Localization of VSAs during the intraerythrocytic developmental cycle.

Abstract

<p><b>A-C:</b> Representative immunofluorescence images of the indicated VSAs in different parasite developmental stages of clinical isolate #4 (<b>A</b>), 3D7 parasites (<b>B</b>), and free merozoites from isolate #1 (<b>C</b>). First row: Giemsa staining of the corresponding parasitic stage. Second row: Positive control serum obtained from a semi-immune patient. Third row: <i>Pf</i>EMP1-specific antibody, showing the presence of the protein in Maurer’s clefts over the entire time course (<b>A, B</b>). Third to eighth rows: 2TM proteins were exported into the host cell (12–36 hpi) during the trophozoite stage but remained inside the parasite in the schizont stage (48 hpi). Proteins of the RIFIN-A family frequently localized to Maurer’s clefts, particularly when using the α-RIF29n antiserum, and the erythrocyte membrane; STEVOR and <i>Pf</i>MC-2TM localized predominantly to the erythrocyte membrane (<b>A, B</b>). RIFIN and STEVOR proteins were also observed at the apical tip or at the merozoite membrane, respectively. Isolate #1 also exhibited <i>Pf</i>MC-2TM-specific fluorescence in free merozoites when using the α-P<i>f</i>MC-2TM-CT antiserum (<b>C</b>). All antibodies were visualized with Alexa488-conjugated secondary antibody (green), and nuclei were stained with DAPI (blue).</p