The authors thank S. Prettin for expert technical assistance. This work was supported by a grant of the Helmholtz Association of German Research Centers (HGF) that was provided as part of the Helmholtz Alliance &#39;&#39;Immunotherapy of Cancers&#34; (HCC_WP2b).

<ol>
	<li>Amon, L., Hatscher, L., Heger, L., Dudziak, D., Lehmann, C. H. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Harnessing+the+complete+repertoire+of+conventional+dendritic+cell+functions+for+cancer+immunotherapy.">Harnessing the complete repertoire of conventional dendritic cell functions for cancer immunotherapy.</a> Pharmaceutics. 12 (7), 12070663 (2020).</li><li>Banchereau, 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=Immunobiology+of+dendritic+cells.">Immunobiology of dendritic cells.</a> Annual Review of Immunology. 18, 767-811 (2000).</li><li>Wculek, S. K., 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=Dendritic+cells+in+cancer+immunology+and+immunotherapy.">Dendritic cells in cancer immunology and immunotherapy.</a> Nature Reviews: Immunology. 20 (1), 7-24 (2020).</li><li>Kastenmuller, W., Kastenmuller, K., Kurts, C., Seder, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendritic+cell-targeted+vaccines--hope+or+hype.">Dendritic cell-targeted vaccines--hope or hype.</a> Nature Reviews: Immunology. 14 (10), 705-711 (2014).</li><li>Bonifaz, L. C., 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=In+vivo+targeting+of+antigens+to+maturing+dendritic+cells+via+the+DEC-205+receptor+improves+T+cell+vaccination.">In vivo targeting of antigens to maturing dendritic cells via the DEC-205 receptor improves T cell vaccination.</a> Journal of Experimental Medicine. 199 (6), 815-824 (2004).</li><li>Boscardin, S. B., 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=Antigen+targeting+to+dendritic+cells+elicits+long-lived+T+cell+help+for+antibody+responses.">Antigen targeting to dendritic cells elicits long-lived T cell help for antibody responses.</a> Journal of Experimental Medicine. 203 (3), 599-606 (2006).</li><li>Hossain, M. K., Wall, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+Dendritic+Cell+Receptors+as+Targets+for+Enhancing+Anti-Cancer+Immune+Responses.">Use of Dendritic Cell Receptors as Targets for Enhancing Anti-Cancer Immune Responses.</a> Cancers. 11 (3), 11030418 (2019).</li><li>Johnson, T. 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=Inhibition+of+melanoma+growth+by+targeting+of+antigen+to+dendritic+cells+via+an+anti-DEC-205+single-chain+fragment+variable+molecule.">Inhibition of melanoma growth by targeting of antigen to dendritic cells via an anti-DEC-205 single-chain fragment variable molecule.</a> Clinical Cancer Research. 14 (24), 8169-8177 (2008).</li><li>Trumpfheller, C., 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=The+microbial+mimic+poly+IC+induces+durable+and+protective+CD4++T+cell+immunity+together+with+a+dendritic+cell+targeted+vaccine.">The microbial mimic poly IC induces durable and protective CD4+ T cell immunity together with a dendritic cell targeted vaccine.</a> Proceedings of the National Academy of Sciences of the United States of America. 105 (7), 2574-2579 (2008).</li><li>Idoyaga, 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=Comparable+T+helper+1+(Th1)+and+CD8+T-cell+immunity+by+targeting+HIV+gag+p24+to+CD8+dendritic+cells+within+antibodies+to+Langerin,+DEC205,+and+Clec9A.">Comparable T helper 1 (Th1) and CD8 T-cell immunity by targeting HIV gag p24 to CD8 dendritic cells within antibodies to Langerin, DEC205, and Clec9A.</a> Proceedings of the National Academy of Sciences of the United States of America. 108 (6), 2384-2389 (2011).</li><li>Sancho, D., 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=Tumor+therapy+in+mice+via+antigen+targeting+to+a+novel,+DC-restricted+C-type+lectin.">Tumor therapy in mice via antigen targeting to a novel, DC-restricted C-type lectin.</a> Journal of Clinical Investigation. 118 (6), 2098-2110 (2008).</li><li>Volckmar, 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=Targeted+antigen+delivery+to+dendritic+cells+elicits+robust+antiviral+T+cell-mediated+immunity+in+the+liver.">Targeted antigen delivery to dendritic cells elicits robust antiviral T cell-mediated immunity in the liver.</a> Scientific Reports. 7, 43985 (2017).</li><li>Kraal, G., Breel, M., Janse, M., Bruin, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Langerhans'+cells,+veiled+cells,+and+interdigitating+cells+in+the+mouse+recognized+by+a+monoclonal+antibody.">Langerhans' cells, veiled cells, and interdigitating cells in the mouse recognized by a monoclonal antibody.</a> Journal of Experimental Medicine. 163 (4), 981-997 (1986).</li><li>Volckmar, 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=The+STING+activator+c-di-AMP+exerts+superior+adjuvant+properties+than+the+formulation+poly(I:C)/CpG+after+subcutaneous+vaccination+with+soluble+protein+antigen+or+DEC-205-mediated+antigen+targeting+to+dendritic+cells.">The STING activator c-di-AMP exerts superior adjuvant properties than the formulation poly(I:C)/CpG after subcutaneous vaccination with soluble protein antigen or DEC-205-mediated antigen targeting to dendritic cells.</a> Vaccine. 37 (35), 4963-4974 (2019).</li></ol>

The authors have nothing to disclose.

Chemical conjugation of an endocytosis receptor-specific antibody and a protein antigen provides an efficient and, importantly, also flexible approach for in vivo DC targeting in pre-clinical mouse models. With our protocol we provide an efficient approach for the successful conjugation of the model antigen OVA to a DEC-205-specific IgG antibody.
In our protocol, &#945;DEC-205 is purified from a hybridoma cellline and in the past, we have purified the antibody using protein G sepharos...

Dendritic cells (DC) are central players of the immune system. They are a diverse group of cells specialized in antigen-presentation and their major function is to bridge innate and adaptive immunity1,2. Importantly, DC not only play an important role in efficient and specific pathogen-directed responses but are also involved in many aspects of antitumor immunity1,3.
Due to their exclusive role in host immunity, DC came into focus as target cells for vaccination4. One approach is to target antigens to DC in vivo to induce antigen-specific immune responses and over the last years, a large number of studies have been dedicated to defining suitable receptors and targeting strategies1,4. One example is the C-type lectin receptor DEC-205, which can be targeted by DEC-205-specific antibodies to induce endocytosis. Importantly, DEC-205 targeting in the combination with suitable adjuvants has been shown to efficiently induce long-lived and protective CD4+ and CD8+ T cells, as well as antibody responses, also against tumor antigens3,5,6,7,8,9.
There are a number of studies showing conjugated antigens targeted to DC to be superior to free un-conjugated antigen3,5,10,11,12. This makes the conjugation of the antigen to the respective DC targeting moiety a central step in DC targeting approaches. In the case of DC targeting via antibodies or antibody fragments, antigens can be either chemically or genetically linked and either strategy provides its own (dis)advantages1. On the one hand, in genetically engineered antibody-antigen constructs there is a control over the antigen dose as well as the location providing superior comparability between lots1. At the same time however, chemical conjugation needs less preparation and provides more flexibility especially when attempting to test and compare different antigens and/or vaccination strategies in experimental and pre-clinical models.
Here, we present a protocol for the efficient and reliable chemical conjugation of ovalbumin (OVA) as a model protein antigen to a DEC-205-specific IgG2a antibody (&#945;DEC-205) suitable for in vivo DC targeting in mice. First, &#945;DEC-205 is purified from&#160;NLDC-145 hybridoma cells13. For chemical conjugation, the heterobifunctional crosslinker sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate (sulfo-SMCC), which contains NHS (N-hydroxysuccinimide) ester and maleimide groups, is used, allowing covalent conjugation of amine- and sulfhydryl-containing molecules. Specifically, the primary amines of the antibody initially react with sulfo-SMCC and the resulting maleimide-activated &#945;DEC-205 then reacts with the sulfhydryl-containing OVA protein reduced through TCEP-HCl (Tris(2-carboxyethyl) phosphine hydrochloride). The final product is chemically conjugated &#945;DEC-205/OVA (Figure 1). Beyond chemical conjugation itself, our protocol describes removal of excess OVA from the conjugate&#160;as well as the verification of successful conjugation through western blot analysis and a specific enzyme-linked immunosorbent assay. We have successfully employed this approach in the past to chemically conjugate OVA and other proteins or immunogenic peptides to &#945;DEC-205. We demonstrate efficient binding to CD11c+ cells in vitro as well as the efficient induction of cellular and humoral immunity in vivo.
Certainly, there are drawbacks to this method such as in lot-to-lot comparability and in the exact dosing of the antigen within the final conjugate. Nevertheless, chemical conjugation provides experimental flexibility in the choice of the antibody and the protein antigen as compared to genetically engineered constructs. Therefore, we believe this approach is especially valuable in evaluating different antigens for their efficiency in DC targeting in pre-clinical mouse models, importantly also in the context of specific antitumor immune responses.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>antibody buffer 2 %</td>
			<td></td>
			<td></td>
			<td>2 % (w/v) Slim-Fast Chocolate powder in TBS-T</td>
		</tr>
		<tr>
			<td>antibody buffer 5 %</td>
			<td></td>
			<td></td>
			<td>5 % milk powder (w/v) in TBS-T</td>
		</tr>
		<tr>
			<td>blocking buffer (ELISA)</td>
			<td></td>
			<td></td>
			<td>10 % FBS in PBS</td>
		</tr>
		<tr>
			<td>blocking buffer 4 %</td>
			<td></td>
			<td></td>
			<td>4 % (w/v) Slim-Fast Chocolate powder in TBS-T</td>
		</tr>
		<tr>
			<td>blocking buffer 10 %</td>
			<td></td>
			<td></td>
			<td>10 % milk powder (w/v) in TBS-T</td>
		</tr>
		<tr>
			<td>cell culture flask T25</td>
			<td>Greiner Bio-One</td>
			<td>690175</td>
			<td>we use standard CELLSTAR filter cap cell culture flasks; alternatively use suspension culture flask (690195 )</td>
		</tr>
		<tr>
			<td>cell culture flask T75</td>
			<td>Greiner Bio-One</td>
			<td>658175</td>
			<td>we use standard CELLSTAR&#160; filter cap cell culture flasks; alternatively use suspension culture flask (658195)&#160;</td>
		</tr>
		<tr>
			<td>cell culture flask T175</td>
			<td>Greiner Bio-One</td>
			<td>661175</td>
			<td>we use standard CELLSTAR filter cap cell culture flasks; alternatively use suspension culture flask (661195)</td>
		</tr>
		<tr>
			<td>centrifugal concentrator MWCO 10 kDa</td>
			<td>Sartorius</td>
			<td>VS2001</td>
			<td>Vivaspin 20 centrifugal concentrator</td>
		</tr>
		<tr>
			<td>centrifugal protein concentrator MWCO 100 kDa, 5 - 20 ml</td>
			<td>Thermo Fisher Scientific</td>
			<td>88532</td>
			<td>Pierce Protein Concentrator, PES 5 -20 ml; we use the Pierce Concentrator 150K MWCO 20mL (catalog number 89921), which is however no longer available&#160;</td>
		</tr>
		<tr>
			<td>centrifuge bottles</td>
			<td>Nalgene</td>
			<td>525-2314</td>
			<td>PPCO (polypropylene copolymer) with PP (polypropylene) screw closure, 500 ml; obtained from VWR, Germany</td>
		</tr>
		<tr>
			<td>coating buffer (ELISA)</td>
			<td></td>
			<td></td>
			<td>0.1 M sodium bicarbonate (NaHCO3) in H2O (pH 9.6)</td>
		</tr>
		<tr>
			<td>desalting columns MWCO 7 kDa</td>
			<td>Thermo Fisher Scientific</td>
			<td>89891</td>
			<td>Thermo Scientific Zeba Spin Desalting Columns, 7K MWCO, 5 mL</td>
		</tr>
		<tr>
			<td>detection reagent ELISA (HRPO substrate)</td>
			<td>Sigma-Aldrich/Merck</td>
			<td>T8665-100ML</td>
			<td>3,3&#8242;,5,5&#8242;-Tetramethylbenzidine (TMB) liquid substrate system</td>
		</tr>
		<tr>
			<td>detection reagent western blot (HRPO substrate)</td>
			<td>Roche/Merck</td>
			<td>12 015 200 01</td>
			<td>Lumi-Light Western Blotting Substrate (Roche)</td>
		</tr>
		<tr>
			<td>dialysis tubing MWCO 12 - 14 kDa</td>
			<td>SERVA Electrophoresis</td>
			<td>44110</td>
			<td>Visking dialysis tubing, 16 mm diameter</td>
		</tr>
		<tr>
			<td>ELISA 96-well plate</td>
			<td>Thermo Fisher Scientific</td>
			<td>442404</td>
			<td>MaxiSorp Nunc-Immuno Plate</td>
		</tr>
		<tr>
			<td>fetal calf serum</td>
			<td>PAN-BIOtech</td>
			<td>P40-47500</td>
			<td>FBS Good forte</td>
		</tr>
		<tr>
			<td>ISF-1 medium</td>
			<td>Biochrom/bioswisstec</td>
			<td>F 9061-01</td>
			<td></td>
		</tr>
		<tr>
			<td>milk powder</td>
			<td>Carl Roth</td>
			<td>T145.2</td>
			<td>powdered milk, blotting grade, low in fat; alternatively we have also used conventional skimmed milk powder from the supermarket</td>
		</tr>
		<tr>
			<td>NLDC-145 hybridoma</td>
			<td>ATCC</td>
			<td>HB-290</td>
			<td>if not already at hand, the hybridoma cells can be acquired from ATCC</td>
		</tr>
		<tr>
			<td>non-reducing SDS sample buffer 4 x&#160;</td>
			<td></td>
			<td></td>
			<td>for 12 ml: 4 ml of 10 % SDS, 600 &#181;l 0.5 M Tris-HCl (ph 6.8), 3.3 ml sterile H2O, 4 ml glycerine, 100 &#181;l of 5 % Bromphenol Blue</td>
		</tr>
		<tr>
			<td>ovalbumin</td>
			<td>Hyglos (via BioVendor)</td>
			<td>321000</td>
			<td>EndoGrade OVA ultrapure with &#60;0.1 EU/mg</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Thermo Fisher Scientific</td>
			<td>15140122</td>
			<td>Gibco Penicillin/Streptomycin 10.000 U/ml; alternatively Gibco Penicillin/Streptomycin 5.000 U/ml (15070-063) can be used</td>
		</tr>
		<tr>
			<td>PETG polyethylene terephthalate glycol cell culture roller bottles</td>
			<td>Nunc In Vitro</td>
			<td>734-2394</td>
			<td>standard PDL-coated, vented (1.2X), 1050 cm&#178;, 100 - 500 ml volume; obtained from VWR, Germany&#160;&#160;</td>
		</tr>
		<tr>
			<td>pH indicator strips</td>
			<td>Merck</td>
			<td>109535</td>
			<td>pH indicator strips 0-14</td>
		</tr>
		<tr>
			<td>polyclonal goat &#945;rat-IgG(H+L)-HRPO (western blot)</td>
			<td>Jackson ImmunoResearch&#160;</td>
			<td>112-035-062</td>
			<td>obtained from Dianova, Germany; used at 1:5000 for western blot</td>
		</tr>
		<tr>
			<td>polyclonal goat &#945;rat-IgG+IgM-HRPO antibody&#160; (ELISA)</td>
			<td>Jackson ImmunoResearch&#160;</td>
			<td>112-035-068</td>
			<td>obtained from Dianova, Germany; used at 1:2000 for ELISA</td>
		</tr>
		<tr>
			<td>polyclonal goat &#945;rabbit-IgG-HRPO (western blot)</td>
			<td>Jackson ImmunoResearch&#160;</td>
			<td>111-035-045&#160;</td>
			<td>obtained from Dianova, Germany; used at 1:2000 for western blot</td>
		</tr>
		<tr>
			<td>polyclonal rabbit &#945;OVA (ELISA)</td>
			<td>Abcam</td>
			<td>ab181688</td>
			<td>used at 3 ng/&#181;l</td>
		</tr>
		<tr>
			<td>polyclonal rabbit &#945;OVA antibody (western blot)</td>
			<td>OriGene</td>
			<td>R1101</td>
			<td>used at 1:3,000 for western blot</td>
		</tr>
		<tr>
			<td>Protein G Sepharose column</td>
			<td>Merck/Millipore</td>
			<td>P3296</td>
			<td>5 ml Protein G Sepharose, Fast Flow are packed onto an empty column PD-10 (Merck, GE 17-0435-01)</td>
		</tr>
		<tr>
			<td>protein standard</td>
			<td>Thermo Fisher Scientific</td>
			<td>26616</td>
			<td>PageRuler Prestained Protein ladder 10 - 180 kDa</td>
		</tr>
		<tr>
			<td>PVDF (polyvinylidene difluoride) membrane</td>
			<td>Merck/Millipore</td>
			<td>IPVH00010</td>
			<td>immobilon-P PVDF (polyvinylidene difluoride) membrane</td>
		</tr>
		<tr>
			<td>rubber plug</td>
			<td>Omnilab</td>
			<td>5230217</td>
			<td>DEUTSCH &#38; NEUMANN rubber stoppers (lower &#934; 17 mm; upper &#934; 22 mm)</td>
		</tr>
		<tr>
			<td>silicone tube</td>
			<td>Omnilab</td>
			<td>5430925</td>
			<td>DEUTSCH &#38; NEUMANN (inside &#934; 1 mm; outer &#934; 3 mm)</td>
		</tr>
		<tr>
			<td>Slim-Fast</td>
			<td></td>
			<td></td>
			<td>we have used regular Slim-Fast Chocolate freely available at the pharmacy as in this western blot approach it yielded better results than milk powder</td>
		</tr>
		<tr>
			<td>stopping solution (ELISA)</td>
			<td></td>
			<td></td>
			<td>1M H2SO4</td>
		</tr>
		<tr>
			<td>sulfo-SMCC</td>
			<td>Thermo Fisher Scientific</td>
			<td>22322</td>
			<td>Pierce Sulfo-SMCC Cross-Linker; alternatively use catalog number A39268 (10 x 2 mg)</td>
		</tr>
		<tr>
			<td>syringe filter unit 0.22 &#181;m&#160;</td>
			<td>Merck/Millipore</td>
			<td>SLGV033RS</td>
			<td>Millex-GV Syringe Filter Unit, 0.22 &#181;m, PVDF, 33 mm, gamma sterilized&#160;</td>
		</tr>
		<tr>
			<td>syringe 10 ml</td>
			<td>Omnilab</td>
			<td></td>
			<td>Disposable syringes Injekt&#174; Solo B.Braun</td>
		</tr>
		<tr>
			<td>Sterican&#174; cannulas</td>
			<td>B. Braun</td>
			<td></td>
			<td>Sterican&#174; G 20 x 1 1/2&#34;&#34;; 0.90 x 40 mm; yellow</td>
		</tr>
		<tr>
			<td>TBS-T</td>
			<td></td>
			<td></td>
			<td>Tris-buffered saline containing 0.1 % (v/v) Tween 20</td>
		</tr>
		<tr>
			<td>TCEP-HCl</td>
			<td>Thermo Fisher Scientific</td>
			<td>A35349</td>
			<td></td>
		</tr>
		<tr>
			<td>tubing connector</td>
			<td>Omnilab</td>
			<td></td>
			<td>Kleinfeld miniature tubing connectors for silicone tube</td>
		</tr>
	</tbody>
</table>

chemical conjugation of a purified dec-205-directed antibody with full-length protein for targeting mouse dendritic cells in vitro and in vivo

Targeted antigen delivery to cross-presenting dendritic cells (DC) in vivo efficiently induces T effector cell responses and displays a valuable approach in&#160;vaccine design. Antigen is delivered to DC via antibodies specific for endocytosis receptors such as DEC-205 that induce uptake, processing, and MHC class I- and II-presentation.
Efficient and reliable conjugation of the desired antigen to a suitable antibody is a critical step in DC targeting and among other factors depends on the format of the antigen. Chemical conjugation of&#160;full-length protein to purified antibodies is one possible strategy. In the past, we have successfully established cross-linking of the model antigen ovalbumin (OVA) and a DEC-205-specific IgG2a antibody (&#945;DEC-205)&#160;for in vivo DC targeting studies in mice. The first step of the protocol is the purification of the antibody from the supernatant of the NLDC (non-lymphoid dendritic cells)-145 hybridoma by affinity chromatography. The purified antibody is activated for chemical conjugation by sulfo-SMCC (sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate) while at the same time the sulfhydryl-groups of the OVA protein are exposed through incubation with TCEP-HCl (tris (2-carboxyethyl) phosphine hydrochloride). Excess TCEP-HCl and sulfo-SMCC are removed and the antigen is mixed with the activated antibody for overnight coupling. The resulting &#945;DEC-205/OVA conjugate is concentrated and freed from unbound OVA. Successful conjugation of OVA to &#945;DEC-205 is verified by western blot analysis and enzyme-linked immunosorbent assay (ELISA).
We have successfully used chemically crosslinked &#945;DEC-205/OVA to induce cytotoxic T cell responses in the liver and to compare different adjuvants for their potential in inducing humoral and cellular immunity following in vivo targeting of DEC-205+ DC. Beyond that, such chemically coupled antibody/antigen conjugates offer valuable tools for the efficient induction of vaccine responses to tumor antigens and have been proven to be superior to classical immunization approaches regarding the prevention and therapy of various types of tumors.

Chemical conjugation of &#945;DEC-205 to OVA protein using this protocol will typically allow efficient generation of &#945;DEC-205/OVA for in vivo DC targeting approaches. There are different strategies to verify the technique itself and to test the functionality of the yielded conjugate. Western blot analysis and ELISA are used to verify successful conjugation and at the same time detect potentially left free OVA (Figure 2). In vitro bindi...

Watch this Scientific Journal Video about Chemical Conjugation of a Purified DEC-205-Directed Antibody with Full-Length Protein for Targeting Mouse Dendritic Cells In Vitro and In Vivo at JoVE.com

Chemical Conjugation of a Purified DEC-205-Directed Antibody with Full-Length Protein for Targeting Mouse Dendritic Cells In Vitro and In Vivo

We describe a protocol for the chemical conjugation of the model antigen ovalbumin to an endocytosis receptor-specific antibody for in vivo dendritic cell targeting. The protocol includes purification of the antibody, chemical conjugation of the antigen, as well as purification of the conjugate and the verification of efficient conjugation.

Chemical Conjugation of a Purified DEC-205-Directed Antibody with Full-Length Protein for Targeting Mouse Dendritic Cells In Vitro and In Vivo

Targeted antigen delivery to cross-presenting dendritic cells (DC) in vivo efficiently induces T effector cell responses and displays a valuable approach ...

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3.3K Views.  Helmholtz Centre for Infection Research. We describe a protocol for the chemical conjugation of the model antigen ovalbumin to an endocytosis receptor-specific antibody for in vivo dendritic cell targeting. The protocol includes purification of the antibody, chemical conjugation of the antigen, as well as purification of the conjugate and the verification of efficient conjugation.

Video: Chemical Conjugation of a Purified DEC-205-Directed Antibody with Full-Length Protein for Targeting Mouse Dendritic Cells In Vitro and In Vivo

In Vitro Imaging and Quantification of the Drug Targeting Efficiency of Fluorescently Labeled GnRH Analogues

GnRH analogues are effective targeting moieties and able to deliver anticancer agents selectively into malignant tumor cells which highly express GnRH receptors. However, the quantitative analysis of GnRH analogues&#39; cellular uptake and the investigated cell types in GnRH-based drug delivery systems are currently limited. Previously introduced, selectively labeled fluorescent GnRH I, -II and -III derivatives provide great detectability, and they have suitable chemical properties for reproducible and robust experiments. We also found that the appropriate up-to-date methods with these labeled GnRH analogues could offer novel information about the GnRH-based drug delivery systems. This manuscript introduces some simple and fast experiments regarding the cellular uptake of [D-Lys6(FITC)]-GnRH-I, [D-Lys6(FITC)]-GnRH-II and [Lys8(FITC)]-GnRH-III on the EBC-1 (lung), the BxPC-3 (pancreas) and on the Detroit-562- (pharynx) malignant tumor cells. In parallel with these GnRH-FITC conjugates, the cell surface level of GnRH-I receptors was also examined on these cell lines before and after the GnRH treatment by confocal laser scanning microscopy. The cellular uptake of GnRH-FITC conjugates was quantified by fluorescence-activated cell sorting. In these experiments minor differences among GnRH analogues and major differences among cell types was observed. The significant differences among cell lines are correlated with their distinct level of cell surface GnRH-I receptors. The introduced experiments contain practical methods to visualize, quantify and compare the uptake efficiency of GnRH-FITC conjugates in a time- and concentration-dependent manner on various adherent cell cultures. These results could predict the drug targeting efficiency of GnRH conjugates on the given cell culture, and offer a good basis for further experiments in the examination of GnRH-based drug delivery systems.

In Vitro Imaging and Quantification of the Drug Targeting Efficiency of Fluorescently Labeled GnRH Analogues

Selectively labeled fluorescent GnRH-I, -II and -III derivatives are reliable tools for tracking and quantifying their cellular uptake. This manuscript introduces experiments to visualize, quantify and compare the uptake efficiency of these GnRH conjugates in various cell lines.

GnRH analogues are effective targeting moieties and able to deliver anticancer agents selectively into malignant tumor cells which highly express GnRH ...

Establishing Dual Resistance to EGFR-TKI and MET-TKI in Lung Adenocarcinoma Cells In Vitro with a 2-step Dose-escalation Procedure

Drug resistance is a major challenge in cancer therapy. The generation of resistant sublines in vitro is necessary for discovering novel mechanisms to overcome this challenge. Here, a 2-step dose-escalation method for establishing dual-resistance to an epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI), gefitinib, and a MET-TKI, PHA665752, is described. This method is based on simple stepwise dose-escalation of inhibitors for inducing acquired resistance in cell lines. The alternate method for generating resistant sublines involves exposing the cells to high concentrations of the inhibitor in one step. The stepwise dose-escalation method has a higher possibility of successfully inducing acquired resistance than this method. Activating EGFR mutations are biomarkers of a response to treatment with EGFR-TKI, which is an applied first-line treatment for non-small cell lung cancers (NSCLC) that harbor these mutations. However, despite reports of effective responses, the use of EGFR-TKI is limited because tumors inevitably acquire resistance. The major mechanisms behind EGFR-TKI resistance include a secondary mutation at the gatekeeper site, T790M in exon 20 of EGFR, and a bypass signal of MET. Thus, a potential solution for this issue would be a combination of EGFR-TKI and MET-TKI. This combined treatment has been shown to be effective in an in vitro study model. Acquired gefitinib-resistance was established through MET-amplification by stepwise dose-escalation of gefitinib for 12 months, and a cell line named PC-9MET1000 was generated in a previous study. To further investigate the mechanisms of acquired MET-TKI and EGFR-TKI resistance, a MET-TKI, PHA665752, was administered to these cells with stepwise dose-escalation in the presence of gefitinib for 12 months. This protocol has also been successfully applied for a number of combination therapies to establish acquired resistance to other inhibitor molecules.

Establishing Dual Resistance to EGFR-TKI and MET-TKI in Lung Adenocarcinoma Cells In Vitro with a 2-step Dose-escalation Procedure

An in vitro method for establishing dual resistance to an EGFR-TKI and a MET-TKI in cancer cells is described. This method is useful for developing treatments for patients with EGFR-mutations, who exhibit disease progression despite EGFR-TKI treatment with MET-amplification. It can also be modified for inhibitors targeting other molecules.

Drug resistance is a major challenge in cancer therapy. The generation of resistant sublines in vitro is necessary for discovering novel mechanisms to ...

Counting Proteins in Single Cells with Addressable Droplet Microarrays

Often cellular behavior and cellular responses are analyzed at the population level where the responses of many cells are pooled together as an average result masking the rich single cell behavior within a complex population. Single cell protein detection and quantification technologies have made a remarkable impact in recent years. Here we describe a practical and flexible single cell analysis platform based on addressable droplet microarrays. This study describes how the absolute copy numbers of target proteins may be measured with single cell resolution. The tumor suppressor p53 is the most commonly mutated gene in human cancer, with more than 50% of total cancer cases exhibiting a non-healthy p53 expression pattern. The protocol describes steps to create 10 nL droplets within which single human cancer cells are isolated and the copy number of p53 protein is measured with single molecule resolution to precisely determine the variability in expression. The method may be applied to any cell type including primary material to determine the absolute copy number of any target proteins of interest.

Here we present addressable droplet microarrays (ADMs), a droplet array based method able to determine absolute protein abundance in single cells. We demonstrate the capability of ADMs to characterize the heterogeneity in expression of the tumor suppressor protein p53 in a human cancer cell line.

Often cellular behavior and cellular responses are analyzed at the population level where the responses of many cells are pooled together as an average ...

Moving Upwards: A Simple and Flexible In Vitro Three-dimensional Invasion Assay Protocol

Although 3D invasion assays have been developed, the challenge remains to study cells without affecting the integrity of their microenvironment. Traditional 3D assays such as the Boyden Chamber require that cells are displaced from the original culture location and moved to a new environment. Not only does this disrupt the cellular processes that are intrinsic to the microenvironment, but it often results in a loss of cells. These problems are especially challenging when dealing with cells that are either rare, or extremely sensitive to their microenvironment. Here, we describe the development of a 3D invasion assay that avoids both concerns. In this assay, cells are plated within a small well and an ECM matrix containing a chemoattractant is laid atop the cells. This requires no cell displacement, and allows the cells to invade upwards into the matrix. In this assay, cell invasion as well as cell morphology can be assessed within the collagen gel. Using this assay, we characterize the invasive capacity of rare and sensitive cells; the hybrid cells resulting from fusion between breast cancer cells MCF7 and mesenchymal/multipotent stem/stroma cells (MSCs).

Moving Upwards: A Simple and Flexible In Vitro Three-dimensional Invasion Assay Protocol

This protocol describes an inverted vertical invasion assay that could be used to quantify the migration and invasion capabilities of cells in a three-dimensional setting while preserving the cell microenvironment. This assay is suitable for rare and/or sensitive cells.

Although 3D invasion assays have been developed, the challenge remains to study cells without affecting the integrity of their microenvironment. ...

In Vivo EPR Assessment of pH, pO2, Redox Status, and Concentrations of Phosphate and Glutathione in the Tumor Microenvironment

This protocol demonstrates the capability of low-field electron paramagnetic resonance (EPR)-based techniques in combination with functional paramagnetic probes to provide quantitative information on the chemical tumor microenvironment (TME), including pO2, pH, redox status, concentrations of interstitial inorganic phosphate (Pi), and intracellular glutathione (GSH). In particular, an application of a recently developed soluble multifunctional trityl probe provides unsurpassed opportunity for in vivo concurrent measurements of pH, pO2 and Pi in Extracellular space (HOPE probe). The measurements of three parameters using a single probe allow for their correlation analyses independent of probe distribution and time of the measurements.

In Vivo EPR Assessment of pH, pO2, Redox Status, and Concentrations of Phosphate and Glutathione in the Tumor Microenvironment

Low-field (L-band, 1.2 GHz) electron paramagnetic resonance using soluble nitroxyl and trityl probes is demonstrated for assessment of physiologically important parameters in the tumor microenvironment in mouse models of breast cancer.

This protocol demonstrates the capability of low-field electron paramagnetic resonance (EPR)-based techniques in combination with functional paramagnetic ...

Isolation Protocol of Mouse Monocyte-derived Dendritic Cells and Their Subsequent In Vitro Activation with Tumor Immune Complexes

Dendritic cells (DC) are heterogeneous cell populations that differ in their cell membrane markers, migration patterns and distribution, and in their antigen presentation and T cell activation capacities. Since most vaccinations of experimental tumor models require millions of DC, they are widely isolated from the bone marrow or spleen. However, these DC significantly differ from blood and tumor DC in their responses to immune complexes (IC), and presumably to other Syk-coupled lectin receptors. Importantly, given the sensitivity of DC to danger-associated molecules, the presence of endotoxins or antibodies that crosslink activation receptors in one of the isolating steps could result in the priming of DC and thus affect the parameters, or at least the dosage, required to activate them. Therefore, here we describe a detailed protocol for isolating MoDC from blood and tumors while avoiding their premature activation. In addition, a protocol is provided for MoDC activation with tumor IC, and their subsequent analyses.

Isolation Protocol of Mouse Monocyte-derived Dendritic Cells and Their Subsequent In Vitro Activation with Tumor Immune Complexes

Monocyte-derived DC (MoDC) can sense minor amounts of danger-associated molecules and are therefore easily primed. We provide a detailed protocol for the isolation of MoDC from blood and tumors and their activation with immune complexes while highlighting key precautions that should be considered in order to avoid their premature activation.

Dendritic cells (DC) are heterogeneous cell populations that differ in their cell membrane markers, migration patterns and distribution, and in their ...

A GPC3-targeting Bispecific Antibody, GPC3-S-Fab, with Potent Cytotoxicity

This protocol describes the construction and functional studies of a bispecific antibody (bsAb), GPC3-S-Fab. bsAbs can recognize two different epitopes through their two different arms. bsAbs have been actively studied for their ability to directly recruit immune cells to kill tumor cells. Currently, the majority of bsAbs are produced in the form of recombinant proteins, either as Fc-containing bsAbs or as smaller bsAb derivatives without the Fc region. In this study, GPC3-S-Fab, an antibody fragment (Fab) based bispecific antibody, was designed by linking the Fab of anti-GPC3 antibody GC33 with an anti-CD16 single domain antibody. The GPC3-S-Fab can be expressed in Escherichia coli and purified by two affinity chromatographies. The purified GPC3-S-Fab can specifically bind to and kill GPC3 positive liver cancer cells by recruiting natural killer cells, suggesting a potential application of GPC3-S-Fab in liver cancer therapy.

Here, we present a protocol to produce a bispecific antibody GPC3-S-Fab in Escherichia coli. The purified GPC3-S-Fab has potent cytotoxicity against GPC3 positive liver cancer cells.

This protocol describes the construction and functional studies of a bispecific antibody (bsAb), GPC3-S-Fab. bsAbs can recognize two different epitopes ...

Phosphopeptide Enrichment Coupled with Label-free Quantitative Mass Spectrometry to Investigate the Phosphoproteome in Prostate Cancer

Phosphoproteomics involves the large-scale study of phosphorylated proteins. Protein phosphorylation is a critical step in many signal transduction pathways and is tightly regulated by kinases and phosphatases. Therefore, characterizing the phosphoproteome may provide insights into identifying novel targets and biomarkers for oncologic therapy. Mass spectrometry provides a way to globally detect and quantify thousands of unique phosphorylation events. However, phosphopeptides are much less abundant than non-phosphopeptides, making biochemical analysis more challenging. To overcome this limitation, methods to enrich phosphopeptides prior to the mass spectrometry analysis are required. We describe a procedure to extract and digest proteins from tissue to yield peptides, followed by an enrichment for phosphotyrosine (pY) and phosphoserine/threonine (pST) peptides using an antibody-based and/or titanium dioxide (TiO2)-based enrichment method. After the sample preparation and mass spectrometry, we subsequently identify and quantify phosphopeptides using liquid chromatography-mass spectrometry and analysis software.

This protocol describes a procedure to extract and enrich phosphopeptides from prostate cancer cell lines or tissues for an analysis of the phosphoproteome via mass spectrometry-based proteomics.

Phosphoproteomics involves the large-scale study of phosphorylated proteins. Protein phosphorylation is a critical step in many signal transduction ...

In Vivo Immunofluorescence Localization for Assessment of Therapeutic and Diagnostic Antibody Biodistribution in Cancer Research

Monoclonal antibodies (mAbs) are important tools in cancer detection, diagnosis, and treatment. They are used to unravel the role of proteins in tumorigenesis, can be directed to cancer biomarkers enabling tumor detection and characterization, and can be used for cancer therapy as mAbs or antibody-drug conjugates to activate immune effector cells, to inhibit signaling pathways, or directly kill cells carrying the specific antigen. Despite clinical advancements in the development and production of novel and highly specific mAbs, diagnostic and therapeutic applications can be impaired by the complexity and heterogeneity of the tumor microenvironment. Thus, for the development of efficient antibody-based therapies and diagnostics, it is crucial to assess the biodistribution and interaction of the antibody-based conjugate with the living tumor microenvironment. Here, we describe In Vivo Immunofluorescence Localization (IVIL) as a new approach to study interactions of antibody-based therapeutics and diagnostics in the in vivo physiological and pathological conditions. In this technique, a therapeutic or diagnostic antigen-specific antibody is intravenously injected in&#160;vivo and localized ex vivo with a secondary antibody in isolated tumors. IVIL, therefore, reflects the in vivo biodistribution of antibody-based drugs and targeting agents. Two IVIL applications are described assessing the biodistribution and accessibility of antibody-based contrast agents for molecular imaging of breast cancer. This protocol will allow future users to adapt the IVIL method for their own antibody-based research applications.

The in vivo immunofluorescence localization (IVIL) method can be used to examine in vivo biodistribution of antibodies and antibody conjugates for oncological purposes in living organisms using a combination of in vivo tumor targeting and ex vivo immunostaining methods.

Monoclonal antibodies (mAbs) are important tools in cancer detection, diagnosis, and treatment. They are used to unravel the role of proteins in ...

In Vivo Targeting of Xenografted Human Cancer Cells with Functionalized Fluorescent Silica Nanoparticles in Zebrafish

Developing nanoparticles capable of detecting, targeting, and destroying cancer cells is of great interest in the field of nanomedicine. In vivo animal models are required for bridging the nanotechnology to its biomedical application. The mouse represents the traditional animal model for preclinical testing; however, mice are relatively expensive to keep and have long experimental cycles due to the limited progeny from each mother. The zebrafish has emerged as a powerful model system for developmental and biomedical research, including cancer research. In particular, due to its optical transparency and rapid development, zebrafish embryos are well suited for real-time in vivo monitoring of the behavior of cancer cells and their interactions with their microenvironment. This method was developed to sequentially introduce human cancer cells and functionalized nanoparticles in transparent Casper zebrafish embryos and monitor in vivo recognition and targeting of the cancer cells by nanoparticles in real time. This optimized protocol shows that fluorescently labeled nanoparticles, which are functionalized with folate groups, can specifically recognize and target metastatic human cervical epithelial cancer cells labeled with a different fluorochrome. The recognition and targeting process can occur as early as 30 min postinjection of the nanoparticles tested. The whole experiment only requires the breeding of a few pairs of adult fish and takes less than 4 days to complete. Moreover, zebrafish embryos lack a functional adaptive immune system, allowing the engraftment of a wide range of human cancer cells. Hence, the utility of the protocol described here enables the testing of nanoparticles on various types of human cancer cells, facilitating the selection of optimal nanoparticles in each specific cancer context for future testing in mammals and the clinic.

Described here is a method for utilizing zebrafish embryos to study the ability of functionalized nanoparticles to target human cancer cells in vivo. This method allows for the evaluation and selection of optimal nanoparticles for future testing in large animals and in clinical trials.

Developing nanoparticles capable of detecting, targeting, and destroying cancer cells is of great interest in the field of nanomedicine. In vivo animal ...