Name: genome engineering of primary human b cells using crispr/cas9
Uploaded: 2020-11-03T14:00:00
Description: Watch this Scientific Journal Video about Genome Engineering of Primary Human B Cells Using CRISPR/Cas9 at JoVE.com

This work was funded by the Children&#8217;s Cancer Research Fund (CCRF) and NIH R01 AI146009 to B.S.M.

Leukapheresis samples from healthy donors were obtained from a local blood bank. All experiments described here were determined to be exempt for research by the Institutional Review Board (IRB) and were approved by the Institutional Biosafety Committee (IBC) at the University of Minnesota.
NOTE: All experiments were performed in compliance with the universal precaution for bloodborne pathogens, with sterile/aseptic techniques and proper biosafety level-2 equipment.
1....

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Precise genome engineering in primary human B cells has been challenging until recently9,10. We had previously published protocols using CRISPR/Cas9 to engineer primary human B cells9. Here, we outline improved protocols for B-cell isolation, expansion, and engineering to allow for efficient KO of CD19 or for knocking-in EGFP.
Here we demonstrate that our expansion protocol allows the rapid expansion of...

B cells are a subgroup of the lymphocyte lineage derived from hematopoietic stem cells. They perform a critical role in the adaptive humoral immune system by producing large amounts of antibodies in response to immune challenges1. B cells are also precursors of memory B cells and the terminally differentiated, long-lived plasma cells, thereby providing lasting humoral immunity2. Plasma cells, in particular, are unique among immune cells in their ability to produce large amounts of a specific antibody while surviving for years or decades3. Additionally, the ease of isolation from peripheral blood makes the B-cell lineage an excellent candidate for novel cell-based therapies4.
Previously, random integration methods, such as those using lentiviral vectors or a Sleeping Beauty transposon, have been used to engineer B cells for transgene delivery and expression5,6,7,8. However, the non-specific nature of these approaches makes it difficult to study the biological functions of a specific gene in the B cells and carries an inherent risk of insertional mutagenesis and variable transgene expression and/or silencing in the therapeutic setting.
The CRISPR/Cas9 system is a powerful genome engineering tool that allows researchers to precisely edit the genome of various cells in numerous species. Recently, two groups, including our own, have successfully developed methods for ex vivo expansion and targeted genome engineering of primary human B cells9,10. We will describe the process of purifying primary human B cells from a leukaphoresis sample. After that, we will describe our updated protocol for B-cell expansion and activation of isolated B cells. We will then describe a process for knocking out cluster of differentiation 19 (CD19), a specific B-cell receptor and a hallmark of B cells, by electroporation to introduce CRISPR/Cas9 mRNA together with CD19 sgRNA into activated B cells.
Cas9 mRNA gets translated and binds to the CD19 sgRNA to form a CRISPR/Cas9-sgRNA ribonucleoprotein complex (RNP). Subsequently, sgRNA in the complex leads Cas9 to create double-strand break (DSB) at the target sequence on exon 2 of the gene. The cells will repair the DSB by &#8220;non-homologous end joining&#8221; by introducing or deleting nucleotides, leading to frameshift mutation and causing the gene to be knocked out. We will then measure the loss of CD19 by flow cytometry and analyze indel formation by tracking of indels by decomposition (TIDE) analysis.
We will then describe the process of using CRISPR/Cas9 together with a recombinant AAV6 vector (rAAV6, a donor template for homology-directed repair (HDR)) to mediate site-specific insertion of enhanced green fluorescent protein (EGFP) at the adeno-associated virus integration site 1 (AAVS1) gene. The AAVS1 gene is an active locus without known biological functions and an AAV viral integration site on the human genome; therefore, it is considered a &#8220;safe harbor&#8221; for genome engineering. Here, we report that expansion and activation of B cells allowed up to 44-fold expansion in 7 days of culture (Figure 1). Electroporation of B cells showed a slight reduction of overall cell health (Figure 2A) at 24 h post-transfection. Scatter plot analysis of the CD19 marker (Figure 2B) showed up to 83% reduction in the edited cells (Figure 2C).
TIDE analysis of the chromatographs (Figure 3A) revealed that the % indels was similar to the % protein loss by flow cytometry (Figure 3B). Flow cytometry analysis of the KI experiment showed that the cells that received AAV vector (Figure 4), together with RNP, expressed up to 64% EGFP-positive cells (Figure 5A) and later displayed successful integration by junction polymerase chain reaction (PCR) (Figure 5B). Cell counts showed that all samples quickly recovered within 3 days post-engineering (Figure 5C).

<table>
	<tbody>
		<tr>
			<td>Alt-R S.p. Cas9 Nuclease V3 protein, 500 ug</td>
			<td>IDT</td>
			<td>1081059</td>
			<td>smaller size is also available</td>
		</tr>
		<tr>
			<td>Amaxa P3 primary cell 4D- Nucleofector X Kit S (32 RCT)</td>
			<td>Lonza</td>
			<td>V4XP-3032</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium-chloride-potassium (ACK) lysing buffer</td>
			<td>Quality Biological</td>
			<td>118-156-101</td>
			<td></td>
		</tr>
		<tr>
			<td>CleanCap chemically modified Cas9 mRNA</td>
			<td>Trilink Biotechnology</td>
			<td>L-7206-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>CpG ODN 2006 (ODN 7909) 5 mg</td>
			<td>Invivogen</td>
			<td>TLRL-2006-5</td>
			<td>different sizes available</td>
		</tr>
		<tr>
			<td>Cryostor CS10, 100 mL</td>
			<td>STEMCELL Technology</td>
			<td>7930</td>
			<td></td>
		</tr>
		<tr>
			<td>CTS Immune Cell SR</td>
			<td>Thermo Fisher Scientific</td>
			<td>A2596101</td>
			<td></td>
		</tr>
		<tr>
			<td>EasySep human B cells isolation kit</td>
			<td>STEMCELL Technology</td>
			<td>17954</td>
			<td></td>
		</tr>
		<tr>
			<td>eBioscience fixable viability dye eFlour 780</td>
			<td>eBiosciences</td>
			<td>65-0865-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Excellerate B cell media, Xeno-free</td>
			<td>R&#38;D Systems</td>
			<td>CCM031</td>
			<td>B-cell basal medium</td>
		</tr>
		<tr>
			<td>Falcon 14 mL Polypropylene Round-bottom Tube</td>
			<td>Corning</td>
			<td>352059</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>R&#38;D Systems</td>
			<td>S11550</td>
			<td>For thawing B cells only</td>
		</tr>
		<tr>
			<td>Ficoll-Paque Plus</td>
			<td>GE Healthcare</td>
			<td>17-1440-03</td>
			<td></td>
		</tr>
		<tr>
			<td>GeneMate SnapStrip&#174; 8-Strip 0.2 mL PCR Tubes with Individual Attached Dome Caps</td>
			<td>BioExpress</td>
			<td>T-3035-1 / 490003-692</td>
			<td></td>
		</tr>
		<tr>
			<td>Hyclone 0.0067M PBS (No Ca, No Mg) or 1x PBS</td>
			<td>GE lifesciences</td>
			<td>SH30256.01</td>
			<td></td>
		</tr>
		<tr>
			<td>Lonza 4D Nucleofector core unit</td>
			<td>Lonza</td>
			<td>AAF-1002B</td>
			<td></td>
		</tr>
		<tr>
			<td>Lonza 4D Nucleofector X unit</td>
			<td>Lonza</td>
			<td>AAF-1002X</td>
			<td></td>
		</tr>
		<tr>
			<td>Mega CD40 Ligand</td>
			<td>Enzo Life Sciences</td>
			<td>ALX-522-110-C010</td>
			<td></td>
		</tr>
		<tr>
			<td>Mr. Frosty</td>
			<td>Sigma-Aldrich</td>
			<td>C1562-1EA</td>
			<td>For freezing cells</td>
		</tr>
		<tr>
			<td>Pen/Strep 100X</td>
			<td>Sigma-Aldrich</td>
			<td>TMS-AB2-C</td>
			<td></td>
		</tr>
		<tr>
			<td>PerCP anti-human CD19 clone HIB19</td>
			<td>biolegend</td>
			<td>302228</td>
			<td>smaller size is also available</td>
		</tr>
		<tr>
			<td>rAAV6 SA-GFP pakaging ( with our SA-GFP cassette see Figure 4.)</td>
			<td>Vigene Biosciences</td>
			<td>N/A</td>
			<td>large scale packaging, 1e13 GC/mL, 500 mL</td>
		</tr>
		<tr>
			<td>Recombinant human IL-10 protein 250 ug</td>
			<td>R&#38;D Systems</td>
			<td>217-IL-250</td>
			<td>different sizes available</td>
		</tr>
		<tr>
			<td>Recombinant human IL-15 protein 25 ug</td>
			<td>R&#38;D Systems</td>
			<td>247-ILB-025</td>
			<td>different sizes available</td>
		</tr>
		<tr>
			<td>The Big Easy EasySep Magnet</td>
			<td>STEMCELL Technology</td>
			<td>18001</td>
			<td>different sizes available</td>
		</tr>
		<tr>
			<td>Tris-EDTA (TE) buffer</td>
			<td>Fisher Scientific</td>
			<td>BP2476100</td>
			<td></td>
		</tr>
	</tbody>
</table>

genome engineering of primary human b cells using crispr/cas9

B cells are lymphocytes derived from hematopoietic stem cells and are a key component of the humoral arm of the adaptive immune system. They make attractive candidates for cell-based therapies because of their ease of isolation from peripheral blood, their ability to expand in vitro, and their longevity in vivo. Additionally, their normal biological function&#8212;to produce large amounts of antibodies&#8212;can be utilized to express very large amounts of a therapeutic protein, such as a recombinant antibody to fight infection, or an enzyme for the treatment of enzymopathies. Here, we provide detailed methods for isolating primary human B cells from peripheral blood mononuclear cells (PBMCs) and activating/expanding isolated B cells in vitro. We then demonstrate the steps involved in using the CRISPR/Cas9 system for site-specific KO of endogenous genes in B cells. This method allows for efficient KO of various genes, which can be used to study the biological functions of genes of interest. We then demonstrate the steps for using the CRISPR/Cas9 system together with a recombinant, adeno-associated, viral (rAAV) vector for efficient site-specific integration of a transgene expression cassette in B cells. Together, this protocol provides a step-by-step engineering platform that can be used in primary human B cells to study biological functions of genes as well as for the development of B-cell therapeutics.

The updated expansion and activation protocol enabled the rapid expansion of B cells up to 44-fold in 7 days (Figure 1; n =3 donors). In the KO experiment, the B-cell count using Trypan blue staining showed more than 80% viable cells with a slight reduction in cell recovery in both the control and the CD19 KO samples at 24 h post-electroporation (Figure 2A; p &#8805; 0.05, n = 3 donors). This result indicates that electroporation slightly affected overall B-cell...

Watch this Scientific Journal Video about Genome Engineering of Primary Human B Cells Using CRISPR/Cas9 at JoVE.com

Genome Engineering of Primary Human B Cells Using CRISPR/Cas9

Here we provide a detailed, step-by-step protocol for CRISPR/Cas9-based genome engineering of primary human B cells for gene knockout (KO) and knock-in (KI) to study biological functions of genes in B cells and the development of B-cell therapeutics.

B cells are lymphocytes derived from hematopoietic stem cells and are a key component of the humoral arm of the adaptive immune system. They make ...

This protocol allows researchers to precisely eliminate a gene in B cells to study the loss of function effects of that gene or to insert a trans gene for stable trans gene expression that can be used for research or therapeutic purposes. The main advantage of this method is that it provides a universal platform that makes it possible to easily and precisely engineer B cells with high efficiencies. This method can be used to engineer B cells to express recombinant antibodies or enzymes and then transfer those B cells to treat infections or in enzymopathies.To begin, thaw B cells in a 37 degree Celsius water bath. While waiting, transfer two milliliters of pre warmed FBS into a sterile, 15-milliliter conical tube. Once the B cells are completely thawed, immediately add one milliliter of pre-warmed FBS, drop-wise, into the sample.Incubate at room temperature for one minute. Gently pipette to resuspend the sample and transfer the whole volume, drop-wise, into a conical tube containing two milliliters of prewarmed FBS. Bring the volume to 15 milliliters with sterile PBS, then cap the tube and invert it gently two to three times.Centrifuge the sample at 400 times G for five minutes, then discard the supernatant without disturbing the cell pellet. Resuspend the pellet with one milliliter of pre-equilibrated B-cell expansion medium and count the cells. The total cell number should be approximately 10 to the seventh cells.Transfer the cells into a flask containing 20 milliliters of the pre-equilibrated B-cell expansion medium. The final concentration of the cells, should be approximately five times 10 to the fifth cells per milliliter. Incubate the flask vertically in a tissue culture incubator.Prepare the CRISPR/Cas9 transfecting substrate by mixing one microgram of chemically modified sgRNA with 1.5 micrograms of chemically modified streptococcus pyogenes Cas9 nucleus mRNA per transfection reaction. For control, add one microliter of TE buffer, instead of sgRNA, into a 0.2-milliliter tube of an eight tube strip. Turn on an electroporator and prepare the nuclear infection reagents.Count and transfer 1 million B cells per transfection reaction, into a sterile conical tube. Bring the volume to 15 milliliters with sterile PBS and centrifuge at 400 times G for five minutes. After centrifugation, discard the supernatant.Resuspend the cells with 10 milliliters of sterile PBS and centrifuge at 400 times G for five minutes, then discard the supernatant completely without disturbing the cell pellet. Add 0.5 micrograms of chemically modified GFP mRNA per 1 million B cells to the cell pellet. Resuspend the pellet with 20 microliters of primary cell transfection reagent per 1 million B cells and mix gently by pipetting five to six times.Transfer 20.5 microliters per transfection reaction into the 0.2-milliliter tubes containing CRISPR/Cas9 reagent. Pipette up and down once to mix and transfer the entire volume into a transfection cuvette. Cap and tap the cuvette on the bench gently to ensure that the liquid covers the bottom of the cuvette.Use the human primary B-cell protocol on the electroporator for transfection. Rest the electroporated cells in the cuvette at room temperature for 15 minutes. Then transfer 80 microliters of the pre-equilibrated B-cell expansion medium into the transfection reaction in the cuvette.Place the cuvette in the tissue culture incubator for 30 minutes. Gently pipe head a couple of times to mix and transfer the whole volume of the sample from the cuvette to an appropriate well of a 48-well tissue culture plate containing one milliliter of the B-cell expansion medium. The final concentration of the cells should be 1 million cells per milliliter.Performing a gene knock-in experiment, transfer recombinant adeno associated type-six viral vector at 500, 000 multiplicity of infection into the appropriate well containing electroporated cells. Place the plate in a tissue culture incubator at 37 degrees Celsius and 5%carbon dioxide with humidity. In the knockout experiment, the B-cell count showed more than 80%viable cells with a slight reduction in cell recovery in both the control and the CD19 knockout samples at 24 hours post electroporation.B cells were collected on day five post-transfection for flow cytometry and tide analysis. Representative scatterplots of the control and knockout samples showed 14 and 95%CD19 negative cells respectively, demonstrating a significant reduction in CD19 expression in the knockout samples. Chromatograms of genomic sequencing showed double peaks in the CD19 knockout B cells, indicating insertions or deletions of nucleotides post-CRISPR/Cas9 mediated double-stranded breaks.Indel analysis of the chromatographs of the knockout samples showed a high percent of indel formation at the CD19 locus, which is consistent with percent CD19 protein loss detected by flow cytometry. B cells from the knock-in experiment were collected on day 12, post engineering. Scatterplots showed 64%of EGFP positive cells in the sample that received the recombinant adeno associated type-six viral vector, together with RNP, whereas none or minimal EGFP positivity was observed in the control and vector-only samples respectively.A junction PCR amplification, showed 1.5 kilobase pair amplicons in the knock-in sample and no PCR product was observed in either the control or vector-only sample. Cell counts showed that the engineering process affects cell recovery in the knock-in sample more than the control or the vector-only samples. However, all samples quickly rebounded within three days after engineering.This procedure can also be used to introduce base editor agents to alter single base pairs in order to induce or correct single point mutations in the B-cell genome. It could also be used to introduce premature stop codons or to alter splice sites, allowing for multiple gene knockouts without the risk of chromosomal translocations. Before this technique was developed, engineering human B cells would inquire the use of other more challenging gene engineering approaches.This technique is an easier, less expensive and quicker alternative. It could also potentially be used to synthesize cell therapy products for clinical use.

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