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	<li>Ruscetti, F. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+effector+mechanisms+against+HTLV-I-+and+HTLV-III/LAV-infected+lymphoid+cells.">Analysis of effector mechanisms against HTLV-I- and HTLV-III/LAV-infected lymphoid cells.</a> J Immunol. 136, 3619-3624 (1986).</li><li>Zheng, Z. Y., Zucker-Franklin, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apparent+ineffectiveness+of+natural+killer+cells+vis-a-vis+retrovirus-infected+targets.">Apparent ineffectiveness of natural killer cells vis-a-vis retrovirus-infected targets.</a> J Immunol. 148, 3679-3685 (1992).</li><li>Ferrari, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clade+B-based+HIV-1+vaccines+elicit+cross-clade+cytotoxic+T+lymphocyte+reactivities+in+uninfected+volunteers.">Clade B-based HIV-1 vaccines elicit cross-clade cytotoxic T lymphocyte reactivities in uninfected volunteers.</a> Proc Natl Acad Sci U S A. 94, 1396-1401 (1997).</li><li>Shankar, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impaired+function+of+circulating+HIV-specific+CD8(+)+T+cells+in+chronic+human+immunodeficiency+virus+infection.">Impaired function of circulating HIV-specific CD8(+) T cells in chronic human immunodeficiency virus infection.</a> Blood. 96, 3094-3101 (2000).</li><li>Ward, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HIV-1+Vpr+triggers+natural+killer+cell-mediated+lysis+of+infected+cells+through+activation+of+the+ATR-mediated+DNA+damage+response.">HIV-1 Vpr triggers natural killer cell-mediated lysis of infected cells through activation of the ATR-mediated DNA damage response.</a> PLoS Pathog. 5, e1000613-e1000613 (2009).</li><li>Ward, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HIV+modulates+the+expression+of+ligands+important+in+triggering+natural+killer+cell+cytotoxic+responses+on+infected+primary+T-cell+blasts.">HIV modulates the expression of ligands important in triggering natural killer cell cytotoxic responses on infected primary T-cell blasts.</a> Blood. 110, 1207-1214 (2007).</li><li>Bonaparte, M. I., Barker, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Killing+of+human+immunodeficiency+virus-infected+primary+T-cell+blasts+by+autologous+natural+killer+cells+is+dependent+on+the+ability+of+the+virus+to+alter+the+expression+of+major+histocompatibility+complex+class+I+molecules.">Killing of human immunodeficiency virus-infected primary T-cell blasts by autologous natural killer cells is dependent on the ability of the virus to alter the expression of major histocompatibility complex class I molecules.</a> Blood. 104, 2087-2094 (2004).</li><li>Stinchcombe, J. C., Griffiths, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Secretory+mechanisms+in+cell-mediated+cytotoxicity.">Secretory mechanisms in cell-mediated cytotoxicity.</a> Annu Rev Cell Dev Biol. 23, 495-517 (2007).</li><li>O'Doherty, U., Swiggard, W. J., Malim, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+immunodeficiency+virus+type+1+spinoculation+enhances+infection+through+virus+binding.">Human immunodeficiency virus type 1 spinoculation enhances infection through virus binding.</a> J Virol. 74, 10074-10080 (2000).</li><li>Alter, G., Malenfant, J. M., Altfeld, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CD107a+as+a+functional+marker+for+the+identification+of+natural+killer+cell+activity.">CD107a as a functional marker for the identification of natural killer cell activity.</a> J Immunol Methods. 294, 15-22 (2004).</li><li>Fogli, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lysis+of+endogenously+infected+CD4++T+cell+blasts+by+rIL-2+activated+autologous+natural+killer+cells+from+HIV-infected+viremic+individuals.">Lysis of endogenously infected CD4+ T cell blasts by rIL-2 activated autologous natural killer cells from HIV-infected viremic individuals.</a> PLoS Pathog. 4, e1000101-e1000101 (2008).</li><li>Tomescu, C., Chehimi, J., Maino, V. C., Montaner, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NK+cell+lysis+of+HIV-1-infected+autologous+CD4+primary+T+cells:+requirement+for+IFN-mediated+NK+activation+by+plasmacytoid+dendritic+cells.">NK cell lysis of HIV-1-infected autologous CD4 primary T cells: requirement for IFN-mediated NK activation by plasmacytoid dendritic cells.</a> J Immunol. 179, 2097-2104 (2007).</li><li>Ward, J. P., Bonaparte, M. I., Barker, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HLA-C+and+HLA-E+reduce+antibody-dependent+natural+killer+cell-mediated+cytotoxicity+of+HIV-infected+primary+T+cell+blasts.">HLA-C and HLA-E reduce antibody-dependent natural killer cell-mediated cytotoxicity of HIV-infected primary T cell blasts.</a> Aids. 18, 1769-1779 (2004).</li></ol>

No conflicts of interest declared.

When done correctly the assays described in this protocol should provide a representative picture of NK cells ability to degranulate against and lyse HIV-1 infected cells (see Figure 5). NK cell degranulation in response to HIV-infected cells and the NK cells lysis HIV-infected cells should be directly proportional10. Reliable results for the two NK cell functional assays to measure cytotoxic responses to HIV-infected cells are dependant on the isolation of highly purified NK cells as well as a highly purified population of infected cells. Having purified NK cells and HIV-1 infected cells are critical for the achievement of a fairly accurate effector to target cell ratio. Similarly, removal of dead and apoptotic cells from the target cell populations is important before 51Cr labeling or incubation with the effector cells. 51Cr may be internalized by cells that are undergoing apoptosis as the presence of dead or apoptotic cells during the isotope labeling step will result in a high spontaneous release and will distort the calculated % specific lysis. Moreover, the presence of dead or apoptotic cells may trigger NK cell degranulation resulting in abnormally high levels of CD107a expression. Precise pipetting is necessary when removing the cell-free supernatants following the incubation of NK cells and target cells in the 51Cr release assays, as differences in the volume of supernatant removed from each replicate well will result in high standard deviations. Modifications can be made to these protocols to evaluate the role of specific NK receptors in triggering NK cells lysis of HIV-infected cells by incubating the effectors or targets prior to co-culture with antagonistic antibodies to specific receptors or ligands 6,11. Cytokine-treated NK cells (e.g., IL-2, IL-15) can be used to evaluate the functionality of stimulated NK cells 12. Similarly, antibody dependant cell cytotoxicity assays may be performed using these protocols. Anti-HIV antibodies (e.g., anti-gp120) can be added to the target cells for recognition by the NK cell low affinity Fc receptor CD16 13. These assays, although set up to measure NK cell cytotoxic responses to HIV-infected cells, can also be modified to measure the ability of NK cells to produce cytokines following HIV-infected cell recognition. Although we described in this protocol the use of in vitro infected cells as target cells we have recently described the generation of target cells from patients infected with HIV. This requires the isolation of CD4+ T-cells followed by expansion of the cells over a two week period following stimulation with mitogens in the presence of interleukin-2 11. After the two week period of expansion, the protocols described in this article are used to isolate the target cells.

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		<div>
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		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Vaccutainer Tubes (Sodium Heparin)</td>
<td>&nbsp;</td>
<td>Becton Dickenson</td>
<td>367874</td>
<td>&nbsp;</td>
<tr>
<td>RosetteSep CD4+ T-cell Isolation Kit</td>
<td>&nbsp;</td>
<td>StemCell Technologies</td>
<td>15062</td>
<td>&nbsp;</td>
<tr>
<td>CMF PBS</td>
<td>&nbsp;</td>
<td>Hyclone</td>
<td>SH30256.01</td>
<td>&nbsp;</td>
<tr>
<td>FBS</td>
<td>&nbsp;</td>
<td>Hyclone</td>
<td>10437-028</td>
<td>&nbsp;</td>
<tr>
<td>Lymphocyte Separation Medium</td>
<td>&nbsp;</td>
<td>Cellgro</td>
<td>25-072-CV</td>
<td>&nbsp;</td>
<tr>
<td>RPMI-1640</td>
<td>&nbsp;</td>
<td>Hyclone</td>
<td>SH30096.01 </td>
<td>&nbsp;</td>
<tr>
<td>Penicillin / Streptomycin</td>
<td>&nbsp;</td>
<td>Hyclone</td>
<td>SV30010</td>
<td>&nbsp;</td>
<tr>
<td>L-glutamine</td>
<td>&nbsp;</td>
<td>Cellgro</td>
<td>25-005-Cl</td>
<td>&nbsp;</td>
<tr>
<td>T-cell Expansion Kit</td>
<td>&nbsp;</td>
<td>Miltenyi Biotec</td>
<td>130-091-441</td>
<td>&nbsp;</td>
<tr>
<td>CMF HBSS (1x)</td>
<td>&nbsp;</td>
<td>Hyclone</td>
<td>SH30588.01</td>
<td>&nbsp;</td>
<tr>
<td>0.5M EDTA</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>46-034-Cl</td>
<td>&nbsp;</td>
<tr>
<td>NK Cell Negative Isolation Kit</td>
<td>&nbsp;</td>
<td>Miltenyi Biotec</td>
<td>130-092-657</td>
<td>&nbsp;</td>
<tr>
<td>IMDM</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>12440-046</td>
<td>&nbsp;</td>
<tr>
<td>CD4+ Positive Isolation Kit</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>113.31D</td>
<td>&nbsp;</td>
<tr>
<td>Dead Cell Removal Kit</td>
<td>&nbsp;</td>
<td>Miltenyi Biotec</td>
<td>130-090-101</td>
<td>&nbsp;</td>
<tr>
<td>Polybrene</td>
<td>&nbsp;</td>
<td>Santa Cruz</td>
<td>sc-134220</td>
<td>&nbsp;</td>
<tr>
<td>CD3 PacificBlue</td>
<td>&nbsp;</td>
<td>Becton Dickenson</td>
<td>558117</td>
<td>&nbsp;</td>
<tr>
<td>CD14 PacificBlue</td>
<td>&nbsp;</td>
<td>Biolegend</td>
<td>325616</td>
<td>&nbsp;</td>
<tr>
<td>CD20 PacificBlue</td>
<td>&nbsp;</td>
<td>Biolegend</td>
<td>302328</td>
<td>&nbsp;</td>
<tr>
<td>CD56 APC</td>
<td>&nbsp;</td>
<td>Biolegend</td>
<td>318310</td>
<td>&nbsp;</td>
<tr>
<td>CD69 PE</td>
<td>&nbsp;</td>
<td>Becton Dickenson</td>
<td>555531</td>
<td>&nbsp;</td>
<tr>
<td>CD107a FITC</td>
<td>&nbsp;</td>
<td>Becton Dickenson</td>
<td>555800</td>
<td>&nbsp;</td>
<tr>
<td>51Chromium</td>
<td>&nbsp;</td>
<td>Perkin Elmer</td>
<td>NEZ030002MC</td>
<td>&nbsp;</td>
<tr>
<td>Gamma Counter Tubes</td>
<td>&nbsp;</td>
<td>Perkin Elmer</td>
<td>1270-401</td>
<td>&nbsp;</td>
<tr>
<td>2470 Automatic Gamma Counter</td>
<td>&nbsp;</td>
<td>Perkin Elmer</td>
<td>2470-0050</td>
<td>&nbsp;</td>
<tr>
<td>FACS Diva</td>
<td>&nbsp;</td>
<td>Beckton Dickenson</td>
<td>643629</td>
<td>&nbsp;</td>
<tr>
<td>FlowJo</td>
<td>&nbsp;</td>
<td>TreeStar</td>
<td>FJ-9-1YR</td>
<td>&nbsp;</td>		</tbody>
		</table>
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preparation and use of hiv-1 infected primary cd4+ t-cells as target cells in natural killer cell cytotoxic assays

Natural killer (NK) cells are a vital component of the innate immune response to virus-infected cells. It is important to understand the ability of NK cells to recognize and lyse HIV-1 infected cells because identifying any aberrancy in NK cell function against HIV-infected cells could potentially lead to therapies that would enhance their cytolytic activity. There is a need to use HIV-infected primary T-cell blasts as target cells rather then infected-T-cell lines in the cytotoxicity assays. T-cell lines, even without infection, are quite susceptible to NK cell lysis. Furthermore, it is necessary to use autologous primary cells to prevent major histocompatibility complex class I mismatches between the target and effector cell that will result in lysis. Early studies evaluating NK cell cytolytic responses to primary HIV-infected cells failed to show significant killing of the infected cells 1,2. However, using HIV-1 infected primary T-cells as target cells in NK cell functional assays has been difficult due the presence of contaminating uninfected cells 3. This inconsistent infected cell to uninfected cell ratio will result in variation in NK cell killing between samples that may not be due to variability in donor NK cell function. Thus, it would be beneficial to work with a purified infected cell population in order to standardize the effector to target cell ratios between experiments 3,4. Here we demonstrate the isolation of a highly purified population of HIV-1 infected cells by taking advantage of HIV-1's ability to down-modulate CD4 on infected cells and the availability of commercial kits to remove dead or dying cells 3-6. The purified infected primary T-cell blasts can then be used as targets in either a degranulation or cytotoxic assay with purified NK cells as the effector population 5-7. Use of NK cells as effectors in a degranulation assay evaluates the ability of an NK cell to release the lytic contents of specialized lysosomes 8 called "cytolytic granules". By staining with a fluorochrome conjugated antibody against CD107a, a lysosomal membrane protein that becomes expressed on the NK cell surface when the cytolytic granules fuse to the plasma membrane, we can determine what percentage of NK cells degranulate in response to target cell recognition. Alternatively, NK cell lytic activity can be evaluated in a cytotoxic assay that allows for the determination of the percentage of target cells lysed by release of 51Cr from within the target cell in the presence of NK cells.

Watch this Scientific Journal Video about Preparation and Use of HIV-1 Infected Primary CD4+ T-Cells as Target Cells in Natural Killer Cell Cytotoxic Assays at JoVE.com

Preparation and Use of HIV-1 Infected Primary CD4+ T-Cells as Target Cells in Natural Killer Cell Cytotoxic Assays

Cytotoxicity assays to measure natural killer cell lytic responses to HIV-infected cells is limited by the purity of the target cells. We demonstrate here the isolation of a highly purified population of HIV-1 infected primary T-cell blasts by taking advantage of HIV-1 s ability to down-modulate CD4.

 Natural killer (NK) cells are a vital component of the innate immune response to virus-infected cells. It is important to understand the ability of NK ...

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Immunology and Infection

25.8K Views.  Rush University Medical Center. Cytotoxicity assays to measure natural killer cell lytic responses to HIV-infected cells is limited by the purity of the target cells. We demonstrate here the isolation of a highly purified population of HIV-1 infected primary T-cell blasts by taking advantage of HIV-1 s ability to down-modulate CD4.