We thank Drs Randy Elkins, Robin Kastenmayer, Ted Torrey, Dan Pare and Tovi Lehman for critical reading of manuscripts. This work was supported by the Intramural Research Program of the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, and by the 973 National Basic Research Program of China, #2007CB513103. We thank NIAID intramural editor Brenda Rae Marshall for assistance.

Aseptic techniques must be applied to all materials that will be administrated into animals to avoid inadvertent introduction of exogenous infectious agents into mice that can confound experimental outcomes.

1. 	 Infection of Laboratory Mice with Blood-stage Malaria Parasites
<ol>
<li>At room temperature, thaw two vials containing the frozen blood stage malaria parasites to be crossed. In this example, two rodent malaria parasite strains used are Plasmodium yoelii yoelii and <e...

<ol>
	<li>Hayton, K., Ranford-Cartwright, L. C., Walliker, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulfadoxine-pyrimethamine+resistance+in+the+rodent+malaria+parasite+Plasmodium+chabaudi.">Sulfadoxine-pyrimethamine resistance in the rodent malaria parasite Plasmodium chabaudi.</a> Antimicrob Agents Chemother. 46, 2482-2489 (2002).</li><li>Cravo, P. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetics+of+mefloquine+resistance+in+the+rodent+malaria+parasite+Plasmodium+chabaudi.">Genetics of mefloquine resistance in the rodent malaria parasite Plasmodium chabaudi.</a> Antimicrob Agents Chemother. 47, 709-718 (2003).</li><li>Hunt, P., Cravo, P. V., Donleavy, P., Carlton, J. M., Walliker, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chloroquine+resistance+in+Plasmodium+chabaudi:+are+chloroquine-resistance+transporter+(crt)+and+multi-drug+resistance+(mdr1)+orthologues+involved?.">Chloroquine resistance in Plasmodium chabaudi: are chloroquine-resistance transporter (crt) and multi-drug resistance (mdr1) orthologues involved?.</a> Mol Biochem Parasitol. 133, 27-35 (2004).</li><li>Yuan, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+mapping+of+targets+mediating+differential+chemical+phenotypes+in+Plasmodium+falciparum.">Genetic mapping of targets mediating differential chemical phenotypes in Plasmodium falciparum.</a> Nat Chem Biol. 5, 765-771 (2009).</li><li>Su, X., Kirkman, L. A., Fujioka, H., Wellems, T. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complex+polymorphisms+in+an+approximately+330+kDa+protein+are+linked+to+chloroquine-resistant+P.+falciparum+in+Southeast+Asia+and+Africa.">Complex polymorphisms in an approximately 330 kDa protein are linked to chloroquine-resistant P. falciparum in Southeast Asia and Africa.</a> Cell. 91, 593-603 (1997).</li><li>Hayton, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Erythrocyte+binding+protein+PfRH5+polymorphisms+determine+species-specific+pathways+of+Plasmodium+falciparum+invasion.">Erythrocyte binding protein PfRH5 polymorphisms determine species-specific pathways of Plasmodium falciparum invasion.</a> Cell Host Microbe. 4, 40-51 (2008).</li><li>Pattaradilokrat, S., Cheesman, S. J., Carter, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Congenicity+and+genetic+polymorphism+in+cloned+lines+derived+from+a+single+isolate+of+a+rodent+malaria+parasite.">Congenicity and genetic polymorphism in cloned lines derived from a single isolate of a rodent malaria parasite.</a> Mol Biochem Parasitol. 157, 244-247 (2008).</li><li>Li, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hundreds+of+microsatellites+for+genotyping+Plasmodium+yoelii+parasites.">Hundreds of microsatellites for genotyping Plasmodium yoelii parasites.</a> Mol Biochem Parasitol. 166, 153-158 (2009).</li><li>Li, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Typing+Plasmodium+yoelii+microsatellites+using+a+simple+and+affordable+fluorescent+labeling+method.">Typing Plasmodium yoelii microsatellites using a simple and affordable fluorescent labeling method.</a> Mol Biochem Parasitol. 155, 94-102 (2007).</li><li>Walliker, D., Carter, R., Morgan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+recombination+in+malaria+parasites.">Genetic recombination in malaria parasites.</a> Nature. 232, 561-562 (1971).</li><li>Sinden, R. E., Hartley, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+the+meiotic+division+of+malarial+parasites.">Identification of the meiotic division of malarial parasites.</a> J Protozool. 32, 742-744 (1985).</li><li>Ozaki, L. S., Gwadz, R. W., Godson, G. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+centrifugation+method+for+rapid+separation+of+sporozoites+from+mosquitoes.">Simple centrifugation method for rapid separation of sporozoites from mosquitoes.</a> J Parasitol. 70, 831-833 (1984).</li><li>Yoeli, M., Most, H., Bone, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmodium+berghei:+cyclical+transmission+by+experimentally+infected+Anopheles+quadrimachulatus.">Plasmodium berghei: cyclical transmission by experimentally infected Anopheles quadrimachulatus.</a> Science. 144, 1580-1581 (1964).</li><li>Landau, I., Boulard, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Life cycles and Morphology. , (1978).</li><li>Vanderbergh, J. P. Y., M, . <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+temperature+on+sporogonic+development+of+Plasmodium+berghei.">Effects of temperature on sporogonic development of Plasmodium berghei.</a> J Parasitol. 52, 559-564 (1966).</li><li>Gadsby, N., Lawrence, R., Carter, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+study+on+pathogenicity+and+mosquito+transmission+success+in+the+rodent+malaria+parasite+Plasmodium+chabaudi+adami.">A study on pathogenicity and mosquito transmission success in the rodent malaria parasite Plasmodium chabaudi adami.</a> Int J Parasitol. 39, 347-354 (2009).</li><li>Pattaradilokrat, S., Culleton, R. L., Cheesman, S. J., Carter, R. G. e. n. e. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=encoding+erythrocyte+binding+ligand+linked+to+blood+stage+multiplication+rate+phenotype+in+Plasmodium+yoelii+yoelii.">encoding erythrocyte binding ligand linked to blood stage multiplication rate phenotype in Plasmodium yoelii yoelii.</a> Proc Natl Acad Sci U S A. 106, 7161-7166 (2009).</li><li>Pattaradilokrat, S., Cheesman, S. J., Carter, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Linkage+group+selection:+towards+identifying+genes+controlling+strain+specific+protective+immunity+in+malaria.">Linkage group selection: towards identifying genes controlling strain specific protective immunity in malaria.</a> PLoS One. 2, e857-e857 (2007).</li><li>Mackinnon, M. J., Read, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+Relationships+between+Parasite+Virulence+and+Transmission+in+the+Rodent+Malaria+Plasmodium+chabaudi.">Genetic Relationships between Parasite Virulence and Transmission in the Rodent Malaria Plasmodium chabaudi.</a> Evolution. 53, 689-703 (1999).</li></ol>

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We demonstrate the techniques for the production of a genetic cross in the rodent malaria Plasmodium yoelii, which is also applicable to production of genetic crosses in other rodent malarias. Infections of mice with single parental clones are usually performed to determine successful transmission of the parental parasites to ensure that the parents are competent in producing functional gametes before performing a cross.
Successful transmission through a mosquito is influenced by mul...

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Glyerolyte 57 solution</td>
<td>&nbsp;</td>
<td>Cenmed</td>
<td>4A7833</td>
<td>&nbsp;</td>
<tr>
<td>Mouse Mus musculus</td>
<td>&nbsp;</td>
<td>Charles River Laboratory</td>
<td>&nbsp;</td>
<td>Female, inbred, strain Balb/C</td>
</tr>
<tr>
<td>Heat-inactivated calf serum</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>26010-066</td>
<td>&nbsp;</td>
<tr>
<td>Phosphate buffered saline (PBS) solution</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>10010-072</td>
<td>pH 7.4; Cell Culture grade </td>
</tr>
<tr>
<td>Malaria parasite Plasmodium yoelii yoelii 17XNL(1.1)</td>
<td>&nbsp;</td>
<td>MR4</td>
<td>MRA-593</td>
<td>deposited by DJ Carucci</td>
</tr>
<tr>
<td>Malaria parasite Plasmodium yoelii nigeriensis N67</td>
<td>&nbsp;</td>
<td>MR4</td>
<td>MRA-427</td>
<td>deposited by W Peters, BL Robinson, R Killick Kendrick</td>
</tr>
<tr>
<td>Mosquito Anopheles stephensi</td>
<td>&nbsp;</td>
<td>MR4</td>
<td>MRA-128</td>
<td>deposited by MQ Benedict</td>
</tr>
<tr>
<td>Cellometer automatic cell counter</td>
<td>&nbsp;</td>
<td>Nexcelom Biosciences</td>
<td>Cellometer Auto T4</td>
<td>&nbsp;</td>
<tr>
<td>Cellometer CP2 disposable hemacytometer</td>
<td>&nbsp;</td>
<td>Nexcelom Biosciences</td>
<td>Cellometer CP2 </td>
<td>&nbsp;</td>
<tr>
<td>High Pure PCR template preparation kit</td>
<td>&nbsp;</td>
<td>Roche Applied Science</td>
<td>11 796 828 001</td>
<td>&nbsp;</td>
<tr>
<td>Calcium chloride</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>C5670</td>
<td>Cell culture tested; insect cell culture tested</td>
</tr>
<tr>
<td>Giemsa stain, modified</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>GS500 </td>
<td>&nbsp;</td>
<tr>
<td>Ketamine hydrochloride</td>
<td>&nbsp;</td>
<td>Fort Dodge Animal Health</td>
<td> NDC 0856-2013-01</td>
<td> Pharmaceutical grade; concentration to 100 mg/mL</td>
</tr>
<tr>
<td>Potassium chloride</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>P5405</td>
<td>Cell culture tested; insect cell culture tested</td>
</tr>
<tr>
<td>Sodium chloride</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>S5886</td>
<td>Cell culture tested; insect cell culture tested</td>
</tr>
<tr>
<td>Trisodium citrate dihydrate</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>S4641</td>
<td>&nbsp;</td>
<tr>
<td>Xylazine</td>
<td>&nbsp;</td>
<td>Akorn Inc.</td>
<td> 4811-20ml</td>
<td>Pharmaceutical grade; concentration to 20 mg/mL</td>
</tr>
<tr>
<td>Glass wool</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>32848-003</td>
<td>&nbsp;</td>
<tr>
<td>Glass capillary (1 &mu;L)</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>53440-001</td>
<td>&nbsp;</td>
<tr>
<td>Hemocytometer</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>15170-168</td>
<td>Complete chamber set</td>
</tr>
<tr>
<td>Homogenizer</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>KT749520-0090</td>
<td>Pestle with matching tube, 1.5 mL </td>
</tr>		</tbody>
		</table>
		</div>
			<div>
			SUPPLEMENTARY MATERIALS:
<ul>
<li>Maintenance of laboratory mice</li>
<li>Maintenance of laboratory mosquitoes</li>
<li>Microscopic examination of thin blood smears stained with Giemsa stain</li>
<li>Measurement of red blood cell density</li>
</ul>

Maintenance of laboratory mice
Females of inbred laboratory mouse strain BALB/c, aged 5 to 8 weeks old, are used in the study. Mice are housed in a standard solid-bottom polycarbonate cage with wire-bar lid, equipped with feeder and a water bottle. Mice are maintained at a constant temperature (25 &plusmn; 1&deg;C) on 12:12 hour light:dark cycle. Mice are allowed to feed on 2018S Harlan Teklad Global 19% protein extruded rodent diet (sterilizable; from Harlan-Teklad) and supplied with acidified drinking water ad libitum. Experiments on animals are performed in accordance with the guidelines and regulations set forth by the Animal Care and Use Committee at the National Institute of Allergy and Infectious Disease under protocol LMVR11E (National Institutes of Health, Bethesda, Maryland).
Maintenance of laboratory mosquitoes
Mosquitoes are from a laboratory-bred colony of Anopheles stephensi. The adults are maintained in nylon cages kept in a temperature- and humidity-controlled room (23 to 25&deg;C for Plasmodium yoelii and Plasmodium chabaudi, and 19 to 21&deg;C for Plasmodium berghei; 80 to 95% humidity; on 12:12 hours light:dark cycle). Adult mosquitoes are fed with 10% glucose and 2.00% para-aminobenzoic acid (PABA) supplemented water solution. To obtain high-quality adults, 500 larvae are grown in a low-density condition in 1 L of distilled water in a 1,000-cm3 open dish supplied with approximately 1 mg of sodium bicarbonate. After hatching, the larvae are given tetramin powder (PETCO) until they develop into the pupa stage and are transferred to the adult mosquito cages for emerging.
Microscopic examination of thin blood smears stained with Giemsa stain
Using clean scissors snip off the tip (1.0 mm) of the infected mouse's tail. Place one drop (0.5-1.0 &mu;L) of tail blood onto a clean specimen slide. Mouse will stop bleeding in 1-2 min. Place a clean spreader slide on top of the blood drop, maintaining it at a 45&deg; angle relative to the specimen slide, and allow the blood to adsorb to the entire width of the spreader. Hold the specimen slide and push forward the spreader slide rapidly and smoothly to produce a thin smear. Let the blood film dry, and then immerse the slides in absolute methanol. Allow the slide to air dry once more before covering it with Giemsa stain (10% Giemsa dye in distilled water). After incubating the thin blood films for 10-15 min at room temperature, carefully rinse the slides with tap water and let it air dry. Examine the number of infected red blood cells (iRBC; see Figure 3 for morphology of infected RBC) under a light microscope with immersion oil at 1000x magnification (with 100x objective lens) and calculate parasitemia (the number of iRBC per 100 RBC counted). Different strains of malaria parasites vary in growth rate and pathogenicity. Monitoring of blood stage parasitaemias can be performed 24hrs after injections, depending on the dose of the blood stage malaria parasites. For example, mice will be microscopically positive 24 hrs when injected with 107 infected RBC intraperitoneally or 106 infected RBC intravenously.
Measurement of red blood cell density
Like the levels of parasitaemias, red blood cell (RBC) density in infected mice varies throughout the course of infection. RBC density should be measured within 1-2 hrs before the start of the single- and mixed-clone infection and the cloning experiments. There are two methods for measurement of RBC density: a manual counting using Neubauer hemocytometer and an automatic counting using a Cellometer (Nexcelom Bioscience). In both methods, withdraw 1 &mu;L of mouse tail blood using a glass capillary (VWR) and dilute in 10 mL of PBS and mix well. To use a Neubauer hemocytometer, load 20 &mu;L of the suspension onto the hemacytometer. Place the hemacytometer on a light microscope with 10x objective lens. The hemacytometer contains a grid divided into 9 large squares, and 4 large squares at the corner are further divided into 16 small squares. Count the total number of cells in each of the 16 small squares in the four corner squares. To avoid counting bias or counting cells that overlap a grid line, count a cell as "in" if it overlaps the top or right lines and "out" if it overlaps the bottom or left lines. Estimate the number of cells per one small square and divide by 0.00625 (the volume of one small square is 6.25 nL). This yields the number of cells per microliter (&mu;L). From this data, calculate the final red blood cell density by multiplying with 10,000 (a dilution factor). Rinse the cover slip and counting chamber with distilled water and 70% ethanol; air dry. Alternatively, load 20 &mu;L of the suspension onto a Cellometer counting chamber slide. Insert the slide into a Cellometer slide chamber (the reader). Start the Cellometer software, select the "red blood cell" option, and enter a dilution factor of 10,000. Record the RBC density.		</div>

protocol for production of a genetic cross of the rodent malaria parasites

Variation in response to antimalarial drugs and in pathogenicity of malaria parasites is of biologic and medical importance. Linkage mapping has led to successful identification of genes or loci underlying various traits in malaria parasites of rodents1-3 and humans4-6. The malaria parasite Plasmodium yoelii is one of many malaria species isolated from wild African rodents and has been adapted to grow in laboratories. This species reproduces many of the biologic characteristics of the human malaria parasites; genetic markers such as microsatellite and amplified fragment length polymorphism (AFLP) markers have also been developed for the parasite7-9. Thus, genetic studies in rodent malaria parasites can be performed to complement research on Plasmodium falciparum. Here, we demonstrate the techniques for producing a genetic cross in P. yoelii that were first pioneered by Drs. David Walliker, Richard Carter, and colleagues at the University of Edinburgh10.

Genetic crosses in P. yoelii and other rodent malaria parasites are conducted by infecting mice Mus musculus with an inoculum containing gametocytes of two genetically distinct clones that differ in phenotypes of interest and by allowing mosquitoes to feed on the infected mice 4 days after infection. The presence of male and female gametocytes in the mouse blood is microscopically confirmed before feeding. Within 48 hrs after feeding, in the midgut of the mosquito, the haploid gametocytes differentiate into male and female gametes, fertilize, and form a diploid zygote (Fig. 1). During development of a zygote into an ookinete, meiosis appears to occur11. If the zygote is derived through cross-fertilization between gametes of the two genetically distinct parasites, genetic exchanges (chromosomal reassortment and cross-overs between the non-sister chromatids of a pair of homologous chromosomes; Fig. 2) may occur, resulting in recombination of genetic material at homologous loci. Each zygote undergoes two successive nuclear divisions, leading to four haploid nuclei. An ookinete further develops into an oocyst. Once the oocyst matures, thousands of sporozoites (the progeny of the cross) are formed and released into mosquito hemoceal. Sporozoites are harvested from the salivary glands and injected into a new murine host, where pre-erythrocytic and erythrocytic stage development takes place. Erythrocytic forms are cloned and classified with regard to the characters distinguishing the parental lines prior to genetic linkage mapping. Control infections of individual parental clones are performed in the same way as the production of a genetic cross.

Watch this Scientific Journal Video about Protocol for Production of a Genetic Cross of the Rodent Malaria Parasites at JoVE.com

Protocol for Production of a Genetic Cross of the Rodent Malaria Parasites

Genetic crosses of rodent malaria parasites are performed by feeding two genetically distinct parasites to mosquitoes. Recombinant progeny are cloned from mouse blood after allowing mosquitoes to bite infected mice. This video shows how to produce genetic crosses of Plasmodium yoelii and is applicable to other rodent malaria parasites.

Variation in response to antimalarial drugs and in pathogenicity of malaria parasites is of biologic and medical importance. Linkage mapping has led to ...

protocol-for-production-genetic-cross-rodent-malaria

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Immunology and Infection

15.1K vistas.  National Institutes of Health. Cruces genéticos de los parásitos de la malaria de roedores se llevan a cabo por la alimentación de dos parásitos genéticamente distintos a los mosquitos. Recombinante progenie clonada a partir de la sangre del ratón después de permitir que los mosquitos que pican ratones infectados. Este vídeo muestra cómo se producen los cruces genéticos de Plasmodium yoelii Y es aplicable a otros parásitos de roedores malaria.