Rapid and Ultrasensitive Detection of Plasmodium spp. Parasites via the RPA-CRISPR/Cas12a Platform.

ABSTRACT

Microscopic examination of thick and thin blood smears stained with Giemsa dye is considered the primary diagnostic tool for the confirmation and management of suspected clinical malaria. However, detecting gametocytes is relatively insensitive, particularly in asymptomatic individuals with low-density Plasmodium infections. To complement existing diagnostic methods, a rapid and ultrasensitive point-of-care testing (POCT) platform for malaria detection is urgently needed and necessary. A platform based on recombinase polymerase amplification (RPA) followed by CRISPR/Cas12a (referred to as RPA-CRISPR/Cas12a) was developed and optimized for the determination of Plasmodium spp. parasites, particularly Plasmodium falciparum, using a fluorescence-based assay (FBDA), lateral flow test strips (LFTS), or naked eye observation (NEO). Then, the established platform was assessed with clinical malaria isolates. Under optimal conditions, the detection threshold was 1 copy/µL for the plasmid, and the limit of detection was 3.11-7.27 parasites/µL for dried blood spots. There was no cross-reactivity against blood-borne pathogens. For the accuracies of RPA-CRISPR/Cas12a, Plasmodium spp. and P. falciparum testing were 98.68 and 94.74%, respectively. The method was consistent with nested PCR results and superior to the qPCR results. RPA-CRISPR/Cas12a is a rapid, ultrasensitive, and reliable platform for malaria diagnosis. The platform requires no or minimal instrumentation for nucleic acid amplification reactions and can be read with the naked eye. Compared with similar diagnostic methods, this platform improves the reaction speed while reducing detection requirements. Therefore, this platform has the potential to become a true POCT for malaria parasites.