Knob morphology in parasitized HbAA and HbAS erythrocytes. A Representative scanning electron microscopic images of HbAA and HbAS erythrocytes infected with the parental FCR3CSA strain and the G6 mutant encoding VAR2CSAmEOS2. Bar, 2 μm. The knobs displayed by G6 were comparable in terms of diameter and density with those found in erythrocytes infected with the parental FCR3 strain. In the case of the clonal NTS-mEOS2, mutant selected for further analysis, henceforth termed G6, RT-PCR of isolated mRNA confirmed transcription of the genetically altered var2csa gene and immunofluorescence assays of live-infected erythrocytes demonstrated surface labeling, using a monoclonal antibody specific to the DBL3-X domain of VAR2CSA.

Sanchez CP, Karathanasis C, Sanchez R, Cyrklaff M, Jäger J, Buchholz B, Schwarz US, Heilemann M, Lanzer M. Single-molecule imaging and quantification of the immune-variant adhesin VAR2CSA on knobs of Plasmodium falciparum-infected erythrocytes. Commun Biol. 2019 May 8;2(1):172.