Agglutination Assays of the Plasmodium falciparum-Infected Erythrocyte

Abstract

The agglutination assay is used to determine the ability of antibodies to recognize parasite variant antigens on the surface of Plasmodium falciparum-infected erythrocytes. In this technique, infected erythrocytes are selectively labelled with a DNA-binding fluorescent dye and mixed with antibodies of interest to allow antibody-surface antigen binding. Recognition of surface antigens by the antibodies can result in the formation of agglutinates containing multiple parasite-infected erythrocytes. These can be viewed and quantified using a fluorescence microscope.

Keywords: Agglutination; Antibody; Infected erythrocytes; Malaria; Naturally acquired immunity; PfEMP1; Plasmodium falciparum; Variant surface antigens.

Fig. 1

An agglutinate stained with ethidium bromide in the individual agglutination assay. Agglutination was conducted on a culture-adapted parasite isolate using plasma from an adult from a malaria-endemic area

Fig. 2

An image of a mixed agglutinate captured using a single fluorescence channel. A culture-adapted parasite isolate was divided into two portions that were separately stained with DAPI (blue) or ethidium bromide (orange). Agglutination was conducted using plasma from an adult from a malaria-endemic area

Fig. 3

An image of single-color agglutinates in a mixed agglutination assay captured using a single fluorescence channel. Two distinct parasite isolates were either stained with DAPI (blue) or ethidium bromide (orange). Agglutination was conducted using plasma from an adult from a malaria-endemic area