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Clinical and Diagnostic Laboratory Immunology, July 2000, p. 607-611, Vol. 7, No. 4
1071-412X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Enzyme-Linked Immunosorbent Assays Using the Recombinant Dense Granule Antigens GRA6 and GRA1 of Toxoplasma gondii for Detection of Immunoglobulin G Antibodies

Laurence Lecordier,^1, Marie-Pierre Fourmaux,¹ Corinne Mercier,¹ Eric Dehecq,^1, E. Masy,² and Marie-France Cesbron-Delauw^1,*

Mécanismes Moléculaires de la Pathogénèse des Sporozoaires, Institut Pasteur de Lille, IBL, 59019 Lille Cedex,¹ and Service de Biologie Clinique, Département d'Hématologie-Immunologie-Cytogénétique, Centre Hospitalier de Valenciennes, 59322 Valenciennes Cedex,² France

Received 22 November 1999/Returned for modification 29 February 2000/Accepted 5 May 2000

The potential of the dense granule antigens GRA1 and GRA6 of Toxoplasma gondii to be used as diagnosis reagents in a recombinant form was evaluated. Both proteins were expressed in Escherichia coli as glutathione-S-transferase (GST) fusions. The GST-GRA1 fusion comprises the entire GRA1 sequence devoid of its N-terminal signal peptide. Separate expression of the two N- and C-terminal hydrophilic regions of GRA6 showed that only the N-terminal hydrophilic part of the protein was recognized by a pool of positive human sera in an immunoblot. One hundred T. gondii-positive and 98 negative human sera were tested in two separate immunoglobulin G (IgG)-direct enzyme-linked immunosorbent assays (ELISAs) using either GST-GRA1 or GST-GRA6-Nt recombinant protein. Whereas the sensitivity of the GST-GRA1 IgG ELISA was low (68%), the GST-GRA6-Nt IgG ELISA reached a sensitivity of 96%. The reactivity to GRA6-Nt was shown to be high even with human sera of low IgG titers. In addition, comparison of the optical density values for each serum revealed that GRA1 may complement GRA6-Nt to reach an overall sensitivity of 98%. Therefore, the GST-GRA6-Nt ELISA could be used together with another antigen like GRA1 for the development of a recombinant antigen-based test for serodiagnosis of toxoplasmosis.

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^* Corresponding author. Mailing address: Institut Pasteur de Lille, 1, rue du Pr. A. Calmette, 59019 Lille, France. Phone: (33) 3.20.87.11.64. Fax: (33) 3.20.87.11.58. E-mail: marie-france.cesbron{at}ibl.fr.

Present address: Molecular Parasitology, Université Libre de Bruxelles, Rhode Saint Genèse, Belgium.

Present address: Hôpital St Antoine, 59000 Lille, France.

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Clinical and Diagnostic Laboratory Immunology, July 2000, p. 607-611, Vol. 7, No. 4
1071-412X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

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