Cellular localization of Babesia bovis merozoite rhoptry-associated protein 1 and its erythrocyte-binding activity.
The cellular localization of Babesia bovis rhoptry-associated protein 1 (RAP-1) and its erythrocyte-binding affinity were examined with anti-RAP-1 antibodies. In an indirect immunofluorescent antibody test, RAP-1 was detectable in all developmental stages of merozoites and in extracellular merozoites. In the early stage of merozoite development, RAP-1 appears as a dense accumulation, which later thins out and blankets the host cell cytoplasm, but retains a denser mass around newly formed parasite nuclei. The preferential accumulations of RAP-1 on the inner surface of a host cell membrane and bordering the parasite's outer surface were demonstrable by immunoelectron microscopy. An erythrocyte-binding assay with the lysate of merozoites demonstrated RAP-1 binding to both bovine and equine erythrocytes. Anti-RAP-1 monoclonal antibody 1C1 prevented the interaction of RAP-1 with bovine erythrocytes and significantly inhibited parasite proliferation in vitro. With the recombinant RAP-1, the addition of increasing concentrations of Ca(2+) accentuated its binding affinity with bovine erythrocytes. The present findings lend support to an earlier proposition of an erythrocytic binding role for RAP-1 expressed in B. bovis merozoites and, possibly, its involvement in the escape of newly formed merozoites from host cells.
Yokoyama
Naoaki
N
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.
Suthisak
Boonchit
B
Hirata
Haruyuki
H
Matsuo
Tomohide
T
Inoue
Noboru
N
Sugimoto
Chihiro
C
Igarashi
Ikuo
I
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000913:Antibodies, Protozoan / Q000494:pharmacology; D016793:Babesia bovis / Q000235:genetics / Q000254:growth & development / Q000276:immunology / Q000378:metabolism*; D001404:Babesiosis / Q000469:parasitology / Q000662:veterinary; D001483:Base Sequence; D002417:Cattle; D002418:Cattle Diseases / Q000469:parasitology; D016054:DNA, Protozoan / Q000235:genetics; D004912:Erythrocytes / Q000469:parasitology*; D017125:Genes, Protozoan; D006736:Horses; D066298:In Vitro Techniques; D011485:Protein Binding; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000913:Antibodies, Protozoan; D016054:DNA, Protozoan; D015800:Protozoan Proteins; C097551:rhoptry-associated protein-1, Babesia