Highly Sensitive and Rapid Characterization of the Development of Synchronized Blood Stage Malaria Parasites Via Magneto-Optical Hemozoin Quantification

Abstract

The rotating-crystal magneto-optical diagnostic (RMOD) technique was developed as a sensitive and rapid platform for malaria diagnosis. Herein, we report a detailed in vivo assessment of the synchronized Plasmodium vinckei lentum strain blood-stage infections by the RMOD method and comparing the results to the unsynchronized Plasmodium yoelii 17X-NL (non-lethal) infections. Furthermore, we assess the hemozoin production and clearance dynamics in chloroquine-treated compared to untreated self-resolving infections by RMOD. The findings of the study suggest that the RMOD signal is directly proportional to the hemozoin content and closely follows the actual parasitemia level. The lack of long-term accumulation of hemozoin in peripheral blood implies a dynamic equilibrium between the hemozoin production rate of the parasites and the immune system’s clearing mechanism. Using parasites with synchronous blood stage cycle, which resemble human malaria parasite infections with Plasmodium falciparum and Plasmodium vivax, we are demonstrating that the RMOD detects both hemozoin production and clearance rates with high sensitivity and temporal resolution. Thus, RMOD technique offers a quantitative tool to follow the maturation of the malaria parasites even on sub-cycle timescales.

Magneto-optical diagnosis of symptomatic malaria in Papua New Guinea

“…Measurements on parasite cultures indicated that RMOD had a limit of detection (LOD) of ∼10 parasites per µL of blood in samples spiked with P. falciparum 26 . These promising results were further supported by studies on P. berghei and P. yoelii-infected mice 23,24 . On an operational level, RMOD is promising as it can be conducted after a short training and provide test results within minutes.…”

“…Rotating magneto-optical detection (RMOD) measurements. The concept of the rotating-crystal magneto-optical setup and the underlying physical principles of hemozoin detection are described in detail in our former studies [24][25][26] . The working principle is depicted in Fig.…”

“…Several approaches to exploit these magnetic properties for diagnostic purposes have been proposed [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and some of these techniques showed promise under laboratory conditions. However, only a few magneto-optical (MO) methods have been tested in operational settings in malaria endemic countries or with samples collected from malaria-infected patients in endemic countries.…”

“…PNG has a complex malaria epidemiology and the study area exhibits high transmission intensities for both, P. falciparum and P. vivax 38 . Using a RMOD prototype device similar to that described in our previous studies [23][24][25][26] , we systematically compared RMOD performance to conventional diagnostic techniques, namely expert LM, RDT, and PCR. Figure 1 provides an overview of the study site and population (Fig.…”

Rapid and quantitative antimalarial drug efficacy testing via the magneto-optical detection of hemozoin

“…For the 0.5% chloroquine assay, the following sampling point were applied after assay initiation: 8, 10, 12, 14, 16, 18, 20, 24, 32, 40 and 48 h. In the case of the 0.1% and 1% parasitemia piperaquine assays, sampling was carried out after 6, 8 and 10 h of incubation, and finally in case of the 1% parasitemia W2 strain treated with chloroquine, sampling took place 24 and 48 h after assay initiation. The scheme of the RMOD setup, as well as the underlying physical principles of the detection, are described in detail in our former studies [15][16][17] . Reproduction of this experimental scheme is possible by following the described details.…”