Morphological Characterization and Identification of Conserved Plasmodium Blood Stage Proteins in Colpodella sp., Free-living Relatives of Apicomplexons

Document Type

Conference Proceeding

Publication Date


Publication Title

American Journal of Tropical Medicine and Hygiene


Colpodella sp. are the closest free-living ancestors of the apicomplexan phylum which contains important human pathogens such as Plasmodium falciparum and Toxoplasma gondii, causative agents of malaria and toxoplasmosis, respectively. Colpodella-like parasites infecting erythrocytes were reported in a human infection marked by low natural killer cells and anemia. Colpodella sp. possess a pseudoconoid, rhoptries, micronemes and in some species trichocysts at the apical end of the trophozoite. In a process similar to merozoite invasion in P. falciparum, contents of the rhoptries are emptied during myzocytosis. In this study, we investigated the morphological characteristics of Colpodella sp. using different staining techniques for light microscopy. Transmission electron microscopy was also performed for ultrastructural characterization. Antibodies specific to Plasmodium blood stage proteins were used in immunofluorescence assay. Colpodella trophozoites and cysts were stained by Giemsa, Wright’s, Sudan IV, Picro-Sirius, Alum Carmine and hematoxylin and eosin (H&E) staining. We compared the clarity of morphological characteristics such as delineation of flagella, cytoplasmic structures, cyst features and the attachment junction formed during myzocytosis. Trophozoites and cysts were distinguished by all dyes except Alum Carmine and Sudan IV. Antibodies recognized several blood stage antigens including the high molecular weight rhoptry protein RhopH3 and SERA1. DNA sequencing of a polymerase chain reaction (PCR) amplified product obtained using primers targeting the P. falciparum RhopH3 gene confirmed the presence of RhopH3 in Colpodella sp. A combination of staining, immunological and molecular protocols can be used to further investigate Colpodella sp. to gain insights regarding the potential for Colpodellid protists to be opportunistic human pathogens.


Abstract 1692