Summary

フローサイトメトリーによるげっ歯類マラリア原虫のin vivo評価とメロゾイト侵略

Published: April 05, 2015
doi:

Summary

マラリア原虫が侵入し、赤血球内で複製する。メロゾイトの侵入および寄生虫の正確な評価は、マラリア感染の経過を評価するので、非常に重要です。ここでは、マラリアのマウスモデルにおいて、これらのパラメータを測定するためのフローサイトメトリーベースのプロトコルを説明する。

Abstract

During blood stage infection, malaria parasites invade, mature, and replicate within red blood cells (RBCs). This results in a regular growth cycle and an exponential increase in the proportion of malaria infected RBCs, known as parasitemia. We describe a flow cytometry based protocol which utilizes a combination of the DNA dye Hoechst, and the mitochondrial membrane potential dye, JC-1, to identify RBCs which contain parasites and therefore the parasitemia, of in vivo blood samples from Plasmodium chabaudi adami DS infected mice. Using this approach, in combination with fluorescently conjugated antibodies, parasitized RBCs can be distinguished from leukocytes, RBC progenitors, and RBCs containing Howell-Jolly bodies (HJ-RBCs), with a limit of detection of 0.007% parasitemia. Additionally, we outline a method for the comparative assessment of merozoite invasion into two different RBC populations. In this assay RBCs, labeled with two distinct compounds identifiable by flow cytometry, are transfused into infected mice. The relative rate of invasion into the two populations can then be assessed by flow cytometry based on the proportion of parasitized RBCs in each population over time. This combined approach allows the accurate measurement of both parasitemia and merozoite invasion in an in vivo model of malaria infection.

Introduction

The clinical symptoms associated with malaria occur during the Plasmodium parasite’s asexual replicative cycle within red blood cells (RBCs). Merozoites, released during the liver stage of infection, quickly attach to and invade RBCs. After gaining entry into the cell, the parasite grows and matures, eventually undergoing schizogony, splitting open the cell, and releasing a cluster of newly formed merozoites which go on to repeat this cycle. As such, an assessment of malaria infection often involves monitoring both parasitemia, which is the percentage of RBCs appropriated by one or more parasites, and the rate of merozoite invasion into uninfected RBCs.

Flow cytometry is a powerful tool which can be used to record the properties of vast numbers of cells in a short period of time. This technique has clear applicability for the measurement of malaria parasitemia and invasion, and offers several advantages over traditional microscopy techniques. These include the accurate measurement of very low parasitemia, which would be prohibitively time consuming by microscopy, the unbiased nature of the measurement, and the ability to measure multiple cell parameters simultaneously. Flow cytometry is widely used to determine both parasitemia and merozoite invasion in in vitro culture1-9, however, techniques for measuring these parameters in vivo are less well developed, and can be complicated by the presence of additional cell types which interfere with analysis. No assays have been described for measurement of in vivo invasion, and while some assays exist for the analysis of in vivo parasitemia, these lack the ability to distinguish between parasitized RBCs (pRBCs) and RBCs containing Howell-Jolly bodies (HJ-RBCs)10-13. The later issue is particularly important as in mice HJ-RBCs may account for up to 0.9% of mature RBCs14-16, thereby preventing the accurate measurement of low parasitemia.

We have previously demonstrated an approach for the measurement of parasitemia and merozoite invasion in a rodent model of malaria infection14. Here, we provide a more detailed protocol and accompanying video. This approach builds on previous methodologies and allows for the accurate identification of parasitized RBCs, as distinct from leukocytes, RBC progenitors, and HJ-RBCs. Additionally, this assay allows the simultaneous measurement of merozoite invasion into two labeled RBC populations, a treated, or target, population, and a control population, thereby providing a robust platform for the assessment of invasion into different cell types.

Protocol

すべての手順は、マッコーリー大学の方針に従って行われ、国立保健医療研究評議会(NHMRC)練習のオーストラリアのコードに適合​​した。仕事はなしARAが2012/017承認されておらず、マッコーリー大学の動物倫理委員会から得た同意の倫理で行った。特に明記しない限り、全ての実験は、SJL / Jマウスで行った。 1.マウスおよび実験マラリア感染 12:12時間の明暗サイクルで制御…

Representative Results

寄生虫の測定。 寄生虫血の測定のために、血液細胞が最初に選択されるべきであり、ノイズ、破片および血小板は、FSC / SSCの特性( 図2A)に基づいて、除外した。使用するフローサイトメーターに応じて、単一の細胞を、次いで、面積比( 図2C)のいずれかでトリガーパルス幅( 図2B)、またはFSCピーク高さに基づいて選択されるべ?…

Discussion

我々は、in vivoでのサンプルの両方寄生虫およびメロゾイトの侵入を測定するための方法を記載している。寄生虫血の測定に関しては、この方法は、それによって偽陽性事象の数を減少させる、PRBCを区別することができるHJ-赤血球における以前の方法10-13に優る利点を提供する。 HJ-RBCは、ヒトでは通常まれですが、いくつかの研究では、これらの細胞とげっ歯類寄生虫の正確な…

Disclosures

The authors have nothing to disclose.

Acknowledgements

私たちは、国立保健医療研究評議会(APP605524、490037と1047082を付与)、オーストラリア研究会議(DP12010061を付与)、オーストラリア国立共同研究インフラ戦略とイノベーション省から教育投資ファンド、産業界からの支援に資金を提供しアクノリッジ、科学·研究。 PMLは、オーストラリアの大学院賞を受賞です。

Materials

bisBenzimide H 33342 trihydrochloride Sigma-Aldrich B2261 Hoechst 33342. Store a 4mM stock solution at -20 °C in distilled water
Hoechst 34580 Sigma-Aldrich 63493 Store a 2mM stock solution at -20 °C in distilled water
JC-1 Dye Life Technologies T-3168 Store small aliquots of 6mM stock solution at -20 °C in DMSO
Anti-Mouse CD45 APC-eFluor 780 eBioscience 47-0451-80 Clone 30-F11
Anti-Mouse CD71 PerCP-eFluor 710 eBioscience 46-0711-80 Clone R17217
Atto 633 NHS ester Sigma-Aldrich 1464 Atto 633-NHS. Store a 2mg/ml stock solution at -20 °C in DMF
EZ-Link Sulfo-NHS-LC-Biotin Thermo Fisher Scientific 21335 Biotin-NHS. Store a 25mg/ml stock solution at -20 °C in DMF
Streptavidin PE-Cyanine7 eBioscience 25-4317-82 Streptavidin PE-Cy7
Heparin Sigma-Aldrich H478
35µM filter cap tubes Becton Dickinson 352235
Flow cytometer: BD LSRFortessa Becton Dickinson
Flow cytometer: BD FACSAria II Becton Dickinson
Flow cytometer: BD Influx Becton Dickinson
Flow cytometer: CyAn ADP Analyzer Beckman Coulter

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Cite This Article
Lelliott, P. M., McMorran, B. J., Foote, S. J., Burgio, G. In Vivo Assessment of Rodent Plasmodium Parasitemia and Merozoite Invasion by Flow Cytometry. J. Vis. Exp. (98), e52736, doi:10.3791/52736 (2015).

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