This work was supported by Project Grants #1010395 (BQ and CP) and #525431 (CR), and a Program Grant #455395 (CP) from the National Health and Medical Research Council of Australia, an Australian Centre for Hepatitis and HIV Virology EOI 2012 grant (CR and RJJ) and a grant from the Gordon and Gretel Bootes Foundation (BQ and CR). We wish to thank Harpreet Vohra and Michael Devoy for their excellent maintenance of the JCSMR FACS laboratory, the Australian Cancer Research Foundation Biomolecular Resource Facility, JCSMR, ANU, for peptide synthesis, and Dr. David Boyle, CSIRO Animal Health Laboratories, Geelong, Australia for providing the parent HIV vaccine stocks.

Note: Mice used under this protocol were handled according to the guidelines of the Australian National University Animal Experimentation Ethics Committee and mice were euthanized by cervical dislocation.
1. Dye and Peptide Preparation
<ol>
	<li>Dye preparation 
	Note: Dyes are prediluted at different concentrations to allow labeling of cells at discrete fluorescence intensities. CFSE is used at seven concentrations made through 3.5-fold serial dilutions, and CTV and CPD are used at six...

<ol>
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The advantage of FTA-based assays is that they allow the discrimination of &#62;250 viable and fully functional target cell populations from a single host animal by flow cytometry. This provides a level of complexity to in vivo flow cytometry based assays that has not been possible before. This is highlighted in the 2 animal experiments shown above, where responses to 7 distinct viral epitopes at 6 concentrations could be monitored in replicates of 6 simultaneously in a single animal allowing parameters such as ...

T cells play a central role in the adaptive immune response and are often targeted for manipulation in immunotherapy. CD4+ effector T cells respond to foreign antigen by secreting cytokines that regulate many aspects of immunity and can also directly help B cells to manufacture antibodies. CD8+ cytotoxic T cells (CTLs) can also respond to foreign antigen by secreting cytokines as well as playing a central role in directly killing cells expressing a foreign antigen. The fundamental interaction that initiates these T cell effector functions involves the interaction of the T cell receptor (TCR) with foreign peptides displayed on MHC molecules on the surface of cells. CD4+ T cells recognize peptides displayed on MHC class-II molecules on antigen presenting cells and CD8+ T cells recognize peptides displayed on MHC class-I molecules that are typically displayed on microbe infected cells.
In order to assess the role T cells play in an immune response, it is essential that their effector functions are measured by reliable and sensitive techniques. Common methods for T cell response assessment include; MHC class-I/II/peptide tetramer reactivity; cytokine production by ELISPOT and intracellular cytokine staining; and killing capacity by 51Cr-release assays. These assays, however, are typically performed ex vivo with in vitro stimulation, or provide limited insight into T cell function. Ideally, when measuring T cell responses it would be beneficial to assess them in situ, in vivo as they occur, with no manipulation of T cells so as to avoid changes in functional parameters that may occur through in vitro stimulation. Some of the most commonly used in vivo T cell functional assays are based on measuring CTL mediated killing of target cells pulsed with MHC class I-binding peptides, that are enumerated in vivo via their detection through fluorescent labeling with vital dyes such as CFSE. While these types of assays can monitor CTL mediated killing of targets when they happen in vivo, they have previously had a relatively limited capacity to assess killing of multiple targets presenting different concentrations and different types of peptide epitopes, which is required to allow qualitative parameters such as functional avidity and epitope variant cross-reactivity to be assessed. These assays also do not provide any information on CD4+ T cell mediated responses.
To overcome many of the limitations with current methods used to assess T cell responses, we have recently developed a multiplex assay based on fluorescent target arrays (FTAs), which allows the monitoring of T cell responses against &#62;250 target cells simultaneously in one animal by flow cytometry 1,2. FTAs are comprised of lymphocytes labeled with several concentrations and combinations of vital dyes like CFSE, CTV and CPD allowing &#62;250 cell clusters of unique fluorescence to be generated. Since these cells remain viable and fully functional, they can be injected into animals to allow monitoring of their interaction with effector T cells in vivo3. For example, the FTA cell clusters can be pulsed with MHC class-I-binding peptides to allow assessment of antigen-specific CTL mediated killing of target cells1. In addition, the FTA cell clusters can also be pulsed with MHC class-II-binding peptides, allowing assessment of antigen specific T helper cell (TH) activity by assessing activation (by assessment of activation markers such as CD69, CD44 and/or CD62L) of B cells within the FTA bearing cognate peptide2. Since more than 250 targets can be detected simultaneously, it is possible to measure CTL and TH responses against many target cell clusters pulsed with numerous peptides at different concentrations and the inclusion of many replicates. The FTA assay therefore provides an unprecedented level of T cell effector response assessment in vivo.
Here we describe in detail the construction of a FTA and show how they can be applied to assessing T cell responses in vivo. The procedure describes the construction of a FTA comprised of 252 discernable cell clusters through the use of three vital dyes, comprised of 6 repeats of 42 cell clusters pulsed with MHC class-I and II-binding peptides. The labeling of 42 cell clusters occurs in 10 ml conical bottomed tubes and it is helpful to lay these out in a tube rack as depicted in Table 1. This method can be adjusted for smaller numbers of discernable clusters as required by reducing the amount of labeling of each dye performed1.
We highlight the utility of the assay by showing how it can measure responses generated by recombinant pox -virus vaccination against multiple epitopes in a small cohort of mice. This shows how the FTA assay can be used to measure cumulative responses and functional avidity through, respectively, the use of area under curve (AUC) assessments and measurement of effective peptide concentration required to generate half maximal responses (EC50).

<table border="0" cellpadding="0" cellspacing="0" width="573">
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		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">RPMI</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">R8758</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Fetal calf serum</td>
			<td style="width:71px;">Serana</td>
			<td style="width:119px;">FCS-500</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">CTV</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">C34557</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">CFDA, SE</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">C1157</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">CPD</td>
			<td style="width:71px;">eBioscience</td>
			<td style="width:119px;">65-0840-90</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">anti-B220 PerCp-Cy5.5</td>
			<td style="width:71px;">eBioscience</td>
			<td style="width:119px;">110730</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">anti-CD69 brilliant violet 605</td>
			<td style="width:71px;">Biolegend</td>
			<td style="width:119px;">104529</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">PKH-26</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">PKH26GL-1KT</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;"></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;">EQUIPMENT:</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Material Name</td>
			<td style="width:71px;">Company</td>
			<td style="width:119px;">Catalogue Number</td>
			<td style="width:167px;">Comments (optional)</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Vortex</td>
			<td style="width:71px;">Scientific Industries Inc&#160;</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Centrifuge</td>
			<td style="width:71px;">Eppendorf</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Flow cytometer (Fortessa or equivalent with blue, red and violet laser source)</td>
			<td style="width:71px;">BD Bioscience</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
	</tbody>
</table>

the use of fluorescent target arrays for assessment of t cell responses in vivo

The ability to monitor T cell responses in vivo is important for the development of our understanding of the immune response and the design of immunotherapies. Here we describe the use of fluorescent target array (FTA) technology, which utilizes vital dyes such as carboxyfluorescein succinimidyl ester (CFSE), violet laser excitable dyes (CellTrace Violet: CTV) and red laser excitable dyes (Cell Proliferation Dye eFluor 670: CPD) to combinatorially label mouse lymphocytes into &#62;250 discernable fluorescent cell clusters. Cell clusters within these FTAs can be pulsed with major histocompatibility (MHC) class-I and MHC class-II binding peptides and thereby act as target cells for CD8+ and CD4+ T cells, respectively. These FTA cells remain viable and fully functional, and can therefore be administered into mice to allow assessment of CD8+ T cell-mediated killing of FTA target cells and CD4+ T cell-meditated help of FTA B cell target cells in real time in vivo by flow cytometry. Since &#62;250 target cells can be assessed at once, the technique allows the monitoring of T cell responses against several antigen epitopes at several concentrations and in multiple replicates. As such, the technique can measure T cell responses at both a quantitative (e.g.&#160;the cumulative magnitude of the response) and a qualitative (e.g.&#160;functional avidity and epitope-cross reactivity of the response) level. Herein, we describe how these FTAs are constructed and give an example of how they can be applied to assess T cell responses induced by a recombinant pox virus vaccine.

As an example of the use of the FTA assay, a BALB/c mouse was immunized with recombinant vaccinia virus (VV) expressing HIV-I epitopes (VV-HIV) and responses to the HIV-I CTL epitopes, Gag, Gag mut, Env and Pol, the VV CTL epitopes F2L and F2L mut, and the HIV-I TH cell epitope, Gag Th (as described in2) were assessed using a 252 parameter FTA assay (Figure 1B). Epitope variants of Gag (Gag mut) and F2L (F2L mut) are not expressed in the VV-HIV vector and therefore responses against...

Watch this Scientific Journal Video about The Use of Fluorescent Target Arrays for Assessment of T Cell Responses In vivo at JoVE.com

The Use of Fluorescent Target Arrays for Assessment of T Cell Responses In vivo

The ability to monitor T cell responses in detail in vivo is important for the development of our understanding of the immune response. Here we describe the use of fluorescent target arrays (FTAs) in an in vivo T cell assay that assesses &#62;250 parameters simultaneously by flow cytometry.

The Use of Fluorescent Target Arrays for Assessment of T Cell Responses In vivo

The ability to monitor T cell responses in vivo is important for the development of our understanding of the immune response and the design of ...

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Immunology and Infection

14.3K visualizações.  Australian National University.  A capacidade de monitorar as respostas das células T em detalhe, in vivo é importante para o desenvolvimento da nossa compreensão da resposta imune. Aqui nós descrevemos o uso de matrizes alvo fluorescentes (ACL) em um ensaio in vivo de células T em que avalia> 250 parâmetros simultaneamente por citometria de fluxo. 