WO2016187717A1 - Exosomes useful for genome editing - Google Patents

Abstract

Genetically modified exosomes are provided which express a nuclease genome editing system. The exosomes are useful, for example, to edit genetic defects in the treatment of genetic disease.

Description

EXOSOMES USEFUL FOR GENOME EDITING Field of the Invention

[0001] The present invention generally relates to exo somes, and more particularly, to the use of exosomes for genome editing.

Background of the Invention

[0002] Technologies for genome-wide sequence interrogation have dramatically improved the ability to identify loci associated with complex human disease. Targeted human genome editing enables functional studies of genetic variation in biology and disease, and provides tremendous potential for applications across basic science, medicine, and biotechnology. To facilitate genome editing, technologies such as Zinc-Finger Nucleases (ZFN) and Transcription Activator-Like Effector Nucleases (TALEN) have been developed to enable targeted and programmable modification of endogenous genomic sequences. TALEN and ZFN technologies use a strategy of tethering endonuclease catalytic domains to modular DNA binding proteins for inducing targeted DNA double-stranded breaks (DSB) at specific genomic loci. However, the need to design new complex nucleases for each target site limits the efficiency of these methods, particularly in multiplexed gene targeting applications. Unlike TALEN and ZFN, a recently discovered genome editing technology called the RNA-guided CRISPR-Cas nuclease system represents a simpler and more versatile approach to engineer the eukaryotic genome.

[0003] RNA-guided CRISPR-Cas nuclease system utilizes Clustered, Regularly

Interspaced, Short Palindromic Repeats (CRISPR) and a Cas (CRISPR-associated) endonuclease, first described in Archaea and bacteria as an RNA-mediated adaptive immune defense mechanism for the degradation of foreign invading viruses and genetic material. Three types of CRISPR systems, namely types I, II, and III, have been identified across a wide range of bacterial and archeal hosts. Each system comprises a cluster of CRISPR-associated (Cas) genes, non-coding RNAs including a distinctive array of repetitive elements (direct repeats). These repeats are interspaced by short variable sequences derived from exogenous DNA targets known as spacers (also referred to herein as target RNA sequences), and together they constitute the CRISPR RNA (crRNA) array. Within the DNA target, the protospacer (or DNA targeted by the Cas nuclease) is associated with a Protospacer Adjacent Motif (PAM), which can vary depending on the specific CRISPR system.

[0004] Type II CRISPR is one of the best characterized systems, and includes the endonuclease, Cas9, the crRNA array that encodes the guide RNAs and a required auxiliary transactivating crRNA (tracrRNA) that facilitates the processing of the crRNA array into discrete . units and facilitates binding with Cas9. The Cas9 nuclease has an RNA binding domain, an alpha helix recognition lobe (REC), a nuclease lobe that includes the RuvC endonuclease and HNH nuclease-associated protein for DNA cleavage, and a PAM interacting site. crRNA forms a complex with the Cas9 nuclease by binding to the bridge helix within the REC lobe, and forms multiple salt bridges with the backbone of the crRNA. Once the crRNA binds to the Cas9, the conformation of the Cas9 nuclease changes and creates a channel that allows for DNA binding. The Cas9/crRNA complex scans the DNA for a PAM (5'-NGG) site. Recognition of a PAM site leads to unwinding of the DNA, and allows the crRNA to check for complementary DNA in die sequence adjacent to the PAM site. When Cas9 binds to a PAM site adjacent to a DNA sequence that is complementary to the spacer sequence of the crRNA, the bridge helix within the REC lobe creates an RNA-DNA heteroduplex with the complimentary target DNA. The PAM site recognition is involved in activating the nucleolytic HNH and RuvC domains which create a double-stranded break in the target DNA, leading to DNA degradation. If the crRNA is not complementary, then Cas9 releases the DNA and searches for another PAM site.

[000S] Recently, it has been demonstrated that the type II CRISPR system from

Streptococcus pyogenes can be engineered to induce Cas9-mediated double-stranded breaks (DSBs) in a sequence-specific manner in vitro by providing a synthetic guide RNA (gRNA; also known as single guide RNA or sgRNA) composed of crRNA fused to tracrRNA. Moreover, the system has been successfully adapted to function in human cells with the use of human codon- optimized Cas9 and customizable 20-nucleotide (nt) target RNA sequences within the gRNAs. Once the gRNA identifies a PAM sequence-NOG, followed by the 20-base pair (bp) target sequence, Cas9 nuclease then cleaves the target sequence several nucleotides upstream of the PAM, creating a DSB. The resulting DSB will either generate nonspecific mutations knocking out a gene through the error-prone NHBJ (non-homologous end joining) pathway, or produce specific modifications dictated by the addition of an exogenous DNA repair template through the HDR (homology-directed repair) pathway. This system provides an enhanced method of genome engineering through the creation of desired DSBs targeted by RNA sequences that are inexpensively and readily designed and synthesized for delivery, holding great promise for multiplexed genome editing.

[0006] However, the current genome-editing techniques, including CRISPR-Cas9 system, are currently limited to use in vitro, for studying cell culture models of disease and/or creating transgenic animal models by editing embryonic stem cells. The most commonly proposed method of gene therapy in multi-cellular mammalian systems using CRISPR-Cas9 system is through viral delivery. Despite FDA approval of several adeno-associated viral and lenti-viral human clinical trials for gene therapy, mainstream physicians and pharmaceutical industries are reluctant to use them due to safety and ethical issues associated with viral-based gene therapy.

[0007] Thus, it would be desirable to develop alternative means for the delivery of genome editing technologies useful in diagnostic and therapeutic methods without the use of viral vectors.

Summary of the Invention

[0008] Genetically modified exosomes have now been developed which express or incorporate a gene-editing system and which may be effectively used to deliver gene-editing systems in vitro and vivo.

[0009] Thus, in one aspect of the invention, a genetically modified exosome is provided which is modified to express or incorporate a nuclease genome editing system.

[0010] In another aspect, a composition comprising a genetically modified exosome which is modified to express or incorporate a nuclease genome editing system is provided.

[0011] In another aspect, a method of treating a genetic disease in a mammal is provided comprising administering to the mammal a composition comprising a genetically modified exosome which is modified to express or incorporate a nuclease genome editing system, wherein the nuclease genome editing system is adapted to edit the genome of the mammal at a site causative of the genetic disease to provide treatment of the disease.

[0012] In a further aspect of the invention, a method of correcting a genetic mutation in a mammal is provided comprising administering to the mammal a composition comprising exosomes that are genetically modified to incorporate a nuclease genome editing system adapted to correct the genetic mutation.

[0013] These and other aspects of the invention will be described by reference to the following figures.

Brief Description of the Figures

[0014] Figure 1. Untargeted exosomes effectively carry CR1SPR-Cas9 designed to knock-down PGC-Ια expression. Figure 1 graphically illustrates that exosomes containing CRISPR-Cas9 Pgcla is taken up by mouse primary myotubes and results in disruption of PGC- la expression.

[0015] Figure 2. Untargeted exosomes deliver CRISPR-Cas9 ND4 to mitochondria and repair the m.ll778G>A mutation. Figure 2 graphically illustrates that exosomes packaged with CRISPR-Cas9 ND4 plasmids was effective to correct the ND4 m.H778G>A mutation in primary fibroblasts isolated from LHON patients (A/B).

[0016] Figure 3. Muscle-targeted exosomes deliver CRISPR-Cas9 to skeletal muscle and knock-down PGC-Ια function in vivo. Figure 3 graphically illustrates that muscle-targeted exosomes containing CRISPR-Cas9 PGCla results in PGCla gene editing (disruption) from skeletal muscle of mice as shown by gene expression analyses in (A) muscle (quadriceps femoris), (B) heart, (C) liver, and (D) brain.

[0017] Figure 4. Muscle-targeted exosomes carrying CRISPR-Cas9 designed to knock-down PGC-Ια reduce enzyme capacity selectively in skeletal muscle and lower endurance capacity. Figure 4 graphically illustrates that muscle-targeted exosomes containing CRISPR-Cas9 PGCla results in reduction of mitochondrial complex IV activity in skeletal muscle (A) and impedes mice endurance exercise capacity (B).

Detailed Description of the Invention

[0018] A genetically modified exosome is provided which is modified to express or incorporate a nuclease genome editing system. Such modified exosomes are useful to treat genetic disease.

[0019] The term "exosome" refers to cell-derived vesicles having a diameter of between about 20 and 140 nm, for example, a diameter of about 40-120 nm, including exosomes with a mean diameter of about 40 nm, SO nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or 110 nm. Exosomes may be isolated from any suitable biological sample from a mammal, including but not limited to, whole blood, serum, plasma, urine, saliva, breast milk, cerebrospinal fluid, amniotic fluid, ascitic fluid, bone marrow and cultured mammalian cells (e.g. immature dendritic cells (wild-type or immortalized), induced and non-induced pluripotent stem cells, fibroblasts, platelets, immune cells, reticulocytes, tumor cells, mesenchymal stem cells, satellite cells, hematopoietic stem cells, pancreatic stem cells, white and beige pre-adipocytes and the like). As one of skill in the art will appreciate, cultured cell samples will be in the cell-appropriate culture media (using exosome-free serum). Exosomes include specific surface markers that distinguish them from other vesicles, including surface markers such as tetraspanins, e.g. CD9, CD37, CD44, CD53, CD63, CD81, CD82 and CD151; targeting or adhesion markers such as integrins, ICAM-1, EpCAM and CD31; membrane fusion markers such as annexins, TSG101, ALIX; and other exosome transmembrane proteins such as Rab5b, HLA-G, HSP70, LAMP2 (lysosome- associated membrane protein) and LIMP (lysosomal integral membrane protein). Exosomes may also be obtained from a non- mammalian biological sample, including cultured non-mammalian cells. As the molecular machinery involved in exosome biogenesis is believed to be evolutionarily conserved, exosomes from non-mammalian sources include surface markers which are isoforms of mammalian surface markers, such as isoforms of CD9 and CD63, which distinguish them from other cellular vesicles. As used herein, the term "mammal" is meant to encompass, without limitation, humans, domestic animals such as dogs, cats, horses, cattle, swine, sheep, goats and the like, as well as non-domesticated animals such as, but not limited to, mice, rats and rabbits. The term "non-mammal" is meant to encompass, for example, exosomes from microorganisms such as bacteria, flies, worms, plants, fruit/vegetables (e.g. corn, pomegranate) and yeast.

[0020] Exosomes may be obtained from the appropriate biological sample using a combination of isolation techniques, for example, centrifugation, filtration and ultracentrifugation methodologies. In one embodiment, the isolation protocol includes the steps of: i) exposing the biological sample to a first centrifugation to remove cellular debris greater than about 7-10 microns in size from the sample and obtaining the supernatant following, centrifugation; ii) subjecting the supernatant from step i) to centrifugation to remove microvesicles therefrom; iii) micrpfiltering the supernatant from step ii) and collecting the microfiltered supernatant; iv) subjecting the microfiltered supernatant from step iii) to at least one round of ultracentrifugation to obtain an exosome pellet; and v) re-suspending the exosome pellet from step iv) in a physiological solution and conducting a second ultracentrifugation in a density gradient and removing the exosome pellet fraction therefrom.

[0021] Thus, the process of isolating exosomes from a biological sample may include a first step of removing undesired large cellular debris from the sample, i.e. cells, cell components, apoptotic bodies and the like greater than about 7-10 microns in size. This step is generally conducted by centrifugation, for example, at 1000-4000x g for 10 to 60 minutes at 4 °C, preferably at 1500-2500x g, e.g. 2000x g, for a selected period of time such as 10-30 minutes, 12-28 minutes, 14-24 minutes, 15-20 minutes or 16, 17, 18 or 19 minutes. As one of skill in the art will appreciate, a suitable commercially available laboratory centrifuge, e.g. Thermo- Scientific™ or Cole-Parmer™, is employed to conduct this isolation step. To enhance exosome isolation, the resulting supernatant is subjected to an optional centrifugation step in which the above centrifugation step is repeated, i.e. centrifugation at 1000-4000x g for 10 to 60 minutes at 4 °C, preferably at 1500-2500x g, e.g. 2000x g, for the selected period of time, to further remove cellular debris and apoptotic bodies, such as debris that is at least about 7-10 microns in size.

[0022] Following removal of cell debris, the supernatant resulting from the first centrifugation step(s) is separated from the debris-containing pellet (by decanting or pipetting it off) and may then be subjected to an optional additional (second) centrifugation step, including spinning at 12,000-15,000x g for 30-90 minutes at 4 °C to remove intermediate-sized debris, e.g. debris that is greater than 6 microns size. In one embodiment, this centrifugation step is conducted at 14,000x g for 1 hour at 4 °C. The resulting supernatant is again separated from the debris-containing pellet.

[0023] The resulting supernatant is collected and may be subjected to a third centrifugation step, including spinning at between 40,000-60,000x g for 30-90 minutes at 4 °C to further remove impurities such as medium to small-sized micro vesicles greater than 0.3 microns in size e.g. in the range of about 0.3-6 microns. In one embodiment, the centrifugation step is conducted at 50,000x g for 1 hour. The resulting supernatant is separated from the pellet for further processing.

[0024] The supernatant may then be filtered to remove debris, such as bacteria and larger microvesicles, having a size of about 0.22 microns or greater, e.g. using microfiltration. The filtration may be conducted by one or more passes through filters of the same size, for example, a 0.22 micron filter. Alternatively, filtration using 2 or more filters may be conducted, using filters of the same or of decreasing sizes, e.g. one or more passes through a 40-50 micron filter, one or more passes through a 20-30 micron filter, one or more passes through a 10-20 micron filter, one or more passes through a 0.22-10 micron filter, etc. Suitable filters for use in this step include the use of 0.45 and 0.22 micron filters.

[0025] The microfiltered supernatant (filtrate) may then be combined with a suitable physiological solution, preferably sterile, for example, an aqueous solution, a saline solution or a carbohydrate-containing solution in a 1:1 ratio, e.g. 10 mL of supernatant to 10 mL of physiological solution, to prevent clumping of exosomes during subsequent purification steps, such as ultracentrifugation, and to maintain the integrity of the exosomes. The exosomal solution is then subjected to ultracentrifugation to pellet exosomes and any remaining contaminating microvesicles (between 100-220 nm). This ultracentrifugation step is conducted at 110,000-170,000x g for 1-3 hours at 4 °C, for example, 170,000x g for 3 hours. This ultracentrifugation step may optionally be repeated, e.g. 2 or more times, in order to enhance results. Any commercially available ultracentrifuge, e.g. Thermo-Scientific™ or Beckman™, may be employed to conduct this step. The exosome-containing pellet is removed from the supernatant using established techniques and re-suspended in a suitable physiological solution,

[0026] Following ultracentrifugation, the re-suspended exosome-containing pellet may be subjected to density gradient separation to separate contaminating microvesicles from exosomes based on their density. Various density gradients may be used, including, for example, a sucrose gradient, a colloidal silica density gradient, an iodixanol gradient, or any other density gradient sufficient to separate exosomes from contaminating microvesicles (e.g. a density gradient that functions similar to the 1.100-1.200 g/ml sucrose fraction of a sucrose gradient). Thus, examples of density gradients include the use of a 0.25-2.5 M continuous sucrose density gradient separation, e.g. sucrose cushion centrifugation comprising 20-50% sucrose, and a colloidal silica density gradient, e.g. Percoll™ gradient separation (colloidal silica particles of 15-30 nm diameter, e.g. 30%/70% w/w in water (free of RNase and DNase), which have been coated with polyvinylpyrrolidone (PVP)). The resuspended exosome solution is added to the selected gradient and subjected to ultracentrifugation at a speed between 110,000- 170,000x g for 1-3 hours. The resulting exosome pellet is removed and re-suspended in physiological solution.

[0027] Depending on the density gradient used, the re-suspended exosome pellet resulting from the density gradient separation may be ready for use. For example, if the density gradient used is a sucrose gradient, the exosome pellet is removed from the appropriate sucrose gradient fraction, and is ready for use, or may preferably be subjected to an ultracentrifugation wash step at a speed of 110,000-170,000x g for 1-3 hours at 4 °C. If the density gradient used is, for example, a colloidal silica density gradient, then the resuspended exosome pellet may be subjected to additional wash steps, e.g. subjected to one to three ultracentrifugation steps at a speed of 110,000-170,000x g for 1-3 hours each at 4 °C, to yield an essentially pure exosome- containing pellet. As one of skill in the art will appreciate, the exosome pellet from any of the centrifugation or ultracentrifugation steps may be washed between centrifugation steps using an appropriate physiological solution, e.g. saline. The final pellet is removed from the supernatant and may be re-suspended in a physiologically acceptable solution for use. Alternatively, the exosome pellet may be stored for later use, for example, in cold storage at 4°C, in frozen form or in lyophilized form, prepared using well-established protocols. The exosome pellet may be stored in any physiological acceptable carrier, optionally including cryogenic stability and/or vitrification agents (e.g. DMSO, xylose, sucrose, mannitol, glycerol, trehalose, polyhydroxylated alcohols (e.g. methoxylated glycerol, propylene glycol), 2,2,2-trichloroethanol, M22 and the like).

[0028] In another embodiment, a method of isolating exosomes from a biological sample is provided comprising the steps of: i) optionally exposing the biological sample to a method of pre-enrichment to remove cellular and other debris; and ii) subjecting the sample to immunoaffinity capture with an antibody cocktail comprising at least three different antibodies to different exosome surface proteins. The exosomes bind to the antibodies which bind or are bound to a solid support to yield an exosome-solid support complex from which the isolated exosomes may be collected.

[0029] The biological sample may be pre-enriched to remove cellular and other debris therefrom. The degree of pre-enrichment conducted will vary with the nature of the biological sample used, as well as the purity and yield of the desired exosome product, and thus, may be more or less extensive accordingly. Thus, as will be appreciated by one of skill in the art, the biological sample may be subjected to pre-enrichment using one or more of: centrifugation, including sequential centrifugations at various speeds, microfiltration, ultrafiltration, ultracentrifugation with or without density gradients, polymer-based isolations, and the like.

[0030] In one embodiment, pre-enrichment comprises exposing the biological sample to a first centrifugation to remove cellular debris, i.e. cells, cell components, apoptotic bodies and the like greater than about 7-10 microns in size, from the sample, followed by microfiltration of the resulting supernatant. Removal of large cellular debris from the sample may be conducted by centrifugation, for example, at 1000-4000x g for 10 to 60 minutes at 4 °C, preferably at 1500- 2500x g, e.g. 2000x g, for a selected period of time such as 10-30 minutes. To enhance enrichment, the resulting supernatant may be subjected to an additional centrifugation step to further remove cellular debris and apoptotic bodies, such as debris that is at least about 7-10 microns in size, by repeating this first step of the process, i.e. centrifugation at 1000-4000x g for 10 to 60 minutes at 4 °C, preferably at 1500-2500x g, e.g. 2000x g, for the selected period of time. To remove intermediate-sized debris, e.g. debris that is greater than 6 microns size, the exosome-containing supernatant may be subjected to further centrifugation steps, including spinning at 12,000-15,000x g for 30-90 minutes at 4 °C. In one embodiment, this centrifugation step is conducted at 14,000x g for 1 hour at 4 °C. To remove smaller impurities such as medium to small-sized microvesicles greater than 0.3 microns in size e.g. in the range of about 0.3-6 microns, the exosome-containing supernatant may be subjected to a centrifugation step, including spinning at between 40,000-60,000x g for 30-90 minutes at 4 °C, e.g. spinning at 50,000x g for 1 hour.

[0031] Microfiltration may also be used to pre-enrich an exosome-containing sample to remove debris, such as bacteria and larger microvesicles, having a size of about 0.22 microns or greater, as described herein.

[0032] Ultracentrifugation may also be used to further remove debris or contaminating microvesicles/bacteria from a sample and thereby enhance the enrichment of exosomes. In this case, the filtrate may be combined with a suitable physiological solution. Ultracentrifugation may be conducted at 110,000-170,000x g for 1-3 hours at 4 °C, for example, 170,000x g for 3 hours, and may be repeated, e.g. 2 or more times, in order to enhance results. The ultracentrifugation step may be performed with or without the use of a density gradient. As one of skill in the art will appreciate, the resulting exosome pellet may be washed between centrifugation steps using an appropriate physiological solution, e.g. saline. Any commercially available ultracentrifuge, e.g. Thermo-Scientific™ or Beckman™, may be employed to conduct this step. The exosome-containing pellet is removed from the supernatant using established techniques and re-suspended in a suitable physiological solution.

[0033] Alternatively, the filtration and/or ultracentrifugation steps as described above, and/or one or more centrifugation steps, may be replaced by an ultrafiltration step in which the use of forces like pressure or centrifugal forces, lead to a separation of exosomes (permeate) from debris and contaminating microvesicles/bacteria (retentate) through a semipermeable membrane (e.g. comprising polymer materials such as polysulfone, polypropylene, cellulose acetate and polylactic acid). Ultrafiltration may be conducted in stages, first to target large cellular debris from the sample, i.e. cells, cell components, apoptotic bodies and the like greater than about 6-10 microns in size, and then to target debris such as microvesicles, e.g. greater than 0.3 microns in size, followed by removal of debris greater than 0.22 microns in size, e.g. contaminants such as bacteria and microvesicles. Appropriate conditions and filters are utilized at each stage.

[0034] Prior to conducting immunoaffinity capture of exosomes, biological samples with a high protein concentration (such as serum) may be immuno-depleted to remove high abundance proteins that may interfere with exosome capture by antibodies. Thus, removal of albumin, immunoglobulins such as IgG, IgM and IgA, transferrin, fibrinogen, apolipoprotein A-I and A-II, haptoglobin, al-antitrypsin, a2-macroglobulin and the like. Immunodepletion of such proteins may be readily accomplished using methods known to those of skill in the art. Kits for this purpose are also commercially available.

[0035] To isolate exosomes from the biological sample, either pre-enriched or not, immunoaffinity capture utilizing an antibody cocktail of three or more antibodies is used. The term "immunoaffinity capture" is used herein to refer to the use of antibodies to "capture" or isolate exosomes from a sample. Antibodies that bind specific exosome membrane marker proteins function as ligands to bind exosome membrane proteins, thereby providing a means to capture exosomes (either directly or indirectly) to permit their isolation from the sample. Examples of immunoaffinity capture techniques include, but are not limited to, immunoprecipitation, column affinity chromatography, magnetic-activated cell sorting, fluorescence-activated cell sorting, adhesion-based sorting and microfluidic-based sorting. The antibodies in the antibody cocktail may be utilized together, in a single solution, or may be utilized in two or more solutions that are administered simultaneously or consecutively.

[0036] Antibodies having specificity for any exosomal marker may be used. Examples of exosomal markers, which are not to be construed as limiting, include the following: CD9 molecule (CD9), programmed cell death 6 interacting protein/Alix (PDCD6IP), heat shock protein family A (Hsp70) member 8 (HSPA8), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin, beta (ACTB), annexin A2 (ANXA2), CD63 molecule (CD63), syndecan binding protein (SDCBP), enolase 1, (alpha) (ENOl), heat shock protein 90kDa alpha family class A member 1 (HSP90AA1), tumor susceptibility 101 (TSG101), pyruvate kinase, muscle (PKM), lactate dehydrogenase A (LDHA), eukaryotic translation elongation factor 1 alpha 1 (EBF1A1), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta (YWHAZ), phosphoglycerate kinase 1 (PGK1), eukaryotic translation elongation factor 2 (EEF2), aldolase, fructose-bisphosphate A (ALDOA), heat shock protein 90kDa alpha family class B member 1 (HSP90AB1), annexin A5 (ANXA5), fatty acid synthase (FASN), tyrosine 3- monooxygenase/tryptophan 5-monooxygenase activation protein, epsilon (YWHAE), clathrin, heavy chain (He) (CLTC), CD81 molecule (CD81), albumin (ALB), valosin containing protein (VCP), triosephosphate isomerase 1 (TPI1), peptidylprolyl isomerase A (cyclophilin A) (PPIA), moesin (MSN), cofilin 1 (CFL1), peroxiredoxin 1 (PRDX1), profiHn 1 (PFN1), RAP1B, member of RAS oncogene family (RAP IB), integrin subunit beta 1 (ITGB1), heat shock protein family A (Hsp70) member 5 (HSPAS), solute carrier family 3 (amino acid transporter heavy chain), member 2 (SLC3A2), histone cluster 1, H4a (HIST1H4A), guanine nucleotide binding protein (G protein), beta polypeptide 2 (GNB2), ATPase, Na+/K+ transporting, alpha 1 polypeptide (ATP1A1), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, theta (YWHAQ), fiotillin 1 (FLOTl), filamin A, alpha (FLNA), chloride intracellular channel 1 (CLIC1), chaperonin containing TCP1, subunit 2 (CCT2), cell division cycle 42 (CDC42), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, gamma (YWHAG), alpha-2-macroglobulin (A2M), tubulin alpha lb (TUBA1B), ras-related C3 botulinum toxin substrate 1 (rho family, small OTP binding protein Racl) (RAC1), lectin, galactoside-binding, soluble, 3 binding protein (LGALS3BP), heat shock protein family A (Hsp70) member 1A (HSPA1 A), guanine nucleotide binding protein (G protein), alpha inhibiting activity polypeptide 2 (GNAI2), annexin Al (ANXA1), ras homolog family member A (RHOA), milk fat globule- EGF factor 8 protein (MFGE8), peroxiredoxin 2 (PRDX2), GDP dissociation inhibitor 2 (GDI2), EH domain containing 4 (EHD4), actinin, alpha 4 (ACTN4), tyrosine 3- monooxygenase/tryptophan 5-monooxygenase activation protein, beta (YWHAB), RAB7A, member RAS oncogene family (RAB7A), lactate dehydrogenase B (LDHB), GNAS complex locus (GNAS), RAB5C, member RAS oncogene family (RAB5C), ADP ribosylation factor 1 (ARF1), annexin A6 (ANXA6), annexin Al 1 (ANXA11), actin gamma 1 (ACTG1), karyopherin (importin) beta 1 (KPNB1), ezrin (EZR), annexin A4 (ANXA4), ATP citrate lyase (ACLY), tubulin alpha lc (TUBAIC), transferrin receptor (TFRC), RAB14, member RAS oncogene family (RAB14), histone cluster 2, H4a (HIST2H4A), guanine nucleotide binding protein (G protein), beta polypeptide 1 (GNB1), thrombospondin 1 (THBS1), RAN, member RAS oncogene family (RAN), RABSA, member RAS oncogene family (RABSA), prostaglandin F2 receptor inhibitor (PTGFRN), chaperonin containing TCP1, subunit 5 (epsilon) (CCT5), chaperonin containing TCP1, subunit 3 (CCT3), adenosylhomocysteinase (AHCY), ubiquitin- like modifier activating enzyme 1 (UBA1), RABSB, member RAS oncogene family (RABSB), RAB1A, member RAS oncogene family (RABIA), lysosomal-associated membrane protein 2 (LAMP2), integrin subunit alpha 6 (ITGA6), histone cluster 1, H4b (HIST1H4B), basigin (Ok blood group) (BSG), tyrosine 3-monooxygenase/tryptophan S-monooxygenase activation protein, eta (YWHAH), tubulin alpha la (TUBAIA), transketolase (TKT), t-complex 1 (TCP1), stomatin (STOM), solute carrier family 16 (monocarboxylate transporter), member 1 (SLC16A1), RAB8A, member RAS oncogene family (RAB8A), myosin, heavy chain 9, non- muscle (MYH9) and major vault protein (MVP). Antibodies to exosome protein markers may be obtained using well-established techniques in the art. Antibodies to certain exosome markers may also be commercially available, for example, from LifeSpan Biosciences, Inc., Novus Biologicals, Thermoflscher Scientific, Abeam, among other providers.

[0037] In one embodiment, the antibody cocktail comprises 3 or more antibodies each having a specificity for a different exosome marker selected from the following proteins: Alix, Flotillin 1, CD9, CD63, CD81, TSG101 and LAMP2. For example, the antibody cocktail may comprise an antibody with specificity to each of Alix, Flotillin 1, CD9 and CD63, or an antibody to each of Flotillin 1 , CD9, CD63, CD81 and TSG101, or an antibody to each of Flotillin 1, CD9, CD63, CD81, TSG101 and ALIX, or an antibody with specificity to each of ALIX, TSG101 and CD9, or an antibody with specificity to each of CD81, CD63 and CD9.

[0038] Having selected antibodies for use in the isolation method, the selected antibody cocktail may be either directly or indirectly immobilized on a solid support in a known manner. While die appropriate solid support for use will vary with the immunoaffinity capture method used, examples of solid supports that may be appropriate for use include, but are not limited, to the following: agarose/sepharose, latex, dextran, acrylamide, polyacrylamide, other polymeric supports, cellulose, silica, colored or magnetic beads, glass and the like. To facilitate or enhance immobilization of selected antibodies to the solid support, affinity ligands such as protein A, protein G, protein A/G and protein L may first be immobilized on the solid support using well- established techniques. The solid support may alternatively be modified to incorporate other affinity ligands for binding the selected antibodies. For example, other affinity ligands such as streptavidin-biotin based ligands, amine-reactive ligands (such as N-HydroxySuccinimide (NES) ester-based, aldehyde-based, azlactone-based and carbonyl diimidazole (CDI)-based ligands), sulfhydryl-reactive ligands (such as maleimide-based, iodoacetyl-based and pyridyl disulfide- based ligands), carbonyl-reactive ligands (such as hydrazide-based ligands), carboxyl-reactive ligands (such as carbodiimide (EDC)-based ligands) and secondary antibodies to the selected antibodies may be immobilized on the solid support to bind with a corresponding ligand on the selected antibodies. Further, to enhance the purity of exosomes eluted from the solid support, the selected antibodies may be crosslinked to the solid support, or an affinity ligand on the support, prior to incubation with an exosome-containing sample. Examples of cross-linking agents used for this purpose include, but are not limited to the following: Disuccinimidyl suberate (DSS), Dimethyl pimelimidate (DMP) and Bis(sulfosuccinimidyl)suberate (BS3).

[0039] The selected antibodies may be bound to the solid support and then combined with exosome-containing sample, or may be first combined with the exosome-containing sample and then exposed to a solid support adapted to bind the selected antibodies, e.g. with antibody- binding ligand.

[0040] The described exosome isolation protocols advantageously provide a means to obtain mammalian exosomes which are at least about 90% pure, and preferably at least about 95% or greater pure, i.e. referred to herein as "essentially free" from cellular debris, apoptotic bodies and microvesicles having a diameter less than 20 or greater than 140 nm, for example, free from particles having a diameter of less than 40 or greater than 140 nm (as measured, for example, by dynamic light scattering), and which are biologically intact, e.g. not clumped or in aggregate form, and not sheared, leaky or otherwise damaged. Exosomes isolated according to the methods described herein exhibit a high degree of stability, evidenced by the zeta potential of a mixture/solution of such exosomes, for example, a zeta potential of at least a magnitude of 30 mV, e.g. < -30 or > +30, and preferably, a magnitude of at least 40 mV, 50 mV, 60 mV, 70 mV, 80 mV, or greater. The term "zeta potential" refers to the electrokinetic potential of a colloidal dispersion, and the magnitude of the zeta potential indicates the degree of electrostatic repulsion between adjacent, similarly charged particles (exosomes) in a dispersion; For exosomes, a zeta potential of magnitude 30 mV or greater indicates moderate stability, i.e. the solution or dispersion will resist aggregation, while a zeta potential of magnitude 40-60 mV indicates good stability, and a magnitude of greater than 60 mV indicates excellent stability.

[0041] Moreover, high quantities of exosomes are achievable by these isolation methods, e.g. exosomes in an amount of about 1-2000 μg total protein (e.g. 100-2000 μg total protein) can be obtained from 1-4 mL of mammalian serum or plasma, or from 15-20 mL of cell culture spent media (from at least about 2 x 10⁶ cells). Thus, solutions comprising exosomes at a concentration of at least about S μg/μL, and preferably at least about 10-25 μg/μL, may readily be prepared due to the high exosome yields obtained by the present method. The term "about" as used herein with respect to any given value refers to a deviation from that value of up to 10%, either up to 10% greater, or up to 10% less.

[0042] Exosomes isolated in accordance with methods herein described, which beneficially retain integrity, and exhibit a high degree of purity (being "essentially free" from entities having a diameter less than 20 nm and greater man 140 nm), stability and biological activity both in vitro and in vivo, have not previously been achieved. Thus, the present exosomes are uniquely useful, for example, diagnostically and/or therapeutically, e.g. for the in vivo delivery of nucleic acid. In this regard, it is noted that the present exosomes readily permit loading of exogenous nucleic acid in an amount of at least about 1 ng nucleic acid (e.g. mRNA) per 10 ug of exosomal protein, or at least about 30 ug protein per 10 ug of exosomal protein. They have also been determined to be non-allergenic/non-immunogenic, and thus, safe for autologous, allogenic, and xenogenic use.

[0043] Isolated exosomes, obtained using the methods described herein or other methods, may be genetically modified to express or incorporate a nuclease genome editing system useful to edit the genome, including nuclear and/or mitochondrial nucleic acid. Genome editing as described herein may include gene insertions, deletions, modifications (e.g. nucleotide transitions, transversions, insertions or deletions of one or more nucleotides or duplications of any nucleotide sequence), gene activation and gene silencing. As will be appreciated by one of skill in the art, genome editing may be for the purpose of correcting an undesirable gene mutation, introducing a gene mutation (e.g. including gene mutations to yield a transgenic animal model), altering a gene sequence (e.g. to improve, enhance or inhibit gene function), inserting a gene sequence (e.g. to activate or inhibit gene expression), and the like. Examples of nuclease genome editing systems include, but are not limited to, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) nuclease system, e.g. including a targeting gRNA and a CRISPR-associated (Cas) gene, such as CRISPR-Cas9, Transcription Activator-Like Effector Nucleases (TALEN) and mito-TALEN, Zinc-Finger Nucleases (ZFN), and other therapeutic nucleic acids, e.g. small interfering RNA, micro RNA, anti-microRNA, antagonist, small hairpin RNA, and aptamers (RNA, DNA or peptide based (including affimers)).

[0044] In one embodiment, isolated exosomes are genetically modified to express or incorporate a CRISPR nuclease system, such as a CRISPR/Cas9 Type II genome editing system, including a Cas nuclease, and a guide RNA (gRNA), which comprises a fusion of trans- activating RNA (tracrRNA) and CRISPR RNA (crRNA). CRISPR RNA includes a targeting RNA sequence and a distinctive array of non-coding direct RNA repeats. The crRNA and tracrRNA are related to the selected Cas nuclease. As one of skill in the art will appreciate, the crRNA and tracrRNA (components of the gRNA) and the Cas nuclease are indicated to be "related" which means that the crRNA and tracrRNA are specific for and recognized by one or more particular Cas nucleases.

[0045] The targeting sequence of the guide RNA (gRNA) is a strand of RNA that is homologous to a region on a target gene, i.e. a gene to be edited or silenced. As discussed in detail herein, target genes may be genes associated with genetic disease, including hereditary disease such as autosomal dominant, autosomal recessive, X-linked disorders, and mitochondrial genetic mutations. The term, "mutation" is used herein to describe any inherited or sporadic change in the nucleotide sequence or arrangement of DNA that results in a dysfunctional or absent protein including, but not limited to, nucleotide substitutions (e.g. missense mutations, nonsense mutations, RNA processing mutations, splice-site mutations, regulatory mutations, nucleotide transitions and nucleotide transversions), insertions or deletions of one or 'more nucleotides, duplications of any nucleotide sequence, repeat expansion mutations (e.g. trinucleotide repeats, etc.) and frame-shift mutations. The targeting RNA may comprise about 10-30 nucleotides, e.g. about 1S-2S nucleotides, such as 20 nucleotides, and may comprise a GC content of about 40-80%. In one embodiment, gRNAs utilizing truncated RNA targeting sequences (e.g. 17 or 18 nucleotides in length rather than the more typical 20 nucleotide sequences) are employed to improve the specificity of gene targeting. As would be appreciated by one skilled in the art, the optimal length of the RNA targeting sequences will vary dependent on several factors, such as GC content.

[0046] The CRISPR system may be utilized to disrupt expression of a gene by insertion or deletion of nucleotides to disrupt the Open Reading Frame (OKF) of a target gene, or to introduce a premature stop codon therein. Non-Homologous End Joining (NHEJ) DNA repair may be used in this instance.

[0047] The CRISPR system may also be used to edit (e.g. to correct a gene mutation) by utilizing homology directed repair, in which an editing region (also known as a repair template) is included in the CRISPR system. The editing region or repair template incorporates an edit (e.g. a healthy or wild-type DNA sequence to replace an undesirable DNA mutation in a target gene or any other edit as above) flanked by a region of homology (homologous arms) on either side thereof. The editing region or repair template may be a single-stranded DNA template sequence, double-stranded DNA template sequence or double-stranded DNA plasmid that is homologous to the wild-type template within the boundaries of the desired DNA edit. The size of the editing region or repair template is not particularly restricted, and may include a single nucleotide edit, or edits of up to 100 nucleotides or more. The homologous arms will generally increase in size with the size of the repair template, for example, for edits of less than about SO nucleotides, the homologous arms may be in the range of about 100-150 nucleotides in length, while larger repair templates may incorporate homologous arms of about 200-800 nucleotides, or more. Edits may also be introduced using CRISPR which facilitate expression of a target gene, e.g. edits which introduce a transcription factor that promotes gene expression.

[0048] The targeting sequence of the gRNA is selected such that it targets a site (e.g. a nucleotide or nucleic acid sequence) within the target gene that is proximal (e.g. within about 2-5 nucleotides or more) to a protospacer adjacent motif (PAM) located within the target gene. The PAM is recognized by the Cas nuclease and permits Cas nuclease binding. The gRNA additionally incorporates related crRNA and tracrRNA sequences, which interact with and function to direct the Cas nuclease to the target gene to catalyze cleavage of the target gene. As will be understood by one of skill in the art, while each of the crRNA, tracrRNA, and Cas nuclease sequences are related, these sequences may be native or mutated sequences, provided that any mutations thereof do not have an adverse impact on function. Nucleotide mismatches near the 5' end of the target DNA sequence that do not prevent Cas nuclease function and thus, double strand breaks (DSBs) can occur at sites other than the intended target DNA (also referred to as off-target DSBs) that may have deleterious/undesired consequences. To minimize the possibility that similar non-target sequences (e.g. containing a mismatch of only 1 or 2 nucleotides from the target DNA sequence, for example) will be cleaved by the Cas nuclease, it is preferred that the targeting RNA sequence specifically target the gene of interest, and that the target DNA sequence is unique and is not present elsewhere within the relevant genome. Selection of suitable gRNA sequences can be achieved using methods known in the art, such as using programs for this purpose (e.g. CRISPR-MIT (http://crispr.mit.edu/), CHOPCHOP (https://chopchop.rc.fas.harvard.edu/index.php), or E-CRISP (http://www.e-crisp.org/E- CRISP/index.html).

[0049] In order to enhance the efficacy of gene editing, multiple gRNAs that target the same gene at several different exons or loci may be employed. Similarly, multiple genes can be edited concurrently by combining gRNAs targeting two or more genes within the same application.

[0050] In the CRISPR/Cas9 Type II genome editing system, the Cas nuclease is a Cas9- based nuclease. Examples of a Cas9 nuclease include wild-type Cas9 (a double nickase) from Streptococcus pyogenes (SP), Staphylococcus aureus (SA), Neisseria meningitidis (NM), Streptococcus thermophilus (ST), and Treponema denticola (TD), as well as mutated recombinant Cas9, e.g. mutated to function as a single nickase such as Cas9 D10A and Cas9 H840A, which may be used with 2 or more gRNAs to achieve a genome edit with increasing targeting efficiency that prevents non-specific genomic editing. Single nickase Cas9 generates a single stranded break (SSB) at the DNA target site due to a mutation which renders one of the two nuclease domains of Cas9 catalytically inactive/dead. By multiplexing with a second gRNA that contains a targeting RNA sequence specific to a targeted DNA sequence on the opposite DNA strand to yield a second SSB and thereby, a DSB, provided that the second SSB is within suitable proximity (e.g. up to approximately 100 base pairs) to the initial SSB. Use of single nickase Cas9 in this manner can improve the specificity of the CRISPR/Cas9 system since in order for a DSB to occur, it is required that two separate DNA sequences of the target DNA sequences exist within a certain proximity (as opposed to the single sequence targeted by wild- type Cas9). Gene editing specificity may also be enhanced by using "enhanced specificity" Cas9 (eCas9), which is a modified form of wild-type SP Cas9 that has been altered to reduce target DNA strand binding efficiency and thus, increase the degree of target RNA and DNA homology that is required to result in a DSB. Other modified versions of SP Cas9 are also suitable for improving gene editing specificity, such as high-fidelity variant number 1 (SpCas9- HF1), for example, which eliminates or significantly reduces the number of DSBs at undesirable off-target loci. Specificity of gene editing may also be enhanced by utilizing catalytically dead Cas9 (dCas9 - in which both nuclease domains are inactivated, but which can target DNA sequences via two unique gRNA) that has been fused to a non-specific Fokl restriction endonuclease cleavage domain (termed FokI-dCas9). The FokI-dCas9 improves specificity by functioning as an obligate dimeric Cas9, which only induces a DSB when the two gRNA bind target DNA sequences (on opposing DNA strands) with a defined spacing and orientation (e.g. about 30bp apart) to cause the FokI-dCas9 monomers to bind and activate cleavage. Wild-type and single nickase Cas 9 may be used to edit genes, for example, autosomal recessive, X-linked recessive, autosomal dominant or mitochondrial DNA disorders, in order to correct the mutation.

[0051] The targeting RNA is an RNA strand complementary to a site on the target gene which is 3-4 nucleotides upstream of a PAM sequence recognized by the Cas nuclease. The targeting RNA does not itself include a PAM sequence. PAM sequences differ for various Cas nucleases. For example, for Streptococcus pyogenes (SP), the PAM sequence is NGG; for S. aureus, the PAM sequence is NNGRRT or NNGRR(N); for Neisseria meningitides, the PAM sequence is NNNNGATT; for Streptococcus thermophilus, the PAM sequence is NNAGAAW; for Treponema denticola (TD), the PAM sequence is NAAAAC. "N" represents any nucleotide, W = weak (A or T) and R = A or G. Given that a target DNA sequence must be adjacent to the appropriate PAM to allow for Cas binding and nuclease activity, non-SP Cas species (such as the ones described above, for example) can be utilized to increase the number of possible gRNA sequences that can be utilized to target a desired gene. An increased selection of gRNA sequences can also be achieved by employing SP Cas nucleases which have been modified to recognize alternative PAM sites (e.g. 5'-NGCG, 5'-NGAG, S'-NGAN or 5'-NGNG as PAM sites), contrary to wild-type SP Cas9 which recognizes 5'-NGG as a PAM.

[0052] As would be appreciated by one of skill in the art, the present method for delivering genome editing systems (e.g. the CRISPR/Cas genome editing system) is suitable not only for delivering genome editing systems that are currently available, but is also suitable for delivering modified or improved versions of current genome editing systems.

[0053] To reduce the probability of the Cas endonuclease reversing the gene edit by cutting a corrected DNA sequence which is newly inserted into the gene of interest, the PAM sequence that is present with the target DNA may be removed from the repair template or rendered non-functional (for example, using site-directed mutagenesis) or the repair template oligonucleotide may be synthesized without inclusion of the PAM site. If the PAM site is contained within a coding region of the newly inserted gene of interest, the alteration of the PAM site in the repair template may be a silent mutation (i.e. a mutation which renders the PAM site non-functional, but maintains functionality of the desired gene sequence).

[0054] While the CRISPR-Cas system is useful to permanently correct mutated or defective genes, CRISPR-Cas can also be used to temporarily activate or repress the activity of a target gene. For example, nuclease-deficient Cas (for example, incorporating both D10A and H840A to inactivate nuclease function) binds target DNA but does not cleave target DNA and thereby is useful to silence a gene. For use in transcriptional repression, nuclease-deficient Cas may be fused to a transcriptional repressor. The Cas functions to localize the repressor to a desired site of a target gene (e.g. around a transcriptional start site) on the target gene. Nuclease- deficient Cas 9, with or without fusion to a transcriptional repressor, may be used to treat an autosomal dominant-negative condition, to prevent or minimize expression of a dysfunctional mutated protein, which may interfere with the activity of the desired functional protein. Nuclease-deficient Cas can also be fused to a transcriptional activator to localize the transcriptional activator to a desired site of a target gene, e.g. transcriptional start site, and thereby, increase the activity of the target gene.

[0055] CRISPR-Cpfl gene editing systems may also be loaded into exosomes for use according to the present invention. CRISPR-Cpfl gene editing systems include the Cpfl single RNA-guided endonuclease in class 2 of the CRISPR Cas system, but possess several differences compared to CRISPR-Cas9. These primary differences include the recognition of a T rich PAM, the absence of a tracrRNA sequence and the production of a staggered DNA DSB leaving a 5'overhang, which is about 18-23 nucleotides away from the PAM. These unique characteristics of the CRISPR-Cpfl system may provide advantages over the CRISPR-Cas9 system in certain gene editing applications.

[0056] For introduction into exosomes, a nuclease genome editing system, such as a selected CRISPR nuclease system including gRNA, DNA repair template and a Cas nuclease, may be produced using known synthetic techniques and then incorporated into the same or different expression vectors under the control of an appropriate promoter. Suitable vectors for such expression are known in the art. Alternatively, expression vectors incorporating the selected nuclease genome editing system may be obtained commercially. Expression vectors incorporating the nuclease genome editing system may be introduced into exosomes using electroporation or transection using cationic lipid-based transfection reagents. Alternatively, the components of the nuclease editing system may be introduced directly into exosomes using similar introduction techniques. For example, the DNA repair template may be introduced into exosomes as ssDNA, the gRNA and Cas nuclease may be introduced into exosomes as oligonucleotides/mRNA, or the Cas nuclease may be introduced into exosomes as a protein (produced using recombinant techniques, or otherwise obtained). Thus, as would be recognized by one of skill in the art, the different components of the nuclease editing system may be introduced into exosomes in various forms and/or combinations of nucleic acid, protein and expression vector incorporating DNA. For example, exosomes can be loaded with gRNA in oligonucleotide form, an expression vector incorporating Cas nuclease DNA and the repair template in DNA form. [0057] The components of the nuclease genome editing system are introduced into exosomes, either directly or within expression vectors, using electroporation or other transfection methods such as transfection using cationic lipid-based transfection reagents. More particularly, electroporation applying voltages in the range of about 20-1000 V/cm may be used to introduce nucleic acid into exosomes. Transfection using cationic lipid-based transfection reagents such as, but not limited to, Lipofectamine™ CRISPRMAX™ Cas9 Transfection Reagent, Lipofectamine® MessengerMAX™ Transfection Reagent, Lipofectamine® RNAiMAX Transfection Reagent, Lipofectamine® 3000 Transfection Reagent, or Lipofectamine® LTX Reagent with PLUS™ Reagent, may also be used. The amount of transfection reagent used may vary with the reagent, the sample and the cargo to be introduced. For example, using Lipofectamine® MessengerMAX™ Transfection Reagent, an amount in the range of about 0.1S μL to 10 μL may be used to load 100 ng to 2500 ng nucleic acid or protein into exosomes. Other methods may also be used to load nucleic acid or protein into exosomes including, for example, the use of cell-penetrating peptides.

[0058] In another embodiment, one or more expression vectors encoding components of the selected nuclease genome editing system may be introduced directly into exosome-producing cells, e.g. autologous, allogenic, or xenogenic cells, such as immature dendritic cells (wild-type or immortalized), induced and non-induced pluripotent stem cells, fibroblasts, platelets, immune cells, reticulocytes, tumor cells, mesenchymal stem cells, satellite cells, hematopoietic stem cells, pancreatic stem cells, white and beige pre-adipocytes and the like, by electroporation or other transfection methods as described above. Following a sufficient period of time, e.g. 3-7 days to achieve stable expression of the nuclease genome editing system, exosomes incorporating the nuclease genome editing system are isolated from the exosome-producing cells as described herein.

[0059] The components of the nuclease genome editing system, for incorporation into exosomes according to the invention, may be functional native mammalian nucleic acids or proteins, including for example, nucleic acid or protein from human and non-human mammals, or may be functionally equivalent variants of native nucleic acids or protein. The term "functionally equivalent" refers to nucleic acid, e.g. mRNA, rRNA, tRNA, DNA, or cDNA, which retains the same or similar function to its native counterpart, including but not limited to the capacity to encode a functional protein. Thus, functional nucleic acid equivalents include all transcript variants, variants that encode protein isoforms, variants due to degeneracy of the genetic code, artificially modified variants, and the like. Thus, nucleic acid modifications may include one or more base substitutions or alterations, addition of 5' or 3' protecting groups, and the like, preferably maintaining significant sequence similarity, e.g. at least about 70%, and preferably, 80%, 90%, 95% or greater. The term "functionally equivalent" is used herein also to refer to a protein which exhibits the same or similar function to the native protein (e.g. retains at least about 30% of the activity of the native protein), and includes all isoforms, variants, recombinant produced forms, and naturally-occurring or artificially modified forms, i.e. including modifications that do not adversely affect activity and which may increase cell uptake, stability, activity and/or therapeutic efficacy. Protein modifications may include, but are not limited to, one or more amino acid substitutions (for example, with a similarly charged amino acid, e.g. substitution of one amino acid with another each having non-polar side chains such as valine, leucine, alanine, isoleucine, glycine, methionine, phenylalanine, tryptophan, proline; substitution of one amino acid with another each having basic side chains such as histidine, lysine, arginine; substitution of one amino acid with another each having acidic side chains such as aspartic acid and glutamic acid; and substitution of one amino acid with another each having polar side chains such as cysteine, serine, threonine, tyrosine, asparagine, glutamine), additions or deletions; modifications to amino acid side chains, addition of a protecting group at the N- or C- terminal ends of the protein, addition of a nerve targeting sequence or targeting fragments thereof, at the N-terminal end of the protein and the like. Suitable modifications will generally maintain at least about 70% sequence similarity with the active site and other conserved domains of the native protein, and preferably at least about 80%, 90%, 95% or greater sequence similarity.

[0060] Exosomes may be further genetically engineered to target particular tissues/cells to facilitate delivery of the nuclease genome editing system. In this regard, exosomes may be engineered to incorporate a target-specific fusion product comprising a cell or tissue targeting sequence linked to an exosomal membrane marker. The exosomal membrane marker of the fusion product will localize the fusion product within the membrane of the exosome to enable the targeting sequence to direct the exosome to the intended target. Examples of exosome membrane markers include, but are not limited to: tetraspanins such as CD9, CD37, CDS3, CD63, CD81, CD82 and CD151; targeting or adhesion markers such as integrals, ICAM-1 and CDD31; membrane fusion markers such as annexins, TSG101, ALIX; and other exosome transmembrane proteins such as LAMP (lysosome-associated membrane protein) and LIMP (lysosomal integral membrane protein). All or part (a fragment) of an exosome membrane marker may be utilized in the fusion product provided that the fragment includes a sufficient portion of the membrane marker to enable it to localize within the exosomal membrane, i.e. the fragment comprises at least one intact transmembrane domain to permit localization of the membrane marker within the exosomal membrane.

[0061] Suitable cell or tissue targeting peptides will generally comprise a peptide sequence derived from a cell surface marker of a target cell or tissue. The cell or tissue targeting peptide may comprise all or a portion of a target cell surface marker that will function to direct the exosome to the target cell or tissue. Examples of targeting peptides for some tissues include, but are not limited to, the following: target peptides for cerebellum include sequences from cerebellin, Muncl3, LANO and CACNA1A; target peptides for cerebrum/pyrimidal cells include sequences from GLUT1, SLC1A3, cortexin, SCAMPS and Synaptotagmin-1; target peptides for hippocampus include sequences from muscarinic acetylcholine receptors such as Ml, M2 and M4, and SNAP25; target peptides for brain generally including YTIWMPENPRPGTPCDIFTNSROKRASNG (SEQ ID NO: 1); target peptides for astrocytes/glia include sequences from GFAP and SLC1A3; target peptides for myelin include sequences from myelin basic protein and PMP-22; target peptides for nerves include sequences from MAG, KIF1A, Synthaxinl, SNAP2S and synaptobrevin; target peptides for dermis include sequences from CDl lc+/BDCA-l+; target peptides for skin include sequences from p63, and AE1/AE3; target peptides for heart include sequences from cardiac troponin C; target peptides for skeletal muscle include sequences from muscle-binding peptides such as SERCA2, acetylcholine receptor epsilon, SCN4A, muscle specific creatine kinase (CK-MM), including the peptide sequence, TARGEHKEEELI (SEQ ID NO: 2); and target peptides for lysosomes include LAMP, LIMP and fragments thereof, e.g. the C-terminal sequence of LAMP or LIMP. [0062] To further facilitate take up of the target-specific fusion product, the fusion product may be additionally linked to a lysosomal targeting sequence, e.g. at least a partial sequence of a lysosomal membrane protein such as LAMP1 or LAMP2, preferably an N- terminal sequence thereof comprising at least about 10-50 amino acid residues.

[0063] Exosomes incorporating a target-specific fusion product may be produced using recombinant technology. In this regard, an expression vector encoding the target-specific fusion product, or the target-specific fusion product itself, is introduced by electroporation or other transfection methods into exosome-producing cells isolated from an appropriate biological sample, e.g. blood or other appropriate sample. Preferred exosome-producing cells include those which express a low level of immuno-stimulatory molecules and which can readily be modified to express the fusion product, e.g. immature dendritic cells and primary fibroblasts (autologous, allogenic, xenogenic and cross-Kingdom (e.g. from non-mammals such as plants)). Following a sufficient period of time (e.g. 2-10 days), exosomes generated by the exosome-producing cells, and including the fusion product, may be isolated as described. The desired nuclease genome editing system, may be introduced into isolated exosomes incorporating a targeting fusion product as previously described.

[0064] Exosomes may be further modified to incorporate or express other desired functional proteins and/or nucleic acids in addition to the nuclease genome editing system. Such additional proteins and/or nucleic acids may function as an adjunct therapy. For example, the concurrent or sequential use of nuclease gene editing systems may be utilized, a first system functions to replace a mutated gene with a healthy wild-type gene, in combination with a second system designed to activate the transcriptional activity of the healthy wild-type gene.

[0065] Engineered exosomes according to an aspect of the present invention may be formulated for therapeutic use by combination with a pharmaceutically acceptable carrier. The expressions "pharmaceutically acceptable" or "physiologically acceptable" mean acceptable for use in the pharmaceutical and veterinary arts, i.e. not being unacceptably toxic or otherwise unsuitable for physiological use. As one of skill in the art will appreciate, the selected carrier will vary with intended utility of the exosome formulation. In one embodiment, exosomes are formulated for administration by infusion or injection, e.g. subcutaneously, intraperitoneally, intramuscularly or intravenously, and thus, are formulated as a suspension in a medical-grade, physiologically acceptable carrier, such as an aqueous solution in sterile and pyrogen-free form, optionally, buffered or made isotonic. The carrier may be distilled water (DNase- and RNase- free), a sterile carbohydrate-containing solution (e.g. sucrose or dextrose) or a saline solution comprising sodium chloride and optionally buffered. Suitable saline solutions may include varying concentrations of sodium chloride, for example, normal saline (0.9%), half-normal saline (0.45%), quarter-normal saline (0.22%), and solutions comprising greater amounts of sodium chloride (e.g. 3%-7%, or greater). Saline solutions may optionally include additional components, e.g. carbohydrates such as dextrose and the like. Examples of saline solutions including additional components, include Ringer's solution, e.g. lactated or acetated Ringer's solution, phosphate buffered saline (PBS), TRIS (hydroxymethyl)aminomethane-buffered saline (TBS), Hank's balanced salt solution (HBSS), Earle's balanced solution (EBSS), standard saline citrate (SSC), HEPES-buffered saline (HBS) and Grey's balanced salt solution (GBSS).

[0066] In other embodiments, exosomes are formulated for administration by routes including, but not limited to, oral, intranasal, enteral, topical, sublingual, intra-arterial, intramedullary, intrauterine, intrathecal, inhalation, ocular, transdermal, vaginal or rectal routes, and will include appropriate carriers in each case. For oral administration, exosomes may be formulated in normal saline, complexed with food, in a capsule or in a liquid formulation with an emulsifying agent (honey, egg yolk, soy lecithin, and the like). Oral compositions may additionally include adjuvants including sugars, such as lactose, trehalose, glucose and sucrose; starches such as corn starch and potato starch; cellulose and derivatives thereof, including sodium carboxymethylcellulose, ethylcellulose and cellulose acetates; powdered tragancanth; malt; gelatin; talc; stearic acids; magnesium stearate; calcium sulfate; vegetable oils, such as peanut oils, cotton seed oil, sesame oil, olive oil and corn oil; polyols such as propylene glycol, glycerine, sorbital, glycerol, mannitol and polyethylene glycol; agar; alginic acids; water; isotonic saline and phosphate buffer solutions. Wetting agents, lubricants such as sodium lauryl sulfate, stabilizers, colouring agents and flavouring agents may also be present. Compositions for topical application may be prepared including appropriate carriers. Creams, lotions and ointments may be prepared for topical application using an appropriate base such as a triglyceride base. Such creams, lotions and ointments may also contain a surface active agent. Aerosol formulations may also be prepared in which suitable propellent adjuvants are used. Other adjuvants may also be added to the composition regardless of how it is to be administered, for example, anti-microbial agents, anti-oxidants and other preservatives may be added to the composition to prevent microbial growth and/or degradation over prolonged storage periods.

[0067] In accordance with another aspect of the invention, exosomes engineered to incorporate a selected nuclease genome editing system are useful in methods to treat genetic disease. The terms "treat", "treating" or "treatment" are used herein to refer to methods that favourably alter a genetic disease or disorder, including those that moderate, reverse, reduce the severity of, or protect against, the progression of autosomal dominant, autosomal recessive, X- linked recessive genetic diseases or mitochondrial disease.

[0068] Exosomes modified to incorporate a nuclease genome editing system are useful to treat nuclear or mitochondrial gene pathogenic mutations in order to correct or alter hereditary (including autosomal dominant, autosomal recessive and X-linked recessive disorders) and/or spontaneous mutations that result in disease. Examples of autosomal recessive, X-linked recessive or autosomal dominant disorders that may be treated in accordance with the invention include, but are not limited to; muscular dystrophy (MD) (e.g. Duchenne MD, limb-girdle MD, oculopharyngeal MD, fascio-scapulo-humeral MD, myotonic MD type 1 and 2, congenital MD, congenital myopathies, etc.), genetic cancers (e.g. BRCA1/BRCA2 associated cancers, ataxia- telangiectasia, etc.), peripheral neuropathies (e.g. Charcot-Marie-Tooth disease, hereditary Amyotrophic Lateral Sclerosis, spinal muscular atrophy, Spinal and bulbar muscular atrophy (SBMA), etc.), Spino-cerebellar Ataxias (e.g. aprataxin, senetaxin, Spinocerebellar ataxia type 1 (SCA1), SCA2, SCA3, Friedreich's Ataxia, etc.), Hereditary Spastic Paraparesis (e.g. Spastic Paraplegia 7 (SPG7), SPG11, SACS mutations, etc.), blood disorders (hemophilia, familial hypercholesterolemia, hereditary spherocytosis, sickle cell anemia, etc.), liver disease (Wilson disease, hemochromatosis, galactosemia, hereditary fructose intolerance, citrin deficiency, alpha- 1 -antitrypsin deficiency, arginosuccinate lyase deficiency, ornithine transcarbarnylase deficiency and other urea cycle disorders, etc.), polycystic kidney disease, neurofibromatosis type I, connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome, osteogenesis imperfect, etc.), genetic Parkinson disease (e.g. mutations in PTEN-induced putative kinase (PINK), PARKIN, etc.), Huntington disease, cystic fibrosis, lysosomal storage disease (e.g. Pompe disease, Fabry disease, Gaucher disease, metachromatic leukodystrophy, neural ceroid lipofuscinosis, Tay-Sachs disease, mucopolysaccharidosis, lysosomal acid lipase deficiency, etc.), amino acidopathies (e.g. phenylketonuria, Maple Syrup Urine disease (MSUD), etc.), organic acidurias (e.g. proprionic acidemia, methylmalonic acidemia, etc.), glycogen storage diseases (e.g. glycogen storage disease la (GSDla), GSDlb, GSD2, GSD3, GSD4, GSD5, etc.), peroxisomal disorders (e.g. adrenoleuokodystrophy, Zellweger syndrome, Perrault syndrome (HSD17B4), etc.), fatty acid oxidation detects (e.g. in carnitine acyltransferase I (CPT1), CPT2, trifunctional protein (TFP), Medium-chain acyl-CoA dehydrogenase (MCAD), Very long-chain acyl-CoA dehydrogenase (VLCAD), Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD), etc.), and creatine defects (e.g. in L-Arginine:glycine amidinotransferase (AGAT), Guanidlnoacetate methyltransferase (GAMT), CreaT).

[0069] Examples of mitochondrial disease, resulting from mitochondrial DNA or nuclear mutations, include, but are not limited to, Leber Hereditary Optic Neuropathy (LHON), Leigh Syndrome (LS, subacute sclerosing encephalopathy) due to mtDNA (i.e. m.8993T>C/G) or nDNA mutations (i.e. NDUFV1, etc.), Neuropathy, Ataxia, Retinitis Pigmentosa (NARP), MyoNeurogenic Gastrointestinal Encephalopathy (MNGIE), Myoclonic Epilepsy with Ragged Red Fibers (MERRF), Mitochondrial myopathy, Encephalomyopathy, Lactic Acidosis, Strokelike episodes (MELAS), Kearn-Sayre-Syndrome (KSS), infantile cardiomyopathy due to SC02 mutations (G1541A and C1634T), Pearson's syndrome, chronic progressive external ophthalmoplegia associated with mutations in the MT-TLl, POLG, SLC25A4, and CJOor/2 genes, disorders resulting from POLG1 mutations such as SANDO (Sensory Ataxic Neuropathy, Dysarthria, and Ophthalmoparesis) and Alper Syndrome (hepatopathy and encephalopathy due to POLG1. mutations), Combined Oxidative Phosphorylation Defects (COXPD), hereditary spastic paraparesis due to SPG7 mutations, peripheral neuropathy due to Mfh2 mutations, and other mtDNA disorders affecting any of the 37 genes encoded for by mtDNA. The mutations for each of the foregoing are well-known to those of skill in the art, and in many cases, each disease may result from one of multiple mutations. Reference may be made to the Human Polymerase Gamma Mutation Database at NIH for current mutations. Mutations for the aforementioned disorders can be found listed at: http://www.lovd.nV3.0/home for nuclear mutations, and at: http://www.mitomap.org/MITOMAP for both mtDNA and nDNA mutations that result in mitochondrial disease.

[0070] Thus, for use to treat such a disease, a therapeutically effective amount of exosomes, engineered to incorporate a nuclease genome editing system useful to treat the disease, is administered to a mammal in need of treatment. The term "therapeutically effective amount" is an amount of engineered exosomes required to treat the disease, while not exceeding an amount that may cause significant adverse effects. Exosome dosages that are therapeutically effective will vary on many factors including the nature of the condition to be treated, the targeted tissue and/or organelle, as well as the particular individual being treated. Appropriate exosome dosages for use include dosages sufficient to result in an increase in the amount or activity of a target protein product in the case of an autosomal recessive or X-linked recessive genetic disease, or an increase in the amount or activity of a target product (e.g. protein (such as ND4), tRNA (such as tRNAleu), or rRNA (such asl6S rRNA) in the case of mitochondrial mtDNA disorders (i.e. the target product is not expressed causing the disease state), for example, an increase in the target product to an amount which is at least about 5% of the amount expressed in a healthy individual (e.g. wild-type or normal expression), preferably an amount of target product which is at least about 10%, 20%, 30%, 40%, 50% or greater of wild-type expression, e.g. an increase of up to about 50-100% of wild-type expression. In the case of haplo- insufficiency autosomal dominant disorders, exosome dosages sufficient to result in an increase of target product of at least about 70% or greater of wild-type expression of the target product are appropriate. In the case of a dominant-negative genetic disease, exosome dosages for use include dosages sufficient to result in a decrease in the amount or activity of a mutated target product or other undesirable protein product (i.e. an undesirable mutated product/protein which interferes with the expression and/or activity of the healthy wild-type protein), for example, a decrease in expression of the mutated product of greater than about 5 %, 10%, 20%, 30%, 40%, 50% or greater, e.g. a decrease of between 50-100% of the mutated protein expression. Similarly, an exosome dosage appropriate to lower mutational heteroplasmy in mitochondrial disease would be a dosage sufficient to result in a decrease in mutated target product (tRNA, rRNA, protein coding subunit), for example, a decrease in expression of the mutated product of greater than about 20%, 30%, 40%, 50% or greater, e.g. a decrease of between 50-100%. Dosages in the range of about 20 ng to about 200 mg of total exosomal protein for the delivery of DNA or RNA species such as mRNA, tRNA, rRNA, miRNA, SRP RNA, snRNA, scRNA, snoRNA, gRNA, RNase P, RNase MRP, yRNA, TERC, SLRNA, lncRNA, piRNA, or other DNA or RNA oligonucleotides, or the delivery of protein or aptamers, are appropriate for use. In one embodiment, the exosome dosage may be a dosage in an amount in the range of about 1 - 1000 μg of total exosomal protein to result in an increase of 50-98% of a target protein/product. In an exemplary embodiment, a dosage of exosomes sufficient to deliver about 0.1 mg/kg to about 100 mg/kg of a protein, or 0.1 ng/kg to about 100 μg/kg of a nucleic acid (e.g. a DNA or RNA species), is administered to the mammal in the treatment of a disease. The term "about" is used herein to mean an amount that may differ somewhat from the given value, by an amount that would not be expected to significantly affect activity or outcome as appreciated by one of skill in the art, for example, a variance of from 1-10% from the given value.

[0071] Exosomes comprising a nuclease genome editing system, useful to treat genetic disorders (hereditary or spontaneous mutation-induced), may be used alone or in conjunction with (at different times or simultaneously, either in combination or separately) one or more additional therapies to facilitate treatment. Thus, the present exosomes may be used in conjunction with, for example, one or more of antibiotics, chaperones, gene therapy, enzyme replacement therapy, anti-oxidants (i.e., coenzyme Q10, alpha ltpoic acid, vitamin E, synthetic coenzyme Q10 analogues, resveratrol, N-acetylcysteine, etc.), anti-inflammatory agents, immune modulators, chemotherapy agents, monoclonal antibodies, creatine monohydrate, exercise/physio-therapy, insulin and other glycemic control medications, and/or pain medications.

[0072] The use of engineered exosomes in a therapy to treat a genetic disease advantageously results in an efficient, specific treatment not provided by current potential therapies. Additionally, the use of exosomes provides a non-immunogenic means of introducing a gene-editing system in vivo. This is important especially if repeated dosing is required to achieve sufficient genome editing.

[0073] Embodiments of the invention are described in the following examples which are not to be construed as limiting. Example 1 - Preparation of CRISPR-Cas9 nuclease system-containing exosomes

[0074] To determine whether or not the CRISPR-Cas9 nuclease system could be effectively packaged in exosomes and delivered, an in vitro experimental design was utilized in which functional consequences of genome editing could rapidly be analyzed.

[0075] Exosome isolation methodology- Immature dendritic cells from human and mice were grown to 65-70% confluency in alpha minimum essential medium supplemented with ribonucleosides, deoxyribonucleosides, 4 mM L-glutamine, 1 mM sodium pyruvate and 5 ng/ml murine GM-CSF, and 20% fetal bovine serum. For conditioned media collection, cells were washed twice with sterile PBS (pH 7.4, Life Technologies) and aforementioned media (with exosome depleted fetal bovine serum) was added. Conditioned media from human and mouse immature dendritic cell culture was collected after 48 hours of induction. The media (10 mL) was spun at 2,000x g for 15 min at 4°C to remove any cellular debris. This is followed by 2000x g spin for 60 min at 4°C to further remove any contaminating non-adherent cells. The supernatant was then spun at 14,000x g for 60 min at 4°C. The resulting supernatant was then filtered through a 40 um filter, followed by filtration through a 0.22 um syringe filter (twice). The resultant filtered supernatant was spun at 50,000x g for 60 min at 4°C. The supernatant was then carefully transferred into ultracentrifuge tubes and diluted with an equal amount of sterile PBS (pH 7.4, Life Technologies). This mixture was then subjected to ultracentrifugation at 150,000x g for 2 hours at 4°C using a fixed-angle rotor. The resulting pellet was re-suspended in PBS and re-centrifuged at 150,000x g for 2 hours at 4°C. The pellet was resuspended carefully with 25 mL of sterile PBS (pH 7.4, Life Technologies) and then added gently added on top of 4 mL of 30% Percoll gradient cushion (made with 0.22 μπι filter sterilized water) in an ultracentrifuge tube. This mixture was spun at 150,000x g for 90 minutes at 4°C. With a syringe, the exosomal fraction (pellet-containing) was isolated carefully, diluted in 50 mL of sterile PBS (pH 7.4, Life Technologies), followed by a final spin for 90 minutes at 150,000x g at 4°C to obtain purified exosomes. The resulting exosomes were resuspended in sterile PBS or sterile 0.9% saline for downstream use. Exosomal fraction purity was confirmed by sizing using a NanoSight LM10 instrument, and by immuno-gold labelling/Western blotting using the exosome membrane markers, CD9, CD63, TSO101 and ALIX. [0076] Electroporation or transfection using the cationic lipid-based transfection reagent, Lipofectamine® 3000 (Life Technologies), was used to introduce the CRISPR-Cas 9 gene editing system (containing the double nickase plasmid system from Santa Cruz Biotechnology® and Sigma-AIdrich® directed towards multiple exons of the Ppargcla or Nd4 gene) into unmodified exosomes isolated as described above in vitro. Multiple exon-based genome editing for a single gene was used to increase both the efficiency and specificity of gene editing without off target effects. After transfection/electroporation, exosomes were resuspended in 20 mL of sterile PBS (pH 7.4), followed by ultracentrifugation for 2 hours at 170,000χ g at 4°C. For in vitro exosome administration, Ppargcla or Nd4 double nickase CRISPR-Cas9 plasmid-loaded exosomes were re-suspended in 5% (wt/vol) glucose in 100 uL of sterile PBS (pH 7.4) at a concentration of 5 ug/uL of total exosomal protein.

Example 2 - Exosomal CRISPR-Cas9 nuclease system

[0077] The ability of exosomes containing CRISPR-Cas9 PGC-Ια plasmids to edit the PGC-Ια gene and thereby prevent PGC-lct expression was determined.

[0078] Primary mouse myoblasts isolated from C57B1/6 mice (n = 3 male mice, 2 months of age) were differentiated into myotubes. Differentiated primary mouse myotubes were treated with exosomes containing a CRISPR control plasmid vehicle or with exosomes containing CRISPR-Cas9 PGC-Ια plasmids (100 uL of S ug/uL total exosomal protein in PBS) for 72 hours at 37 °C in Dulbecco's Modified Eagle's Medium (DMEM) containing exosome- free 2% heat-inactivated horse serum. Cells were harvested after 72 hours, RNA was isolated, and qPCR was carried out to quantify PGC-Ια gene expression. The PGC-la qPCR amplification plot shows little to no PGC-la expression (Ct values > 35) in myotubes treated with exosomes containing CRISPR-Cas9 PGC-la plasmids vs. myotubes treated with exosomes containing CRISPR-control plasmid (Figure 1). This clearly shows that the CRISPR-Cas9 nuclease system can be successfully packaged in exosomes and effectively delivered to cells in vitro in a form that maintains genome-editing functionality. Example 3 - Exosomal CRISPR-Cas9 nuclease system overcomes LHON fm.ll778G>A)

[0079] It was then determined whether or not exosomes incorporating the CRISPR-Cas9 system could be functionally used for genetic therapy in patients with, for example, Leber's Hereditary Optic Neuropathy (LHON), a mitochondrial DNA (mtDNA). disease in which the mutated mtDNA-encoded ND4 subunit (NADH-ubiquinone oxidoreductase chain 4) results in mitochondrial complex I deficiency.

[0080] Primary dermal fibroblasts were isolated from patients with LHON (3 independent patients with m.ll778G>A ND4 mutation). Control dermal fibroblasts were obtained from age/sex-matched healthy control subjects. Fibroblasts were treated with exosomes containing CRISPR control plasmid vehicle vs. exosomes containing CRISPR-Cas9 ND4 plasmids (including the gRNA sequence to cut and remove mutant ND4 followed by insertion of healthy wild-type ND4 using the homology-directed repair mechanism). Treatment included administration of 100 uL of 5 ug/uL total exosomal protein in PBS to cells, and incubation for 72 hours in enriched alpha-MEM media supplemented with 10% exosome depleted fetal bovine serum. Cells were harvested at 72 hours post-treatment and mitochondrial complex I activity relative to citrate synthase activity was quantified. Treated LHON fibroblasts exhibited normalization of LHON cellular mitochondrial complex I activity relative to complex I activity in dermal fibroblasts from healthy subjects (Figure 2). It is notable that this is the first instance of the use of the CRISPR-Cas9 system for gene-editing in an organelle (mitochondria), as opposed to nuclear gene-editing.

Example 4 - Exosomal delivery of CRISPR-Cas9 nuclease system for gene-editing in vivo

[0081] CRISPR-Cas9 genomic editing technology has not previously been utilized in vivo. Thus, it was determined whether or not the CRISPR-Cas9 nuclease system could be delivered in vivo using exosomes to achieve functional gene editing.

[0082] Exosomes isolated as described above were bioengineered to include a targeting peptide for skeletal muscle (TARGEHKEEELI (SEQ ID NO: 2), a skeletal muscle targeting sequence from peptide-presenting muscle phage libraries). The muscle targeting sequence was fused to the N-terminus of mouse LAMP1 (an abundant exosomal surface protein). To produce exosomes that included this fusion product, dendritic cells were transfected with a mammalian expression vector expressing a [skeletal muscle targeting sequence-Lamp 1 -lysosomal targeting sequence (LTS)] fusion product using Lipofectamine 3000 reagent (Life Technologies). The [skeletal muscle targeting sequence-Lamp 1 -LTS] fusion plasmid was made using Gateway® technology and vectors (Life Technologies) with amplified mouse skeletal muscle cDNA that corresponds to the LAMP1 LTS (MAAPGARRPL LLLLLAGLAHGASALFEVKN) (SEQ ID NO: 3) + the first 10 amino acids of the mature LAMP I protein (for human: AMFMVKNGNG (SEQ ID NO: 4); for mouse: LFEVKNNGTT (SEQ ID NO: 5)). Two days after the transfection, dendritic cells were washed and combined with fresh growth media (GlutaMAX-DMEM media) containing pre-spun exosome depleted FBS. Bioengineered exosomes containing [skeletal muscle targeting sequence-Lampl-LTS] fusion protein were isolated using the exosome isolation procedure as described in Example 1.

[0083] Electroporation or transfection using cationic lipid-based transfection reagents was used to introduce the CRISPR-Cas 9 gene editing system (containing double nickase plasmid system from Santa Cruz Biotechnology® and Sigma-Aldrich® directed towards multiple exons of Ppwgcla gene) into skeletal muscle-targeted modified exosomes as described above. For in vivo exosome administration, Ppargcla double nickase CRISPR-Cas9 plasmid- loaded exosomes were re-suspended in 5% (wt/vol) glucose in 200 uL of 0.9% sterile saline at a concentration of 5 ug/uL of total exosomal protein.

[0084] Three month old C57B1/6 mice were either treated with skeletal-muscle targeted exosomes containing CRISPR control plasmid or containing CRISPR-Cas9 PGC-la (Peroxisome proliferator-activated receptor gamma co-activator 1 -alpha) plasmids (200 uL containing 5 ug/uL of total exosomal protein) intravenously once a week for 8 weeks (n = 5 mice per group). Muscle (quadriceps femoris\ heart, liver, and brain were harvested, followed by RNA isolation and gene expression analyses using SYBR®-Green qPCR.

[0085] The results show a targeted reduction oiPGCla expression (-30% of wild-type activity) in skeletal muscle (quadriceps femoris) (Figure 3A), as compared to other tissues including heart, liver and brain (Figure 3 B-D). The reduction in muscle PGCla expression parallels the decrease in expression of down-stream mitochondrial genes co-activated by PGC-la such as Coxii, Coxiv and Tfam (Figure 3A). Mitochondrial complex IV and citrate synthase activity ratio was also measured in skeletal muscle {quadriceps femoris_> tibialis anterior, extensor digitorum longus, and soleus), heart, liver, and brain, and showed reduced mitochondrial complex IV activity (Figure 4A) in skeletal muscle only. Mice were exposed to endurance stress testing 48 hours before tissue harvest (*P < 0.05. Data were analyzed using an unpaired Mest). Mice with PGCla gene editing in muscle using CRISPR-Cas9-loaded exosomes showed reduced exercise capacity in the endurance stress test (Figure 4B).

[0086] This result confirms that exosomes containing CRISPR-Cas9 adapted for genome editing is effectively delivered in vivo and results in targeted genome editing.

Exam^ple 5 - Exosomal delivery of CRISPR-Cas9 system to treat genetic disorders fa vivo

[0087] To determine the efficacy of engineered exosomes to deliver the CRISPR-Cas9 genome editing system for the treatment of disease in vivo, alpha acid glucosidase (GAA) and dystrophin CRISPR-Cas9 gene editing system were designed to treat representative inherited monogenic diseases: acid alpha glucosidase deficiency (a model of Pompe disease) and dystrophin deficiency (a model of Duchenne Muscular Dystrophy), respectively.

[0088] Unmodified exosomes are isolated as described above. Transfection using the cationic lipid-based transfection reagent, Lipofectamine® 3000 (Life Technologies), is used to introduce into the exosomes either the CRISPR control vehicle, the CRISPR-Cas 9 GAA system (including the gRNA sequence to cut and remove mutant GAA exon 6 and dsDNA oligonucleotide repair template to insert healthy wild-type GAA exon 6 using homology-directed repair mechanism), or the CRISPR-Cas 9 dystrophin system (including the gRNA sequence to cut and remove mutant dystrophin exon 23, also known as exon skipping from exon 22 to 24). For in vivo expsome administration, mice are intravenously (via tail vain) administered of total exosomal protein loaded with either the CRISPR-Cas 9 GAA system, CRISPR-Cas 9 dystrophin system or CRISPR control (Cas9 only control) and suspended in sterile PBS to a total volume of 150μΙ, per mouse. Treatment of GAA deficiency in vivo

[0089] Breeding of GAA mice. Four GAA heterozygous breeding pairs (HET; GAA^-/+; 6^neo/6 +) were obtained from Jackson Laboratories (Maine, USA) to generate homozygous GAA knock-outs (GAA KO; GAA^-/-; 6^neo/6^neo). GAA KO mice have a mutation in exon 6, which result in absent to reduced GAA gene expression levels and subsequently, an absence of functional GAA protein. Mice were genotyped at 1 month of age using a standard genotyping kit as per vendor's instructions (REDExtract™-N-Amp Tissue PCR Kit; Sigma Aldrich). During breeding and throughout the experimental period, animals were housed in standard cages with 12-h light/dark cycles and free access to water/rodent chow (Harlan Teklad 8640 22/5) at McMaster University's Central Animal Facility. The study was approved by McMaster University's Animal Research and Ethics Board, and the experimental procedures strictly followed guidelines published by the Canadian Council of Animal Care.

[0090] Three month old GAA KO mice are either treated with exosomes containing CR1SPR-Cas9 control (Cas9 and no gRNA) or containing CRISPR-Cas9 GAA system intravenously (as above) for a total of 3 injections, each separated by 24 hours. WT mice receiving no treatment are used as a positive control to establish wild-type or healthy values. Muscle (tibialis anterior (TA)), diaphragm and heart) and brain samples are extracted, snap frozen, weighed and stored at -80 °C until further analysis. Enzymatic testing is performed to assess GAA activity. Quantitative real-time PCR is also carried out to quantify mRNA transcript abundance. DNA sequencing is performed to confirm gene editing.

[0091] Treatment of GAA KO mice with CRISPR-Cas9 GAA system-loaded exosomes will increase GAA enzyme activity and mRNA levels in brain, skeletal muscle, heart and diaphragm, while protein and mRNA levels in GAA KO mice treated with CRISPR control will remain at very low to negligible amounts and the specific mutation will not be edited (confirmed by DNA sequencing). Thus, this experiment will demonstrate that CRISPR-Cas9 GAA system- loaded exosomes are able to replace the mutant GAA gene sequence with a healthy or wild-type sequence, thereby restoring GAA enzyme activity to treat Pompe disease. Treatment ofDMD in vivo

[0092] Hemizygous male C57BL/10ScSn-Dmdmdx (mdx+/y or mdx) mice (lacking the primary functional dystrophin gene in skeletal muscle) were obtained from Jackson Laboratories (Strain 001801), and housed at McMaster University's Central Animal Facility. These mdx mice have a premature stop codon at exon 23, preventing expression of the primary full length (functional) dystrophin protein in skeletal muscle. Mice were bred in accordance with rules set by McMaster University's Animal Research and Ethics board, following guidelines set forth by the Canadian Council of Animal Care.

[0093] Three month old mdx mice are either treated with exosomes containing CRISPR control system or containing CRISPR-Cas9 dystrophin system intravenously (as above) for a total of 3 injections, each separated by 24 hours. WT mice receiving no treatment are used as a positive control to establish WT or healthy values. Muscle samples (TA, EDL, SOL and diaphragm) are extracted, snap frozen, weighed and stored at -80 °C until further analysis. qRT- PCR is used to measure mRNA abundance. Immunohistochemistry and Western blotting are used to measure dystrophin content.

[0094] Treatment of mdx mice with CRISPR-Cas9 dystrophin system-loaded exosomes will increase dystrophin protein and mRNA content in skeletal muscle, while protein and mRNA levels in mdx mice treated with CRISPR control will remain at very low to negligible amounts. This experiment will show that exosomes incorporating a nuclease genome editing system can be used to perform a desired gene edit such as exon skipping, to treat genetic diseases such as Duchenne Muscular Dystrophy.

Claims

1. Exosomes which are genetically modified to incorporate or express a nuclease genome editing system.

2. The exosomes of claim 1, essentially free from particles having a diameter less than 40 nm or greater than 140 nm.

3. The exosomes of claim 1, which exhibit a zeta potential having a magnitude of at least about 30 mV, and preferably 40 mV or greater. .

4. The exosomes of claim 1, which is a mammalian exosome.

5. The exosomes of claim 1, wherein the nuclease genome editing system is selected from the group consisting of a Transcription Activator-Like Effector Nuclease (TALEN) system, a Zinc-Finger Nuclease (ZFN) system, and a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) nuclease system.

6. The exosomes of claim 5, wherein the nuclease genome editing system is a CRISPR system.

7. The exosomes of claim 6, wherein the CRISPR system comprises a Cas nuclease, one or more guide RNA (gRNA) and optionally, one or more editing regions.

8. The exosomes of claim 7, wherein the Cas nuclease is a Cas9 nuclease.

9. The exosomes of claim 8, wherein the Cas9 nuclease is from Streptococcus pyogenes (SP), Neisseria meningitides, Streptococcus thermophilus, Treponema denticola or Staphylococcus aureus.

10. The exosomes of claim 9, wherein the SP Cas9 nuclease is a wild-type Cas 9 or mutated Cas 9.

11. The exosomes of claim 7, wherein the editing region of the CRISPR system incorporates a gene insertion, a gene deletion, a gene modification, a gene activating sequence, a gene silencing sequence or any combination thereof.

12. The exosomes of claim 1, further modified to incorporate or express a target-specific fusion product comprising a targeting sequence linked to an exosomal membrane marker.

13. The exosomes of claim 12, wherein the exosomal membrane marker is selected from the group consisting of CD9, CD37, CD53, CD63, CD81, CD82, CD151, an integrin, ICAM-1, CDD31, an annexin, TSGlOl, ALIX, lysosome-associated membrane protein 1, lysosome- associated membrane protein 2, lysosomal integral membrane protein and a fragment of any exosomal membrane marker that comprises at least one intact transmembrane domain.

14. The exosomes of claim 12, wherein the targeting sequence is a sequence that targets the brain, the cerebellum, the cerebrum, the hippocampus, glial cells, myelin, nerves, dermis, skin, heart, lysosomes or skeletal muscle.

15. The exosomes of claim 14, wherein the skeletal muscle targeting sequence is selected from the group consisting of SERCA2, acetylcholine receptor epsilon, SCN4A, muscle specific creatine kinase (CK-MM), and fragments thereof.

16. A composition comprising genetically modified exosomes as defined in claim 1 combined with a pharmaceutically acceptable carrier.

17. The composition of claim 16, comprising exosomal protein in an amount of about 1-1000 μg.

18. The composition of claim 16, wherein the nuclease genome editing system is a CRISPR system.

19. A method of treating a genetic disease in a mammal comprising administering to the mammal a composition comprising exosomes which are genetically modified to incorporate a nuclease genome editing system, wherein the nuclease genome editing system is adapted to edit the genome of the mammal at a site causative of the genetic disease to provide treatment of the disease.

20. The method of claim 19, wherein the nuclease genome editing system is selected from the group consisting of a Transcription Activator-Like Effector Nuclease (TALEN) system, a Zinc-Finger Nuclease (ZFN) system, and a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) nuclease system.

21. The method of claim 20, wherein the nuclease genome editing system is a CRISPR system.

22. The method of claim 21, wherein the CRISPR system is a CRISPR-Cas9 nuclease system.

23. The method of claim 19, wherein the genetic disease is an autosomal dominant, autosomal recessive, X-linked or mitochondrial disorder.

24. The method of claim 19, wherein the genetic disease is selected from the group consisting of muscular dystrophy (MD), genetic cancers, peripheral neuropathies, Spinocerebellar Ataxias, Hereditary Spastic Paraparesis, blood disorders, liver disease, polycystic kidney disease, neurofibromatosis type I, connective tissue disorders, genetic Parkinson disease, Huntington disease, cystic fibrosis, lysosomal storage disease, amino acidopathies, organic acidurias, glycogen storage diseases, peroxisomal disorders, fatty acid oxidation defects, and creatine defects.

25. The method of claim 24, wherein the disease is selected from the group consisting of Duchenne MD, limb-girdle MD, occulopharyngeal MD, fascio-scapulo-humeral MD, myotonic MD type 1 and 2, congenital MD, congenital myopathies, Charcot-Marie-Tooth disease, hereditary Amyotrophic Lateral Sclerosis, spinal muscular atrophy, SBMA, aprataxin, senetaxin, SCA1, SCA2, SCA3, SPG7, SPG11, SACS, hemophilia, familial hypercholesterolemia, hereditary spherocytosis, sickle cell anemia, Wilson disease, hemochromatosis, galactosemia, hereditary fructose intolerance, citrin deficiency, alpha- 1 -antitrypsin deficiency, arginosuccinate lyase deficiency, ornithine transcarbamylase deficiency or other urea cycle disorder, Marfan syndrome, Ehlers-Danlos syndrome, osteogenesis imperfect, PINK, PARKIN, Pompe disease, Fabry disease, Gaucher disease, metachromatic leukodystrophy, neural ceroid lipofuscinosis, Tay-Sachs disease, mucopolysaccharidosis, lysosomal acid lipase deficiency, phenylketonuria, MSUD, proprionic acidemia, methylmalonic acidemia, GSDla, GSDlb, GSD2, GSD3, GSD4, GSD5, adrenoleuokodystrophy, Zellweger syndrome, Perrault syndrome (HSD17B4), CPTl, CPT2, TFP, MCAD, VLCAD, LCHAD, AGAT, GAMT, CreaT, BRCA1/BRCA2 associated cancers and ataxia-telangiectasia.

26. The method of claim 23, wherein the mitochondrial disorder is selected form the group consisting of Leber Hereditary Optic Neuropathy (LHON), Leigh Syndrome (LS, subacute sclerosing encephalopathy), Neuropathy, Ataxia, Retinitis Pigmentosa (NARP), MyoNeurogenic Gastrointestinal Encephalopathy (MNGIE), Myoclonic Epilepsy with Ragged Red Fibers (MERRF), Mitochondrial myopathy, Encephalomyopathy, Lactic Acidosis, Stroke-like episodes (MELAS), Kearn-Sayre-Syndrome (KSS), infantile cardiomyopathy due to SC02 mutations, Pearson's syndrome, chronic progressive external ophthalmoplegia associated with mutations in the MT-TLl, POLG, SLC25A4, and ClOorf2 genes, SANDO (Sensory Ataxic Neuropathy, Dysarthria, and Ophthalmoparesis), Alper Syndrome (hepatopathy and encephalopathy due to POLG1 mutations), Combined Oxidative Phosphorylation Defects (COXPD), hereditary spastic paraparesis due to SPG7 mutations and peripheral neuropathy due to Mfn2 mutations.

27. The method of claim 19, wherein 20 ng to about 200 mg of total exosomal protein is administered to the mammal.

28. The method of claim 19, wherein a dosage of exosomes sufficient to deliver an amount of nucleic acid to yield about 0.1 ng/kg to about 100 ug/kg of the nuclease genome editing system components is administered to the mammal.

29. The method of claim 19, wherein the nuclease genome editing system is adapted to correct a mutation in mitochondrial NADH-ubiquinone oxidoreductase chain 4.

30. The method of claim 19, wherein the nuclease genome editing system is adapted to correct a mutation in alpha acid glucosidase (GAA).

31. The method of claim 19, wherein the nuclease genome editing system is adapted to correct a mutation in dystrophin.

32. The method of claim 19, wherein the nuclease genome editing system is adapted to correct a mutation in peroxisome proliferator-activated receptor gamma coactivator 1 -alpha.

33. A method of correcting a genetic mutation in a mammal, comprising administering to the mammal a composition comprising exosomes that are genetically modified to incorporate a nuclease genome editing system adapted to correct the genetic mutation.

34. The method of claim 33, wherein the exosomes are essentially free from particles having a diameter less than 20 nm or greater than 140 nm.

35. The method of claim 33, wherein the exosomes exhibit a zeta potential having a magnitude of at least about 30 mV, and preferably 40 mV or greater.

36. The method of claim 33, wherein the exosomes are isolated from a biological sample using a method comprising the following steps: i) exposing the biological sample to a first centrifugation to remove cellular debris greater man about 7-10 microns in size from the sample and obtaining the supernatant following centrifugation; ii) subjecting the supernatant from step i) to centrifugation to remove microvesicles therefrom; iii) microfiltering the supernatant from step ii) and collecting the microfiltered supernatant; iv) subjecting the microfiltered supernatant from step iii) to at least one round of ultracentrifugation to obtain an exosome pellet; and v) re- suspending the exosome pellet from step iv) in a physiological solution and conducting a second ultracentrifugation in a density gradient and removing the exosome pellet fraction therefrom.

37. The method of claim 33, wherein the exosomes are isolated from a biological sample using a method comprising the following steps: i) optionally exposing the biological sample to pre-enrichment to remove debris therefrom; and ii) subjecting the biological sample to immunoaffinity capture with an antibody cocktail comprising at least three different antibodies having affinity for different exosome surface proteins, wherein the exosomes bind to the antibodies which bind or are bound to a solid support to yield an exosome-solid support complex.

38. The method of claim 33, wherein the genetic mutation is a nuclear gene mutation.

39. The method of claim 33, wherein the genetic mutation is a mitochondrial gene mutation.

40. The method of claim 33, wherein the nuclease genome editing system is adapted to correct a mutation in mitochondrial NADH-ubiquinone oxidoreductase chain 4, alpha acid glucosidase, dystrophin or peroxisome proliferator-activated receptor gamma coactivator 1- alpha.