Identification of binding domains on red blood cell glycophorins for Babesia divergens.
BACKGROUND
Invasion of red blood cells (RBCs) is one of the critical points in the lifecycle of Babesia. The parasite does not invade other host cells. Earlier work has shown that GPA and GPB function as putative receptors during parasite invasion. The primary focus of this study was the delineation of parasite-binding domains on GPA and GPB.


METHODS
The assay of choice to validate molecules that participate in invasion is an inhibition of invasion assay, in which changes in parasitemia are assessed relative to a wild-type assay (no inhibitors). Inhibition of invasion can be achieved by modification of different components of the assay or by the addition of competitors of the molecules that participate in invasion. In this study purified antibody fragments to various domains on GPA and GPB were tested for magnitude of inhibition of parasite invasion. Effects on invasion were monitored by assessment of Giemsa-stained smears every 24 hours.


RESULTS
Among 10 selected antibodies directed at various epitopes on GPA and GPB, antibodies directed against GPA(M) epitopes had the most severe effect (up to 35%) on inhibition of invasion, followed by antibodies directed against GPB(S) epitope (up to 24%).


CONCLUSIONS
This study confirms the role of RBC glycophorins A and B in Babesia divergens invasion and shows that the GPA(M) and GPB(S) epitopes are likely to play an important role in the entry process.
Department of Blood-Borne Parasites, Lindsley Kimball Research Institute, New York Blood Center, New York, New York.
Jeny R
JR
Cursino-Santos
Greg
G
Halverson
Marilis
M
Rodriguez
Mohandas
M
Narla
Cheryl A
CA
Lobo
D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D000918:Antibody Specificity; D001403:Babesia / Q000276:immunology* / Q000472:pathogenicity; D001404:Babesiosis / Q000276:immunology* / Q000469:parasitology*; D001665:Binding Sites; D002478:Cells, Cultured; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology; D004907:Erythrocyte Deformability / Q000276:immunology; D004912:Erythrocytes / Q000276:immunology* / Q000469:parasitology; D006021:Glycophorins / Q000276:immunology*; D006400:Hematocrit; D006801:Humans; D018512:Parasitemia / Q000276:immunology
D000913:Antibodies, Protozoan; D000939:Epitopes; C409972:GYPA protein, human; C409973:GYPB protein, human; D006021:Glycophorins