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Infection and Immunity, April 2000, p. 1964-1966, Vol. 68, No. 4
EntreMed, Inc., Rockville, Maryland
208501; Department of Immunology, Walter
Reed Army Institute of Research, Washington, D.C.
20307-51002; Malaria Program, Naval
Medical Research Center, Rockville, Maryland
208523; and Department of Microbiology
and Immunology, University of Maryland School of Medicine,
Baltimore, Maryland 212014
Received 24 September 1999/Returned for modification 28 October
1999/Accepted 30 December 1999
The 175-kDa Plasmodium falciparum erythrocyte binding
protein (EBA-175) binds to its receptor, sialic acids on glycophorin A. The binding region within EBA-175 is a cysteine-rich region identified
as region II. Antibodies against region II block the binding
of native EBA-175 to erythrocytes. We identified a P. falciparum strain, FVO, that could not invade erythrocytes devoid of sialic acids due to prior neuraminidase treatment, and in addition, we used a strain, 3D7, that could invade such sialic acid-depleted erythrocytes. We used these two strains to study the capacity of
anti-region II antibodies to inhibit FVO and 3D7 parasite development in vitro. Analysis of growth-inhibitory effects of purified FVO anti-region II immunoglobulin G (IgG) with the FVO and 3D7 strains resulted in similar levels of growth inhibition. FVO and 3D7 strains were inhibited between 28 and 56% compared to control IgG.
There appeared to be no intracellular growth retardation or killing of
either isolate, suggesting that invasion was indeed inhibited. Incubation of recombinant region II with anti-region II IgG
reversed the growth inhibition. These results suggest that antibodies
against region II can also interfere with merozoite
invasion pathways that do not involve sialic acids. The fact that
EBA-175 has such a universal and yet susceptible
role in erythrocyte invasion clearly supports its inclusion in a
multivalent malaria vaccine.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Antibodies against the Plasmodium
falciparum Receptor Binding Domain of EBA-175 Block Invasion
Pathways That Do Not Involve Sialic Acids
*
Corresponding author. Mailing address: EntreMed, Inc.,
9640 Medical Center Dr., Rockville, MD 20850. Phone: (301) 217-9858. Fax: (301) 217-9594. E-mail: kims{at}entremed.com.
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