We are particularly grateful to S. Graewe and V. Heussler for the initial training and continuous input in intravital microscopy of malaria parasites, to J. Burns for donating GFP transgenic parasites, to A. Bosch (Confocal Unit, CCiT-UB, IDIBAPS) for assistance in image analysis and quantification and to P. Astola for technical assistance. We thank R. Tous and I. Caralt for video production. MF is a recipient of a graduate fellowship from the Generality of Catalonia. HAP is an ICREA research professor. Work in the laboratory of HAP is funded by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement N&deg; 242095, by the Private Foundation CELLEX (Catalonia, Spain), and by the Spanish Ministry of Science and Innovation (SAF2009-07760).

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No conflicts of interest declared.

The implementation of intravital microscopy of the spleen in this rodent malaria model opened the possibility of investigating the dynamic passage of parasites through this organ which until now has been considered a "black-box" due to technical considerations. In here, a major effort was put to adapt a quantitative method that allows comparative analysis of different parasite lines at the single and population levels. In contrast to other tissues and cells that had been imaged before in malaria 3,5, imaging ...

<table border="1">
<tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue 	number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>Leica 			TCS-SP5 confocal microscope</td>
 <td>Leica 			Microsystems, Heidelberg, Germany</td>
 <td>TCS-SP5 Serial 			no. 5100000419</td>
 <td>&nbsp;
 </td>
 </tr>
 <tr>
 <td>Ketamine 			(Ketolar 50 			mg/ml)</td>
 <td>Pfizer</td>
 <td>631028</td>
 <td>&nbsp;
 </td>
 </tr>
 <tr>
 <td>Midazolam 			15 mg/3 ml</td>
 <td>Normon</td>
 <td>838193</td>
 <td>&nbsp;
 </td>
 </tr>
 <tr>
 <td>70,000 			MW Dextran, conjugated to Texas Red</td>
 <td>Molecular 			Probes</td>
 <td>D1830</td>
 <td>&nbsp;
 </td>
 </tr>
 <tr>
 <td>Fluorescein 			Isothiocyanate, isomer I (FITC)</td>
 <td>Sigma</td>
 <td>F7250</td>
 <td>&nbsp;
 </td>
 </tr>
 <tr>
 <td>Hoechst 			33342</td>
 <td>Sigma</td>
 <td>H1399</td>
 <td>&nbsp;
 </td>
 </tr>
 <tr>
 <td>Giemsa 			stain</td>
 <td>Sigma</td>
 <td>GS1</td>
 <td>Working 			solution is at 10% 			in distilled water</td>
 </tr>
 <tr>
 <td>Super 			Glue-3 Loctite</td>
 <td>Loctite</td>
 <td>9975-0880</td>
 <td>&nbsp;
 </td>
 </tr>
 </tbody>
</table>

intravital microscopy of the spleen: quantitative analysis of parasite mobility and blood flow

The advent of intravital microscopy in experimental rodent malaria models has allowed major advances to the knowledge of parasite-host interactions 1,2. Thus, in vivo imaging of malaria parasites during pre-erythrocytic stages have revealed the active entrance of parasites into skin lymph nodes 3, the complete development of the parasite in the skin 4, and the formation of a hepatocyte-derived merosome to assure migration and release of merozoites into the blood stream 5. Moreover, the development of individual parasites in erythrocytes has been recently documented using 4D imaging and challenged our current view on protein export in malaria 6. Thus, intravital imaging has radically changed our view on key events in Plasmodium development. Unfortunately, studies of the dynamic passage of malaria parasites through the spleen, a major lymphoid organ exquisitely adapted to clear infected red blood cells are lacking due to technical constraints.
Using the murine model of malaria Plasmodium yoelii in Balb/c mice, we have implemented intravital imaging of the spleen and reported a differential remodeling of it and adherence of parasitized red blood cells (pRBCs) to barrier cells of fibroblastic origin in the red pulp during infection with the non-lethal parasite line P.yoelii 17X as opposed to infections with the P.yoelii 17XL lethal parasite line 7. To reach these conclusions, a specific methodology using ImageJ free software was developed to enable characterization of the fast three-dimensional movement of single-pRBCs. Results obtained with this protocol allow determining velocity, directionality and residence time of parasites in the spleen, all parameters addressing adherence in vivo. In addition, we report the methodology for blood flow quantification using intravital microscopy and the use of different colouring agents to gain insight into the complex microcirculatory structure of the spleen. 
Ethics statement
All the animal studies were performed at the animal facilities of University of Barcelona in accordance with guidelines and protocols approved by the Ethics Committee for Animal Experimentation of the University of Barcelona CEEA-UB (Protocol No DMAH: 5429). Female Balb/c mice of 6-8 weeks of age were obtained from Charles River Laboratories.

Watch this Scientific Journal Video about Intravital Microscopy of the Spleen: Quantitative Analysis of Parasite Mobility and Blood Flow at JoVE.com

Intravital Microscopy of the Spleen: Quantitative Analysis of Parasite Mobility and Blood Flow

We show the method for performing intravital microscopy of the spleen using GFP transgenic malaria parasites and the quantification of parasite mobility and blood flow within this organ.

The advent of intravital microscopy in experimental rodent malaria models has allowed major advances to the knowledge of parasite-host interactions 1,2. ...

intravital-microscopy-spleen-quantitative-analysis-parasite-mobility

Research

JoVE Journal

Immunology and Infection

18.1K Views.  Barcelona Centre for International Health Research. We show the method for performing intravital microscopy of the spleen using GFP transgenic malaria parasites and the quantification of parasite mobility and blood flow within this organ.