Authors thank Bloomberg Philanthropies for financial support to Johns Hopkins Malaria Research Institute (JHMRI). This work would not have been possible without the expertise provided by JHMRI insect and parasitology core facilities.

Blood collections described below have been approved by the Institutional Review Board of Johns Hopkins University. P. falciparum is cultured in fresh RBCs under sterile conditions in a biosafety level 2 (BSL2) facility and caution is used to handle biological materials. After each step involving blood or blood products, every plasticware or glassware is rinsed with 10% bleach within the hood prior to proper disposal.
1. Reagents and preparation
<ol>
	<li>Parasite isolate P. fal...

<ol>
	<li>World Health Organization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=World+Malaria+Report.">World Malaria Report.</a> World Health Organization. , (2018).</li><li>Sinden, R. E., Smalley, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gametocytogenesis+of+Plasmodium+falciparum+in+vitro:+The+cell-cycle.">Gametocytogenesis of Plasmodium falciparum in vitro: The cell-cycle.</a> Parasitology. 79 (2), 277-296 (1979).</li><li>Sinden, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sexual+Development+of+Malarial+Parasites.">Sexual Development of Malarial Parasites.</a> Advances in Parasitology. 22, 153-216 (1983).</li><li>Joice, R., 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=Plasmodium+falciparum+transmission+stages+accumulate+in+the+human+bone+marrow.">Plasmodium falciparum transmission stages accumulate in the human bone marrow.</a> Science Translational Medicine. 6 (244), 5 (2014).</li><li>Abdulsalam, A. H., Sabeeh, N., Bain, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immature+Plasmodium+falciparum+gametocytes+in+bone+marrow.">Immature Plasmodium falciparum gametocytes in bone marrow.</a> American Journal of Hematology. 85 (12), 943 (2010).</li><li>Ghosh, A. K., Jacobs-Lorena, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmodium+sporozoite+invasion+of+the+mosquito+salivary+gland.">Plasmodium sporozoite invasion of the mosquito salivary gland.</a> Current Opinion in Microbiology. 12 (4), 394-400 (2009).</li><li>Bennink, S., Kiesow, M. J., Pradel, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+development+of+malaria+parasites+in+the+mosquito+midgut.">The development of malaria parasites in the mosquito midgut.</a> Cellular Microbiology. 18 (7), 905-918 (2016).</li><li>Trager, W., Jenson, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cultivation+of+malarial+parasites.">Cultivation of malarial parasites.</a> Nature. 273 (5664), 621-622 (1978).</li><li>Duffy, S., Loganathan, S., Holleran, J. P., Avery, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-scale+production+of+Plasmodium+falciparum+gametocytes+for+malaria+drug+discovery.">Large-scale production of Plasmodium falciparum gametocytes for malaria drug discovery.</a> Nature Protocols. 11 (5), 976-992 (2016).</li><li>Delves, M. 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=Routine+in+vitro+culture+of+P.+Falciparum+gametocytes+to+evaluate+novel+transmission-blocking+interventions.">Routine in vitro culture of P. Falciparum gametocytes to evaluate novel transmission-blocking interventions.</a> Nature Protocols. 11 (9), 1668-1680 (2016).</li><li>Habtewold, T., 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=Streamlined+SMFA+and+mosquito+dark-feeding+regime+significantly+improve+malaria+transmission-blocking+assay+robustness+and+sensitivity.">Streamlined SMFA and mosquito dark-feeding regime significantly improve malaria transmission-blocking assay robustness and sensitivity.</a> Malaria Journal. 18 (1), 24 (2019).</li><li>Demanga, C. G., 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+development+of+sexual+stage+malaria+gametocytes+in+a+Wave+Bioreactor.">The development of sexual stage malaria gametocytes in a Wave Bioreactor.</a> Parasites and Vectors. 10 (1), 216 (2017).</li><li>Brockelman, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conditions+favoring+gametocytogenesis+in+the+continuous+culture+of+Plasmodium+falciparum.">Conditions favoring gametocytogenesis in the continuous culture of Plasmodium falciparum.</a> Journal of Eukaryotic Microbiology. 29, 454-458 (1982).</li><li>Meibalan, E., Marti, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biology+of+malaria+transmission.">Biology of malaria transmission.</a> Cold Spring Harbor Perspectives in Medicine. 7, (2017).</li><li>Essuman, E., 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=A+novel+gametocyte+biomarker+for+superior+molecular+detection+of+the+plasmodium+falciparum+infectious+reservoirs.">A novel gametocyte biomarker for superior molecular detection of the plasmodium falciparum infectious reservoirs.</a> Journal of Infectious Diseases. 216 (10), 1264-1272 (2017).</li><li>Sim&#245;es, M. L., Mlambo, G., Tripathi, A., Dong, Y., Dimopoulos, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immune+regulation+of+plasmodium+is+anopheles+species+specific+and+infection+intensity+dependent.">Immune regulation of plasmodium is anopheles species specific and infection intensity dependent.</a> mBio. 8 (5), 01631 (2017).</li><li>Oakley, M. 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=Transcriptome+analysis+based+detection+of+Plasmodium+falciparum+development+in+Anopheles+stephensi+mosquitoes.">Transcriptome analysis based detection of Plasmodium falciparum development in Anopheles stephensi mosquitoes.</a> Scientific Reports. 8, 11568 (2018).</li><li>Saraiva, R. G., 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=Chromobacterium+spp.+mediate+their+anti-Plasmodium+activity+through+secretion+of+the+histone+deacetylase+inhibitor+romidepsin.">Chromobacterium spp. mediate their anti-Plasmodium activity through secretion of the histone deacetylase inhibitor romidepsin.</a> Scientific Reports. 8, 6176 (2018).</li><li>Tao, 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=Sex-partitioning+of+the+Plasmodium+falciparum+stage+V+gametocyte+proteome+provides+insight+into+falciparum-specific+cell+biology.">Sex-partitioning of the Plasmodium falciparum stage V gametocyte proteome provides insight into falciparum-specific cell biology.</a> Molecular and Cellular Proteomics. 13 (10), 2705-2724 (2014).</li><li>Grabias, B., Zheng, H., Mlambo, G., Tripathi, A. K., Kumar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sensitive+enhanced+chemiluminescent-ELISA+for+the+detection+of+Plasmodium+falciparum+circumsporozoite+antigen+in+midguts+of+Anopheles+stephensi+mosquitoes.">A sensitive enhanced chemiluminescent-ELISA for the detection of Plasmodium falciparum circumsporozoite antigen in midguts of Anopheles stephensi mosquitoes.</a> Journal of Microbiological Methods. 108, 19-24 (2015).</li><li>Ferrer, P., Vega-Rodriguez, J., Tripathi, A. K., Jacobs-Lorena, M., Sullivan, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antimalarial+iron+chelator+FBS0701+blocks+transmission+by+Plasmodium+falciparum+gametocyte+activation+inhibition.">Antimalarial iron chelator FBS0701 blocks transmission by Plasmodium falciparum gametocyte activation inhibition.</a> Antimicrobial Agents and Chemotherapy. 59 (3), 1418-1426 (2015).</li><li>Sanders, N. G., Sullivan, D. J., Mlambo, G., Dimopoulos, G., Tripathi, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gametocytocidal+screen+identifies+novel+chemical+classes+with+Plasmodium+falciparum+transmission+blocking+activity.">Gametocytocidal screen identifies novel chemical classes with Plasmodium falciparum transmission blocking activity.</a> PLoS One. 9 (8), 105817 (2014).</li><li>Lindner, S. E., 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=Transcriptomics+and+proteomics+reveal+two+waves+of+translational+repression+during+the+maturation+of+malaria+parasite+sporozoites.">Transcriptomics and proteomics reveal two waves of translational repression during the maturation of malaria parasite sporozoites.</a> Nature Communications. 10, 4964 (2019).</li><li>McLean, K. 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=Generation+of+Transmission-Competent+Human+Malaria+Parasites+with+Chromosomally-Integrated+Fluorescent+Reporters.">Generation of Transmission-Competent Human Malaria Parasites with Chromosomally-Integrated Fluorescent Reporters.</a> Scientific Reports. 9, 13131 (2019).</li><li>Espinosa, D. A., 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=Proteolytic+Cleavage+of+the+Plasmodium+falciparum+Circumsporozoite+Protein+Is+a+Target+of+Protective+Antibodies.">Proteolytic Cleavage of the Plasmodium falciparum Circumsporozoite Protein Is a Target of Protective Antibodies.</a> Journal of Infectious Diseases. 212 (7), 1111-1119 (2015).</li><li>Swearingen, K. E., 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=Interrogating+the+Plasmodium+Sporozoite+Surface:+Identification+of+Surface-Exposed+Proteins+and+Demonstration+of+Glycosylation+on+CSP+and+TRAP+by+Mass+Spectrometry-Based+Proteomics.">Interrogating the Plasmodium Sporozoite Surface: Identification of Surface-Exposed Proteins and Demonstration of Glycosylation on CSP and TRAP by Mass Spectrometry-Based Proteomics.</a> PLoS Pathogens. 12 (4), 1005606 (2016).</li><li>Ifediba, T., Vanderberg, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complete+in+vitro+maturation+of+Plasmodium+falciparum+gametocytes.">Complete in vitro maturation of Plasmodium falciparum gametocytes.</a> Nature. 294 (5839), 364-366 (1981).</li><li>Miura, 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=An+inter-laboratory+comparison+of+standard+membrane-feeding+assays+for+evaluation+of+malaria+transmission-blocking+vaccines.">An inter-laboratory comparison of standard membrane-feeding assays for evaluation of malaria transmission-blocking vaccines.</a> Malaria Journal. 15, 463 (2016).</li><li>Miura, 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=Qualification+of+Standard+Membrane-Feeding+Assay+with+Plasmodium+falciparum+Malaria+and+Potential+Improvements+for+Future+Assays.">Qualification of Standard Membrane-Feeding Assay with Plasmodium falciparum Malaria and Potential Improvements for Future Assays.</a> PLoS One. 8 (3), 57909 (2013).</li></ol>

Methods described here have been successfully used at the Johns Hopkins Malaria Research Institute for more than 10 years15,16,17,18,19,20,21,22. Gametocytes produced using this protocol have been used for high throughput gametocytocidal assays<sup class="x...

Malaria is caused by Plasmodium parasites and is transmitted to their vertebrate hosts via infectious bite of female Anopheles mosquitoes. According to the 2019 World Health Organization (WHO) report, there were an estimated 405,000 deaths, from a total of 228 million cases of malaria1. Most of the malaria related deaths were concentrated in the African region, especially among children below five years of age. While the overall incidence rate of malaria has declined globally from 2010, in recent years decline has plateaued and additional control strategies are urgently needed to eliminate the disease.
Cyclic asexual blood stages of malaria parasites cause disease pathogenesis and a small subset of these differentiate into female and male gametocytes. Plasmodium falciparum&#160;gametocytes are unique in nature as they take 7-10 days to develop through five morphologically distinct stages. Immature gametocytes from stage I to IV are sequestered in bone marrow parenchyma and largely remain absent from peripheral circulation2,3,4,5. Erythrocytes infected with mature stage V gametocytes are released in the bloodstream and freely circulate to be taken up by mosquitoes. Once inside the mosquito midgut, gametocytes are activated, through a change in temperature and exposure to the midgut environment, transform into female and male gametes and begin development of the mosquito stages, which culminates with the infective stages of sporozoites in the mosquito salivary glands6,7.
Since Trager and Jenson8 described a standardized method to culture P. falciparum, studies on the asexual blood stages have greatly advanced. However, the lack of a reliable culture system for sexual stages has made it difficult to study P. falciparum gametocytes, transmission biology and mosquito stages. In recent years, several methods have been published which have aided laboratories in establishing gametocyte cultures9,10,11,12. This manuscript describes standardized and reliable protocol to culture P. falciparum gametocytes that can represent a valuable resource for the malaria research community. This method enables the robust production of mature and infectious gametocytes which along with a standardized mosquito feeding protocol, results in highly reliable mosquito infectivity. These methods were established to maintain uninterrupted supply of gametocytes, and mosquito stage parasites. In this manuscript, we describe a thorough gametocyte culture protocol (Figure 1), preparation of glass membrane feeders and infection of mosquitoes using these membrane feeders (Figure 2), dissection of midgut (Figure 3) and salivary gland of mosquitoes (Figure 4), and quantification of infection in mosquito after midgut and salivary gland dissection.

<table>
	<tbody>
		<tr>
			<td>10% Sugar solution</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>10ml serological pipet</td>
			<td>Falcon</td>
			<td>357551</td>
			<td></td>
		</tr>
		<tr>
			<td>15 ml conical tube</td>
			<td>Falcon</td>
			<td>352096</td>
			<td></td>
		</tr>
		<tr>
			<td>1ml serological pipet</td>
			<td>Falcon</td>
			<td>357521</td>
			<td></td>
		</tr>
		<tr>
			<td>25 ml serological pipet</td>
			<td>Falcon</td>
			<td>357535</td>
			<td></td>
		</tr>
		<tr>
			<td>37&#176;C Incubator</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml conical tube</td>
			<td>Falcon</td>
			<td>352070</td>
			<td></td>
		</tr>
		<tr>
			<td>5ml serological pipet</td>
			<td>Falcon</td>
			<td>357543</td>
			<td></td>
		</tr>
		<tr>
			<td>6 well tissue culture plates</td>
			<td>Falcon</td>
			<td>353046</td>
			<td></td>
		</tr>
		<tr>
			<td>70% Ethanol</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>9&#34; glass pipet</td>
			<td>Fisherbrand</td>
			<td>13-678-6B</td>
			<td></td>
		</tr>
		<tr>
			<td>Anopheles Mosquitoes</td>
			<td>JHMRI, Insectary core</td>
			<td></td>
			<td>We use A. stephensi or A. gambiae (keele)</td>
		</tr>
		<tr>
			<td>cell counter</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Circulating water bath</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>fine tip forceps</td>
			<td>Fisherbrand</td>
			<td>12-000-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Geimsa stain</td>
			<td>Sigma</td>
			<td>GS1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass desiccator</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass membrane feeder</td>
			<td>Chemglass Life Sciences</td>
			<td>CG183570</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass slides</td>
			<td>Fisherbrand</td>
			<td>12-552-3</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS</td>
			<td>Sigma</td>
			<td>H6648</td>
			<td></td>
		</tr>
		<tr>
			<td>Human Blood O+</td>
			<td>JHU</td>
			<td></td>
			<td>Wash RBCs three times with RPMI and refrigerate at 50% heamatocrit</td>
		</tr>
		<tr>
			<td>Human Serum O+</td>
			<td>Interstate blood bank</td>
			<td></td>
			<td>Pool at-least 6 units of serum from different donors and freeze down aliquots at -20&#176;C.</td>
		</tr>
		<tr>
			<td>Hypoxanthine</td>
			<td>Sigma</td>
			<td>H9337</td>
			<td>Make 500x stock in 1M NaOH</td>
		</tr>
		<tr>
			<td>Mercurochrome</td>
			<td>Sigma</td>
			<td>M7011</td>
			<td>Prepare 1% stock solution in PBS that can be diluted to 0.1% when needed</td>
		</tr>
		<tr>
			<td>Micro Pipette</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Olympus</td>
			<td></td>
			<td>Any microscope with 10x, 40x and 100x objective will work.</td>
		</tr>
		<tr>
			<td>Mosquito cups</td>
			<td>Neptune cups</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>N-acetylglucosamine</td>
			<td>Sigma</td>
			<td>A3286</td>
			<td>Optional and needed only when pure gametocytes are required.</td>
		</tr>
		<tr>
			<td>Netting</td>
			<td></td>
			<td></td>
			<td>Make sure it can contain mosquitoes and allow blood feeding</td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>Thermo Scientific</td>
			<td>249964</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipet tips</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plasmodium falciparum NF54</td>
			<td>BEI Resources</td>
			<td>MRA-1000</td>
			<td>Freeze down large numbers of early passage culture to make sure you have a constant supply</td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>Corning</td>
			<td>CV-041-CV</td>
			<td>Media contains glutamine and HEPES</td>
		</tr>
		<tr>
			<td>Slide warmer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium bicarbonate</td>
			<td>Sigma</td>
			<td>S6297</td>
			<td>Optional for media, add only when using malaria gas mix during culture incubation</td>
		</tr>
		<tr>
			<td>water bath</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Xanthurenic Acid</td>
			<td>Sigma</td>
			<td>D120804</td>
			<td>For flagellation media</td>
		</tr>
	</tbody>
</table>

plasmodium falciparum gametocyte culture and mosquito infection through artificial membrane feeding

Malaria remains one of the most important public health problems, causing significant morbidity and mortality. Malaria is a mosquito borne disease transmitted through an infectious bite from the female Anopheles mosquito. Malaria control will eventually rely on a multitude of approaches, which includes ways to block transmission to, through and from mosquitoes. To study mosquito stages of malaria parasites in the laboratory, we have optimized a protocol to culture highly infectious Plasmodium falciparum gametocytes, a parasite stage required for transmission from the human host to the mosquito vector. P. falciparum gametocytes mature through five morphologically distinct steps, which takes approximately 1-2 weeks. Gametocyte culture described in this protocol is completed in 15 days and are infectious to mosquitoes from days 15-18. These protocols were developed to maintain a continuous cycle of infection competent gametocytes and to maintain uninterrupted supply of mosquito stages of the parasite. Here, we describe the methodology of gametocyte culture and how to infect mosquitoes with these parasites using glass membrane feeders.

Here we present results from a series of membrane feeds using P. falciparum NF54 gametocyte cultures generated using the protocol above (see (Figure 5). Gametocyte culture was initiated with approximately 0.5% mixed stage asexual culture on Day 0, which grew to a peak parasitemia of approximately 15% by Day 4 and Day 5. As shown in Figure 5A at this high parasitemia, the parasites are stressed and the asexual stage culture crashes. However, this stress ...

Watch this Scientific Journal Video about Plasmodium falciparum Gametocyte Culture and Mosquito Infection Through Artificial Membrane Feeding at JoVE.com

Plasmodium falciparum Gametocyte Culture and Mosquito Infection Through Artificial Membrane Feeding

Detailed investigations on mosquito stages of malaria parasites are critical to design effective transmission blocking strategies. This protocol demonstrates how to effectively culture infectious gametocytes and then feed these gametocytes to mosquitoes to generate mosquito stages of P. falciparum.

Plasmodium falciparum Gametocyte Culture and Mosquito Infection Through Artificial Membrane Feeding

Malaria remains one of the most important public health problems, causing significant morbidity and mortality. Malaria is a mosquito borne disease ...

Gametocytes are responsible for malaria parasite transmission. Generating infectious gametocytes in the lab is key to studying transmission biology in mosquito stages and to generating sporozoites for later-stage results. These methods are simple for any laboratory to adopt, and visual demonstration will aid in the sharing of these procedures with the world-wide malaria community.Demonstrating the procedure with me will be my colleagues, Godfree Mlambo, our senior research associate, and Sachie Kanatani, our postdoctoral fellow, both from the Johns Hopkins Malaria Research Institute. To set up a gametocyte culture, spin down five milliliters of feeder culture in a centrifuge, and re-suspend the pellet in 30 milliliters of complete medium. Mix 1.2 milliliters of packed red blood cells with the tube contents, and add five milliliters of the resulting suspension to each well of a six-well culture plate.Then place the plate in a candle jar at 37 degrees Celsius. Every day for the next 15 to 18 days, carefully aspirate 70 to 80%of the culture supernatant from each well and use a serological pipette to add five milliliters of fresh medium without blood cells down the wall of each well to feed the cultures without disturbing the settled red blood cell layer. To quantify mature gametocytemia, on day 15 to 18, make a blood smear, and count the number of matured gametocytes in a minimum of 1000 red blood cells to allow calculation of the percentage of mature, gametocyte-infected red blood cells.To quantify the exflagellation events, centrifuge 200 microliters of the gametocyte culture in a pre-warmed tube, and re-suspend the pellet in 20 microliters of exflagellation medium. Transfer the gametocyte suspension to a glass slide with a cover slip, and incubate the slide for 15 minutes at room temperature. At the end of the incubation, use a 10X objective to count the exflagellation centers in phase contrast mode in at least four fields to allow calculation of the exflagellation events.To infect mosquitoes using the standard membrane feeding assay, remove the sugar water from a three to seven-day-old female anopheles mosquito cage for 6.5 to 18 hours, and use an aspirator to transfer up to 100 mosquitoes into individual paper cups covered with a double-layer of fine mesh fabric. Collect the washed blood by centrifugation, and reconstitute the blood with an equal volume of freshly-thawed human serum. Pre-warm reconstituted blood in a 37-degrees Celsius water bath for 30 minutes, transfer the gametocyte culture into pre-warmed, 15-milliliter plastic tubes for centrifugation, and make a thin blood smear of the pellet to determine the mature gametocytemia as demonstrated.To make the final blood feed, use reconstituted whole blood to dilute the gametocyte pellet to the appropriate experimental concentration, and place the blood feed at 37 degrees Celsius until the mosquitoes and glass feeders are ready. Stretch a square piece of paraffin film to an even thickness and place the film over the top opening of the feeder to create a sealed compartment for the blood feed. Use a connecting tube on each side to attach the membrane feeder to a circulatory water bath to allow the passage of warm water through the jacket around the feeder.When all of the feeders for the experiment have been connected, turn on the bath and check all of the equipment for leaks. Place the feeders in the center of the netting on the mosquito cups, membrane side down, and secure the feeders to the netting in an upright position. When all of the feeders have been optimally positioned, add 200 to 1000 microliters of blood feed to each membrane feeder, and check that the feed has been properly overlaid onto the paraffin film.After about 30 minutes of feeding with intermittent monitoring, knock down the mosquitoes in a cold room and visibly inspect the insects for bulge and redness in the abdomen. Place the fed mosquitoes back into the mosquito cups, and place cotton pads soaked in 10%sucrose on the mosquito cups to provide them with a sugar meal and then double-cage the cups to secure infected mosquitoes, then transfer the mosquitoes to a high-containment incubator specifically for mosquitoes infected with the human malaria parasite, P.falciparum. To harvest the midguts from the infected mosquitoes, pipette 100 microliters of PBS into the center of a glass slide mounted onto a dissecting microscope stage, and use forceps to carefully transfer one mosquito into the PBS.Use fine-tipped forceps to grasp the segment of the abdomen from the posterior end of the mosquito, and use a second pair of forceps to hold the junction between the thorax and the abdomen, then gently pull the abdomen until the midgut is fully exposed. When all of the mosquitoes have been dissected in the same manner, use a pipette to carefully remove the PBS, and stain in the midguts with 0.2%Mercurochrome for two to five minutes. At the end of the incubation, remove the excess dye, and line the midguts on the slide for easy visualization under a light microscope, then place a cover slip over the midguts and count the number of oocysts in each midgut under the 10X objective.For salivary gland harvest, place the mosquitoes in a glass plate under a dissecting microscope in just enough medium to keep the mosquito tissue hydrated and use two syringes equipped with 25-gauge needles to grasp mosquito thorax and head. Gently pull the head upward to pull the salivary glands from the thorax, and use a needle to disconnect the salivary glands from the head and thorax. When 15 to 20 salivary glands have been collected, use a Pasteur pipette to transfer the glands to a low-retention tube, and pellet the glands by a short pull spin in a tabletop centrifuge.Re-suspend the salivary gland in 100 microliters of fresh dissection medium, and use a small homogenizer to grind the salivary glands for one minute to release the sporozoites, then count the number of sporozoites in 10 microliters of dissection medium in two quadrants of a hemocytometer. Here, a time course of P.falciparum NF54 gametocyte culture growth, as demonstrated, can be observed. The gametocyte culture was initiated with an approximately 0.5%mixed-stage asexual culture on day zero that grew to a peak parasitemia of approximately 15%by days four and five.At this high parasitemia, the parasites are stressed, resulting in crashing of the asexual stage culture. This stress, however, results in the induction of gametocytogenesis, with early gametocytes appearing around day six to seven, and asexual parasitemia slowly declining while remaining at a low level. The majority of the gametocytes matured to stage five by day 15, at which point they become infectious to mosquitoes and are ready to be fed.These representative images of Giemsa's stain blood smears show gametocyte culture progression at different time points after gametocyte culture initiation. Here, results from series-of-membrane feeds using P.falciparum NF54 gametocytes generated using this protocol can be observed. Between 8 to 10 days after blood feeding, the number of oocysts varies both within and between experiments, and requires 25 to 50 mosquitoes per cohort to determine the effects of various experimental conditions.As shown in the table, overall, the average number of sporozoites in this analysis was consistent. However, there was one experiment in which zero sporozoites were obtained, illustrating the occasional failure of the assay. The success of this protocol depends on how well the gametocytes infect the mosquitoes.Keeping the gametocytes as still as possible when changing the medium during the two-week culture helps. Using these methods, laboratories can perform studies on gametocyte biology, transmission blocking, vector and parasite interactions, and the sporozoite stages.

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Research

JoVE Journal

Biology

7.1K visualizações.  Johns Hopkins University. Gametocytes are responsible for malaria parasite transmission. Generating infectious gametocytes in the lab is key to studying transmission biology in mosquito stages and to generating sporozoites for later-stage results. These methods are simple for any laboratory to adopt, and visual demonstration will aid in the sharing of these procedures with the world-wide malaria community.Demonstrating the procedure with me will be my colleagues, Godfree Mlambo, our senior research associate, a...