We acknowledge Brian Tullius for his kind help in editing the manuscript.

Healthy donor buffy coats were obtained as source material from the Central Ohio Region American Red Cross. This research was determined to be exempt research by the Institutional Review Board of Nationwide Children&#8217;s Hospital.
1. Human NK Cell Purification and Expansion
<ol>
	<li>Isolate PBMCs from Buffy Coat12.
	<ol>
		<li>Layer 35 mL of buffy coat sample on 15 mL of Ficoll-Paque.</li>
		<li>Centrifuge at 400 x g for 20 minutes without brake and collect the PBMC from the interface.</li>
		<li>Wash the recovered PBMCs three times by adding at least an equal volume of PBS, centrifuging at 400 x g for 5 minutes, and aspirating the PBC wash. NK cell can be isolated at this stage by RosettesSep13.</li>
	</ol>
	</li>
	<li>Expand NK cells by stimulating with irradiated 10 x 106 mbIL21-expressing feeder cells at Days 0, 7, and 14. Replace media with fresh RPMI containing 10% FBS, 1% Glutamine, 1% Penicillin Streptomycin, and 100 IU/mL of IL-2 for the entire media volume every other day.</li>
</ol>
2. gRNA Design and Selection
<ol>
	<li>Choose the specific genomic loci to target, using online tools, e.g., NCBI, Ensemble. 
	Example. 
	Description: Transforming growth factor beta receptor 2 (TGFBRR2) ectodomain 
	View record: PF08917 
	View InterPro: IPR015013 
	Position: 49 - 157 aa 
	Targeted Sequence: Exon 4 of TGFBR2 gene (ENSG00000163513)</li>
	<li>To design the gRNAs, use CRISPR design web tools such as http://crispr.mit.edu and &#8216;Benchling.&#8217;
	<ol>
		<li>Enter in the DNA sequence chosen in step 2.1. Choose human (hg 19) as a target genome. CRISPR guides (20 nucleotides followed by a PAM sequence: NGG) will be scanned from the sequence entered earlier. It also shows possible off-target matches throughout the selected genome.</li>
		<li>Choose the best three gRNAs which have the highest score, based on their on-target and off-target rates. For example, Table 1 shows the designed CRISPR RNAs to target exon 4 of TGFBR2 gene suggested by CRISPR design web tools.</li>
	</ol>
	</li>
	<li>Order the CRISPR RNAs as synthetic sequence-specific crRNAs.</li>
	<li>Order a conserved, transactivating RNA (tracrRNA) to interact through partial homology with the crRNA.</li>
</ol>
3. Design Deletion Screening Primers
<ol>
	<li>Design primers spanning the gRNA cleavage sites for T7E1 mutation assay.</li>
	<li>Use primers at least 100 bp away from the predicted cleavage site to ensure small insertion-deletion (indels) at the sgRNA target site will appear on 1.5% agarose gel following the mutation assay. Table 2 shows the primers which are used to amplify the TGFBR2 ectodomain.</li>
</ol>
4. Transduction of Human Primary and Expanded NK Cells
Note: Transduction of Cas9/RNPs elements into NK is done by electroporation using 4D system as follows.
<ol>
	<li>Cell Preparation 
	<ol>
		<li>For primary NK cells, incubate freshly isolated NK cells in RPMI medium in the presence of 100 IU/mL of IL-2 for 4 days and perform the electroporation at Day 5. Replace the media every other day as described earlier and the day before transduction.</li>
		<li>For expanded NK cells, stimulate the cells at day 0 with irradiated feeder cells at a ratio of 1:1 and perform the electroporation at Day 5 or 6 or 7. Replace the media every other day as described earlier and the day before transduction.</li>
		<li>On the day of electroporation, prepare a T25 flask filled with 8 mL of fresh RPMI containing 100 IU/mL of IL-2 for cells undergoing electroporation and pre-incubate flasks in a humidified 37 &#176;C and 5% CO2 incubator. 
		Note: Thawed cells or cells that have undergone 2nd or 3rd stimulation can be electroporated at any time after their recovery as described.</li>
		<li>Take 3 - 4 &#215; 106 cells per condition for 26 &#181;L of transduction mix. 
		Note: Very high concentration of NK cells in electroporation solution enhances the transduction rate.</li>
		<li>Wash the cells 3 times with PBS to remove all FBS, which commonly contains RNase activity. Spin them down each time at 300 x g for 8 minutes. 
		Note: Consider 7 electroporation conditions for Cas/RNPs as single gRNA (gRNA1, gRNA2, gRNA3) and a combination of two gRNAs (gRNA1+gRNA2, gRNA1+gRNA3, gRNA2+gRNA3) and one control with no Cas9/RNPs.</li>
	</ol>
	</li>
	<li>Form the crRNA:tracerRNA/complex
	<ol>
		<li>Resuspend crRNAs (gRNA1, gRNA2, and gRNA3) and tracerRNA in 1x&#160;TE solution to final concentrations of 200 &#956;M. Mix 2.2 &#956;L of each 200 &#956;M gRNA with 200 &#956;M tracerRNA as shown in Table 3.</li>
		<li>Heat the samples at 95 &#176;C for 5 min and allow to cool on the bench top to room temperature (15 - 25 &#176;C). Store resuspended RNAs and crRNA: tracerRNA/complex at -20 &#176;C for later use.</li>
	</ol>
	</li>
	<li>Form the RNP complex 
	Note: To save time, form the RNP complex during the washing step 4.1.5.
	<ol>
		<li>For single crRNA:tracrRNA duplex reaction, dilute Cas9 endonuclease to 36 &#956;M as shown by the example in Table 4.</li>
		<li>For combination transduction of crRNA:tracrRNA duplexes, dilute Cas9 endonuclease to 36 &#956;M as shown by the example in Table 5. </li>
		<li>Add Cas9 endonuclease to crRNA:tracrRNA duplexes slowly while swirling pipette tip, over 30 s to 1 minute.</li>
		<li>Incubate the mixture at room temperature for 15 - 20 min. If not ready to use the mixture after incubation, keep the mixture on ice until use.</li>
	</ol>
	</li>
	<li>Electroporation 
	<ol>
		<li>Add the entire supplement to the electroporation solution P3 and keep it at room temperature.</li>
		<li>Resuspend the cell pellet (3 - 4 &#215; 106 cells from step 4.1.5) in 20 &#956;L of P3 primary 4D electroporation solution. Avoid air bubbles while pipetting. 
		Note: The cells should not be left for a long time in P3 solution.</li>
		<li>Immediately add 5 &#181;L of RNP complex (Step 4.3) to the cell suspension.</li>
		<li>Add 1 &#956;L of 100 &#956;M Cas9 electroporation enhancer to the Cas9/RNPs/cell mix.</li>
		<li>Transfer Cas9/RNPs/cell mix into 20 &#956;L electroporation strips.</li>
		<li>Gently tap the strips to make sure that the sample covers the bottom of the strips.</li>
		<li>Start 4D electroporation system and choose the EN-138 program.</li>
	</ol>
	</li>
</ol>
5. Post Transduction
<ol>
	<li>Let the cells rest for 3 minutes in the strips.</li>
	<li>Add 80 &#181;L of the pre-equilibrated culture media to the cuvette and gently transfer the sample into flasks.</li>
	<li>48 hours after transduction, extract genomic DNA from 5 &#215; 105 cells for the gene deletions screening.</li>
	<li>Amplify the gene of interest using the primers designed in step 3.2 with Taq DNA polymerase kits.</li>
	<li>Form PCR amplicon heteroduplexes for T7EI digestion and incubate the product for 30 -&#160;60 minutes with a T7EI enzyme in 37 &#176;C. 
	Note: The T7EI assay is preferred for screening as it is fast, simple and provides clean electrophoresis results compared to using surveyor assay. However, this method cannot detect insertions and deletions of &#60;2 bases that are generated by non-homologous end joining (NHEJ) activity in Cas9 RNPs experiments14.</li>
	<li>Run the digested DNA on 1.5% agarose gel at 110 V for 30 - 45 minutes, every 15 minutes visualize the gel.</li>
	<li>Stimulate the rest of the cells with the mbIL21-expressing feeder cells at a ratio of 1:1.</li>
	<li>Five days after stimulation extract the RNA for gene expression level using qPCR.</li>
	<li>Conduct calcein assays as previously reported12. Briefly, load target cells with calcein AM (in the example shown, 3 &#181;g/mL/1,000,000 DAOY cells was used). Prepare NK cells for cytotoxicity assays by resting overnight in IL2 (100 IU/mL) plus or minus 10 ng/mL soluble TGF&#946;. Conduct calcein assays in the same cytokines as the NK cells were rested in overnight.</li>
</ol>

<ol>
	<li>Guven, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+gene+transfer+into+primary+human+natural+killer+cells+by+retroviral+transduction.">Efficient gene transfer into primary human natural killer cells by retroviral transduction.</a> Experimental Hematology. 33 (11), 1320-1328 (2005).</li><li>Alici, E., Sutlu, T., Sirac Dilber, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retroviral+gene+transfer+into+primary+human+natural+killer+cells.">Retroviral gene transfer into primary human natural killer cells.</a> Methods in Molecular Biology. 508, 127-137 (2009).</li><li>Carlsten, M., Childs, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+Manipulation+of+NK+Cells+for+Cancer+Immunotherapy:+Techniques+and+Clinical+Implications.">Genetic Manipulation of NK Cells for Cancer Immunotherapy: Techniques and Clinical Implications.</a> Frontiers in Immunology. 6, 266 (2015).</li><li>Mehta, R. S., Rezvani, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chimeric+Antigen+Receptor+Expressing+Natural+Killer+Cells+for+the+Immunotherapy+of+Cancer.">Chimeric Antigen Receptor Expressing Natural Killer Cells for the Immunotherapy of Cancer.</a> Frontiers in Immunology. 283, 9 (2018).</li><li>Zuris, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cationic+lipid-mediated+delivery+of+proteins+enables+efficient+protein-based+genome+editing+in+vitro+and+in+vivo.">Cationic lipid-mediated delivery of proteins enables efficient protein-based genome editing in vitro and in vivo.</a> Nature Biotechnology. 33 (1), 73-80 (2015).</li><li>Wang, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+delivery+of+genome-editing+proteins+using+bioreducible+lipid+nanoparticles.">Efficient delivery of genome-editing proteins using bioreducible lipid nanoparticles.</a> PNAS. 113 (11), 2868-2873 (2016).</li><li>Liang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+DNA-free+genome+editing+of+bread+wheat+using+CRISPR/Cas9+ribonucleoprotein+complexes.">Efficient DNA-free genome editing of bread wheat using CRISPR/Cas9 ribonucleoprotein complexes.</a> Nature Communications. 8, 14261 (2017).</li><li>DeWitt, M. A., Corn, J. E., Carroll, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome+editing+via+delivery+of+Cas9+ribonucleoprotein.">Genome editing via delivery of Cas9 ribonucleoprotein.</a> Methods. , 9-15 (2017).</li><li>Rezvani, K., Rouce, R., Liu, E., Shpall, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+Natural+Killer+Cells+for+Cancer+Immunotherapy.">Engineering Natural Killer Cells for Cancer Immunotherapy.</a> Molecular Therapy. 25 (8), 1769-1781 (2017).</li><li>Sutlu, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+intracellular+antiviral+defense+mechanisms+augments+lentiviral+transduction+of+human+natural+killer+cells:+implications+for+gene+therapy.">Inhibition of intracellular antiviral defense mechanisms augments lentiviral transduction of human natural killer cells: implications for gene therapy.</a> Human Gene Therapy. 23 (10), 1090-1100 (2012).</li><li>Viel, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TGF-beta+inhibits+the+activation+and+functions+of+NK+cells+by+repressing+the+mTOR+pathway.">TGF-beta inhibits the activation and functions of NK cells by repressing the mTOR pathway.</a> Science Signaling. 9 (415), (2016).</li><li>Somanchi, S. S., Senyukov, V. V., Denman, C. J., Lee, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expansion,+purification,+and+functional+assessment+of+human+peripheral+blood+NK+cells.">Expansion, purification, and functional assessment of human peripheral blood NK cells.</a> JoVE. (48), (2011).</li><li>Lee, D. A., Verneris, M. R., Campana, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acquisition,+preparation,+and+functional+assessment+of+human+NK+cells+for+adoptive+immunotherapy.">Acquisition, preparation, and functional assessment of human NK cells for adoptive immunotherapy.</a> Methods in Molecular Biology. , 61-77 (2010).</li><li>Vouillot, L., Thelie, A., Pollet, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+T7E1+and+surveyor+mismatch+cleavage+assays+to+detect+mutations+triggered+by+engineered+nucleases.">Comparison of T7E1 and surveyor mismatch cleavage assays to detect mutations triggered by engineered nucleases.</a> G3. 5 (3), 407-415 (2015).</li><li>Eyquem, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+a+CAR+to+the+TRAC+locus+with+CRISPR/Cas9+enhances+tumour+rejection.">Targeting a CAR to the TRAC locus with CRISPR/Cas9 enhances tumour rejection.</a> Nature. 543 (7643), 113-117 (2017).</li><li>Liang, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+and+highly+efficient+mammalian+cell+engineering+via+Cas9+protein+transfection.">Rapid and highly efficient mammalian cell engineering via Cas9 protein transfection.</a> Journal of Biotechnology. 208, 44-53 (2015).</li><li>Kim, S., Kim, D., Cho, S. W., Kim, J., Kim, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+efficient+RNA-guided+genome+editing+in+human+cells+via+delivery+of+purified+Cas9+ribonucleoproteins.">Highly efficient RNA-guided genome editing in human cells via delivery of purified Cas9 ribonucleoproteins.</a> Genome Research. 24 (6), 1012-1019 (2014).</li><li>Chmielecki, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genomic+Profiling+of+a+Large+Set+of+Diverse+Pediatric+Cancers+Identifies+Known+and+Novel+Mutations+across+Tumor+Spectra.">Genomic Profiling of a Large Set of Diverse Pediatric Cancers Identifies Known and Novel Mutations across Tumor Spectra.</a> Cancer Research. 77 (2), 509-519 (2017).</li><li>Schultz, L. M., Majzner, R., Davis, K. L., Mackall, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+developments+in+immunotherapy+for+pediatric+solid+tumors.">New developments in immunotherapy for pediatric solid tumors.</a> Current Opinion in Pediatrics. 30 (1), 30-39 (2018).</li></ol>

DAL serves/has served as a consultant for Courier Therapeutics, Obsidian Therapeutics, Intellia Therapeutics, Merck Research Laboratories, and Miltenyi Biotec, and has equity/Leadership in CytoSen Therapeutics.

DNA-dependent modification of NK cells has been challenging4,9. We, therefore, introduced directly a synthetically preformed ribonucleoprotein (RNPs) complex and Cas9 protein as purified protein into primary and expanded NK cells8. This method allowed us to eliminate capping, tailing, and other transcriptional and translational processes started by RNA polymerase II, which may cause NK cell apoptosis associated with DNA-dependent transduct...

Cancer immunotherapy has been advanced in recent years. Genetically-modified chimeric antigen receptor (CAR) T cells are an excellent example of engineered immune cells successfully deployed in cancer immunotherapy. These cells were recently approved by the FDA for treatment against CD19 + B cell malignancies, but success has so far been limited to diseases bearing a few targetable antigens, and targeting such limited antigenic repertoires is prone to failure by immune escape. Furthermore, CAR T cells have been focused on the use of autologous T cells because of the risk of graft-versus-host disease caused by allogeneic T cells. In contrast, NK cells are able to kill tumor targets in an antigen-independent manner and do not cause GvHD, which makes them a good candidate for cancer immunotherapy6,7,8,9.
CRISPR/Cas9 technology has been used recently in engineering immune cells, but genetically reprogramming NK cells with plasmids has always been challenging. This has been due to difficulties in transgene delivery in a DNA dependent manner such as lentiviral and retroviral transduction causing substantial procedure-associated NK cell apoptosis and the limited production of genetically engineered NK cells4,9.
Many innate immune cells express high levels of receptors for pathogen-associated molecular patterns such as Retinoic acid-inducible gene I (RIG-I), which enable heightened recognition of foreign DNA. Suppression of these pathways has enabled higher transduction efficiency in NK cells when using DNA-based methods for genetic modification10.
We describe here the method for using a DNA-free genome editing of primary and expanded human NK cells utilizing Cas9 ribonucleoprotein complexes (Cas9/RNPs). Cas9/RNPs is composed of three components, recombinant Cas9 protein complexed with synthetic single-guide RNA comprised of a complexed crRNA and tracerRNA. These Cas9/RNPs are capable of cleaving genomic targets with higher efficiency as compared to foreign DNA-dependent approaches due to their delivery as functional complexes. Additionally, rapid clearance of Cas9/RNPs from the cells may reduce the off-target effects such as induction of apoptosis. Thus, they can be used to generate knock-outs, or knock-ins when combined with DNA for homologous recombination6,7. We showed that electroporation of Cas9/RNPs is an easy and relatively efficient method that overcomes the previous constraints of genetic modification in NK cells.
TGF&#946; is a major immunosuppressive cytokine, which inhibits the activation and functions of NK cells. It has been suggested that targeting the TGF&#946; pathway can increase immune cell functions. We targeted the region encoding TGBR2 ectodomain which binds TGF&#946;11. The representative results show a significant decrease in the level of mRNA expression of this gene and further demonstrate that the modified NK cells become resistant to TGF&#946;. In addition, the modified cells retain viability and proliferative potential, as they are able to be expanded post-electroporation using irradiated feeder cells. Therefore, the following method is a promising approach to genetically manipulate NK cells for any further clinical or research purposes.

<table>
	<tbody>
		<tr>
			<td>RosetteSep&#8482; Human NK Cell Enrichment Cocktail</td>
			<td>STEMCELL Technologies</td>
			<td>15065</td>
			<td>The RosetteSep&#8482; Human NK Cell Enrichment Cocktail is designed to isolate NK cells from whole blood by negative selection.</td>
		</tr>
		<tr>
			<td>Ficoll-Paque&#174; PLUS</td>
			<td>GE Healthcare - Life Sciences</td>
			<td>17-1440-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Alt-R&#174; CRISPR-Cas9 tracrRNA</td>
			<td>Integrated DNA Technologies</td>
			<td>1072532</td>
			<td>TracrRNA that contains proprietary chemical modifications conferring increased nuclease resistance. Hybridizes to crRNA to activate the Cas9 enzyme</td>
		</tr>
		<tr>
			<td>Alt-R&#174; CRISPR-Cas9 crRNA</td>
			<td>Integrated DNA Technologies</td>
			<td></td>
			<td>Synthetically produced as Alt-R&#174; CRISPR-Cas9 crRNA, based on the sequence of designed gRNA targeting the gene of intrest</td>
		</tr>
		<tr>
			<td>Alt-R&#174; Genome Editing Detection Kit</td>
			<td>Integrated DNA Technologies</td>
			<td>1075931</td>
			<td>Each kit contains T7EI endonuclease, T7EI reaction buffer, and T7EI assay controls.</td>
		</tr>
		<tr>
			<td>Platinum&#174; Taq DNA Polymerase High Fidelity</td>
			<td>Invitrogen</td>
			<td>11304-011</td>
			<td></td>
		</tr>
		<tr>
			<td>4D-Nucleofector&#8482; System</td>
			<td>Lonza</td>
			<td>AAF-1002B</td>
			<td></td>
		</tr>
		<tr>
			<td>Human recombinant IL-2 Protein</td>
			<td>Novartis</td>
			<td>65483-0116-07</td>
			<td></td>
		</tr>
		<tr>
			<td>P3 Primary Cell 4D-Nucleofector&#8482; X Kit</td>
			<td>Lonza</td>
			<td>V4XP-3032</td>
			<td>Contains pmaxGFP&#8482; Vector, Nucleofector&#8482; Solution, Supplement, 16-well Nucleocuvette&#8482; Strips</td>
		</tr>
		<tr>
			<td>Non-targeting: Custom siRNA, Standard 0.05 2mol ON-TARGETplus</td>
			<td>Dharmacon</td>
			<td>CTM-360019</td>
			<td></td>
		</tr>
		<tr>
			<td>Alt-R&#174; S.p. Cas9 Nuclease 3NLS</td>
			<td>Integrated DNA Technologies</td>
			<td>1074181</td>
			<td>Cas9 Nuclease</td>
		</tr>
		<tr>
			<td>DNeasy&#174; Blood &#38; Tissue Handbook</td>
			<td>Qiagen</td>
			<td>69504</td>
			<td></td>
		</tr>
		<tr>
			<td>RNeasy Mini Kit</td>
			<td>Qiagen</td>
			<td>74104</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcein AM</td>
			<td>ThermoFisher</td>
			<td>C3099</td>
			<td></td>
		</tr>
		<tr>
			<td>TGF&#946;</td>
			<td>Biolegend</td>
			<td>580706</td>
			<td></td>
		</tr>
		<tr>
			<td>Alt-R&#174; CRISPR-Cas9 Control Kit, Human</td>
			<td>Integrated DNA Technologies</td>
			<td>1072554</td>
			<td>Includes tracrRNA, HPRT positive control crRNA, negative control crRNA#1, HPRT Primer Mix, and Nuclease-Free Duplex Buffer.</td>
		</tr>
		<tr>
			<td>IDTE pH 7.5 (1X TE Solution)</td>
			<td>Integrated DNA Technologies</td>
			<td>11-01-02-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Alt-R&#174; Cas9 Electroporation Enhancer</td>
			<td>Integrated DNA Technologies</td>
			<td>1075915</td>
			<td>Cas9 Electroporation Enhancer</td>
		</tr>
	</tbody>
</table>

generation of knock-out primary and expanded human nk cells using cas9 ribonucleoproteins

CRISPR/Cas9 technology is accelerating genome engineering in many cell types, but so far, gene delivery and stable gene modification have been challenging in primary NK cells. For example, transgene delivery using lentiviral or retroviral transduction resulted in a limited yield of genetically-engineered NK cells due to substantial procedure-associated NK cell apoptosis. We describe here a DNA-free method for genome editing of human primary and expanded NK cells using Cas9 ribonucleoprotein complexes (Cas9/RNPs). This method allowed efficient knockout of the TGFBR2 and HPRT1 genes in NK cells. RT-PCR data showed a significant decrease in gene expression level, and a cytotoxicity assay of a representative cell product suggested that the RNP-modified NK cells became less sensitive to TGF&#946;. Genetically modified cells could be expanded post-electroporation by stimulation with irradiated mbIL21-expressing feeder cells.

Electroporation Efficiency
To optimize electroporation of Cas9/RNPs, we tested 16 different programs with transduction of GFP non-targeting siRNA and DNA plasmid into NK cells. Flow cytometry assay showed that the EN-138 had the highest percentage of cell viability and transduction efficiency (35% live GFP positive cells) for both particles (Figure 1 &#38; Figure 2...

Watch this Scientific Journal Video about Generation of Knock-out Primary and Expanded Human NK Cells Using Cas9 Ribonucleoproteins at JoVE.com

Generation of Knock-out Primary and Expanded Human NK Cells Using Cas9 Ribonucleoproteins

Here, we present a protocol to genetically modify primary or expanded human natural killer (NK) cells using Cas9 Ribonucleoproteins (Cas9/RNPs). By using this protocol, we generated human NK cells deficient for transforming growth factor&#8211;b receptor 2 (TGFBR2) and hypoxanthine phosphoribosyltransferase 1 (HPRT1).

CRISPR/Cas9 technology is accelerating genome engineering in many cell types, but so far, gene delivery and stable gene modification have been challenging ...

generation-knock-out-primary-expanded-human-nk-cells-using-cas9

Research

JoVE Journal

Immunology and Infection

12.3K Views.  Nationwide Children's Hospital. Here, we present a protocol to genetically modify primary or expanded human natural killer (NK) cells using Cas9 Ribonucleoproteins (Cas9/RNPs). By using this protocol, we generated human NK cells deficient for transforming growth factor–b receptor 2 (TGFBR2) and hypoxanthine phosphoribosyltransferase 1 (HPRT1).

Video: Generation of Knock-out Primary and Expanded Human NK Cells Using Cas9 Ribonucleoproteins

Expansion, Purification, and Functional Assessment of Human Peripheral Blood NK Cells

Natural killer (NK) cells play an important role in immune surveillance against a variety of infectious microorganisms and tumors. Limited availability of NK cells and ability to expand in vitro has restricted development of NK cell immunotherapy. Here we describe a method to efficiently expand vast quantities of functional NK cells ex vivo using K562 cells expressing membrane-bound IL21, as an artificial antigen-presenting cell (aAPC).
NK cell adoptive therapies to date have utilized a cell product obtained by steady-state leukapheresis of the donor followed by depletion of T cells or positive selection of NK cells. The product is usually activated in IL-2 overnight and then administered the following day 1. Because of the low frequency of NK cells in peripheral blood, relatively small numbers of NK cells have been delivered in clinical trials.
The inability to propagate NK cells in vitro has been the limiting factor for generating sufficient cell numbers for optimal clinical outcome. Some expansion of NK cells (5-10 fold over 1-2 weeks) has be achieved through high-dose IL-2 alone 2. Activation of autologous T cells can mediate NK cell expansion, presumably also through release of local cytokine 3. Support with mesenchymal stroma or artificial antigen presenting cells (aAPCs) can support the expansion of NK cells from both peripheral blood and cord blood 4. Combined NKp46 and CD2 activation by antibody-coated beads is currently marketed for NK cell expansion (Miltenyi Biotec, Auburn CA), resulting in approximately 100-fold expansion in 21 days.
Clinical trials using aAPC-expanded or -activated NK cells are underway, one using leukemic cell line CTV-1 to prime and activate NK cells5 without significant expansion. A second trial utilizes EBV-LCL for NK cell expansion, achieving a mean 490-fold expansion in 21 days6. The third utilizes a K562-based aAPC transduced with 4-1BBL (CD137L) and membrane-bound IL-15 (mIL-15)7, which achieved a mean NK expansion 277-fold in 21 days. Although, the NK cells expanded using K562-41BBL-mIL15 aAPC are highly cytotoxic in vitro and in vivo compared to unexpanded NK cells, and participate in ADCC, their proliferation is limited by senescence attributed to telomere shortening8. More recently a 350-fold expansion of NK cells was reported using K562 expressing MICA, 4-1BBL and IL159.
Our method of NK cell expansion described herein produces rapid proliferation of NK cells without senescence achieving a median 21,000-fold expansion in 21 days.

Here we describe a method to efficiently expand and purify large numbers of human NK cells and assess their function.

Natural killer (NK) cells play an important role in immune surveillance against a variety of infectious microorganisms and tumors. Limited availability of ...

Generation of Organotypic Raft Cultures from Primary Human Keratinocytes

The development of organotypic epithelial raft cultures has provided researchers with an efficient in vitro system that faithfully recapitulates epithelial differentiation. There are many uses for this system. For instance, the ability to grow three-dimensional organotypic raft cultures of keratinocytes has been an important milestone in the study of human papillomavirus (HPV)1. The life cycle of HPV is tightly linked to the differentiation of squamous epithelium2. Organotypic epithelial raft cultures as demonstrated here reproduce the entire papillomavirus life cycle, including virus production3,4,5. In addition, these raft cultures exhibit dysplastic lesions similar to those observed upon in vivo infection with HPV. Hence this system can also be used to study epithelial cell cancers, as well as the effect of drugs on epithelial cell differentiation in general. Originally developed by Asselineau and Prunieras6 and modified by Kopan et al.7, the organotypic epithelial raft culture system has matured into a general, relatively easy culture model, which involves the growth of cells on collagen plugs maintained at an air-liquid interface (Figure 1A). Over the course of 10-14 days, the cells stratify and differentiate, forming a full thickness epithelium that produces differentiation-specific cytokeratins. Harvested rafts can be examined histologically, as well as by standard molecular and biochemical techniques. In this article, we describe a method for the generation of raft cultures from primary human keratinocytes. The same technique can be used with established epithelial cell lines, and can easily be adapted for use with epithelial tissue from normal or diseased biopsies8. Many viruses target either the cutaneous or mucosal epithelium as part of their replicative life cycle. Over the past several years, the feasibility of using organotypic raft cultures as a method of studying virus-host cell interactions has been shown for several herpesviruses, as well as adenoviruses, parvoviruses, and poxviruses9. Organotypic raft cultures can thus be adapted to examine viral pathogenesis, and are the only means to test novel antiviral agents for those viruses that are not cultivable in permanent cell lines.

An in vitro method to mimic in vivo epithelial differentiation is described. Many viruses target epithelial cells as part of their viral life cycle, and this method provides a means of examining virus:host interactions that more closely resembles that which occurs in vivo. This technique can be used with primary keratinocytes, established cell lines, as well as normal or diseased biopsy tissue.

The development of organotypic epithelial raft cultures has provided researchers with an efficient in vitro system that faithfully recapitulates ...

Generation of Induced Regulatory T Cells from Primary Human Na&iuml;ve and Memory T Cells

The development and maintenance of immunosuppressive CD4+ regulatory T cells (Tregs) contribute to the peripheral tolerance needed to remain in immunologic homeostasis with the vast amount of self and commensal antigens in and on the human body. Perturbations in the balance between Tregs and inflammatory conventional T cells can result in immunopathology or cancer. Although therapeutic injection of Tregs has been shown to be efficacious in murine models of colitis1 , type I diabetes2 , rheumatoid arthritis and graft versus host disease,4 several fundamental differences in human versus mouse Treg biology5 has thus far precluded clinical use. The lack of sufficient number, purity, stability and homing specificity of therapeutic Tregs necessitated a dynamic platform of human Treg development on which to optimize conditions for their ex vivo expansion6.
Here we describe a method for the differentiation of induced Tregs (iTregs) from a single human peripheral blood donor which can be broken down into four stages: isolation of peripheral blood mononuclear cells, magnetic selection of CD4+ T cells, in vitro cell culture and fluorescence activated cell sorting (FACS) of T cell subsets. Since the Treg signature transcription factor forkhead box P3 (FoxP3) is an activation-induced transcription factor in humans7 and no other unique marker exists, a combinatorial panel of markers must be used to identify T cells with suppressor activity. After six days in culture, cells in our system can be demarcated into na&iuml;ve T cells, memory T cells or iTregs based on their relative expression of CD25 and CD45RA. As memory and na&iuml;ve T cells have different reported polarization requirements and plasticities8 , pre-sorting of the initial T cell population into CD45RA+ and CD45RO+ subsets can be used to examine these discrepancies. Consistent with others, our CD25HiCD45RA- iTregs express high levels of FoxP39 , GITR and CTLA-411 and low levels of CD12712 . Following FACS of each population, resultant cells can be used in a suppressor assay which evaluates the relative ability to retard the proliferation of carboxyfluorescein succinimidyl ester (CFSE)-labeled autologous T cells.

Generation of Induced Regulatory T Cells from Primary Human Na&#239;ve and Memory T Cells

We describe a method for generating regulatory, memory and na&#239;ve T cells from a single human blood donor. Polarized Tregs can be then compared to other subsets in a variety of genetic and functional applications with genetic homogeneity, including a suppression assay also detailed here.

The development and maintenance of immunosuppressive CD4+ regulatory T cells (Tregs) contribute to the peripheral tolerance needed to remain in ...

piggyBac Transposon System Modification of Primary Human T Cells

The piggyBac transposon system is naturally active, originally derived from the cabbage looper moth1,2. This non-viral system is plasmid based, most commonly utilizing two plasmids with one expressing the piggyBac transposase enzyme and a transposon plasmid harboring the gene(s) of interest between inverted repeat elements which are required for gene transfer activity. PiggyBac mediates gene transfer through a "cut and paste" mechanism whereby the transposase integrates the transposon segment into the genome of the target cell(s) of interest. PiggyBac has demonstrated efficient gene delivery activity in a wide variety of insect1,2, mammalian3-5, and human cells6 including primary human T cells7,8. Recently, a hyperactive piggyBac transposase was generated improving gene transfer efficiency9,10.
Human T lymphocytes are of clinical interest for adoptive immunotherapy of cancer11. Of note, the first clinical trial involving transposon modification of human T cells using the Sleeping beauty transposon system has been approved12. We have previously evaluated the utility of piggyBac as a non-viral methodology for genetic modification of human T cells. We found piggyBac to be efficient in genetic modification of human T cells with a reporter gene and a non-immunogenic inducible suicide gene7. Analysis of genomic integration sites revealed a lack of preference for integration into or near known proto-oncogenes13. We used piggyBac to gene-modify cytotoxic T lymphocytes to carry a chimeric antigen receptor directed against the tumor antigen HER2, and found that gene-modified T cells mediated targeted killing of HER2-positive tumor cells in vitro and in vivo in an orthotopic mouse model14. We have also used piggyBac to generate human T cells resistant to rapamycin, which should be useful in cancer therapies where rapamycin is utilized15.
Herein, we describe a method for using piggyBac to genetically modify primary human T cells. This includes isolation of peripheral blood mononuclear cells (PBMCs) from human blood followed by culture, gene modification, and activation of T cells. For the purpose of this report, T cells were modified with a reporter gene (eGFP) for analysis and quantification of gene expression by flow cytometry.
PiggyBac can be used to modify human T cells with a variety of genes of interest. Although we have used piggyBac to direct T cells to tumor antigens14, we have also used piggyBac to add an inducible safety switch in order to eliminate gene modified cells if needed7. The large cargo capacity of piggyBac has also enabled gene transfer of a large rapamycin resistant mTOR molecule (15 kb)15. Therefore, we present a non-viral methodology for stable gene-modification of primary human T cells for a wide variety of purposes.

piggyBac Transposon System Modification of Primary Human T Cells

We describe a method to genetically modify primary human T cells with a transgene using the non-viral piggyBac transposon system. T cells modified to using the piggyBac transposon system exhibit stable transgene expression.

The piggyBac transposon system is naturally active, originally derived from the cabbage looper moth1,2. This non-viral system is plasmid based, most ...

Generation of Human Alloantigen-specific T Cells from Peripheral Blood

The study of human T lymphocyte biology often involves examination of responses to activating ligands. T cells recognize and respond to processed peptide antigens presented by MHC (human ortholog HLA) molecules through the T cell receptor (TCR) in a highly sensitive and specific manner. While the primary function of T cells is to mediate protective immune responses to foreign antigens presented by self-MHC, T cells respond robustly to antigenic differences in allogeneic tissues. T cell responses to alloantigens can be described as either direct or indirect alloreactivity. In alloreactivity, the T cell responds through highly specific recognition of both the presented peptide and the MHC molecule. The robust oligoclonal response of T cells to allogeneic stimulation reflects the large number of potentially stimulatory alloantigens present in allogeneic tissues. While the breadth of alloreactive T cell responses is an important factor in initiating and mediating the pathology associated with biologically-relevant alloreactive responses such as graft versus host disease and allograft rejection, it can preclude analysis of T cell responses to allogeneic ligands. To this end, this protocol describes a method for generating alloreactive T cells from naive human peripheral blood leukocytes (PBL) that respond to known peptide-MHC (pMHC) alloantigens. The protocol applies pMHC multimer labeling, magnetic bead enrichment and flow cytometry to single cell in vitro culture methods for the generation of alloantigen-specific T cell clones. This enables studies of the biochemistry and function of T cells responding to allogeneic stimulation.

This article describes a method for the generation and propagation of human T cell clones that specifically respond to a defined alloantigen. This protocol can be adapted for cloning human T cells specific for a variety of peptide-MHC ligands.

The study of human T lymphocyte biology often involves examination of responses to activating ligands. T cells recognize and respond to processed peptide ...

Generation of Recombinant Human IgG Monoclonal Antibodies from Immortalized Sorted B Cells

Finding new methods for generating human monoclonal antibodies is an active research field that is important for both basic and applied sciences, including the development of immunotherapeutics. However, the techniques to identify and produce such antibodies tend to be arduous and sometimes the heavy and light chain pair of the antibodies are dissociated. Here, we describe a relatively simple, straightforward protocol to produce human recombinant monoclonal antibodies from human peripheral blood mononuclear cells using immortalization with Epstein-Barr Virus (EBV) and Toll-like receptor 9 activation. With an adequate staining, B cells producing antibodies can be isolated for subsequent immortalization and clonal expansion. The antibody transcripts produced by the immortalized B cell clones can be amplified by PCR, sequenced as corresponding heavy and light chain pairs and cloned into immunoglobulin expression vectors. The antibodies obtained with this technique can be powerful tools to study relevant human immune responses, including autoimmunity, and create the basis for new therapeutics.

Synthesis of human monoclonal antibodies is the first step in studies aimed at unraveling the pathophysiological mechanisms of auto-antibody-mediated immune responses. We have developed a protocol to generate recombinant human immunoglobulin G (IgG) monoclonal antibodies from blood sorted B cells, including B-cell isolation, antibody cloning and in vitro synthesis.

Finding new methods for generating human monoclonal antibodies is an active research field that is important for both basic and applied sciences, ...

Generation of Human Monocyte-derived Dendritic Cells from Whole Blood

Dendritic cells (DCs) recognize foreign structures of different pathogens, such as viruses, bacteria, and fungi, via a variety of pattern recognition receptors (PRRs) expressed on their cell surface and thereby activate and regulate immunity. 
The major function of DCs is the induction of adaptive immunity in the lymph nodes by presenting antigens via MHC I and MHC II molecules to na&#239;ve T lymphocytes. Therefore, DCs have to migrate from the periphery to the lymph nodes after the recognition of pathogens at the sites of infection. For in vitro experiments or DC vaccination strategies, monocyte-derived DCs are routinely used. These cells show similarities in physiology, morphology, and function to conventional myeloid dendritic cells. They are generated by interleukin 4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation of monocytes isolated from healthy donors. Here, we demonstrate how monocytes are isolated and stimulated from anti-coagulated human blood after peripheral blood mononuclear cell (PBMC) enrichment by density gradient centrifugation. Human monocytes are differentiated into immature DCs and are ready for experimental procedures in a non-clinical setting after 5 days of incubation.

Here, we demonstrate how monocytes are isolated by magnetic bead separation from peripheral blood mononuclear cells after density gradient centrifugation of human anti-coagulated blood. Following incubation for 5 days, human monocytes are differentiated into immature dendritic cells and are ready for experimental procedures in a non-clinical setting.

Dendritic cells (DCs) recognize foreign structures of different pathogens, such as viruses, bacteria, and fungi, via a variety of pattern recognition ...

Dextran Enhances the Lentiviral Transduction Efficiency of Murine and Human Primary NK Cells

The efficient transduction of specific genes into natural killer (NK) cells has been a major challenge. Successful transductions are critical to defining the role of the gene of interest in the development, differentiation, and function of NK cells. Recent advances related to chimeric antigen receptors (CARs) in cancer immunotherapy accentuate the need for an efficient method to deliver exogenous genes to effector lymphocytes. The efficiencies of lentiviral-mediated gene transductions into primary human or mouse NK cells remain significantly low, which is a major limiting factor. Recent advances using cationic polymers, such as polybrene, show an improved gene transduction efficiency in T cells. However, these products failed to improve the transduction efficiencies of NK cells. This work shows that dextran, a branched glucan polysaccharide, significantly improves the transduction efficiency of human and mouse primary NK cells. This highly reproducible transduction methodology provides a competent tool for transducing human primary NK cells, which can vastly improve clinical gene delivery applications and thus NK cell-based cancer immunotherapy.

The goal of this study was to formulate technologies that allow for successful gene transduction in primary natural killer (NK) cells. The dextran-mediated lentiviral transduction of human or mouse primary NK cells results in higher gene expression efficiencies. This method of gene transduction will vastly improve NK cell genetic manipulation.

The efficient transduction of specific genes into natural killer (NK) cells has been a major challenge. Successful transductions are critical to defining ...

Small RNA Transfection in Primary Human Th17 Cells by Next Generation Electroporation

CD4+ T cells can differentiate into several subsets of effector T helper cells depending on the surrounding cytokine milieu. Th17 cells can be generated from na&#239;ve CD4+ T cells in vitro by activating them in the presence of the polarizing cytokines IL-1&#946;, IL-6, IL-23, and TGF&#946;. Th17 cells orchestrate immunity against extracellular bacteria and fungi, but their aberrant activity has also been associated with several autoimmune and inflammatory diseases. Th17 cells are identified by the chemokine receptor CCR6 and defined by their master transcription factor, ROR&#947;t, and characteristic effector cytokine, IL-17A. Optimized culture conditions for Th17 cell differentiation facilitate mechanistic studies of human T cell biology in a controlled environment. They also provide a setting for studying the importance of specific genes and gene expression programs through RNA interference or the introduction of microRNA (miRNA) mimics or inhibitors. This protocol provides an easy to use, reproducible, and highly efficient method for transient transfection of differentiating primary human Th17 cells with small RNAs using a next generation electroporation device.

Next generation electroporation is an efficient method for transfecting human Th17 cells with small RNAs to alter gene expression and cell behavior.

CD4+ T cells can differentiate into several subsets of effector T helper cells depending on the surrounding cytokine milieu. Th17 cells can be generated ...

A Flow Cytometry-Based Cytotoxicity Assay for the Assessment of Human NK Cell Activity

Within the innate immune system, effector lymphocytes known as natural killer (NK) cells play an essential role in host defense against aberrant cells, specifically eliminating tumoral and virally infected cells. Approximately 30 known monogenic defects, together with a host of other pathological conditions, cause either functional or classic NK cell deficiency, manifesting in reduced or absent cytotoxic activity. Historically, cytotoxicity has been investigated with radioactive methods, which are cumbersome, expensive and potentially hazardous. This article describes a streamlined, clinically applicable flow cytometry-based method to quantify NK cell cytotoxic activity. In this assay, peripheral blood mononuclear cells (PBMCs) or purified NK cell preparations are co-incubated at different ratios with a target tumor cell line known to be sensitive to NK cell-mediated cytotoxicity (NKCC). The target cells are pre-labeled with a fluorescent dye to allow their discrimination from the effector cells (NK cells). After the incubation period, killed target cells are identified by a nucleic acid stain, which specifically permeates dead cells. This method is amenable to both diagnostic and research applications and, thanks to the multi-parameter capabilities of flow cytometry, has the added advantage of potentially enabling a deeper analysis of NK cell phenotype and function.

A flow cytometry-based method to quantitatively determine the cytotoxic activity of human natural killer cells is shown here.

Within the innate immune system, effector lymphocytes known as natural killer (NK) cells play an essential role in host defense against aberrant cells, ...