and subsequently forming a CRISPR complex of the Type VI Cas effector protein with each guide RNA comprising the guide sequence hybridized to the complementary target nucleic acid sequence; and
an RNA-based masking construct.
2. The detection system of claim 1 , wherein the mosquito-borne parasite is selected from the genus Plasmodium.
3. The detection system of claim 2 , wherein the Plasmodium is selected from the species Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae , and Plasmodium knowlesi.
4. The detection system of claim 1 , wherein the one or more target nucleic acid sequences are DNA or RNA and wherein the one or more target nucleic acid sequences can be used for species or strain identification.
5. The detection system of claim 4 , wherein
when the one or more target nucleic acid sequences are DNA sequences, the DNA sequences are selected from gene sequences that are conserved within species but divergent between species, and
when the one or more target nucleic acid sequence are RNA sequences, the RNA sequences are selected from transcripts of said gene sequences that are conserved within species but divergent between species.
6. The detection system of claim 4 , wherein
when the one or more target nucleic acid sequences are DNA, the DNA is selected from highly expressed gene sequences, highly conserved gene sequences, gene sequences that are present in multiple copies in the genome, and combinations thereof; and
when the target nucleic acid sequence is RNA, the RNA is selected from transcripts of said highly expressed gene sequences, transcripts of said highly conserved gene sequences, transcripts of said gene sequences that are present in multiple copies in the genome, and combinations thereof.
7. The detection system of claim 4 , wherein the one or more target nucleic acid sequences are selected from a transcript of a ribosomal gene cytochrome b (CYTB), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), Histone H2B, enolase, and lactate dehydrogenase (LDH).
8. The detection system of claim 7 , wherein the transcript of a ribosomal gene is an 18S ribosomal DNA transcript.
9. The detection system of claim 4 , wherein the one or more target nucleic acid sequences can be used for the detection of one or more parasite drug-resistance markers; and wherein the drug is selected from aryl-amino alcohols, antifolate drugs, pyrimethamine, atemisins drugs, proguanil, the combination of atovaquone and proguanil, and combinations thereof.
10. The detection system of claim 9 , wherein the aryl-amino alcohols are selected from quinine, quinine derivatives, lipophilic hydroxynapthoquinone, and combinations thereof.
11. The detection system of claim 10 , wherein the quinine derivatives are selected from chloroquine, amodiaquine, mefloquine, piperaquine, lumefantrine, primaquine, and combinations thereof.
12. The detection system of claim 10 , wherein the lipophilic hydroxynaphthoquinone analog is atovaquone.
13. The detection system of claim 9 , wherein the antifolate drugs are selected from sulfa drugs.
14. The detection system of claim 13 , wherein the sulfa drugs are selected from sulfadoxine, dapsone, and combinations thereof.
15. The detection system of claim 4 , wherein the one or more target nucleic acid sequences are selected from sequences encoding transporter proteins and sequences encoding proteins involved in the translocation of protons across the inner mitochondrial membrane.
16. The detection system of claim 15 , wherein the transporter proteins are selected from a protein from the drug/metabolite transporter family, the ATP-binding cassette (ABC) protein involved in substrate translocation, and combinations thereof.
17. The detection system of claim 16 , wherein the ATP-binding cassette (ABC) protein involved in substrate translocation is selected from the ABC transporter C subfamily, the Na+/H+ exchanger, and combinations thereof.
18. The detection system of claim 15 , wherein the proteins involved in the folate pathway are selected from the dihydropteroate synthase, the dihydrofolate reductase activity, the dihydrofolate reductase-thymidylate synthase, and combinations thereof.
19. The detection system of claim 15 , wherein the one or more target nucleic acid sequences comprise a mitochondrial gene sequence.
20. The detection system of claim 19 , wherein the protein involved in the translocation of protons across the inner mitochondrial membrane is the cytochrome b complex.
21. The detection system of claim 4 , wherein the one or more target nucleic acid sequences are selected from the P. falciparum chloroquine resistance transporter gene (pfcrt), the P. falciparum multidrug resistance transporter I (pfmdr1), the P. falciparum multidrug resistance-associated protein gene (Pfmrp), the P. falciparum Na+/H+ exchanger gene (pfnhe), the P. falciparum Ca2+ transporting ATPase 6 (pfatp6) gene, the P. falciparum dihydropteroate synthase (pfdhps) gene, the P. falciparum dihydrofolate reductase activity (pfdhpr) gene, the P. falciparum dihydrofolate reductase-thymidylate synthase (pfdhfr) gene, the cytochrome b gene, and functional heterologous genes thereof in other Plasmodium species.
22. The detection system of claim 21 , wherein the target sequence is selected from pfcrt, pfmdr1, pfdhjr, Cytochrome b, gtp cyclohydrolase, and Kelch13.
23. A method for detecting a mosquito-borne parasite by detecting one or more target nucleic acids in one or more samples, comprising:
distributing a sample or set of samples into one or more individual discrete volumes, the individual discrete volumes comprising the nucleic acid detection system of claim 1 ;
incubating the sample or set of samples under conditions sufficient to allow binding of the one or more guide RNAs to the one or more target nucleic acid sequences;
activating the Type VI Cas effector protein via binding of the one or more guide RNAs to the one or more target nucleic acid sequences, wherein activating the Type VI Cas effector protein results in modification of the RNA-based masking construct such that a detectable positive signal is generated; and
detecting the detectable positive signal, wherein detecting the detectable positive signal indicates a presence of one or more target nucleic acids in the sample.
24. The method of claim 23 , wherein the one or more target nucleic acid sequences are a one or more target DNA sequences and the method further comprises binding the one or more target DNA sequences with a primer comprising an RNA polymerase site.
25. A polypeptide detection system comprising:
a CRISPR system comprising a Type VI Cas effector protein and one or more guide RNAs capable of binding one or more trigger RNAs of a mosquito-borne parasite, each guide RNA comprising a guide sequence capable of hybridizing with a complementary trigger RNA sequence and subsequently forming a CRISPR complex of the Type VI Cas effector protein with each guide RNA comprising the guide sequence hybridized to the complementary trigger RNA;
an RNA-based masking construct; and
one or more detection aptamers capable of binding one or more target polypeptides of a mosquito-borne parasite, each detection aptamer comprising a masked RNA polymerase promoter binding site or a masked primer binding site and capable of binding a corresponding target polypeptide of a mosquito-borne parasite.
26. A method for detecting a mosquito-borne parasite by detecting one or more target polypeptides in one or more samples, comprising: distributing a sample or set of samples into a set of individual discrete volumes, the individual discrete volumes comprising the polypeptide detection system of claim 25 ;
incubating the sample or set of samples under conditions sufficient to allow binding of the one or more detection aptamers to the one or more target polypeptides, wherein binding of one of the detection aptamers to one of the target polypeptides exposes the RNA polymerase binding site or primer binding site of the detection aptamer resulting in generation of a trigger RNA;
activating the Type VI Cas effector protein via binding of the one or more guide RNAs to the one or more trigger RNAs, wherein activating the Type VI Cas effector protein results in modification of the masking construct such that a detectable positive signal is produced; and
detecting the detectable positive signal, wherein detecting the detectable positive signal indicates a presence of one or more target polypeptides in a sample.
27. The method of claim 23 or 26 , further comprising amplifying the one or more nucleic acid sequences or the one or more trigger RNAs by nucleic acid sequence based amplification (NASBA) or recombinase polymerase amplification (RPA).
28. The method of claim 23 or 26 , wherein the sample is a biological sample or an environmental sample, and wherein the biological sample is a blood, plasma, serum, urine, stool, sputum, mucous, lymph fluid, synovial fluid, bile, ascites, pleural effusion, seroma, saliva, cerebrospinal fluid, aqueous or vitreous humor, or any bodily secretion, a transudate, an exudate, or fluid obtained from a joint, or a swab of skin or mucosal membrane surface.
29. The method of claim 28 , wherein the sample is blood, plasma or serum obtained from a human patient.
30. The method of claim 28 , wherein the sample comprises a sample obtained from one or more mosquitoes, such as saliva obtained from mosquito.
31. The method of claim 23 or 26 , wherein the one or more guide RNAs are designed to detect a single nucleotide polymorphism in a target RNA or DNA, or a splice variant of an RNA transcript.
32. The method of claim 23 or 26 , wherein the one or more guide RNAs are designed to bind to one or more target nucleic acids that are diagnostic for a disease state.
33. The method of claim 23 or 26 , wherein the one or more guide RNAs are designed to bind to cell free nucleic acids.
34. A method for the prophylaxis of a mosquito-borne pathology in a human patient, comprising detecting a mosquito-borne parasite according to the method of claim 23 or 26 .
35. A method for the diagnosis of a mosquito-borne pathology in a human patient, comprising detecting a mosquito-borne parasite according to the method of claim 23 or 26 .
36. A method for the treatment of mosquito-borne pathology in a human patient, comprising (a) detecting a mosquito-borne parasite according to the method of claim 23 or 26 ; (b) determining a course of treatment based on the detection results obtained at step (a); (c) treating said patient in accordance with the course of treatment determined at step (b).
37. The method for treatment of claim 36 , wherein step (a) comprises the detection of a parasite drug-resistance marker; and wherein steps (a) to (c) are repeated at least once.
38. The method for treatment of claim 36 , wherein the parasite is Plasmodium and the pathology is malaria.
39. The method for treatment of claim 36 , wherein the patient is at risk of experiencing an infection, a primo-infection, a relapse, a re-infection, an over-infection, a recrudescence, or multiple infections.
40. A method for the monitoring of a mosquito population in a geographic area, comprising detecting a mosquito-borne parasite according to the method of claim 23 or 26 .
41. The method for monitoring of claim 40 , comprising the monitoring of one or more parasite drug resistance markers.
42. A method for the surveillance of a mosquito-borne pathology in a geographic area, comprising detecting a mosquito-borne parasite according to the method of claim 23 or 26 .